Survivorship of high tibial osteotomy: comparison between opening and closing wedge osteotomy

Background: High tibial osteotomy (HTO) is frequently used to treat varus osteoarthritis (OA) in younger patients with the goal of delaying the need for total knee arthroplasty (TKA). While it has been reported that the results of TKA following HTO are worse than those in patients without prior knee surgery, the influence of osteotomy technique (medial opening wedge versus lateral closing wedge) has not been explored. The purpose of this study was to retrospectively compare the results of closing wedge and opening wedge and assess which technique led to lower risk of failure. Methods: A total of 141 knees with indication for TKA, which were previously submitted to HTO (24 opening wedge and 117 closing wedge), were included in this study. At the time of TKA, the Knee Society Score and Knee Society Score function were evaluated. Additionally, the lower limb mechanical angle and Blackburn-Peele index were retrospectively retrieved. The relative risk of failure of the two techniques was compared using the Cox proportional hazard regression model. The impact of the patient’s age at HTO on the time to convert to TKA was also analyzed. Results: There was no significant difference in Knee Society Score and Knee Society Score function scores based on osteotomy technique at the time of the TKA. The survival curves were significantly different between the two groups (P<0.001) and patients who underwent opening wedge HTO had a 3-fold higher risk of failure (relative risk =2.91, P<0.001). There was a significant but weak linear correlation between higher age at HTO and lesser time until the TKA (r=0.326, P<0.001). Conclusions: Opening wedge HTO was associated with a 3-fold increase in risk of conversion to TKA, when compared to the closing wedge HTO surgical technique. These results are important for HTO surgical planning and may assist the orthopaedic surgeon in the decision between opening wedge or closing wedge HTO.