Defining normative side-to-side differences in the distal tibiofibular joint of healthy individuals using weight-bearing CT 3D image analysis

Abstract

Background and purpose

Accurate quantification of bony malalignment within the ankle syndesmosis is crucial in diagnosing syndesmotic instability, especially when subtle. While three-dimensional (3D) measurement techniques using weight-bearing computed tomography (WBCT) have gained popularity, normative bilateral comparative data still need to be established. This study aimed to identify the side-to-side variations and gender differences in the syndesmotic area and volume among individuals without syndesmotic injury using WBCT.

Methods

Retrospective analysis was conducted on bilateral ankle WBCT imaging of 88 individuals who underwent imaging for non-ankle-related injury or pathology. Two-dimensional area (at 1, 3, and 5 cm proximal to the tibial plafond) and three-dimensional volumetric (from 0.5 mm proximal to the tibial plafond and up to 3 and 5 cm proximally) measurements were obtained for bilateral ankles. Mean ( ± SD) values, percentage right-to-left differences, and gender differences were analyzed.

Results

Although there were no significant differences between laterality in any of the measurements, the largest right-to-left difference was 8.9 at the syndesmotic area at 3 cm above the tibial plafond in general. Contrarily, significant gender differences were found in the areas and volumes, with the largest difference observed for the 0.5–5 cm volume (8.41 ± 0.87 vs 7.45 ± 1.47 in male vs female, respectively; P = 0.001).

Conclusion

The mean side-to-site variation in the syndesmotic area and volume among individuals without syndesmotic injury is less than 9 %, and a side-to-side volume difference greater than 19 % might be indicative of abnormality. Additionally, gender-specific differences highlight the importance of considering gender norms in ankle syndesmosis evaluation and the need to use the contralateral side as a comparison.