Biomechanical Testing of a Transmetatarsal Base Screw in Lisfranc Injuries.

OBJECTIVES

To compare displacement between the cuneiforms and metatarsals for a typical Lisfranc screw and a transmetatarsal base screw under biomechanical loading.

METHODS

Eight pairs of cadaveric feet (16 total) were evaluated. The Lisfranc ligamentous structures were transected in all specimens. All feet were repaired with screws traversing the first and second tarsometatarsal joints. A Lisfranc screw was placed from the first cuneiform to the second metatarsal in 8 specimens. A transmetatarsal base screw from the first metatarsal to the second metatarsal was placed in the remaining 8 corresponding feet. The repairs were randomized by side. Markers were placed on the dorsum of the midfoot for optical tracking. The feet were mounted into a load frame and loaded on the plantar forefoot to 100, 400, 800, and 1100 N. Displacement was measured and recorded using 3D camera tracking.

RESULTS

Displacement between the first cuneiform and second metatarsal base was found to be significantly less (P = 0.02) with the transmetatarsal screw than the Lisfranc screw. There were no significant differences between displacements at any other articulations.

CONCLUSIONS

This study demonstrates biomechanical superiority using a modified transmetatarsal base screw compared with the highly used Lisfranc screw for fixation of ligamentous Lisfranc injuries.