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Small Animal articles
Hip Dysplasia
Definition
Hip Dysplasia is a developmental disorder of the canine hip
joint, which is strongly inf luenced by inherited and environmental
factors. It can cause SPONTANEOUS hind limb lameness in a
proportion of affected dogs. The condition is often bilateral
although lameness may only be seen in one leg. Giant, large
and medium sized breeds are most commonly affected although
the problem can be recognised in small breeds.
What Happens
The normal canine hip joint is a tight articulation between
the head of the thigh bone (f emur) and the deep socket in
the pelvis (acetabulum). The femur head should sit within
the acetabulum so that more than 50 % of its surface is snugly
contained. HIP DYSPLASIA describes malformed joints, which
are loose fitting (lax).
This laxity results in an unstable gait, and
the femur head rubs unevenly against the rim of the pelvic
socket. The joint cartilage is then subject to excessive "wear
and tear' and the joint capsule lining becomes inflamed and
painful. These processes result in deformity of the bones
and arthritis develops.
Clinical Signs
One of the main problems in detecting Hip Dysplasia is the
surprising but well-known fact that some dogs with abnormal
joints do not show any lameness and apparently walk with a
norm al gait. Lameness is only apparent if the joint is suff
iciently unstable or painful to enforce a change in gait and
may relate to the age of the dog as well as the severity of
the condition. Potentially dysplastic hips are probably normal
at birth but deteriorate as the animal grows. Signs of lameness
appear as the puppy becomes more active. They do
not move as freely as normal dogs and often 'bunny hop' when
trotting - as this allows them to shift weight off the painful
hind leg on to the forelegs. They prefer to sit rather than
stand and have difficulty with stairs. At the walk they may
have a marked sway and the pelvis appears to rise and fall
with each step. Puppies suffering from severe dysplasia may
not be able to move faster than a painful walking pace.
Hip Dysplasia progresses significantly between
6 and 18 months of age with most of the changes developing
before 2 years old. In adult dogs the changes that began in
early life may result in hip arthritis in middle or old age.
The dog will then become lame even though no signs were noticed
when it was a puppy.
Causes
Genetic and environmental factors influence the development
of Hip Dysplasia and affect the final degree of lameness and
disability. The environmental factors of most importance are:
-
- Feeding a diet that results in excessively
heavy puppies at a young age. This leads to overloading
of the soft cartilage of the developing joint and a resulting
deformation of the predisposed dysplastic joint.
- Over exercise of dogs with unstable joints
will exacerbate any wear and tear of the hip.
Treatment
Various methods of treatment are av ailable for Hip Dysplasia
nowadays. Rest and anti-inflammatory drugs will often help
dogs showing pain after exercise.
Lead walks which are short but frequent - 10
minutes 4 times a day - will allow the growing skeleton to
adapt and the joint to become m ore stable and pain-free by
the time the dog becomes mature at about 1 5 months of age.
This is greatly helped by keeping the dog slim and not allowing
it to grow too fast. The success of such conservativ e treatment
is about 60 to 70 % and the
dog can then be allowed to become more active.
Dogs with severe signs that do not respond
may need corrective surgery, which may take many forms. In
young dogs, realignment of the hip joint components can be
performed by cutting the bones and adjusting them with steel
plates and screws. For older dogs, a total hip joint repl
acement in which the femur head and acetabulum are replaced
by a stainless steel prosthesis, which fits into a plastic
socket, can be performed.
These operations are costly and may have to
be carried out at veterinary referral centres. |
