TKA Development in Japan: General Remarks

The development of TKA in Japan began in the 1970s, and subsequently many implants have been clinically applied. At that time, implants in Europe and the United States were being developed in accordance with Western lifestyles, so acquiring deep flexion was not a vital postoperative goal. Therefore, efforts have been made in Japan to devise a shape that does not compromise durability when the knee joint is moved to achieve deep flexion. In addition, there have been developments to increase size variations and adjust the lateral/anterior components using Japanese human bone shape data, to address the issue of the unsuitable implant sizes for Japanese bone structure. It is also noteworthy that global-leading design improvements have been made to obtain kinematics that closely resemble biological kinematics. This section outlines the development of representative TKA in Japan.