Intraoperatively accurate limb alignment after opening wedge high tibial osteotomy can be lost by large knee joint line convergence angle during surgery

Introduction The purpose of this study was to assess early postoperative loss of achieved correction and associated factors after opening wedge high tibial osteotomy (OWHTO). Materials and methods OWHTO was performed in 121 patients with osteoarthritis of the knee (mean age 66 years, 154 knees). Anteroposterior radiographs of the knee and full-length leg, and varus and valgus stress radiographs of the knee were taken, and the femorotibial angle (FTA), joint line convergence angle (JLCA), and medial proximal tibial angle (MPTA) were measured. The changes in the FTA, JLCA, and MPTA were defined as Delta FTA, Delta JLCA, and Delta MPTA. Results The Delta FTA and Delta JLCA at postoperative 0-2 days were - 1.8 +/- 1.2 degrees and - 1.9 +/- 1.4 degrees, respectively. The Delta FTA, Delta JLCA and Delta MPTA at postoperative 1-12 months were 0.9 +/- 1.3 degrees, 0.2 +/- 1.2 degrees and - 0.8 +/- 0.8 degrees, respectively. A positive correlation was found between Delta FTA and Delta JLCA at postoperative 0-2 days (rho = 0.642, P < 0.001) and at postoperative 1-12 months (rho = 0.402, P < 0.001). A negative correlation was found between Delta FTA and Delta MPTA at postoperative 1-12 months (rho = - 0.534, P < 0.001). A discrepancy in alignment represented by the FTA occurred in the supine radiographs between the day of surgery and postoperative 2 days. Multiple regression analysis suggested that postoperative JLCA on the day of surgery was the factor related to early postoperative change of the FTA. Conclusions This study demonstrated the early loss of achieved correction after OWHTO due to change of the JLCA, even if the accurate alignment is obtained intraoperatively.