Discrete element method simulator for joint dynamics: a case study using a red-tailed hawk’s hallux digit

A discrete element method simulator is developed, which models all of the components (bones, tendons, and ligaments) as discrete elements. This simulator is then used to simulate the dynamics of a raptor’s hallux digit as a case study. The biomechanical linkage is constructed from computerized tomography (CT) scans of bones. The ligaments and tendons are attached to the anatomical landmarks of the bones. This model approximates the multibody dynamics of a biomechanical linkage without making kinematic assumptions on the bones’ movements in relationship to each other. The nonlinear dynamics resulting from the bones’ geometric shape and the complex distribution of forces from the soft tissue is approximated with this discrete element method simulation approach. A dynamic simulation of a hallux digit is shown, and the force distribution within the joint is also provided at different points in time. This discrete element method simulator for joint dynamics relies on few assumptions and could be readily applied to more complex biomechanical linkages. This novel method for the dynamic simulation of biomechanical linkages is very general and flexible. Since the dynamics of biomechanical linkages relies on contacting features, these systems exhibit small-scale phenomena. For this reason, the discrete element method is computationally favorable when compared to finite element methods.