Thigh pain in primary total hip arthroplasty: the effects of elastic moduli

Thigh pain after uncemented total hip arthroplasty (THA) remains a controversial topic. Our objective was to assess the effect of material composition in the development of thigh pain after primary THA. A cohort of 241 primary THAs was followed for a minimum of 2 years. All patients received identically shaped tapered cementless femoral components; the first half received a Cr-Co-Mo implant and the other half an identical implant made of Ti-6Al-4V. There were no statistically significant preoperative differences in the 2 component groups except that the percentage of blacks in the Cr-Co-Mo group was larger than in the Ti-6Al-4V group (26% vs. 14%; P <.05). The overall 1- and 2-year incidence of thigh pain was 9.5% and 8.7%, respectively. Implant composition was unrelated to reported thigh pain 1 and 2 years postoperatively. However, patients receiving larger versus smaller stems irrespective of material composition were more likely to report thigh pain at year 1 (relative risk = 4.68; 95% confidence interval = 1.41, 15.50). Thigh pain reported at year 2 was also higher in patients with larger versus smaller implants; however, this difference was not statistically significant (RR = 1.73; 95% CI = 0.68, 4.43). Material composition of this tapered stem design is unrelated to the incidence of thigh pain.