1. health and fitness
2. disease
3. arthritis

Volume 4 Issue 6
November 2010
VNA Roadshow 2009
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In this e-mag...
Dog hip dysplasia:
causes, diagnosis
and treatment
Graham Hayes looks at how this condition
manifests itself in young and old patients,
and the breeds and types of dog predisposed
to the condition
Role of monitoring in
care of elderly cats
Sarah M A Caney discusses the importance of
regular health checks to detect early signs of
disease, and the role of nurse clinics
(Please click their names for an in-depth biography)
hip dysplasia
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Dog hip dysplasia: causes,
diagnosis and treatment
Graham Hayes MA, VetMB, CertSAS, MRCVS
looks at how this condition manifests itself in
young and old patients, and the breeds and
types of dog predisposed to the condition
H
ip dysplasia is a common
developmental disorder of
the hip joint characterised
by pain and laxity, which leads to
progressive osteoarthritis (OA).
During early postnatal development,
the hip joint fails to develop
normally and there is a loss of
congruency between the articular
surfaces of the acetabulum and
femoral head, with stretching of the
teres ligament and joint capsule.
This abnormal development leads
to hip joint laxity and the femoral
head subluxates during normal
activity.
If you consider a normal hip joint
to be a smooth, spherical snooker
ball sitting in a deep cup, then a
severely dysplastic hip could be
considered as a flattened mushroom
sitting in a shallow saucer. As the
dog runs around, the mushroomshaped femoral head bangs about
in the shallow acetabulum, causing
microfractures on the articular
surface. This causes further stretching
and tearing of the soft tissues and
pain. Damage to the articular cartilage
and joint capsule inflammation trigger
OA in the joint.
In the short term this has some
benefits, as fibrotic thickening of
the joint capsule reduces laxity in
the hip joint and the clinical signs of
hip pain diminish. However, as OA
progresses over several years, new
bone deposited around the joint leads
to a reduced range of movement,
and loss of articular cartilage causes
Click to see Graham’s Biography
Figure 1 (left). Ventrodorsal extended radiograph of a 15-month-old
Labrador retriever with severe bilateral hip dysplasia. Both hips are
subluxated, neither femoral head is within the acetabulum and there is
new bone around both femoral heads and acetabulae. Figure 2 (right).
Ventrodorsal extended radiograph of a five-year-old GSD with hip
osteoarthritis secondary to hip dysplasia. The right hip is moderately
affected, the left hip is severely affected. There are osteophytes
(new bone) all around the left femoral head and acetabulum
VNTCPD l Volume 4
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hip dysplasia
exposure of subchondral bone, both
of which lead to the return of hip pain
and a gradual loss of function. This
is exacerbated by obesity and loss of
muscle mass.
A spectrum of disease exists, from
mildly affected dogs with minor hip
dysplasia and no clinical signs to
those with completely dislocated hips
(Figure 1). The disease typically has a
biphasic age distribution:
●● young dogs (four to 18 months of
age) with hip pain resulting from hip
laxity; and
●● older dogs (two to 12 years) with hip
pain from hip OA (Figure 2).
Clinical signs
Clinical signs include a unilateral
or bilateral pelvic limb lameness,
reluctance to exercise, slowness to
rise, an inability to jump into the car
or go up steps, poorly developed
hindlimb muscles with weight shifted
on to the forelimbs, an abnormal
gait with flexion of the spine to limit
movement of the hips and “bunnyhopping”. It is not uncommon to
have an individual dog presented for
treatment when it is young and then
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much older, having had several years
of pain-free hip function due to this
biphasic age distribution of clinical
signs.
Causes
Hip dysplasia is inherited as
a polygenic trait, but disease
development is thought to be
influenced by environmental factors
such as growth rates, nutrition,
exercise and muscle mass. Dogs
with hip dysplasia commonly suffer
with other joint problems such as
elbow dysplasia. The condition is
perpetuated by inbreeding and is
significant in certain breeds with
a restricted genepool, such as the
Clumber spaniel.
Affected animals are thought to
be normal at birth with abnormal
development starting in the first
few months of life. Uncertainty
exists about whether the abnormal
bone growth leads to the laxity or
vice-versa. Clinical disease is most
frequently encountered in medium
and larger breeds, although it is a
common incidental finding in smaller
breeds, such as bulldogs and pugs.
Estimates from the USA suggest
8.5 per cent of golden retrievers,
10 per cent of GSDs, 10 per cent of
Rottweilers and 15 per cent of St
Bernards have clinical hip dysplasia
(Witsberger et al, 2008).
