Reasons for performing study: The finite element (FE) method is the most powerful modelling technique available to explicate the biomechanics of the digit. It has already proved to be of high value in human podiatry. However, accurate models of the complex anatomy of the horse and donkey digit are currently lacking.
Objectives: To develop FE models of the horse and donkey digit from computed tomography data, including all functionally relevant anatomy, and to perform simulations to replicate prestrain in the flexor tendons and quasistatic weightbearing.
Methods: Computed tomography data of the front right digits were obtained under general anaesthesia. The anatomy was rationalised into 32 functional components. The FE models were generated using a forward engineering technique. Linear or nonlinear material properties were applied according to published data. Prestraining of the flexor tendons was achieved by z-direction displacement, and loading by the application of 1 x body mass.
Results: The resultant FE models comprised over 10^6 elements. Z-direction displacement of the digital flexor tendons to compensate for general anaesthesia relaxation gave von Mises stress levels up to 1.34 MPa for the deep and 0.56 MPa for the superficial in the horse and 0.78 MPa and 0.27 MPa in the donkey, respectively. Weightbearing resulted in capsular deformation patterns consistent with in vivo observations, and maximum stress levels of 1.46 MPa for the horse and 0.89 MPa for the donkey.
Conclusion: These high resolution FE models could give new insight into the biomechanics of the equid digit and provide new data regarding stress and strain levels within the tissues of the digit that are unobtainable by other means.
Potential relevance: Application of the FE modelling technique could enable investigation of the biomechanics of orthopaedic problems and may provide a mechanistic basis for enhanced preventative and remedial management and treatment.