Abstract
To restore a physiologic kinematic is one of the goals of total knee replacement (TKR). This study compared the intra-operative registration of the knee kinematics during standard, navigated TKR performed either with a well validated floating platform design with posterior cruciate (PCL) preservation, or with a newly designed TKR with a rotating platform and PCL substitution. It was hypothesised that this new design will significantly alter the kinematic recorded after TKR implantation in comparison to the conventional design.
A standard navigation software has been modified to allow the intra-operative registration of the knee kinematic during a flexion-extension movement before and after implantation. Kinematic registration was performed twice: 1) before any bone resection or ligamentous balancing; 2) after fixation of the final implants. Post-operative kinematic was classified as following: 1) Occurrence of a normal femoral roll-back during knee flexion, no roll-back or paradoxical femoral roll-forward. 2) Occurrence of a normal tibial internal rotation during knee flexion, no tibial rotation or paradoxical tibial external rotation. 20 patients were operated on with either the PCL preserving or sacrificing designs. The kinematic behaviour was compared on a patient specific basis before and after the TKR.
About femoral roll-back, 54% had a normal femoral roll-back during knee flexion after total knee replacement, 13% had no significant roll-back and 33% had a paradoxical femoral roll-forward. About tibia rotation, 65% had a normal tibia internal rotation during knee flexion, 16% had no significant tibia rotation and 19 had a paradoxical tibia external rotation. There was no difference of repartition between the two designs.
The new software allows actually validating new designs of a TKR in terms of intra-operative kinematic behaviour.
