CHANGE OF TIBIAL ROTATION AFTER COMPUTER NAVIGATED KNEE REPLACEMENT

Abstract

We studied the change in the axial rotation of the tibia at different levels of knee flexion after Knee Replacement using navigation systems.

We reviewed the knee kinematic data of 36 consecutive patients (15 males and 21 females) who underwent elective knee replacement (Scorpio/Stryker) at King’s College Hospital. All data were generated using the navigation TKR trackers and software of a knee replacement system. All preoperative data obtained before any soft tissue release. We studied the tibial rotation at 30°, 60° and 90° of knee flexion. All operations were performed by consultant orthopaedic surgeons. We used the Wilcoxon non parametric two sample test for statistical analysis.

The average tibial internal rotation upon knee flexion was 9.4° preoperatively and was reduced to 5.3° (mean 7.3°) post operatively. Most of the change (80%) occurred within the first 30° of flexion (p< 0.001). Postoperatively 38% of the studied knees had the screw home mechanism preserved. 52.7% had a mixed pattern of both internal and external rotation of the tibia and three knees (8%) had a reversed rotation of the tibia. The abnormal screw home pattern was preserved in 16 of the postoperative joints (46%). One knee was found postoperatively with external tibial rotation in all flexion increments. The abnormal pattern of tibial rotation was not improved following a navigation arthroplasty.

We found that computer navigated TKR reduces significantly the tibial rotation and the replaced knee joint does not behave as a hinge joint. Pre-existing abnormal tibial rotation patterns were not improved postoperatively.