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An oblique osteotomy is better for subtrochanteric shortening in total hip arthroplasty for high hip dislocation: a mechanical comparison of four techniques

Background: Subtrochanteric femoral shortening is used during total hip arthroplasty for high hip dislocation in developmental dysplasia of hip patients. Methods: We mechanically tested the stability of various commonly used subtrochanteric osteotomy techniques. As the equivalent of a femoral stem placed in a shortened femur without any stable fixation at the osteotomy line, 2 polyvinylchloride pipes were loosely intertwined. 4 different osteotomies (Z-subtrochanteric osteotomy, oblique-45° osteotomy, double Chevron-90° and 120° subtrochanteric osteotomy) were simulated. Torsional and axial loads were applied, and torsional stiffness was calculated for each test model. Results: Z, double Chevron-90° and 120° subtrochanteric osteotomy models demonstrated lower mean torsional stiffness than oblique-45° osteotomy. With the highest torsional stiffness oblique-45° provides the best stability for treatment of high dislocation hips when a subtrochanteric osteotomy is added. Conclusions: This matches our previous clinical experience. Oblique osteotomy may also provide higher contact surfaces in the osteotomy lines to promote bone healing.