Updated: 12/2/2018

Adult Spinal Deformity

Review Topic
https://upload.orthobullets.com/topic/2041/images/progression small large.jpg
https://upload.orthobullets.com/topic/2041/images/coronal balance.jpg
https://upload.orthobullets.com/topic/2041/images/sagittal balance.jpg
  • A deformity of the spine in either the coronal or sagittal plane
    • coronal plane imbalance 
      • defined as lateral deviation of the normal vertical line of the spine > 10 degrees
    • sagittal plane imbalance
      • defined as radiographic sagittal imbalance of >5cm
  • Epidemiology
    • demographics
      • mean age is 60 years
      • males and females equally affected
    • location
      • idiopathic scoliosis is more common in the thoracic spine
      • degenerative scoliosis occurs more commonly in the lumbar spine.
  • Pathoanatomy
    • degenerative scoliosis results from the asymmetric degeneration of disc space and/or facet joints in the spine.  
    • may occur in the coronal plane (scoliosis) or the sagittal plane (kyphosis/lordosis)
    • factors contributing to loss of sagittal plane balance
      • osteoporosis   
      • preexisting scoliosis
      • iatrogenic instability
      • degenerative disc disease
  • Prognosis
    • worse prognosis with
      • if symptoms progress to the side of curve convexity
      • sagittal plane imbalance
        • sagittal plane balance is the most reliable predictor of clinical symptoms in adults with spinal deformity   
    • progression
      • depends on curve type
        • thoracic >  lumbar > thoracolumbar > double major
        • right thoracic curves (1 degree per year)
        • right lumbar curves (0.5 degree per year)
        • thoracolumbar curves (0.25 degree per year)
      • depends on curve magnitude
        • curves <30 deg rarely progress
        • curves >50 deg commonly progress
      • additional risk factors for progression
        • increased risk when intercrestal line is below L4-5 
        • preexisting rotational changes exist
  • Coronal deformity can be broken down into
    • idiopathic (residual) ASD
      • the result of untreated adolescent idiopathic scoliosis in the adult
    • degenerative (de novo)  ASD
      • defined as a progressive deformity in the adult caused by
        • degenerative changes
        • iatrogenic
        • paralytic
        • posttraumatic
Difference between Idiopathic (residual) and Degenerative (de novo) ASD
  Idiopathic (residual) Degenerative (de novo)
Curve pattern Follows classic curve patterns 
Lack classic curve patterns
Vertebral segments Involves more vertebral segments
Involves fewer vertebral segments
Curve location Thoracic spine  Confined to lumbar spine
Curve magnitude Larger curves Smaller curve magnitude
  • Symptoms
    • low back pain (40-90%)
      • commonest symptom is low back pain
      • caused by spondylosis, micro/macro instability, and discogenic pain
      • more severe and recurrent than general population
    • neurogenic claudication
      • pain in lower extremities and buttocks 
        • unlike classic claudication, patients with scoliosis + stenosis do not obtain relief with sitting / forward flexion
      • caused by spinal stenosis
        • stenosis is located on the concave side of the curve
    • radicular leg pain and weakness
      • caused by foraminal and lateral recess stenosis
      • worse in concavity of the deformity where there is vertebral body rotation and translation
  • Physical exam
    • deformity with thoracic prominence seen with forward bending
    • muscle weakness
  • Radiographs
    • recommended views
      • full length long 36-inch cassette standing scoliosis xrays in coronal (AP radiograph) and sagittal plane (lateral radiograph), with right and left bending films 
        • bending films help assess curve flexibility and possibility of correction with surgical intervention
    • measurements
      • AP radiograph
        • Cobb angle
        • coronal balance  
          • using C7 plumb line (C7PL) and center sacral vertical line (CSVL)
      • lateral radiograph
        • sagittal balance  
          • using C7 plumb line  (C7PL)
        • pelvic incidence 
          • pelvic incidence = sacral slope + pelvic tilt
  • CT scan
    • will help identify bony deformity such as facet arthrosis
  • CT myelogram
    • most useful for assessing stenosis and bony anatomy as rotation makes interpretation of MRI difficult
    • better appreciation of bony anatomy and rotational deformity than MRI
  • MRI
    • indicated when lower extremity pain is present
    •  can identify 
      • central canal stenosis
      • facet hypertrophy
      • pedicular enlargement
      • foraminal encroachment
      • disc degeneration
  • DEXA scan
    • important to determine bone density for surgical planning
  • Nonoperative
    • observation with nonoperative modalities 
      • indications
        • coronal curves < 30 degree rarely progress
      • modalities
        • oral medications
          • NSAIDS
          • tricyclic antidepressants help with sleep disturbance
        • physical therapy 
          • includes core strengthening (walking, cycling, swimming, selected weight lifting)
        • corticosteroid injections and nerve root blocks
          • diagnostic and therapeutic
        • bracing
          • may slow progression and increase comfort
  • Operative
    • surgical curve correction with instrumented fusion
      • general indications
        • curve > 50 degrees of the following type
        • sagittal imbalance
        • curve progression
        • intractable back pain or radicular pain that has failed nonsurgical efforts
        • cosmesis (controversial)
        • cardiopulmonary decline
          • thoracic curves >60deg affect pulmonary function tests
          • thoracic curves >90deg affect mortality
      • technique
        • posterior only curve correction and instrumented fusion
          • indications
            • thoracic curves > 50 degrees
            • most double structural curves > 50 degrees
            • selecting technique is patient and surgeon specific
        • combined anterior/posterior curve correction with instrumented fusion
