A biomechanical analysis of the trunk and spine during paediatric cerebral palsy gait

THESIS 11497Movement pathologies in the lower limbs of children with cerebral palsy are well established in the literature. However, movement pathologies of the upper body, in particular the trunk, are less well defined. Mechanical loads at the spine and the surrounding areas are influenced by gravity, inertia and externally applied loads and pathological motion patterns could result in mechanical changes in structural tissue surrounding the spine over time. Consequently, this thesis reports an investigation into the relationship between pathological movement of the trunk and loading at the lower lumbar spine. The specific impact of Trendelenburg and Duchenne type movement patterns on loading at the lower lumbar spine was also examined. Prior to assessment, the role of gait analysis in the assessment of trunk and lower lumbar spinal loading was considered. This highlighted a number of issues relating to the kinematic and kinetic models that warranted further investigation. Specifically, those issues related to (1) the choice of body segment parameter set, (2) the choice of hip joint centre regression equation set, (3) the thorax kinematic protocol and (4) the lumbar segment kinematic protocol. Before data were collected to address the primary goals of the thesis, a number of preparatory studies were therefore conducted. The first two preparatory studies identified the most suitable choice of body segment parameter and hip joint centre regression equation sets for the purposes of this thesis. Next, a thorax kinematic protocol was proposed to address some of the practical issues experienced when using other protocols during the assessment procedure. As a preliminary evaluation before use, the protocol was compared to two reference protocols from the literature and performed well and was later used in the thesis. A separate investigation into choice of lumbar segment kinematic protocol identified a skin surface protocol as suitable for studies where axial rotation may be a consideration and so was used in this thesis. With the kinematic and kinetic models in place, 3-dimensional thoracic, lumbar and L5/S1 kinetics were measured in 52 children with cerebral palsy and 26 typically developed children. Differences were present for cerebral palsy children, most notably in the coronal plane for thorax kinematics and L5/S1 kinetics. Peak L5/S1 moment data were up to 21% higher than normal for GMFCS level one children and up to 90% higher than normal for GMFCS level two children. Moderate to strong correlations were evident between movement of the thorax and L5/S1 loading (r = 0.52). However, other factors may have contributed to this loading and further investigation was suggested, perhaps by means of forward dynamics, to determine other underlying factors that may contribute to this loading. The final investigation of this thesis examined the impact of Duchenne and Trendelenburg type gait on loading at the lower lumbar spine in children with cerebral palsy. The same cohort of subjects was divided according to clinical presentation of each pattern. Trendelenburg gait had little impact on L5/S1 loading. However, increased loading was evident where Duchenne type movements were present. To conclude, increased loading was evident at the lower lumbar spine during cerebral palsy gait. This loading was related to the position of the thorax. It is important that interventions relating to movement of the trunk during cerebral palsy gait, or specifically related to Duchenne or complex Trendelenburg-Duchenne type gait, are aimed at reducing trunk motion specifically in the coronal plane in order to reduce abnormal loading which could, in turn, impact the health of the spine in this population