Abstract
Purpose: The purpose of this study was to determine whether X-ray attributes of the femoro-acetabular impingement (FAI) - alpha angle (AA) and offset ratio (OR) reflect real measurements on resected femoral heads. Methods: FAI AA and OR were assessed on 50 consecutively resected femoral heads.
The parameters were measured on heads cut through the maximum range of the deformity and compared to the same parameters on standardized X-ray projections (anteriorposterior [AP] and axial views). Results: Mean AA was 76.47° on dissected heads vs. 75.81° on axial X-ray (p = 0.688).
Mean OR was 0.132 on dissected heads vs. 0.220 on axial X-ray (p < 0.001). Mean AA on ideal AP X-ray was 79.46° vs. 81.51° on AP standing plain X-ray view (p = 0.431).
AA measurements on plain X-ray AP and axial view of halved femoral heads correlated highly. Conclusions: AA on axial X-ray view reflected the real AA in our series, but the risk of cartilage damage cannot be predicted.