Usefulness of cross-table lateral view radiograph for the diagnosis of cam-type femoroacetabular impingement.

The purpose of this study was to examine the usefulness of cross-table view in the clinical diagnosis of cam-type femoroacetabular impingement (FAI). We measured the α angles on radiographs taken in cross-table lateral view in 39 hips with cam-type FAI and compared with those measured in 45 control hips. Alpha angles ranged from 30° to 78° (mean 56°) in the control group and from 47° to 120° (mean 81.1°) in the FAI group. From a canonial discriminant analysis, the cutoff value of α angle was 68.2°. Sensitivity analysis showed a sensitivity of 87.18 %, specificity of 88.89 %, and accuracy of 88.3 %. Cross-table lateral view is useful for the diagnosis of cam-type FAI.