In simple terms, a hip luxation means having a dislocated hip. Medically speaking, it is referred to as a coxofemoral luxation, because the ball-and-socket joint formed by the pelvis and the head of the femur is called the coxofemoral joint. The hip joint is held together by a strong round ligament and the joint capsule, and is stabilized by the surrounding muscles. A hip luxation results in the displacement of thehead of the femur (the “ball”) from the acetabulum (the “socket”). In order for the luxation to occur, the round ligament and the joint capsule must have been torn completely, which is what allows the femur to become dislocated. With these injuries, damage to the muscles of the hip often occurs as well. (show anatomy of hip; diagram or rad of luxated hip)
A hip luxation can occur in any age, breed, or gender of dog, and can occur in cats as well. It occurs more commonly in dogs that are older than one year; in immature developing dogs, a fracture of the femoral head is more common.
The primary sign of a hip luxation is a severe, acute, non-weight-bearing lameness. There are several types of hip luxations, and depending on which one is present, the animal will exhibit different signs. The most common type of luxation is one in which femur is pulled upwards. This is called a craniodorsal luxation, and occurs in about 75% of affected dogs and cats. In a craniodorsal luxation, the limb will appear shorter than the unaffected side. The paw is positioned underneath the body, and the stifle (knee) is rotated externally. The other type of hip luxation seen more commonly is a caudoventral luxation. In this case, the head of the femur ends up under the pelvis, in an opening called the obturator foramen. This results in the limb being held away from the body, (abduction) and the stifle being internally rotated. (show images of the different types of luxations)
Your veterinarian can usually diagnose a hip luxation based on clinical signs and a physical exam. However, it is important that radiographs be taken to rule out other conditions such as fractures of the acetabulum or of the femur. Additionally, because hip luxations are usually associated with trauma, as many as half of these patients have another major injury as well. Therefore, a thorough physical exam and the identification of concurrent trauma is very important.
Most dogs with hip luxations have sustained trauma, such as a motor vehicle accident. In some cases, the luxation can happen with minor trauma, such as falling down a couple of stairs. Dogs that have luxations that occur as a result of minor trauma must be evaluated for an underlying cause of hip instability associated with hip dysplasia.
Hip luxations must be treated as soon as possible to prevent further damage to the soft tissue surrounding the joint and degeneration of the cartilage. The veterinarian will first attempt to replace the femoral head into the acetabulum manually, from the outside. This is called a closed reduction, and it is performed under general anesthesia. The leg is then placed in a special sling for 10-14 days, and the dog must be kept confined to a cage. This allows the joint time to heal and re-stabilize without the risk of it reluxating. If closed reduction is not sufficient to correct the problem, surgery is required. Surgical correction involved reducing the femoral head into the acetabulum and securing the joint with artificial ligaments. In severe cases where neither open nor closed reductions are options, the patient may have to undergo either a total hip replacement (THR) or a femoral head and neck osteotomy (FHO).
Since a hip luxation results from trauma, there are no definitive ways to prevent the injury from happening.
The success rate of closed reduction of a hip luxation is about 50%, while the success rate of open reduction is 85% to 90%. If a hip stays reduced for 3 weeks, the prognosis is excellent for continued reduction unless another trauma is occurs or if there is underlying hip laxity (dysplasia). Persistent lameness is seen about 30 to 35% of cases and is due to arthritis that has developed in the joint. It is also possible that there are underlying issues cases such as hip dysplasia or major damage to the cartilage of the joint from the initial injury.