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Alterations of Musculoskeletal Function in ChildrenChapter 43

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Bone Formation Bone formation begins in two phases at about

the eighth week of gestation Delivery of bone cell precursors to sites of bone

formation Aggregation of the bone cell precursors at

primary centers of ossification

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Bone Formation Intramembranous formation

On or within the mesenchyme Endochondral formation

Cartilage anlage Perichondrium Periosteal collar Secondary centers of ossification

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Bone Formation

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Bone Growth Until adult stature is achieved, bone growth

occurs at the epiphyseal plate through endochondral ossification

Factors affecting bone growth Growth hormone Nutrition General health Many growth factors and regulators

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Skeletal Development In the newborn, the entire spine is concave

anteriorly (kyphosed) In the first 3 months of life, the cervical spine

begins to arch (lordotic) Curve of the lumbar spine develops with sitting Compared to an adult, a newborn has a large

head, long spine, and short extremities

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Skeletal Development Genu varum (peaks by 2½ years)

Bowleg Genu valgum (5-6 years)

Knock-knee

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Muscle Development Between birth and maturity, muscle nuclei in

the body increase 14 times in boys and 10 times in girls

The composition and size of muscles vary with age

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Congenital Defects Syndactyly

Webbing of the fingers Fusion of the soft tissues of the fingers True syndactyly also includes fusion of the bones

and nails Vestigial tabs

Extra digit

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Syndactyly

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Congenital Defects Developmental dysplasia of the hip

Abnormality of the proximal femur, acetabulum, or both

Risk factors Female sex, metatarsus adductus, torticollis,

oligohydramnios, first pregnancy, and breech presentation

The hip can present as subluxated, dislocatable, or dislocated

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Congenital Defects Developmental dysplasia of the hip

Manifestations Asymmetry of gluteal or thigh folds Limb length discrepancy Limitation of hip abduction Positive Ortolani sign Positive Barlow test Positive Trendelenburg gait Pain

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Developmental Dysplasia of the Hip

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Congenital Defects Deformities of the foot

Metatarsus adductus Equinovarus deformity

Positional equinovarus Idiopathic congenital equinovarus Tetratologic equinovarus Pes planus

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Osteogenesis Imperfecta “Brittle bone disease” Defect in collagen production

Bone and vessel collagen Sillence classification Results in osteoporosis, bowed and deformed

limbs, short stature, spine curvature, and bluish sclera

Can be evident before birth (in utero fractures)

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Osteogenesis Imperfecta

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Rickets Disorder causing mineralization failure, “soft”

bones, and skeletal deformity Causes

Insufficient vitamin D Insensitivity to vitamin D Renal wasting of vitamin D Inability to absorb calcium or vitamin D in the

gut

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Rickets

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Scoliosis Scoliosis is a rotational curvature of the spine

Nonstructural The curvature is from a cause other than the spine

Structural Spine curvature associated with vertebral rotation Skeletal abnormalities, neuromuscular disease, trauma

extraspinal contractures, bone infections of the vertebrae, metabolic bone disorders, joint disease, and tumors

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Scoliosis

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Osteomyelitis Osteomyelitis in children frequently begins as

a blood abscess in the metaphysis of the bone The abscess ruptures under the periosteum

and spreads along the bone shaft or into the bone marrow Sequestra

Sections of dead bone due to periosteal separation Involucrum

Periosteal new bone

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Osteomyelitis

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Juvenile Rheumatoid Arthritis Childhood form of rheumatoid arthritis The basic pathophysiology of JRA is the same

as the adult form One difference is the mode of onset

Arthritis in fewer than five joints Arthritis in more than five joints Systemic disease

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Juvenile Rheumatoid Arthritis Differences in JRA and adult RA

Large joints are affected Subluxation and ankylosis of the cervical spine Joint pain is not as severe Positive antinuclear antibody test Chronic uveitis Low detection of rheumatoid factor Limited subcutaneous rheumatoid nodules

Common in the heart, lungs, eyes, and other organs

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Osteochondrosis Avascular diseases of the bone Legg-Calvé-Perthes disease

Interrupted blood supply to the femoral head Self-limiting disease Deformation due to ischemia is permanent

Osgood-Schlatter disease Tendinitis of the anterior patellar tendon and

osteochondrosis of the tubercle of the tibia

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Legg-Calvé-Perthes Disease

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Cerebral Palsy A static disorder of muscle tone and balance

caused by an ischemic insult to the brain Perinatal disorder Disease patterns

Hemiplegia, diplegia, quadriplegia

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Muscular Dystrophies Group of disorders that cause degeneration of

skeletal muscle fibers The muscular dystrophies cause progressive,

symmetric weakness and wasting of skeletal muscle groups

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Duchenne Muscular Dystrophy Most common of the muscular dystrophies X-linked recessive inheritance

Deletion of a segment of DNA or a single gene defect on the short arm of the X-chromosome

Duchenne muscular dystrophy gene Encodes for the dystrophin protein Dystrophin mediates the anchorage of the actin

cytoskeleton of the skeletal muscle fiber to the basement membrane

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Duchenne Muscular Dystrophy Manifestations of the disorder begin to appear

by approximately 3 years of age Slow motor development Progressive weakness Muscle wasting Sitting and standing are delayed The child is clumsy, falls frequently, and has

difficulty climbing stairs

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Muscular Dystrophy

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Muscular Dystrophies Becker muscular dystrophy Fascioscapulohumeral muscular dystrophy Scapuloperoneal muscular dystrophy Limb girdle muscular dystrophy

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Bone and Muscle Tumors Nonossifying fibroma Simple bone cysts Aneurysmal bone cysts Osteoid osteoma Fibrous dysplasia Osteosarcoma Ewing sarcoma Rhabdomyosarcoma

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Nonaccidental Trauma “Corner” metaphyseal fractures

Long bone fractures caused by a twisting force Transverse tibial fractures are the most common Associated with child abuse, but osteogenesis

imperfecta must be ruled out

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Nonaccidental Trauma