AANA Lab Course 907-Arthroscopic/Open Strategies - Hip Preservation-What to Do with Os Acetabulum_ They Are Not All Created Equally-J.W. Thomas Byrd, MD

What to Do with Os Acetabulum_ They Are Not All Created Equally-J.W. Thomas Byrd, MD

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This presentation by J. W. Thomas Byrd, MD, at the 2019 AANA/ISHA course addresses the clinical challenge of os acetabuli—bony fragments at the acetabular rim of the hip—highlighting that these lesions vary in nature and implications. Os acetabuli may represent rim fractures, calcific or ossified labral deposits, avulsion fragments, traction phenomena, stress fractures, or unfused physes. They are frequently incidental findings on imaging and may accompany femoroacetabular impingement (FAI) symptoms requiring surgery.<br /><br />A key clinical decision is whether to excise or preserve the os acetabuli fragment during surgical hip preservation. Excision is common but risks reducing acetabular coverage, potentially causing iatrogenic instability or accelerating osteoarthritis. Conversely, fixing the fragment risks creating or worsening impingement. Thus, careful preoperative assessment is essential.<br /><br />Byrd recommends evaluating the center-edge (CE) angle with and without the fragment, using coronal and sagittal 2-D CT reconstructions to understand fragment size and morphology. He suggests a practical "rule of thumb": if the fragment can accommodate two 4.5 mm cannulated screws, it is large enough to warrant fixation; if smaller, excision is generally safe since it is unlikely to compromise acetabular stability. Surgical tips include thorough soft tissue clearance to delineate fragment margins, fluoroscopic guidance during screw placement to avoid acetabular perforation, and repairing any labral tissue over the fragment without interfering with screw anchors.<br /><br />In summary, os acetabuli are not uniform lesions. Management should be individualized, balancing risks of instability and impingement. Surgical strategies depend on fragment size, morphology, and contribution to acetabular coverage, emphasizing the importance of careful imaging and intraoperative technique.

Keywords

os acetabuli

acetabular rim

hip preservation surgery

femoroacetabular impingement

fragment excision

fragment fixation

center-edge angle

CT imaging

surgical technique

labral repair