1. No category

Pekka Kuittinen
Lumbar spinal stenosis
surgical treatment
Correlation of radiological severity to patient’s
symptoms and outcome
Publications of the University of Eastern Finland
Dissertations in Health Sciences
PEKKA KUITTINEN
Lumbar spinal stenosis surgical treatment
Correlation of radiological severity to patient's
symptoms and outcome
To be presented by permission of the Faculty of Health Sciences, University of Eastern Finland for
public examination in Mediteknia Auditorium, University of Eastern Finland , Yliopistonranta 1B,
Kuopio, on September 12th 2015, at 12 noon
Publications of the University of Eastern Finland
Dissertations in Health Sciences
Number 294
Departments of Neurosurgery, Surgery, Clinical Radiology and Physical Medicine and
Rehabilitation, Institute of Clinical Medicine, School of Medicine, Faculty of Health Sciences,
University of Eastern Finland
Kuopio
2015
Grano Oy
Kuopio, 2015
Series Editors:
Professor Veli-Matti Kosma, M.D., Ph.D.
Institute of Clinical Medicine, Pathology
Faculty of Health Sciences
Professor Hannele Turunen, Ph.D.
Department of Nursing Science
Faculty of Health Sciences
Professor Olli Gröhn, Ph.D.
A.I. Virtanen Institute for Molecular Sciences
Faculty of Health Sciences
Professor Kai Kaarniranta, M.D., Ph.D.
Institute of Clinical Medicine, Ophthalmology
Faculty of Health Sciences
Lecturer Veli-Pekka Ranta, Ph.D. (pharmacy)
School of Pharmacy
Faculty of Health Sciences
Distributor:
University of Eastern Finland
Kuopio Campus Library
P.O.Box 1627
FI-70211 Kuopio, Finland
http://www.uef.fi/kirjasto
ISBN: 978-952-61-1842-0 (print)
ISBN: 978-952-61-1843-7 (pdf)
ISSN: 1798-5706 (print)
ISSN: 1798-5714 (pdf)
ISSN-L: 1798-5706
III
Author’s address:
Department of Neurosurgery
Institute of Clinical Medicine
School of Medicine, Faculty of Health Sciences
University of Eastern Finland
KUOPIO
FINLAND
Supervisors:
Ville Leinonen M.D., Ph.D.
Department of Neurosurgery
Institute of Clinical Medicine
School of Medicine, Faculty of Health Sciences
University of Eastern Finland
KUOPIO
FINLAND
Petri Sipola M.D., Ph.D.
Department of Clinical Radiology
Institute of Clinical Medicine
School of Medicine, Faculty of Health Sciences
University of Eastern Finland
KUOPIO
FINLAND
Sakari Savolainen M.D., Ph.D.
Department of Neurosurgery
Institute of Clinical Medicine
School of Medicine, Faculty of Health Sciences
University of Eastern Finland
KUOPIO
FINLAND
Olavi Airaksinen M.D., Ph.D.
Department of Physical and Rehabilitation Medicine
Institute of Clinical Medicine
School of Medicine, Faculty of Health Sciences
University of Eastern Finland
KUOPIO
FINLAND
Reviewers:
Docent Ville Vuorinen M.D., Ph.D.
Department of neurosurgery
University of Turku
TURKU
FINLAND
Docent Marko Neva M.D., Ph.D.
Department of Orthopaedic and Trauma Surgery
University of Tampere
TAMPERE
FINLAND
IV
Opponent:
Docent Eero Kyllönen M.D., Ph.D.
Department of Physical and Rehabilitation Medicine, Institute of Clinical
Sciences
University of Oulu
OULU
FINLAND
V
Kuittinen, Pekka
Lumbar spinal stenosis surgical treatment: Correlation of radiological severity to patient's symptoms and
outcome
University of Eastern Finland, Faculty of Health Sciences
Publications of the University of Eastern Finland. Dissertations in Health Sciences 294. 2015. 79.
ISBN: 978-952-61-1842-0 (print)
ISBN: 978-952-61-1843-7 (pdf)
ISSN: 1798-5706 (print)
ISSN: 1798-5714 (pdf)
ISSN-L: 1798-5706
ABSTRACT
Lumbar spinal stenosis (LSS) is defined as buttock or lower-extremity pain associated
with diminished space available for the neural and vascular elements in the lumbar spine.
LSS may occur with or without low-back pain and other symptoms may include lowerextremity numbness and weakness. LSS is the most common indication for lumbar spinal
surgery in people aged over 65 years. The incidence of LSS is increasing because of the
aging global population, which in turn is associated with an increasing demand for
healthcare. Diagnosis of LSS requires that clinical symptoms be consistent with radiological
imaging findings. The main aim of this study was to assess the correlation of preoperative
MRI findings with clinical symptoms and electromyography (EMG) findings and to
determine whether preoperative MRI findings can be used to predict surgical outcome at
the two-year follow-up. Additionally, we validated a retrospective outcome scale for LSS
surgery, and studied the epidemiology and outcomes of patients treated for LSS in Kuopio
University Hospital from 2003 to 2007.
Preoperative radiological stenosis severity measured using MRI did not correlate with
the preoperative symptoms in patients with central canal LSS. In patients with lateral
stenosis, preoperative electromyography findings correlated with clinical symptoms and
MRI findings. Preoperative lumbar spine MRI predicted the patient outcome in a two-year
follow up. Preoperative findings of visually evaluated severe central stenosis and one-level
stenosis are predictors of good surgical outcomes, whereas findings of scoliosis may
indicate worse functional recovery. Retrospective outcome evaluation was feasible when
compared with prospectively performed assessments. Symptoms were clearly improved in
four out of five LSS patients treated in Kuopio University Hospital.
Our results suggest that preoperative MRI findings of patients with central stenosis do
not have a straightforward correlation with preoperative symptoms, but that the MRI
findings of patients with lateral stenosis may explain the symptoms in some patients.
Preoperative MRI has value in the assessment of surgical outcome before LSS surgery.
National Library of Medicine Classification: Lumbar Spinal Stenosis
Medical Subject Headings: Surgical Outcome, Magnetic resonance imaging, electromyography, Lateral
lumbar spinal stenosis, Surgical Treatment
VI
VII
Kuittinen, Pekka
Lannerangan spinaalistenoosin kirurginen hoito: Radiologisen ahtauman korrelaatio potilaan oireisiin ja
leikkaustulokseen.
Itä-Suomen yliopisto, terveystieteiden tiedekunta, 2015
Publications of the University of Eastern Finland. Dissertations in Health Sciences 294. 2015. 79.
ISBN: 978-952-61-1842-0 (print)
ISBN: 978-952-61-1843-7 (pdf)
ISSN: 1798-5706 (print)
ISSN: 1798-5714 (pdf)
ISSN-L: 1798-5706
TIIVISTELMÄ
Lannerangan spinaalistenoosi (englanniksi lumbar spinal stenosis, jäljempänä LSS)
määritellään seuraavasti: lannerangan selkäydinkanavan tai hermojuurikanavien ahtauma,
jossa hermorakenteet ovat ahtaalla aiheuttaen potilaalle alaraaja - ja/tai selkäoireita sekä
kipua ja toimintakyvyn heikkenemistä. LSS on yleisin syy selkäleikkaukseen yli 65vuotiailla. Väestön ikääntyessä LSS:n esiintyvyys tulee todennäköisesti kasvamaan, joka
aiheuttaa haasteita terveydenhuollolle. LSS-diagnoosi vaatii, että kliiniset oireet ja
radiologiset löydökset sopivat yhteen.
Tämän tutkimuksen tavoitteena oli tutkia, kuinka radiologisen ahtauman aste
mangeettikuvauksessa
(MRI)
ja
neurofysiologisen
(EMG)
tutkimuksen
löydökset
korreloivat potilaan oireisiin ennen leikkausta, sekä pystyykö ennen leikkausta tehty MRI
tutkimus ennustamaan leikkaustulosta kahden vuoden seurannassa LSS-potilailla. Lisäksi
validoitiin
retrospektiivinen
leikkausvasteluokitus
LSS-potilaille
ja
tutkittiin
epidemiologiaa ja leikkaustulosta vuosien 2003 – 2007 välisenä aikana Kuopion
yliopistollisessa sairaalassa leikatuilla LSS-potilailla.
Tämä tutkimus osoitti, että spinaalistenoosin radiologisen ahtauman aste ennen
leikkausta tehdyssä MRI tutkimuksessa ei korreloinut potilaan kliinisten oireiden kanssa,
kun taas lateraalistenoosipotilailla ennen leikkausta havaittu EMG-löydös korreloi potilaan
oireisiin ja radiologiseen löydökseen. Ennen leikkausta tehdyn MRI kuvauksen löydökset
ennustivat kahden vuoden leikkaustulosta lannerangan spinaalistenoosipotilailla. Ennen
leikkausta visuaalisesti arvioitu vaikea sentraalinen stenoosi ja yhden tason stenoosi ovat
hyvän leikkaustuloksen ennustekijöitä, sen sijaan ennen leikkausta todettu skolioosi voi
ennustaa huonoa leikkaustulosta. Tutkimus osoitti myös, että spinaalistenoosileikkauksen
tulos voidaan arvioida varsin luotettavasti retrospektiivisesti sairauskertomustietojen
perusteella.
Neljällä
viidestä
Kuopion
yliopistollisessa
sairaalassa
lannerangan
spinaalistenoosin vuoksi leikatuilla potilailla on hyvä leikkaustulos.
Tutkimuksen tulokset osoittavat, että ennen leikkausta tehdyn MRI tutkimuksen
löydökset eivät korreloi sentraali spinaalistenoosi potilaan oireisiin ennen leikkausta ja että,
lateraalistenoosi voi selittää joidenkin potilaiden oireita.
Ennen leikkausta tehty MRI
tutkimus pystyy ennustamaan leikkaustulosta LSS potilailla.
Luokitus: Yleinen Suomalainen asiasanasto: Lannerangan spinaalistenoosi, leikkaushoito, kirurgia,
magneettikuvaus, neurofysiologinen, leikkausindikaatio
VIII
IX
To Anna-Kaisa
X
XI
Acknowledgements
This study was a part of the “ENNUSSTENOOSI” project and was carried out in the
Departments of Neurosurgery, Surgery, Clinical Radiology, Physical Medicine and
Rehabilitation at the University of Eastern Finland and Kuopio University Hospital in 2008–
2015.
This thesis was financially supported by the University of Eastern Finland, EVO
funding of Kuopio University Hospital, the Finnish Medical Foundation, the Maire
Taponen Foundation, the Medcare foundation, the Research Foundation for Orthopaedics
and Traumatology, the North Savo Regional Fund of the Finnish Cultural Foundation and
the Emil Aaltonen Foundation.
I wish to thank all the co-authors of this “ENNUSSTENOOSI” project: Timo Aalto,
MD, PhD, for setting up and collecting initial patient data. You had great thoughts and
viewpoints regarding my manuscripts, and which contributed to their subsequent
publication. Your help and contribution was especially crucial for my fourth article; Veli
Turunen, MD, for collecting patient data in his clinical work and sharing his great thoughts
about everyday clinical work; Professor Heikki Kröger, MD, PhD, for planning this
research project in the beginning stages, and providing thoughts and guidance with my
manuscripts during the publication process; Sara Määttä, Docent, MD, PhD, and Anita
Parviainen, MD, for analysing the EMG data that had an essential role in my third article;
Sanna Sinikallio Docent, PhD, for valuable comments and thoughts regarding my
manuscripts; and Tapani Saari, MD, for precise analysis of the MRI pictures.
One of my supervisors, Olavi Airaksinen, Docent, MD, PhD, initially planned this
study project and gave guidance and help throughout this project, which I greatly
appreciated. Sakari Savolainen, Docent, MD, PhD, my supervisor, collected excellent
patient data in his clinical work, which I used in my research thesis. Petri Sipola, Docent,
MD, PhD, was an essential supervisor throughout this project; Petri was always ready to
help and to give me guidance with my questions. Petri’s way of thinking about these
scientific problems is both open but still very precise – a great combination for a researcher
and clinical radiologist. Finally, but definitely not least, my main supervisor Ville Leinonen,
Docent, MD, PhD, was my mentor in this scientific research world throughout my research
project. You truly guided me in how to do research and taught me even the most basic
things, like how to use SPSS. I had so many questions and problems during my years of
working on this thesis, but you were always ready to help me. I could not have had a better
supervisor than you, Ville; I am always thankful for your help.
XII
I want to thank Ville Vuorinen, Docent, MD, PhD, University of Turku, and Marko
Neva, Docent, MD, PhD, University of Tampere, for reviewing my thesis. I am thankful to
have Eero Kyllönen, Docent, M.D., Ph.D., from University of Oulu as my opponent.
To my parents, Anne-Riitta and Paavo: thank you for supporting my education. To
my brothers, Panu, Tuomo and Jukka: thank you for just being my brothers.
Finally, I want to express my deepest thanks to Anna-Kaisa for all our years together.
Without your support and love, I would have not done this.
Kuopio, July 2015
Pekka Kuittinen
XIII
List of the original publications
This dissertation is based on the following original publications:
I
Kuittinen P, Aalto TJ, Heikkilä T, Leinonen V, Savolainen S, Sipola P,
Kröger H, Turunen V, Airaksinen O. Accuracy and reproducibility of a
retrospective outcome assessment for lumbar spinal stenosis surgery.
BMC Musculoskelet Disord 29;13:83. 2012.
II
Kuittinen P, Sipola P, Saari T, Aalto TJ, Sinikallio S, Savolainen S,
Kröger H, Turunen V, Leinonen V, Airaksinen O. Visually assessed
severity of lumbar spinal canal stenosis is paradoxically associated with
leg pain and objective walking ability. BMC Musculoskelet Disord.
16;15:348. 2014.
III
Kuittinen P, Sipola P, Aalto TJ, Määttä S, Parviainen A, Saari T,
Sinikallio S, Savolainen S, Turunen V, Kröger H, Airaksinen O,
Leinonen V. Correlation of lateral stenosis in MRI with symptoms,
walking capacity and EMG findings in patients with surgically confirmed
lateral lumbar spinal canal stenosis. BMC Musculoskelet Disord
23;15:247. 2014.
IV
Kuittinen P, Sipola P, Leinonen V, Saari T, Sinikallio S, Savolainen S,
Kröger H, Turunen V, Airaksinen O, Aalto T. Preoperative MRI findings
predict two-year postoperative clinical outcome in lumbar spinal
stenosis. PLoS One 17;9(9): e106404. 2014.
The publications were adapted with the permission of the copyright owners.
XIV
XV
Contents
1 INTRODUCTION ...................................................................... ....
1
2 REVIEW OF THE LITERATURE .............................................. ...
3
2.1
Anatomy of the spine ...............................................................
3
2.2
Pathomorphology and pathophysiology of LSS ..................
4
2.3
Classification of LSS .................................................................
4
2.4
Epidemiology ............................................................................
7
2.5
Diagnosis of LSS .......................................................................
8
2.6
Differential diagnosis in LSS ...................................................
8
2.7
Radiological imaging and grading of LSS ............................
8
2.8
Electrodiagnosis in LSS............................................................
10
2.9
Conservative treatment of LSS ...............................................
10
2.10 Factors predicting surgical outcome in LSS .........................
10
2.10.1 Preoperative MRI predictors ...........................................
11
2.10.2 Preoperative patient symptoms ......................................
11
2.11 Surgical treatment of LSS ........................................................
11
2.11.1 Surgical technique .............................................................
11
2.11.2 Outcome measures in LSS................................................
12
2.11.3 The results of surgical treatment in LSS ........................
14
3 AIMS OF THE STUDY ...................................................................
15
4 ACCURACY AND REPRODUCIBILITY OF A RETROSPECTIVE OUTCOME
ASSESSEMENT OF LUMBAR SPINAL STENOSIS SURGERY
17
4.1
Introduction ...............................................................................
18
4.2
Material and methods ..............................................................
18
4.2.1 Patients................................................................................
19
4.2.2 Retrospective outcome scale measurement ...................
19
4.2.3 Prospective outcome scale measurements ....................
19
4.2.4 Statistical analyses .............................................................
20
4.3
Results ........................................................................................
