Dynamic Evaluation Of The Effect Of Syndesmotic Injury On Lateral Ankle Stability Using Fluoroscopy

CATEGORY: Ankle; Sports; Trauma INTRODUCTION/PURPOSE: There is a high incidence of concomitance between lateral ankle ligament injuries and syndesmotic ligamentous injuries. However, it is unclear whether syndesmotic ligaments directly contribute toward the stability of the lateral ankle. Stress radiographs are an accepted technique to assess the degree of lateral ankle instability by providing a static view of the ankle when subjected to the anterior drawer (AD) and talar tilt (TT) tests. The aim of this study is to assess the effect of syndesmotic injury as well as combined syndesmotic and lateral ankle injury on the stability of the lateral ankle. METHODS: Sixteen fresh frozen above-knee amputated cadaveric specimens, divided into two groups, underwent fluoroscopic evaluation for lateral ankle stability. In both the groups, the assessment was first done with all ligaments intact and later with sequential transection of anterior inferior tibiofibular ligament (AITFL), interosseous ligament (IOL), posterior inferior tibiofibular ligament (PITFL), anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL) and posterior talofibular ligament (PTFL). In all scenarios, two loading conditions were considered: (1) Anterior drawer test: 50N and 80N and (2) Talar tilt and Lateral clear space (LCS): 1.7Nm torque. The talar translation, talar tilt, and LCS were measured using Image J. Wilcoxon rank-sum test was used to compare the findings of each ligamentous transection state to the intact state. A p-value <0.05 was considered statistically significant. RESULTS: In group 1 after transection of the AITFL and IOL, an increase in the anterior drawer, talar tilt, and lateral clear space values was found as compared to the intact state. Similarly, in group 2 the anterior drawer, talar tilt, and lateral clear space values significantly increased after transection of the AITFL and ATFL as compared to the intact state (p-values = 0.001). CONCLUSION: Lateral ankle instability appears after injury to two syndesmotic ligaments (AITFL and IOL), or after one syndesmotic ligament rupture (AITFL) with a concomitant anterior talofibular ligament rupture (ATFL). These findings suggest that surgeons should lower their threshold for stabilizing the syndesmosis if there is a concomitant lateral ankle ligament injury.