Hip Dislocation - Mar Vista Animal Medical Center

HIP DISLOCATION

normal hip - femoral head fits snugly inside acetabulum

normal hip - femoral head fits
snugly inside acetabulum
(original graphic by marvistavet.com)

Dislocated hip

Dislocated hip
(original graphic by marvistavet.com)

In order to understand how hips dislocate and how they can be put back in place, some knowledge of the anatomy is needed. The normal hip joint can be described as a "ball and socket." The thigh bone, called the "femur" possesses a head that constitutes the "ball" part of the hip joint while the socket is a special area of the pelvic bone called the "acetabulum." In other words, the femoral head and acetabulum form the ball and socket of the hip joint. The femoral head is held in place by a thick ligament called the “capital” ligament or simply the “round ligament of the femoral head” which spans across the center of the joint. Also keeping the bones in their proper location are the muscles of the hip, the upper rim of the acetabulum which acts as a protective ledge, and the fact that the whole joint is enclosed in fibrous capsule.

Hip dislocation is the common term for the separation of the femoral head from the pelvic acetabulum. The more medical term is “hip luxation” and you will probably hear your veterinarian use this term.

In order for the hip to luxate/dislocate, trauma must be severe enough to break the capital ligament and tear the joint capsule. The femur almost always luxates the same way: up and forward.

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 but not in a normal way. 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. That said, better results are obtained if the hip can be put back together in its natural configuration.

limping dog
(original graphic by marvistavet.com)

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 tears off from where the ligament had attached to the femoral head. 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.

Severe hip Dysplasia in both hips. A radiograph like this makes for
special considerations if one of the hips becomes dislocated.
(original graphic by marvistavet.com)

Radiographs are also important to assess hip dysplasia (the shallow acetabula of this condition may impede manual 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 simply knowing whether or not it is luxated is going to be 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 no matter how old the luxation is 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 the patient must be confined for about two weeks in a cage or similar small area while the joint tissue heals.

Traditionally, the Ehmer sling has been used to hold the leg in place during the healing period. This sling involves flexing up the knee and taping the foot to the thigh. Other similar slings can be employed so as to hold the "ball" inside the "socket" of the hip. The problem with slings is that they are difficult to apply. Bandage sores can result easily if the sling is not perfectly fitted. For this reason, most specialists prefer cage rest over slings and bandages for safety reasons.

Ehmer slings are usually fashioned out of bandage tape but can be purchased pre-made

Ehmer slings are usually fashioned out of bandage
tape but can be purchased pre-made
(original graphic by marvistavet.com)

Manipulating the bones back in place may sound simple enough but it is not always successful. Large dogs are difficult to manipulate. Cats tend to promptly reluxate their hips. Do not be surprised if closed reduction does not work and surgery is recommended.

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 hold 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 (effectively re-creating the torn capital ligament).

There are numerous methods and the surgeon will choose the most appropriate. Expect some type of bandaging 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

normal hip

normal hip
(original graphic by marvistavet.com)

femoral head cut off after FHO

femoral head cut off after FHO
(original graphic by marvistavet.com)

This surgery is commonly referred to as the “FHO” and is best used for smaller dogs (50 lbs or less), for very active dogs, or for cats. 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 pet 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 4-6 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. For more details, click here.

If the patient has significant hip dysplasia, this may be a good time to address the dysplasia surgically. For more information on hip dysplasia, click here.

Page last updated: 4/22/2023