A finite element analysis of stability of subtrochanteric oblique osteotomy in total hip arthroplasty for type IV developmental dysplasia of the hip

Abstract

Objective Finite element analysis was used to evaluate the effects of different angles of subtrochanteric osteotomy on the bone and prosthesis stress and the stability of the osteotomy surface. Methods CT scan of A 50 year old female patient with Crowe type developmental dysplasia of the hip (DDH) was subjected to the CT scan, the femur data were extracted, the digital model was established, components were digitalized, and the operation was simulated. The osteotomy was done under the rotor downward inclination of 30°, 45°, 60°, 90°. The affected lateral single leg standing was developed by mechanical loading. The stress distribution, relative displacement and measurement of each model were detected. Results The stress distribution of the femoral and hip replacement was different from that of the whole femur. After the subtrochanteric osteotomy, the stress concentration appeared in both the prosthesis and the femur, and the stress concentration area of the femur was mainly located at the distal end of the osteotomy. From the angle of the displacement of the osteotomy plane, the relative displacements after 30°, 45°, 60° and 90° osteotomy were 101, 29, 48, and 133 μm respectively. The rotation and axial displacement of the osteotomy face were balanced when the inclination was 45°, and the overall displacement was minimum. Conclusion The finite element analysis shows that the subtrochanteric osteotomy can cause the stress concentration of the distal femur of the osteotomy. Because of the small overall displacement, the tilt of the rotor under 45° osteotomy is expected to obtain the best stability of the osteotomy surface. Key words: Developmental dysplasia of the hip; Total hip arthroplasty; Subtrochanteric oblique osteotomy; Finite element analysis