EP1.80 Defining the Stigmata of Hip Instability: When to consider combined surgery and how to avoid failure in hip preservation surgery

Abstract Background Hip microinstability is a painful phenomenon caused by supra physiological mobility resulting from underlying bony and functional abnormalities. It is commonly encountered in patients with borderline acetabular dysplasia and remains challenging to diagnose due to a lack of a universally accepted definition. Historically, patients with borderline hip dysplasia have mixed results following isolated hip arthroscopy leading to high unsatisfaction and reoperation rates. Therefore, the indication for the use of combined surgery is relevant in the borderline dysplastic patient population when signs of hip microinstability are present. Purpose To describe a set of clinical, intra operative, and imaging findings as the “stigmata of instability” in support of a diagnosis of hip microinstability and potentially assist with proper indication for a combined arthroscopic and open procedure to improve outcomes following hip preservation surgery Study Design Narrative review and expert opinion, Level V Methods A narrative review was performed focusing on hip microinstability, borderline acetabular dysplasia, and outcomes following hip preservation surgery. Peer-reviewed studies evaluating clinical presentation, imaging characteristics, intraoperative findngs, and outcomes were synthesized. Results Nine stigmata of hip instability were identified across clinical evaluation, imaging, and intraoperative assessment. These include inside-out labral tears, posterolateral femoral head cartilage wear, focal posteroinferior acetabuluar cartilage damage, endospheric pseudocam deformity, an easily distractable hip joint, generalized ligamentous laxity, posterior hip pain, lateral abductor overload, and labral hypertrophy. Conclusion Hip microinstability is a commonly underdiagnosed spectrum of disease that occurs due to inherent altered joint mechanics leading to secondary compensatory mechanisms. These findings can be identified as a group of clinical and intraoperative features known as the stigmata of instability. The ability to recognize these features may lead surgeons to consider combined hip arthroscopy with periacetabular osteotomy and avoid high failures rates with isolated approaches to this distinct patient population.