AAOS Comprehensive Orthopaedic Review

Section 7 - Spine

Chapter 66. Adult Spinal Deformity

I. Epidemiology and Overview

A. Definition—Adult spinal deformity (ASD) is defined as a lateral spinal curve >10° in a skeletally mature person.

 

B. Prevalence

 

1. As the average American life span increases, the prevalence of ASD increases. Currently, 1.4% to 12% of the population has a curve >10°.

 

2. Males and females are affected equally.

 

3. Mean age is 60 years.

 

4. Up to 90% of patients have symptoms related to stenosis.

 

C. Disability

 

1. Back and leg pain is a common symptom, reported by almost 61% of patients with advanced degenerative scoliosis.

 

2. Radiculopathy and neurogenic claudication due to nerve root compression is the most common symptom.

 

3. Stenosis is most commonly located on the concavity of the curve.

 

D. Progression

 

1. The average curve progression is 1.0° per year for thoracic curves >50°, 0.5° per year for thoracolumbar curves, and 0.24° per year for lumbar curves.

 

2. Progression is related to curve location; thoracic curves progress more rapidly than lumbar curves, followed by thoracolumbar and double major curves.

 

3. Loss of normal sagittal balance (lumbar lordosis/thoracic kyphosis) is common.

 

4. Contributing factors to loss of sagittal balance include osteoporosis, preexisting scoliosis, iatrogenic instability, and degenerative disk disease.

 

5. Progression more commonly results when intercrestal line is below L4-5 and preexisting rotational changes exist.



II. Classification

A. Two types of adult spinal deformity are currently recognized.

 

1. Idiopathic (residual)—This type represents the natural history of untreated adolescent idiopathic scoliosis after skeletal maturity.

 

2. De novo (adult degenerative scoliosis)—This type results from progressive degenerative changes in the lumbar spine.

 

a. Degenerative (

Figure 1)

 

b. Iatrogenic

 

c. Paralytic

 

d. Posttraumatic

 

[Figure 1. Radiographs of the spine of a 50-year-old woman with degenerative scoliosis and spinal stenosis who was treated with lumbar laminectomy, radical facetectomies, instrumentation with correction of scoliosis, and spinal fusion. A, Preoperative PA view of the lumbar spine. B, Postoperative PA weight-bearing radiograph of the same patient after decompression and fusion.]

B. Curve patterns in de novo ASD

 

1. De novo ASD lacks classic curve patterns.

 

2. De novo ASD usually involves fewer vertebral segments and lacks structural vertebral deformity.

 

3. The curve patterns are usually confined to the lumbar spine, with smaller curve magnitude than seen in idiopathic (residual) ASD.

 

C. Scoliosis Research Society classification

 

1. A new classification system has recently been proposed by the Scoliosis Research Society to categorize scoliosis patients based on curve type, sagittal modifiers, lumbar degenerative modifiers, and global balance modifiers.

 

2. The purpose is to provide uniformity of classification, treatment, and decision making, which would help to facilitate an evidence-based approach to ASD.



III. Patient Evaluation

A. History

 

1. Unlike the classic pattern of neurogenic claudication, patients with scoliosis and stenosis do not obtain relief with sitting or forward flexion.

 

2. Back pain is common (40% to 90%) and more severe and recurrent than in the general population.

 

3. Pain is common in advanced cases and results from stenosis and symptomatic degenerative disks coupled with underlying deformity.

 

B. Physical examination

 

1. A three-dimensional assessment of the entire spine to evaluate kyphosis, lordosis, curve magnitude, deformity, flexibility, and presence of pelvic obliquity is necessary.

 

2. Complete and thorough neurologic examination often reveals deficits.

 

3. Evaluation of body habitus and nutritional status is also important for successful patient management.

 

C. Imaging

 

1. Radiographs

 

a. AP and lateral 36-inch-cassette views

 

i. These radiographs are used to visualize the entire spine, iliac crests, and clavicles (

Figure 2).

