Objective: The patellar tracking is an important factor that affect range of motion after total knee arthroplasty (TKA). Intraoperative patellar maltracking during TKA can be improved by performing lateral release. We hypothesized that TKA with patellar maltracking after undergoing lateral release can increase intraoperative range of flexion.

Material and Method: A prospective study was conducted on 110 knees that underwent computer assisted TKA. The patellar tracking was assessed with no thumb test technique. Fifty-two knees were classified into negative no thumb test group, and 58 knees were classified into positive no thumb test group. The positive no thumb test group further received lateral release with outside to inside technique. The range of flexion was recorded before and after final implantation in both groups, and recorded after lateral release in positive no thumb test group.

Results: After final implantation, the negative no thumb test group had significant greater flexion angle than the positive no thumb test group (128.20° and 123.90°). The range of flexion after performing the lateral release in positive no thumb test group increased the flexion up to 127.60°. Thus, there was no significant difference from the negative no thumb test group (128.20°). After the lateral release was performed, the flexion angle had significantly increased by 3.70°.

Conclusion: The results indicated that intraoperative lateral release in patellar maltracking can improve range of flexion in computer assisted TKA.

Keywords: Lateral release, Patellar maltracking, Computer assisted total knee arthroplasty