Femoroacetabular impingement: correlation between imaging parameters, sport activity and chondral damage

Femoroacetabular impingement is characterized by an abnormal contact between the acetabulum and the femoral head-neck junction. Femoroacetabular impingement shows three main clinical frameworks: pincer-FAI, cam-FAI and cam-pincer mixed form. The aim of the study was to investigate the correlation between femoroacetabular impingement, imaging, activity and chondral damages.

Forty-one patients, undergoing arthroscopic chondroartroplasty for cam and cam-pincer mixed form were considered. All patients underwent an X-Ray hip evaluation (G1 group), while 15 patients also underwent a pelvis MRI evaluation (G2 subgroup). For G1 patients, the superior-inferior offset ratio and alpha angle were calculated from the X-Ray examinations. For G2 patients, the antero-posterior offset ratio was also calculated from pelvis MRI. Chondral damage was classified according to the Outerbridge Classification.

The superior-inferior offset ratio and the antero-posterior offset ratio were respectively 0.50±0.23 and 0.33±0.19. The α angle predictive for a chondral damage of IV degree was 81.5°. The chondral damage of the patients suffering from cam-FAI and cam-pincer mixed form were respectively 3.53±0.80 and 3.00±1.41.

From the results was possible to: 1) elaborate two tables providing a reliable indirect calculation of the alpha angle; 2) establish an alpha angle cut-off value indicative for a IV degree chondral damage; 3) show that pincer-FAI does not represent an aggravating factor for chondral damage; 4) show that the level of sports activity was related to the severity of chondral damage; and 5) show that a physically demanding occupation was not an aggravating factor for chondral damage.