Editorial Commentary: Treating Hip Impingement Without a Computed Tomography Scan? You Might as Well Operate With a Blindfold.

Hip impingement is defined as a bony conflict between the femur and acetabulum occurring throughout normal or supraphysiological range of motion. Traditionally, the cause was attributed to reduced femoral head-neck offset and/or excessive acetabular coverage, giving rise to cam, pincer, and mixed impingement. However, recent outcome studies showing less favorable results of hip arthroscopy in patients with femoral and acetabular version abnormalities have sparked renewed interest in the pathomechanics of hip impingement. We now have a greater appreciation for the 3-dimensional scope of the problem through specialized computed tomography sequencing allowing assessment of the entire limb and pelvis. Consequently, we have learned that rotational hip range of motion is more strongly correlated with combined femoral and acetabular version than with the sphericity of the femoral head, allowing us to counsel patients accordingly. We also recognize that impingement can occur with little to no femoral asphericity if the combined femoral and acetabular version does not permit adequate clearance for unimpeded motion. This improved understanding can be applied to diagnose subtle and uncommon cases of impingement and will ultimately enable a more complete bony resection.