20
4.4
Discussion ..................................................................................
21
4.5
Conclusions ...............................................................................
22
5 EPIDEMIOLOGY AND RETROSPECTIVE SURGICAL OUTCOME OF KUOPIO
UNIVERSITY HOSPITAL LSS AND DISC HERNIATION SURGERY PATIENTS
DURING THE YEARS 2003-2007. ....................................................
29
5.1
Results ........................................................................................
29
6 VISUALLY ASSESSED SEVERITY OF LUMBAR SPINAL CANAL STENOSIS IS
PARADOXICALLY ASSOCIATED WITH LEG PAIN AND OBJECTIVE WALKING
ABILITY. ...............................................................................................
31
6.1
Background ...............................................................................
32
6.2
Methods .....................................................................................
32
6.2.1 Patients................................................................................
32
6.2.2 MRI ......................................................................................
32
6.2.3 Image analysis ...................................................................
33
6.2.4 Assessment of preoperative symptoms and functional disability
33
6.2.5 Statistical analyses .............................................................
34
XVI
6.3
Results ........................................................................................
34
6.3.1 Clinical characteristics, preoperative symptoms, and functional disability 34
6.3.2 Radiological findings ........................................................
35
6.3.3 Correlation of imaging findings with preoperative symptoms
and functional disability ..................................................
35
6.4
Discussion..................................................................................
35
6.5
Conclusions ...............................................................................
38
7 CORRELATION OF LATERAL STENOSIS IN MRI WITH SYMPTOMS,
WALKING CAPASITY AND EMG FINDINGS IN PATIENTS WITH SURGICALLY
CONFIRMED LATERAL LUMBAR SPINAL CANAL STENOSIS
45
7.1
Introduction ..............................................................................
46
7.2
Material and methods ..............................................................
46
7.2.1 Patients ...............................................................................
46
7.2.2 Magnetic resonance imaging ...........................................
46
7.2.3 Image Analysis ..................................................................
47
7.2.4 Assessment of preoperative symptoms and functional disability
47
7.2.5 EMG ....................................................................................
48
7.2.6 Statistical analyses ............................................................
49
7.3
Results ........................................................................................
49
7.3.1 Correlation of MRI findings with clinical symptoms ..
50
7.3.2 Correlation of clinical symptoms with EMG findings
50
7.3.3 Correlation of MRI and EMG findings ..........................
50
7.4
Discussion..................................................................................
50
7.5
Conclusions ...............................................................................
52
8 PREOPERATIVE MRI FINDINGS PREDICT TWO-YEAR POSTOPERATIVE
CLINICAL OUTCOME IN LUMBAR SPINAL STENOSIS .......
55
8.1
Introduction ..............................................................................
56
8.2
Material and methods ..............................................................
57
8.2.1 Patients ...............................................................................
57
8.2.2 Magnetic resonance imaging ...........................................
57
8.2.3 MRI predictors...................................................................
57
8.2.4 Assessment of postoperative symptoms, functional disability
and satisfaction with surgical outcome ........................
58
8.2.5 Statistical analyses ............................................................
59
8.3
Results ........................................................................................
59
8.3.1 Preoperative clinical characteristics and surgical outcome
59
8.3.2 Radiological findings ........................................................
59
8.3.3 Predictive value of imaging findings for 2-year postoperative outcome 59
8.4
Discussion..................................................................................
60
8.5
Conclusions ...............................................................................
62
9 GENERAL DISCUSSION .............................................................
65
9.1
Role of the retrospective outcome scale ................................
65
9.2
Impact of preoperative MRI in central LSS patients ...........
65
9.3
Impact of preoperative MRI and EMG in lateral spinal stenosis patients
66
9.4
Impact of preoperative MRI for surgical outcome in LSS patients
66
10 CONCLUSIONS .............................................................................
67
11 REFERENCES ...................................................................... ...........
69
XVII
Abbreviations
AP
antero-posterior (diameter)
ODI
Oswestry disability index
BDI
Beck depression index
PRO
patient-reported outcomes
BMI
Body mass index
RCT
randomized controlled trial
CT
Computed tomography
RDQ
Roland-Morris disability
CI
Confidence interval
DSCA
Dural sac cross-sectional area
EMG
Electromyography
EQ-5D
EuroQol 5D quality of life
questionnaire
SF-36
SF-36 health survey
SD
Standard deviation
VAS
Visual analoque pain scale
survey
vs
Versus
kg
Kilogram
15D
15D overall quality of life
LLSCS
Lateral lumbar spinal canal
stenosis
LBP
Low back pain
LSS
Lumbar spinal stenosis
MRI
Magnetic resonance imaging
M
Median
min
Minute
MMC
Minimal clinically importantc
change
mm
Millimeter
mm²
Square millimeter
NSR-11
Numeric rating scale 0-10
N
Number
survey
XVIII
1
1 Introduction
Lumbar spinal stenosis (LSS) is defined as “buttock or lower extremity pain, which may occur
with or without low back pain (LBP), associated with diminished space available for the neural
and vascular elements in the lumbar spine” (1), other symptoms may include lower-extremity
numbness and weakness (3). The diagnosis of LSS is based on clinical symptoms and
radiographic findings (2-4). Electromyography (EMG) tests are used also to supplement
diagnosis of LSS (5).
LSS is the most common indication for lumbar spinal surgery in people aged over 65 years
(6). The aim of surgery is to improve functional ability and relieve symptoms with adequate
decompression of the neural elements. In most of the patients, the long-term results of surgery
are good to excellent, but in one-third of patients, the results are unsatisfactory (7). Accordingly,
preoperative patient selection is considered critical (8-11). The incidence of LSS is increasing,
likely because of a) the better quality and availability of radiological imaging facilities, which
increases detection rates, and b) the aging population (12); therefore, the number of LSS
operations is increasing, selection of patients for surgical treatment still remains challenging.
Previous studies regarding the relationship between radiological severity of LSS and
patient symptoms have had conflicting results. Some studies have found a positive correlation
between patient symptoms and radiological findings (13-14), and some studies have not found
any correlation (15-19). Additionally, radiological stenosis has been found in subjects without
any clinical symptoms (20-22).
EMG test have been used decades for spinal disorders (41). However with the modern
radiological imaging time the role of EMG in LSS diagnose have not been significant (27, 42).
Because correlation between the radiological findings and clinical symptoms has been overally
poor or no correlation at all (15, 44) EMG test has been recommend for LSS diagnosis (15, 22-23).
The primary aim of this study was to investigate how preoperative MRI and EMG
findings correlate with preoperative patient symptoms, postoperative symptoms and patient
satisfaction. We also validated a retrospective outcome scale for LSS, and have presented the
epidemiology of LSS surgery patients treated in Kuopio University Hospital from the beginning
of 2003 until the end of 2007.
2
3
2 Review of the literature
2.1 ANATOMY OF THE SPINE
The vertebral column (or spine) consists of 33 bones called vertebrae. Of these, seven cervical,
12 thoracic and five lumbar vertebrae bones are mobile; five sacral vertebrae form the fused
sacrum; and four vertebrae form the fused coccyx. Between the vertebral bodies are
intervertebral discs, and between the articular processes are two posterior zygapophyseal joints
(facet joints). Inside the intervertebral discs is the nucleus pulposus, and outside is the annulus
fibrosus. The vertebral column forms a spinal canal in which the spinal cord is located and
surrounded by the dural sac. The spinal cord usually ends at the L1–L2 vertebrae level;
thereafter, the lumbar and sacral nerve roots form a prolongation of the spinal cord called the
cauda equina. On the posterior part of the spinal canal is the ligamentum flavum. Thirty-one
pairs of spinal nerves comprise the spinal cord’s dorsal (sensory) and ventral (motor) roots.
From the spinal cord, spinal nerves go to the lateral spinal canal, which consists of subarticular
(entrance) and foraminal (mid) zones. The subarticular zone (lateral recess) is the most cephalad
part of the lateral lumbar canal and is located medial to or underneath the superior articular
process. The foraminal zone is located below the pedicle.
Figure 1. Anatomy of vertebrae. (Wikimedia Commons)
4
2.2 PATHOMORPHOLOGY AND PATHOPHYSIOLOGY OF LSS
The LSS is related to the overall degeneration of the spine. Between the bony vertebrae are the
intervertebral discs with similar constituents to articular cartilage. Disc degeneration can occur
if the balance between synthesis and degradation is abnormal (24). Aging reduces the synthesis
of growth factors, which in turn causes a reduction in the nucleus pulposus water content and
increases stress on discs (24). Twin studies have shown a strong genetic influence on disc
degeneration (25-26). The intervertebral disc is composed of avascular tissue, and blood is
supplied therein through diffusion. One reason for degeneration is a lack of transport of
nutrients and blood into the disc. This leads also to an increase in oxidative stress. Smoking and
nicotine also inhibit cell proliferation and cause disc degeneration (105). Cytokines have been
shown to have a role in disc degeneration process also (93, 94, 95). One randomized controlled
trial (RCT) study showed that antibiotic treatment was more effective than a placebo for
reduction of chronic LBP associated with the Modic type I change, which could suggest that
bacterial infection may have role in disc degeneration also (111).
Disc degeneration has a complex multifactorial aetiology that is mainly an age-related
process influenced by genetic and mechanical factors leading to collapse of the intervertebral
space, disc herniation/bulging, osteoarthrosis of the facet joints, ligament thickening and
osteophyte formation. These factors, together or separately, may cause obstruction of the nerves
in the central or lateral spinal canal. Porter et al. hypothesized that multilevel central stenosis or
one-level central plus foraminal stenosis may cause venous congestions and neurogenic
claudication (27). The current evidence favours venous congestion secondary to mechanical
compression. Some data suggest that multilevel central stenosis may provoke symptoms with
even modest compression because of venous congestion (105).
2.3
CLASSIFICATION OF LSS
LSS is most commonly classified into two categories as either primary stenosis, caused by
congenital stenosis or a disorder of postnatal development, or secondary (acquired) stenosis,
caused by degenerative changes or as a consequence of local infection, trauma, metabolic
disorder (e.g. ,Paget’s disease), surgery, tumour or facet joint cyst. Degenerative LSS is the most
common type of stenosis (28-29).
LSS is defined as “buttock or lower extremity pain, which may occur with or without LBP,
associated with diminished space available for the neural and vascular elements in the lumbar
spine” [1]. Lateral lumbar spinal canal stenosis (LLSCS) is a related condition characterized by
narrowing of the lateral aspects of the central canal (subarticular recess) or foramen through
which the nerve root exits the spinal canal.
Anatomically, LSS can involve the central canal, lateral recesses, foramina or any
combination of these. Central canal stenosis may result from a narrowing of the spinal canal
across the anteroposterior (AP) or transverse diameter combined with loss of disc height.
Central canal stenosis may be accompanied by bulging of the intervertebral disc, hypertrophy
of the facet joints and the ligamentum flavum, or vertebral osteophytosis. Lateral recess and
5
foraminal stenosis may result from same processes as central canal stenosis (30). Foraminal
stenosis may also occur because of spondylolisthesis.
The lateral canal of the lumbar spine can be divided into the entrance zone, the mid-zone
and the exit zone. The subarticular zone (entrance zone) is the most cephalad part of the lateral
lumbar canal and is located medial to or underneath the superior articular process. The
foraminal zone (mid zone) is located below the pedicle, and the exit zone is surrounded by the
intervertebral foramen (31).
Figure 2. Sagittal view, central spinal stenosis.
6
a) normal central spinal canal
b) central spinal canal stenosis
Figure 3. shows the axial T2-weighted model images a) normal central spinal canal; b) central
spinal canal stenosis.
7
2.4
EPIDEMIOLOGY
The Incidence of LSS is increasing because of the aging population (12). Lumbar stenosis is also
detected more frequently these days because of the better quality and availability of radiological
imaging facilities. These factors increase the number of LSS operations. It is estimated from
United States data that every year 90 out of 100.000 persons older than 60 years undergo lumbar
surgery, and LSS is the most frequent indication for this procedure (6). The precise prevalence
of symptomatic lumbar stenosis is still unknown. The prevalence of symptomatic LSS has been
estimated to be around 3 to 10 percent of the population (103, 104). Large variations in surgery
rates for spinal stenosis have been found in different geographical regions (7).
8
2.5
DIAGNOSIS OF LSS
Diagnosis of LSS requires that clinical symptoms and radiological imaging findings match.
Clinical symptoms in LSS can be very diverse. The most common symptom in LSS patients is
neurogenic claudication, defined as buttock or leg pain, fatigue, heaviness, weakness and/or
paraesthesia during walking. Patient symptoms usually increase with lumbar extension and
decrease with flexion. In fact, at rest, patients may even seem asymptomatic (30). Radiographic
evidence (magnetic resonance imaging, computed tomography, myelography) should confirm
compression of the cauda equina or exiting nerve roots resulting from degenerative changes
(ligamentum flavum, facet joints, osteophytes, and/or disc material) that support the clinical
symptoms. The North American Spine Society (NASS) guidelines conclude that imaging is the
key non-invasive test for LSS diagnosis; however, they do not provide radiological criteria for
stenosis (1).
2.6
DIFFERENTIAL DIAGNOSIS IN LSS
To diagnose LSS, it is important to exclude other diseases that can cause similar symptoms.
Most commonly, similar symptoms may occur in vascular claudication. In patients with
vascular claudication, distal pulses are not usually palpable, and the lower legs are cold because
of insufficient blood circulation. Symptoms in vascular claudication are not usually relieved by
lumbar flexion. EMG is helpful for excluding distal nerve entrapment, which may mimic the
radicular symptoms associated with LSS. In myelopathy, the Babinski sign is positive, the lower
limbs are spastic, and reflexes may be clonic. Trochanter and gluteal bursitis can cause pain and
should be taken into account during differential diagnosis. Osteoarthritis in the hip and knee
can also cause radicular-type symptoms, and therefore x-ray of these joints may be necessary.
Neurological diseases and sacroiliitis should also be kept in mind during differential diagnosis
(30).
2.7
RADIOLOGICAL IMAGING AND GRADING OF LSS
NASS guidelines conclude that imaging is the key non-invasive test for LSS diagnosis. A recent
literature review concluded that the most promising imaging test for LSS is MRI (5). However,
there are no well-defined radiological criteria for LSS diagnosis. In the 1980s, Schonstrom
recommended cross-sectional area measurement of the spinal canal for CT imaging, and the
following cut-off values were proposed for LSS diagnosis: absolute stenosis ≤ 75 mm2, relative
stenosis = 75–100 mm2, normal > 100 mm2 (2,89,110); these values were then adopted for MRI
imaging. Several other radiological criteria for LSS diagnosis have been proposed, including the
AP diameter of the central spinal canal (< 10–12 mm), the cross-sectional area of central spinal
canal (<70 mm2), absent fluid around the cauda equina, disc protrusion, lack of perineural
intraforaminal fat, hypertrophic facet joint degeneration and hypertrophy of the ligamentum
flavum. For lateral stenosis, a height (< 2–3 mm) and depth (<3 mm) of the lateral recess have
been defined; for foraminal stenosis, the foraminal diameter (<3 mm) has been recommended
(32-33). However, the challenge with these recommendations is a lack of clear correlation with
clinical symptoms.
9
The relationship of MRI findings to the patient symptoms has also been questioned. Haig
et al. showed that MRI could not differentiate asymptomatic volunteers from symptomatic
spinal stenosis patients (15, 34). In one study, 20% of asymptomatic subjects over 60 years old
had radiological spinal stenosis on MRI (21). A lack of association has been reported between
the Oswestry Disability Index (ODI) and dural sac cross-sectional area (DSCA), qualitative
evaluation of the lateral recess, and foraminal stenosis in a study of 63 LSS patients [16]. Also,
Sigmundsson et al. did not find any correlation between preoperative symptoms and
radiological findings (17). Kanno et al. found that smaller DSCA in axially loaded MRI
correlated with the severity of preoperative symptoms in LSS patients (13). Ogikubo et al.
showed that patients with smaller DSCA in the preoperative MRI had more leg and back pain
preoperatively, had a lower quality of life and reduced walking ability (14). In another study
with 50 patients, patients with a smaller central AP canal reported greater disability, but no
other differences emerged (18). Thus, there is discrepancy within the previous results.
