Osteoarthritis caused by an inverted acetabular labrum: radiographic diagnosis and arthroscopic treatment.

PURPOSE

An inverted labrum is an acknowledged but often elusive cause of osteoarthritis. The study goals were to define the characteristic radiographic features of secondary osteoarthritis of the hip due to an inverted labrum and report the results of arthroscopic treatment.

TYPE OF STUDY

This is a case series study.

METHODS

From 220 consecutive arthroscopic hip procedures, 9 patients were identified who had had secondary osteoarthritis caused by an inverted labrum and who underwent a minimum 2 years follow-up. All were prospectively assessed with a modified Harris hip score. All patients underwent excision of a torn inverted labrum and chondroplasty. Three patients who had well- circumscribed grade IV acetabular lesions also underwent microfracture of the subchondral bone.

RESULTS

Characteristic anteroposterior radiographic features included isolated narrowing of the superolateral joint space. This narrowing caused a lateral convergence in the normally parallel lines created by the radius of curvature of the subchondral bone of the acetabulum and the convex surface of the femoral head. These 2 features created a false appearance of dysplasia (pseudodysplasia), because the center edge angle of Weiberg was normal in 6 cases (range, 24 degrees to 41 degrees; average, 29 degrees ) and was indicative of true dysplasia in only 3 cases (17 degrees ). The median preoperative score was 51, and the postoperative hip score was 56. Only 4 patients showed significant improvement. The best results were in the group with microfracture; the average improvement in this group was 36.

CONCLUSIONS

An inverted labrum is an occasionally encountered cause of osteoarthritis of the hip. The radiographic features seen with this disorder are quite characteristic and essentially pathognomonic. Recognizing these features in this population may help the physician avoid an unnecessarily extensive work-up for poorly explained hip pain. The 3 patients with microfracture responded well to the arthroscopic technique; otherwise the results of arthroscopic treatment were poor. The outcomes were no better than those previously reported for arthritis of all causes.