Plantar versus dorsomedial locked plating for Lapidus arthrodesis: a biomechanical comparison.

BACKGROUND: Lapidus arthrodesis with a plate and a compression screw is an established procedure in hallux valgus surgery. The present study was performed to investigate the potential benefit of a compression screw combined with a plantarly applied angle-stable, anatomically precontoured plate or a dorsomedially applied angle-stable plate.

METHODS: In six pairs of human cadaver specimens, one specimen each was randomized to receive a dorsomedial H-shaped plate, while the other received a plantar plate. Bone mineral density was measured with peripheral quantitative computed tomography. The specimens were loaded quasi-statically, followed by cyclic loading. Finally, they were loaded to failure. In the static tests, stiffness and range of motion (ROM) data were obtained. In the cyclic tests, the constructs' displacement was studied. In the load-to-failure test, stiffness and maximum load to failure were measured.

RESULTS: The two groups did not differ significantly with regard to BMD (p = 0.25). Any significant differences observed were in favor of the plantar constructs, which had greater initial stiffness (p = 0.028) and final stiffness (p = 0.042), a smaller ROM (p = 0.028), and a greater load to failure (p = 0.043). There was no significant difference regarding displacement (p = 0.14).

CONCLUSION: In the static tests, the plantar angle-stable plate construct was superior to the dorsomedial angle-stable plate construct.

CLINICAL RELEVANCE: Plantar plating appears to offer biomechanical benefit. Clinical studies will be required to show whether this translates into earlier resumption of weightbearing and into lower rates of nonunion.