The Prognostic Value of Syndesmosis Malreduction for Revision Surgery: A Systematic Review
Authors: Heifner John , Kilgore Jack E. , Nichols Jennifer A. , Reb Christopher W. 
Published: January 2022

Category: Ankle; Trauma Introduction/Purpose: Reported rates of syndesmosis malreduction are highly variable due to applied criteria that differ in imaging modality, threshold for malreduction and use of the contralateral ankle for comparison. Studies have emphasized the importance of anatomic reduction while providing inconclusive evidence for the need for revision surgery in malreduced ankles. With no industry standard for determining malreduction, it is unclear whether the most commonly used criteria is a valuable discriminator for clinical decision making. Our objective was to describe the rates of syndesmosis revision that are reported in the literature and to determine if malreduction diagnoses are reliable in predicting the need for syndesmosis revision surgery. Methods: Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta Analyses) guidelines, a systematic review of the literature was performed in order to describe revision syndesmosis surgery. Included studies were grouped based on criteria for determining malreduction - group 1 (N = 954) used unilateral radiograph, group 2 (N = 41) used unilateral CT scan, group 3 (N =531) used bilateral CT scan and group 4 (N = 119) used bilateral radiograph. Evidentiary quality was graded with the Modified Coleman Methodology Score (MCMS). Student t tests were used to calculate the differences between groups for rates of malreduction and revision. For the screening criteria most commonly used to determine malreduction, the test characteristics sensitivity, specificity and positive predictive value (PPV) were calculated. Results: Pooled rates of malreduction and revision for the groups using CT scan (groups 2 and 3, N = 572, mean follow up 16 months) were 23.5% and 0.25% respectively. Pooled rates of malreduction and revision for the groups using bilateral imaging (groups 3 and 4, N = 650, mean follow up 20 months) were 18.5% and 0.8% respectively. Significant differences were found between CT scan and radiograph for malreduction (p<0.001) and for revision (p=0.02). Significant differences were also found between bilateral and unilateral imaging for malreduction (p=0.01). The malreduction criteria of a 2mm difference in tibiofibular space on CT scan between the injured and uninjured side was used in 6 studies (N = 531, mean follow up 19 months). The sensitivity of this criteria for detecting cases which required revision was 100%, specificity 78%, and PPV 6%. Conclusion: It is unclear whether high rates of malreduction are due to suboptimal surgical repair which lead to clinical detriment or are they solely an imaging finding which depend heavily on the criteria for diagnosis. The most commonly used criteria for malreduction - a 2mm side-to-side difference in tibiofibular space on CT scan - is highly sensitive for reoperations. The specificity and PPV indicate that a threshold of more than 2mm is needed to better evaluate those ankles which may require revision surgery. Based on the current findings, malreduction diagnoses do not adequately translate from disease-oriented information to patient-oriented information.