 

ii. Measurements should include Cobb angles to assess magnitude of all curves, C7 plumb line to assess for sagittal imbalance, and center

 

[Figure 2. Preoperative PA (A) and lateral (B) weight-bearing radiographs of an adult patient with scoliosis who was treated with staged anterior and posterior fusion with posterior fixation to the pelvis using iliac screw fixation. Postoperative PA (C) and lateral (D) weight-bearing radiographs of the same patient.]

[

Figure 3. Illustrations of a center sacral plumb line (A) and a C7 sagittal plumb line (C7PL) (B).]

   sacral vertical line (Figure 3, A) to identify coronal malalignment.

 

iii. A C7 plumb line is crucial to help guide the surgeon as to the amount of global correction needed (Figure 3, B).

 

iv. It is also important to identify levels of asymmetric collapse.

 

b. Bending views—These radiographs are important for assessing curve flexibility and the possibility of correction with surgical intervention.

 

2. MRI is used to identify central canal stenosis, facet hypertrophy, pedicular enlargement, and foraminal encroachment, as well as disk degeneration.

 

3. CT myelography is often as useful as MRI because rotational deformity and bony anatomy are better visualized on CT.

 

4. Dual-energy x-ray absorptiometry (DEXA) scan may be helpful with preoperative planning.



IV. Nonsurgical Management

A. Overview—Nonsurgical management is the mainstay of treatment in patients in whom surgery is contraindicated (patients with cardiopulmonary limitations, advanced osteopenia, lack of physical or mental conditioning and preparation).

 

B. Treatment regimens

 

1. Core strengthening programs—These include low-impact exercise such as walking, swimming, cycling, and selected weight lifting.

 

2. Medications

 

a. Nonsteroidal anti-inflammatory drugs, non-narcotic analgesia

 

b. Other medications include tricyclic antidepressants, which may be helpful when sleep disturbance is an issue.

 

3. Corticosteroid injections or selective nerve root blocks often can be both diagnostic (to validate foraminal compression) and therapeutic.

 

4. Bracing, coupled with continued exercise, may slow progression and increase comfort.



V. Surgical Management

A. Overview

 

1. Surgical indications include persistent pain (back or radicular) that has failed nonsurgical efforts, increasing deformity, cardiopulmonary decline, unacceptable cosmesis (increasing), and risk of further progression.

 

2. Complications are most effectively minimized by careful patient selection. The patient's age, physical conditioning, and overall health status must be considered.

 

3. Achievement of spinal balance, relief of pain, and a solid arthrodesis should remain the primary goals of surgery.

 

4. The amount of overall correction is directly proportional to the coronal and sagittal balance obtained (

Figure 4).

 

5. Correction of these deformities often necessitates combined anterior and posterior surgeries, either staged or performed on the same day. Combined surgeries can result in longer surgeries, higher complication rates, and more overall medical stress to the patient. Careful preoperative planning for the approach, correction of deformity via osteotomies, and medical optimization are critical.

 

B. Thoracic curves

 

1. Curves limited to the thoracic spine are usually approached posteriorly; exceptions are curves that are extremely rigid, which require an anterior release.

 

[Figure 4. PA (A and C) and lateral (B and D) weight-bearing long-cassette radiographs of a woman with a major spinal deformity before (A and B) and after (C and D) surgical correction.]

2. Only the thoracic deformity should be corrected. Extending the correction to the lumbar vertebrae will compromise motion of the lumbar spine.

 

3. The arthrodesis construct should start high (T2 or T3), and ligaments at more cephalad levels should be spared.

 

C. Isolated thoracolumbar and lumbar curves

 

1. Surgical fixation in the thoracolumbar spine should include decompression as indicated, instrumentation and arthrodesis of the deformity, and correction of the curve as possible.

 

2. These curves are often corrected with an anterior and a posterior approach, but a solely posterior approach may be sufficient.

 

D. Deformity with two or more structural curves

 

1. Multiple curves can often be corrected posteriorly.

 

2. Distally, fusion in this scenario is often to L3 or L4 unless they are also involved in the curve, in which case L5 or S1 should be the distal level of fusion.

