Work contained in this thesis describes a new biomechanical model for clinical
gait analysis. Identified problems with current models are related to the subjective
reasonableness of their underlying modelling assumptions and used to guide
development of a new model.
Gait scores were developed to evaluate alternative modelling solutions in terms
of cycle average position, range, inter-cycle variability and movement pattern. An
overly simple pro-forma model was developed to facilitate evaluation of the
effects of complexity from alternative modelling approaches, both existing and
newly developed.
A clinical interpretation of Euler angles, widely used to describe joint orientations
and movements, is presented. Leading directly from this interpretation, simple,
joint-specific rules are derived that ensure calculated angles match clinical
terminology. Other identified concerns are tackled on a per body-segment basis,
with each segment presenting a different challenge.
Identified problems with current trunk models were related to difficulties of
orientating and tracking movement of the whole based on a selected sub-region.
This was solved via the development of a more holistic solution, which
additionally reduces the need for patient upper body exposure.
For the pelvis and thigh segments, excessive soft tissue cover was identified as
the major issue and resolved by the amalgamation of published methods with the
novel introduction of fixed length thigh segments and a bespoke axial alignment
calibration procedure.
Foot model accuracy was improved by the application of bespoke calibration(s)
that relates a defining flat foot posture to the position of surface markers, thus
reducing the requirement for accurate placement over bony landmarks. Existing
multi-segment foot models were grouped by a novel complexity index. Analysis
of each group revealed an optimal balance with hind, medial forefoot, and lateral
forefoot divisions. A model with this configuration was developed and outputs
related to existing clinical terminology describing the foot shape.