Objectives: Optimal fixation technique after purely ligamentous Lisfranc injury remains controversial. This biomechanical study compares dorsal plate versus transarticular screw fixation by measuring dorsal and plantar joint diastasis. A unique protocol was developed, using reflective triad markers and positional cameras.
Methods: Eleven cadaveric matched pairs were assigned to either transarticular screw or dorsal plate fixation. Two reflective triad markers were placed into the medial cuneiform (C1) and second metatarsal base (MT2). Three cameras recorded the 3-dimensional location of triads to quantify C1-MT2 diastasis in the following states: intact Lisfranc ligament (INTACT), cut ligament (CUT), fixed (SCREW or PLATE) joint, and fixed joint after 10,000 loaded cycles. On completion, the plantar Lisfranc ligament insertions were identified, and plantar diastasis was determined using additional reflective triads. Statistical post hoc pairwise comparisons assessed differences in diastasis.
Results: C1-MT2 diastasis in the CUT state increased relative to INTACT (P < 0.001). SCREW fixation reduced C1-MT2 diastasis relative to CUT at dorsal (P < 0.007) and plantar (P = 0.015) locations after cycling. PLATE fixation significantly reduced dorsal diastasis relative to CUT (P < 0.001) but not for plantar diastasis (P > 0.99). PLATE plantar diastasis was numerically higher than INTACT but not significantly (P > 0.39). PLATE plantar diastasis tended to be greater than SCREW before cycling (P = 0.068) and after cycling (P = 0.080).
Conclusions: Transection of the Lisfranc ligament complex yielded C1-MT2 diastasis. Both SCREW and PLATE fixation successfully reduced dorsal diastasis. However, upon load, the PLATE resulted in greater plantar diastasis, nearly statistically different relative to the SCREW. Cyclic loading at 343 N did not worsen diastasis.