The natural history of undisplaced Lisfranc-type injuries initially treated conservatively

P. Chen, N. Ng, S.P. Mackenzie, J.A. Nicholson, A.K. Amin

Background: Undisplaced Lisfranc-type injuries are subtle but potentially unstable fracture-dislocations with little known about the natural history. These injuries are often initially managed conservatively due to lack of initial displacement and uncertainty regarding subsequent instability at the tarsometatarsal joints (TMTJ). The aim of this study was to determine the secondary displacement rate and the need for delayed operative intervention in undisplaced Lisfranc injuries that were managed conservatively at initial presentation.

Methods: Over a 6-year period (2011 to 2017), we identified 24 consecutive patients presenting to a university teaching hospital with a diagnosis of an undisplaced Lisfranc-type injury that was initially managed conservatively. Pre-operative radiographs were reviewed to confirm the undisplaced nature of the injury (defined as a diastasis< 2mm at the second TMTJ). The presence of a 'fleck' sign (small bony avulsion of the second metatarsal) was also noted. Electronic patient records and sequential imaging (plain radiographs/CT/MRI) were scrutinized for demographics, mechanism of injury and eventual outcome.

Results: The mean age of the patients at the time of injury was 42 years (19 Female). 96% (23/24) were low energy injuries and 88% (21/24) had a positive 'fleck sign'. The secondary displacement rate in this group of patients was 62.5% (15/24) over a median interval of 14 days (range 0 to 482 days). 12 patients underwent open reduction internal fixation after a median interval of 29 days (range 1 to 294 days) from their initial injury. One patient required TMTJ fusion at 19 months and two patients were managed non-operatively. The injury remained undisplaced in 37.5% patients (9/24) with only one patient requiring subsequent TMTJ fusion at 5 months.

Conclusion: Undisplaced Lisfranc injuries have a high rate of secondary displacement and warrant close follow-up. Early primary stabilisation of undisplaced Lisfranc injuries should be considered to prevent unnecessary delays in surgical treatment.