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HIP DYSPLASIA
This information is provided by
Provet for educational purposes only.
You should seek the advice of
your veterinarian if your pet is ill as only he or she can correctly advise
on the diagnosis and recommend the treatment that is most appropriate for
your pet.
Note for Pet Owners:
Hip dysplasia is a condition that frightens many owners although in truth
most dogs can live a normal, productive and otherwise healthy life - even
with quite severe hip disease present. There is evidence to show that the
severity of the changes in the hips (as seen on an XRay) is not
directly related to the amount of pain shown by an animal. Nevertheless, hip
dysplasia can be a debilitating disease and there is a strong hereditary
influence - so responsible owners and breeders should have their animals
screened by their veterinarian, and avoid breeding from the worst affected
individuals. The occurrence of hip dysplasia can be reduced by not breeding
from affected animals.For more information about the BVA/KC Hip Dysplasia
Scheme in the UK email info@provet.co.uk
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Description
Hip dysplasia occurs when there is insufficient stability to keep
the head of the femur (the "ball") within the acetabulum (the
"socket") of the hip joint. This may be due to stretching of the joint
capsule or
weakness in the surrounding muscles, or a failure of the
"socket" to develop properly.
Because of this instability the hip joint develops abnormally, remodelling
of the bones occurs and new bone is deposited around the joint (used to be
called arthritis - now called degenerative joint disease). The result is hindleg
weakness, pain and functional disability.
Cause
It may surprise people to learn that the cause of hip dysplasia is not known !
Hip dysplasia is a complex (called polygenic or multigenic) disease with many
factors involved in the cause. The most important are genetic and environmental
factors but, based on detailed analysis of inheritance in German Shepherd dogs
the disease is only described as being moderately heritable in that breed. Contributing
factors are :
Breed - genetic inheritance, BUT specific genes not yet identified. Also
multiple genes involved (polygenic). Body size - low prevalence -
ancestral dog size; greater prevalence -large/giant breeds Body type - low
prevalence - slender and fit. Low subcutaneous fat content (1-2%); greater
prevalence- giant breeds, heavy conformation, with acromegaly. Relatively
high subcutaneous fat content(5-10%). Growing pattern - rapid growth rate
and excessive weight gain (above the average for the breed) can both
increase the likelihood of hip dysplasia occurring. Increased activity has
been associated with increased likelihood of developing hip dysplasia.
Possibly increased activity exposes the animal to increased chance of
injury, or to excessive biomechanical forces which alter the stability of
the hip joints. Muscle disorder - a muscle disease (developmental myopathy
of the pectineus muscle) has been described in German Shepherd puppies with
hip dysplasia, but a direct link between the two conditions was not proved,
though it may have been present. Hormone - experimentally a female hormone
(the oestrogen relaxin) can induce hip dysplasia due to relaxation of
supporting ligaments in dogs, including greyhounds. However there is no
evidence of a naturally occurring role for the hormone in the cause of the
disease. Diet does not seem to be important except when excessive calorie
intake occurs resulting in too rapid a rate of growth or excessive weight
gain. There is good evidence that too high calcium intake may results in
skeletal developmental problems, which may include hip dysplasia.
Breed Occurrence
Hip dysplasia affects humans (1.3 children in every 1000) and ALL domestic
animals including cats and dogs. Body size is an important factor and one of the
of the highest prevalence's of the disease is in large and giant breeds of dog
in which over 30% of some breeds may be affected. The disease is less common in
dogs with a body size similar to the ancestral dog and it is rare in
undomesticated animals.
In the USA screening XRays have indicated that in some breeds over 20% are
affected by hip dysplasia including - in descending order : St Bernards (43.2%),
Newfoundlands (39.9%), Bullmastiffs (34.5%), English Setters (32.1%), Gordon
Setters (32.1%), Old English Sheepdogs (29.9%), English Springer Spaniel
(27.3%), Akita (27.1%), Chesapeake Bay Retriever (25.7%), Golden Retriever
(27.5%), Norwegian Elkhound (25.6%), Rottweiler (25.4%), the German Shepherd Dog
(25.1%), Giant Schnauzer(24.2%), Standard Poodle (23.6%) and the Brittany
Spaniel (22.4%). (Reference Riser WH et al J Am Vet Med Assoc (1974) 165:79).
Other breeds are over-represented in other schemes eg in the UK the Clumber
Spaniel has the second worse breed mean scores (42) in the BVA/Kennel Club
scheme (2001)
Dogs less than 30.5 cm in height and less than 11.3 kg in body weight rarely
develop hip dysplasia.
