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Introduction
  • Definition
    • genetic disorder of childhood caused by the presence of an extra chromosome 21
  • Epidemiology
    • incidence
      • most common chromosomal abnormality in the United States
      • 1:700 live births
    • risk factors
      • advanced maternal age. 1 in 250 if mother > 35 yo, 1 in 5000 if < 30 yo
  • Genetics
    • maternal duplication of chromosome 21, yielding a trisomy 21
    • chromosome 21 codes for Type VI Collagen (COL6A1, COL6A2)
      • critical component of skeletal muscle extracellular matrix
      • dysfunction may contribute to generalized joint laxity
  • Associated conditions
    • orthopaedic manifestations
      • generalized ligamentous laxity and hypotonia
      • short stature
      • C1-2 instability  
      • Occipitocervical Instability 
      • delayed motor milestones (walk at 2-3 years of age)
      • hip subluxation and dislocation
      • patellofemoral instability and dislocation  
      • scoliosis & spondylolisthesis
      • pes planus
      • metatarsus primus varus
      • SCFE  
    • medical conditions and comorbidities
      • mental retardation
      • cardiac disease (50%)
      • endocrine disorders (hypothyroidism)
      • premature aging
      • duodenal atresia
      • hypothyroidism
      • Alzheimer's disease
Presentation
  • Symptoms
    • determining degree of symptoms can be difficult 
  • Physical exam
    • HEENT
      • flattened facies
      • upward slanting eyes
      • epicanthal folds
    • upper extremity
      • single palmar crease (simian crease)
      • ligamentous laxity
    • spine
      • scoliosis
    • neuro
      • mental retardation of varying degrees
      • hearing loss
Spine Conditions
  • Atlantoaxial Instability 
    • epidemiology
      •  instability is present in 17.5%
    • presentation
      • may be subtle
      • manifests as a loss or change in gait or bowel/bladder symptoms
    • radiographs  
      • may obtain flexion-extension cervical spine radiographs (indications vary, routine screening radiographs likely not needed)
      • flexion-extension films are needed to confirm stability prior to intubation
      • atlantodens interval (ADI) of <5mm is normal
      • In general, 5-10mm of motion can be considered normal in this population
    • treatment
      • nonoperative
        • routine follow up with neurologic evaluation and repeat imaging
          • indications
            • for ADI 5-10, no neurologic findings, and imaging with >14mm space available for the cord.
      • operative
        • C1-2 posterior spinal fusion 
          • general indications
            • ADI >5mm and symptomatic/myelopathic or ADI >10mm
            • <14mm space available for the cord
          • complications
            • reported complication rate up to 50%
      • sports participation
        • asymptomatic patients with instability should avoid contact sports, diving, and gymnastic
  • Occipitocervical Instability 
    • imaging
      • Powers ratio
        • used to diagnosis occipitocervical instability  
    • treatment
      • observation with limitation of contact sports activity
        • indications
          • vast majority of patients
      • posterior occipitocervical fusion
        • indications
          • progressive neurologic deficits and myelopathy
  • Lumbar Spondylolithesis
    • present in 6% of patients with Down's Syndrome
  • Scoliosis
    • treatment
      • bracing for Curves 25-30 degrees
      • spinal Fusion for curves >50 degrees
    • complications
      • complication rate with surgical treatment likely greater than idiopathic scoliosis
Knee Conditions
  • Patellofemoral instability  
    • radiographs
      • lower extremity to evaluate for genu valgum
      • sunrise or Merchant view to evaluate degree of subluxation or dislocation
    • treatment
      • nonoperative
        • observation only
          • indications
            •  in skeletally mature patient with no pain
        • patellar stabilizing brace
          • indicated if symptomatic
      • operative
        • lateral release, medial reefing, semitendiniosus tenodesis, or tibial tubercle osteotomy
          • indications
            •  symptomatic patients
            • osteotomy for skeletal mature patients
Hip Conditions
  • Hip instability
    • introduction
      • may be subluxation of dislocation
      • caused by ligamentous laxity and muscle hypotonia
      • occurs between 2-10 years of age
      • occurs in 5% of patients
    • treatment
      • nonoperative
        • abduction bracing
          • indications
            •  younger child without bony changes or dislocation
      • operative
        • capsulorrhaphy and pelvic and femoral varus osteotomies
          • indications
            • symptomatic older children
          • surgery associated with high complication rate
  • Slipped capital femoral epiphysis  
    • introduction
      • evaluate for concomitant hypothyroidism
    • radiographs
      • AP and Frog Pelvis 
    • treatment
      • operative
        • pinning of affected and contralateral hip
Foot Conditions
  • Pes Planus and Planovalgus
    • introduction
      • seen in 50% of patients
    • treatment
      • orthotics 
        • indications
          • if symptomatic
      • surgery correction
        • indications
          • if refractory symptoms
  • Metatarsus primus varus
  • Hallux valgus
    • seen in 25% of patients
 

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