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Updated: Jun 17 2021

Spondyloepiphyseal Dysplasia (SED)

Images with cervical instability.jpg spine.jpg
  • summary
    • Spondyloepiphyseal Dysplasia is a rare congenital disorder most commonly caused by a COL2A1 mutation leading to abnormal Type II collagen synthesis. Patients present with dwarfism, flattened faces, scoliosis, and in some cases gait instability as a result of cervical myelopathy. 
    • Diagnosis is made radiographically with presence of irregular ossification at multiple epiphysesflattened vertebral bodies, and thoracic kyphoscoliosis. Flexion and extension radiographs of cervical spine should be performed to evaluate for atlantoaxial instability.
    • Treatment involves a multidisciplinary approach to improve and maintain function. Spinal fusion is indicated in patients with atlantoaxial instability, cervical myelopathy, or progressive scoliosis.
  • Epidemiology
    • Incidence
      • rare
  • Etiology
    • Pathophysiology
      • caused by abnormal synthesis of Type II collagen
      • primarily affects the vertebrae and epiphysis of bone
    • Genetics
      • inheritance pattern
        • autosomal dominant (SED congenita)
        • X linked recessive (SED tarda)
        • random mutation (50% of cases)
      • mutations
        • COL2A1 on chromosome 12
    • Associated conditions
      • atlantoaxial instability
      • frequent cause of myelopathy in spondyloepiphyseal dysplasia congenita
      • nephrotic syndrome (SED tarda)
  • Classification
    • Two forms of SED exist
      • SED congenita
        • autosomal dominant
        • more severe than SED tarda
      • SED tarda
        • X-linked recessive
        • clinicallly less severe and does not have the lower extremity angular deformities that are present in the congenita form
  • Presentation
    • Symptoms
      • cervical myelopathy
        • due to atlantoaxial instability
      • respiratory difficulty
        • due to respiratory insufficiency secondary to thoracic dysplasia
      • problems with vision
        • due to myopia or retinal detachment
      • hip pain
        • due to coxa varus
      • decreased walking distance
        • due to poor muscular endurance and skeletal deformities
    • Physical exam
      • inspection
        • short stature
        • flatened facies
        • kyphoscoliosis
        • lumbar lordosis
        • coxa vara
        • genu valgum
      • motion
        • decreased ROM of hips
        • waddling gait
  • Imaging
    • Radiographs
      • recommended views
        • AP, lateral, open mouth views of cervical spine
        • AP, lateral views of thoracolumbar spine
        • AP, lateral views of hips
      • alternative views
        • flexion-extension views of cervical, thoracolumbar spine
      • findings
        • cervical spine
          • upper cervical spine instability
          • odontoid hypoplasia or os odontoideum
        • thoracolumbar spine
          • platyspondyly (flattened vertebral bodies) is evident in lumbar spine
          • incomplete fusion of spinal ossification centers
          • end plate irregularities and narrowed intervertebral disk spaces
          • kyphoscoliosis
          • excessive lumbar lordosis
        • hips
          • horizontal acetabular roofs and delayed ossification of the pubis
          • wide Y cartilage
          • coxa vara of varying severity
          • delayed ossification of the femoral head
    • MRI
      • indications
        • cervical instability
        • symptoms of myelopathy
      • findings
        • spinal cord signal changes
        • delayed ossification centers
  • Differential
    • Achondroplasia
    • Diastrophic dysplasia
    • Multiple Epiphyseal Dysplasia (MED) 
  • Treatment
    • Nonoperative
      • multidisciplinary rehabilitation
        • indications
          • all patients to improve and maintain function
        • technique
          • should integrate
            • physiotherapy
              • monitor for weakness, increasing spine curvature, worsening hip pain
            • occupational therapist
            • ophthalmologist
              • obtain yearly eye examination
            • pulmonologist
              • monitor for declining lung function
            • orthopaedic surgeon
              • possible bracing for mild scoliosis
    • Operative
      • posterior atlantoaxial fusion
        • indications
          • atlantoaxial instability measuring 8 mm or more
          • myelopathy
        • techniques
          • posterior instrumentation
      • posterior thoracolumbar instrumentation
        • indications
          • spinal scoliosis curvatures >50 degrees
        • techniques
          • distraction spinal rods (younger aged patients)
          • posterior instrumented spinal fusion (older aged patients)
      • valgus intertrochanteric osteotomy
        • indications
          • coxa vara angle <100 degrees
          • progressive coxa vara
          • symptomatic hip arthritis
        • techniques
          • valgus + extension osteotomy may help to decrease an associated hip flexion deformity
          • reconstructive measures may be indicated in patients with subluxation, hinge abduction, or osteoarthritis.
          • open reduction and fixation of proximal femur and acetabulum to treat hip dislocations.
  • Complications
    • Cervical spine instability
    • Spinal deformity
      • including scoliosis, kyphosis, lordosis
    • Ocular abnormalities
    • Hip deformities
    • Degenerative joint disease
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