Background: An intact opposite cortex (OC) is essential for HTO stability. For an appropriate prognosis of the role of opposite cortical fracture (OCF) in the development of mechanical complications, it is important to identify the type of OCF. This study seeks to establish an OCF classification in CWHTO with a treatment algorithm.
Methods: The clinical radiological results of 187 angle-stable navigated CWHTOs were retrospectively analyzed. Two OCF types (according the direction of fracture line) with three subtypes (A-nondisplaced, B-primarily, and C-secondarily displaced) were identified.
Results: A total of 67.6% of type 1 and 44.7% of type 2 OCFs were non-displaced (p = 0.041). Secondary displacement developed in 36.2% of type 2 OCFs and in none of the type 1 OCFs. The tibial pseudoarthrosis rate was significantly higher with displaced type 2B and 2C OCFs than with non-displaced 2A fractures (30.8% vs. 4.8%, p = 0.03). The regression analysis showed a relevant correlation between OCF types 1B, 2B, and 2C and the incidence of mechanical complications; the significance of type 2C fractures (OR 43.8) for the incidence of tibial pseudoarthrosis was more than twice as high than for type 1B fractures.
Conclusion: Type 1 OCFs are considered to be stable and type 2 OCFs unstable with a tendency to become displaced. Only 57.4% of type 2 OCFs were recognizable intraoperatively; thus, increased attention must be focused on this event in postoperative repeat radiographs. The classification provides practice-relevant therapeutic approaches.
Keywords: CWHTO; Classification; Fracture; Hinge; Pseudarthrosis.
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