          • indications
            • isolated thoracolumbar
            • isolated lumbar curves
            • extremely rigid curves requiring anterior release
  • General
    • goals of surgery
      • restore spinal balance
        • sagittal plane balance is the most reliable predictor of clinical symptoms postoperatively   
        • can be measured by C7 plumb line (C7 sagittal vertical axis) 
          • correction of sagittal plane deformity requires intense preoperative planning
      • relieve pain
      • obtain solid fusion
  • Selecting Proximal and Distal fusion level
    • proximal extension
      • extend to a neutral and horizontal vertebra above the main curve
    • extend fusion to L5
      • indications
        • only indicated if no pathology at L5/S1
          • patients with normal C7 plumb line and normal sacral inclination have lowest risk of future L5-S1 disc degeneration
      • outcomes
        • high failure rate if instrumentation does not extend to the sacrum if pathology at L5/S1
    • extend fusion to sacrum (S1)
      • indications
        • extend to sacrum if any pathology at L5-S1 including
          • L5-S1 spondylolisthesis
          • L5-S1 spondylolysis
          • L5-S1 facet arthrosis
          • prior laminectomy
        • technique
          • may requires concomitant anterior release and anterior column support (through anterior approach) for better deformity correction
        • outcomes
          • advantages
            • increased stability of long fusion construct
            • constructs less likely to fail if instrumentation extends to sacrum
          • disadvantages
            • increased risk of pseudoarthrosis
            • increased surgical time
            • increased reoperation rate
            • increased risk of sacral insufficiency fractures
            • altered gait postoperatively
    • extend fusion to ilium (sacropelvic fusion)
      • indications
        • consider this if sacrum is included in fusion involving >3 levels
      • technique
        • using iliac screws or bolts
      • outcomes
        • advantage
          • increased stability of long fusion construct
          • increases success of lumbosacral fusion
        • disadvantage
          • prominent hardware
  • Osteotomies
    • overview
      • useful to regain sagittal balance in severe angulation deformities
      • 30deg or more correction can be obtained through Smith-Petersen or pedicle subtraction osteotomies
      • intraoperative neuromonitoring preferred
    • Smith-Petersen osteotomy (SPO) 
      • indications
        • mild-moderate sagittal imbalance 
        • requiring correction of up to 10deg (per level of osteotomy)
      • prerequisites
        • no anterior fusion at the level of osteotomy
        • adequate correction requires adequate disc height and mobility (correction is at the level of the disc)
          • more correction in the lumbar spine (greater disc height and mobility)
          • less correction in the thoracic spine (lesser disc height and mobility)
    • pedicle subtraction osteotomy (PSO) 
      • indications
        • severe sagittal imbalance >12cm
        • requiring correction of 30-35deg in the lumbar spine, and 25deg in the thoracic spine
        • where anterior fusion is present (correction is at the level of the vertebral body and not at the disc)
    • vertebral column resection 
      • indications
        • severe sagittal imbalance (provides more correction than PSO)
        • requiring correction of up to 45deg 
        • rigid angular thoracic spine kyphosis, such as associated with tumor, fracture or infection
        • severe rigid scoliosis
        • congenital kyphosis
        • hemivertebrae resection in thoracic/lumbar spines
  • Anterior Procedures
    • indications
      • large curves >70deg
      • rigid curves (no flexibility on side bending films)
      • isolated lumbar or thoracolumbar curves
      • anterior interbody fusion at L5/S1 when fusing to sacrum 
    • technique
      • anterior release and fusion usually combined with posterior instrumentation and fusion
        • staged or same day
    • outcomes
      • disadvantages
        • longer surgeries (if performed on the same day)
        • higher complication rates
        • more medically stressful
      • advantage
        • increases stability of L5-S1 long fusion constructs
        • helps restore and maintain sagittal and coronal balance
Complications (surgical)
  • Overall 
    • overall complication rate ~13.5%
    • 10% major complications which often irreversibly affect long term health of patient 
    • complication rate is significantly higher when osteotomies, revision procedures, and combined anterior/posterior approaches
    • venous thromboembolism is most likely to result in poor clinical outcome following adult spinal deformity surgery  
  • Pseudoarthrosis
    • incidence (~5-25%)
    • most common surgical technique resulting in pseudoarthrosis is posterior only fusion (15%)
    • commonest locations
      • L5-S1 
      • thoracolumbar junction
    • risks
      • age>55
      • kyphosis >20 degrees
      • positive sagittal balance >5cm
      • hip arthritis
      • smoking  
      • thoracoabdominal approach 
      • incomplete lumbopelvic fixation
  • Dural tear (~2.9%), 
  • Infection
    • deep wound infection (~1.5%)
    • superficial wound infection (~0.9%)
  • Implant complication (~1.6%)
    • instrumentation failure more likely in bone with lowest ratio of cortical to cancellous bone (sacrum<vertebral bodies<lumbar pedicles<thoracic pedicles) 
  • Neurologic deficits
    • acute neurological deficits (~1.0%)
      • can occur intraoperatively after deformity correction maneuver
      • if identified on neurophysiologic monitoring, should remove instrumentation and consider wake-up test 
    • delayed neurological deficits (~0.5%)
    • acute neurological deficits following PSO (18%) 
      • nerve root injury
      • screw malposition
      • corrective maneuver
  • Epidural hematoma (~0.2%)
  • Pulmonary embolus (~0.2%)
  • Deep venous thrombosis (~0.2%).
  • Deaths (~0.3%)