Figure 3. A sedated dog correctly positioned for ventrodorsal extended
radiographs. Notice the use of a trough, tapes on both hindlimbs and a
tape to prevent external rotation of the stifles. Ilial wings, ischial tubers
and greater trochanters should be palpated to ensure the pelvis is not
rotated
Diagnosis
Diagnosis is made in young dogs
by localising pain to the hip,
demonstrating hip joint laxity and by
radiography. Affected dogs often have
poorly developed hindlimb muscles,
prominent greater trochanters, and
pain is elicited on manipulation of
the hips (especially on extension
and circumduction). Subluxation
or clunking of the hips may be
observed during examination. Under
sedation, passive hip joint laxity
can be subjectively assessed in
young dogs using either the Ortolani
test or Barden’s hip lift test, which
assess passive laxity in the joint.
Radiography usually demonstrates
primary conformational abnormalities
and secondary degenerative changes
(arthritis), which can often be seen
from five months of age. In the UK,
ventrodorsal extended radiographs
are usually taken (Figure 3); however,
extending the hip may underestimate
laxity by spiral tensioning of the joint
capsule. Distraction radiographs
(called the PennHip method; Smith,
1997) are around 2.5 times more
sensitive at demonstrating laxity than
ventrodorsal extended radiographs,
but require manual restraint and so
VNTCPD l Volume 4
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hip dysplasia
are not permitted under the UK’s
ionising radiation regulations.
Differential diagnoses for hindlimb
lameness in young dogs include
panosteitis, Legg-Calvé-Perthes
disease, stifle problems (cruciate
disease, patella luxation and
osteochondritis dissecans) and hock
problems (osteochondritis dissecans).
Differential diagnoses for hip pain in
older dogs include cruciate disease,
lumbosacral disorders, hip joint sepsis
and proximal femoral bone neoplasia.
Treatment
Many mild cases and those where
hip dysplasia is an incidental finding
do not require treatment (see
Table 1). Most dogs can be treated
conservatively, with the majority
improving by 12 to 18 months of
age. Conservative treatment should
involve the judicious use of NSAIDs,
moderate exercise restriction, weight
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control and nutraceuticals. Activity
is important for these animals, but
heavy or high-impact exercise with
frequent over-exertion exacerbates
the clinical signs so dogs are best
restricted to leash exercise. The
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muscles around the hip are extremely
important active stabilisers of the
joint. Building muscle to support
the hip using physiotherapy or
hydrotherapy is very effective at
improving joint stability. The benefits
of weight control are often undersold,
but a prospective study following
48 Labradors throughout their lives
showed that the dogs fed ad-lib
had significantly worse clinical signs
and progression of hip arthritis
than those fed on restricted rations
and kept lean (Smith et al, 2006). In
addition, the restricted dogs in this
study lived on average nearly two
years longer than those fed ad-lib.
Nutraceuticals (primarily chondroitin
and glucosamine) have recently been
proven to have some beneficial effects
in slowing progression of arthritis and
improving joint function, and should
be recommended.
Up to three-quarters of hip dysplasia
cases will improve with conservative
treatment, and all cases are treated
this way initially; however, severely
affected dogs have a more guarded
prognosis (Farrel et al, 2007) for which
surgical solutions can be considered,
as follows.
●● Triple-pelvic osteotomy (TPO) aims
to improve hip joint biomechanics
by improving dorsal coverage of the
femoral head. The surgery involves
three osteotomies (pubis, ischium
and ilial body) to free the acetabular
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Figure 4 (right). Ventrodorsal extended radiograph of a seven-monthold golden retriever with bilateral hip dysplasia. Both hips are
subluxated with only about a quarter of the femoral head within the
acetabulum. Figure 5 (far right). Ventrodorsal extended radiograph of
the dog in Figure 4 after a unilateral TPO. Notice the three osteotomies
and rotation of the left acetabular fragment to improve congruency of
the left hip joint. Inset: a TPO plate
fragment, which is then rotated
(normally by 20°) to improve joint
congruency by increasing joint surface
area. The weight-bearing axis is
restored using a TPO-plate to repair
the ilial osteotomy while maintaining
the rotation. While bilateral
simultaneous surgeries are possible,
most surgeons prefer to stage
bilateral procedures by four to six
weeks. Suitable candidates for a TPO
are young dogs (less than 10 months)
with clinical signs of hip dysplasia
confirmed by radiography, but with no
secondary arthritic changes (Figures
4 and 5). TPO is a mildly controversial
procedure as some argue that the
criteria defining a suitable candidate
VNTCPD l Volume 4
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hip dysplasia
would select for patients that would
do well with conservative treatment.
