The utility of point-of-care dynamic ultrasonography for the diagnosis of subtle isolated ligamentous Lisfranc injuries: a cadaveric study.

Objectives: To assess if Lisfranc injury can be detected by US with and without abduction stress.

Methods: Eight cadaveric feet were obtained. The following measurements were obtained in the uninjured feet: C1M2 and C1C2 intervals and TMT1 and TMT2 dorsal step-off distances. Measurements were obtained both with and without abduction stress using ultrasound. The injury model was created by transecting the Lisfranc ligament complex, after which the observers performed the measurements again. Statistical analysis was used to identify differences between intact and injured models, to determine diagnostic cut-off values for identifying Lisfranc injuries, and to assess interobserver/intraobserver reliability.

Results: There was a significant difference in the mean C1M2 interval, both with and without abduction stress, between the intact and torn Lisfranc ligament (p < 0.001). A C1M2 interval with stress of > 2.03 mm yielded 81% sensitivity and 72% specificity for Lisfranc disruption. There was no significant difference in the mean C1C2 interval of the torn versus intact Lisfranc ligament without stress (p = 0.10); however, the distance was significantly different with the application of stress (p < 0.001). The C1C2 interval of > 1.78 mm yielded 72% sensitivity and 69% specificity for Lisfranc injury under stress. There were no significant differences in the mean TMT1 or TMT2 dorsal step-off measurements between the intact and torn Lisfranc ligaments. All observers showed good intraobserver ICCs. The interobserver ICCs for all measurements were good or excellent, except for TMT1, which was moderate.

Conclusion: Ultrasonography is a promising point-of-care imaging tool to detect Lisfranc ligamentous injuries when measuring C1M2 and C1C2 distances under abduction stress.