Do Syndesmotic Injury Patterns Influence Functional and Radiological Outcomes in Complex Ankle Fractures? A Retrospective Cohort Study

Abstract

Category: Ankle; Trauma Introduction/Purpose: Syndesmosis injury can be of a varying magnitude; little information exists about the influence of degree of initial syndesmotic injury/instability on functional outcomes in ankle fractures, nor is there any correlation of this with follow up radiological parameters. Aims and Objectives: To identify and define morphological patterns of syndesmotic injury in ankle fractures according to a zone based evaluation, and correlate initial degree of instability with mid-term functional and radiological outcomes using validated scores Design: Retrospective cohort study, to review a prospective question. Methods: 40 complex ankle fractures out of 120 ankle fractures in our ankle registry met the inclusion criteria ie significant documented syndesmosis involvement needing stabilization, with all initial clinical and radiological records available. The patients were followed up between January 2020 to July 2021. Injury characteristics, fracture morphology of posterior malleolus, medial malleolus and fibula were noted and classified by validated classification systems based on x-rays and CT scan. The syndesmosis was analyzed on axial CT scan; it was divided into 3 zones, A,B,C from anterior to posterior, and degree of displacement and morphology was noted. Immediate post-operative radiographs were evaluated for fracture and syndesmosis reduction. The patients were evaluated at final follow up with both ankle specific scores (Olerud Molander score, Ankle-Hindfoot scale, Manchester-Oxford Foot questionnaire) and quality of life score (SF-12). Ankle Osteoarthritis grade was used to evaluate radiological outcomes. Results: Mean follow-up was 19 months. 22(55%) patients had syndesmotic widening on plain radiographs; however in pre- operative CT scan evaluation 40(100%) patients had syndesmotic injury based on the Zone evaluation of the syndesmosis. 22 patients had Zone A injury (widening, AITFL, Chaput, Wagstaff). 22 patients had widening of Zone B. Zone C was involved in 30 patients (PM fracture,PITFL involvement). At final follow up; the mean OMAS was 83.38±16.35, mean Ankle-Hindfoot scale= 88±9.98, mean Mox-FQ score=27.15±13.35 & mean SF-12 were (MCS=56.59±8.24, PCS=51.18±8.48). There was no significant difference in outcome scores based on fracture types, Posterior malleolus morphology, or based on zones of syndesmosis injury. Syndesmosis malreduction contributed to significantly poorer outcomes (SF-12, OMAS, MoxFQ) Conclusion: Despite a zonal classification of syndesmotic injury on CT and more clarity of injury patterns, we could not corelate the site and extent of syndesmotic injury with final functional and radiological outcomes. The one factor that has significant influence is initial accurate reduction of both the malleolar fractures and syndesmosis injury. In this the CT based axial classification may play a role.