Background: Lateral hinge fracture (LHF) is a major complication of opening wedge high tibial osteotomy (OWHTO) and may result in poor outcomes.
Purpose/hypothesis: The purpose of this study was to develop preventive strategies by identifying factors that affect LHFs. We hypothesized that (1) each LHF type would have different affecting factors and that (2) specific operative strategies that can contribute to the prevention of each LHF type can be developed.
Study design: Case-control study; Level of evidence, 3.
Methods: We retrospectively analyzed 261 consecutive knees treated with biplanar OWHTO between March 2014 and December 2017. Perioperative radiological variables that can affect LHFs were measured and divided into 2 categories: unmodifiable and modifiable. A regression model was developed, and subgroup analyses involving comparisons between the non-LHF group and each LHF group were performed. The weightbearing line (WBL) ratio was measured at 2 weeks and 1 year after surgery to determine the serial changes in each LHF type.
Results: A total of 66 knees (25.3%) were diagnosed with LHFs. From these, 26 (39.4%), 13 (19.7%), 15 (22.7%), and 12 (18.2%) showed type I, II, III, and I-variant LHFs, respectively. In the subgroup analysis, a larger posterior gap and distance X and a smaller fibular height (FH) were significant unmodifiable factors, while the retrotubercular thickness was a significant modifiable factor, for type I LHF. For type II LHF, a smaller lateral condylar slope and a larger distance X were significant unmodifiable factors, while the lateral distal fragment thickness and the osteotomy-condylar angle were significant modifiable factors. For type III LHF, a larger lateral condylar width and distance X and a smaller FH were significant unmodifiable factors, while the lateral proximal fragment thickness and the retrotubercular angle (RA) were significant modifiable factors. A smaller FH and a larger distance X were significant unmodifiable factors for type I-variant LHFs, while the lateral thickness ratio and the RA were significant modifiable factors. Between postoperative week 2 and 1 year, the WBL ratio decreased in cases with type I LHFs (P < .001) and increased in those with type II (P = .001) and type I-variant (P = .006) LHFs.
Conclusion: Unmodifiable and modifiable factors for the development of LHFs after OWHTO differ among LHF types. To prevent LHFs, the causes of each LHF must be identified, the patient's specific geometry be considered in the preoperative planning, and the surgical technique be modified according to the modifiable factors. In addition, during the rehabilitation period after OWHTO, specific caution and close observation are necessary for alignment changes related to each LHF type.
Keywords: lateral hinge fracture; modifiable factor; opening wedge high tibial osteotomy; preventive strategy; unmodifiable factor.