Editorial Commentary: Hip Dysplasia-Arthroscopic Femoroacetabular Impingement Versus Periacetabular Osteotomy: Do Not FEAR the Size of the Next Step.

Hip dysplasia is characterized by inadequate acetabular coverage of the femoral head. There is a consensus that hip dysplasia with a lateral center edge angle (LCEA) less than18° should be treated with realignment of acetabular coverage by acetabular osteotomy, but there is controversy whether milder, borderline dysplasia with an LCEA between 18° and 25° should be treated with arthroscopy or acetabular reorientation. Identifying whether the problem is related to dysplasia or femoroacetabular impingement syndrome is essential, and a crucial factor is whether the hip is unstable. A femoroepiphyseal acetabular roof (FEAR) index with a cutoff value of 2 predicts hip stability with 90% probability, even with a normative LCEA. In addition, according to the anterior-wall index (AWI), the anterior acetabular border should cross onto the middle third of the medial femoral head radius on a line that runs parallel to the femoral neck axis through the center of the femoral head. A reduced AWI suggests a deficient anterior rim. Next, lateral labrum length correlates with the FEAR index and anterior labrum length with AWI, i.e., anterior dysplasia. Consequently, the lateral labrum increases in size with progressive instability, and the anterior labrum increases in size with decreased anterior coverage. Threshold values for labrum size should be defined to guide clinical decision making. Ultimately, we require an algorithm to guide arthroscopy versus bony correction.