The Ability to Achieve a Specific Target Angle on Weightbearing Radiographs After Valgus High Tibial Osteotomy for Medial Knee Arthritis Is Not Predictable

PURPOSE: Standing radiographs are commonly used to plan angular correction in valgus tibial osteotomy for varus gonarthrosis. Most clinical studies have reported postoperative alignment as overall averages or means. The purpose of this study was to compare the preoperatively planned angle of correction measured on weight-bearing radiographs to the follow-up angle measured on weightbearing radiographs in individual patients 6 weeks after surgery and to analyze factors that could potentially affect achieving the planned degree of surgical correction. Our objective was to analyze factors potentially affecting the accuracy and ability to achieve the preoperatively planned correction angle (the target angle) in the individual patient. METHODS: We studied 35 tibial osteotomies (13 Coventry closing wedge osteotomies and 22 Maquet barrel vault osteotomies) performed for varus gonarthrosis between 1981 and 2019 to determine how accurately the target angle, based on preoperative standing weight-bearing radiographs, was achieved according to the postoperative radiographs in each individual. We reviewed 35 knees in 34 patients who had complete pre- and postoperative radiographs for review. RESULTS: Overall, only 14 of 35 (40%) of the patients were corrected to within ± 2° of the planned target angle. Valgus tibial osteotomy based on preoperative weightbearing radiographs is unpredictable in its ability to achieve the target angle on postoperative weightbearing radiographs when using either the Coventry or the Maquet surgical technique. The tendency was to undercorrect with either of the techniques. Larger (greater than 10°) preoperative varus alignment did not make it more difficult to achieve the target angle. Male or female sex and body mass index had no effect on the ability to achieve the target angle. CONCLUSIONS: Valgus tibial osteotomy planning based on preoperative weightbearing is unpredictable in its ability to achieve the target angle on postoperative weightbearing radiographs. Overall, only 40% of our patients were corrected to within ± 2° of the planned target angle. The tendency was to undercorrect, with either the Coventry or the Maquet technique. Contrary to our hypothesis, larger preoperative varus alignment (greater than 10°) did not make it more difficult to achieve the target angle. The Coventry technique was as accurate as the Maquet technique. LEVEL OF EVIDENCE: Level IV.