Introduction: Tarsometatarsal joint complex (TMC) is the anatomical structure of midfoot composed by metatarsals, tarsometatarsal (TMT) joints, cuneiforms, cuboid and navicular. TMC lesion are rare but critical since they cause severe disability if misdiagnosed. The knowledge of anatomic pattern of the lesion and biomechanics of the midfoot is the key for a successful diagnosis and treatment. The aim of this study was to review a consecutive series of TMC injuries analyzing preoperative radiograph and CT scan to accurately define the pattern of ligament and bone injuries.
Material and methods: We reviewed a series of 24 complete TMC injuries with homolateral dorsolateral dislocation. The total TMT joints involved were 120. We observed if the lesions were pure ligamentous or fracture-dislocation detecting the extent and the location of fractures. Twenty-nine lesions (24%) were pure dislocations and they were mainly localized in the first and fifth ray. The fracture-dislocations were 91 (76%) and 25 were fractures of the proximal row (cuneiforms and cuboid), 39 of the distal row (metatarsals), 27 of both the distal and proximal row.
Results: Proximal fracture had a homogeneous distribution and they were more frequently simple than comminuted. Comminuted fractures were more frequent in the cuboid. In the proximal row, majority of partial articular fractures were localized in the dorsal side. Fracture-dislocations of the distal row were more frequent in the second metatarsal base (100%) and the partial articular fractures were always placed in the plantar side. In TMC injuries fracture-dislocations are more frequent than pure dislocations. Pure dislocations occur more often in the marginal rays that are characterized by weaker ligaments and larger mobility. The second ray, where there is the more stable joint of TMC, was never dislocated with a pure ligamentous lesion.
Conclusions: We suppose that plantar avulsion from the distal row and dorsal compression fracture of the proximal row is consistent with a direct force applied to the forefoot and direct dorsolaterally. The direction of the forces may explain why some fractures occur in the distal row, some in the proximal and some in both rows. The thickness of plantar ligaments may explain the frequency of plantar bone fragment avulsion.
Keywords: Fracture-dislocation; Lisfranc injury; Tarso-metatarsal joint.
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