Effect of proximal femoral bone support on the fixation of a press-fit noncemented total hip replacement femoral component

Purpose: Proximal femoral bone loss is a common challenge in revision hip arthroplasty. In this study, in vitro fixation of a non-cemented, rectangular, dual-tapered, press-fit femoral component designed to achieve metadiaphyseal fixation was analyzed using an accelerated proximal femoral bone loss model to assess the potential use in revision cases. Methods: The press-fit Alloclassic (TM) femoral stem was implanted in ten cadaveric femurs and tested under cyclic biomechanical loading in an intact state, and then again after sequential proximal femoral bone resections, simulating increasing amounts of bone deficiency. Anterior-posterior and medial-lateral interface motions were measured at the distal stem tip throughout loading. Results: Three specimens remained stable throughout testing, with initial and peak per-cycle motions of less than 50 mu m. Six specimens were destabilized under loading with higher per-cycle motions, specifically at the distal stem tip during peak loading in the anterior-posterior direction, with motions of 78 +/- 69 mu m, compared to 12 +/- 9 mu m in the stable specimens (P<.05). Total migration of the destabilized specimens was also significantly higher, specifically at the proximal stem tip in the medial-lateral direction, with migrations of 101 +/- 34 mu m (P<.05) and at the distal stem tip in the anterior-posterior direction, with migrations of 155 +/- 179 mu m (P<.05), compared to 33 +/- 12 mu m and 13 +/- 11 mu m for the stable specimens. Conclusion: The results indicate that when strong initial fixation is achieved, long-term success is possible given substantial proximal femoral bone loss.