McCance 45

• Musculoskeletal alterations in children can be congenital, hereditary, or acquired.

Musculoskeletal Development in Children

Bone Formation

• Bone formation begins at approximately the sixth week of gestation.
• It involves delivering bone cell precursors to formation sites and their aggregation at ossification centers.
• Flatbones (cranium, facial bones, clavicles, jawbone parts) form via intramembranous bone formation from the mesenchyme.
• Mesenchyme vascularization leads to immature bone cells maturing into osteoblasts, forming ossification centers and creating solid bone or osteoid.
• Endochondral bone formation is the development of new bone from cartilage.
• Mesenchymal tissue forms a cartilage anlage that defines the bone shape around 6 weeks' gestation.
• Blood vessel invasion brings osteoprogenitor cells, leading to primary calcification centers by 8 weeks.
• The perichondrium, a dense connective tissue layer, develops osteoblasts, forming a periosteal collar around the cartilage model.
• Cartilage within the periosteal collar degenerates, while capillaries deliver osteoblast and osteoclast precursors.
• Endochondral bone formation progresses from the primary ossification center toward the developing bone ends.
• Secondary ossification centers lay down bone at the cartilage model's ends by the end of gestation.
• Ossification spreads until all cartilage is replaced by bone, leaving articular cartilage and the physeal plate.
• The physeal plate can form and calcify cartilage and deposit bone until skeletal maturity, approximately one year after sexual maturity.

Bone Growth

• Long bones grow in length at the physeal plate via endochondral ossification until adulthood.
• Cartilage cells at the epiphyseal side multiply and enlarge while cells on the metaphyseal side are destroyed and replaced by bone.
• Compact bone is thickest where stress is maximal, typically in the middle of the shaft.
• The distal physis in the femur contributes 80% of the overall length, whereas the proximal physis at the hip contributes only 20%.
• The distal femur has an undulating pattern that increases its resistance to sheer force.
• The distal radius is a flat, smooth physis that is far more resistant to traumatic injury.
• Bone diameter increases through new bone deposition on the periosteal surface and resorption on the endosteal surface.
• Endosteal resorption increases the diameter of the medullary cavity.
• Growth hormone, peptide regulatory factors, cell interactions, ECM, nutrition, health, and hormones all affect epiphyseal plate development and growth.

Skeletal Development

• The axial skeleton's shape changes with growth which includes the spine.
• A newborn's spine is concave anteriorly (kyphosed) but the cervical spine arches (becomes lordotic) as head control develops in the first 3 months.
• The normal lordotic curve of the lower (lumbar) spine develops with sitting.
• The appendicular skeleton (extremities) grows faster than the axial skeleton during childhood.
• 50% of spinal growth is complete by age 1, and over 70% by age 8.
• In newborns, the proximal femur is rotated forward up to 40 degrees, and the tibia is rotated inward.
• Femur alignment neutralizes by 12, while tibial rotation neutralizes at 8 years of age.
• Bowlegs (genu varum) peak at 30 months, and knock knees (genu valgum) maximize by 5 to 6 years.
• Pathologic causes of genu varum include Blount disease, rickets, skeletal dysplasias, traumatic injury, and musculoskeletal infection.
• Genu valgum may persist in children with skeletal dysplasia, benign musculoskeletal tumors, osteogenesis imperfecta, traumatic injury, or infection.

Muscle Growth

• Muscle tissue in fetuses contains a large amount of water and much intercellular matrix.
• After birth, water and intercellular matrix reduce as muscle fibers enlarge by accumulating cytoplasm.
• The number of muscle nuclei increases between birth and maturity by 14 times in boys and 10 times in girls.
• Muscle fibers reach their maximal size in girls at approximately 10 years of age and in boys by 14 years. Growth in length occurs at the ends of muscles, with an increase in nuclei.
• Muscle fibers increase in diameter as fibrils become more numerous.
• Separation of muscle attachments due to skeletal growth is a potent stimulus.
• Muscle length is a consequence of its intended range of movement, and tendon formation results from muscle pull on connective tissue.
• Muscle fails to grow properly if the normal opponents are paralyzed, potentially causing joint contracture.
• Muscle growth during adolescence is a major factor in weight gain.
• Infants have approximately 25% of their total body weight in muscle, compared to 40% in adults.
• Infants' respiratory and facial muscles are well-developed at birth.
• The weight of skeletal muscles can be increased by exercise throughout life.

