Gait strategy in myelomeningocele : Movements, mechanics and methods

Sammanfattning: The overall aim of this thesis was to describe the movement patterns employed in selfambulatory children with a range of muscle paresis due to nervous tissue damage resulting from myelomeningocele, a common congenital malformation of the spinal column resulting in sensory and motor paresis. Using 3D movement analysis, the upper and lower body kinematics, movement of the center of mass, and joint moments, powers, and work done during gait in 32 children with lumbo-sacral myelomeningocele were analyzed and divided into 5 groups based on the severity of paresis. Characteristic gait patterns were identified and biomechanics of the altered gait were determined. Results were compared with those from 21 control children. The method used to calculate the center of mass was compared against a gold standard method, and theoretical causes of deviations were explored. Children in Group 1 with only incomplete paresis of the plantarflexors and dorsiflexors were less able to control the advancement of the tibia over the foot than the healthy controls, which resulted in a more flexed position of the knees and increased requirement of the knee extensors. Children in Group 2 had complete paresis of the plantarflexors and incomplete paresis of the hip extensors and abductors. Group 2 children compensated for excessive tibial advancement, knee flexion, hip flexion, and anterior trunk tilt with the use of orthoses, which then placed a higher demand at the hip to generate propulsive power. Children in Group 3 had with additional total paresis of the dorsiflexors; and were able to compensate for plantarflexion during swing with orthoses. Group 3 children leaned forward during walking and propagated their centers of mass along a large vertical sinusoidal path. Children in Group 4 had more extensive paresis involving the hip abductors and walked with large lateral and rotational movements of the trunk and pelvis to avoid abductor requirement, which placed their centers of mass over their hip joints. Without orthotic support, a flexed knee gait was observed in Group 4 which placed stress on the knees was typical, but with supported ankles and mediolaterally supported knees, the children were able to stand more upright, extend their knees, take fuller advantage of remaining muscle strength, and propagate along a lateral path while reducing vertical excursions. Finally, children in Group 5, who had only lower limb strength remaining in only hip adductors and flexors and knee extensors, and partial strength in the knee flexors, were unable to walk independently without orthotic support. Group 5 children were able to walk with large upper body motions, an upright trunk and extended knees, via a large lateral path, by taking full advantage of the capacity in remaining musculature and the stability in their orthoses. The use of a full-body model to compute center of mass motion as the centroid of the multi-segment system was compared against a dynamic equilibrium computation of the ground force reactions. The segmental model produced good results in the lateral direction, but may an anterior shift of the computed centroid. The vertical trajectory produced by the segmental model was more credible than the ground force reaction computation due to the latter's hypersensitivity to small errors. This dissertation documented gait using suitable, clinically meaningful, and valid methods in children whose full-body gait is little documented elsewhere. The strategies and mechanisms in which altered gait, non-paretic muscles, and orthotic support are used to compensate for paretic muscles can be used as a reference basis for evaluation of future patients. Consideration to the gait strategy should be given in clinical planning and decisionmaking to ensure that the described gait mechanisms are preserved.