●● Femoral head and neck excision
(FHNE) aims to remove the painful,
dysplastic hip joint and allow the
formation of a pseudoarthrosis
or false joint. FHNE is a salvage
procedure for an intractably painful
joint. The pseudoarthrosis formed
is usually more functional than the
dysplastic, painful joint it replaces,
although range of motion is often
still decreased. FHNE has been used
successfully for small dogs and cats,
and is used with more caution in
larger dogs (more than 15kg to 20kg).
The procedure’s success is improved
by early mobilisation and good
physiotherapy in the first few weeks
postsurgery, to maintain and build
muscle around the hip. The function
after FHNE is usually acceptable, but is
inferior to the function achieved after
total hip replacement.
●● Juvenile pubic symphysiodesis (JPS)
is a prophylactic treatment to change
the growth pattern of the pelvic bones
to improve hip joint congruency. The
surgery involves electrocauterising the
pubic symphysis, leading to premature
closure of this growth plate and,
subsequently, bilateral rotation of both
acetabular rims to improve coverage
of the femoral heads. The end result is
similar to performing a bilateral TPO,
but relies on growth of the pelvis to
gradually achieve the rotation. This
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surgery is easily performed, with
results comparable to TPO, but must
be performed in dogs less than 18-22
weeks of age to be effective (Bernarde,
2010). This is often before many dogs
show clinical signs of hip dysplasia, so
almost has to be used prophylactically
in patients at high risk of developing
hip dysplasia and demonstrable hip
laxity. An additional controversy of JPS
is that improving the phenotype does
not alter the genotype and dogs that
have undergone JPS must not be bred
from and are usually early-neutered at
the time of JPS.
●● Hip denervation is a palliative
treatment involving transection of the
nerves that innervate the hip joint
capsule. Although the procedure
probably does not affect disease
progression and may only provide
temporary relief, it is a relatively
simple surgery with a short recovery
period and is analgesic to the young
dog with hip pain. It is popular in
parts of Europe.
●● Total hip replacement (THR) is
the salvage procedure of choice
for intractably painful hips; in most
cases the functional outcome is good
to excellent and improvement is
maintained, resulting in a dramatically
improved quality of life for the dog.
Initial cost, while considerable, is often
offset by eliminating the need for lifelong palliative medications. The aim of
THR is to remove the painful, poorly
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functioning hip and replace it with a
pain-free, fully-functional prosthetic
joint. Until recently, THR was restricted
to dogs above 20kg, but implants
are now available to allow it to be
performed on skeletally mature dogs
(more than six to eight months) of any
size. The surgery can be performed as
a treatment for hip dysplasia in young
dogs or as a treatment for hip arthritis
(following hip dysplasia) in older dogs.
Surgery has a greater than 90 per cent
success rate when performed by a
suitably experienced surgeon.
A range of THR systems is available,
but the most well-established is the
BioMedtrix CFX. This uses a stainless
steel alloy femoral implant and a
high-density polyethylene acetabular
cup, both cemented in-situ using
polymethylmethacrylate. This has
performed well and remains popular,
but concerns regarding the longevity
of implants and a trend for earlier
surgeries in humans led to the
development of cementless implants
in humans. These are designed to
integrate into the bone and may
lead to a more stable implant-bone
interface longer term. Cementless
implants may have some theoretical
advantages for use in young animals,
but this is yet to be proven, and the
short-term complication rate may be
slightly higher. A leading cementless
THR implant is the BioMedtrix BFX,
which is a “push-fit” system. The Kyon
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Table 1. Treatment options for OA
Treatment
Young dogs
with hip
dysplasia
Conservative ✓
JPS
✓ (<22 wks)
TPO
✓ (<10 mths)
Older dogs
with hip
osteoarthritis
✓
Nerve ablation ✓
FHNE
✓
THR
✓ (>6-8 mths) ✓
✓
Zurich and the Medicatech Helica hip
systems are becoming more popular,
both of which screw into the bone.
Feline hip dysplasia
Hip dysplasia occurs in cats with
a frequency of about 6.6 per cent,
but is often an incidental finding
during radiography, and often is not
associated with clinical signs (Keller et
al, 1999). The condition may be more
common in combination with medial
patella luxation or may increase the
risk of hip luxation after trauma.
Certain breeds are reported to be
over-represented.
Screening programmes
In the UK, a scheme administered by
the BVA on behalf of The Kennel Club
aims to reduce the prevalence of hip
dysplasia in dogs by discouraging
breeding from individuals with
suboptimal hip conformation. Wellpositioned ventrodorsal extended hip
VNTCPD l Volume 4
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hip dysplasia
Home
radiographs from dogs of 12 months or older are
scrutinised by the BVA panel and semi-objectively
scored according to nine criteria reflecting primary
conformational abnormalities, laxity and secondary
arthritic changes. Each hip is scored out of 53,
giving a combined total of 106, with higher scores
reflecting more serious hip dysplasia. A summary
is available on the BVA website. It is recommended
that only dogs with scores significantly below the
breed average are used for breeding.