The results of these previous studies relate to routine clinical MRI with patients lying in
the supine position. Imaging patients in the supine position is a limitation, because symptoms
may worsen in the upright position and the upright position may also alter the anatomy of the
neural canal. Accordingly, an upright position would be the most appropriate image acquisition
position for linking image findings to patient symptoms [13, 35]. Hiwatashi et al. found that
axial loading during imaging can even influence treatment decisions [36]. Willen et al. also
pointed out that axially loaded imaging added 29% more information to the imaging results
when compared with imaging in the standard supine position (97). Another study showed that
DSCA decreased 40 mm² at the L3–L4 level in MRI imaging between flexion to extension (106).
One study suggested that lumbar spine extension is the dominant cause for reduction of DSCA
in the standing patient rather than compression (107). Another study pointed out that the
foraminal width, height, and area significantly decreased with the extension of lumbar spine
during the CT imaging (114). Rade et al. showed that the spinal cord displaces distally with the
lumbar nerve roots during clinically applied unilateral and bilateral straight-leg raise tests. A
greater amount of conus medullaris displacement occurred with more hip flexion (113).
Studies that have visually analysed spinal canal stenosis of the whole lumbar spine are
rare. The amount of neural tissue at the L1–L2 and L2–L3 levels is significantly greater than at
the L4–L5 or presacral levels. Thus, by measuring only the DSCA, subjects with reduced space
for neural tissue may not be correctly identified. There is also wide individual variation in the
size of the central canal. Some patients can have a small DSCA without having compression of
neural structures.
Schizas et al. designed a 7-grade qualitative grading system based on the morphologic
appearance of the dural sac, taking into account the cerebrospinal fluid/rootlet content. Their
intra- and interobserver agreement was substantial and moderate, respectively. However, they
did not find any correlation between stenosis grade and baseline ODI (37). Interestingly, using
the same qualitative grading system Mannion et al. found that severity of stenosis measured
using MRI correlated with preoperative pain, change score for pain (between baseline and a 12month follow-up) and the Core Outcome Measures Index change score (38). Another study also
used the same qualitative grading system, and they found strong correlation between the
qualitative and DSCA measurements (39). Guen et al. proposed the same kind of qualitative
four-scale grading as Schizas et al., and their intra- and interobserver agreement was perfect;
however, they did not compare this radiological grading to patient symptoms (109). Sipola et al.
10
evaluated the use of a 3-grade visual classification for the assessment of lateral stenosis, and
demonstrated that this method has acceptable repeatability for research purposes (40).
2.8
ELECTRODIAGNOSIS IN LSS
EMG and nerve conduction studies were used over sixty years ago to diagnose spinal disorders
(41). However, modern medicine has ignored the role of EMG in LSS diagnosis (27, 42) until
recent decades (15). NASS guidelines conclude that imaging is the key non-invasive test for
LSS diagnosis and do not support the use of EMG (1).
Because the correlation between radiological findings and clinical symptoms has been
generally poor or non-existent (15, 44), EMG testing has been recommended for LSS diagnosis.
Haig et al. found that MRI imaging did not differentiate symptomatic from asymptomatic
persons, whereas paraspinal EMG could make this distinction (15). Yagci et al. pointed out that
paraspinal mapping EMG was abnormal in 93% of patients who had clinical and radiological
LSS, whereas paraspinal mapping EMG was normal in 94% of patients who had radiological
stenosis but no symptoms at all (23). In turn, Chiodo et al. pointed out that motor unit changes
on EMG needle examination and low paraspinal mapping scores are also common in
asymptomatic older adults with radiological spinal stenosis. This finding indicates weak
specificity; however, the risk of abnormal spontaneous activity on needle examination and
paraspinal mapping scores greater than 6 was considered lower than the risk of false positive
findings during EMG testing (22). However, studies by Haig et al. and Yagci et al. showed high
specificity in paraspinal mapping EMG testing (15, 23). In a recent literature review, although
MRI was recommended for LSS diagnosis, it was suggested that paraspinal mapping EMG may
be useful in confirming LSS diagnosis among patients with atypical symptoms (5). Further
study is needed to clarify the role of EMG in the diagnostics of LSS.
2.9
CONSERVATIVE TREATMENT OF LSS
Conservative treatment is recommended for several months in LSS. This conservative approach
favours mild symptoms, when daily function is sufficient and the patient can walk at least few
hundred meters. Conservative treatment includes analgesics, which can be paracetamol, antiinflammatories or opioids if necessary (44-45). Tricyclic antidepressants have been used also to
treat chronic pain (44). Some benefits of exercise and active physiotherapy in LSS have also been
found (46). A sport trial study showed that, in most patients treated conservatively, disability
did not worsen over the course of a four-year follow-up (74). Another study in turn showed that
pain increased in only 15 % of the LSS patients during a five-year period of conservative
treatment (108).
2.10 FACTORS PREDICTING SURGICAL OUTCOME IN LSS
LSS diagnosis is made from clinical symptoms and radiological findings (1, 5). However, the
long-term results of surgery are poor in one-third of patients (6, 7). Accordingly, preoperative
11
patient selection is considered critical. The preoperative predictors for surgical outcome are
important for optimal patient selection.
2.10.1
Preoperative MRI predictors
Previous studies have pointed out that greater preoperative scoliosis based on standard X-ray
images predicted more postoperative back pain with a two-year follow-up time (47). Yukawa et
al. observed less postoperative disability, as measured with the ODI, in patients who had a
DSCA under 70 mm2 on the preoperative MRI (48). Sigmundsson et al. investigated the
predictive value of MRI findings among 109 LSS patients undergoing surgery with a one-year
follow-up. That prospective study showed that a smaller DSCA indicated less leg pain
postoperatively and reduced LBP (49). Amundsen et al. did not find any association between
preoperative radiological MRI findings and postoperative outcomes (43).
2.10.2
Preoperative patient symptoms
According to a systematic literature review on LSS surgery patients, depression, cardiovascular
comorbidity, disorder influencing walking ability, and scoliosis predicted poorer subjective
outcomes. Better walking ability, self-rated health, higher income, less overall comorbidity, and
pronounced central stenosis predicted better subjective outcomes. Male gender and younger
age predicted better postoperative walking ability (50). Another review also confirmed that
preoperative depression is a prognostic factor for postoperative symptom severity and
disability in LSS patients (51). Smoking, psychiatric illness, high body mass index (BMI), a long
duration of symptoms and preoperative resting numbness have also been identified as
predictors of poorer surgical outcomes (52-56). Wahlman et al. found that the prevalence of
depressive symptoms decreased after spinal fusion surgery (115). Our current data on LSS
patients, collected in Kuopio University Hospital, have also indicated that regular use of
analgesics preoperatively for 12 months or less, self-rated health above average and nonsmoking predicted a good postoperative functional improvement. An age under 75 years and
no previous lumbar operation predicted good postoperative satisfaction with the surgery (8).
Sigmundsson et al. found that patients who had a preoperative duration of leg pain of less than
2 years, no analgesics consumption and good preoperative function demonstrated better
postoperative outcomes (49).
2.11 SURGICAL TREATMENT OF LSS
Surgical treatment should be considered if patients have neurological symptoms, severe pain
persisting in spite of conservative treatment, a walking distance of less than 200–300 m or a
progressive defect.
2.11.1
Surgical technique
The most common surgical technique for LSS is decompressive (bilateral) laminotomy, in which
the medial part of the facet joint, osteophytes, the hypertrophic ligamentum flavum and
potential disk herniation compressing the central and/or lateral spinal canal are resected.
12
Decompressive laminectomy can also be done, in which the posterior part of the vertebral arch
is totally resected. If necessary, vertebral levels can be fused with a bone graft – with or without
instrumentation – to prevent progression of the spondylolisthesis. In spinal stenosis with
degenerative olisthesis, fusion has been found to be superior to conservative treatment or
decompression alone (58-61). In turn, a Swedish spine registry study did not find any
differences in outcome between decompression/fusion treatment and decompression only
surgical treatment groups in LSS patients with degenerative olisthesis at the two-year follow-up
(112).
2.11.2
Outcome measures in LSS
The outcome of treatment is measured nowadays using patient-reported outcomes (PRO) and
quality of life scales such as the ODI (62,63) and the Roland-Morris Disability Questionnaire
(RDQ) (64), the Visual analogue pain scale (VAS) (65), work disability time (66,67) and quality
of life questionnaires such as the SF-36 (68), EQ-5D (69) and 15D (70). Comorbidity measures
such as the Beck Depression Index (BDI) (71) and the Fear-Avoidance Belief Questionnaire
(FABQ) (72) are also used. Table 1 shows the different outcome measures that can be used in
LSS surgery to measure surgical treatment outcomes. The minimal clinically important change
(MMC) is the minimal change of the score between the postoperative and preoperative
measurement that is clinically relevant (Table 1).
13
Table 1. Different outcome predictor scales and their minimal important changes.
Scale
MMC
Reference.
ODI
0-100 %
10
62, 63
RDQ
0-24
5
64
VAS
0-100
15
65
SF-36
0-100
EQ-5D
-0.059 – 1.00
15D
0 -1
68
0.08
69
70
MMC = minimal clinically important change, ODI = Oswestry disability index, RDQ = Roland –
Morris disability questionnaire, VAS = Visual analogue pain scale , SF-36 = SF-36 health survey,
EQ-5D = EuroQol 5D quality of life survey, 15D = 15D overall quality of life survey
14
2.11.3
The results of surgical treatment in LSS
Good-to-excellent surgical results for LSS have been reported for an average 64% of cases (73).
In the first RCT that compared surgery with conservative treatment in LSS patients, surgery
was more influential on pain and function at the two-year follow-up; however, no differences
were found between walking capabilities (58). The same study showed that there was a
statistically significant difference in disability (using the ODI scale) in favour of surgical
treatment at the six-year follow-up; however, differences in pain were no longer noticeable
(102). Another randomized trial and concurrent observational cohort study also showed that
surgical treatment was superior to conservative treatment at the two-year follow-up (61). The
same study group has published four- and eight-year results, and these results confirm that
surgical treatment is more effective compared with conservative treatment (74, 75). A previous
report from Kuopio University Hospital showed that patient assessment and satisfaction with
surgery outcome was good or excellent in 68% of patients at the ten-year follow-up (76). Few
studies have investigated surgical treatment of lateral spinal stenosis. A single study pointed
out that surgical outcomes for lateral spinal stenosis were worse than for central spinal stenosis
or disk herniation at the one-year follow-up; however, differences were diminished after a
follow-up period of eleven years (77). Spinal fusion surgery has been shown to be effective three
months postoperatively, and the good results sustained at the two-year follow-up (116).
15
3 Aims of the study
The general aim of this study was to evaluate the correlation of preoperative MRI and EMG
findings with preoperative patient symptoms and postoperative surgical outcomes.
Additionally, we validated a retrospective outcome scale for LSS surgery.
The specific aims of the study were as follows (Roman numerals refer to original publications):
1.
To validate a retrospective outcome scale for LSS (I).
2.
To compare preoperative, visually and quantitatively evaluated radiological central
lumbar spinal canal stenosis with preoperative patient symptoms and clinical
findings in patients with LSS (II).
3.
To evaluate the clinical significance of lateral lumbar spinal canal stenosis patients,
found by MRI, through correlating the imaging findings with patient symptoms,
walking capacity and EMG measurements (III).
4.
To study the value of preoperative MRI findings in central lumbar stenosis patients
for predicting two-year postoperative clinical outcomes in LSS (IV).
16
17
4
Accuracy and reproducibility of a retrospective
outcome assessement of lumbar spinal stenosis surgery
Abstract
Purpose: Retrospective assessment of surgery outcome is considered problematic. The aims of
this study were to evaluate the reproducibility and accuracy of a retrospective outcome
assessment of lumbar spinal stenosis surgery with reference to prospective outcome scale
measurements.
Method: Outcome of surgery from 100 lumbar spinal stenosis (LSS) patients was evaluated
retrospectively from patient files of a 3-month outpatient visit performed according to a
standard clinical protocol by two independent researchers. In the retrospective analysis,
outcome was graded as 2=good if the clinical condition had clearly improved, 1=moderate if it
had just slightly improved, 0=poor if it had not improved or was even worse than before the
surgical treatment (Retrospective 3-point scale). A prospectively assessed Oswestry Disability
Index questionnaire (ODI), Visual analogue pain scale (VAS) and a patient satisfaction
questionnaire were used as references of standards. Reproducibility of the measurements were
evaluated.
Results: The retrospective 3-point scale correlated with ODI (r = 0.528; P < 0.001) and VAS (r =
0.368; P < 0.001). The agreement was better in the good and poor outcome than in the moderate
outcome. Retrospective 3-point scale demonstrated substantial intra-rater and inter-rater
repeatability.
Conclusions: Retrospective assessment of spinal surgery outcome is highly reproducible.
Accuracy is highest in the patients with poor and good surgical result.
18
4.1
INTRODUCTION
Lumbar spinal stenosis (LSS) is the most common indication for lumbar spinal surgery in
people aged over 65 years (6). The long-term results of surgery are poor in one third of patients
(6, 7) emphasizing the need for investigation of the predictive factors of surgical outcome (7, 78)
and patient selection for surgery (79). Prospective studies are the best way to perform research.
In prospective studies, however, patient selection may differ from the patient selection in daily
clinical routine. In addition, comparison of treatment with historical controls is not feasible.
Retrospective studies can include large patient materials. However, assessment of outcome in
retrospective analysis is questionable. To the best of our knowledge, however, no previous
study has investigated the accuracy and reproducibility of retrospective outcome
measurements. Accordingly, the aims of this study were to evaluate the reproducibility and
accuracy of a retrospective outcome assessment for lumbar spinal stenosis surgery with
reference to prospective outcome scale measurements. As a model cohort we used a well
characterized patient cohort which has undergone surgery for lumbar spinal spinal stenosis in a
prospective study design.
4.2
MATERIAL AND METHODS
This prospective single-center study was approved by the Ethics Committee of Kuopio
University Hospital, and the patients provided informed consent. The study included 102
patients with both clinically and radiologically defined LSS who had been selected for surgical
treatment. Eighteen patients had only lateral spinal stenosis. Selection for surgery was made by
an orthopedist or neurosurgeon at the Kuopio University Hospital, Kuopio, Finland.
The inclusion criteria were as follows: 1) the presence of severe back, buttock, lower
extremity pain, and/or neurogenic claudication with radiographic evidence (computed
tomography, magnetic resonance imaging (MRI), myelography) of compression of the cauda
equina or exiting nerve roots by degenerative changes (ligamentum flavum, facet joints,
osteophytes, and/or disc material); and 2) clinical and radiological evaluation by a surgeon,
indicating that the patient had degenerative LSS with symptoms that could be relieved by
operative treatment. Additionally, all patients had a history of ineffective response to
conservative treatment over three months. Patients with only back pain were not included.
The exclusion criteria were as follows: emergency or urgent spinal surgery precluding
recruitment and protocol investigations; cognitive impairment prohibiting completion of the
questionnaires or other failures in cooperation, and the presence of metallic particles in the
body preventing the magnetic resonance imaging investigation. The surgeons sent the
information of eligible patients to the Department of Physical and Rehabilitation Medicine, for
19
further study organization. A previous spine operation or co-existing disc herniation (N=13)
were not exclusion criteria. Sixteen patients (out of 102 study patients) had previously
undergone one or more lumbar spine operations.
All the 102 patients had open or microscopic decompressive surgery with (N=19) or
without (N=83) arthrodesis or with extirpation of disc herniation (N=7). Decompressive surgery
included laminotomy, hemilaminectomy or laminectomy with undercutting facetectomy.
Decompression was done at 1 level in 23 patients, 2 levels in 51 patients, 3 levels in 24 patients
and 4 levels in 2 patients. The most common level for decompression was L4-L5. Of the 19 cases
with concomitant degenerative spondylolistesis leading to posterolateral fusion, three reached
two levels, and the remaining 16 cases were single level.
