Superficial Medial Collateral Ligament Transection Sufficiently Increases Joint Space Width for Medial Meniscal Procedures During Medial Open‐Wedge High Tibial Osteotomy

Purpose To investigate the changes in minimum joint space width (mJSW) caused by superficial medial collateral ligament (sMCL) transection during open‐wedge high tibial osteotomy (OWHTO). Methods This study included consecutive patients with a diagnosis of medial unicompartmental knee osteoarthritis who were scheduled for OWHTO between September 2020 and August 2022. Intraoperative fluoroscopic evaluations of mJSW were performed under neutral, valgus stress, and varus stress positions in knee extension and 20° of flexion before sMCL transection, after transection, and after plate fixation. Changes in mJSW and increases in valgus stress were calculated and compared using analysis of variance. Linear regression analysis was performed to investigate the related factors for increased mJSW after transection. Results We included 44 knees in 43 patients in the final statistical analysis. The maximum mJSW occurred during valgus stress after sMCL transection at 20° of flexion and returned to baseline after plate fixation. Under the valgus stress condition, mean mJSW before transection was 5.1 ± 0.9 mm in extension and 5.5 ± 1.1 mm at 20° of flexion. It increased significantly after transection to 7.8 ± 1.4 mm ( P < .001) and 9.2 ± 2.1 mm ( P < .001), respectively. Regression analysis showed that increased mJSW after transection in extension positively correlated with the knee extension angle ( P = .032). Overall, mJSW increased with sMCL transection regardless of the preoperative condition. Conclusions Transection of the sMCL in OWHTO effectively enlarged the mJSW to 9.2 mm, which was 3.8 mm greater than that before transection, facilitating medial meniscal procedures. After plate fixation, the mJSW returned to pre‐transection levels. Level of Evidence Level Ⅳ, therapeutic case series.