The anterior femoral cortical window as an alternative to an extended trochanteric osteotomy in revision hip arthroplasty surgery: the evolution of the surgical technique and outcomes in 22 consecutive cases

BACKGROUND: The anterior femoral cortical window is an attractive alternative to the extended trochanteric osteotomy when removing femoral cement in revision hip arthroplasty. CT-based additive manufacturing technology has now permitted the creation of patient-specific instrumented (PSI) jigs to facilitate this. The jig simplifies creation of the window, potentiating medullary exposure through an optimally-sized window and therefore cement removal. Between 2006 and 2021 this technique was used in 22 cases at a regional hospital in New Zealand (mean age 74; range 44 to 89 years). 16 cases were for aseptic loosening and 6 for infection. We describe the technique and our case series. Bone incorporation for the cortical window was assessed in all cases using CT imaging. Oxford scores were obtained at a minimum of 6 months after revision surgery. Of the 6 septic cases 5 went onto successful stage-2 procedures, the other to a Girdlestone procedure. RESULTS: The mean rectangular shaped window size was 8 × 1.5 cm and in each case, this provided adequate intramedullary access. On average at minimum 5 months post-surgery, 84% bone incorporation of the cortical window occurred on CT (40-100%). The functional outcome Oxford hip score was 37 (range 22-48) for 10 cases. There were 2 cases with femoral component subsidence which then stabilised. CONCLUSIONS: This technique description and retrospective case series has shown the effectiveness of removing a distal femoral cement mantle in revision hip arthroplasty using an anterior femoral cortical window, recently optimised using a PSI jig. This technique is a straightforward alternative to a trochanteric osteotomy. Reliable bony integration of the cortical window occurred and functional outcomes were comparable with the mean score for revision hip procedures reported in the New Zealand Joint Registry.