Coronal tibiofemoral subluxation is a risk factor for postoperative overcorrection in high tibial osteotomy

Background: Severe tibiofemoral (TF) subluxation > 10 mm is a contraindication for high tibial osteotomy (HTO). However, the relationship between the degree of preoperative TF subluxation at < 10 mm and postoperative radiographic/clinical outcomes remains unclear. Methods: Sixty-seven patients who underwent open wedge HTO with a planned postoperative mechanical femorotibial angle (mFTA) of three degrees valgus were retrospectively studied. The minimal subluxation (MIN) group included 39 patients with TF subluxation < 5 mm, while the moderate subluxation (MOD) group included 28 patients with TF subluxation of five to 10 mm. The preoperative and one-year postoperative mFTA, TF subluxation, medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), preoperative Kellgren-Lawrence (K-L) grade and varus-valgus laxity were evaluated. Clinical scores and pain visual analogue scale (VAS) were also analyzed. Results: The mean preoperative TF values in the MIN and MOD groups were 3.1 +/- 1.0 mm and 6.7 +/- 1.6 mm (mean +/- standard deviation, p < 0.001), respectively, with no significant difference in K-L grades. The MIN group demonstrated a significantly smaller varus preoperative mFTA (p < 0.001), larger MPTA (p = 0.011), smaller JLCA (p = 0.004), and less varus laxity (p = 0.023). Postoperative TF subluxation, MPTAs, and JLCAs did not differ significantly between the two groups, while the postoperative mFTA was significantly different (p = 0.001), with unintended overcorrection in the MOD group. No significant difference in clinical scores and VAS were observed. Conclusions: After HTO, compared to patients with TF subluxation < 5 mm, patients with TF subluxation of five to 10 mm were more likely to demonstrate unintended valgus overcorrection on one-year postoperative radiography. (C) 2019 Elsevier B.V. All rights reserved.