1. science
2. medicine
3. surgery

MARCH / APRIL 2014
70
a new w ay of thinking about ever y d ay lif e
in medic ine and in t h e c lin ic
STIMULI FROM ORTHOPAEDICS AND THE PROFESSIONAL FIELD – FOR PHYSICIANS, SPECIALISTS AND EXECUTIVES
Interview with Professor Karl Stoffel
“Implanting an optimys® is
like travelling by train”
Focus on science
A soft material with
exceptional hardness
From the professional field
Swarm intelligence
How to utilise
collective intelligence
for strategic decisions
2
INTER
VIEW
“Implanting an optimys® is
like travelling
During the primary implantation of a femoral prosthesis, short stems that take into account
the patients anatomy are preferred. We asked Professor Karl Stoffel why he chose optimys,
and what matters when it comes to planning surgery.
Professor Stoffel, what prompted you to
start using the optimys stem in Australia?
Professor Karl Stoffel
Swiss-born Professor Stoffel has been
working as a Professor of Orthopaedic
Surgery at the University of Western
Australia in Perth since 2002 until today.
From 2008 until 2011 he retuned to
Switzerland as the Head of Department
at the canton hospital in Chur. The
46-year-old Professor has published
numerous articles in peer reviewed journals and has won numerous awards for
his research in the field of biomechanics
and joint arthroplasty.
E-mail: [email protected]
Six years ago, I started using a short stem in
young patients when I was working in Switzerland. My aim was primarily to preserve
bone in the proximal femur, reduce stress
shielding and avoid damaging the muscles
around the greater trochanter during the implantation procedure. As the short stem I had
been using in Switzerland wasn’t available in
Australia, I made some enquiries. I needed a
short stem with proximal metaphyseal anchoring that allowed me to continue my minimally
invasive approach to preserve bone and protect muscle. optimys was the stem that most
closely resembled the stem I had been using
previously, and it also had documented excellent short-term results. Furthermore, Mathys
has a good reputation in Australia, as well as a
great customer service.
allow yourself to be guided by the calcar and
you plan the resection height, stem size and
offset version correctly before the operation,
everyone should arrive at the planned, correct
final destination.
What design features do you like most
about the optimys?
The entire package impresses me. It includes,
for example, the simple set of tools for MIS ac-
“optimys was the stem that most
closely resembled the stem I had
been using previously and it also had
documented short-term results that
were excellent.”
What do you think is the advantage of optimys compared to other hip stems?
I believe that its biggest advantage lies in the
fact that the centre of rotation, the femoral
offset and the leg length can be reconstructed
in virtually every patient. With most stem
systems, the offset increases with the implant
size. This means that, where there is a narrow
proximal medullary canal, the stem is medialised, leading to a limp and the risk of dislocation. optimys pursues a different philosophy:
Its positioning by the calcar, making the reconstruction of the patient’s individual anatomy
easier. Implanting an optimys, you could almost imagine, is like travelling by train: if you
cess, as well as the curved stem design with the
flattened shoulder and trapezoidal intersection.
This feature has already become established
in uncemented stems and has shown that it is
possible to achieve very good primary stability.
What was the biggest challenge for you in
terms of switching to optimys?
Since I was already familiar with the anterolateral MIS approach, and had been using a
FOR
YOUR USE
Surgical risk
calculator
by train“
similar short stem for many years, I found the
switch relatively straightforward. Planning,
however, is different: because the stem is
guided by the calcar therefore standardised
x-ray images are essential. Often, patients
have limited internal rotation and the femur
remains in a slightly externally rotated position. This reduces the offset and increases
the CCD angle. I’ve also learned to integrate
lateral x-ray images into my planning as well,
to be able to determine the anteversion.
So pre-operative planning is an essential
stage?
Absolutely. Not just to ensure that the procedure is carried out efficiently and precisely,
but also to anticipate any potential intraoperative complications. The aim of planning
using a standardised x-ray image
is to determine the leg length
and the femoral offset. During
the operation, I measure the distance from the lesser trochanter
to the resection height and –
once the stem has been inserted
– the distance to the end of the
neck. Sizing the stem correctly is
crucial for guaranteeing primary
stability and avoiding the risk
of under-sizing the implant. As
soon as I deviate from my plan
by two sizes, I use an image
intensifier (C-arm) during the
operation to assess the situation.
What’s your view on using the
Adam’s arch as the “guiding
rail”?
Generally speaking, the shape
and offset of the implant is defined by the anatomy of the calcar. There is a close relationship here between
the CCD angle and the centre of rotation. If
a stem can be implanted so that the calcar is
used as the guide, this is definitely the most accurate way of restoring the patient’s anatomy.
