Musculoskeletal Disorders

Musculoskeletal Disorders


Developmental dysplasia of the hip (DDH) is an abnormal development or dislocation of the hip joint present from birth.

DDH can be unilateral or bilateral. It affects the left hip more often (67%) than the right. This abnormality occurs in three degrees of severity:

  • dislocatable — hip positioned normally but manipulation can cause dislocation

  • subluxatable — femoral head rides on edge of acetabulum

  • dislocated — femoral head totally outside the acetabulum.


Unknown, but genetic factors may play a role.

Risk Factors

  • Breech delivery (malposition in utero; DDH is 10 times more common with breech delivery than after cephalic delivery)

  • Elevated maternal relaxin

  • Large neonates and twins (more common)


Muscular dystrophy is a group of congenital disorders characterized by progressive symmetric wasting of skeletal muscles without neural or sensory defects. Paradoxically, some wasted muscles tend to enlarge (pseudohypertrophy) because connective tissue and fat replace muscle tissue, giving a false impression of increased muscle mass. The prognosis varies with the form of disease. The four main types of muscular dystrophy include:

  • Duchenne’s or pseudohypertrophic (50% of all cases) — strikes during early childhood, is usually fatal during the second decade of life, and affects 13 to 33 per 100,000 persons, mostly males

  • Becker’s or benign pseudohypertrophic (milder form of Duchenne’s) — becomes apparent between ages 5 and 15, is usually fatal by age 50, and affects 1 to 3 per 100,000 persons, mostly males

  • Facioscapulohumeral (Landouzy-Dejerine) and limb-girdle — usually manifests in second to fourth decades of life, doesn’t shorten life expectancy, and affects both sexes equally.


Genetic Mechanisms, Typically Causing an Enzymatic or Metabolic Defect

  • Duchenne’s or Becker’s muscular dystrophy — X-linked recessive disorders; mapped to the Xp21 locus for the muscle protein dystrophin, which is essential for maintaining muscle cell membrane; muscle cells deteriorate or die without it

  • Limb-girdle muscular dystrophy — autosomal recessive disorder

  • Facioscapulohumeral muscular dystrophy — autosomal dominant disorder


Osteomyelitis is a bone infection characterized by progressive inflammatory destruction after the formation of new bone. It commonly results from a combination of local trauma — usually trivial but causing a hematoma — and an acute infection originating elsewhere in the body. Although osteomyelitis usually remains localized, it can spread through the bone to the marrow, cortex, and periosteum.

Osteomyelitis is usually classified as acute if symptoms have been present for less than 2 weeks, subacute between 2 weeks and 3 months, or chronic if greater than 3 months (Chiappini et al., 2016).

Acute osteomyelitis is usually a blood-borne disease and most commonly affects rapidly growing children, with an estimated incidence of 8 cases per 100,000 children/year and a male:female ratio of 2:1. The long bones, such as the femur, are the most frequently involved and the lower extremities are more affected than the upper extremities (Yeo & Ramachandran, 2014). Although rare, with chronic osteomyelitis, drainage of the sinus tracts may be necessary and widespread lesions may be present. Possible consequences may include amputation of an arm or leg when resistant chronic osteomyelitis causes severe, unrelenting pain and decreased function due to weakened bone cortex.


  • Minor traumatic injury

  • Acute infection originating elsewhere in the body

  • Staphylococcus aureus (most common)

  • Streptococcus pyogenes

  • Pneumococcus species

  • Pseudomonas aeruginosa

  • Escherichia coli

  • Proteus vulgaris

  • Pasteurella multocida (part of normal mouth flora in cats and dogs)


Primary malignant bone tumors (also called sarcomas of the bone and bone cancer) are rare, and while constituting only 1% of new cancer diagnoses, it accounts for 2% of cancer deaths (Zhang et al., 2016). The incidence is approximately 8 cases per million/year (Aggerholm-Pedersen et al., 2014). Most bone tumors are secondary, caused by seeding from a primary site.



Suggested Mechanisms

  • Rapid bone growth — Children and young adults with primary bone tumors are much taller than average.

  • Heredity

  • Trauma

  • Excessive radiotherapy


Scoliosis is a lateral curvature of the thoracic, lumbar, or thoracolumbar spine. The curve may be convex to the right (more common in thoracic curves) or to the left (more common in lumbar curves). Rotation of the vertebral column around its axis may cause rib cage deformity. Scoliosis may be associated with kyphosis (humpback) and lordosis (swayback).



  • Poor posture

  • Uneven leg length


  • Congenital — wedge vertebrae, fused ribs or vertebrae, and hemivertebrae

  • Paralytic or musculoskeletal — asymmetric paralysis of trunk muscles due to polio, cerebral palsy, or muscular dystrophy

  • Idiopathic — most common; appears in a previously straight spine during the growing years; may be transmitted as an autosomal dominant or multifactorial trait