Musculoskeletal Alterations in Children

Congenital Defects

Syndactyly

• Syndactyly, or webbing of fingers, is the most common congenital defect of the upper extremity
• Simple webbing involves soft tissue only, and is surgically released at 6 months to 1 year of age.
• Complex syndactyly involves fusion of bones and nails, and surgeries are ideally completed before the child enters school.
• Vestigial tabs, an extra digit, are best removed during the immediate neonatal period.
• Anomalies on the radial aspect of the arm are associated with abnormalities of blood, heart, or kidneys.

Developmental Dysplasia of the Hip

• Developmental dysplasia of the hip (DDH) is an abnormality in the development of the proximal femur, acetabulum, or both.
• The incidence of true dislocation is 1 in 1000 live births. Some degree of instability is present in approximately 10 per 1000 live births.
• 60% of cases affect the left hip, and bilateral DDH occurs 20% of the time.
• Risk factors include family history, female gender, metatarsus adductus, torticollis, oligohydramnios, first pregnancy, and breech presentation.
• Maternal hormones that reportedly increase joint laxity may affect DDH.
• DDH also is more common in whites and those cultures that swaddle infants with the hips in extension and adduction.
• The hip can be described as subluxated, dislocated, and acetabular dysplasia.
• The acetabulum is often dysplastic, typically shallow or sloping rather than cup-shaped.
• By approximately 10 weeks’ gestation, the femur, acetabulum, and hip joint capsule are well developed.
• Most hip dysplasia develops within the second and third trimesters and is often the result of positioning factors.
• In untreated DDH, the acetabulum becomes shallow, and soft tissues shorten around the proximal femur.
• Subluxation leads to early osteoarthritis (OA), and it is estimated that at least 60% of all OA of the hip is related to DDH.
• The dislocated hip has no contact between the femoral head and the acetabulum and an apparent limb length inequity and hip muscle weakness occur.
• Clinical manifestations include asymmetry of gluteal or thigh folds, limb length discrepancy, limited hip abduction, and a positive Barlow or Ortolani maneuver.
• Clinical examination is the most important diagnostic tool in the newborn period, along with real-time ultrasound.
• After age 6 months, radiographs are used when the ossific nucleus of the femoral head appears.
• Treatment involves using a Pavlik harness in children less than 4 to 6 months old, and a "closed" reduction followed by spica casting for up to 3 months in children less than 12 months of age.
• Surgical intervention is required after 12 months. Early intervention before age 1 is critical for a good outcome.

Deformities of the Foot

• Congenital foot deformity is found in approximately 4% of all newborns, and metatarsus adductus accounts for 75% of these deformities
• Metatarsus adductus is a forefoot adduction deformity associated with a normal, plantigrade hindfoot.
• Metatarsus adductus is associated with DDH in 20% of cases.
• Metatarsus adductus is classified by flexibility and degree of deformity, ascertained by the heel bisection line.
• Serial casts during the first 6 months are suggested for moderate to severe deformities and those deformities that appear less flexible.
• By 6 years of age, 87% of children correct spontaneously, and 95% by 15 years of age.
• Clubfoot describes a range of foot deformities in which the foot turns inward and downward and is technically called equinovarus.
• The clubfoot deformity can be positional, idiopathic, or teratologic equinovarus.
• Positional equinovarus deformity lends itself to rapid correction by stretching exercises or serial casts.
• The idiopathic varieties are treated by weekly cast correction, followed by Achilles tenotomy and abduction bracing.
• Teratologic equinovarus deformities more often require surgical correction or muscle-balancing procedures, or both; however, initial serial casting may achieve correction albeit with a higher risk of recurrence.