The triple-cone stem geometry of the optimys has been proven to guarantee good
primary stability.1 With the CaP coating,
the time between primary and secondary
stability is reduced. Do you believe that
3
on the net
these product characteristics are crucial for
good stability, or are they just gimmicks?
Of course, the triple taper is vital for primary
stability, and the CaP coating will encourage
the growth of bone onto the stem. However
we shouldn’t forget that every stem sinks and
runs the risk of failure if it is under-dimensioned. There’s a learning curve when it comes
to implanting short stems. To begin with, there
is a tendency to choose a stem that is too
small. During the planning stage, the stem size
should be chosen so that the lateral surface
of the prosthesis extends to the lateral cortex.
Researchers at the American College
of Surgeons (ACS) have developed an
online surgical risk calculator that allows
patient-specific post-operative complications to be predicted for 1,500 different
types of operation. Information was
taken from over 1.4 million patients in
around 400 American hospitals, analysed and used as the basis for the calculator.1
“If a stem can be implanted so that
the calcar is used as the guide, this is
definitely the most accurate way of
restoring the patient’s anatomy.”
What would you advise colleagues wanting to start using the optimys?
I would advise them to attend a workshop in
which an experienced trainer teaches them
how the implant works and how to insert it
correctly. I also recommend first assisting someone who is experienced in using the optimys or
asking them to assist during the first few procedures. Additionally, it is helpful to use x-ray
monitoring during the operation. Anyone using
an implant for the first time should not change
their approach at the same time. A final piece
of advice is to choose the right patient, because
even the best implant can fail if the patient is
unsuitable.
Professor Stoffel, thank you for talking to
us today.
The calculator allows surgeons to enter
up to 22 of a patient’s pre-operative
risk factors. Using this information, the
patient’s risk of mortality, the overall
complication rate, the rate of severe
complications and the risks of lung inflammation, heart problems, infections
etc. are calculated and set against an
“average patient risk”. An estimate of
the duration of the patient’s hospital stay
is also provided.
The risks are set out clearly in percentages and in the form of bar charts. The
results can be printed out in PDF format
and sent digitally. The risk calculator is
free to use and is available to doctors
and patients free of charge in English at:
www.riskcalculator.facs.org.
1
Bieger R. et al Biomechanics of a short stem: In
vitro primary stability and stress shielding of a conservative cementless hip stem. J Orthop Res. 2013
Aug;31(8):1180-6.
1
Bilimoria KY, et al. Development and evaluation of the universal ACS NSQIP surgical
risk calculator: A decision aid and informed
consent tool for patients and surgeons. J Am
Coll Surg. 2013;217(5):833-42
FOCUS ON
SCIENCE
4
vitamys®
A soft material with exceptional
By Dr Reto Lerf, Mathys Ltd Bettlach
The hip simulator realistically simulates the long-term stresses that affect
the joint in the body. The implant material vitamys exhibits no increased wear,
even under exaggerated test conditions.
In terms of wear resistance, the demands on
implants and the materials used for them are
growing. So it was an important goal in the
development of the highly cross-linked, vitamin E-stabilised polyethylene used in vitamys
to reduce wear. When it comes to replacing
hip joints, less wear means a lower revision
rate, as the Australian National Joint Replacement Registry of 2013 confirms. The longer
the implant remains in situ, the higher the
difference in the revision rate of highly crosslinked PE compared to conventional (non
cross-linked) PE (Fig. 1).
For vitamys, hip simulator studies were used
to demonstrate a seven-fold reduction in the
in vitro wear.1 The test protocol, consistent
with the ISO 14242 standard, is based on the
assumptions that a factory-new acetabular cup
will be positioned at the optimum angle and
the patient will load it with normal walking.
But what happens if not all of these conditions
28%
are perfectly met? What if the cup has been
inserted at too steep an angle, or what may
happen to the material of a cup after several
years of implantation? To get answers to these
questions, hip simulator studies were carried
out under exaggerated test conditions.
Hip simulator study
with aged polyethylene
Another goal in the development of vitamys
was to increase its resistance to ageing.3 One
way of simulating the ageing process in the
laboratory was to increase the storage temperature. With UHMW-PE, the samples are
stored at 70° C and – to exaggerate the conditions – under 5 bar of oxygen. The ASTM
F2003 standard specifies a duration of 15
days, which is equivalent to around 10 years
in vivo.4 For vitamys, the ageing period was
extended to 60 days, simulating around 40
years of implantation. The wear rate in the
hip simulator remained virtually unchanged
Dr Reto Lerf
Head of Polymer Development
Mathys Ltd Bettlach
at 5.9 mg / million cycles versus 5.8 mg / million cycles in the un-aged condition. With
conventional PE, the wear rate rose from
29 mg / million cycles, un-aged, to 45 mg / million cycles after 15 days of ageing (Fig. 2).
