Anatomic Changes in the Hip May Cause Impingement

Early signs of hip osteoarthritis (OA) in young adults has puzzled surgeons for years. Hip dysplasia (shallow hip socket) is a common cause of OA. But these patients don't have dysplasia. Genetics and overload of the joint were two other popular theories. But no proof has been found to support these ideas.

More recently, a new theory has emerged. Femoroacetabular impingement (FAI) may be the cause of hip pain (and later OA) in these patients.

FAI is the abnormal contact between the femoral neck and the acetabular rim (hip socket). The femoral neck is the supporting structure between the femur (thigh bone) and the round head of the femur that fits into the hip socket.

Minor changes in the anatomy of the femur or acetabulum may be at fault. The result of these changes is the pattern of abnormal contact described. Over time the bone starts to rub along the cartilage of the hip and the acetabular rim called the labrum.

The femoral head can get jammed into the acetabulum during normal motion. Tears in the cartilage start to develop. The cartilage under the labrum may pull away from the bone. These lesions eventually progress to form degenerative joint disease.

The patient reports groin pain that comes and goes with activity. Walking long distances especially aggravates the condition. The pain may travel from the hip to the knee. The diagnosis can be difficult to make. Special tests and careful attention to X-rays and MRIs may be helpful.

Treatment begins with conservative care. This includes changing activities to avoid aggravating the condition. Anti-inflammatory drugs may be used. Symptoms can be controlled but usually surgery is needed to allow full activity in these young patients.

The surgeon dislocates the hip. The bone is shaved to restore the normal rounded anatomy. The surgeon is careful to preserve the blood vessels and balance the hip joint anatomy. The torn labrum is repaired if possible or removed. The hip is put back in the socket.

The authors describe the operation in detail using several different surgical methods. Open incision, arthroscopic surgery, and the anterior approach are included. New ways to use traction to dislocate the hip are also being studied.