Aseptic Acetabular Protrusio with Intrapelvic Migration of a Bipolar Prosthesis: A Case Report of a Rare Presentation and its Management.

Introduction: Bipolar hemiarthroplasty is a very common surgery done for geriatric patients with femoral neck as well as some trochanteric fractures. Complications usually range from infection, loosening, and dislocation to periprosthetic fractures. We present here a case report of a very rare presentation of aseptic acetabular protrusio with intrapelvic migration of a bipolar prosthesis and how it was managed. Case Report: An 80-year-old male patient of Indian origin operated with bipolar hemiarthroplasty 4 years back presented with severe pain and restricted movements of the right hip. The patient was having progressive pain for the past 1 year with a history of sudden giving way while walking 1 month back. Radiographs and further imaging showed acetabular protrusio of the bipolar prosthesis with intrapelvic migration of the head. There was no evidence of infection seen on investigations and hip aspiration. Surgery was associated with high risk due to the associated comorbidities and the close proximity of neurovascular structures to the prosthesis. The patient was managed with extended trochanteric osteotomy, implant removal, and revision total hip arthroplasty with antiprotrusio cage and long revision stem in a single stage. At 18-months follow-up, the patient is walking well without support. Conclusion: An elderly patient with multiple comorbidities and with the bipolar prosthesis lodged in the pelvis could be managed well with an excellent functional outcome. However, proper pre-operative planning with all required implants and instruments with a backup plan remains the key in such complicated and rare presentations. [ABSTRACT FROM AUTHOR]