Comparison of Clinical and Radiologic Outcomes Between Normal and Overcorrected Medial Proximal Tibial Angle Groups After Open-Wedge High Tibial Osteotomy

Purpose: To evaluate whether the overcorrected medial proximal tibial angle (MPTA) affects the clinical outcomes after open-wedge high tibial osteotomy (OWHTO) and to assess the correlation between knee joint line obliquity (KJLO) changes and the compensatory changes in the hip and ankle joints. Methods: Consecutive patients who underwent OWHTO from July 2006 to August 2015 were included. Exclusion criteria were bilateral OWHTO and follow-up of <2 years. The patients were retrospectively divided into 2 groups according to postoperative MPTA; a normal group (MPTA <95 degrees) and an overcorrected MPTA group (MPTA >= 95 degrees). The groups were compared with respect to the clinical and radiologic outcomes after OWHTO. Clinical parameters, including Japanese Orthopedic Association (JOA) score, Oxford Knee Score (OKS), and Knee Injury and Osteoarthritis Outcome Score (KOOS), were evaluated. Radiologic outcomes, including the hip-knee-ankle angle (HKA), joint line convergence angle (JLCA), MPTA, KJLO, ankle joint line obliquity (AJLO), and hip abduction angle (HAA), were evaluated preoperatively and at the final follow-up. Results: Ninety-four patients (normal group; n = 52, overcorrected group; n = 42) were included in this study. After OWTHO, the mean increases in HKA and MPTA were 11.0 degrees +/- 3.2 degrees and 10.4 degrees +/- 2.7 degrees, respectively, whereas the change in KJLO was only 3.7 degrees +/- 2.9 degrees. The mean AJLO (4.3 +/- 3.9 to -1.3 +/- 3.3, P < .001) and HAA (3.7 +/- 2.5 to -1.1 +/- 2.3, P < .001) significantly decreased after OWHTO. The mean postoperative MPTA in the overcorrected group was 96.9 degrees +/- 1.5 degrees, whereas the mean postoperative KJLO was only 3.1 degrees +/- 2.0 degrees. No significant differences were noted in all clinical scores between the groups at the final follow-up. Conclusions: A certain degree of overcorrected MPTA (>= 95 degrees) did not affect the clinical outcomes after OWHTO because of compensatory changes in the hip and ankle joints.