50
45
24%
40
20%
35
30
16%
Non Cross-Linked
25
Cross-Linked
12%
20
15
8%
10
4%
5
0%
0
0
2
4
6
8
10
12
Years Since Primary Procedure
Fig. 1: Cumulative revision rate for total hip
endoprostheses, comparison between highly
cross-linked and non cross-linked polyethylene.2
UHMW-PE
UHMW-PE
aged 15 d
vitamys
vitamys
aged 60 d
Fig. 2: Hip simulator wear rates for conventional UHMW-PE and vitamys, aged and un-aged,
15 days for UHMW-PE, 60 days for vitamys.
Fig. 3: vitamys inlays after 5 million cycles in the
hip simulator. With a normal installation angle,
corresponding to 45° of inclination, the contact
surface with the head covers around 2/3 of the
joint surface, but with an 80° inclination this
contact surface is only represented by a narrow
area at the upper edge.
PRODUCT
IN FOCUS
hardness
Hip simulator study
with steep cup position
In standard hip simulator tests, the cup and
head are arranged so that they correspond
to an in vivo angle of inclination of 45°. To
simulate a cup that is implanted at a very
steep angle, an installation angle was selected
that corresponds to an inclination of 80°. 5
At first glance, the results are surprising.
With conventional UHMW-PE, the wear rate
was 24 mg / million cycles, less than with the
normal angle of inclination (29 mg / million
cycles). A look at the inlays after the test over
5 million cycles (Fig. 3) explains why: the steep
angle of inclination leads to the wear being
concentrated in an area on the caudal edge
of the cup. The contact surface with the head
is smaller, and as a result so is the amount of
wear. With vitamys, the reduction in the wear
rate with a steep inclination is barely measurable: 5.4 mg / million cycles compared with
5.8 mg / million cycles.
A material that forgives mistakes
Under standard test conditions, vitamys exhibits excellent wear results. The low wear
values persist in an extremely aged condition,
and with a very steep inclination. Even under
unfavourable clinical conditions, vitamys can
be expected to yield good results.
Sources
5
Ligamys® – Healing
of torn anterior cruciate ligaments
Ligamys is an innovative implant for the surgical treatment of torn anterior
cruciate ligaments (ACL). The implant creates the optimal conditions for the
biological self-healing of the ligament.
Ligamys® is made up of two key
components:
dynamic stabilization component
(monoblock with integrated
spring system)
polyethylene thread with Button
Treatment using Ligamys involves the dynamic stabilisation of the knee joint by
means of a spring system. The polyethylene thread that lies behind the patient’s own
cruciate ligament is fixed to the femur by a button and is connected to the spring
system in the proximal tibia. This provides the healing cruciate ligament with the rest
it needs for the two stumps to come together and heal well. With Ligamys, there is
no longer a need to harvest graft tendon tissue, thus avoiding an additional surgical
procedure that would weaken the knee joint considerably.
Promoting self-healing
To promote the ruptured ligament’s self-healing, the inferior cruciate ligament
stump is wrapped with PDS threads and anatomically repositioned. Microfracturing
is also used to promote regeneration of the ligament: this process involves perforating the femur in the area of the ACL insertion with a reamer so that stem cells can
escape and accelerate ligament healing.
1
Beck M et al. Oxidation prevention with vitamin
E in a HXLPE isoelastic monoblock pressfit cup.
Preliminary results in: Knahr K (Ed.) EFORT 2011
Tribology Book, Springer, Berlin 2012.
2
Australian Orthopaedic Association National
Joint Replacement Registry. Annual Report 2013,
Figure HT 26. Available from URL: https://aoanjrr.
dmac.adelaide.edu.au/annual-reports-2013.
Since the Ligamys implant is not a fixed point-to-point connection, unloading of the
healing ACL through the knee joint’s entire range of movement is guaranteed. The
spring mechanism therefore markedly promotes biological healing of the ACL.
3
Lerf R, Zurbrügg D, Delfosse D. Use of vitamin E
to protect cross-linked UHMWPE from oxidation.
Biomaterials. 2010; 31(13):3643-8.
