The status of acetabulum in bipolar HIP replacements in orthopaedics oncology cases

Background: Bipolar hip endoprosthesis replacement is a commonly employed procedure in orthopaedic oncology that requires the resection and reconstruction of the proximal femur. With improving survival rates, issues of implant durability and acetabular wear have become increasingly important. The decision to replace the acetabulum in bipolar hip endoprosthesis replacement procedures remains a topic of debate. Aim: This study aimed to assess the prevalence of secondary osteoarthritis following bipolar hip replacement, the need for revision to total joint replacement post-procedure, the functional status of patients in relation to radiological findings of joint degeneration, and the survivorship of bipolar hip replacements. Methods: Patients with orthopaedic oncology cases who underwent bipolar hip endoprosthesis replacement between 2006 and October 2021, with a minimum follow-up of six months, were included. Both clinical and radiological evaluations were carried out. The clinical evaluation utilised the Musculoskeletal Tumor Society (MSTS), Toronto Extremity Salvage Score (TESS), and modified Harris Hip Score (mHHS) systems. The radiological assessment focused on identifying acetabular erosion. Results: Forty eligible patients were identified. Radiological assessments revealed 21 patients (52.5%) with grade 0, 17 patients (42.5%) with grade 1, and 2 patients (5.0%) with grade 2 acetabular erosion. No patients exhibited grade 3 acetabular erosion. One patient (2.5%) required revision surgery from proximal femoral bipolar replacement to total hip replacement due to recurrent postoperative hip dislocation. There was no statistically significant difference in MSTS and mHHS scores but a significant difference in TESS scores. The ten-year implant survival rate was 77.8%, while the overall patient survivorship at ten years was 72.1%. Conclusion: Bipolar hip replacement is a durable limb-preserving reconstruction that can outlast patients' lifespans and is well-tolerated by oncology patients. The incidence of acetabular erosion and revision surgery is low. Despite radiological evidence of hip degeneration, functional status in patients is not significantly impacted.