Positional Equinovarus

• Positional equinovarus is a flexible deformity without deep creases.
• The Achilles tendon is still flexible, and the foot can be passively brought to a plantigrade position.
• Conservative therapy corrects this foot without the need for surgical intervention or lengthy bracing.

Idiopathic Congenital Equinovarus

• The etiology of idiopathic equinovarus (clubfoot) is unknown.
• Muscle biopsies reveal a decreased number of muscle fibers and/or abnormal fiber histology.
• Historically, these deformities were treated by posteromedial release, but techniques developed by Ignacio Ponseti are commonly used since 1998.
• Ponseti casting implements toe-to-groin casts changed weekly for 6 weeks.
• The need for PMR in idiopathic clubfoot has decreased.
• Noncompliance with braces leads to increased recurrence and need for additional casting or surgery.

Teratologic Equinovarus

• The most common cause of teratologic equinovarus is either neuromuscular (such as spina bifida) or syndromic (such as arthrogryposis or osteochondrodysplasia).
• The teratologic clubfoot, unlike the idiopathic type, more often fails to be corrected with Ponseti casting and may require operative intervention.

Pes Planus Deformity

• Pes planus (flatfoot) commonly raises parental concern.
• Flexible flatfoot deformity appears to be familial, with occasional association of generalized ligamentous laxity.
• Significant ankle valgus, tarsal coalition, and skewfoot must be accurately differentiated from flexible pes planus.
• Surgical or orthotic treatment of asymptomatic flexible pes planus is unnecessary.
• In rigid flat feet, a computed tomographic (CT) scan often will reveal a coalition.

Abnormal Density or Modeling of the Skeleton

Osteogenesis Imperfecta

• Osteogenesis imperfecta (OI) (brittle bone disease) is a collagen-related bone dysplasia first described in 1840.
• Collagen is the main component of bone and blood vessels.
• The Sillence classification describes the most common types of OI.
• Errors in collagen synthesis affect bone, cartilage, eye tissue, skin, and the vascular system.
• Individuals with OI may have increased serum thyroxine levels, suggesting hyperthyroidism.
• Classic clinical manifestations are fractures, osteoporosis, bony deformation, triangular facies, possible vascular weakness, possible blue sclerae, and poor dentition.
• Types I and IV are inherited as autosomal dominant traits and vary in age of onset from birth to adulthood.
• Type IV has a white sclerae, is the least deforming, and is often confused with nonaccidental trauma (child abuse).
• Quantitative analysis of cultured skin fibroblast collagen shows a decreased quantity of collagen in 95% of individuals.
• For Type II OI, careful positioning and handling of the newborn prevent fractures.
• Multicenter study shows that bisphosphonate therapy shows results in type III OI, with marked improvements of bone density.
• Genetic counseling for affected families should aim at primary prevention.

Rickets

• Rickets is a disorder in which growing bone fails to become mineralized, resulting in ‘soft’ bones and skeletal deformity.
• It is the result of either vitamin D insufficiency/insensitivity, wasting of vitamin D by the kidney, or inability to absorb vitamin D and calcium in the gut.
• The most common form is X-linked hypophosphatemic rickets in industrialized nations.
• Severe metabolic rickets leads to short stature, bowing of the limbs, and broad, irregular growth plates.
• Children with rickets are often listless and irritable, have hypotonia and muscle weakness.
• The cartilaginous attachments of the ribs become prominent, and growth is restricted.
• Children may benefit from guided growth techniques for persistent deformity.

Scoliosis

• Scoliosis is a rotational curvature of the spine most obvious in the anteroposterior plane, and classified either as nonstructural or structural.
• Nonstructural scoliosis results from a variety of causes, such as posture, leg length discrepancy, or pain; structural scoliosis is curvature of the spine associated with vertebral rotation.
• Structural scoliosis can be caused by congenital skeletal abnormalities, neuromuscular diseases, trauma, extraspinal contractures, and more.
• Idiopathic scoliosis is classified as infantile, juvenile, or adolescent, depending on the child’s age at the time of onset.
• Adolescent scoliosis in its milder forms occurs equally in boys and girls; however, girls are 10 times more likely than boys to develop curves greater than 30 degrees.
• The earliest pathologic changes occur in the soft tissues in the muscles, ligaments, and other soft tissues become shortened on the concave side of the curve.
• Curves increase most rapidly during periods of rapid skeletal growth, but the spine is biomechanically unstable in curves greater than 50 degrees and the curve usually progresses even after the cessation of growth.
• Structural scoliosis manifests as asymmetry of hip height, asymmetry of shoulder height, shoulder and scapular prominence, and rib prominence. Brace treatment is indicated for children with curves of 25 to 40 degrees.
• If surgery is indicated, it is better performed during the adolescent years.

