Contribution of the Bioball(TM) head–neck adapter to the restoration of femoral offset in hip revision arthroplasty with retention of a well-fixed cup and stem

PURPOSE: Failure to restore the femoral offset of the native hip is a potential cause of dysfunctional hip arthroplasty. The aim of this study was to report our experience of using a modular head–neck adapter in revision THA, specifically analyzing its usefulness as a tool to correct a slightly diminished femoral offset. MATERIALS AND METHODS: This was a retrospective single-center study including all hip revisions performed at our institution from January 2017 to March 2022 where the BioBall(TM) head–neck metal adapter was used. The preoperative and one year follow-up modified Merle d’Aubigné hip score was used to evaluate functional outcomes. RESULTS: Of a total of 34 cases included for revision, the head–neck adapter system was used specifically in six patients (17.6%) to increase femoral offset, retaining both the acetabular and femoral components. In this subgroup of patients, mean offset decrease after primary THA was 6.6 mm (4.0–9.1), equivalent to a mean 16.3% femoral offset reduction. The median modified Merle d’Aubigné score went from 13.3 preoperatively to 16.2 at one year follow-up. CONCLUSION: The use of a head–neck adapter is a safe and reliable procedure that may allow the surgeon to easily correct a slightly diminished femoral offset in a dysfunctional THA without the need to revise well-fixed prosthetic components.