4
Zurbrügg D, Abt N. Comparison between in vivo
ageing, shelf and accelerated ageing of UHMWPE based on the theory of oxidation kinetics, ESB
2003, Stuttgart.
For whom is Ligamys® suitable?
In view of the fact that the self-healing abilities of the torn ligament decrease over
time, Ligamys implants must be implanted no more than 21 days following the ligament injury. In particular sporty patients may benefit from treatment using Ligamys,
which restores both the stability of the knee and proprioception.
5
Halma JJ, Señaris J, Delfosse D, et al. submitted
to J Biomed Mater Res: Part B – Applied Biomaterials.
The market launch of Ligamys is planned for the first half-year of 2014 in
selected sales territories. Information about compulsory training and opportunities to observe its use can be found at www.mathysacademy.com under “Coming
courses” and “Ligamys Day”.
6
FROM THE
PROFESSIONAL FIELD
Swarm intelligence
How to use collective intelligence
When it comes to complex disease patterns, consultations can underpin the diagnosis.
to discuss possible solutions with people they
trust outside the group.
When it comes to strategic questions, groups are often smarter than a single specialist.
To allow collective intelligence to develop to its fullest potential, four key requirements
must be in place.
A ward team that works together to develop
new ideas for managing care. A group of
clinicians at a congress that determines the
best treatment strategy via tele-voting. When
collective intelligence develops in groups, the
results are often astounding. As an example,
a group of people set the task of determining how many marbles there are in a glass on
average predicts the number more accurately
than each of the individuals on their own.
This phenomenon of group intelligence is also
seen in the “Ask the audience” option of the
TV show “Who wants to be a millionaire?”.
The audience helps in 91 % of cases, whereas
the experts called in “Phone a friend” give the
right answer in only 65 % of cases.
For strategic decisions such as expanding a
catchment area or building a centre, a variety
of information needs to be processed and possible solutions evaluated. In such cases, the
intelligence of many can be used to generate
ideas and verify strategies.1 Psychologists have
recognised that a decision made based on the
independent opinions of many group members is usually better and sounder than the
majority of the individual decisions that go into
the group decision.2
In his best-seller “The wisdom of crowds”,
business journalist James Surowiecki defines
four basic conditions for the development of
collective intelligence: 3
1. Diversity of opinion
The group should be as diverse as possible, i.e.
made up of men and women of different ages,
nationalities, educational backgrounds, with
different skill sets, mindsets and so on. This is
the only way to ensure that different perspectives lead to new and unusual solutions.
In homogeneous groups, for example of only
female staff in a department, the people
involved tend to deliberately or unconsciously
ignore information. The
consequence of this is
“group thinking”. In this
situation, the group tries
to avoid conflicts or minimise them and achieve a
consensus – but without
evaluating ideas with the
appropriate degree of
critique.
Hint: Form project-related teams of people who
are not yet used to each
other and who can inspire each other with new
ideas. Invite external experts to meetings who
will share their perspective on things. Encourage
members of the group
2. Independence
Collective decisions are only wise if the people
involved do not listen to each other too much.
As a result, group member should be able to
form their own opinions independently of their
superiors and colleagues. Different personal
views and opinions need to be tolerated and
encouraged.
Strong hierarchies in a group can skew the
result. The opinion of a superior is given higher
status. If the group cohesion is very high or if
the group exerts pressure on people who think
differently, an undesirable “herd instinct” can
develop.
Hint: Form teams that are independent of
each other that will work on the same question. As a manager, keep your own opinion to
yourself when you are setting the group tasks.
At every meeting, assign the role of devil’s advocate to a different group member.
3.Decentralisation
The decentralised knowledge of many forms
the resource of collective intelligence. Everyone is an expert in his own field and assesses
a problem based on their own personal knowledge: A controller may tackle the question
of whether the hospital should broaden the
number of conditions it treats differently to a
theatre nurse, for example. Individuals’ specialisations increase the spectrum of knowledge
and experience within the group.
Often, individuals hold valuable information
that is not accessible to everyone. A decentralised system therefore needs resources and
incentives to share that information and to
facilitate networking with experts and supposed non-experts.
Hint: Every employee should be at liberty to
specialise, procure information and if necessary
cooperate with others. Suitable incentives, such
as a ranking list of the most accurate forecasts or
small prizes can motivate participants to offer as
precise a forecast as possible.
4.Aggregation
In ideal cases, the individual responses can be
SEND FOR
YOUR FREE COPY
Collective intelligence
for strategic decisions
in everyday hospital situations
Book
recommendations
Abrahamson S, Ryder P, Unterberg B. Crowdstorm: The Future of Innovation, Ideas, and
Problem Solving. Wiley; 1. ed. 2013
Howe J. Crowdsourcing: Why the Power of
the Crowd Is Driving the Future of Business.
