Mechanical Engineering - Theses
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ItemEffect of lower-limb torsional deformities on muscle and joint function during gait( 2017)Torsional deformities of the femur and tibia have been associated with walking difficulties, lower-limb pain and joint dysfunction. Patients presenting with torsional deformities typically undergo medical imaging and 3D gait analysis, prior to consideration of surgical correction. To date, much of the research has focused on kinematic and kinetic deviations during gait. However, little is known in regards to the effect of torsional deformities on muscle and joint contact forces. The overall goal of this dissertation was to understand the effect of lower-limb torsional deformities on muscle and joint function during gait, to improve surgical decision-making and hence clinical outcomes. Prior to addressing the overall goal of this dissertation we investigated three key areas; 1) the evaluation of suitable clinical methods for the measurement of lower-limb torsion, 2) determining accurate anatomical based joint parameters (joint centres and axes) for the lower-limbs and 3) separating the effects of bone geometry (lower-limb torsion) and joint parameters on musculoskeletal modelling results (kinematics, kinetics, muscle-tendon unit lengths, muscle moment arms, muscle forces and joint contact forces). Various clinical methods of measuring lower-limb torsion were compared to the gold standard, computed tomography (CT) measurements. Physical examination measurements were unreliable, showing poor agreement with measurements from CT. Freehand 3D ultrasound and low dose biplanar radiography (EOS imaging) showed good agreement with measurements from CT. Validation of methods to determine joint centres and axes has been limited, often assessed with indirect outcome measures. For this study, patient-specific joint parameters were identified from low dose biplanar radiography and registered with respect to the skin markers used during 3D gait analysis. This was done for the hip joint centre, condylar axis (knee axis) and bimalleolar axis (ankle axis). This method was used as a reference to evaluate previously described methods. For the hip joint centre recent regression equations obtained from CT or magnetic resonance imaging showed good agreement with the reference, with the majority being less than 30mm from the reference. For the condylar axis both the conventional gait model and functional calibration methods were unreliable. Freehand 3D ultrasound imaging showed the closest results to the reference. The separate effects of bone geometry and joint parameters on the results from musculoskeletal modelling were investigated. Joint parameters had a significant effect on the kinematics, kinetics and hip and knee joint contact forces. Bone geometry had a significant effect on the muscle forces and hip and knee joint contact forces. Both bone geometry and joint parameters where deemed necessary inclusions in patient-specific musculoskeletal models. To address the overall goal of the dissertation we investigated the relationship between lower-limb torsional deformities, physical examination measures, gait parameters (kinematics, kinetics, muscle forces and joint contact forces) and pain in two clinical populations; children with idiopathic torsion and children with spastic diplegic cerebral palsy. This was done by creating musculoskeletal models with patient-specific anatomy, accurately registered to the skin markers used during 3D gait analysis. These models were created using low dose biplanar radiographs combined with 3D gait analysis. This investigation showed that both patients with idiopathic torsion and those with spastic cerebral palsy have similar gait deviations. However, the cerebral palsy patients showed additional gait deviations likely the result of muscle spasticity, muscle weakness and impaired selective motor control. Additionally, lower-limb torsion and joint contact forces were predictors of pain in both populations. This dissertation presents clinically feasible methods for the creation of musculoskeletal models on a patient-specific basis. This is the first study to combine low dose biplanar radiography with 3D gait analysis to obtain patient-specific musculoskeletal models. These models have the advantage of registering patient-specific anatomy with respect to the skin markers in a standing position, with short scan times (10 seconds) and low radiation exposure.