Type C ankle fractures with additional medium-sized posterior malleolus fragment: Radiological and functional results of osseous reconstruction of the syndesmosis

Introduction

Standard treatment of type C ankle fractures with an additional posterior fragment (PF) consists of closed reduction and stabilisation using syndesmotic positioning screws. Biomechanical studies show that in case of a PF the posterior ligaments (PITFL) are always intact, and therefore stability can be obtained by fixation of only the PF. However, to date there are no published in-vivo studies supporting this hypothesis.

Methods

Multicenter prospective cohort study. Patients presenting between 2015 and 2020 with type C fractures with additional PF (5-25% of the joint surface) were approached for inclusion. Patients operated in center 1 are treated according to protocol 1 (placement of syndesmotic screws alone). Patients operated in center 2 are treated according to protocol 2 (open reduction and internal fixation of the PF using the posterolateral approach). Concomitant fractured medial and lateral malleoli are treated according to AO-principles. Pre- and post-operative radiographs and CT-scans were obtained for radiological outcome and validated questionnaires for functional outcome. Functional outcomes were assessed at 1Y using the VAS-pain (0-100), AAOS and Olerud and Molander (OMAS) questionnaires.

Results

9 patients were included in group 1 and 17 in group 2. Medial fractures were more common in group 1 (table 1). PF size was 15% vs 20%. No additional positioning screws were placed in group 2. Compared to the uninjured side on bilateral CT-scan, the fibula was malpositioned in the incisura in 22% vs 12%. Radiological outcome: medial clearspace 3.7 vs 3.4 mm, superior clearspace 3.2 vs 3.5 mm, step-off 2.7 vs 0.8 mm. Functional outcomes after 1Y were: VAS 28 vs 18, AAOS 83 vs 89, OMAS 63 vs 80 (table 2). Development of osteoarthritis and complications were similar after 1Y.

Conclusion

Fixation of the PF in type C ankle fractures with additional PF is an effective way to obtain syndesmotic reduction without using positioning screws.

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