Updated: 12/12/2016

Down Syndrome

Topic
Review Topic
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Questions
3
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Evidence
6
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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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(SAE07PE.84) The parents of a 10-year-old boy with Down syndrome are seeking sports clearance for participation in the high jump at the Special Olympics. He is asymptomatic, and the neurologic examination is normal. The hips and patellae are clinically stable. Radiographs of the cervical spine in flexion and extension show a maximum atlanto-dens interval (ADI) of 6 mm. Based on these findings, what recommendation should be made? Review Topic

QID: 6144
1

Clearance for all sports activities

19%

(26/137)

2

Avoidance of contact sports, high jump, and diving

74%

(102/137)

3

Application of a hard cervical collar during sports events

0%

(0/137)

4

Application of a halo vest

1%

(1/137)

5

Posterior atlantoaxial arthrodesis

0%

(0/137)

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