Satoshi Yamakawa

The in situ force in the calcaneofibular ligament and the contribution of this ligament to ankle joint stability

BACKGROUND Numerous biomechanical studies of the lateral ankle ligaments have been reported; however, the isolated function of the calcaneofibular ligament has not been clarified. We hypothesize that the calcaneofibular ligament would stabilize the ankle joint complex under multidirectional loading, and that the in situ force in the calcaneofibular ligament would change in each flexed position. METHODS Using seven fresh frozen cadaveric lower extremities, the motions and forces of the intact ankle under multidirectional loading were recorded using a 6-degree-of-freedom robotic system. On repeating these intact ankle joint complex motions after the calcaneofibular ligament transection, the in situ force in the calcaneofibular ligament and the contribution of the calcaneofibular ligament to ankle joint complex stability were calculated. Finally, the motions of the calcaneofibular ligament-transected ankle joint complex were recorded. FINDINGS Under an inversion load, significant increases of inversion angle were observed in all the flexed positions following calcaneofibular ligament transection, and the calcaneofibular ligament accounted for 50%-70% of ankle joint complex stability during inversion. The in situ forces in the calcaneofibular ligament under an anterior force, inversion moment, and external rotation moment were larger in the dorsiflexed position than in the plantarflexed position. INTERPRETATION The calcaneofibular ligament plays a role in stabilizing the ankle joint complex to multidirectional loads and the role differs with load directions. The in situ force of the calcaneofibular ligament is larger at the dorsiflexed position. This ligament provides the primary restraint to the inversion ankle stability.

Static and Dynamic Properties of a 6-DOF Robotic System for Knee Joint Biomechanics Study

The application of robotic technology to the field of joint biomechaics has started more than 20 years ago1). Since then, a variety of studies have employed commercially available articulated manipulators for the joint biomechanical studies1–5). However, such articulated manipulators are generally poor at stiffness and precision although they were basically designed to achieve high speeds of motion while performing tasks in a large work space. To solve the problem, we have previously developed a robotic system consisting of a custom-made 6-degree of freedom (6-DOF) manipulator and a universal force-moment sensor (UFS)6). The present study was aimed to evaluate the static and dynamic properties of the system.Copyright

Effect of Initial Graft Tension During Calcaneofibular Ligament Reconstruction on Ankle Kinematics and Laxity

Background: Although a variety of surgical procedures for lateral ankle ligament reconstruction have frequently been reported, little is known about the effects of initial graft tension. Purpose/Hypothesis: The purpose was to investigate the effects of initial graft tension in calcaneofibular ligament (CFL) reconstruction. It was hypothesized that a high degree of initial graft tension would cause abnormal kinematics, laxity, and excessive graft tension. Study Design: Controlled laboratory study. Methods: Twelve cadaveric ankles were tested with a 6 degrees of freedom robotic system to apply passive plantarflexion-dorsiflexion motion and multidirectional loads. A repeated-measures experiment was designed with the CFL intact, CFL transected, and CFL reconstructed with 4 initial tension conditions (10, 30, 50, and 70 N). The 3-dimensional path and reconstructed graft tension were simultaneously recorded. Results: The calcaneus in CFL reconstruction with an initial tension of 70 N had the most eversion relative to the intact condition (mean eversion translations of 1.2, 3.0, 5.0, and 6.2 mm were observed at initial tensions of 10, 30, 50, and 70 N, respectively). The calcaneus also moved more posteriorly with external rotation as the initial tension increased. The reconstructed graft tension tended to increase as the initial tension increased. Conclusion: Ankle kinematic patterns and laxity after CFL reconstruction tended to become more abnormal as the initial graft tension increased at the time of surgery. Moreover, excessive initial graft tension caused excessive tension on the reconstructed graft. Clinical Relevance: This study indicated the importance of initial graft tension during CFL reconstruction. Overtensioning during CFL reconstruction should be avoided to imitate a normal ankle.

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.Copyright