One of the objectives of total hip arthroplasty is to restore femoral and acetabular combined anteversion. It is desirable to reproduce both femoral and acetabular antevesions to maximize the acetabular cup fixation coverage and hip joint stability. Studies investigated the resultant of implanted femoral stem anteversion in western populations showed that the implanted femoral stems had only a small portion can meet the desirable femoral anteversion angle1, and anteversion angle increases after the implantation of an anatomical femoral stem with anteverted stem neck comparing to anatomical femoral neck2. The purpose of this study was to anatomically measure the anteversion angular difference between metaphyseal long axis and femoral neck in normal Chinese population. The metaphyseal long axis represents the coronal fixation plane of modern cementless medial-lateral cortical fitting taper stem. This angular difference or torsion Δ angle provides the estimation of how much the neck antevertion angle of femoral stem would be needed to match for desirable anatomical femoral neck version. 140 (77 male and 63 female) anonymous normal adult Chinese CT data with average age of 54.6 (male 54.6, female 54.5, P=0.95) were segmented and reconstructed to 3D models in Trauson Orthopeadic Modeling and Analytics (TOMA) program. Femoral head center, femoral neck axis and center point of diaphyseal canal 100mm bellow calcar formed the femoral neck plane. The metaphyseal stem implantation plane was determined by the center point of medial calcar, proximal canal central axis formed by femoral neck plane and the center point of diaphyseal canal 100mm bellow calcar. [Fig. 1] The angle between two planes was the torsion Δ angle between femoral placement plane and anatomical femoral neck. [Fig. 2] The torsion Δ angles were measured for all 140 cases. The traditional anteversion angle for anatomical femoral neck was also measured by Murphy's method. Student T test was perform to compare the angles for male and female. The 98% confidence level was assumed.Introduction
Methods