4.2.1 Patients.
In this publication (I) two of the 102 baseline patients had missing BDI and ODI data at the 3month follow-up time, thus the final patients sample size was 100.
4.2.2Retrospective outcome scale measurement
In the retrospective analysis, surgical outcome was evaluated from the medical records by two
independent researchers blinded for the prospective questionnaire data. Patient outcome was
graded as 2=good if the clinical condition had clearly improved which was the case when the
patient was satisfied to the surgical treatment and symptoms free, 1=moderate if it had only
slightly improved symptoms and the patient was not totally satisfied to the surgical treatment,
0=poor if it had not improved symptoms or was worse than before the surgical treatment which
was the case if the patient was totally dissatisfied to the surgical treatment (Retrospective 3point scale). The judgement was based on the information in the medical records during the
postoperative 3-month clinical check-up when the surgeon met the patient and patient told for
the surgeon about how he or she was doing and how satisfied patient was to surgical treatment.
To assess the inter-rater repeatability of the retrospective scale, the evaluation of the patient files
was repeated completely for all patients (N = 100) by an independent senior neurosurgeon
blinded for the previous evaluation. To assess the intra-rater repeatability, the retrospective
evaluation of the patient files was repeated completely (N = 100) of at least 2 months after the
first evaluation by the first independent researcher, who was again blinded for previous results
and prospective questionnaire data.
4.2.3 Prospective outcome scale measurements
Overall back and leg pain intensity was assessed by a self-administered Visual analogue scale
(VAS) (range 0-100 mm). This has been proved to be a valid index of experimental, clinical and
chronic pain (82). Subjective disability was measured by the validated Finnish version of the
Oswestry Disability Index, where 0% represents no disability and 100% extreme debilitating
disability (62, 83). Depression was assessed with the Finnish version of the 21-item BDI with
20
scores ranging from 0 to 63 (71, 84). Patients completed the ODI, VAS and BDI questionnaires at
the baseline and 3 month after operation.
4.2.4 Statistical analyses
Associations between the retrospective 3-point surgical outcome scale and the prospectively
measured ODI, VAS and BDI were analysed using Spearman correlation coefficients. Final
value of ODI, VAS and BDI were used for prospective data. We analysed separately analysis for
patients with the only isolated lateral spinal stenosis to study possible difference outcomes in
the central and lateral spinal stenosis patients. The inter-rater and intra-rater repeatability of the
retrospective scale was analysed by calculating kappa coefficients (κ). Statistical significance
was set at the P < 0.05 level.
4.3 RESULTS
The mean age of the study patients at the time of surgery was 62 years (range 34-86), and
57 (57%) were male. The mean 3-month ODI was 26.9 (SD = 18.6), the mean 3-month VAS was
19.1 (SD = 22.1), and the mean 3-month BDI was 8.0 (SD = 5.8). Other background and baseline
clinical characteristics of all the surgically treated lumbar spinal stenosis patients are in Table 2.
According to the 3-point retrospective outcome scale, 73 (73 %) patients had good, 14 (14
%) moderate and 13 (13 %) poor outcome. 3-point retrospective outcome scale correlated with
The mean 3-month ODI (Spearman r = 0.528; P < 0.001) (Table 3) (Figure 4). Spearman
correlation coefficient was somewhat higher in patients with lateral canal stenosis only (r =
0.621, P = 0.008, N=17) than in patients with central canal stenosis (r = 0.520, P = 0.001, N=83).
3-point retrospective outcome scale correlated with the mean 3-month VAS (Spearman r =
0.368, P < 0.001) (Table 3). Spearman correlation coefficient was higher in patients with lateral
canal stenosis only (r = 0.592, P = 0.012, N=17) than in patients with central canal stenosis (r =
0.335, P = 0.002, N=83).
3-point retrospective outcome scale correlated with the mean 3-month BDI (Spearman r =
0.300, P < 0.005) (Table 3). Spearman correlation coefficient was again higher in patients with
lateral canal stenosis only (r = 0.655, P = 0.004, N=17) than in patients with central canal stenosis
(r = 0.229, P = 0.038, N=83).
3-point retrospective outcome scale correlated with the baseline ODI (r = 0.229, p = 0.022)
(Figure 5), VAS (r = 0.197, p = 0.049), BDI (r = 0.292, p = 0.004) and with the change between the
baseline and 3-month follow-up ODI (r = 0.482, p = 0.000) (Figure 6) but not change in VAS (r =
0.165, p = 0.102) and BDI (r = 0.051, p = 0.621).
21
We compared also patients with the only spinal stenosis, spinal stenosis with the
instability, spinal stenosis and we didn’t find any difference in the pre op, post op or change of
ODI, VAS and BDI scores between these groups.
Both the intra and inter-rater repeatability of the retrospective 3-point surgical outcome
scale was substantial (κ = 0.682, P < 0.001 and κ=0.630, P < 0.001, respectively). Overall
agreement was 83% (N = 68) and there was only one case with total disagreement in the surgical
result between the researchers.
4.4
DISCUSSION
Selection of patients for surgical treatment of LSS still remains challenging as well as the
evaluation of the efficacy of the treatment. The definition of the outcome by different outcome
measures of surgical and non-surgical treatment requires clarification. To the best of our
knowledge, there are no previous studies validating the retrospective evaluation of surgical
outcome for lumbar spinal stenosis. Such a measure is important when studying large cohorts
of patients and comparing prospective registries with previous clinical results.
In prospective studies, the outcome of treatment can be with standard questionnaires such
as the Oswestry Disability Index (ODI) (62) and the Roland-Morris Disability Questionnaire
(RDQ) (64), the Visual analogue pain scale (VAS) (85), the work disability time (66,67) and
quality of life questionnaires such as SF-36 (68), EQ-5D (69) and 15D (70) . Comorbidity
measures such as the Beck Depression Index (BDI) (71) and the Fear-Avoidance Belief
Questionnaire (FABQ) (72) are also used.
Our results show that the outcome of surgery can be evaluated also retrospectively.
Accuracy is highest in patients with poor and good surgical result. Both the intra- and also the
inter-rater reproducibility of retrospective assessments are acceptable. The moderate outcome is
the most challenging to determine and its retrospective evaluation could be questioned (Figure
4.1).
This study showed that patients who had at the baseline worse scores in the ODI, VAS,
BDI had also worse surgical outcome according the retrospective 3-point scale. The bigger ODI
change between the baseline and 3-month follow-up also correlated to good outcome (Figure
4.3). This data could be used in clinical work to predict possible surgical outcome.
The higher correlation of the 3-point outcome scale with the ODI than with the VAS and
BDI is logical. The VAS measured overall back pain, which is, in contrast to neurogenic
claudication, usually not the worst symptom relieved by surgery in LSS patients. With regard to
the BDI, improvement in disability and pain are the most important aspects of good outcome
(79), and depression is only a comorbid condition, although, a potential predictor of outcome.
Interestingly, correlations with the VAS and BDI were almost two times higher in patients
with only lateral stenosis compared with central stenosis patients. One explanation for this
22
could be that severe lateral spinal stenosis causing nerve compression is the major cause of pain
and disability, and patients may have fever other symptomatic structural changes in their spine.
One limitation of this study is the relatively small number of patients with lateral spinal
stenosis.
4.5
CONCLUSIONS
Retrospective assessment of spinal surgery outcome is highly reproducible. Accuracy is highest
in the patients with poor and good surgical result.
23
Table 2. Background and clinical characteristics of the lumbar spinal stenosis patients
preoperatively and on 3-month postoperative follow-up time n=100.
Preoperative phase
Age (years at operation,mean (SD))
62.0 (12.0)
Male/Female (n)
57/41
BMI (kg/m²) (SD)
29.4 (4.0)
Marital status (%)
64.4
3-months follow-up
In relationship (married or co-habiting)
Employment status (%), at work
13.9
Current smoker (%)
20.6
Number of somatic diseases (mean (SD))
5.4 (3.2)
Type of stenosis central/lateral
83/17
Dural sac area (mean; mm²) the most stenotic level
57.8 (32.5)
Previous lumbar operation (n)
16
Time since first back pain episode, years (mean (SD))
15.8 (13.9)
Oswestry (ODI) % (mean (SD))
43.9 (15.4)
26.9 (18.6)
VAS, mm (mean (SD))
33.3 (23.9)
19.1 (22.1)
BDI score (mean (SD))
10.3 (6.0)
8.0 (5.8)
Walking capacity, m (mean (SD))
594 (439)
ODI = Oswestry disability index scale (0-100)
VAS = overall Visual analogue pain scale (0-100)
BDI = Beck Depression index (0-63)
24
Table 3. Correlation of retrospective 3-point surgical outcome and prospective follow-up
measures, N (100).
3-month follow-up
ODI
r=0.528, P=0.000
BDI
r=0.300, P=0.002
VAS
r=0.368, P=0.000
P = P values
r = Spearman correlation coefficients
ODI = Oswestry disability index
BDI = Beck depression index
VAS = Visual analogue pain scale
25
Figure 4. Correlation of retrospective 3-point surgical outcome and 3 month follow-up
prospective Oswestry disability index.
26
Figure 5. Correlation of retrospective 3-point surgical outcome and baseline prospective
Oswestry disability index
27
Figure 6. Correlation of retrospective 3-point surgical outcome and change between the baseline
and 3-month follow up time prospective Oswestry disability index
28
29
5 Epidemiology and retrospective surgical outcome of Kuopio
University Hospital LSS and disk herniation surgery
patients during the years 2003-2007.
For this thesis, we retrospectively analysed the epidemiology of Kuopio University Hospital
LSS decompression and disk herniation surgery patients using background data, and evaluated
a retrospective outcome scale for these patients according to previously validated retrospective
outcome scales (I). The study included patients (N = 2310) who underwent operations for LSS
decompression and disk herniation surgery between 1.1.2003–31.12.2007 in the departments of
neurosurgery and orthopaedics.
5.1
RESULTS
Altogether, the study included 2310 patients (1091 LSS decompression surgery patients and
1219 disk herniation surgery patients). Patient background and clinical data are presented in
Table 4. This study confirmed previously published results that there is no statistically
significant difference in outcome with respect to LSS and herniated disc surgery outcomes (77).
Previous studies have showed that the long-term results of surgery are good-to-excellent in
two-thirds of patients (6,7). Our results also showed that LSS and disk herniation surgery
patients demonstrated good surgical outcomes in 79% of cases according to our retrospective
outcome scale. The disk herniation patients were younger and they had more re-operations
after the first operation within a one-year period than the LSS decompressive surgery patients.
In turn, LSS patients had higher BMI (p = 0.002) and American Society of Anesthesiologists scale
points (p < 0.001 ) than disk herniation patients, which may be associated with greater age and
more comorbidities in the LSS group. Interestingly, 8.1 % of the LSS patients had preoperatively
used antidepressant medication compared with 4.6% of disk herniation patients (p < 0.001). This
result may indicate that more LSS patients experience depression than disk herniation patients,
or that antidepressant medication is used more frequently as a treatment for pain in LSS
patients. These data did not include patients’ symptom duration, which can also explain higher
antidepressant medication in LSS patients because usually disk herniation surgery patients
undergo operation more rapidly than LSS patients.
62.8 (11.7)
519/572 (47.6/52.4 %)
28.5 (10.3)
2.3 (0.7)
88 (8.1 %)
199 (18.2 %)
84 (7.7 %)
Age (years at operation, mean (SD))
Male/Female n (%)
BMI (kg/m²) (SD)
ASA scale (SD)
Anti-depressant medicine in use
Previous lumbar operation (%)
Reoperation surgical operation in one year (%)
96 (12.2 %)
67 (8.5 %)
Moderate outcome
Poor outcome
ASA scale = American Society of Anesthesiologists (ASA) physical status
622 (79.2 %)
Good outcome
Retrospective 3-point surgical outcome
1091
Decompression of LSS
Number of the patients n
Hospital.
102 (11.0 %)
92 (9.9 %)
734 (79.1 %)
157 (12.9 %)
243 (19.9 %)
56 (4.6 %)
1.5 (0.7)
27.0 (11.5)
709/510 (58.2/41.8 %)
44.8 (12.8)
1219
Excision of disc herniation of the lumbar spine
0.096
0.096
0.096
0.000
0.224
0.000
0.000
0.002
0.000
0.000
P-value
Table 4. Patients’ background data were operated for LSS and disc herniation between 1.1.2003 – 31.12.2007 time period in Kuopion University
30
31
6 Visually assessed severity of lumbar spinal canal
stenosis is paradoxically associated with leg pain and
objective walking ability
Abstract
Background: Lumbar spinal stenosis (LSS) is the common term used to describe patients with
symptoms related to the anatomical reduction of the lumbar spinal canal size. However, some
subjects may have a markedly narrowed canal without any symptoms. This raises the question
of what is the actual role of central canal stenosis in symptomatic patients. The purpose of this
study was to compare radiological evaluations of LSS, both visually and quantitatively, with the
clinical findings of patients with LSS.
Methods: Eighty central LSS patients [mean age 63 (11) years, 44% male], with symptoms
severe enough to indicate LSS surgery, were included in this prospective single-center study.
Lumbar magnetic resonance imaging was performed and one experienced neuroradiologist
classified patients into three groups: 0 = normal or mild stenosis, 1 = moderate stenosis, and 2 =
severe stenosis. In addition, the same observer measured the minimal dural sac area level by
level from the inferior aspect of L1 to the inferior aspect of S1. The association between
radiological and clinical findings were tested with Oswestry Disability Index, overall visual
analog pain scale, specific low back pain, specific leg pain, Beck Depression Inventory, and
walking distance on treadmill exercise test.
Results: In the visual classification of the central spinal canal, leg pain was significantly higher
and walking distance achieved was shorter among patients with moderate central stenosis than
in patients with severe central stenosis (7.33 (2.29) vs 5.80 (2.72); P = 0.008 and 421 (431) m vs 646
(436) m; P = 0.021, respectively). Patients with severe stenosis at only one level also achieved
shorter walking distance than patients with severe stenosis of at least two levels. No correlation
between visually or quantitatively assessed stenosis and other clinical findings was found.
Conclusions: There is no straightforward association between the stenosis of dural sac and
patient symptoms or functional capacity. These findings indicated that dural sac stenosis is not
the single key element in the pathophysiology of LSS.
Keywords: Spinal stenosis; Magnetic resonance imaging; MRI; Low back pain; Leg pain;
disability; Walking distance
32
6.1
BACKGROUND
Lumbar spinal stenosis (LSS) is the term used commonly to describe patients with symptoms
related to the anatomical reduction of the size of the lumbar spinal canal [86]. However, some
subjects can have a narrowed canal without presenting any symptoms. Therefore, this
peculiarity raised the question of what is the actually role of central canal stenosis in
symptomatic patients. The relationship between radiological findings and patient’s symptoms
has been studied by several authors. These studies have reported that MRI imaging findings
did not identify symptomatic from asymptomatic persons [15, 18, 19, 16].
Unfortunately, many previous studies have some methodological limitations related to the
assessment of patients’ symptoms. Typically, the symptoms have been evaluated
retrospectively from the patient records or otherwise rated without a standard methodology.
The use of the standardized Oswestry Disability Index (ODI) [62], overall Visual analog pain
scale (VAS) [85], Beck Depression Inventory (BDI) [71], and specific back pain at rest and leg
pain at walking items of the Numerical Rating Scale (LBP- and LP-NRS-11) [87] have improved
the accuracy and reproducibility of patients symptom and functional disability grading.
The purpose of this study was to investigate the role of anatomical changes on patient
symptoms and functional disability. We compared the radiological findings to the symptoms
and function of patients with LSS measured with standardized methods in a prospective study
setting.
6.2
6.2.1
METHODS
Patients
In this publication (II) we selected central spinal stenosis patients (n = 84) of the 102 baseline
patients. Only distinct lateral spinal canal stenosis patients were excluded. Four patients
baseline data was missing, thus the final patients sample size was 80. See above 4.2.
