A Single Lateral Hinge Screw Increased Resistance to Varus Stress After Medial Opening Wedge High Tibial Osteotomy in a Synthetic Bone Model: a Biomechanical Analysis.

Abstract

Purpose: To determine whether use of a tibial screw placed across the lateral tibial hinge results in significantly higher failure load compared with no lateral screw after medial opening wedge high tibial osteotomy (MOWHTO).

Methods: Twelve Sawbone tibias were used for the study. A MOWHTO was performed in each specimen using a computed tomography-based patient specific correction guide, and 6 specimens received a lateral hinge screw. Cantilever varus bending load was applied to failure, and failure load, displacement at failure, and stiffness of the osteotomy before hinge failure were recorded.

Results: Failure load was statistically higher in the hinge screw group compared to the control group, 437.0 ± 82.0 N vs 336.0 ± 55.9 N, p = 0.046 (mean ± standard deviation). This load to failure was 30% higher in MOWHTO using a hinge screw versus the control.

Conclusion: Using a Sawbone model, the current data showed that placement of a lateral hinge screw significantly increased resistance to varus stress following MOWHTO compared with a construct having no tibial screw. Additionally, no significant difference in displacement or stiffness was observed between the hinge screw and the control groups.

Clinical relevance: The current biomechanical findings suggest that the use of a laterally based proximal tibial screw can potentially reduce the risk of lateral hinge fracture and its associated morbidity after MOWHTO.