Does the anteromedial plate position affect proximal screw length and worsen the clinical outcomes in medial opening wedge high tibial osteotomy?

Background: During medial opening wedge high tibial osteotomy (MOWHTO), sometimes the plate tends to be positioned anteromedially. The plate position can affect the length of the proximal screw, which significantly affects stability after osteotomy. Therefore, research on the correlation among plate position, screw length, and clinical outcomes is needed. Methods: This retrospective review examines 196 knees in 175 patients who underwent MOWHTO from May 2012 to December 2018, for symptomatic medial compartment osteoarthritis with a varus alignment of > 5°. We evaluated the anteroposterior plate position, length of proximal screw, and postoperative computed tomography (CT). We reviewed patients’ clinical outcome scores, presence of lateral hinge fracture, neurovascular complications, and infection. The correlation among proximal plate position, proximal screw length, and clinical outcomes was evaluated using Pearson’s correlation analysis. A subgroup analysis by screw angle (> 48 ° or < 48 °) was also performed using chi-square test and Student t-test. Results: The mean proximal plate position was 16.28% (range, 5.17–44.74) of the proximal tibia’s anterior-to-posterior distance ratio, and the proximal screw length averaged 63.8 mm (range, 44–80 mm). Proximal posteromedial plate position and proximal screw length were significantly correlated (r2 = 0.667, P <.001), as were screw angle and length (r2 = 0.746, P <.001). Medial plating (< 48°) can use a longer proximal screw; nevertheless, no significant difference occurred in clinical outcomes between the two groups. Also, no differences occurred in complication rate, including hinge fracture. Conclusion: With more medially positioned plating during MOWHTO, we can use longer proximal screws. However, there was no significant difference in clinical outcomes and the incidence of lateral hinge fractures regardless of plate position and screw length.