Joint line obliquity after lateral closing-wedge high tibial osteotomy does not adversely affect clinical and radiological outcome: a 5-year follow-up study

PURPOSE: To analyze the association between change in knee joint line obliquity (KJLO) and patient-reported outcome, radiological progression of osteoarthritis, and surgical survival after lateral closing-wedge high tibial osteotomy (HTO). METHODS: A cohort of 180 patients treated in one single hospital with lateral closing-wedge HTO was examined. KJLO was defined by the medial proximal tibial angle (MPTA). To assess the association between KJLO and patient-reported outcome, radiological progression of osteoarthritis, and surgical survival, patient groups were defined: I, postoperative MPTA < 95.0°; II, postoperative MPTA ≥ 95.0°; A, MPTA change < 8.0°; B, MPTA change ≥ 8.0°. Propensity score matching was used for between-groups (I and II, A and B) covariates matching, including age, gender, preoperative lower limb alignment, preoperative medial joint space width (mJSW), preoperative Western Ontario and McMaster Universities osteoarthritis Index (WOMAC) score, wedge size, and postoperative follow-up time. Patient-reported outcome was assessed by the WOMAC questionnaire, radiological progression of osteoarthritis by mJSW and Kellgren–Lawrence (KL) grade progression (≥ 1) preoperatively and at follow-ups (> 2 years). Failure was defined as revision HTO or conversion to knee arthroplasty. RESULTS: After propensity score matching, groups I and II contained 58 pairs of patients and groups A and B contained 50 pairs. There were no significant differences in postoperative WOMAC score or surgical failure rate between groups I and II or between groups A and B (p > 0.05). However, the postoperative mJSW was significantly lower in group I than group II (3.2 ± 1.6 mm vs 3.9 ± 1.8 mm; p = 0.018) and in group A than group B (3.0 ± 1.7 mm vs 3.7 ± 1.5 mm; p = 0.040). KL grade progression rate was significantly higher in group I than group II (53.4% vs 29.3%; p = 0.008) and in group A than group B (56.0% vs 28.0%; p = 0.005). CONCLUSION: Increased KJLO (postoperative MPTA ≥ 95.0°) or MPTA change ≥ 8.0° after lateral closing-wedge HTO does not adversely affect patient-reported outcome, radiological progression of osteoarthritis, or surgical survival at an average 5-year follow-up. LEVEL OF EVIDENCE: III, retrospective cohort study.