The Use of a 6-DOF Robotic System for the Functional Analysis of Ankle Joint Ligaments

Ankle sprains are common injuries in daily and athletic activities. An epidemiological report indicated that the incidence rate of ankle sprains treated in emergency departments in the USA is more than 2 per 1000 persons a year, and the rate is estimated to be more than double as for ankle sprains in athletic activity [1]. Better understanding of ankle biomechanics is, therefore, important for the improvement of clinical outcome. Many investigators have performed in vitro and in vivo experiments to determine the mechanical roles of ankle structures such as range of motion, contribution of ankle ligaments to joint stability, joint instability due to ligament transection, and so on. In spite of these efforts, tensile forces in ankle ligaments in response to specific loading conditions still remains unclear because of a lack of experimental methodology. Meanwhile, the use of robotic technology for knee joint biomechanics study has been established by Fujie et al [2]. Using the technique, tensile forces in knee cruciate ligaments have been determined by Woo et al [3], Li et al [4], Fujie et al [5], and other groups, while ligament reconstruction technique has been evaluated by many investigators [for example 6–8]. Therefore, the objectives of the present study were to determine the ankle joint instability due to ligament transection and to determine the tensile forces in the anterior tarofibular ligament (ATFL) and calcaneofibular ligament (CFL) in response to anterior-posterior (AP) drawer force to the human cadaveric ankle joints.