Changes in patellar baja progress until 3 months after medial open-wedge high tibial osteotomy

Purpose The purpose of this study was to evaluate sequential patellar height changes as well as the factors leading to these changes after medial open-wedge high tibial osteotomy (MOWHTO). Methods The study cohort constituted 37 knees from 36 patients who underwent MOWHTO for varus knee. The Caton–Deschamps index (CDI) for patellar height was measured preoperatively and at 2 weeks and 3, 6, and 12 months postoperatively. The factors related to sequential changes in patellar height were evaluated. Results Significant differences were observed between preoperative CDI and postoperative CDI at all time points (p < .05). Two-week postoperative CDI and postoperative CDI at 3,6,12-months was also significantly different (p < .05). The only significant factor for the change in patellar height between preoperative CDI and postoperative CDI at 2-weeks and 12-months was the change in the Δ medial proximal tibial angle (ΔMPTA) (postoperative MPTA–preoperative MPTA). We could not identify the factor that affected the change in patellar height change from 2-weeks postoperatively. Conclusion The change in patellar height continued sequentially until at least 3 months postoperatively. ΔMPTA was associated with the change in patellar height at 2 weeks postoperatively compared with preoperatively; however, no factors associated with the change in patellar height from 2 weeks postoperatively to 3, 6, and 12-months postoperatively were identified.