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.
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ItemMusculoskeletal model for gait analysis in people with partial foot amputation( 2015)Partial foot amputation is the most common amputation performed in the world today. In Australia, over 74% of all lower limb amputations are partial foot amputations. Diabetic patients are 15 times more likely to have an amputation than people without diabetes. Despite the prevalence of partial foot amputation, the influence of different levels of amputation on the biomechanics of gait is not well understood. This research project aimed to develop subject-specific musculoskeletal models to simulate and analyse gait in people with partial foot amputation, including quantification of the forces developed in the lower limb muscles during walking. One subject with transmetatarsal amputation and another with metatarsophalangeal amputation were selected based on inclusion criteria. In the transmetatarsal subject, the effects of compromised metatarsals on spatiotemporal data, kinematics, kinetics and individual muscle forces were compared with those of a control subject with metatarsophalangeal amputation through toes. The validation of developed models showed that predicted joint angles and joint moments were comparable to those reported in another study so developed musculoskeletal models for subjects were used for individual muscle force prediction of lower limb muscles during stance. For some muscles, the timing of forces predicted by the models and the timing of their EMG data were comparable so the forces predicted for muscles were reliable so far. The results showed that once the metatarsals are compromised through transmetatarsal amputation, some gait abnormalities were observed. These changes in gait were caused by an inability to generate power across the ankle joint. In the residual limb with transmetatarsal amputation, the reduction in the magnitude of the net ankle joint moment was associated with the reduction in the calf muscle forces during terminal stance and pre-swing of the gait. Compromised metatarsals through transmetatarsal amputation may impair the biomechanics of gait significantly through the reduction in the capacity of calf muscle forces to plantar flex the ankle and generate the necessary ankle torque to propel the residual limb.
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ItemLower-limb muscle forces and patellofemoral joint loading in people with and without patellofemoral osteoarthritis during walking and stair ambulation( 2012)Osteoarthritis (OA) is a chronic degenerative joint disease that is the leading cause of musculoskeletal pain and disability in Australia. OA often affects the knee joint and commonly occurs between the patella (knee cap) and femur (thigh bone), known as patellofemoral joint osteoarthritis (PFJ OA). PFJ OA is highly prevalent in elderly populations and is more common than tibiofemoral joint osteoarthritis (TFJ OA). Despite the differences in prevalence, PFJ OA is less studied than TFJ OA. The mechanical loading transferred through a joint is generally thought to play a major role in OA initiation and progression via the lifelong “wear and tear” of a joint’s articular cartilage. Alterations to gait patterns and muscle dysfunction are commonly observed in people with knee disorders. However, little is known on how these changes actually combine to alter patellofemoral joint (PFJ) loading. The use of computational models is becoming a popular approach to quantify in vivo muscle forces and joint contact forces in healthy individuals during common activities. However, these models have rarely been applied to pathological populations, such as PFJ OA. Given the dearth of knowledge in the gait characteristics, in vivo muscle function and PFJ joint loading in the PFJ OA population, the purpose of this study was to investigate the joint kinematics, joint moments, muscle forces and PFJ loading in individuals with and without PFJ OA during three common activities of daily life: (1) overground walking, (2) stair ascent and (3) stair descent. Four specific research questions are addressed in this thesis. 1. Do people with PFJ OA demonstrate altered trunk and lower-limb joint biomechanics in comparison to people without PFJ OA during walking and stair ambulation? 2. Do people with PFJ OA demonstrate differences in hip and knee muscle forces when compared to controls during walking and stair ambulation? 3. Is the patellofemoral joint reaction force different in people with and without PFJ OA during walking and stair ambulation? 4. Are there biomechanical characteristics that distinguish people with isolated PFJ OA from people with concurrent TFJ OA and PFJ OA? Quantitative gait experiments and computational modelling were utilised to address the above research questions. The main findings of this study were that subjects with PFJ OA (with and without concurrent TFJ OA) adopted activity-specific gait modifications to off-load the PFJ. Specifically, participants with PFJ OA chose to alter their sagittal-plane kinematics, such as increased anterior pelvic tilt and/or decreased knee flexion, during stair ambulation to reduce the knee extension moment, quadriceps force and the patellofemoral joint reaction force. PFJ OA participants also walked and descended stairs with lower hip abductor muscle forces and lower knee adduction moments, which may represent a frontal-plane adaptation to off-load the PFJ. The alterations in quadriceps and hip abductor muscle forces observed in the individuals with PFJ OA suggest that hip and knee muscle dysfunction may be characteristic features of the PFJ OA population. These findings indicate the importance of including the PFJ and the dynamics of joints proximal to the knee when investigating the knee OA disease process.