Change in the First Cuneiform-Second Metatarsal Distance After Simulated Ligamentous Lisfranc Injury Evaluated by Weightbearing CT Scans

BACKGROUND: This study aimed to investigate the widening between the first cuneiform (C1) and second metatarsal (M2) in a Lisfranc ligamentous complex (LLC) joint injury model subjected to successive ligament dissections evaluated by weightbearing computed tomography (CT) scans.

METHODS: Twenty-four intact cadaveric feet served as the control (condition 1). Each component of the LLC (dorsal, interosseous, and plantar ligaments-conditions 2, 3, and 4, respectively) were then sequentially dissected. The specimens were equally randomized to 1 of 3 additional dissections (first or second tarsometatarsal [TMT] joint capsule or first-second intercuneiform ligament [ICL]-conditions 5a, 5b, and 5c, respectively). One additional ligament was then randomly transected (eg, condition 6ac-transection of the first TMT capsule and ICL). Finally, the remaining ligament was transected (condition 7). After each dissection, CT scans were acquired under nonweightbearing (NWB, 0 kg), partial-weightbearing (PWB, 40 kg), and full-weightbearing (FWB, 80 kg) conditions. The distance between the lateral border of C1 and the medial border of M2 was assessed to evaluate diastasis. Linear regressions with 95% CIs and converted q values were used to compare the measured data.

RESULTS: No significant differences were found within the control. In condition 4, an average axial plane widening relative to control of 1.6 mm (95% CI, 1.5-1.8) and 2.1 mm (95% CI, 1.9-2.2) was observed under PWB and FWB. A coronal plane widening of 1.5 mm (95% CI, 1.3-1.6) and 1.9 mm (95% CI, 1.7-2.1) under PWB and FWB, respectively, was measured. A 95% CI of at least a 2-mm widening during PWB was demonstrated in 5c, 6ac, 6bc, and 7.

CONCLUSIONS: Weightbearing computed tomography (WBCT) scans were used to detect ligamentous Lisfranc injuries in a cadaveric model. Relative axial widening greater than 1.5 mm under PWB conditions could indicate a complete LLC injury. Complete transection of the intercuneiform 1-2 ligament was required to detect a 2-mm widening in the nonweightbearing condition.

CLINICAL RELEVANCE: This study provides insight on the detection of various severities of LLC injuries using WBCT imaging.