Modelling the German Shepherd lumbosacral spine and pelvis

Sophie Reed is nearing the completion of a one year Master’s project funded by the Centre. She is developing a preliminary model of the German Shepherd lumbosacral spine and pelvis using a proprietary (AnyBody®) musculoskeletal modelling package. After CT of an intact German Shepherd cadaver, dissection of the soft tissues was undertaken to map, in detail, all of the individual muscles and ligaments crossing the joints of the caudal spine and pelvis and to record the morphology of each muscle. Calibrated three-dimensional coordinates of muscle origins and insertions were obtained with a 3D camera system (Qualisys®). Muscle mass and volume, pennation angles, fibre lengths and sarcomere lengths are recorded to calculate a muscle’s optimal fibre length and physiological cross-sectional area for description in the model of an individual muscle’s contractile properties. Ligament properties are described in the model according to values in the literature for stress-strain relationships based on cross-sectional area. Following dissection of the soft tissues, the individual bony elements of the spine and pelvis were macerated and dried, and separate CT images generated to represent the individual spinal elements in the model. These were put back together as an articulated spine and pelvis using SolidWorks® and the muscles added as vectors between origins and insertions with contractile properties. Sophie is currently working on the final part of her project, which is to assess the impact of variability of some of the muscle inputs, in a sensitivity analysis.

This is a preliminary model that uses data from the literature to estimate joint centres of rotation, and joint motion constraints. To do this more accurately, and more specifically for the GS spine, we will need to collect 3D motion data from another similar spine after removal of the muscles. The longer term aim is to build a model of the entire dog for the study of the injury of limb joints as well as the spine joints. With this, we will be able to collect 3D motion and force data from the dog performing a variety of gait and other motor functions for inclusion as input variables to the model.

On the strength of Sophie’s work to date, and other funding from the Equine Trust to develop a musculoskeletal model of the equine limb for testing equestrian riding surfaces, researchers have been successful in obtaining a Catalyst grant from the Royal Society to run a workshop in Denmark with European collaborators from Vienna and Ghent. They have similar interests in working dogs and horses, and collaboration with them will enable us to apply for EU funding to continue this work.