Fixation of Takeuchi Type II/III lateral hinge fractures provides favourable stability of a medial open wedge high tibial osteotomy-A biomechanical study.

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To investigate the biomechanical consequences of osteosynthesis of lateral hinge fractures (LHFs) in medial open wedge high tibial osteotomy (MOWHTO). Sixteen fresh-frozen human cadaveric proximal tibiae underwent MOWHTO fixed with an ipsilateral locking compression plate. The specimens were assigned to two clusters simulating LHFs according to the Takeuchi classification: (1) Type II fracture; and (2) Type III fracture. The following conditions were serially tested: (1) intact hinge; (2) fractured hinge; (3) screw fixation of the LHF; (4) staple fixation of the LHF; and (5) locking T-plate fixation of the LHF. Each specimen was subjected to 10 cycles of axial compression load (720 N; 36 N/s), and internal and external rotational loads (10 N m; 1 N m/s), while capturing the interfragmentary movements via motion tracking. In Takeuchi Type II fractures, osteosynthesis of the fractured hinge with staples or a plate significantly reduced fracture site displacement (p < 0.05) and significantly increased construct stiffness (p < 0.05) under axial and torsional loading, while only the plate restored intact torsional displacement (n.s.). For Takeuchi Type III fractures, both screw and plate fixation significantly reduced fracture site displacement (p < 0.05) and significantly increased construct stiffness (p < 0.05) under axial and torsional loading. Both techniques restored torsional stiffness in each rotational direction and torsional displacement in internal rotation (n.s.). Additional plate fixation of Takeuchi Type II fractures was the construct with the highest stiffness, restoring the axial and torsional stability to a MOWHTO with an intact hinge. Screw and plate fixation of Takeuchi Type III fractures provided equivalent stability and restored the torsional and axial stability of the MOWHTO. In case of a Takeuchi Type II or III fracture, surgeons should consider additional plate or screw osteosynthesis of the fractured hinge to best restore the stability of the MOWHTO, which may potentially reduce the risk of loss of correction and impaired bone healing. There is no level of evidence as this study was an experimental laboratory study.