Influence of the manufacturing process in performance concerning wear of total hip prostheses

Wear on joint prostheses is the leading cause of premature failure leading to revision surgery. Tests conducted on mechanical wear simulator show poor performance of prosthetic hip components manufactured using high-quality raw materials. Aiming to understand the phenomena that limit the longevity of joint prostheses, the manufacturing processes of two separate companies were investigated. Results obtained suggest that the lack of control during the manufacturing of the parts may be the reason for the low performance shown by the prostheses tested in the wear simulator. Out-of-roundness and roughness of finished surfaces is pointed out as the main manufacturing failure in production lines tested. Metal femoral heads showed deviations from roundness of up to 32.41 μm (σ = 8.869) and Ra = 0.295 ± 0.03, while acetabular cups in ultra-high molecular weight polyethylene showed deviations of up to 166.31 μm (σ = 53.982) and Ra = 0.031 ± 0.02. The out-of-roundness contributes to reducing the contact area between rolling surfaces, increasing tension in regions where premature wear on parts occurs with frequency. This study points out the common faults found in manufacturing processes and suggest changes to increase the longevity of total hip arthroplasty.