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Questions (17)
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(OBQ11.25) A 53-year-old woman is seen in the adult spine clinic for long-standing back pain. History reveals she had untreated scoliosis as a child. Her current radiographs are shown in Figures A and B. Due to discomfort with ADLs and progressive pain, surgical intervention is planned. Which of the following factors would increase her risk of nonunion? Review Topic

QID: 3448

An anterior thoracoabdominal approach




Preoperative Cobb angle of 60 degrees




Age greater than 35 years




A posterior midline approach




Positive sagittal balance < 5 cm



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(OBQ09.20) In adult patients with scoliosis, severity of symptoms correlates with which of the following variables? Review Topic

QID: 2833

Coronal imbalance




Sagittal imbalance




Magnitude of coronal Cobb angle




Number of spine levels involved in the deformity




Level of the apex of the curve



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(OBQ12.77) What is the incidence of major complications following adult spinal deformity surgery? Review Topic

QID: 4437

< 1%



















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(OBQ10.221) In patients with adult scoliosis requiring long thoracolumbar fusions, which of the following is the major advantage of extending the fusion to the sacrum as opposed to ending at L5. Review Topic

QID: 3320

Improved function outcomes




Decreased pseudoarthosis rates




Decreased major medical complications




Improved correction and maintenance of sagittal balance




Improved curve correction in the coronal plane



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