Open-wedge high tibial osteotomy with a slight valgus correction from neutral limb alignment achieves clinical improvements comparable with those for knees with varus deformity

Purpose The effect of open-wedge high tibial osteotomy (OWHTO) on the preoperative neutral alignment of the knee is unknown. The purpose of this study was to clarify the clinical outcome of OWHTO with neutral alignment, defined as within 4 degrees of varus. Methods This retrospective study included 72 knees with varus that underwent medial OWHTO. The knees were divided according to the preoperative hip-knee-ankle angle into a neutral alignment group (≤ 4° of varus alignment) and a varus alignment group (> 4° of varus alignment). The Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Forgotten Joint Score-12 (FJS-12) were evaluated preoperatively and during at least 2 years of follow-up postoperatively. Results There were no significant differences between the preoperative FJS-12 (17.9 versus 23.7; p = 0.16) and postoperative FJS-12 (57.3 versus 60.6; p = 0.52) or KOOS subscale scores ( p > 0.05) in the neutral alignment group or the varus alignment group. Each group had a mean change in the KOOS subscale scores that exceeded the minimum clinically important difference. Conclusion The short-term clinical results of OWHTO for neutral alignment were as favourable as those for varus malalignment. Level of evidence IV.