The hip is a simple ball and socket joint that has a wide range of movement in all directions and its efficient function is essential to normal hind limb movement. The joint is comprised of the acetabulum, which is a cup-shaped depression in the pelvis (this forms the “socket”), and the femoral head, which is part of the femur (thigh bone). The femoral head forms the “ball” of the “ball and socket” joint. The stability of the hip joint comes from the joint capsule, a short ligament that connects the ball to the socket and the muscles that surround the hip.
What does hip dislocation mean?
When the hip dislocates, the femoral head is displaced from the acetabulum (out of socket); in most cases of hip dislocation, the femoral head will be positioned above and in front of the acetabulum. The most common cause of hip dislocation is blunt force trauma such as a fall or an automobile injury, but any traumatic injury to the hip area may cause a hip dislocation.
An increasing number of cats, especially purebred cats (Maine coon, Himalayan, Persian, Devon Rex, and Siamese), are being diagnosed with hip dysplasia (poor hip joint conformation), like that seen in dogs. Hip dysplasia may predispose a cat to hip dislocation.
What are the clinical signs of a dislocated hip?
With some traumatic injuries, your cat may have been missing from home for a few days because it may have had difficulty returning home. In addition to having a dislocated hip, there may also be other injuries, some of which may be more serious. Most cats with a hip dislocation will have severe hind limb lameness and may not be able to put any weight on the affected limb. The affected limb is often carried in a flexed (folded or pulled up) position and may appear shorter than the other limb.
How is a hip dislocation diagnosed?
The hip joint will be painful when your veterinarian manipulates it during the physical examination of your cat. In addition, your veterinarian may feel a grinding sensation (crepitus) when the femur is moved.
"A diagnostic X-ray will show the direction of dislocation and whether there is a fracture in any part of the hip joint"
The diagnosis is confirmed by a X-ray (radiograph). A diagnostic X-ray will show the direction of dislocation and whether there is a fracture in any part of the hip joint. If a fracture is present, it may be more difficult to repair the dislocation. If your cat has other, more serious or life-threatening injuries, these injuries will be treated before your veterinarian will consider addressing the dislocated hip.
What is the best treatment for a dislocated hip?
In most cases of hip dislocation, it is desirable to replace the femoral head in the acetabulum. The only exception to this rule is if your cat has another illness or if there are other factors that make anesthesia too risky to undertake. If the hip is left dislocated, a false joint will form, and the cat will have permanent lameness.
In many cases, it is possible to replace the femoral head in the acetabulum by manipulation under general anesthesia (closed reduction). The success of a closed reduction increases if the dislocation is recent (i.e., the injury is less than 72 hours old).
After the dislocation is reduced or replaced, a supportive wrap or bandage will be applied to immobilize the leg and prevent the hip from popping back out (reluxating). This bandage or support wrap will remain in place for 4 to 14 days. The occasional cat may not tolerate this bandage well. The cat must be closely supervised, and its activity must be severely restricted, to ensure that the bandage is not too tight and that the cat is not too distressed by the support wrap.
In some cases of hip dislocation, it will be impossible to replace the femoral head in the acetabulum or it will keep slipping out of the socket. In these cases, surgery is required to repair the injury. Surgical options include joint capsule or round ligament reconstruction (toggle pinning), total hip replacement (THR), or femoral head/neck ostectomy (FHNO). The specific surgical repair technique will depend on the nature of the injury and the preference of the veterinary surgeon.
What postoperative care does my cat need?
If it was possible to put the femoral head back into the acetabulum without surgery, your cat will need to be confined to strict cage rest and will have a bandage to keep the leg motionless and supported. The bandage and leg should be checked daily for swelling, odor, and discomfort. Your veterinarian will give you specific instructions for the care and monitoring of any bandages.
If your cat requires surgery, there are many techniques that might be used to repair the dislocation. A bandage may be placed, depending on the type of surgery, and it will be necessary to restrict your cat as directed by your veterinarian.
Regardless of which method is used to fix the hip, pain medications will be necessary.
What is the long-term prognosis for my cat?
If the femoral head has been successfully replaced and the correct postoperative treatment has been adhered to, it is unlikely that the hip will dislocate again. In many cases, the hip joint will regain full function and require no further treatment. However, some cats may develop a stiff or arthritic hip months or years after the dislocation, and this may require additional treatment. Cats that were unable to have the joint successfully replaced often limp or have limited use of the limb unless surgery is performed. Most of these cases will eventually require treatment for osteoarthritis due to their injury.
