Stability of lisfranc injury fixation in theil cadavers: is fixation of the third ray necessary?
R. Lawton, S. Dalgliesh, F. Harrold, G. Chami
Introduction: 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 Lisfranc injuries or if fixation of the 3rd ray is also required to fully stabilise the medial column. Unlike the 4th and 5th TMTJs, stabilisation of the 3rd ray requires either intra-articular screw fixation or bridge plating, which both risk causing chondrolysis and/or OA.
Methods: In eight Theil embalmed specimens, measurements of 1st - 2nd metatarsal gaping and TMTJ dorsal displacement were made at each ray (1st to 5th) during simulated weight bearing with sequential ligamentous injury and stabilisation to determine the contribution of anatomical structures and fixation to stability. At baseline, the 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.
Resuls: 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.
Conclusion: The results suggest that stabilising the medial cuneiform to 2nd metatarsal base and 4/5th TMTJs with K wires will stabilise the 3rd TMTJ if the inter-metatarsal ligaments are intact. Thus 3rd TMTJ stability should be checked after stabilisation with a home run screw and k wires to the 4/5th rays. Provided the 3rd-4th intermetatarsal ligaments are intact the 3rd ray does not need to be stabilised.
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