Effect of Ankle Position during Anterior Talofibular Ligament Reconstruction on Ankle Kinematics, Laxity, and In-situ Force

CATEGORY: Ankle, Basic Sciences/Biologics INTRODUCTION/PURPOSE: Anatomical anterior talofibular ligament (ATFL) reconstruction is a standard surgical treatment for chronic lateral ankle instability. The optimal position during ATFL reconstruction is still uncertain. The purpose of this study was to investigate the effect of ankle position during ATFL reconstruction on ankle kinematics, laxity, and in-situ force on the graft. METHODS: Twelve fresh-frozen cadaveric ankles were evaluated. First, ankle specimens were subjected to passive plantarflexion (PF)-dorsiflexion (DF) movement, from 15° DF to 30° PF, using a 6-degrees-of-freedom robotic system. Then, 60 N of anterior- posterior (AP) load, 1.7 Nm of inversion-eversion (IV-EV) torque, and 1.7 Nm of internal-external rotation (IR-ER) torque were applied to the ankle. During testing, 3-dimensional paths of the ankle were recorded simultaneously. In-situ forces on the ATFL and reconstructed graft were calculated using the principle of superposition. A repeat experiment was designed with intact (intact), ATFL transection, and ATFL reconstruction conditions, using 3 different flexion angles (Group A: 0°, Group B: PF 15°, Group C: PF 30°). RESULTS: In ATFL transection condition, the talus was significantly translated anteriorly with internal rotation during PF-DF motion, compared to that in intact condition. In addition, laxity in AP, IV-EV, and IR-ER conditions was significantly greater than in intact condition. In each ATFL reconstruction group, kinematics and laxity showed no significant difference compared to that in intact condition. In intact condition, in-situ force was maximal at PF 30° (19.0±12.0 N). The in-situ force on the reconstructed graft in Group A, B, and C at PF 30° was 50.0±12.4 N, 33.7±13.0 N, and 21.9±7.5 N. The in-situ force in Group A and B was significantly greater than in intact condition. The in-situ force in Group C was not significantly different compared to that in intact condition (Figure 1). CONCLUSION: Ankle position during ATFL reconstruction affected in-situ force on the reconstructed graft. ATFL reconstruction at PF 30° is recommended to avoid excessive in-situ force on the reconstructed graft.