A multisegmental foot model with bone-based referencing: Sensitivity to radiographic input parameters

We present a new kinematic model measuring the three-dimensional orientation of multiple segments of the foot and ankle. The model defines neutral alignments based on the alignments of the underlying bony segments, and indexes the orientation of skin-mounted markers to the bony anatomy using measures from weightbearing x-rays. The sensitivity of the model to these radiographic input parameters was analyzed using data from walking trials. Kinematic output in each plane was found to be most sensitive to perturbations of radiographic measurements in that same plane; however, perturbations in the coronal and transverse planes demonstrated significant carry-over into other planes. The analysis highlights the importance of accurately accounting for the underlying anatomy in measuring intersegmental kinematics.