Controlled posterior condylar milling technique for unicompartmental knee arthroplasty minimises tibia resection during gap balancing: Short-term clinical results

Purpose: The purpose of this study was to demonstrate the clinical utility of controlled posterior condylar milling (CPCM) in gap balancing while minimally resecting the tibia during fixed-bearing unicompartmental knee arthroplasty (UKA).Methods: This study is a retrospective cohort study. Patients who underwent medial UKA for isolated medial compartment osteoarthritis with a minimum follow-up of 2 years were included. The patients were divided into two groups: the conventional group (n = 56) and the CPCM group (n = 66). In the CPCM group, the proximal tibia was resected at the level of the distal end of the subchondral bone. If the flexion gap was tighter than extension, the posterior condyle was additionally milled to adjust gap tightness. Standing knee X-ray and scanogram were used to evaluate alignment and tibia resection amount. Range of motion (ROM) and Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) scores were used to evaluate clinical outcomes.Results: The CPCM group showed significantly smaller tibia resection (3.6 +/- 1.9 mm) compared to the conventional group (5.2 +/- 2.7 mm) (p < 0.001). Postoperative ROM (133.0 +/- 8.3 degrees, 135.2 +/- 7.2 degrees, n.s.) and WOMAC (19.3 +/- 13.6, 23.6 +/- 17.7, n.s.) were not significantly different between the two groups. Postoperative periprosthetic fractures occurred in two patients in conventional group, while the CPCM group had no periprosthetic fractures.Conclusion: The CPCM technique may be a simple and useful intraoperative technique that can achieve minimal tibia resection and promising clinical outcomes while easily adjusting gap tightness between flexion and extension during medial fixed-bearing UKA. Level of Evidence: Level III.