BACKGROUND: Subtle, or ligamentous, Lisfranc injuries occur following low-energy trauma to the midfoot and can be debilitating. Since they are ligamentous, they may not heal, requiring arthrodesis in some cases. Certain mortise anatomic characteristics on radiographs have been shown to be associated with a predisposition to the ligamentous subtype of Lisfranc injuries. It is not known whether there are other morphometric characteristics, such as arch height or the relative length of the second metatarsal, that can similarly influence the predisposition to these injuries. METHODS: The present retrospective matched case-control study involved fifty-two control subjects and twenty-six patients with ligamentous Lisfranc injuries treated from 2006 to 2010 at two institutions. Clinical and radiographic data (second metatarsal length relative to foot length, first intermetatarsal angle, navicular-cuboid overlap relative to cuboid vertical height, first metatarsal-talus angle, and calcaneal pitch angle) were examined for the existence of significant differences between control and Lisfranc subjects. Logistic regression analysis was then performed to evaluate potential risk for injury on the basis of these anatomic variables. RESULTS: Compared with matched controls, patients with a ligamentous Lisfranc injury were found to have a significantly smaller ratio of second metatarsal length to foot length (p < 0.001) on weight-bearing radiographs. CONCLUSIONS: Occurrence of a ligamentous Lisfranc injury was shown to be associated with a smaller ratio of second metatarsal length to foot length; >50% of patients in the injury group had a ratio of <29%.
BACKGROUND: Subtle, or ligamentous, Lisfranc injuries occur following low-energy trauma to the midfoot and can be debilitating. Since they are ligamentous, they may not heal, requiring arthrodesis in some cases. Certain mortise anatomic characteristics on radiographs have been shown to be associated with a predisposition to the ligamentous subtype of Lisfranc injuries. It is not known whether there are other morphometric characteristics, such as arch height or the relative length of the second metatarsal, that can similarly influence the predisposition to these injuries. METHODS: The present retrospective matched case-control study involved fifty-two control subjects and twenty-six patients with ligamentous Lisfranc injuries treated from 2006 to 2010 at two institutions. Clinical and radiographic data (second metatarsal length relative to foot length, first intermetatarsal angle, navicular-cuboid overlap relative to cuboid vertical height, first metatarsal-talus angle, and calcaneal pitch angle) were examined for the existence of significant differences between control and Lisfranc subjects. Logistic regression analysis was then performed to evaluate potential risk for injury on the basis of these anatomic variables. RESULTS: Compared with matched controls, patients with a ligamentous Lisfranc injury were found to have a significantly smaller ratio of second metatarsal length to foot length (p < 0.001) on weight-bearing radiographs. CONCLUSIONS: Occurrence of a ligamentous Lisfranc injury was shown to be associated with a smaller ratio of second metatarsal length to foot length; >50% of patients in the injury group had a ratio of <29%.