Predictive Factors for Lateral Hinge Fracture in Medial Closing Wedge Distal Femoral Osteotomy

Background: Recent studies have reported that lateral hinge fracture (LHF) has a negative effect on bone healing at the osteotomy site after medial closing wedge distal femoral osteotomy (MCDFO). However, limited evidence exists in the literature regarding the predictive factors for LHF in MCDFO. Hypothesis: A large medial closing gap and a lateral hinge position in the supracondylar area would increase plain radiography–based and/or computed tomography (CT)–based LHF in MCDFO. Study Design: Case control study; Level of evidence, 3. Methods: We retrospectively evaluated 67 knees of 53 patients (mean age, 37.4 ± 16.9 years) who underwent MCDFO between May 2009 and June 2021. The surgical indications for MCDFO were genu valgum deformity combined with either lateral compartment osteoarthritis or recurrent patellar dislocation. The presence of LHF was evaluated based on immediate postoperative plain radiography and CT scans. The predictive factors for LHF in MCDFO were investigated using multivariate logistic regression analysis. Results: LHFs were identified in 21 knees (31.3%) through plain radiography and in 40 knees (59.7%) through CT. Multivariate logistic regression analysis showed that the medial closing gap and lateral hinge position were predictive factors for plain radiography– and CT-based LHF after MCDFO. Controlling for other variables, we found that an increase in the medial opening gap by 1 mm increased the likelihood of plain radiography–based LHF by a factor of 1.805 (95% CI, 1.291-2.525; P = .001) and CT-based LHF by 1.333 (95% CI, 1.003-1.772; P = .048). Moreover, a lateral hinge position in the supracondylar area increased the likelihood of plain radiography–based LHF by a factor of 9.870 (95% CI, 2.179-44.720; P = .003) and CT-based LHF by 5.686 (95% CI, 1.124-28.754; P = .036). Conclusion: A large medial closing gap and lateral hinge position in the supracondylar area are associated with LHF in MCDFO. Care should be taken to prevent LHF in MCDFO with a large medial closing gap. Moreover, a lateral hinge position in the supracondylar area should be avoided to decrease the incidence of LHF in MCDFO.