 

3. Proximally, the arthrodesis should include the main curve and should extend cephalad to a neutral and horizontal vertebra.

 

E. Extending fusion to S1 (versus L5)

 

1. Extending fusion to S1 is a highly controversial concept.

 

2. Key considerations are any instability of the L5-S1 segment to include spondylolisthesis, or previous laminectomy.

 

3. Fusing to the sacrum

 

a. Disadvantages—Increases pseudarthrosis rate, surgical time, reoperation rate, and rate of sacral insufficiency fractures; also alters gait postoperatively.

 

b. Advantages—Theoretically, L5-S1 fusion increases the stability of a long fusion construct.

 

c. When fusing to the sacrum, anterior column support becomes more important and is most efficiently gained through an anterior approach, allowing for anterior release and better deformity correction.

 

d. Stopping the fusion at L5 may result in painful disk pathology below the fusion in future years.

 

e. Patients with normal sacral inclination and normal C7 plumb line have the lowest incidence of subsequent L5-S1 disk degeneration.

 

F. Sacropelvic fusion

 

1. Sacropelvic fusion is achieved through placement of iliac screws or bolts.

 

2. This approach should be strongly considered if the sacrum is included in a fusion involving more than three levels.

 

G. Indications for anterior interbody fusion

 

1. Anterior fusion is necessary to provide anterior column support when L5-S1 is included in the arthrodesis.

 

2. This may also be achieved through a posterior approach with interbody stabilization.

 

3. An anterior approach, release, and arthrodesis is also helpful when it is necessary to restore sagittal and coronal balance.

 

4. Anterior releases are useful for very stiff curves and when rotatory subluxation or listhesis exists.

 

H. Osteotomies

 

1. Osteotomies are sometimes required to regain sagittal balance in severely angulated deformities.

 

2. A tremendous amount of correction (30° or more) can be gained through different types of osteotomies such as pedicle subtraction or Smith-Petersen techniques.

 

3. These are often larger operations with higher complication rates and more blood loss, and they require greater technical finesse.

 

4. Intraoperative neuromonitoring is recommended to avoid iatrogenic neurologic injury.



VI. Outcomes

A. Most surgical patients obtain significant pain relief, and most of those patients report that they would undergo the same procedure again for the same benefit.

 

B. Complications

 

1. Pseudarthrosis (5% to 25%)

 

2. Infection (0.5% to 8%)

 

3. Neurologic compromise (0.5% to 5%)

 

4. Pulmonary embolism (1% to 20%)



Top Testing Facts

1. ASD is defined as a rotatory and lateral spinal curve >10° in a skeletally mature person.

 

2. From 1.4% to 12% of the population has a curve greater than 10°.

 

3. Back and leg pain are common symptoms in patients with ASD.

 

4. Unlike the classic pattern of neurogenic claudication, patients with scoliosis and stenosis do not obtain relief with sitting or forward flexion.

 

5. Curve progression is likely, especially in patients with thoracic curves or when preexisting rotation is seen on radiographs.

 

6. AP and lateral long-cassette views should be obtained for complete evaluation. Measurements should include Cobb angles to assess magnitude of all curves, C7 plumb line to assess for sagittal imbalance, and center sacral vertical line to identify coronal malalignment.

 

7. CT myelography is most useful for assessing stenosis and bony anatomy, as rotation makes interpretation of MRI scans difficult.

 

8. Nonsurgical management is the first treatment of choice and remains the mainstay of treatment in those patients in whom surgery is contraindicated.

 

9. Correction of these deformities often necessitates combined anterior and posterior surgeries, either staged or performed on the same day. Combined surgeries can result in longer surgeries, higher complication rates, and more overall medical stress to the patient. Careful preoperative planning for the approach, correction of deformity via osteotomies, and medical optimization are critical.

 

10. Achievement of spinal balance, relief of pain, and a solid arthrodesis are the primary goals of surgery.



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