6.2.2
MRI
MRI of the lumbar spine was performed with a 1.5-T imager (Vision; Siemens Medical
Solutions, Erlangen, Germany) and a dedicated receive-only spine coil. All patients were
evaluated prospectively by applying the same study protocol for study purposes. The imaging
protocol conformed to the requirements of the American College of Radiology for the
33
performance of MRI of the adult spine [88]. The following sequences were used: (a) sagittal T1weighted spin-echo (repetition time/echo time (TR/TE) 600/12 ms; flip angle, 150°; 4-mm
sections; intersection gap, 0.4 mm; field of view (FOV), 290 mm; rectangular FOV, 80%; three
signals acquired per data line; matrix 288 × 512) (b) sagittal T2-weighted fast spin-echo
(3500/120; flip angle, 180°; echo train length of five; 4-mm sections; intersection gap, 0.4 mm;
FOV 290 mm; rectangular FOV, 63%; two signals acquired; matrix 180 × 512); (c) transverse T1weighted spin-echo (700/15; flip angle, 90°; 4-mm sections; intersection gap, 0.4 mm; FOV, 250
mm; rectangular FOV, 80%; two signals acquired per data line; matrix 288 × 512); and (d)
transverse T2-weighted fast spin-echo (5000/120; flip angle, 180°; echo train length of 15; 4-mm
sections; intersection gap, 0.4 mm; FOV, 250 mm; rectangular FOV, 100%; three signals acquired
per data line; matrix 330 × 512).
The entire lumbar spine was studied on the sagittal images (T12-S1), including parasagittal
imaging of all the neural foramina bilaterally. Transverse images (axial) were obtained from the
inferior aspect of L1 to the inferior aspect of S1, and the orientation of the sections was planned
parallel to the major axis of each disc. In all sequences, a saturation band was placed over the
abdominal vessels.
6.2.3
Image analysis
Image evaluation was performed with Numaris software (Siemens Medical Systems) by a
neuroradiologist with 15 years of experience with spinal MRI (T.S.). Image analysis was
performed independently without knowledge of the patient clinical symptoms and data. Each
level from the inferior aspect of L1 to the inferior aspect of S1 was analyzed separately. For the
visual image evaluation, the central canal was visually classified into three grades: 0 = normal or
mild changes (ligamentum flavum hypertrophy and/or osteophytes and/or or disk bulging
without narrowing of the central spinal canal), 1 = moderate stenosis (central spinal canal is
narrowed but spinal fluid is still clearly visible between the nerve roots in the dural sac), 2 =
severe stenosis (central spinal canal is narrowed and there is only a faint amount of spinal fluid
or no fluid between the nerve roots in the dural sac) (Fig 7). Patients who had severe stenosis at
least two levels in the visual analysis were classified as having the multilevel spinal stenosis.
For the quantitative image evaluation, each level was first assessed visually. The borders of the
dural sac were manually traced in the image with smallest cross-sectional area upon visual
examination. According to the smallest area, patients were divided into three groups: 1)
patients with dural sac area less than 75 mm²; 2) patients with dural sac area form 75–100 mm²;
and 3) patients with dural sac area greater than 100 mm² [89]. In statistical analyses, the highest
degree of stenosis was used for both the visually and quantitatively measured stenoses.
6.2.4
Assessment of preoperative symptoms and functional disability
The overall current low back and leg pain intensity was assessed by a self-administered VAS
(range 0–100 mm) in a sitting position during study visits. VAS was proven as a valid index for
34
experimental and clinical assessments of chronic pain [65]. According to the score range (0–100
range), four groups were established: scores 0–20 (minimal), 21–40 (moderate), 41–60 (severe),
and over 60 (crippled). Back pain at rest (during last week) and leg pain while walking (during
last week) were measured separately with a numeric rating scale ranging from 0 to 10 (NRS-11)
[87]. The questions about pain were anchored on the left (0) with the phrase “No pain” and on
the right (10) with the phrase “intolerable pain”.
Subjective disability was measured by the validated Finnish version of the ODI, where 0%
represents no disability and 100% extreme debilitating disability. This ODI score (0–100 range)
were also classified in four groups: scores 0–20 (minimal), 21–40 (moderate), 41–60 (severe), and
over 60 (crippled) [62-63, 83].
Depression was assessed with the Finnish version of the 21-item BDI with scores ranging
from 0–63 [71, 84]. The cutoff point for depression was set at 15/63. The BDI score was classified
into two groups: scores 0–14 (normal mood), and 15 or more (indicating elevated depressive
symptoms) [90].
The treadmill test was supervised by a physiotherapist. The patient was asked to keep a
straight, upright position during walking on ram without elevation. The starting speed was 0.67
m/s for the first 10 min (400 m), then 1 m/s for the next 10 min (600 m), with a maximum result
1,000 m in 20 min. If the patient was not able to start with a speed of 0.67 m/s, another test with
a starting speed of 0.5 m/s was applied. The walking distance scale ranged from 0 to 1000 m.
6.2.5
Statistical analyses
Associations between the quantitative evaluation of the radiological stenosis in MRI and the
continuous ODI, VAS, BDI, and walking capacity were analyzed using Spearman correlation
coefficients. The visual assessments were analyzed using t-test. Non-parametric tests were used
when no assumption of normal distribution could be made. Statistical analysis was performed
using SPSS for Windows (version 19.0; SPSS, IBM, Chicago IL, USA). Statistical significance was
set at a P < 0.05.
6.3 RESULTS
6.3.1
Clinical characteristics, preoperative symptoms, and functional disability
Patient characteristics are summarized in Table 5. The mean age of the study patients (n = 80) at
the time of surgery was 63 years (11) [mean (SD)], and 35 (44%) of the subjects were male. Ten
patients (13%) had undergone previous spine operation. Coexisting disc herniation was found
in 11 patients (14%). According to the ODI scores 7 (9%), 26 (33%), and 36 (45%) had minimal,
moderate, and severe disability, respectively, and 11 (14 %) patients were crippled. Regarding
the overall VAS scores, 28 (35%) patients had minimal pain, 20 (25%) had moderate pain, 22
35
(28%) had severe pain, and 10 (13%) had crippled pain. Regarding the BDI scale, 63 patients had
normal mood and 17 patients were depressed (15 or more points); the mean BDI was 10.4 (6.1).
Mean walking distance achieved was 545 (445) m (range, 0–1000 m).
6.3.2
Radiological findings
According to the visual assessment, none of the patients had a normal central canal. The central
canal was moderately and severely stenosed in 36 (45%) and 44 (55%) patients, respectively.
Based on the quantitative assessment, the mean minimal dural sac area was 56.1 (21.9) (range,
12–120) mm2. In the quantitative analyses the smallest dural sac was greater than 100 mm², 75–
100 mm², and under 75 mm² in 4 (5%), 15 (19%), and 61 (76%) patients, respectively.
6.3.3
Correlation of imaging findings with preoperative symptoms and functional
disability
The correlation of radiological spinal stenosis and clinical symptoms is summarized in Table 5.
VAS leg pain was higher in patients with moderate stenosis than in patients with severe
stenosis (7.33 (2.29) vs 5.80 (2.72); P = 0.008) (Figure 8). The walking distance achieved was
shorter in patients with radiologically moderate stenosis than in patients with severe stenosis
(421 (431) m vs 646 (436) m; P = 0.021) (Figure 9). Patients with severe stenosis at only one level
(50%) achieved shorter walking distance than patients with severe stenosis of at least two levels
[393 (436) m vs 675 (423) m; P = 0.022]. No correlation was found between the dural sac area
measurements and patient symptoms or walking distances achieved (Table 6).
6.4
DISCUSSION
The strength of this study was its prospective study design for both radiological and clinical
methods. The main finding of our study was that there is no linear correlation in the
radiological degree of severity of LSS and clinical findings. In contrast, according to the visual
evaluations of the central canal LSS, leg pain measured by VAS was higher in the moderate
stenosis group than in severe stenosis group. Additionally, the walking distance achieved was
shorter in the patients with moderate stenosis on visual evaluation compared with the patients
with severe stenosis. This finding was consistent for both the analysis performed using the
maximal degree of stenosis and among patients with multilevel stenosis. We did not find any
correlation between objective quantitative radiological measures and patient symptoms, which
also supports the paradoxical finding based on visual evaluation.
Our results indicate that LSS is not solely an anatomical disorder, but that this disease may
have other underlying pathobiological mechanisms to be discovered. Indeed, we found that the
correlation between the severity of LSS and clinical findings is complex, with milder symptoms
in patients with more severe stenosis. In a cross-sectional study setting, we cannot provide a
36
definite explanation for our findings. Our results raise the possibility that the pain of patients
could resolve spontaneously across time and that this adaptation could possibly explain the
longer walking distance achieved in this group of patients regardless of the progression in the
severity of the central LSS. One possible explanation to our apparently paradoxical findings
could be the decreased lumbar spine instability in patients with advanced facet joint
hypertrophy and large end-plate osteophytes, which in turn would provide pain relief and
allow higher walking capacity. Accordingly, degenerative hypertrophy could be a protective
mechanism against the disc degeneration typically found in patients with advanced age. Porter
and Ward hypothesized that central stenosis at two levels or central stenosis at one level with
lover root canal stenosis may cause venous congestions and may explain neurogenic
claudication [27]. We are not aware of the methods to assess venous congestion on the MRI,
which could be a potential target of future research.
Sirvanci et al. found no correlation between the severity of spinal stenosis and ODI. The
aforementioned study, however, was retrospective and patient symptoms were evaluated only
by the ODI scale. Moreover, no data of the experience of the subjects performing the
radiological analysis were provided in that study [16]. Accordingly, it is difficult to evaluate the
reliability of the radiological analysis. In the study by Geisser et al, no correlation was found
between the quantitative measurement of central spinal canal AP diameter and clinical
symptoms [18]. Assessment of spinal canal AP diameter may be problematic in the context of
LSS because, according to our experience, the most common reason for LSS is facet joint
hypertrophy that causes bilateral stenosis of the dural sac and does not influence the midsagittal level. Jonsson et al found a weak positive correlation between the central spinal canal
AP diameter and reduction of the patient’s estimated walking ability; however, that correlation
was not statistically significant [19]. Haig et al evaluated the LSS by measuring the area of the
minimal dural sac cross-sectional area, as also performed in our study, and they found no
difference in the degree of stenosis between symptomatic and asymptomatic subjects [15].
Interestingly, in the one other study using validated methods to record patient symptoms,
patients with multilevel spinal stenosis had significantly better scores in the general health
items of the Short Form-36, and similar to our findings, moderate lower leg pain measured with
the VAS-scale [17]. Further, Park et al found that there was less pain radiation and
pseudoclaudication in patients with three- and two-level spinal stenosis compared with patients
with one-level stenosis only [91]. In contrast, Ogikubo et al found lowered preoperative walking
capacity, higher leg and back pain and reduced quality of life in LSS patients with smaller dural
sac cross-sectional area [14]. Furthermore, Yukawa et al found a positive correlation between
the preoperative dural cross-sectional area in magnetic resonance imaging and with a better
postoperative ODI score [48]. The aforementioned and many other studies [15-19] did not
analyze spinal canal stenosis visually, which we considered an elemental part of the image
analysis, especially in patients with stenosis at the upper part of the lumbar spine. The amount
of neural tissue at L1-2 and L2-3 levels is considerably greater than at the L4-5 or at the
37
presacral measurements, and thus, by performing dural sac cross-sectional area measurements
only, subjects with reduced space for neural tissue may not be correctly recognized.
We did not execute intra-rater and inter-rater repeatability of MRI evaluation, and this is
the main weakness of this study. However, we consider that such a measurement was not
related to the present study aim. Notably, reliability of the qualitative grading of LSS has been
described and evaluated previously, and it was shown to have substantial intraobserver and
moderate interobserver agreement in a multicenter study setting (37). In the present study
methods, a 7-grade classification was used (37). However, Lurie et al used a 4-grade
classification in their study and showed moderate to substantial reliability (92). Moreover, we
have recently extended the method of the assessment of lateral stenosis using a 3-grade
classification, which has been demonstrated to have acceptable repeatability for research
purposes (40). Future objective would be standardized studies of visual assessment of the LSS
and to analyze how these findings correlate with patient symptoms and surgical outcomes.
The results of the current study relate to routine clinical MRI with patients lying in the
supine position. Imaging studies of patients in this position is a limitation because patient
symptoms may worsen in an upright position. Further, the anatomy of the neural canal may
appear altered when patients are in an upright position. Accordingly, the upright position
would be the most appropriate imaging acquisition posture to link imaging findings to patient
symptoms [13, 35-36]. Hiwatashi et al found that axial loading while performing imaging
studies could even influence to treatment decisions [36].
The incidence of LSS is increasing probably because of the better quality and availability of
radiological imaging equipment, and facilities, added to increasing aging population [12, 79],
which reflect in a higher number of LSS surgery. However, selection of patients for surgical
treatment still remains challenging. Our results strengthen the classical conception that the
diagnosis of this syndrome is constituted by the clinical history, clinical symptoms and
radiographic evidence of a demonstrable stenosis [2-4].
MRI evaluations are thus needed to establish the level(s) and severity of stenosis.
However, MRI images cannot be the only decision-making factor of surgical treatment selection
for LSS patients. The degree of the severity of the disease cannot be judged based solely on MRI
either. Ohtori et al found that proinflammatory cytokine levels in the cerebrospinal fluid of
patients with LSS correlated with the severity of the stenosis [93]. Sairyo et al found that
hypertrophy of the lumbar ligamentum flavum is associated with inflammation-related genes
[94]. Moon et al pointed out that fibrosis and scarring during inflammatory reaction is the major
pathomechanism of ligamentum flavum hypertrophy [95]. The present study adds to the
current knowledge by showing that there is no straightforward association between stenosis of
dural sac and patient symptoms or functional capacity, which indicates that dural sac stenosis is
not the only key in the pathophysiology of LSS. It is not justified to select patients for surgery
based solely on the degree of central stenosis either.
38
6.5
CONCLUSIONS
Association between the anatomical degree of LSS and the clinical findings is a complex one.
Our findings indicate that advanced degenerative hypertrophy may potentially be a protective
mechanism that causes relief of patient symptoms. Follow-up studies are needed to confirm if
symptoms of patients with LSS may improve despite the progression of the anatomical degree
of central LSS.
63.0 (11.0)
29.6 (4.0)
5.3 (3.0)
44.7 (16.1)
33.3 (23.9)
4.1 (2.6)
6.49 (2.6)
10.4 (6.1)
545 (445)
Age
BMI (kg/m²)
Number of somatic diseases
ODI
VAS overall
NRS LBP
NRS LP
BDI score
Walking distance (m)
421 (431)
9.78 (6.86)
7.33 (2.29)
4.72 (2.6)
34.6 (24.7)
45.4 (18.0)
5.6 (3.2)
29.5 (4.4)
62.0 (11.6)
72.1 (18.0)
66
70/30
55/36/9
646 (436)
10.93 (5.546)
5.80 (2.72)
3.59 (2.4)
31.9 (25.0)
44.1 (14.4)
5.1 (2.8)
29.8 (3.5)
64.0 (10.8)
43.0 (15.2)
11 (25.0)
5 (11.4)
7 (16.0)
27 (61.3)
17/27 (39/61)
Severe stenosis (n = 44)
0.258
0.104
0.971
0.021
0.233
0.008
0.059
0.523
0.731
0.445
0.746
0.413
0.000
0.365
0.248
0.345
0.762
0.308
P-value
scale leg pain at walking, scale (0–10), BDI = Beck Depression Inventory (0–63), § Percentages
deviations in parentheses. ODI = Oswestry Disability Index (0–100), VAS overall = Visual analog pain scale (0–100), NRS LBP = Numerical rating scale low back pain at rest, scale (0–10), NRS LP = Numerical rating
Except where indicated, data are numbers of patients, with percentages in parentheses or means, ± standard deviations in parentheses. ȝ BDI 15 or more points, ɫ at the most stenotic level, mean (mm²), ± standard
33
56.1 (21.9)
Minimal dural sac area ɫ
6 (16.7)
Lumbar fusion yes §
17 (21)
Depressed ȝ
6 (16.7)
53/47
11 (13)
Previous lumbar operation
10 (27.7)
Multilevel stenosis yes/no §
17 (21.3)
Current smoker
25 (69.5)
53/39/8
52 (65)
Marital status married or co-habiting
18/18 (50/50)
Moderate stenosis (n = 36)
Foraminal stenosis (normal/moderate/severe) §
35/45 (43/56)
Male/Female
All patients (n =80)
Table 5. Clinical characteristics of the study subjects
39
r= -0.036
P= 0.752
P=0.448
VAS overall scale
r= 0.086
BDI = Beck Depression Inventory (0–63)
Treadmill exercise test (0–1000 m)
NRS LP = Numerical rating scale leg pain at walking (0–10)
NRS LBP = Numerical rating scale low back pain at rest (0–10)
VAS overall = Visual analog pain scale (0–100)
ODI = Oswestry Disability Index (0–100)
P = P values
r = Spearman correlation coefficients
Central spinal canal (mm2)
ODI scale
P=0.972
r= -0.004
NRS LBP
P= 0.841
r= 0.023
NRS LP
Table 6. Correlation of the dural sac area with patient symptoms and walking capacity
40
P= 0.380
r= -0.099
Beck depression index
P = 0.200
r = -0.145
Treadmill test
a )normal
b ) moderate
c) severe
a) normal central spinal canal; b) moderate central spinal canal stenosis; c) severe central spinal canal stenosis.
