Functional Scaling of Musculoskeletal Models

The validity of the predictions from musculoskeletal models depends largely on how well the morphology of the model matches that of the patient. To address this problem, we present a novel method to scale a cadaver-based musculoskeletal model to match both the segment lengths and joint parameters specific to the patient. This is accomplished using optimisation methods to determine patient-specific joint positions and orientations, which minimise the least-squares error between model markers and the recorded markers from a motion capture experiment.
Functional joint positions and joint axis orientations are then used to morph/scale a cadaver based musculoskeletal model using a set of radial basis functions (RBFs).
Using the functional joint axes to scale musculoskeletal models provides a better fit to the marker data, and allows for representation of patients with considerable difference in bone geometry, without the need for MR/CT scans. However, more validation activities are needed to better understand the effect of morphing musculoskeletal models based on functional joint parameters.