Objective:To investigate whether deltoid ligament (DL) injury produces axial-plane rotational instability of the ankle in patients with chronic ankle instability (CAI).Methods:A retrospective study was conducted to analyze the 33 patients with CAI who had been treated at Department of Orthopaedics, The First Affiliated Hospital of Nanjing Medical University between January 2023 and December 2024. The cohort consisted of 17 males and 16 females with an age of (31.5±9.9) years. The patients were assigned into 2 groups based on the presence of DL injury: a lateral chronic ankle instability (LCAI) group ( n=17) and a rotational ankle instability (RAI) group ( n=16). Barefoot natural walking trials were performed in all patients. Three-dimensional kinematic data were synchronously collected using an optical motion capture system (12 cameras) and force plates. A lower extremity model was constructed to obtain shank axial rotation (internal/external rotation) and rear-foot inversion/eversion angles. Continuous relative phase (CRP) analysis was employed to assess shank-rearfoot movement coupling. The mean absolute relative phase (MARP) and deviation phase (DP) were calculated. Results:There was no statistically significant difference in the clinical baseline data between the 2 groups, indicating comparability ( P>0.05). Throughout the gait cycle, no significant differences were found in shank rotation angles or rear-foot eversion angles between the RAI group and the LCAI group. However, CRP analysis revealed that during the early stance phase (initial contact and loading response), shank-rearfoot coupling was significantly lower in the RAI group than in the LCAI group. In the early stance phase, the CRP values in the RAI group were significantly higher than those in the LCAI group. The CRP curve changes in the RAI group were consistently higher in the standce phase of the entire gait cycle than those in the LCAI group, and the peak value of the CRP curve was larger in the RAI group. Concurrently, the RAI group exhibited significantly higher MARP and DP values than the LCAI group (27.48°±14.54° versus 15.21°±9.56°; 26.02°±11.73° versus 17.83°±9.82°) (both P<0.05). Conclusion:DL injury significantly damages the axial rotational stability of the ankle joint and significantly exacerbates the mechanical instability of the ankle joint in CAI patients.

Objective:To investigate whether deltoid ligament (DL) injury produces axial-plane rotational instability of the ankle in patients with chronic ankle instability (CAI).Methods:A retrospective study was conducted to analyze the 33 patients with CAI who had been treated at Department of Orthopaedics, The First Affiliated Hospital of Nanjing Medical University between January 2023 and December 2024. The cohort consisted of 17 males and 16 females with an age of (31.5±9.9) years. The patients were assigned into 2 groups based on the presence of DL injury: a lateral chronic ankle instability (LCAI) group ( n=17) and a rotational ankle instability (RAI) group ( n=16). Barefoot natural walking trials were performed in all patients. Three-dimensional kinematic data were synchronously collected using an optical motion capture system (12 cameras) and force plates. A lower extremity model was constructed to obtain shank axial rotation (internal/external rotation) and rear-foot inversion/eversion angles. Continuous relative phase (CRP) analysis was employed to assess shank-rearfoot movement coupling. The mean absolute relative phase (MARP) and deviation phase (DP) were calculated. Results:There was no statistically significant difference in the clinical baseline data between the 2 groups, indicating comparability ( P>0.05). Throughout the gait cycle, no significant differences were found in shank rotation angles or rear-foot eversion angles between the RAI group and the LCAI group. However, CRP analysis revealed that during the early stance phase (initial contact and loading response), shank-rearfoot coupling was significantly lower in the RAI group than in the LCAI group. In the early stance phase, the CRP values in the RAI group were significantly higher than those in the LCAI group. The CRP curve changes in the RAI group were consistently higher in the standce phase of the entire gait cycle than those in the LCAI group, and the peak value of the CRP curve was larger in the RAI group. Concurrently, the RAI group exhibited significantly higher MARP and DP values than the LCAI group (27.48°±14.54° versus 15.21°±9.56°; 26.02°±11.73° versus 17.83°±9.82°) (both P<0.05). Conclusion:DL injury significantly damages the axial rotational stability of the ankle joint and significantly exacerbates the mechanical instability of the ankle joint in CAI patients.