Figure 7. Shows the axial T2-weighted model images of representative cases that were used to grade central spinal canal in visual asessment.
41
42
Figure 8. Visual assessment of the MRI and VAS leg pain n = 80.
Mean VAS leg pain ± 1 SD
43
Figure 9. Walking distance in the treadmill exercise test in patients with moderate and severe
spinal stenosis
Mean walking distance ± 1 SD
44
45
7 Correlation of lateral stenosis in MRI with symptoms,
walking capacity and EMG findings in patients with
surgically confirmed lateral lumbar spinal canal stenosis
Purpose: To evaluate the clinical significance of lateral lumbar spinal canal stenosis (LLSCS),
found by magnetic resonance imaging (MRI), through correlating the imaging findings with
patient symptoms, walking capacity and electromyography (EMG) measurements.
Method: 102 patients with symptoms of LSS referred for operative treatment were studied in
this uncontrolled study. Of these patients, subjects with distinct only lateral LSS were included.
Accordingly, 140 roots in 14 patients (mean age 58, range 48-76 years, male 43 %) were
evaluated. In MR images the entrance and mid zones of the lateral lumbar nerve root canal
were graded as normal, narrowed but not compressed, or compressed. In quantitative analysis,
the minimal widths of the lateral recess and mid zone area were measured. Clinical symptoms
were recorded with the Oswestry Disability Index (ODI), overall Visual Analogue Scale (VAS),
specific low back pain (LBP; NRS-11), specific leg pain (LP NRS-11), Beck Depression Inventory
(BDI) and walking distance in the treadmill test. Lumbar paraspinal (L2- L5) and lower limb (L3
– S1) needle EMG studies were performed. The findings were classified root by root as 1 =
normal, 2 = abnormal. The associations between radiological, EMG and clinical findings were
tested with each other.
Results: EMG findings were normal in 92 roots and abnormal in 48 roots. All of the patients had
at least one abnormal nerve root finding. Severity of the mid zone stenosis in MRI correlated
with abnormal EMG findings (p = 0.015). Patients with abnormal EMG had also higher scores in
the VAS (41.9 ± 25.7 vs 31.5 ± 18.1; p = 0.018), NRS leg pain (7.5 ± 1.5 vs 6.3 ± 2.1; p = 0.000) and
BDI (9.8 ± 3.8 vs 8.0 ± 3.9; p = 0.014). However, no statistically significant correlations between
MRI findings and clinical symptoms or walking capacity were found.
Conclusions: Among persons previously selected for surgery, lateral stenosis seen on MRI
correlates with EMG, and thus may be a clinically significant finding. Our EMG findings were
also associated with patient symptoms. However, no relationships between the MRI findings
and symptoms or walking capacity were found, suggesting their multifactorial etiology. MRI
and EMG may be useful in the workup of patients with suspected LLSCS.
46
7.1
INTRODUCTION
Lumbar spinal stenosis (LSS) is defined as “buttock or lower extremity pain, which may occur
with or without low back pain, associated with diminished space available for the neural and
vascular elements in the lumbar spine” [1]. Lateral lumbar spinal canal stenosis (LLSCS) is a
related condition and it is characterized by the narrowing of the lateral aspects of the central
canal (subarticular recess) or foramen through which the nerve root exits the spinal canal. LSS is
the most common indication for lumbar spinal surgery in people aged over 65 years [6]. When
successful, surgery relieves pressure on the nerves and reduces pain and weakness. However,
the long-term results of surgery are poor in one third of patients [6, 7]. Accordingly,
preoperative patient selection is considered critical. Clinically, routine magnetic resonance
imaging (MRI) and electromyography (EMG) are standard tools in the diagnostic workup of
patients with suspected LSS [15, 18-19, 22-23].
Most of the earlier studies in patients with LSS are focused on patients with central canal
stenosis. LLSCS is a controversial clinical issue. On one hand it is thought that the most
common cause for a poor surgical result in LSS surgery was failure of the surgeon to either
identify or adequately treat the LLSCS [96]. On the other hand, LLSCS is thought to be overdiagnosed because the pathology can be more readily seen on MRI and CT scans and is also
seen in asymptomatic patients.
The purpose of this study was to evaluate correlation of MRI imaging findings, EMG and
clinical patient symptoms with LLSCS patients.
7.2
7.2.1
MATERIAL AND METHODS
Patients
In this publication (III) we selected only distinct lateral spinal canal stenosis patients (n = 18) of
the 102 baseline patients. Four patients baseline data was missing, thus the final patients sample
size was 14. Accordingly, 140 roots of the 14 patients were assessed. See above 4.2.
7.2.2
Magnetic resonance imaging.
See above 6.2.2
47
7.2.3
Image Analysis
Image analysis was performed as previously described in detail [40]. Briefly, the lateral canal of
the lumbar spine was divided into subarticular (entrance) and foraminal (mid) zones. The
subarticular zone (lateral recess) was the most cephalad part of the lateral lumbar canal and
located medial to or underneath the superior articular process. The foraminal zone was located
below the pedicle. Each subarticular zone and foraminal zone was evaluated separately,
bilaterally. The observer was blinded to the clinical and radiological reports and to the findings
of any prior clinical examinations. The observer was, however, aware that all study subjects
were symptomatic. Visual assessment and quantitative measurements were performed on an
IDS5 diagnostic workstation (version 10.2P4; Sectra Imtec, Linköping, Sweden) using highly
magnified images on 1024 × 768 and 1600 × 1200 displays.
In visual analysis, the grading system classified the lumbar nerve root canals into three
grades: 0 = normal, 1 = narrowing without root compression and 2 = nerve root compression. In
quantitative analysis, the minimal width of the subarticular (entrance) zone (lateral recess) and
the cross-sectional (mm²) area of the foraminal zone (mid zone area) were measured. At the
foraminal zone, no space below the line parallel to the lower end plate was included in area
measurements as previously described in detail [40]. Repeatability of assessments has been
previously studied and shown to vary from moderate to substantial [40].
7.2.4
Assessment of preoperative symptoms and functional disability
The overall current low back and leg pain intensity was assessed by a self-administered Visual
Analogue Scale (VAS) (range 0-100 mm) in a sitting position during study visits. This has been
proved to be a valid index of experimental, clinical and chronic pain [65]. Back pain at rest
(during the previous week) and leg pain when walking (during the previous week) were
measured separately with a numeric rating scale 0-10 (NRS-11) [87]. The questions about pain
were anchored on the left (0) with the phrase “No pain” and on the right (10) with the phrase
“intolerable pain”.
Subjective disability was measured by the validated Finnish version of the Oswestry
Disability Index, where 0% represents no disability and 100% extreme debilitating disability [6263, 83]. Depression was assessed with the Finnish version of the 21-item Beck Depression
Inventory (BDI) with scores ranging from 0 to 63 [71, 84].
The treadmill test was supervised by a physiotherapist. The patient was asked to keep a
straight, upright position during walking (with a zero degree ramp). The starting speed was
0.67 m/s for the first 10 min (400 m), then 1 m/s for the next 10 min (600 m); maximum results
were thus 1000 m in 20 min. If the patient was not able to start with a speed of 0.67 m/s, another
test with a starting speed of 0.5 m/s was applied. Thus the walking distance scale was 0-1000 m.
48
7.2.5
EMG
Lumbar paraspinal and lower limb needle EMG were recorded pre-operatively by a
neurophysiologist (SM or AP) who was blinded to the radiological data and clinical assessment.
The EMG investigation included bilateral paraspinal muscles innervated by the L2-L5 posterior
primary rami and a symptomatic lower limb muscles (roots L3 - S1). Examination of the
paraspinal roots was performed using a monopolar needle electrode (Medtronic, 50 x 0.40 mm)
and examination of the lower limb muscles using a concentric (Neuroline, 38 x 0.45 mm) needle
electrode. Amplification was set at 50 μV/div, and the high and low-pass filters at 10 kHz and
20 Hz, respectively.
The aim of the needle examination was to detect the abnormal spontaneous activity
associated with axonal damage (fibrillation and positive sharp waves) [22]. Our EMG data was
scaled in the following way: 0 = none or no reproducible spontaneous activity, 1 = rare or
occasional (two or more) trains of fibrillation potentials, 2 = frequent spontaneous potentials
recordable at more than one depth, 3 = abundant spontaneous activity nearly filling the screen.
Categories 1-3 were considered abnormal.
During paraspinal EMG, the patient would lie in the prone position supported by pillows
underneath the abdomen. The L3-4 interspinal space was determined by first locating the
interspinal space at the level corresponding to the iliac crest, then identifying the L3, L4, L5 and
S1 spinal processes by palpation. At least 20 insertions were analyzed from each multifidus
muscle. The aim of the examination was to detect the abnormal spontaneous activity suggesting
lower motor neuron disorder, and thus serving as a sign of denervation. Abnormal activity
indicating denervation was considered to be fibrillation potentials, positive sharp waves, and
complex repetitive discharges.
Lower limb needle EMG was performed with the patient lying in the supine position,
considering assessment of m. vastus lateralis, tibialis anterior, extensor hallucis longus and
gastrocnemius (roots L3 -S1).
The recording of tibial H-waves and peroneal F-waves was performed with Keypoint
EMG equipment (Skovlunde, Denmark), using the H-wave and F-wave programs (20
successive samples, 1 stimulus per second, stimulus duration 0.2 ms, high pass filter 20 Hz, low
pass filter 10 kHz, sensitivity 0.2 mV/div, sweep 10 ms/div). The stimulus intensity for Fresponses was adjusted to obtain supramaximal M-response amplitude. The F-responses were
recorded using a surface electrode placed over the middle of the short toe extensor muscle. The
reference electrode was placed over the first metatarsal bone on the dorsal surface of the foot.
The stimulus intensity for H-responses was adjusted to get repeatable responses with identical
latency. The stimulus site was the popliteal fossa and the H-responses were recorded by surface
electrodes over the gastrocnemius muscle. The latencies of the minimum F-response (Fmin) and
H-response were determined. The recorded values were compared to the normal material of the
laboratory (120 normal values) taking the height of the subject into account. The deviation from
49
the normal value was expressed as standard deviation (SD). SD values higher than 2.5 SD were
considered abnormal.
Nerve root level specific (L2 – S1) EMG was abnormal if abnormal spontaneous activity
associated with axonal damage (fibrillation and positive sharp waves) was found in the limbs or
paraspinals. Specific nerve root involvement was defined by that nerve root innervated
paraspinal muscles (roots L2 – L5) or lower limb muscles (vastus lateralis, tibialis anterior,
extensor hallucis longus and gastrocnemius) (roots L3 – S1). The EMG findings were classified
root by root as 1) normal (92/140 roots) or 2) abnormal (active paraspinal and/or limb lesion
(48/140).
7.2.6
Statistical analyses
In statistical analyses, MRI and EMG were analyzed root by root. Associations between MRI
findings with VAS, BDI, walking capacity and EMG were analyzed using Chi-squared tests,
Spearman and Pearson correlation coefficients, t-tests, and when no assumption of normal
distribution could be made, non-parametric tests were used. Statistical analysis was performed
using SPSS for Windows (version 19.0; SPSS, IBM, Chicago IL, USA). Statistical significance was
set at the P < 0.05 level.
7.3
RESULTS
Patient characteristics are summarized in Table 7. The mean age of the study patients (n = 14) at
the time of surgery was 58 years (range 48-76), and 6 (42 %) of the subjects were male. None of
the patients had undergone previous spine surgery. Co-existing disc herniation was found in
one patient (7 %).
According to the ODI scores, 1 patient (7 %) had minimal disability (scores 0-20), 4
patients (29 %) had moderate disability (scores 21-40), 9 patients (64 %) had severe disability
(scores 41-60), and none of the patients were crippled (scores over 60). In the overall VAS scores,
3 patients (21 %) had minimal pain (scores 0-20), 7 (50 %) had moderate pain (scores 21-40), 2
(14 %) had severe pain (scores 41-60) and 2 (14 %) had crippling pain (scores >60). In the BDI
scale, 12 patients had normal mood and 2 patients were depressed (15 or more points), with a
mean BDI of 8.6 (SD 4.1) and the walking distance was 829 ± 310 meters (Table 7).
By MRI, the lateral spinal canal recess appeared normal in 93 roots, narrowed in 35 roots
and compressed in 12 roots. Also according to our MRI findings, the lateral foraminal canal was
normal in 111 roots, narrowed in 26 roots and compressed in 3 roots. The mean entrance zone
width of the lateral spinal canal was 5.3 (1.8) mm and the foraminal zone area was 69.3 (17.6)
mm², respectively.
50
The EMG findings were normal in 92 (66 %) roots and abnormal in 48 (34 %) roots. Level
by level EMG data were as follows: L2; 27 roots normal and 1 root abnormal, L3; 11 roots
normal and 17 roots abnormal, L4; 19 roots normal and 9 roots abnormal, L5; 14 roots normal
and 14 roots abnormal, S1; 21 roots normal and 7 roots abnormal.
F-responses were bilaterally normal in 4 patients, one-side were normal and one-side were
abnormal in 5 patients and bilateral abnormal F-responses were in 5 patients, respectively. Hresponses were bilaterally normal in 6 patients, one-side were normal and one-side were
abnormal in 3 patients and bilateral abnormal H-responses were in 5 patients, respectively.
7.3.1
Correlation of MRI findings with clinical symptoms
Visually assessed severity of entrance stenosis, mid zone stenosis, entrance zone width, and
mid zone area did not correlate with the clinical symptoms recorded; ODI, VAS, specific low
back pain (LBP; NRS-11), specific leg pain (LP NRS-11), BDI and walking distance achieved in
the treadmill test.
7.3.2
Correlation of clinical symptoms with EMG findings
Patients with abnormal EMG findings had higher scores in the VAS (41.9 ± 25.7 vs 31.5 ± 18.1; p
= 0.018), VAS leg pain (7.5 ± 1.5 vs 6.3 ± 2.1; p = 0.000) and BDI (9.8 ± 3.8 vs 8.0 ± 3.9; p = 0.014)
(Table 8).
7.3.3
Correlation of MRI and EMG findings
Abnormal EMG correlated with the severity of mid zone stenosis in the visual assessment (p =
0.015). The entrance zone width was also somewhat lower in the roots with abnormal EMG (5.1
± 1.7 mm vs 5.7 ± 1.9 mm; p = 0.050).
7.4
DISCUSSION
To the best of our knowledge, there are no previous studies investigating the severity of LLSCS
by MRI and its associations with clinical symptoms and EMG findings. This study points out
that there are associations between MRI-assessed LLSCS and abnormal EMG, indicating that
LLSCS is a clinically significant finding. However, the severity of the LLSCS measured from
MRI data did not correlate with the clinical symptoms. This may be explained by the small
study sample but also by the multifactorial etiology of symptoms.
