The biomechanics of turning gait in children with cerebral palsy

Turning while walking is a crucial component of locomotion; yet, little is known about how the biomechanics of turning gait differ from those of straight walking. Moreover, it is unclear how populations with restricted gait ability, such as children with cerebral palsy (CP) adapt to turning, compared to their typically developing (TD) peers. Thus, the aims of this thesis were to quantify the biomechanical differences between turning gait and straight walking in TD children and to explore if further, pathology specific, changes present during turning in children with CP. Biomechanical data, including three-dimensional body motion, ground reaction forces, and muscle activity from both groups were collected during straight walking and 90 degree turning gait using motion capture technology. Experimental data were used to compute joint kinematics (angles) and joint kinetics (moments and power) as well as more novel measures to quantify turning fluency and dynamic stability. These data were also used to derive walking simulations using a musculo-skeletal model of the human body in order to quantify muscle contributions to medio-lateral center of mass (COM) acceleration. The results show that both groups preferred to redirect their body during turning about the inside, rather than the outside, limb (with respect to the turn center). For TD children, substantial biomechanical adaptations occurred during turning, compared to straight walking. Furthermore, turning gait simulations reveal that proximal (hip abductors) and distal (ankle plantarflexors) leg muscles were mainly responsible for the redirection of the COM towards the new walking direction during turning. For children with CP, the results suggest that turning gait may be better able to reveal gait abnormalities than straight walking for a number of kinematic and kinetic gait variables. Potentially, analysis of turning gait could improve the identification and management of gait abnormalities in children with CP.This thesis is not currently available in OR

The role of mechanical loading in osteoarthritis of the knee

Medial osteoarthritis (OA) and lateral OA have distinct characteristic cartilage lesion locations and knee flexion angles associated with lesion development. These types of OA are suggested to be caused by loading when the knee is in extension and mid-range flexion, respectively. This project used subject-specific finite element (FE) models to investigate contact conditions within the extended and flexed knee. A method of creating subject-specific FE models by combining geometry (derived from magnetic resonance imaging scans) and load cases (calculated from motion analysis data) collected from the same subject was developed. This model creation method was validated by comparing experimentally-measured pressure data to contact data calculated by FE models. Models of normal knees in three subjects were created first. Models with larger subject-specific loads had larger displacements and higher stresses and contact pressures. Contact occurred over most of the articulating cartilage surfaces, both in areas of typical cartilage lesions and outside areas of typical cartilage lesions. Parameters in the normal models were then altered to reflect three mechanical changes hypothesized to lead to OA: increased loading, globally decreased cartilage stiffness, and locally decreased cartilage stiffness. Increased loading led to increased displacements, stresses, and contact pressures. Contact shifted anteriorly in the extended knee models to locations of typical medial OA cartilage lesions; contact remained stationary with elevated stress magnitudes in the flexed knee models. Globally decreasing cartilage stiffness had limited effects on contact results. Locally decreased cartilage stiffness led to locally increased displacement and strain and locally decreased stress and contact pressure. Contact again shifted anteriorly in the extended knee models. Potential mechanisms of OA initiation were then proposed. Increased weight or locally decreased cartilage stiffness increased strains within the cartilage. High strains can damage the cartilage matrix fibres, further decreasing cartilage stiffness and eventually leading to cartilage lesions and OA.EThOS - Electronic Theses Online ServiceNational Science Foundation (USA)Whitaker International Fellowship (USA)Clarendon ScholarsGBUnited Kingdo

The use of turning tasks in clinical gait analysis for children with cerebral palsy

Background Turning while walking is a crucial component of locomotion that is performed using an outside (step) or inside (spin) limb strategy. The aims of this paper were to determine how children with cerebral palsy perform turning maneuvers and if specific kinematic and kinetic adaptations occur compared to their typically developing peers. Methods Motion capture data from twenty-two children with cerebral palsy and fifty-four typically developing children were collected during straight and 90° turning gait trials. Experimental data were used to compute spatio-temporal parameters, margin of stability, ground reaction force impulse, as well as joint kinematics and kinetics. Findings Both child groups preferred turning using the spin strategy. The group of children with cerebral palsy exhibited the following adaptations during turning gait compared to the typically developing group: stride length was decreased across all phases of the turn with largest effect size for the depart phase (2.02), stride width was reduced during the turn phase, but with a smaller effect size (0.71), and the average margin of stability during the approach phase of turning was reduced (effect size of 0.98). Few overall group differences were found for joint kinematic and kinetic measures; however, in many cases, the intra-subject differences between straight walking and turning gait were larger for the majority of children with cerebral palsy than for the typically developing children. Interpretation In children with cerebral palsy, turning gait may be a better discriminant of pathology than straight walking and could be used to improve the management of gait abnormalities.</p

Paediatric flexible flatfoot: a new stance - beyond static assessment

Flatfoot is often asymptomatic but sometimes presents with symptoms, even in children. This thesis aimed to discover if there was a difference between children with and without symptoms, in the hope that this might aid treatment decisions. Firstly, an audit was performed to discover the prevalence and type of symptoms, as well as current treatment protocols. Secondly, 107 volunteers from the general population and 20 patients were assessed in more detail. The participants were divided into groups and ANOVA tests were used to find the significant differences. Pain and parental concern were frequently reported in the audit population. The majority of this population had moderate bilateral flexible flatfoot with an active Windlass mechanism and static heel valgus. Treatment was dependent on department. The symptomatic group displayed reduced passive ankle dorsiflexion indicating tightness of the tendo-Achilles, as well as increased frequency of severe knee hyperextension and knee valgus upon clinical examination. During static stance, three differences were found between symptomatic and asymptomatic groups, two differences between flat feet and neutral feet. During dynamic trials, the symptomatic group showed reduced stride length and percentage time spent in swing. The ground reaction profiles showed differences in early and late stance. Further investigation supported the idea that decreased late stance vertical ground reaction force peak was evidence of instability in the symptomatic group. Four kinematic parameters demonstrated significant differences at foot strike, five at midstance, and seven at foot off. In terms of kinetics, after controlling for relative stride length, four differences were found, but none between the asymptomatic and symptomatic flat feet. Plantar pressure was successfully used to estimate truncated foot length. The flat feet did not display increased peak midfoot pressure; it was actually lower in flat footed groups. Arch Index and Modified Arch Index were successfully used for instantaneous and continuous assessment of foot posture over stance. The differences found between symptomatic and asymptomatic flat feet (particularly at foot off) shed some light upon the potential causes of symptoms.This thesis is not currently available via ORA