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.
Keywords: Anterior femoral cortical window; bone incorporation; femoral canal cement removal; patient-specific jig; revision hip arthroplasty; trochanteric osteotomy.