Editorial Commentary: Indications for Periacetabular Osteotomy (Versus Hip Arthroscopy) Alone for Borderline Hip Dysplasia Require Consideration of Multiple Three-Dimensional Factors Contributing to Dynamic Pathoanatomy and Instability Severity.

The management of borderline hip dysplasia (BHD) remains a topic of particular interest in the hip preservation world. While periacetabular osteotomy remains the gold standard for frank dysplasia, management of mild or borderline dysplasia is more nuanced, and in many cases, isolated hip arthroscopy with capsular plication can yield favorable and durable outcomes, avoiding morbidity associated with osteotomy. However, the benefit of avoiding the morbidity of a periacetabular osteotomy should be carefully weighed against the risk of undertreating this complex pathology. Historically, BHD was defined as a lateral center-edge angle between 20° and 25°, with more recent studies using 18° as a lower threshold. Yet, a singular 2-dimensional measurement provides an incomplete picture. Labral hypertrophy, an upsloping lateral sourcil, fovea alta, ligamentum teres tears, Tönnis angle, Femoro-Epiphyseal Acetabular Roof index, vertical center anterior angle, and abnormal femoral or acetabular version are additional factors that help us understand dynamic pathoanatomy and the severity of instability. Some of these variables-including Tönnis angle >10-15°, ligamentum teres pathology, and vertical center anterior angle <18°-have been associated with failure of arthroscopy alone for BHD.