Crown Business; 2009
Surowiecki J. The wisdom of crowds. Why
the many are smarter than the few and how
collective wisdom shapes business, economies,
societies and nations.
Anchor; Trade Paperback; 2005
brought together using a suitable algorithm
to form a single, common opinion. Already
decades ago, it was possible by using a simple
statistical formula to predict a diagnosis of
neurosis or psychosis. The assessment of a
group of 29 inexperienced and experienced
psychiatrists was more reliable than that of
the best of the participating neurologists.4
Ideally, opinions and predictions should be
documented in the form of figures (e.g. development of future theatre numbers, patient
numbers, etc.). This procedure, known as
“social forecasting”, is already being used
successfully by major companies.
Hint: Form an average from several opinions
and forecasts! This generally leads to a higher
degree of accuracy than the use of specialists’
individual opinions and analyses.
7
Find out what form of leadership is best for making use of collective intelligence in everyday hospital situations. We give you some
unusual examples of swarm intelligence and show you where it can
be used and what its limits are. The best collective decisions do not
come from consensus and compromise, but rather from a diversity
of perspectives on the question in hand. Learn to ask the ‘right’
questions.
You can easily obtain your personal copy with practical hints and
suggestions
Using the attached fax reply form:
+41 32 644 1 161
Or via e-mail:
[email protected]
Psychological background
for group intelligence
One study that was published in the highly
respected journal “Science”, attempted to
determine the nature of collective intelligence
– with astonishing results.5 Adults who had
had their intelligent quotas (IQ) determined
previously were randomised into various
groups that were set the tasks of brainstorming, decision-making and solving complex
tasks. Despite expectations, a high IQ of all
the group members had only a slight effect
on the collective intelligence. Group cohesion, motivation and satisfaction were also
of barely any significance. One crucial factor
was the number of women in the team. The
authors explained this unusual result by the
higher social sensitivity of women. They are
able to perceive the emotions of others and
recognise them correctly.
Masthead
Publisher:
Mathys Ltd Bettlach • Robert Mathys Strasse 5 • 2544 Bettlach • Switzerland
Telephone No.: +41 32 644 1 485 • E-Mail: [email protected]
Editor responsible for the magazine:
Tanja Rölli • Head of Market Communcation • Mathys Ltd Bettlach
To use the knowledge of many for strategic decisions, it is essential to ensure that the group
is made up of the right individuals. Facilitating
networking and retreating as a manager creates good conditions for collective intelligence
to flourish.
Leimeister JM. Kollektive Intelligenz. In: Wirtschaftsinformatik. Gabler Verlag 2010; 4(52):239-42.
Yi, SKM, Steyvers M, Lee MD, Dry MJ. The wisdom
of the crowd in combinatorial problems. Cognitive
Science. 2012; 36(3):1-19.
3
James Surowiecki. The wisdom of crowds. Anchor;
New ed. Trade Paperback. 2005.
4
Goldberg LR. Simple models or simple processes?
Some research on clinical judgements. Am Psychol.
1968;23:483-96.
5
Woolley AW, Chabris CF, Pentland A, et al. Evidence
for a collective intelligence factor in the performance
of human groups. Science. 2010;330(6004):686-8.
1
2
move! is published by Mathys Ltd Bettlach –
your competent partner for total arthroplasty.
With new, useful information, move! is addressed to specialists in orthopaedics and
traumatology in hospitals and practices, as
well as all specialist and management staff in
the medical field, nursing staff and general
management in hospitals. We would like to
thank all of those who have helped us in real-
ising the publication of move! by making
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97.3
%
Works even better!
97.3 % survival at 13 years. [1,2] The balanSys cruciate retaining knee system
has an excellent survival rate. The probability of having NO revision within
the first 13 years after surgery is 97.3 %.
[1]
10 years results of the tension controlled, ligament balanced TKA. Klenk JS, Christen B, Eijer H,
Schuster AJ; SGOT Congress, Lausanne, 26 – 28
June 2013
[2]
Long-term results of a tension controlled ligament balanced total knee arthroplasty. Klenk
JS, Christen B, Eijer H, Schuster AJ; White Paper,
Mathys Ltd Bettlach, 2013
Mathys Ltd Bettlach • Robert Mathys Strasse 5 • P.O. Box • 2544 Bettlach • Switzerland • www.mathysmedical.com
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