It is interesting to note that hip dysplasia is extremely rare in racing
greyhounds, but it is seen frequently in greyhounds kept as pets. This
highlights the fact that environmental factors are important as well as
genetics.
Equal numbers of males and female dogs are affected with the hip dysplasia.
Signs
The disease affects young animals and dogs are usually aged between 5-12 months
when signs are first noted. Signs include a swaying hindleg gait,
hindleg lameness, muscle wastage around the hindquarters, reluctance to
exercise, fatigue during exercise, inability to climb stairs or jump up.
Sometimes there is a loud "click" heard during exercise.
Occasionally affected animals walk in a hunched-up manner with an arched back.
In some cases (the worst cases) the dog will wince with pain when it moves
it's hindlegs. It is important to realise that the occurrence of pain is not
directly related to the degree of abnormal change that can be seen on XRays.
Complications
Remodeling of the hip hip joint can lead to severe deformity. In addition
the instability results in new bone being deposited around the joint - this can
lead to pain, and reduced range of movement. With advancing age, as degenerative
joint disease progresses in the hips, ambulatory function is
gradually lost resulting in great difficulty rising from a lying down position
or negotiating steps and stairs. In large and giant breeds of dogs an inability
to jump up (into cars for example) can present serious management problems for
owners.
Post-operative complications can occur - particularly following the removal
(excision) of a femoral head and neck.
Diagnosis
Hip dysplasia is diagnosed from the presenting history, physical examination and
is confirmed by taking XRays of the hip joints. For accurate interpretation of
the XRays the position of the animal is critical and in order to position the
animal correctly (lying on it's back) it is necessary to immobilise the
patient. This usually requires the administration of a general anaesthetic. This
dog has severe hip dysplasia with secondary arthritic changes- some of which are described
below
A Abnormal, square
shaped head to the femurs with a broader than normal neck. The head
"ball" is not lying properly in the acetabular fossa B
There is a lot of "new" bone around the joints such as this osteophyte
lying in front of the acetabulum C There
is a loss of cartilage on the surface of the joint resulting in a loss (or
narrowing) of apparent joint space between the head of the femur and the
acetabulum D There is an increase in the
radiodensity of the bone lying under the acetabulum articular surface. This
gives the bone a very white colour - and is called sclerosis. In addition, the
joint space (darker line) appears to be wider because the head of the
femur is partially lifted out of the socket created by the acetabulum. E
New bone can be deposited all around the joint, including along the
neck of the femoral head.
Treatment
In young animals genetically predisposed to develop hip dysplasia they should be
reared in a cage with minimal exercise as this has been shown to reduce the
likelihood of dysplasia developing. Food intake should be restricted during
growth to avoid too rapid a growth or excessive weight gain. Medical treatment
involves the administration of pain killers and rest. Aspirin and other
non-steroidal anti-inflammatory drugs can be very successful , but they do have
potential side-effects if used over a long period of time. Corticosteroids can
also give a clinical improvement but most authors advise that they should be
used with caution.. Surgical intervention is possible in young dogs with acute
pain - various techniques can be used in an attempt to increase the stability of
the hip joint.
- Triple osteotomy of the pelvis to increase the surface coverage of the
femoral head (the "ball") by the acetabulum (the
"socket")
- Total hip replacement
- Removal of the femoral head and neck (excision arthroplasty)
- Changing the angle of the head of the hip - corrective osteotomy
- Myotomy - sectioning the pectineus, iliopsoas or or gluteal muscle
or muscle attachments to provide pain relief
Prognosis
The prognosis is good for most animals, but as they get older the degenerative
joint disease makes locomotion more and more difficult
Screening Programmes
There is no doubt that owners should only breed from
"normal" dogs and attempt to reduce the numbers of affected animals in
those breeds known to develop hip dysplasia on a regular basis. Controlled
breeding of German Shepherd dogs in Sweden and of a colonies of German
Shepherd dogs in the USA have suggested that breeding only from dogs with
normal hips can reduce the incidence of hip dysplasia to less than half
- from 39% to less than 17%. However , in a report publish in January 2000 the
value of existing schemes has been questioned. HD Update In many countries there are highly
sophisticated scoring systems by which the degree of hip dysplasia can be
assessed. In the UK the British Veterinary Association in conjunction with the
Kennel Club run a scheme and further details can be obtained from your
veterinary practice - or by writing to the BVA/KC Hip Dysplasia Scheme, 7
Mansfield Street, London, WIM OAT. If you are an owner and would like more
information about the UK Scheme Provet will be please to send it to you e-mail
info@provet.co.uk If you are a
veterinarian and would like more information about the UK scheme Provet will
be please to send it to you e-mail info@provet.co.uk Updated
October 2013
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