Objective: We have developed a posterior-stabilized (PS) total knee prosthesis for Japanese patients. The purpose of this study was to examine in vivo kinematic characteristics of the new prosthesis, compared to a popular high-flexion PS prosthesis.
Methods: We analyzed 14 knees with the new PS prosthesis (group A) and 14 knees with a popular high-flexion PS prosthesis (group B) as a control group. Lateral radiographic knee images were recorded at five positions: extension standing, at 90° and at maximum flexion lunge, and at 90° and maximum flexion kneeling. The 3-dimensional position and orientation of the implant components were determined using model-based shape matching techniques.
Results: The maximum implant flexion angles tended to be greater in group A than group B, averaging 117°±8° and 109°±14° at maximum lunge (P=0.054), and 119°±7° and 110°±14° at maximum kneeling (P=0.061), in groups A and B, respectively. The femoral centers were located more posterior in group A than group B at the 90° flexion positions (P<0.001), although there were no significant differences at maximum flexion positions. The femoral center positions had a strong negative correlation with implant flexion angles at maximum lunge in group B, but not in group A.
Conclusion: Our newly developed total knee prosthesis designed for Japanese knees appears to perform comparably to a conventional high-flexion PS design with greater posterior femoral translation at 90° knee flexion.
