Updated: 2/1/2017

Spondyloepiphyseal Dysplasia (SED)

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https://upload.orthobullets.com/topic/4096/images/sed.jpg
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https://upload.orthobullets.com/topic/4096/images/sed spine.jpg
Introduction
  • A form of short-trunk dwarfism caused by a defect in the secondary ossification center (epiphysis) 
  • Epidemiology
    • rare
  • 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
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

References

 

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