Computer Modeling of Crouch Gait in CP Children

Cerebral palsy is a leading disorder of the developing brain. One of the most common movement abnormalities among children with cerebral palsy is the crouch gait. Crouch gait is characterised primarily by excessive flexion of the knee during stance, although exaggerated flexion, adduction, and internal rotation of the hips are also often observed. Gait analysis techniques have led to a more objective assessment of movement abnormalities in children with cerebral palsy, however, this approach cannot be used to specify the actions of individual leg muscles during walking. There are several reasons: first, each body joint is spanned by several extensor and flexor muscles, and a net joint moment can be produced by an infinite combination of muscle forces; second, muscle EMG recordings determine only whether a muscle is active and give no information on the amount of force that the muscle might be producing during dynamic activity; and third, because muscles can accelerate joints they do not span, gait data alone cannot be used to describe and explain how individual muscles coordinate movement of the lower limbs during walking. In contrast, computer modeling combined with a concept known as `induced accelerations analysis` can be used to provide a more quantitative understanding of muscle function during normal walking and crouch gait. The overall goal of the proposed project is to combine musculoskeletal modeling with optimization theory to assess lower-limb muscle function when healthy children walk at their natural speeds, and when children with cerebral palsy walk with a crouch gait. We propose to develop musculoskeletal models of five healthy 8-year-old children and patient-specific musculoskeletal models of three 8-year-old children with spastic diplegia using MR imaging. Static optimization and gait data will be used to calculate the time histories of forces developed by 62 major muscle groups in the lower limb. Induced acceleration analysis will then be used to describe, explain, compare, and contrast the function of individual leg muscles during normal and crouch gait. The results of our work will be significant on a number of levels. First, new data describing the musculoskeletal geometry and physiological properties of all the major lower-limb muscles in both healthy children and children with cerebral palsy will be obtained. Second, our estimates of muscle lengths and muscle forces in children with cerebral palsy will take into account bony deformities, such as femoral anteversion, which are commonly observed in patients exhibiting crouch gait. Third, because our calculations will reveal the time histories of leg muscle forces developed during the gait cycle, our results will show whether leg-muscle function is the same in both healthy children and adults. No information is available on leg-muscle function during walking even in healthy children. Fourth, information about the time histories of leg-muscle forces during walking will be valuable to surgeons and physical therapists not only in the pre-operative planning of muscle-tendon lengthening and transfer procedures, but also in designing the most appropriate methods for rehabilitation (e.g., prescribing the correct orthosis to treat a specific abnormality).

Cerebral palsy is a leading disorder of the developing brain. One of the most common movement abnormalities among children with cerebral palsy is the crouch gait. Crouch gait is characterised primarily by excessive flexion of the knee during stance, although exaggerated flexion, adduction, and internal rotation of the hips are also often observed. Gait analysis techniques have led to a more objective assessment of movement abnormalities in children with cerebral palsy, however, this approach cannot be used to specify the actions of individual leg muscles during walking. There are several reasons: first, each body joint is spanned by several extensor and flexor muscles, and a net joint moment can be produced by an infinite combination of muscle forces; second, muscle EMG recordings determine only whether a muscle is active and give no information on the amount of force that the muscle might be producing during dynamic activity; and third, because muscles can accelerate joints they do not span, gait data alone cannot be used to describe and explain how individual muscles coordinate movement of the lower limbs during walking. In contrast, computer modeling combined with a concept known as "induced accelerations analysis" can be used to provide a more quantitative understanding of muscle function during normal walking and crouch gait. The overall goal of the proposed project is to combine musculoskeletal modeling with optimization theory to assess lower-limb muscle function when healthy children walk at their natural speeds, and when children with cerebral palsy walk with a crouch gait. We propose to develop musculoskeletal models of five healthy 8-year-old children and patient-specific musculoskeletal models of three 8-year-old children with spastic diplegia using MR imaging. Static optimization and gait data will be used to calculate the time histories of forces developed by 62 major muscle groups in the lower limb. Induced acceleration analysis will then be used to describe, explain, compare, and contrast the function of individual leg muscles during normal and crouch gait. The results of our work will be significant on a number of levels. First, new data describing the musculoskeletal geometry and physiological properties of all the major lower-limb muscles in both healthy children and children with cerebral palsy will be obtained. Second, our estimates of muscle lengths and muscle forces in children with cerebral palsy will take into account bony deformities, such as femoral anteversion, which are commonly observed in patients exhibiting crouch gait. Third, because our calculations will reveal the time histories of leg muscle forces developed during the gait cycle, our results will show whether leg-muscle function is the same in both healthy children and adults. No information is available on leg-muscle function during walking even in healthy children. Fourth, information about the time histories of leg-muscle forces during walking will be valuable to surgeons and physical therapists not only in the pre-operative planning of muscle-tendon lengthening and transfer procedures, but also in designing the most appropriate methods for rehabilitation (e.g., prescribing the correct orthosis to treat a specific abnormality).