The scheme reduced the prevalence of hip
dysplasia to some degree, but not as much as
anticipated. The main criticisms are that the
ventrodorsal extended view underestimates laxity
compared to distraction radiographic methods,
and the young screening age makes the scheme
insensitive at detecting dogs with milder grades of
hip dysplasia. A more sensitive method of screening
would theoretically lead to more rapid progress
in reducing the prevalence of hip dysplasia in our
dogs.
Smith G K, Paster E R, Powers M Y et al (2006).
Lifelong diet restriction and radiographic evidence
of osteoarthritis of the hip joint in dogs, JAVMA
229: 690-693.
Witsberger T H, Villamil J A, Schultz L G et al (2008).
Prevalence of and risk factors for hip dysplasia and
cranial cruciate ligament deficiency in dogs, JAVMA
232:1818-1824.
Selected references
Bernardé A (2010). Juvenile pubic symphysiodesis
and juvenile pubic symphysiodesis associated with
pectineus myotomy: short-term outcome in 56
dysplastic puppies, Veterinary Surgery 39: 158-164.
Farrell M, Clements D N, Mellor D et al (2007).
Retrospective evaluation of the long-term outcome
of non-surgical management of 74 dogs with
clinical hip dysplasia, Veterinary Record 160:
506-511.
Keller G G, Reed A L, Lattimer J C and Corley E A
(1999). Hip dysplasia: a feline population study,
Veterinary Radiology and Ultrasound 40: 460-464.
Smith G K (1997). Advances in diagnosing canine
hip dysplasia, JAVMA 210: 1451-1457.
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Further reading
www.bva.co.uk/canine_health_schemes/Hip_
Scheme.aspx
BSAVA Manual of Canine and Feline Musculoskeletal
Disorders (2006).
Please click here to turn to
the questions page to test your
knowledge & understanding
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VNTCPD l Volume 4
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hip dysplasia
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1
4
7
n At birth
n 1-2 months
n 6-12 months
n 5 years
n Cage rest
n Weight management
n Long walks at the weekend
n Feeding raw meaty bones
n 6-month-old Labrador with
At what age is hip
dysplasia normally
diagnosed?
YOU WERE
2
Which of the following
breeds is NOT
commonly affected by
hip dysplasia?
nRottweiler
n GSD
n Labrador retriever
n Greyhound
YOU WERE
3
Which test can be used
to evaluate hip joint
laxity in young dogs?
n Ortolani test
n Cranial drawer test
n Cranial tibial thrust test
n The ‘sit’ test
YOU WERE
Which of the following
is most important for
dogs with hip joint pain?
YOU WERE
5
Most cases of hip
dysplasia can be
treated conservatively:
n True
n False
YOU WERE
6
Triple pelvic osteotomy
may be suitable for:
n 7-month-old Labrador
with hip pain and subluxation
n 12-month-old Rottweiler
with hip pain and early arthritis
n 2-year-old St Bernard with
hip arthritis
n An overweight 12-year-old
Labrador with hip arthritis
YOU WERE
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Juvenile pubic
symphysiodesis may
be suitable for:
hip dysplasia
n 3-month-old Labrador the
owner wishes to breed from
n 3-month-old GSD with hip
dysplasia
n 10-month-old Rottweiler
with hip dysplasia
YOU WERE
9
Which of the following
is NOT important after
a femoral head and neck
excision?
n Early return to activity
after suture removal
n Physiotherapy or
hydrotherapy to maintain
muscle mass
n Analgesia to permit
early activity
n Prescription diet
YOU WERE
8
Femoral head and neck
excision may be the
most suitable treatment for:
n 2-year-old working gundog
with unlimited finances
n 12-year-old GSD with hip
osteoarthritis and severe
muscle atrophy
n 1-year-old pet spaniel
with unilateral hip dysplasia
and limited finances
n 3-month-old Labrador
YOU WERE
Try
again
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Get
Score
10
Which of the
following is NOT
correct regarding canine
total hip replacement?
n The success rate is
around 90%
n Possible complications
include dislocation, aseptic
loosening, infection and
femoral fracture
n Implants wear out and
require replacement every
3 years.
n All sizes of dogs can
undergo THR.
YOU WERE
VNTCPD l Volume 4
l
issue 6 l NOVEMBER 2010
7