Limited medial posterior capsular release increases the intraoperative medial component gap while maintaining the joint varus angle at extension in posterior-stabilized total knee arthroplasty.

Abstract

There is a lack of robust evidence for the magnitude of the effects of posterior capsular release (PCR) on intraoperative component gaps during total knee arthroplasty (TKA). The purpose of the present study was to quantify and compare the effects of partial versus full PCR on the intraoperative component gaps at various degrees of flexion during posterior-stabilized TKA. Full PCR was performed on 39 consecutive cases (full PCR group), and partial PCR (the medial side up to and including the intercondylar notch) was performed on the subsequent 39 consecutive cases (partial PCR group) during posterior-stabilized TKA using the measured resection technique for varus knee osteoarthritis. Medial component gaps and varus angles at 0°, 10°, 45°, 90°, and a maximum of flexion were measured with a tensor device before and after the PCR. Differences between the two groups in post-release medial component gap increase and post-release joint varus angle increase were assessed using a t test. Pre- to post-release medial component gaps and joint varus angles in each group were compared using a paired samples t test. In both groups at 0° and 10° of flexion, post-release medial compartment gaps were significantly greater than pre-release gaps (all P < 0.001). At 45°, 90° and maximum flexion, the medial compartment gap increase did not exceed the minimal detectable change in either group. At 0° and 10° of flexion, there was no significant difference in post-release medial compartment gap change between the two groups. In the full PCR group, post-release joint varus angles at 0° of flexion were significantly greater than pre-release angles (P < 0.001), while there was no significant pre- and post-release difference in the partial PCR group. The change in post-release joint varus angles at 0° of flexion was significantly greater in the full PCR group than in the partial PCR group. Both full and partial PCR show similar clinical usefulness for increasing the medial component gap at extension and reducing component gap mismatch. A partial PCR can be used to avoid increasing joint varus angles at 0° of flexion. Level 2 (prospective comparative study).