Body Structure/Fxn
PT addressed neuromsk impairments and movement-related body functions and structures
Primary impairments: an immediate result of the existing pathophysiologic process
Secondary Impairments: develop over time as the result of other impairments, activity limitations, participation restrictions or environmental/personal factors
– Msk secondary impairments = contracture, skeletal malalignment–> impact capacity for performance of functional tasks
Muscle Tone and Extensibility
TONE = term that describes the neural and mechanical properties of mm
MUSCLE TONE = normal resting tension or resistance of mm to passive mvmt or mm lengthening — excludes resistance as a result of joint, ligament, or skeletal properties
Hypotonia = diminished resting tone and decreased ability to generate voluntary mm force Hypertonia = abnormal increase in resistance to an external force about a joint resulting from a number of factors (neurally mediated reflex stiffness, passive mm stiffness, and active mm stiffness--> all contribute to resistance to stretch)
Abnormal mm tone not classified as primary or secondary impairment bc:
- develops over time and with increasing attempts to overcome force of gravity and gain mobility
- the early neurally mediated abnormal tone (sign of CP) is compound over time by the addition of mm stiffness and contractures
* * In CP mm tone has been found to increase to age 4 and then decrease up to age 12
SPASTICITY: neural resistance to externally imposted mvmt which increased with increased velocity of stretch and varies with direction of joint mvmt
- may be associated with clonus, pathologic reflexe, and particular patterns of posture and mvmt
- supraspinal and interneuronal mechanisms are responsible for spasticity
PASSIVE MM STIFFNESS: sense of abnormally high tone or hypoextensibility of mm resulting from abnormal mechanical properties
- mm offers resistance to passive stretching at a shorter length than that expected in normal mm
- greater amounts of force are needed to produce a change in length = mm has increased stiffness
CONTRACTURE: when clinician finds that it is not possible to manually stretch the mm through a normal range using reasonable amounts of manual force
- alterations of sarcomere properties of mm, fiber size, type, alignment, and distribution, mm volume and mm stiffness
- it has been noted that spastic tissue has a proliferation of extracellular materials with inferior mechanical properties—> abnormal collagen characteristics
FORCE LENGTH RELATIONSHIP: stretch from PF to DF, in children with CP the maximal forces is lower and the peak force occurs at more plantarflexed position in CP mm vs normal MM (Figure 18-2)
MM growth: mm grow and respond to the amount and type of activity they experience during an activity.
- CP: mm may not relax during activity and children with CP may be subject to mm imbalance, abnormal posturing, and static positioning resulting from spasticity, weakness and abnormal reflex activity
- mm growth may not keep up with bone growth during periods of rapid growth–> contributes to hypoextensibility
MM most commonly at risk for contracture: shoulder adductors, elbow, wrist, finger flexors, hip flexors/ adductors, knee flexors, ankle PF
– GMFCS level does not impact contractures (study found that some children at level I who were ambulatory had contractures and those who were level V did not)
Muscle Strength
Evidence suggests that children with CP are unable to generate normal voluntary force in a mm or normal torque about a joint
- – Decreased force output, a deficiency in power, or when considered over time a deficiency in work
- – diminished force production = primary impairment in CP
MM weakness is consistent with low level of EMG activity and has been attributed to decreased neuronal drive, inappropriate co-activation of antagonist mm groups, secondary myopathy, and alter mm tissue properties
MM shortening and skeletal deformity can lead to changes in level arm biomechanics resulting in decreased output of mm force in terms of torque
Skeletal Structure
Weakness, spasticity, abnormal extensibility and disturbed reflexes can result in abnormal and excessive biomechanical forces —> can compromise joint capsule, ligs, and bones
Torsion of long bones, joint instability, and premature degenerative changes can occur in WB bones
Spine and alignment can be impacted during times of physical growth (scoliosis in CP ranges 15-61% and increases with age and GMFCS level)
Hips: decreased acetabular development and decreased hip stability d/t hip flexion/adduction spasticity
- greater than 30% experience some form of hip displacement
- greater hip displacement seen in higher GMFCS levels
Selective Control
Normal mvmt = orderly phasing in/out of mm activation, coactivation of mm with similar biomechanical functions, and limited coactivation of antagonist mm during phasic or free mvmt
CP = poor selective control of mm activity = impaired ability to isolate the activation of mm in a selected pattern in response to demands of a voluntary posture
Individuals with poor selective control exhibit reduced speed of mvmt, mirror mvmt, or abnormal reciprocal mm activation
May be unable to move joints independently of one another and exhibit coupled flexor or extensor patterns when attempting functional mvmt
Poor selective control = major contributor to impaired motor fxn
** Selective motor control = important predictor of improvement after interventions for other impairments (rhizotomy or mm lengthening)
Postural Control
Postural control = ability to control the position of the center of mass over the BOS, involves coordination of sensory, motor, and msk system for postural activity
Children with CP have dysfunction in responding to postural challenges and have difficulty fine-tuning postural activity
Reactive postural adjustments occur in response to unexpected external postural perturbations— in children with CP these responses vary based on level of severity
- GMFCS Level I-II have some ability to produce direction specific adjustments to counteract forces disturbing equilibrium through reactive control
- Abilities decrease as GMFCS level increase, largely absent in children at GMFCS level 5
Anticipatory postural responses are related to expected internal postural perturbations preceding the onset of voluntary motor mvmt
- – typical individuals changes in posture and preceded by preparatory mm contractions that stabilize the body and allow weight shifts in anticipation of mvmt while keeping the COM with in stability limits of the body
- – CP have characteristics of disorganization and/or adaptions including: cranial caudal recruitment of postural mm, excessive antagonistic co activation and reduced/absent capacity to adapt the degree of mm contraction as appropriate to the specific task or situation
Motor Learning
Motor learning = set of processes associated with practice or expertise that leads to relatively permanent change in the ability to produce a skilled action
Children with CP and be constrained in their ability to learn mvmt strategies bc of impairments like, spasticity, weakness, limited sensation, perceptual motor skills, cognition and lack of opportunities to experience motor skills in variable settings
- have difficulty analyzing own mvmt and using feedback on performance
- frequently have impaired motor memory
Pain
secondary impairment that affects other body functions and structures, levels of participation and QOL
can result from primary impairments, overuse syndromes, interventions (surgery, equipment use, injections, rehab)
Chronic pn may contribute to depression, sleep disturbances, fatigue and reduced physical functioning
Pn is experience by ambulatory and non ambulatory children
Activity and Participation
motor skills vary greatly among children with CP
Factors identified by pediatric PT’s influential in bringing about change in motor ability of children with CP: mm tone, mvmt patterns and selective control, force production, endurance, family factors, and personality characteristics
Many parents become preoccupied with walking– frequent goal of families, predictor of participation, and skill that can deteriorate over time
– walking not always a realistic mode for mobility
Children with Cp experience restrictions in participation compared to children of general pop
Factors associated with participation: physical environment, GMFCS level, hand fxn, and cognition
– one study found that walking ability was greatest predictor of participation
Participation in physical activity is particularly important for children with CP
