Is the Bone-bonding Ability of a Cementless Total Hip Prosthesis Enhanced by Alkaline and Heat Treatments?

Abstract

Cementless total hip arthroplasty (THA) implants using alkaline and heat treatments were developed to enhance bone bonding. Although bone-bonding ability of the alkali- and heat-treated titanium surface has been demonstrated in animal studies, it remains unknown whether it enhances or provides durable bone bonding in humans. We therefore (1) determined long-term survivorship, function, and radiographic signs of failure of fixation of alkali- and heat-treated THA implants; and (2) histologically examined their bone-bonding ability in two human retrievals. We retrospectively reviewed 58 patients who underwent 70 primary THAs, of whom 67 were available for minimum followup of 8 years (average, 10 years; range, 8-12 years). Survival rate was calculated. Hip function was evaluated using the Japan Orthopaedic Association (JOA) hip scores, and radiographic signs of implant failure were determined from anteroposterior radiographs. Two retrieved implants were investigated histologically. Using revision for any reason as the end point, the overall survival rate was 98% (95% confidence interval, 96%-100%) at 10 years. The patients' average JOA hip scores improved from 47 points preoperatively to 91 points at the time of the last followup. No implant had radiographic signs of loosening. Histologically we observed bone in the pores 2 weeks after implantation in one specimen and apparently direct bonding between bone and the titanium surface in its deep pores 8 years after implantation. Cementless THA implants with alkaline and heat treatments showed a high survival rate. Further study is required to determine whether the treatment enhances direct bone bonding.