Knee motion in total knee arthroplasty. A roentgen stereophotogrammetric analysis of the kinematics of the Tricon-M knee prosthesis.
The three-dimensional kinematics of the Tricon-M knee prosthesis during active knee flexion and extension were recorded in 11 patients with arthrosis or rheumatoid arthritis using roentgen stereophotogrammetric analysis. Twenty-three normal knees constituted the control group. The prosthetic knees displayed the same degrees of freedom regarding rotational and translational movements as the normal knees, although the kinematics were different. A combination of internal rotation, abduction, and lateral translation of the tibia was recorded during flexion, and the reversed movements were recorded during extension. During the first 25 degrees of flexion, these movements were small, reflecting the high congruency between the articular surfaces, while beyond 25 degrees they increased. The normal knees displayed a combination of internal rotation, adduction, and medial translation of the tibia during flexion and the reversed movements during extension. The prosthetic knees also exhibited an increased posterior displacement during increasing flexion when compared with the normal knees. There was a correlation between the positioning of the femoral component in the sagittal plane and the recorded anterior/posterior translations. In conclusion, the kinematics of the Tricon-M knee prosthesis significantly differ from the normal knee, probably because of the design of the prosthesis and the absence of the cruciate ligaments.