Cerebral palsy
Skeleton

For bones to attain their normal shape and size, they require the stresses from normal musculature. People with cerebral palsy are at risk of low bone mineral density. The shafts of the bones are often thin (gracile), and become thinner during growth. When compared to these thin shafts (diaphyses), the centres (metaphyses) often appear quite enlarged (ballooning). Due to more than normal joint compression caused by muscular imbalances, articular cartilage may atrophy, leading to narrowed joint spaces. Depending on the degree of spasticity, a person with the spastic form of CP may exhibit a variety of angular joint deformities. Because vertebral bodies need vertical gravitational loading forces to develop properly, spasticity and an abnormal gait can hinder proper or full bone and skeletal development. People with CP tend to be shorter in height than the average person because their bones are not allowed to grow to their full potential. Sometimes bones grow to different lengths, so the person may have one leg longer than the other.

Children with CP are prone to low trauma fractures, particularly children with higher Gross Motor Function Classification System (GMFCS) levels who cannot walk. This further affects a child's mobility, strength, and experience of pain, and can lead to missed schooling or child abuse suspicions. These children generally have fractures in the legs, whereas non-affected children mostly fracture their arms in the context of sporting activities.

Hip dislocation and ankle equinus or plantar flexion deformity are the two most common deformities among children with cerebral palsy. Additionally, flexion deformity of the hip and knee can occur. Torsional deformities of long bones such as the femur and tibia are also encountered, among others. Children may develop scoliosis before the age of 10 – estimated prevalence of scoliosis in children with CP is between 21% and 64%. Higher levels of impairment on the GMFCS are associated with scoliosis and hip dislocation. Scoliosis can be corrected with surgery, but CP makes surgical complications more likely, even with improved techniques. Hip migration can be managed by soft tissue procedures such as adductor musculature release. Advanced degrees of hip migration or dislocation can be managed by more extensive procedures such as femoral and pelvic corrective osteotomies. Both soft tissue and bony procedures aim at prevention of hip dislocation in the early phases or aim at hip containment and restoration of anatomy in the late phases of disease. Equinus deformity is managed by conservative methods especially when dynamic. If fixed/static deformity ensues surgery may become mandatory.

Growth spurts during puberty can make walking more difficult for people with CP and high muscle tone.
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