Abstract
Fixed and mobile-bearing in total knee arthroplasty are still discussed controversially. In this article, biomechanical and clinical aspects in both fixed and mobile-bearing designs were reviewed. In biomechanical aspect, the mobile-bearing design has proved to provide less tibiofemoral contact stresses under tibiofemoral malalignment conditions. It also provides less wear rate in in-vitro simulator test. Patients with posterior stabilized mobile-bearing knees had more axial tibiofemoral rotation than patients with posterior stabilized fixed-bearing knees during gait as well as in a deep knee-bend activity. However, in clinical aspect, the mid-term or long-term survivorship of mobile-bearing knees has no superiority over that of fixed-bearing knees. The theoretical advantages for mobile-bearing design to provide a long-term durability have not been demonstrated by any outcome studies. Finally, the fixed-bearing design with all-polyethylene tibial component is suggested for relatively inactive, elder people. The mobile-bearing design is suggested for younger or higher-demand patients due to the potential for reduced polyethylene wear and more normal kinematics response after joint replacement. For younger surgeon, the fixed-bearing design is suggested due to less demand for surgical technique. For experienced surgeon, one familiar surgical protocol and instrumentation is suggested rather than implant design, either fixed-bearing or mobile-bearing.
Highlights
Total knee arthroplasty (TKA) has become a standard operative procedure to relieve pain and restore function in patients with osteoarthritis or rheumatoid arthritis
Current total knee prosthesis (TKP) devices can be subdivided into two groups based on different fundamental design principals: fixed-bearing knees, where the polyethylene tibial insert locked with tibial tray, and mobile-bearing designs which facilitate movement of the insert relative to the tray [1]
Fixed-bearing prosthesis with a high conformity bearing surface provides low contact stress, but produces high torque at the bone-implant interface predisposing to component loosening
Summary
Total knee arthroplasty (TKA) has become a standard operative procedure to relieve pain and restore function in patients with osteoarthritis or rheumatoid arthritis. We investigated the contact stresses in tibial polyethylene component of fixed and mobile-bearing knee prostheses under medial-lateral, anterior-posterior maltranslations and in internal-external malrotations of tibiofemoral joint [18]. Patients with any design of knee prostheses (fixed-bearing or mobile-bearing) had smaller femoral rollback as well axial rotation than normal knees during gait and a deep knee bend. At a minimum of 15 years follow-up for cemented rotating-platform mobile-bearing TKA, Callaghan et al [38] reported no knee was revised because of loosening, osteolysis, or wear in their series of 37 patients (53 knees). The theoretical advantages for mobile-bearing design to provide a long-term durability have not been demonstrated by any outcome studies
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