The multi-ligament ankle fracture: Epidemiology, key anatomical findings and fixation strategies in unstable open injuries.

Background: Ankle fracture surgery has traditionally focussed on restoration of bony anatomy, with fixation of the malleoli and syndesmotic stabilisation where applicable. However, high energy open fracture-dislocations can also result in periosteal stripping of the stabilising capsuloligamentous attachments. As such, restoration of osseous anatomy alone may not result in sufficient articular stability. Objectives: In this series from a level 1 trauma centre, we report a subset of highly unstable open ankle fractures with combined capsuloligamentous injuries, in which restoration of osseous anatomy did not result in a stable joint. Supplementary soft tissue reconstruction and other stabilisation techniques were required. Methods: Retrospective case series of eligible patients from a level 1 trauma centre. Inclusion criteria were open ankle fractures with tibial extrusion (AO 44) and persistent instability post-bony fixation, age over 18 years and non-diabetic. Analysis of injury pattern, mechanism, pathological anatomy, soft tissue and orthopaedic reconstruction methods was performed. Results: 16 patients were identified during the study period who met the eligibility criteria, out of 95 open ankle fractures treated between January 2017-December 2020. Most patients were under 65 (n = 13; 81.3%) and sustained combined or isolated injuries of the deltoid ligament, anterior capsule, lateral ligament complex (ATFL±CFL) and tibialis posterior retinaculum. The commonest injury pattern was tibial extrusion via a medial soft tissue defect with deltoid ligament and anteromedial capsule rupture. Associated syndesmotic instability and fixation was common (n = 10; 62.5%). Supplementary stabilisation methods to standard bony fixation included capsuloligamentous reconstruction or repair, "ORIF+" external fixation, or conversion to primary fusion or hindfoot nail. Six patients required either local or free flap soft tissue coverage. Conclusions: A subset of up to 20% of open ankle fractures require supplementary fixation beyond anatomical restoration of the bony anatomy due to persistent ligamentous instability. They are associated with capsuloligamentous and syndesmotic disruption, more commonly affecting the medial structures. These rare injuries can be defined as multi-ligament ankle fractures. Surgeons should be aware of this subset and be able to recognise where supplementary stabilisation strategies are required.