|
Canine Hip Dislocation
|
|
Hip Dislocation
The hip joint is a “ball and socket” type joint attaching the rear
leg to the trunk of the body. The “ball” part is the head of the first
long bone of the rear leg – the femur – and the socket is the part of the
pelvis known as the acetabulum. The femoral head is held in place by a
thick ligament called the capital ligament or simply the “round ligament
of the femoral head.” Also keeping the joint in place is the upper rim of
the acetabulum and the fact that the whole joint is enclosed in a fibrous
capsule. The local hip muscles also help support the joint.
The Patient
A radiograph is necessary to confirm the luxation but it will be clear
simply from looking at the patient (assuming he or she is walking) that
a major orthopedic problem exists. The patient will not be bearing weight
on the affected leg and the leg may actually seem shorter than the other
three.
If the luxation is not corrected, a false joint, consisting of scarring
and
fibrous attachment, may form and the patient may begin to bear some
weight again. False joints of this sort are not very strong and do not
afford normal range of motion but may be adequate for a very small patient
such as an indoor cat or sedentary toy breed dog. Surgical correction should
provide a better result, however.
The Radiographs
Sometimes it is possible to tell by feeling the joint whether or not
it is luxated. Radiographs are still necessary in patient evaluation. This
is because there is additional information to be obtained beyond simply
whether the joint is luxated. Sometimes when the capital ligament tears,
a chip of bone from is femoral attachment comes off as well. If the luxated
hip were simply popped back into place with the chip in the joint, the chip
would forever be trapped to grind painfully inside the joint. Instead, it
should be surgically trimmed.
Radiographs are also important to assess hip dysplasia (the shallow
acetabula of this condition may impede joint placement or may determine
“off the bat” that a surgical correction is needed. If the patient is a
puppy or kitten, there is a growth plate (an area where the bone is growing)
that may have been damaged in the trauma and this must be assessed. In short,
the status of the hip beyond know whether or not it is luxated is important
in selecting therapy.
Closed Reduction
Reduction is the act of putting the bones of the luxated joint back
where they belong. Closed reduction means that the bones are put back without
surgically opening the joint. If the hip appears to be normal other
than the luxation, it is probably worth at least attempting closed reduction;
although after 3 days local muscle contraction makes successful reduction
very difficult. In cats, closed reduction is problematic as the reduced
hip frequently pops out again. Still, as mentioned, closed reduction is
a non-invasive procedure and is worth a try if the hip is otherwise normal.
To reduce the luxated hip, the patient must be anesthetized to relax
the local muscles. The femoral head is manipulated back into place (often
with a satisfying pop). Radiographs confirm the reduction and a sling
is placed to keep the hip bones together while the joint capsule around
them heals.
This may sound simple enough but it is often unsuccessful. Large dogs
are difficult to manipulate. Cats tend to promptly reluxate their hips.
Do not be surprised if closed reduction proves impossible and surgery is
recommended.
The sling, called an “Ehmer” sling, involves flexing up the knee and
taping the foot to the thigh. The sling stays on approximately 1 to 2
weeks, while the patient leads a confined lifestyle indoors at home. The
bandages must stay clean and dry. After the sling has been on an appropriate
time the sling is removed and confinement continues another 2 to 4 weeks.
Surgery
There are many techniques of surgical treatment that might be employed
in keeping the bones where they are supposed to be. In a perfect situation,
the hip is reduced and only a small tear in the joint capsule is present.
Sewing the joint capsule back together holds the femoral head where it
belongs in the acetabulum.
In a less perfect situation, the joint capsule is too damaged to simply
sew back together. In this situation, screws can be placed around the acetabulum
and a hole drilled through the neck of the femur. A stiff suture can run
around the screws and through the femoral neck holding the femoral head
in place.
Another technique uses a pin passing from the femur, out the femoral
head and into the bone of the acetabulum like an axle.
There are numerous methods and the surgeon will choose the most appropriate.
Expect a sling as described to be necessary for at least a week and confinement
for at least a couple of weeks after that to be necessary.
The Femoral Head Ostectomy
This surgery is commonly referred to as the “FHO” and is best used
for smaller dogs (50 lbs or less) or very active dogs. Here, the femoral
head is cut off and removed, allowing the joint to heal as a “false joint”
(just a capsule connecting the two bones but no actual bone to bone contact).
If the dog is not carrying too much weight, a false joint is strong enough.
If the dog is very active, a false joint will form quickly. The pet typically
does not want to use the leg for the first 2 weeks but should at least
be partially using the leg after 4 to 6 weeks. The leg should be used nearly
normally after a couple of months. Many veterinarians are well experienced
with this surgery and often a specialist is not needed. This surgery is
typically substantially less expensive than the other procedures.
|
|
femoral head before FHO
|
femoral head cut off after FHO
|
This procedure is particularly helpful for cats.
If the patient has significant hip dysplasia, this may be a good
time to address the dysplasia surgically. For more information, click here.
Date
Published: 12/26/2005 12:49:00 PM
Copyright
2005 - 2007 by the Veterinary Information Network, Inc. All rights reserved.
This work was originally published by Veterinary Information
Network, Inc. (VIN) and is republished with VIN's permission.
********************
The above information is simply informational.
It's intent is not to replace the advice of a veterinarian nor to assist you
in making a diagnosis of your pet. Please consult with your own veterinarian
for confirmation of any diagnosis. Your pets life may depend on it.