Bone Infection: Osteomyelitis

• Osteomyelitis is an infection of the bone occurring twice as often in males as females and affects infants/children of any age but occurs most often between 3 and 12 years.
• Bacteria enter the bone through the bloodstream and lodge in the medullary cavity, or may lodge at the end of the venous loops beneath the epiphyseal plate.
• In newborns, osteomyelitis is caused primarily by Staphylococcus aureus, while S. aureus is the responsible microorganism in most older children.
• Factors that predispose an individual to the development of osteomyelitis include impetigo, furunculosis, infected lesions of varicella, infection of the vertebrae, burns, cerebral abscesses, immunization with BCG vaccine, and others.
• Osteomyelitis usually begins as a bloody abscess in the metaphysis of the bone, and rarely spreads down the medullary cavity of the bone.
• Abscesses may cause a rupture into the joint cavity, causing secondary septic arthritis.
• Multiple sites of osteomyelitis are also common in children younger than 2 years of age.
• In children older than 2 years, the epiphyseal plate prevents the spread of a metaphyseal abscess into the epiphysis.
• An elevated CRP is quickly responsive to appropriate treatment.
• CRP (C-reactive protein) is more responsive to appropriate treatment.
• Positive blood cultures, aspiration of soft tissue or bone helps identify a causative microorganism.
• Treatment includes IV antibiotics, or combinations of IV and oral antibiotics for 6 weeks, drainage, and immobilization.

Rheumatologic Disorders

• The rheumatic diseases are a group of diverse conditions commonly having inflammation of connective tissues, including JIA, SLE, dermatomyositis, and progressive systemic sclerosis.
• Many children with pauciarticular arthritis who are seronegative for ANA will resolve their symptoms over time. With systemic onset, JIA may progress to true adult RA.
• The emergence of new treatments including use of biologics have improved the prognosis for children with JIA.
• The classic findings for JIA are enlarged joints, warm to the touch, pain, and systemic inflammation.

Avascular Diseases of the Bone: Osteochondrosis

• The avascular diseases of the bone, collectively termed osteochondroses, are caused by insufficient blood supply to growing bones.
• The osteochondroses involve areas of significant tensile or compressing stress that undergo partial osseous necrosis, progressive bony weakness, and then microfracture.
• Most are associated with trauma and overuse and improve with rest. Reparative correction by revascularization is the rule.

Legg-Calvé-Perthes Disease

• Legg-Calvé-Perthes (LCP) disease is a self-limited disease of the hip that is produced by interruption of the blood supply to the femoral head; the ossification center first becomes necrotic and collapses and then is gradually remodeled by live bone.
• LCP is common and usually occurs in children between 3 and 10 years of age; it affects boys more than girls. Bilateral cases are temporally separated.
• Constitutional factors play a role in LCP; skeletal maturation is delayed, children are shorter, and familial occurrence is 30% to 40%.
• Acute synovitis and increased hydrostatic pressure in the hip joint may compress blood vessels that supply the femoral head.
• The fourth or healed stage consists of remodeling. Recent studies show that hips with no involvement to the femoral lateral head do better than those with involvement.
• Injury or trauma precedes the clinical manifestations in approximately one-third of the time, and onset of symptoms is insidious unless trauma aggravates the disease process.
• Treatments include antiinflammatory medications, crutches, and limited activity.

