Diagnosis of subtle syndesmotic instability using conventional CT- imaging and axial force in different foot positions

Background: Currently, there is no available method that can objectively and reliably detect subtle instability of the distal tibiofibular joint. The purpose of this study is to diagnose, using computerized axial tomography and an adjustable simulated loading device, subtle instability of the tibiofibular syndesmosis.Methods: Fifteen healthy individuals and 15 patients with clinical suspicion of subtle instability of the tibiofibular syndesmosis (total 60 ankles) were studied using an adjustable simulated loading device (ASLD). This device allows to perform bilateral ankle CT scans in two forced foot and ankle positions (30 degrees of plantar flexion, 15 degrees of inversion, 20 degrees of internal rotation and 15 degrees of dorsal flexion, 15 degrees of eversion, 30 degrees of external rotation). Axial load was applied simultaneously in a controlled manner (70% body weight). Measurements on the axial image of computed tomography were: syndesmotic area (SA), fibular rotation (FR), position of the fibula in the sagittal plane (FPS), depth of the incisura (ID), anterior direct difference (ADD), middle direct difference (MDD) and posterior direct difference (PDD).Results: Statistically significant differences were observed in the variable syndesmotic area between healthy (mean=-0.14, SD=4.33) and diseased (mean=16.82, SD=12.3)(p < 0.001). No statistically significant differences were found in the variables ADD, MDD, PDD, ID, FPS and FR.Conclusions: Measurement of syndesmotic area employing axial force and forced foot positions using the ASLD may be useful for the diagnosis of subtle tibiofibular syndesmosis instability.(c) 2023 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study aimed to diagnose subtle instability of the tibiofibular syndesmosis using computerized axial tomography and an adjustable simulated loading device. The measurement of syndesmotic area was found to be useful for the diagnosis of subtle tibiofibular syndesmosis instability.