However, abnormal EMG findings were associated with the overall VAS, leg pain VAS
and BDI, which suggests that EMG could be more sensitive than MRI for the detection of
LLSCS.
In the context of previous publications [15, 18-19], we did not find significant associations
between the severity of stenosis in MRI and patient symptoms. However, we found associations
between EMG and clinical symptoms. To the best of our knowledge there are no other
51
prospective (LLSCS) studies evaluating the associations between EMG, MRI findings and
clinical symptoms.
The strengths of this study are prospective study setting, recording of symptoms with
validated questionnaires and tests, detailed visual and quantitative MRI analysis with
confirmed reproducibility. The results of the current study relate to routine clinical MRI with
patients lying in the supine position. Imaging patients in the supine position is a limitation
because patient symptoms may worsen in the upright position and the upright position may
also alter the anatomy of the neural canal. Accordingly, the upright position would be the most
appropriate image acquisition position to link image findings to patient symptoms [13, 35, 97].
Hiwatashi and colleagues found that axial loading with imaging can even influence treatment
decisions [36]. Another limitation of this study is the small sample size; however, it is still large
enough to provide the main results.
Lateral canal is a relatively small structure and use of 4 mm thick transversal slices, that
were used to analyze subarticular zone, is suboptimal to visualize nerve roots accurately. It
should be noted that at the subarticular zone the course on nerve root may be oblique to slice
orientation and thinner slice thickness would provide higher accuracy especially for
quantitative measurements. Moreover, even though we characterized some nerve roots to be
compressed, we were not able to detect anatomical changes in nerve roots that would confirm
the presence of true compression [98]. In optimal condition high resolution imaging with
isotropic voxels conjoined with functional provocations could possibly improve diagnostic
accuracy. Unfortunately such methods are not available for clinical routine. However, 3D
isotropic SPACE sequence is currently available but it has not yet shown to improve diagnostic
accuracy compared to 2D imaging [99].
We did not use paraspinal mapping technigue for EMG analysis which can be as a
methodology weakness [15]. However our EMG analysis criterions are precise and the results
are considered comparable with mapping technique.
Incidence of lumbar spinal stenosis is increasing due to the aging population [12, 79].
Lumbar stenosis is detected also more frequently these days, due to the better quality and
availability of radiological imaging facilities. These factors also increase the number of LSS
operations. However, the selection of patients for surgical treatment still remains challenging.
Our result strengthens the classical perception that the diagnosis of this syndrome arises from
clinical history and radiographic evidence of a demonstrable stenosis [2-4].
The present study adds to the current knowledge by showing that EMG findings correlate
with clinical symptoms in patients with LLSCS. This study also supports both the clinical use
and research use of quantitative radiological classification of lateral spinal stenosis.
52
7.5
CONCLUSIONS
Conclusions: Among persons previously selected for surgery, lateral stenosis seen on MRI
correlates with EMG, and thus may be a clinically significant finding. Our EMG findings were
also associated with patient symptoms. However, no relationships between the MRI findings
and symptoms or walking capacity were found, suggesting their multifactorial etiology. MRI
and EMG may be useful in the workup of patients with suspected LLSCS.
53
Table 7. Clinical characteristics of the study subjects with lateral spinal stenosis (n = 14 patients).
Male/Female
6/8 (43/57)
Marital status; married or co-habiting
9 (64)
Current smoker
2 (14)
Age
58 (range 48-76)
BMI (kg/m²)
27.3 (3.8)
Number of somatic diseases
5.8 (3.9)
ODI
41.5 (9.6)
VAS overall
35.1 (22.2)
NRS LBP
4.4 (3.0)
NRS LP
6.7 (2.1)
BDI score
8.6 (4.1)
Walking distance (m)
829 (310)
Note: Except where indicated, data are numbers of patients, with percentages in parentheses or
means, ± standard deviations in parentheses.
ODI = Oswestry disability index scale (0-100), VAS overall = Visual analogue pain scale (0-100),
NRS LBP = NRS low back pain at rest, scale (0-10), NRS LP = NRS leg pain at walking, scale (010), BDI = Beck Depression inventory (0-63).
54
Table 8. Comparison of normal and abnormal EMG groups with clinical data (n = 14).
Normal EMG
Abnormal EMG
p value
ODI
41.1 (9.3)
42.2 (9.4)
p = 0.280
VAS
31.5 (18.1)
41.9 (25.7)
p = 0.018
NRS leg pain
6.3 (2.1)
7.5 (1.5)
p = 0.000
NRS low back pain
4.2 (2.7)
4.8 (3.2)
p = 0.400
BDI
8.0 (3.9)
9.8 (3.8)
p = 0.014
Treadmill test
700 (426)
740 (385)
p = 0.642
Data are means, ± standard deviations in parentheses.
ODI = Oswestry disability index scale (0-100), VAS overall = Visual analogue pain scale (0-100),
NRS LBP = NRS low back pain at rest, scale (0-10), NRS LP = NRS leg pain at walking, scale (010), BDI = Beck Depression inventory (0-63), treadmill exercise test (0-1000 metres).
55
8 Preoperative MRI findings predict two-year postoperative
clinical outcome in lumbar spinal stenosis
Purpose: To study the predictive value of preoperative magnetic resonance imaging (MRI)
findings for the two-year postoperative clinical outcome in lumbar spinal stenosis (LSS).
Methods: 84 central lumbar spinal canal stenosis patients (mean age 63 ± 11 years, male 43%)
with symptoms severe enough to indicate LSS surgery were included in this prospective
observational single-center study. Preoperative MRI of the lumbar spine was performed with a
1.5-T unit. The imaging protocol conformed to the requirements of the American College of
Radiology for the performance of MRI of the adult spine. Visual and quantitative assessment of
MRI was performed by one experienced neuroradiologist. At the two-year postoperative
follow-up, functional ability was assessed with the Oswestry Disability Index (ODI 0–100%)
and treadmill test (0–1000 m), pain symptoms with the overall Visual Analogue Scale (VAS 0–
100 mm), and specific low back pain (LBP) and specific leg pain (LP) separately with a numeric
rating scale from 0–10 (NRS-11). Satisfaction with the surgical outcome was also assessed.
Results: Preoperative severe central stenosis predicted postoperatively lower LP, LBP, and VAS
when compared in patients with moderate central stenosis (p < 0.05). Moreover, severe stenosis
predicted higher postoperative satisfaction (p = 0.029). Preoperative scoliosis predicted an
impaired outcome in the ODI (p = 0.031) and lowered the walking distance in the treadmill test
(p = 0.001). The preoperative finding of only one stenotic level in visual assessment predicted
less postoperative LBP when compared with patients having 2 or more stenotic levels (p =
0.026). No significant differences were detected between quantitative measurements and the
patient outcome.
Conclusions: Routine preoperative lumbar spine MRI can predict the patient outcome in a twoyear follow up in patients with LSS surgery. Severe central stenosis and one-level central
stenosis are predictors of good outcome. Preoperative finding of scoliosis may indicate worse
functional ability.
56
8.1
INTRODUCTION
Lumbar spinal stenosis (LSS) is defined as “buttock or lower extremity pain, which may occur
with or without low back pain (LBP), associated with diminished space available for the neural
and vascular elements in the lumbar spine” [1, 100]. LSS is the most common indication for
lumbar spinal surgery in people aged over 65 years. Incidence of lumbar spinal stenosis is
increasing due to the aging population, which increase also the frequency of more complex
lumbar spine procedures, which in turn is associated with the more demand for the healthcare
[6]. The aim of surgery is to improve functional ability and relieve symptoms with adequate
decompression of the neural elements. However, the long-term results of surgery are good to
excellent only in two-thirds of patients [6, 7]. Accordingly, preoperative patient selection is
considered critical [8-11]. Clinically, routine magnetic resonance imaging (MRI) is the standard
method in the diagnostic workup of patients with suspected LSS [18-19]. However, impacts of
the MRI findings to the patients’ symptoms have been also questioned [15].
We have earlier reported that depressive symptoms are a strong predictor for a worse
short-term outcome [9, 101] and for the two-year outcome in LSS surgery [10]. Depression and
disability were also clearly associated in a cross-sectional setting [80].
There are several a cross-sectional studies on preoperative radiological findings and
preoperative patient’s symptoms, but only few with prospective setting. A clear association in a
cross-sectional setting has been reported between the minimum dural sac cross-sectional
(DSCA) area in lumbar MRI and several outcome measures (walking ability, symptom severity,
quality of life) with the 82 and 88 LSS patient groups [13, 14]. In another study with 50 patients
population a smaller central anterior–posterior (AP) canal have reported greater postoperative
disability, but no other group differences emerged [18]. In contrast, a lack of association has
been reported between the ODI and DSCA, qualitative evaluation of the lateral recess, and
foraminal stenosis with the 63 LSS patients [16]. Thus there is discrepancy in the previous
literature.
Yukawa et al reported in their prospective study that 62 LSS patients with the multilevel
central stenosis were on average older and walked a shorter distance preoperatively and
postoperatively, although the improvement in their postoperative self-assessment scores was
similar to that of patients with single-level stenosis [48]. Sigmundsson et al. investigated the
predictive value of MRI findings among a study population consisting of 109 LSS patients
undergoing surgery with a one-year follow-up. They found in their prospective study that a
smaller dural sac area predicted less leg pain postoperatively and more pain relief in low LBP
[49]. None of these studies have, however, investigated the predictive value of visual and
quantitative findings from preoperative lumbar spine MR images for both subjective and
objective clinical outcome measures with a two-year follow-up [48, 49].
57
The use of the standardized Oswestry Disability Index (ODI) [62, 63], visual analogue
scale for pain (VAS) [65], Beck Depression Inventory (BDI) [71], and specific back pain and leg
pain assessment with a numeric rating scale (NRS-11) [87] has improved the accuracy and
reproducibility in reliably grading functional disability, pain and depressive symptoms in
patients. Keeping in mind the strong association of depressive symptoms and outcome
measures of LSS, depressive symptoms should be adjusted. As far as we are aware, there have
been no earlier LSS studies on MRI predictors that have adjusted the clinical outcome for
depressive symptoms.
The purpose of the current study was to investigate the predictive value of preoperative
MRI findings for the postoperative clinical outcome by comparing the preoperative imaging
findings with the postoperative symptoms and function measured using standardized methods
in a prospective study setting in LSS.
8.2
8.2.1
MATERIAL AND METHODS
Patients
In this publication (IV) we selected only central spinal stenosis patients (n = 84) of the 102
baseline patients. Only distinct lateral spinal canal stenosis patients were excluded. See above
4.2.
8.2.2
Magnetic resonance imaging
See above 6.2.2
8.2.3
MRI predictors
Image evaluation was performed with Numaris software (Siemens Medical Systems) by a
neuroradiologist with 15 years of experience of spinal MRI (T.S.). Image analysis was
performed independently without knowledge of the patients’ clinical symptoms and data. Each
level from the inferior aspect of L1 to the inferior aspect of S1 was analyzed separately. The
central spinal canal was evaluated both visually and quantitatively. The lateral recess, lateral
foramen, scoliosis, stenotic levels and spondylolisthesis were evaluated visually. The central
canal was visually classified into three grades: 0 = normal or mild changes (ligamentum flavum
hypertrophy and/or osteophytes and/or or disk bulging without narrowing in the central spinal
canal); 1 = moderate stenosis (central spinal canal is narrowed but spinal fluid is still clearly
visible between the nerve roots in the dural sac); 2 = severe stenosis (central spinal canal is
narrowed and there is only a faint amount of spinal fluid or no fluid between the nerve roots in
the dural sac). In quantitative image evaluation, each level was first assessed visually. On the
image with the visually smallest cross-sectional area of the dural sac (mm²), this area was
manually traced. The number of stenotic levels was graded as: 1 = 1 stenotic level, 2 = two
58
stenotic levels, 3 = three stenotic levels, 4 = four stenotic levels. The number of stenotic levels
was also dichotomously classified as 1 (one-level stenosis) or 2 (two or more stenotic levels).
The lateral canal of the lumbar spine was divided into subarticular (entrance) and
foraminal (mid) zones. The subarticular zone (lateral recess) was the most cephalad part of the
lateral lumbar canal and located medial to or underneath the superior articular process. The
foraminal zone was located below the pedicle. Each subarticular zone and foraminal zone was
evaluated separately and bilaterally. In visual analysis, the grading system classified the lumbar
nerve root canals into three grades: 0 = normal, 1 = narrowing without root compression and 2 =
nerve root compression [40].
Scoliosis was evaluated visually of MRI pictures and categorized into: 0 = no scoliosis, 1 =
mild scoliosis, 2 = severe scoliosis. Spondylolisthesis was visually analyzed and categorized as 0
= no spondylolisthesis or 1 = spondylolisthesis.
8.2.4
Assessment of postoperative symptoms, functional disability and satisfaction with
surgical outcome
The overall current low back and leg pain intensity was assessed using a self-administered VAS
(range 0–100 mm) in a sitting position during study visits. This has been demonstrated to be a
valid index of experimental, clinical, and chronic pain [65].
Back pain at rest (during last week) and leg pain on walking (during last week) were
measured separately with a numerical rating scale from 0–10 (NRS-11) [87]. The questions about
pain were anchored on the left (0) with the descriptor “no pain” and on the right (10) with the
descriptor “intolerable pain”. Subjective disability was measured using the validated Finnish
version of the ODI, where 0% represents no disability and 100% extreme debilitating disability
[62-63, 83].
The treadmill test (0–1000 m) was supervised by a physiotherapist. The patient was asked
to keep a straight upright position during walking (on a zero-degree ramp). The starting speed
was 0.67 m/s for the first 10 min (400 m), then 1 m/s for the next 10 min (600 m), and the
maximum result was thus 1000 m in 20 min. If the patient was unable to start with a speed of
0.67 m/s, another test with a starting speed of 0.5 m/s was applied.
Satisfaction with the surgical outcome was assessed using a seven-category scale as
follows: -3 = surgery was a total failure; -2 = condition is now considerably worse; -1 = condition
is now slightly worse; 0 = no change; 1 = condition has slightly improved; 2 = condition has
considerably improved; and 3 = totally cured. With respect to satisfaction, a “good outcome”
consisted of those patients who were either “totally cured” or reported “condition considerably
improved”, whereas a “worse outcome” consisted of the other responses [I].
59
8.2.5
Statistical analyses
Analysis was performed using a general linear univariate model, and for patient satisfaction
using a generalized linear model. Adjusting factors in the analysis were the age at operation
(years), spondylodesis (yes/no) at operation (with or without instrumentation), and depressive
symptoms (Beck Depression Inventory as a continuous scale, 0–63) [71] at two-year follow-up.
The predictive value of the radiological factors was assessed as follows: all the MRI predictors
and adjusting factors were included together in the model, and tested together against each
outcome measure. We applied a backward stepwise method in the analysis, using SPSS for
Windows (version 19.0; SPSS, IBM, Chicago IL, USA). Statistical significance was set at p < 0.05.
8.3
8.3.1
RESULTS
Preoperative clinical characteristics and surgical outcome
Patient characteristics are summarized in Table 9. The mean age of the study patients (n = 84) at
the time of surgery was 63 years (range 33–83), and 36 (43%) of the subjects were male. Twelve
patients (14%) had undergone a previous spine operation. All the pre- and postoperatively
evaluated outcome measures displayed a statistically significant improvement after surgery (p <
0.001; Table 8.1). Postoperative satisfaction was as follows: 9 (11.1%) "totally cured"; 39 (48.1%)
"considerable improvement"; 25 (30.9%) "slight improvement"; 2 (2.5%) "no change"; 3 (3.7%)
"condition is now slightly worse”; and 3 (3.7%) patients “considerably worse outcome”.
8.3.2
Radiological findings
In visual analysis, none of the patients had a normal central canal. The central canal was
moderately and severely stenosed in 40 (47.6%) and 44 (52.4%) patients, respectively. In
quantitative analysis, the mean minimal DSCA was 55.2 ± 20.9 mm2 (range 12–120). The lateral
spinal canal recess was moderately and severely stenosed in 60 (71.1%) and 24 (28.9%) patients,
respectively. The lateral spinal foramina was normal, moderately, and severely stenosed in 47
(55.4%), 30 (36.1%), and 7 (8.4%) patients, respectively. One-, two-, three-, and four-level central
stenosis was observed in 29 (34.5%), 34 (40.5%), 13 (15.5%), and 8 (9.5%) patients, respectively.
