Titanium and Cobalt-Chrome Cementless Femoral Stems of Identical Shape Produce Equal Results

This study of proximal porous-coated stems of identical shape, but with two types of stem materials (Ti alloy or Co-Cr alloy), was done to determine the differences, if any, in these stems in the following parameters: clinical and functional outcomes; the prevalence of thigh pain; the stem alignment and the stem-canal fill; cup position; the degree of periprosthetic bone loss; the prevalence of polyethylene liner wear and osteolysis; the incidence of aseptic loosening of acetabular and femoral components; and complication rates. In the Ti alloy group, there were 60 patients (70 hips) followed up for a mean of 6.4 years (range, 5–7 years) with a mean age at surgery of 45.3 years and a mean weight of 65.7 kg. In the Co-Cr alloy group, there were 60 patients (70 hips) followed up for a mean of 6.6 years (range, 5–7 years) with a mean age at surgery of 45.4 years and a mean weight of 66.8 kg. Harris hip scores did not differ and the prevalence of transient pain in the thigh was 5% with both stems. No acetabular or femoral component had aseptic loosening in either group. Loss of bone density in the calcar region was more severe in the Co-Cr group. The mean polyethylene linear wear per year was 0.15 mm (SD, 0.015) in the Ti group and 0.14 mm (SD, 0.013) in the Co-Cr group. No acetabular or femoral osteolysis was seen in any patient. The clinical and radiographic results of this study did not show any significant differences between the Ti and Co-Cr alloy femoral components; however, the Ti alloy femoral component retained greater periprosthetic bone as compared with a Co-Cr alloy femoral component.