Hip dislocations can also occur as a complication of hip replacement surgery. Because an artificial hip replacement is different from a normal hip joint, dislocation after joint replacement is a possible risk of surgery. In fact, between 1-4% of patients may sustain a hip dislocation after undergoing hip replacement surgery. New types of hip replacements, and new techniques for performing surgery, are making this a less common complication.
The Hip JointThe hip joint is a ball-and-socket joint. The socket of the hip joint is a deep cup of bone that is part of the pelvis (called the acetabulum). The ball is the top of the thigh bone (the femur)--the name of the hip joint is the femoroacetabular joint. The major reason hip dislocations are so unusual, is that the ball is held deeply within the hip socket. Unlike the shoulder joint, where the ball is sitting loosely on the socket, hip dislocations are uncommon, whereas shoulder dislocations are very common.
In addition to the bone anatomy of the hip that creates a stable joint, the body also has strong ligaments, and many muscles and tendons that also contribute the the stability of the hip joint. In order for a hip dislocation to occur, significant force must be applied to the joint. People who feel a snapping sensation of the hip seldom have a dislocation of the joint; these conditions are known as snapping hip syndrome.
Hip DislocationsWhen a hip dislocation does occur, there has to be damage to the structures that hold the ball in the socket. Common injuries that occur when a hip dislocation happens include fractures of the bone surrounding the hip, tears in the labrum and ligaments of the hip, and cartilage damage of the joint. In addition, injury to blood vessels that nourish the bone can lead to a condition called avascular necrosis (also called osteonecrosis of the hip).
Treatment of a Hip DislocationThe most important treatment of a dislocated hip is to properly position the ball back inside the socket--called reducing the joint. In order to reposition the hip joint, the patient will require general anesthesia. Unlike a shoulder dislocation that many patients, especially those who have had repeat shoulder dislocations, can reposition on their own, a hip dislocation usually requires significant force to reposition.
Once the ball is back within the socket, your doctor will evaluate for other injuries, including injury to the bone, cartilage, and ligaments. Depending on the injuries that have occurred, further treatment may be necessary. Broken bones may need to be repaired in order to keep the ball within the socket, and damaged cartilage may have to be removed from within the joint. Hip arthroscopy is becoming more commonly used as a tool to ensure the joint is as healthy as possible following this type of injury. In addition, the development of early arthritis of the hip is very common following the type of trauma to the hip joint. Therefore, many patients who have a hip dislocation ultimately require hip replacement surgery.
Hip SubluxationA related injury is called a hip subluxation. A joint subluxation is another way of describing what people often call a partial dislocation. In the case of the hip joint, it means the ball started to come out of the socket, but did not come fully out. Patients with a hip subluxation may have some of the same complications as those who sustain a hip dislocation. A hip subluxation was the injury that ended the career of football star Bo Jackson.
"Insights into Rare but Devastating Football Hip Injury Duke Medicine News and Communications, Nov. 3, 2004.
Foulk DM and Mullis BH. "Hip Dislocation: Evaluation and Management" J Am Acad Orthop Surg April 2010 ; 18:199-209.