Acetabular Rim Degeneration

During recent years the acetabular labrum has gained increased interest because its degeneration frequently is found in association with early osteoarthritis of the hip. To determine spatial distribution of labral degeneration in the aged hip and to identify the pathologic features triggering this event, an anatomic postmortem and an intraoperative in vivo study were done in 30 cadavers (range, 60-90 years) and in 18 elderly patients (range, 69-97 years) who had hemiarthroplasty for displaced femoral neck fractures. In both groups, no gross anatomic or radiographic abnormalities suggesting advanced osteoarthritis were present. All cadaveric acetabuli (30 of 30) revealed labrum and cartilage damage. Labrum damage (17 of 18) and cartilage lesions (16 of 18) occurred less frequently and were smaller in the elderly patients. Peripheral joint degeneration was most frequent at the superior acetabular rim close to the anterior inferior iliac spine. More centrally localized cartilage lesions were present in 47% of cadavers and in 28% of patients. The majority of femurs (cadavers) (80%) showed reduced narrowing at the anteromedial femoral head-neck junction causing impingement against the corresponding acetabular rim or squeezing of this area into the joint during flexion, whereas the femoral head cartilage appeared normal in all but one hip. Acetabular rim degeneration is a constant finding in the aged hip, which seems to be triggered by femoroacetabular impingement.