The Zweymüller primary stem is a reliable, effective, and less invasive implant in revision hip arthroplasty for Paprosky type I and II defects.

Aims: Revision hip arthroplasty for femoral stem loosening remains challenging due to significant bone loss and deformities requiring specialized revision stems. The aim of this study was to evaluate the clinical and radiological outcomes, and survival, of a consecutive series of femoral revisions performed using a primary cementless stem with tapered geometry and rectangular cross-section at medium-term follow-up.

Methods: We retrospectively evaluated 113 patients (115 hips) with intraoperative Paprosky type I (n = 86) or II (n = 29) defects, who underwent femoral revision with Alloclassic Zweymüller SL stem for one-stage aseptic revision or two-stage septic revision from January 2011 to December 2020. The mean follow-up was 77.9 months (SD 33.8). Nine patients were lost to follow-up (deceased or not available), leaving 104 patients (106 hips) for the clinical and radiological analysis. Clinical assessment was performed with Harris Hip Score (HHS) and visual analogue scale (VAS) before surgery and at final follow-up.

Results: There were 60 males and 53 females with a mean age at time of surgery of 71.2 years (SD 12.6). The mean HHS and VAS significantly improved at final follow-up, from 33.7 (SD 13.0) and 5.8 (SD 1.8) preoperatively to 66.4 (SD 16.8) and 2.1 (SD 1.8) postoperatively, respectively (p = 0.001 and p = 0.001). Overall, 28 patients (25%) showed non-progressive radiolucent lines at the level of proximal femur without radiological or clinical signs of loosening. One patient had a recurrence of periprosthetic joint infection after a two-stage procedure requiring re-revision surgery. One patient underwent exchange of modular components for recurrent dislocation, and another case of dislocation was treated conservatively. The survival with aseptic loosening as endpoint was 100%, while stem revision for any reason was 99.1% at up to 152 months' follow-up.

Conclusion: Alloclassic Zweymüller SL primary stem showed favourable medium-term results and survival for revision total hip arthroplasty in Paprosky type I and II defects.