Abstract
Research Type:
Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies
Introduction/Purpose:
Evaluating syndesmotic stability in both acute and chronic settings is inherently challenging. Failure to diagnose syndesmotic ankle injuries can lead to end-stage ankle osteoarthritis in up to 30% of cases. While advanced imaging modalities, such as magnetic resonance imaging (MRI), have historically been the gold standard for evaluating distal tibiofibular complex injuries, this study investigates the application of a three-dimensional (3D) cone beam weight-bearing computed tomography (WBCT) distance mapping algorithm for detecting syndesmotic instability under physiological loading conditions. We hypothesized that this algorithm would aid surgeons in accurately diagnosing syndesmotic instability in a clinical setting.
Methods:
A retrospective, single-institution study was conducted on patients with unilateral ankle instability and no history of contralateral ankle injury. All patients underwent surgical intervention for lateral ankle instability.
Preoperative assessment included cone-beam WBCT to evaluate syndesmotic morphology under physiological loading conditions. Semiautomatic segmentation of CT scans was performed using Disior Bonelogic (Disior, Paragon28, Englewood, CO, USA), with syndesmotic distance measurements computed via MATLAB. A three-dimensional (3D) distance mapping algorithm was employed to quantify syndesmotic incisura and lateral gutter distances (overall, minimum, maximum, 50% anterior, 50% posterior), which were subsequently compared with uninjured syndesmotic ankles. The diagnostic accuracy of distance mapping in detecting syndesmotic instability was assessed relative to arthroscopic findings using receiver operating characteristic (ROC) curve analysis and area under the curve (AUC).
Paired statistical analyses were conducted to identify significant differences between ankles with syndesmotic injuries and contralateral controls. Statistical significance was set at p < 0.05
Results:
Among 27 patients (54 ankles) with a mean age of 35.3 years (SD 17.5) and a mean BMI of 29.24 kg/m² (SD 8.59), 16 revealed syndesmotic instability during arthroscopy. No significant differences in age or BMI were observed between patients with and without syndesmotic injury. The distance mapping algorithm showed significant syndesmotic widening at 1 cm (12.44%, p=0.016) and 3 cm (14.70%, p=0.024), whereas 5 cm was not significant (p=0.114). Receiver operating characteristic analyses indicated moderate diagnostic accuracy, with AUC values of 0.64–0.717 at 1 cm and 0.689–0.692 at 3 cm. Paired t-tests comparing injured and contralateral ankles demonstrated widening in overall, anterior, and posterior distances (p < 0.05), with mean differences up to 0.36 mm.
Conclusion:
WBCT-based distance mapping can detect subtle syndesmotic widening under physiological loading, without rotational stress. Our retrospective analysis demonstrated that diagnostic accuracy is higher at 1 and 3 cm proximal to the tibio-talar joint line, with anterior and posterior measurements showing significant differences. Color-coded distance maps simplify interpretation, while measurements provide comparative values, supporting the use of contralateral comparisons in diagnosing syndesmotic instability. Our results suggest that this tool can enhance diagnostic precision in cases of subtle syndesmotic widening or instability. Future studies are needed to correlate these findings with clinical outcomes.
Figure 1 (A) Color-coded 3D distance map of the ankle, highlighting decreased tibiofibular distances (red - yellow) and increased distances (green-blue). (B) Comparative difference between injured and non-injured ankles. (C)
Measurements at multiple syndesmotic levels (1, 3, and 5 cm) and percentage differences with p-values. (D–F) Receiver operating characteristic (ROC) curves of diagnostic accuracy of distance mapping at 1 cm, 3 cm, and 5 cm.