Abstract: BACKGROUND: Although high tibial osteotomy and unicompartmental knee arthroplasty are often used to treat unicompartmental knee osteoarthritis with varus deformity, whether there are differences in knee function at different postoperative periods and whether there are changes in knee parameters on preoperative and postoperative imaging still need further clinical study.  
OBJECTIVE: To compare the early clinical efficacy and the differences in knee imaging-related parameters of unicompartmental knee arthroplasty and open-wedge high tibial osteotomy in the treatment of unicompartmental knee osteoarthritis with varus deformity.
METHODS:  The medical record data of 126 patients with unicompartmental knee osteoarthritis with varus deformity were retrospectively analyzed, including 60 patients undergoing open-wedge high tibial osteotomy and 66 patients undergoing unicompartmental knee osteoarthritis with varus deformity. The Hospital for Special Surgery knee score was used to assess knee function preoperatively, 1 month postoperatively and the late follow-up between the two groups. Long-leg full-weight-bearing radiograph and anteroposterior and lateral radiograph of knee were taken before and after operation. The postoperative hip-knee-ankle angle, tibial posterior slope and patellar height were measured. The differences in the relevant imaging parameters of knee joint were compared between the two groups before and after operation.  
RESULTS AND CONCLUSION: (1) A total of 53 knees with high tibial osteotomy and 61 knees with unicompartmental knee arthroplasty were included in this study. The overall follow-up time was (26.29±3.84) months. (2) The Hospital for Special Surgery scores were higher in the unicompartmental knee arthroplasty group than those in the high tibial osteotomy group (P < 0.05). At the last follow-up, there was no significant difference in Hospital for Special Surgery scores between the two groups (P > 0.05). (3) Compared with preoperative data in the same group, the hip-knee-ankle angle and tibial posterior slope increased (P < 0.05), but patellar height decreased (P < 0.05) in the high tibial osteotomy group. Compared with preoperative data in the same group, hip-knee-ankle angle increased (P < 0.05), but tibial posterior slope decreased (P < 0.05), patellar height increased in the unicompartmental knee arthroplasty group, but the difference was not significantly different (P > 0.05). (4) Total hip-knee-ankle angle increased from (-5.68±3.48)° preoperatively to (0.69±0.69)° postoperatively. No significant difference was detected in hip-knee-ankle angle, tibial posterior slope and patellar height between the two groups before operation (P > 0.05). Significant differences were found in hip-knee-ankle angle, tibial posterior slope, patellar height, Δ hip-knee-ankle angle (postoperation-preoperation), Δ tibial posterior slope (postoperation-preoperation) and Δ patellar height (postoperation-preoperation) between the two groups after operation (P < 0.05). (5) It is concluded that the two groups of patients obtained satisfactory results in the late follow-up. However, the patients in the unicompartmental knee arthroplasty group had better knee function scores 1 month after surgery compared with the high tibial osteotomy group. In contrast, the high tibial osteotomy group was prone to postoperative patellar baja and increased posterior tibial slope. In the unicompartmental knee arthroplasty group, the patellar height did not change significantly after surgery, but the posterior tibial slope showed a significant decrease.

Key words: knee osteoarthritis, high tibial osteotomy, unicompartmental knee arthroplasty, tibial posterior slope, patellar height