PAPER 178: RADIOGRAPHIC DETERMINATION OF ACETABULAR CARTILAGE DELAMINATION IN PATIENTS WITH LABRAL TEARS

Abstract

Purpose: The treatment and prognosis of labral tears secondary to femoroacetabular impingement depends on the severity of the labral injury and whether or not there is concomitant injury and delamination of the adjacent articular cartilage. At present, there is no simple and reproducible technique to determine if there is delamination of the adjacent articular cartilage. We undertook a study to determine if the preoperative presence of a previously undescribed radiographic finding, a “delamination cyst”, correlated with delamination of the articular cartilage at the time of hip arthroscopy.

Method: The preoperative radiographs of 125 consecutive hip arthroscopies in which a labral tear was identified intraoperatively were retrospectively reviewed.. In each case an anteroposterior (AP) pelvis and AP, lateral and frog lateral hip radiographs were evaluated for the presence of delamination cysts, perilabral cysts, abnormalities of the femur and acetabulum, as well as arthritic changes. A “delamination cyst” was defined as a subchondral cyst either directly adjacent to a perilabral cyst, or in relation to a subchondral crack in the anterolateral portion of the acetabulum. These findings were then compared and correlated to the intraoperative arthroscopic findings.

Results: We identified 16 patients with delamination cysts on radiographs and 15 patients with delamination of the acetabulum on arthroscopy. A strong correlation was found between the preoperative radiographic presence of a delamination cyst and acetabular delamination at the time of arthroscopy – sensitivity of 93.3%, specificity of 98.8%, positive predictive value of 93% and a negative predictive value of 99% (p=0.034). No other radiographic findings were associated with the status of the articular cartilage.

Conclusion: A “delamination cyst” is a previously undescribed and novel radiographic sign that can accurately predict preoperatively which patients with labral tears have associated acetabular cartilage delamination or chondral damage. Delamination cysts can be easily identified on plain radiographs without performing any special imaging or invasive infiltrations. Identifying these cysts preoperatively can aid the surgeon in selecting the appropriate surgical procedure and help predict the patient’s prognosis following the planned surgical procedure.