Keitaro Yamamoto

Analysis of the kinematics of total knee prostheses with a medial pivot design.

Analysis of the kinematics of the FINE Total Knee System (Nakashima Medical, Okayama, Japan) revealed that the medial condyle is fixed and the lateral condyle shows lateral posterior movement and tibial internal rotation. Analysis of the kinematics of the ADVANCE Total Knee System (Wright Medical Technology, Arlington, Tenn) revealed that the medial condyle is fixed and the lateral condyle shows anterior movement in the early stage, changing thereafter to posterior movement. With regard to rotation, initial external rotation subsequently changes to internal rotation. Analysis of the kinematics of the ADVANTIM Total Knee System (Wright Medical Technology) revealed that the bicondyle shows posterior movement, subsequently changing to anterior and posterior movements. Thus, unlike the FINE or ADVANCE Total Knee Systems, the ADVANTIM Total Knee System shows internal rotation.

Primary and Revision Total Ankle Arthroplasty in Japan

Ankle arthrodesis is still performed more frequently than total ankle replacement for treatment of painful degenerative changes about the ankle joint. However, total ankle replacement has advanced during the last few decades and the clinical results have been improved substantially. Prosthesis design, preoperative planning, operative techniques to balance the joint, and postoperative evaluation of outcomes have made progress and have allowed surgeons to achieve good clinical results reliably. Since 2003, we started to use the three-component total ankle prosthesis with a mobile-bearing polyethylene insert. As a result, the FINE Total Ankle System is the most frequently employed ankle prosthesis in Japan today. It was designed to allow not only dorsiflexion and plantar flexion but also ±10° of internal and external rotation and ±3-mm anterior–posterior sliding along the mobile-bearing mechanism. We have investigated the in vivo kinematics of this three-component total ankle replacement. The preliminary results are promising and the prosthesis mimics the normal ankle kinematics during gait. Since 2006, the sliding medial malleolar osteotomy technique to balance varus malalignment, the use of a preoperative three-dimensional preoperative bone model based upon DICOM data obtained from a preoperative computed tomography scan, and dedicated patient-specific surgical instruments have played important roles in total ankle replacement surgery precision. However, we previously have limited the indication for total ankle replacement to only inflammatory arthritis due to low-demand physical activities, but more recently, we started expanding our indications to include osteoarthritis patients with higher daily activities. Even with the limited clinical experiences, the midterm results may be promising.