Abstract
There is debate whether a home run screw (medial cuneiform to 2nd metatarsal base) combined with k-wire fixation of 4th & 5th rays is sufficient to stabilise Lisfrance injuries or if fixation of the 3rd ray is also required. Unlike the 2nd, 4th and 5th TMTJ, stabilisation of the 3rd requires either intra-articular screw or a cross joint plate which both risk causing chondrolysis and/or OA.
Using 8 Theil embalmed specimens, measurements of TMTJ dorsal displacement at each ray (1st to 5th) and 1st – 2nd metatarsal gaping were made during simulated weight bearing with sequential ligamentous injury and stabilisation to determine the contribution of anatomical structures and fixation to stability.
At baseline mean dorsal TMTJ displacement of the intact specimens during simulated weight bearing (mm) was: 1st: 0.14, 2nd: 0.1, 3rd:0, 4th: 0, 5th: 0.14. The 1st-2nd IM Gap was 0mm. After transection of the Lisfranc ligament only, there was 1st-2nd intermetatarsal gaping (mean 4.5mm), but no increased dorsal displacement. After additional transection of all the TMTJ ligaments dorsal displacement increased at all joints (1st: 4.5, 2nd: 5.1, 3rd: 3.6, 4th: 2, 5th: 1.3). Stabilisation with the home run screw and 4th and 5th ray k-wires virtually eliminated all displacement. Further transection of the 3rd/4th inter-metatarsal ligaments increased mean dorsal displacement of the 3rd ray to 2.5mm. K-wire fixation of the 3rd ray completely eliminated dorsal displacement.
The results suggest that stabilising the 2nd and 4/5th TMTJs will stabilise the 3rd if the inter-metatarsal ligaments are intact. Thus 3rd TMTJ stability should be checked after stabilising the 2nd and 4/5th. Provided the intermetatarsal ligaments (3rd-4th) are intact the 3rd ray does not need to be stabilised routinely.
