Abstract
BACKGROUND: To provide normal knee function, a total knee arthroplasty (TKA) implant with an anatomic surface shape and an adequate sagittal position has been developed. However, it is unclear how this modern implant influences knee joint kinetics and muscle activation during a gait. Therefore, we evaluated this modern TKA prosthesis and compared it with a conventional TKA prosthesis for gait analysis in terms of kinetics and muscle activation. METHODS: Subjects were patients (>60 years of age) with knee osteoarthritis who had undergone unilateral TKA. Twelve patients received the modern TKA prosthesis (group modern), and the other 12 patients received a conventional TKA prosthesis (group conventional). The subjects underwent motion capture analyses with a force plate, and kinematic and kinetic data were acquired from a 10-m gait test. Electromyography data of 6 lower limb muscles were simultaneously collected during the gait test. The 2 groups were compared using unpaired t-tests. RESULTS: In group modern, gait speed was faster, step length was longer, and the knee flexion angle during the initial stance phase was larger. Furthermore, in group modern, the maximum knee extension moment was higher; however, the quadriceps muscle activity tended to be lower than that in group conventional. CONCLUSIONS: Gait characteristics of group modern were more like a normal gait, and knee joint extension moments were greater. This finding indicates that the quadriceps muscles can be more effectively activated, and the anterior stability function of the anterior cruciate ligament may be reproduced with the shape of the modern implant.