Biomechanical Comparison of Lag Screw versus Self-Drilling Screw Fixation of Oblique Metatarsal Osteotomy

Background: Several fixation methods for a Weil metatarsal osteotomy have been proposed. Lag screw fixation has been described as the preferred fixation technique. The self-drilling screw has been introduced and can be used for fixation of the Weil osteotomy. The current study compared self-drilling screws with lag screw fixation. Materials and Methods: A Weil metatarsal osteotomy was performed on the second, third, and fourth metatarsals of five matched pairs of fresh frozen cadaver feet. The feet of each pair were randomly assigned to fixation with either a 2.0-mm cortical lag screw or a 2.0-mm self-drilling screw. The second metatarsals were stressed using cantilever bending. The third and fourth metatarsals were stressed under a shear force. Yield load, deformation at yield load, structural stiffness, and energy stored at yield load were recorded. Results: There were no statistically significant differences ( p < 0.05) noted. However, there was a trend toward greater biomechanical stability with the lag screw. Conclusion: There were no significant differences in the stability of fixation of the self-drilling screw and lag screw. There was a trend toward the lag screw fixation being more stable. Clinical Relevance: The clinical significance of this trend is uncertain but suggests there is not a large difference between the two methods of fixation.