Tom Youm: Borderline hip dysplasia and femoroacetabular impingement

Today’s guest is Dr. Thomas Youm from NYU Langone Health a high-volume hip arthroscopist.The focus of the conversation is a niche but common clinical scenario: femoroacetabular impingement syndrome in the setting of borderline hip dysplasia—typically defined by a lateral center-edge angle between 20 and 25 degrees. We use several recent papers from Dr. Youm’s group as the starting point, but the discussion stays practical: when a hip lives near that borderline zone, where undercoverage and potential instability may coexist with impingement morphology, who truly benefits from arthroscopy, who should be screened out, and what long-term outcome studies can—and cannot—claim.We talk about definitions that drive everything: how “borderline dysplasia” is operationalized beyond a single angle, how FAIS is defined and selected for surgery, and how labral and capsular management can shift a hip toward stability or toward symptoms.We talk about imaging as decision-making, not just documentation: what plain radiographs miss, how MRI can (and should) classify the labrum and cartilage more meaningfully, when CT adds value for combined femoral and acetabular version, and how those parameters change counseling and surgical indications.We talk about dynamic assessment—especially the role of ultrasound to evaluate motion-dependent instability in select patients—and how that complements static imaging when the story and exam do not match the radiographs.We also spend time on endpoints. We talk about what “survivorship” means when studies use revision arthroscopy and conversion to total hip arthroplasty, and how that aligns—or fails to align—with the outcomes that matter most to patients: pain, function, athletic participation, and the possibility that some hips may later need a reorientation procedure rather than another arthroscopic intervention.