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Introduction
  • A rigid thoracic hyperkyphosis defined by > 45 degrees
  • Epidemiology
    • incidence
      • 1% to 8%  
      • most common type of structural kyphosis in adolescents
    • demographics
      • M:F ratio between 2:1 and 7:1
    • location
      • usually in thoracic spine
      • less common form occurs in thoracolumbar/lumbar region (see below)
  • Pathoanatomy
    • exact cause unknown 
    • currently theory suggests that the kyphosis and vertebral wedging are caused by a developmental error in collagen aggregation which results in an abnormal end plate
  • Genetics
    • autosomal dominant inheritance pattern now accepted
  • Associated conditions
    • orthopaedic manifestations
      • Lumbar hyperlordosis
      • spondylolysis (30-50%)
      • scoliosis (33%)
    • nonorthopaedic manifestations
      • possible pulmonary issues in curves exceeding 100 degrees
  • Prognosis
    • back pain in adults that very rarely limits daily activities (mild curves with a mean of 71 degrees)
    • curves >75 degrees are likely to cause severe thoracic pain
Classification
  • Thoracic Scheuermann's Kyphosis
    • most common form
  • Thoracolumbar/lumbar Scheuermann's Kyphosis
    • less common
    • associated with increased back pain
    • more irregular end-plates noted on radiographs 
    • no vertebral wedging involved
Presentation
  • Symptoms
    • may complain of thoracic or lumbar pain
    • cosmetic concerns
  • Physical exam  
    • increased kyphosis which has a sharper angulation when bending forwards
      • normal thoracic kyphosis is between 20 degrees and 45 degrees 
    • may have a compensatory hyperlordosis of the cervical and/or lumbar spine
    • tight hamstrings are common
    • neurological deficits rare but need to evaluate neuro status
Imaging
  • Radiographs
    • recommended
      • AP and lateral spine
    • findings
      • anterior wedging across three consecutive vertebrae 
      • disc narrowing
      • endplate irregularities
      • Schmorl's nodes (herniation of disc into vertebral endplate)
      • scoliosis  
      • compensatory hyperlordosis
      • important to look for spondylolysis on lumbar films
    • hyperextension lateral xrays
      • can help differentiate from postural kyphosis
      • Scheuermann's kyphosis usually relatively inflexible on bending xray
  • CT scan
    • usually not needed
  • MRI
    • controversial as to if indicated prior to surgery or not to look for associated disc herniation, epidural cyst, cord abnormalities, and spinal stenosis 
    • will show vertebral wedging, dehydrated discs, and Schmorl's nodes (herniation of disc into vertebral endplate)
Treatment
  • Nonoperative
    • stretching and observation
      • indications
        • kyphosis < 60° and asymptomatic (or pain is mild)
          • most patients fall in this group and can be treated with observation alone
    • bracing with extension-type orthosis (jewitt type - with high chest pad)
      • indications
        • kyphosis 60°-80° msot effective in those with gorwth remaining
      • outcomes
        • patient compliance is often an issue
        • usually does not lead to correction but can stop progression
  • Operative
    • PSF with dual rod instrumentation ± Smith-Petersen osteotomy ± anterior release and interbody fusion
      • indications
        • kyphosis > 75 degrees 
        • neurologic deficit
        • spinal cord compression
        • severe pain in adults
      • Smith-Petersen osteotomy
        • best for long sweeping, global kyphosis
        • 10° sagittal plane correction per level
      • anterior release
        • uncommon now from improved pedicle screw posterior constructs 
        • perhaps indicated in larger curves that are more rigid in nature
      • outcomes
        • studies show 60-90% improvement of pain with surgery (no correlation with amount of correction)
Surgical Techniques
  • PSF with dual rod instrumentation
    • approach
      • posterior midline to thoracic spine
    • arthrodesis
      • current recommendation is to include entire kyphotic Cobb angle and stop distally to include theStable Sagittal Vertebrae
    • fixation technique
      • usually a combination of pedicle screws and hooks
        • intra canal hooks may be dangerous at apex of curve as they can potentially compress spinal cord
      • do not always have to instrument at apex
    • correction technique
      • Cantelever - usally two rods placed in top anchors then brought down to bottom pedicle screws
      • Compression accross psoterior anchors
      • posterior spine shortening technique of Ponte
        • indicated in stiff curves where correction is needed
        • done by removing spinous processes at apex, ligamentum flavum, and performing  superior and inferior facet resection
      • goal is to obtain correction to final kyphosis from 40-50°
      • in situ bending usally not helpful
  • Anterior release and fusion
    • thorascopic anterior discectomy may morbidity of thoracotomy, but usually not needed
Complications
  • Neurologic complications
    • higher than idiopathic scoliosis corrective surgeries
    • must monitor with motor and somatosensory evoked potentials
  • Distal Junctional kyphosis
    • occurs in 20-30% of patient
    • avoid by
      • making proper selection of fusion levels
      • avoid overcorrection (correction should not exceed 50% of original curve)
 

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