No differences in in vivo kinematics between six different types of knee prostheses

Purpose: The aim of this study was to compare a broad range of total knee prostheses with different design parameters to determine whether in vivo kinematics was consistently related to design. The hypothesis was that there are no clear recognizable differences in in vivo kinematics between different design parameters or prostheses. Methods: At two sites, data were collected by a single observer on 52 knees (49 subjects with rheumatoid arthritis or osteoarthritis). Six different total knee prostheses were used: multi-radius, single-radius, fixed-bearing, mobilebearing, posterior-stabilized, cruciate retaining and cruciate sacrificing. Knee kinematics was recorded using fluoroscopy as the patients performed a step-up motion. Results: There was a significant effect of prosthetic design on all outcome parameters; however, post hoc tests showed that the NexGen group was responsible for 80% of the significant values. The range of knee flexion was much smaller in this group, resulting in smaller anterior-posterior translations and rotations. Conclusion: Despite kinematics being generally consistent with the kinematics intended by their design, there were no clear recognizable differences in in vivo kinematics between different design parameters or prostheses. Hence, the differences in design parameters or prostheses are not distinct enough to have an effect on clinical outcome of patients.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin

In vivo three-dimensional kinematics of total elbow arthroplasty using fluoroscopic imaging

Higher complication rates and lower survivorship are still seen for total elbow arthroplasties compared to total knee and hip arthroplasties. This is partly due to polyethylene wear of the articular surface induced by excessive articular contact stress during elbow motion. The aim of this study was to dynamically evaluate in vivo three-dimensional elbow motion after total elbow arthroplasty. Twelve patients (15 elbows) who underwent operation with the Osaka University Model Total Elbow System were analysed using X-ray fluoroscopic imaging and a two-dimensional/three-dimensional registration technique, which could accurately estimate the three-dimensional spatial position of components. Valgus/varus angle and rotation between humeral and ulnar components showed wide variations among patients. Elbows with valgus angle and internal rotation >10° could induce edge-loading of the articular surface. Component alignment, articular configuration, and soft-tissue balance can affect the kinematics of total elbow arthroplasty