In dichotomous classification, one-level stenosis was recorded in 29 (34.5%) and stenosis of two
or more levels in 55 (65.5%) patients. Scoliosis was severe in 3 (3.6%), mild in 19 (22.9%) and
normal in 61 (73.5%) patients. One-level spondylolisthesis was found in 2 (2.4%) patients.
8.3.3
Predictive value of imaging findings for 2-year postoperative outcome
In parentheses below, the means and standard deviations of the study groups are presented, in
addition to p-values and statistical tests of subgroups not mentioned in the methods.
60
Severe stenosis predicted less postoperative LP compared to moderate stenosis (2.75 ± 2.6
vs 4.25 ± 3.1; p = 0.028). Nevertheless, the improvement in LP was statistically also significant
among patients in the moderate stenosis group (p < 0.001; paired t-test).
Similarly, severe stenosis predicted less postoperative LBP compared to moderate stenosis
(1.6 ± 2.3 vs 2.4 ± 2.5; p = 0.046). The improvement in LBP was also statistically significant
among patients in the moderate stenosis group (p < 0.001; paired t-test).
Moreover, severe stenosis predicted a lower postoperative overall VAS score compared to
moderate stenosis (7.8 ± 13.2 vs 17.8 ± 20.9; p = 0.010) (Figure 10). The improvement in the VAS
score was also statistically significant among patients with moderate stenosis (p < 0.001; paired
t-test).
Finally, severe stenosis predicted better postoperative satisfaction with the surgical
outcome compared to moderate stenosis (OR 0.297; 95% CI 0.100–0.880; p = 0.029).
Mild scoliosis predicted a worse 2-year outcome with the ODI compared to patients who
had no scoliosis (34.3 ± 21.5 vs 24.6 ± 18.5; p = 0.031). The improvement in the ODI was also
statistically significant among patients with scoliosis (p = 0.003; paired t-test).
In addition, scoliosis predicted a shorter postoperative treadmill test result compared to
patients who had no preoperative scoliosis (547 m ± 464 m vs 820 m ± 315 m; p = 0.001). The
improvement in walking ability in the treadmill test was not statistically significant among
patients with scoliosis (p = 0.397; paired t-test).
One-level central stenosis predicted lower postoperative LBP compared to patients who
had two or more stenotic levels (1.55 ± 2.1 vs 2.22 ± 2.5; p = 0.026).
We did not find any predictive value for quantitative evaluation of the central spinal canal
or visual evaluation of spondylolisthesis, the lateral spinal canal recess and foramina.
8.4
DISCUSSION
Our main finding was that the visually evaluated severity of lumbar spinal stenosis correlated
with the postoperative clinical outcome. Interestingly, in the visual classification of the central
spinal canal, the LP, LBP, and overall VAS were postoperatively higher in patients with
moderate than with severe central canal stenosis. In addition, more severe stenosis also
associated with better postoperative satisfaction with the surgical outcome. However, according
to subgroup analysis, patients with only moderate stenosis also displayed a statistically
significant improvement in LP, LBP, and overall VAS. Thus, patients with only moderate
stenosis still appear to experience significant pain relief following surgical treatment for LSS.
Mild scoliosis predicted a worse postoperative ODI and walking distance in the treadmill
test compared with patients who had no scoliosis. However, despite the scoliosis, subgroup
analysis revealed that patients had a significant improvement in the ODI but not in the walking
distance in the treadmill test. Consistently with this, Frazier et al. observed that greater
61
preoperative scoliosis predicted more postoperative back pain. However, their radiological
evaluation was based on plain X-ray images [47]. In our study, scoliosis also predicted a worse
postoperative outcome in the ODI and treadmill test, but not worse LBP. Thus, patients who
have scoliosis still benefit from surgical treatment for LSS in terms of their overall functional
ability, but the effect on walking ability appears to be non-significant.
Patients who preoperatively had only one stenotic level reported lower postoperative LBP
than patients who had two or more stenotic levels. This could be expected, since the
degenerative changes are then also often more severe. In contrast, Sigmundsson et al. found
that multilevel stenosis patients had less leg pain postoperatively than patients with single-level
stenosis [20]. Amundsen et al. did not find any association between the number of stenotic
levels and the surgical outcome in their study [43].
In the literature, there are only a few earlier prospective studies on the predictive value of
preoperative MRI findings for an adequately determined postoperative clinical outcome on
two-year follow-up. Yukawa et al. observed a correlation between better postoperative ODI
scores in patients who had a DSCA under 70 mm2 in preoperative MRI [48]. However, the
authors did not visually evaluate the severity of stenosis, which we found an elementary part of
image analysis, especially in patients with stenosis in the upper part of the lumbar spine.
Sigmundsson et al. found in their prospective study that a smaller dural sac area predicted less
leg pain postoperatively and more pain relief for LBP. However, they did not visually evaluate
the severity of LSS, and walking distance was only subjectively estimated by the patient,
depressive symptoms were not adjusted, and the clinical outcome was only evaluated with a
one-year follow-up [49]. Our results are generally in line with these studies, i.e. more severe
visually determined preoperative central canal stenosis predicted less pain and better
satisfaction postoperatively.
Studies on visually analyzed spinal canal stenosis of the whole lumbar spine are rare. In
our study, we found a clear correlation between visually assessed central spinal canal stenosis
and the patient outcome, but no correlation in quantitative preoperative measurements. How
can this discrepancy be explained? The amount of neural tissue at the L1–2 and L2–3 levels is
significantly greater than at the L4–5 or presacral levels. Thus by measuring only the crosssectional area of the dural sac, subjects with reduced space for neural tissue may not be
correctly recognized. According to our findings, quantitative evaluation with the used methods
cannot replace visual interpretation performed by an experienced radiologist. To the best of our
knowledge, there have been no previous prospective studies in which the predictive value of
lateral spinal stenosis has been examined. Despite the visually evaluated lateral spinal recess
and foraminal stenosis not predicting any postoperative outcome in our study, it may have
clinical relevance. Lateral stenosis, if not decompressed properly, might be associated with a
poor outcome. All our patients had central canal stenosis, which is always associated with a
stenotic lateral recess but only few had foraminal stenosis, which may explain our results.
62
The strengths of this study are the prospective, observational study setting, carefully
characterized study population. The study included clinically relevant subjective and validated
outcome measures together with objectively measured walking distance, and the analyses were
adjusted for depressive symptoms, age, and fusion. A two-year follow-up is considered as a
“golden standard” in spine surgery studies. The standardized MRI protocol was planned and
carefully performed for the study purposes, and the evaluation was performed with visually
and quantitatively by an experienced neuroradiologist.
The limitation of this study are relatively small number of the patients, however number
of the patients in the previous prospective studies are less than in this study expect in the study
by Sigmundsson et al where was several shortages compared to this study as pointed out earlier
(49). In our study number of patients was sufficient for detecting clinically relevant associations.
The results of the current study relate to routine clinical MRI with patients lying in the
supine position. Imaging patients in the supine position is also a limitation, because the
symptoms may worsen in the upright position, and the upright position may also alter the
anatomy of the neural canal. Accordingly, an upright position would be the most appropriate
image acquisition position to link image findings to the patient’s symptoms [13, 35]. Hiwatashi
et al. found in their study that axial loading with imaging can even influence treatment
decisions [36].
The incidence of lumbar spinal stenosis is increasing due to the aging of population [12].
This also increase the number of LSS operations. However, the selection of patients for surgical
treatment still remains challenging. Our results strengthen the classical conception that the
diagnosis of this syndrome depends on the clinical history and radiographic evidence of a
demonstrable stenosis [3, 4]. This study shows that pre-operative lumbar spine MRI imaging
can predict the two-year clinical outcome in LSS surgery patients. The results of our study can
be used to improve patient information and selection of patients for surgery.
8.5
CONCLUSIONS
Routine preoperative lumbar spine MRI can predict the two-year clinical outcome in LSS
surgery. Severe central stenosis, compared with moderate stenosis, predicted better
postoperative satisfaction and less pain. One-level stenosis, compared to patients who had two
or more stenotic levels, predicted less low back pain. Preoperative scoliosis may indicate a
worse functional outcome.
63
Figure 10. Visual analogue pain (mean ± SD) on two-year follow-up in patients with moderate
and severe central spinal stenosis in visual analysis of lumbar spine magnetic resonance images.
36/48 (43/57)
54 (64)
17 (20)
12 (14)
63 (11.0)
29.6 (4.0)
5.2 (3.0)
10.4 (6.1)
44.8 (16.1)
32.8 (24.5)
4.1 (2.6)
6.4 (2.6)
551 (446)
Male/Female
Marital status married or co-habiting
Current smoker
Previous lumbar operation
Age
BMI (kg/m²)
Number of somatic diseases
BDI score
ODI
VAS overall
NRS LBP
NRS LP on walking
Walking distance (m)
729 (384)
3.2 (2.7)
1.9 (2.3)
12.6 (17.7)
27.1 (19.8)
7.6 (5.7)
2-year post-operative
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
P-value
BDI = Beck Depression Inventory (0–63)
P-values: Paired T-test was used. ODI = Oswestry Disability Index scale (0–100), VAS overall = Visual analogue pain scale (0–100), VAS LBP = specific back pain scale (0–10), VAS LP = specific leg pain scale (0–10),
Note: Except where indicated, the data are numbers of patients, with percentages or means ± standard deviations in parentheses.
Preoperative phase
Phase
Table 9. Clinical characteristics of the study subjects (n = 84)
64
65
9. General discussion
9.1 ROLE OF THE RETROSPECTIVE OUTCOME SCALE
Selection of patients for surgical treatment of LSS remains challenging, as does the evaluation of
the efficacy of surgical treatment. Defining the outcome with different outcome measures for
surgical and non-surgical treatment requires clarification. To the best of our knowledge, there
are no previous studies validating the retrospective evaluation of surgical outcomes for LSS
patients. A retrospective outcome scale is useful when studying large cohorts of patients and
comparing prospective registries with previous clinical results.
Our results show that the outcome of surgery can be evaluated retrospectively. Accuracy
is highest in patients with poor and good surgical results. Both the intra- and the interrater
reproducibility of retrospective assessments were acceptable. The moderate outcome was the
most challenging to determine accurately, and its usefulness for retrospective evaluation could
be questioned. For this PhD thesis, we retrospectively analysed Kuopio University Hospital LSS
decompression and disk herniation surgery data from 2003 until 2007. Surgery outcomes were
evaluated using the retrospective outcome scale. According to our retrospective outcome scale,
LSS and disk herniation surgery patients had good surgical outcomes in 79% of cases, which is
comparable with previously published results.
9.2
IMPACT OF PREOPERATIVE MRI IN CENTRAL LSS PATIENTS
The main finding of our study was that there is no linear correlation in the radiological degree
of the severity of central stenosis and preoperative clinical findings. In contrast, for visually
evaluated central canal LSS patients, leg pain measured by VAS was higher in the moderate
stenosis group than in the severe stenosis group. Additionally, walking distance was
unexpectedly shorter in the patients with visually evaluated moderate stenosis compared to the
patients with severe stenosis. We did not find any correlation between objective quantitative
radiological findings and patient symptoms, which also supports this paradoxical visual
finding. However, this may be attributed to patient selection for surgery because patients with
fewer symptoms and moderate radiological stenosis only may continue in conservative
treatment. In contrast, severe radiological stenosis might be treated more aggressively even
with milder clinical symptoms. Furthermore, patients with moderate radiological finding may
have concomitant/other causes of severe symptoms and thus a lower probability of benefitting
from surgery. Overall, the present study adds to the current knowledge by showing that there is
no straightforward association between stenosis of the dural sac and patient symptoms or
functional capacity. This finding indicates that dural sac stenosis is not the only key in the
pathophysiology of LSS. Additionally, it is not justified to select patients for surgery based
66
solely on the degree of central stenosis. Patients cannot be treated based on radiological
imaging pictures alone; assessment of patient symptoms are crucial when surgical treatment
decision are being made.
9.3
IMPACT OF PREOPERATIVE MRI AND EMG IN LATERAL SPINAL
STENOSIS PATIENTS
This study suggests that there are associations between MRI-assessed LLSCS and abnormal
EMG. EMG findings were also associated with patient symptoms. However, the severity of
LLSCS measured from MRI data did not correlate with the clinical symptoms, which suggests
that EMG could be more sensitive than MRI for the detection of symptomatic LLSCS. Future
studies with a larger patient sample may confirm the role of EMG in the diagnosis of LLSCS.
Nerve root-level specific study of patient symptoms would also be needed.
9.4
IMPACT OF PREOPERATIVE MRI FOR SURGICAL OUTCOME IN LSS
PATIENTS
This study showed that preoperative severe central stenosis predicted lower LP, LBP, and VAS
postoperatively when compared to patients with moderate central stenosis. Moreover, severe
stenosis predicted higher postoperative satisfaction. Preoperative scoliosis predicted an
impaired outcome in the ODI and a reduced walking distance during the treadmill test. The
preoperative finding of only one stenotic level in visual assessment predicted less postoperative
LBP when compared with patients having two or more stenotic levels. No significant
differences were detected between quantitative measurements and patient outcomes.
Studies on visually analysed spinal canal stenosis of the whole lumbar spine are rare. In
our study, we found a clear correlation between visually assessed central spinal canal stenosis
and patient outcomes, but no correlation in quantitative preoperative measurements. How can
this discrepancy be explained? The amount of neural tissue at the L1–L2 and L2–L3 levels is
significantly greater than at the L4–L5 or presacral levels. Thus, by measuring only the DSCA,
subjects with reduced space for neural tissue may not be correctly identified. According to our
findings, quantitative evaluation with the used methods cannot replace visual interpretation
performed by an experienced radiologist or surgeon. Current studies also favour visual
evaluation of radiological LSS diagnoses (38, 39). This study shows that preoperative lumbar
spine MRI imaging can predict the two-year clinical outcome in LSS surgery patients.
67
10.
Conclusions
A general conclusion of this study was that preoperative MRI findings do not correlate in a
straightforward manner to preoperative symptoms. However, preoperative MRI imaging can
predict the two-year clinical outcome in LSS surgery patients. Therefore, these study results also
favour visual evaluation of MRI imaging.
I
Our results show that the outcome of LSS surgery can be evaluated retrospectively and Kuopio
University Hospital LSS surgery patients have good surgical outcomes in 79% of cases
according our retrospective outcome scale.
II
Our study did not find any straightforward association between preoperative radiological
stenosis severity using MRI and patient symptoms in central LSS patients.
III
Our study indicated that lateral stenosis patients’ preoperative EMG findings correlate with
clinical symptoms and MRI findings; however, no significant correlations between MRI
findings and clinical symptoms or walking capacity were found.
IV
Our study indicates that preoperative lumbar spine MRI can predict the patient outcome at the
two-year follow-up in patients with LSS surgery. Visually evaluated severe central stenosis and
one-level central stenosis were found to be predictors of good outcome. A preoperative finding
of scoliosis may indicate worse functional ability.
68
69
11.
1.
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Pekka Kuittinen
Lumbar spinal stenosis
surgical treatment
Lumbar spinal stenosis (LSS) is
Correlation of radiological severity to patient’s
the most common indication for
symptoms and outcome
lumbar spinal surgery in people
aged over 65 years. The main aim
of this study was to assess the
correlation of preoperative MRI
findings with clinical symptoms
and electromyography (EMG)
findings. Our results suggest that
preoperative MRI findings of patients
with central stenosis do not have
a straightforward correlation with
preoperative symptoms, but that the
MRI findings of patients with lateral
stenosis may explain the symptoms
in some patients. Preoperative
MRI has value in the assessment of
surgical outcome before LSS surgery.
Publications of the University of Eastern Finland
Dissertations in Health Sciences
isbn 978-952-61-1842-0