Kyung Hee University, KOREA The effect of ankle joint plantar and dorsiflexion to the mechanism of lateral ankle sprain Myagmarbayar Batbaatar, Tserenchimed Purevsuren, Kyungsoo Kim and Yoon Hyuk Kim Kyung Hee University, KOREA #1098 INTRODUCTION Among ligament injury in ankle, 77-80% were lateral ankle sprain (LAS). There is almost consistent belief that there are three major factors (ankle inversion, internal rotation, and plantar-flexion) in LAS mechanism [1]. However, a recently published study [2] in which accidental ankle injuries were evaluated showed that ankle dorsiflexion also play important role in LAS. Thus, the previous belief that the plantarflexion is necessary component in LAS mechanism has been remain controversial. Loading and boundary conditions RESULTS Validation of the developed the dynamic model of the ankle model joint – Syndesmotic test In this study, we evaluated contribution of the ankle plantarflexion and dorsiflexion to LAS injury mechanism while complex combination of internal and inversion torque acting on the ankle joint. OBJECTIVE MATERIALS & METHODS A three-dimensional multibody dynamic model of the ankle joint (26 year old male subject) with 28 bones, 24 linear elastic ligaments, and 6 articular contacts was developed using a commercial multibody dynamics software (RecurDyn V8). Two kinds of tests were performed to validate multibody ankle joint model. A syndesmotic ankle injury test: The compressive force of 67 N was applied to proximal tibia. The tibia was then internally rotated to simulate external foot rotation under internal tibial torque of 2.7 Nm [3]. Ligament strain test: The continuous ankle flexion (form 20° dorsiflexion to 30° plantarflexion) was applied in the model, while applying internal and external moments of 3 Nm on the talus [4]. To investigate contribution of the ankle joint plantar and dorsiflexion to LAS mechanism, internal moment coupled with inversion torque (both ranging from 0 to 21 Nm with increments of 3 Nm) was applied to the ankle joint model, when ankle flexion angle was varied. Validation of the developed the dynamic model of the ankle model joint – Ligament strain test DISCUSSION The results of this study showed that Calcaneofibular ligament (CaFL) was stretched during dorsiflexion under high ankle inversion torque and no CaFL ligament injury was observed in the ankle plantar flexion posture. The Anterior Talofibular ligament (ATaFL) tear was expected during ankle dorsiflexion under high internal rotation torque. At neutral position and early plantarflexion (0° to 30° of plantarflexion), ATaFL tear was expected under different combination of ankle inversion torque coupled with internal rotational moment. In high ankle plantarflexion (40°-60° of planatarflexion), ATaFL tear was expected under relative low loading conditions. Simulated lateral ankle sprain test [1] JR. Funk et al., Clin Anat., 24 (3), 2011. [2] DT. Fong et al., Foot ankle int., 37 (4), 2009. [3] MR. Colville et al., Am J sports Med., 18 (2), 1990. [4] Marqueen et al., Foot ankle int., 26 (3), 2005. REFERENCES