Chapter 58 - Musculoskeletal Developmental & Metabolic

• as long bones grow in length, the deeper layers of cartilage cells in the growth plate multiply and enlarge, pushing the articular cartilage farther away from the metaphysis and diaphysis of the bone
• mature/enlarged cartilage cells at the metaphyseal plate become inactive and are replaced by bone cells
• bone diameter increases via oppositional growth
• in oppositional growth, concentric rings are added to the outer bone surface accompanied by resorption of bone on the inner surface
• the separation of the epiphyseal growth plate (i.e., as a result of trauma) ruptures the blood vessels that nourish the epiphysis (causes cessation of growth and shortened extremity length)
• sensitivities of the growth plate:

  • nutritional/metabolic changes
  • scurvy
  • rickets
  • after puberty, becomes increasingly less responsive to hormones
  • generally, bone growth ends by age 20 as epiphyseal plate closes
• scurvy impairs the formation of organic matrix in bone causing slowing of growth
• rickets impairs calcification of newly formed bone
• osteogenesis imperfecta is a hereditary disease characterized by defective synthesis of type I collagen
• osteogenesis imperfecta is a spectrum of disorders that results in extreme skeletal fragility with thin, poorly developed bones prone to fractures
• the most serious defects occur with type II osteogenesis imperfecta, where may infants are stillborn or die during infancy due to multiple intrauterine fractures, bowing, and shortening of extremities
• type I OI = postnatal fractures, bone sclera

  • autosomal dominant
  • normal stature, skeletal fragility, hearing impairment, joint laxity, blue sclera
• type II OI = perinatal, lethal

  • autosomal recessive
  • death in utero or in days after birth
  • skeletal deformity with excessive fragility, multiple fractures, blue sclera
• type III OI = progressive deformity

  • autosomal dominant (75), autosomal recessive (25%)
  • growth retardation, multiple fractures, progressive kyphoscoliosis, hearing impairment, blue sclera at birth
• type IV OI = postnatal fractures, normal sclera

  • autosomal dominant
  • moderate skeletal fragility, short stature
• OI is a genetic disorder of connective tissues caused by an abnormality in the synthesis or processing of type I collages
• OI is also called brittle bone disease and is characterized by an increased susceptibility to bone fractures and decreased bone density
• the most common form of OI is caused by mutations in the two collages type I genes
• 85% of OI is caused by pathogenic variants in genes encoding type I collagen (COL:A1/COL:A2)
• a mild OI phenotype stop mutations usually leading to reduced collagen amount
• severe OI phenotype missense mutations mainly provoke structural alterations in the collagen protein
• DDH is an abnormality in hip development that leads to a wide spectrum of hip problems in infants and children
• DDH abnormalities range from weak joints to dislocations
• the primary concern of DDH is damage to the acetabulum and to the head of the femur
• DDH has a necessity for early treatment as therapy works best if begun before 6 months of age
• general treatment for DDH involves reduction of dislocation and immobilization of the legs in an adducted position
• clubfoot/talipes is a congenital deformity of the foot that can affect one or both feet and is the most common pediatric orthopedic condition
• in clubfoot/talipes, the plantar is flexed and inverted (accounts for 95% of cases)
• when treatment for clubfoot/talipes is initiated during the first few weeks of life, a nonoperative procedure may be effective
• serial manipulations and casting are used gently to correct each component of the deformity in clubfoot/talipes
• surgery may be required for severe clubfoot/talipes deformities or when nonoperative treatment methods are unsuccessful
• scoliosis is a lateral deviation of the spinal column that may or may not include rotation or deformity of the vertebrae
• postural scoliosis is a small curve that corrects with bending
• structural scoliosis is a fixed deformity that does not correct with bending
• congenital scoliosis is caused by disturbances in vertebral development during the 6th to 8th week of embryonic development
• neuromuscular scoliosis develops from neuropathic or myopathic diseases
• idiopathic scoliosis is a structural spinal curvature for which no cause has been established
• signs and symptoms of scoliosis:

  • uneven shoulders
  • uneven waist
  • one side of the rib cage jutted forward
  • a prominence on one side of the back when bending forward
• severe scoliosis can be disabling and can cause the spine to twist as well as curve side to side (can affect the rib cage, causing back pain, difficulty breathing, and even heart damage)
• there are 3 proven ways to manage scoliosis: observation, bracing, and surgery