Lack of evidence for an effect of joint line obliquity after medial opening wedge high tibial osteotomy: A 12-year single-centre retrospective study.

PURPOSE: Large correction in opening wedge high tibial osteotomy (HTO) may lead to excessive joint line obliquity (JLO). This study hypothesized that the presence of an oblique joint line, defined by knee joint line obliquity (KJLO) > 5° and/or medial proximal tibial angle (MPTA) > 94°, was associated with poorer functional outcomes and lower survival rates following HTO at long-term follow-up. METHODS: This retrospective study included 83 patients who underwent a medial opening wedge HTO with at least 5 years of follow-up. Complete pre- and postoperative radiographic parameters (hip-knee-ankle angle [HKA], MPTA, lateral distal femoral angle [LDFA], KJLO, joint line convergence angle [JLCA]) and functional outcomes (Knee injury and Osteoarthritis Outcome Score [KOOS], International Knee Society Score [IKS], Subjective Knee Value [SKV]) were analysed. Excessive JLO was defined by a KJLO ≥ 5° and/or an MPTA > 94°. An independent Student's t test was then performed to compare functional scores and angular measurements between groups. Functional results and revision-free survival were analysed according to JLO, using the Kaplan-Meier method for survival analysis. The mean follow-up was 12.3 ± 3.3 years (5-19). RESULTS: The HKA, MPTA, JLCA and KJLO angles varied significantly (ΔHKA = 7.8° ± 3.7, p < 0.001). Functional scores showed no significant difference between patients with or without JLO. Five- and 10-year survival rates were 86% and 71%, respectively, with no difference based on JLO (p = 0.500). Smoking, age > 55 years, Ahlbäck stage III osteoarthritis and out-of-target postoperative alignment (HKA < 180° or > 183°) were identified as risk factors for conversion to total knee arthroplasty in multivariate Cox regression analysis. CONCLUSION: This retrospective analysis found no significant association between excessive JLO (KJLO ≥ 5° and/or MPTA > 94°) and either survival or functional outcomes after medial opening wedge HTO at a mean follow-up of 12 years. Factors negatively influencing survival after HTO were smoking, age > 55 years, advanced osteoarthritis and out-of-target postoperative alignment. These findings should be confirmed by larger series. LEVEL OF EVIDENCE: Level III.