Syndesmosis Evaluation Under WBCT: 3rd Base to Get a Cut-Off Point to Diagnosis

Abstract

Category: Sports; Arthroscopy Introduction/Purpose: Evaluation of syndesmal injury remains challenging for Foot & Ankle Surgeons. As objective data to provide an accurate preoperative diagnosis of syndesmal instability is lacking, arthroscopy has remained the Gold Standard. However, the costs and risks associated with surgery make arthroscopy challenging to indicate in all cases. Therefore, significant interest exists in determining objective criteria to safely indicate surgery. Comparative WBCT is a valuable tool, allowing a precise evaluation of the healthy and injured joints. Specifically, the difference in the syndesmal area correlates with diastasis at the inferior tibiofibular joint, while the cut value for diagnostic instability remains undetermined. Objective: To compare the difference in syndesmal area between healthy patients and patients with syndesmal sprains under WBCT. Methods: IRB approval was obtained for a retrospective case-control study. Patients with suspected syndesmal injuries from April 2019 to August 2022 were included in the case group. Patients with chronic ankle instability, age over 55 years, or surgery of the inferior limb were excluded. The control group was obtained from a previous study of comparative WBCT of the ankle joint, obtained for reasons different than trauma or instability. All patients were evaluated under WBCT by a fellowship-trained MSK radiologist. After evaluating the syndesmal area at 1 cm from the ankle joint line in an axial WBCT slice, the percentage difference from the injured to the healthy side was recorded. Demographic data were obtained from the patient chart. For those patients undergoing surgical stabilization, the operative note was examined. Statistical evaluation was performed by an independent statistician using SPSSv27 using the ANOVA test. Results: Thirty-nine patients were recruited for the study group, and a control group of 25 patients with healthy ankles was obtained. Demographics data for both groups were comparable Arthroscopy was indicated in 7/39 patients (17,9%), which confirmed diagnosis and warranted stabilization of the joint. The mean percentage area difference of the confirmed injured syndesmosis was 15,14% (IC 4,89-25,39), suspected injured syndesmosis was 9,25% (IC 3,11-15,39), and the healthy syndesmosis was 1,54 (IC 1,08-2,01). Statistically significant differences were obtained for healthy, operated, and non-operated patients with a p=0,021. Conclusion: A comparative WBCT scan and the percentage difference in the syndesmal area between the healthy, confirmed, and suspected syndesmal injury demonstrated a handy diagnostic tool. Although the limitations of this study, our results suggest that a 15% difference in the syndesmal area between healthy and injured sides might be used as the cut-off point to indicate diagnostic arthroscopy.