Ligamentous Lisfranc injuries: analysis of CT findings under weightbearing.

Purpose: The aim of this study was to investigate the influence of different ligamentous Lisfranc injuries on computed tomography (CT) findings under weight-bearing and to emphasize the indications for surgical treatment of their various types.

Methods: Sixteen human cadaveric lower limbs were placed in weight-bearing radiolucent frame for CT scanning. All intact specimens were initially scanned, and then, dorsal approach was used for sequential ligaments cutting of: (1) the dorsal and the interosseous (Lisfranc) ligaments between medical cuneiform (MC) and metatarsal 2 (MT2); (2) the plantar ligament between the MC and MT3; (3) the plantar ligament between MC and MT2. Based on sequential CT scans, the distances MT1-MT2, MC-T2, as well as the alignment and dorsal displacement of MT2 were measured.

Results: Slight increase in the distances MT1-MT2 and MC-MT2 was observed after the disruption of the dorsal and the interosseous ligaments. Further increase in MT1-MT2 and MC-MT2 distances was registered after the disruption of the ligament between MC and MT3. The largest distances MT1-MT2 and MC-MT2 were measured after the final plantar ligament cut between MC and MT2.

Conclusions: Unequivocal instability is observed with simultaneous transection of the Lisfranc ligament with both plantar ligaments. On CT used as diagnostic tool, plantar injuries at the basis of the second and the third metatarsal are indirect signs of violation of the ligaments and represent an indication for surgical treatment. When using magnetic resonance imaging as diagnostic tool, a ruptured Lisfranc ligament alone without dislocation does not necessarily need surgical intervention.