Osgood-Schlatter Disease

• Osgood-Schlatter consists of tendinitis of the anterior patellar tendon and osteochondrosis of the tubercle of the tibia.
• Osgood-Schlatter disease occurs most often in preadolescents and adolescents who participate in sports.
• The severity of the lesion varies from mild tendinitis to a complete separation of the anterior extension of the tibial epiphysis.
• The child experiences pain and swelling in the region of the patellar tendon and tibial tubercle.
• Treatment includes rest, gradual resumption of activity, a cast, or a brace.

Cerebral Palsy

• CP is a general term that refers to nonprogressive disorders of movement and posture resulting from injury or malformation of the developing central nervous system.

Neuromuscular Disorders

• Neuromuscular disorders are a group of inherited disorders causing progressive muscle fiber loss, leading to weakness that affects children resulting in lifelong complications.
• Increasing genetic testing is used for diagnosis and classification for disorders, using clinical history, physical examination, and family history to narrow the differential diagnosis for testing directly with a genetic test.

Duchenne Muscular Dystrophy

• DMD is the most common of the muscular dystrophies, affecting approximately 1 in 3500.
• DMD is caused by deletion of one or more exons of the DMD gene on the X chromosome.
• Lack of dystrophin results in poorly anchored fibers that are torn apart under stress of contraction. Free calcium then enters the muscle cells, causing cell death and fiber necrosis.
• Duchenne muscular dystrophy is usually identified in children at approximately 3 to 4 years of age when the parents notice gait abnormalities, including difficulty getting up from the ground.
• Complications such as compromised pulmonary function and kyphoscoliosis are delayed, however cognitive dysfunction is a common aspect of Duchenne.
• Diagnosis of DMDis confirmed by genetic testing, which is informative in 95% of cases. Maintaining function in unaffected muscle groups for as long as possible is the primary goal of treatment.

Spinal Muscular Atrophy

• Spinal muscular atrophy (SMA) is a common autosomal recessive disorder characterized by degeneration of motor neurons in the spinal cord; caused by a mutation in the SMN1 gene.
• Children have progressive weakness, loss of motor skills, tongue fasciculation, and a bell-shaped chest.
• Genetic replacement and gene modification therapies are rapidly evolving.

Facioscapulohumeral Muscular Dystrophy

• FSHD is a mild form of progressive autosomal dominant muscular dystrophy with onset varies from early childhood to adulthood.
• Clinical manifestations begin with weakness and atrophy of facial and shoulder girdle (scapulohumeral) muscles.
• Complete treatment includes supportive physiotherapy and plastic ankle-foot orthoses.

Musculoskeletal Tumors in Children

• Bone tumors are uncommon childhood tumors and comprise less than 5% of all childhood malignancies.
• Most pediatric tumors are benign, most commonly nonossifying fibroma, osteochondroma, simple bone cyst, aneurysmal bone cyst, osteoid osteoma, and fibrous dysplasia.

Benign Bone Tumors

• Nonossifying fibromas constitute about 50% of benign bone tumors and are usually asymptomatic.
• Osteochondroma results in a bony protuberance of bone growing near the growth plate from a solitary lesion or hereditary multiple exostoses (HMEs).
• A spinal MRI is helpful to see if the core is at risk of injury in children diagnosed with HME.
• Simple bone cysts are cystic lesions of the central region of the metaphyseal area that are usually asymptomatic until pathologic fracture.
• Aneurysmal bone cysts are eccentric, metaphyseal lesions in an older population, must be differentiated from telangiectatic osteosarcoma.
• When pain is too extreme to be controlled, resection of the “nidus,” or central portion, of the lesion is uniformly successful.
• Fibrous dysplasia causes thinning of the bone with one bone in 1/13 or multiple bones affected.

Malignant Bone Tumors

• Osteosarcoma is typically treated with multiagent chemotherapy and surgery that has improved and increased the patient survival rate.
• Osteosarcoma disseminates through the bloodstream, usually to the lung.
• Osteosarcoma is typically found between the ages of 10-18.
• Ewing sarcoma is a malignant tumor of bone and soft tissue that is the second most common and most lethal malignant bone tumor, and is more common in males.
• Bone scan, chest roentgenogram, chest CT scan, and bone marrow biopsy also are used to detect metastases.