Abstract
Background
Restoration of physiologic rotational kinematics after total knee replacement has been difficult to achieve using modern dual M/L radius knee designs. This study was undertaken to determine whether a change in femoral shape substituting for the effect of the menisci in load sharing and motion accommodation would result in more normal rotational post arthroplasty kinematics.
Methods
17 knees reconstructed more than twelve months previously with a tricompartmental cemented knee replacement using a single F/E radius, miniscal substituting, a fixed bearing total knee were studied fluoroscopically while performing closed chain activities. The patients were studied during level gait, deep knee bending, rising from a chair, and kneeling. Images were converted from 2 to 3d and joint kinematics were measured using edge recognition softwear.
Results
The highest levels of physiologic rotation were demonstrated during kneeling and squatting. The average knee flexion attained was 133 ± 6 degrees. Internal tibial rotation around a medial tibial axis was present in each knee. The average physiologic rotation observed was 13 degrees in both maneuvers. There was no visualized unloading or instability seen in any of the knees.
Conclusions
These results suggest that incorporating a single M/L radius in both the femoral component and the tibial bearing can memic the function of the menisci in the normal knee: providing for unrestricted rotation while enhancing load distribution across the articular surface of the knee joint.
