Adult idiopathic and degenerative scoliosis

1

Define adult scoliosis and describe the prevalence and incidence of this condition.

Adult scoliosis is a spinal deformity characterized by a Cobb angle in excess of 10° in the coronal plane that is present in a skeletally mature patient. Recent estimates regarding the prevalence of scoliosis in adults range from 2.5% to 25% of the population, and increasing age is associated with higher prevalence rates. Kebaish et al (1) reported a prevalence of 9% in adults aged 40 years and older, and a prevalence as high as 68% in a population of adults aged 60 years and older. According to 2010 US Census data, the incidence of adult scoliosis is 5.9 million adults, based on a conservative prevalence rate of 2.5%, with 1.6 million adults receiving treatment either on an inpatient or outpatient basis.

2

What are the major types of scoliosis identified in adults?

Three types of scoliosis in adults are identified according to the Aebi classification system:

• Type 1: Primary degenerative or de novo scoliosis develops after age 40 in patients with a previously straight spine, as the result of multilevel asymmetric disc and facet joint degeneration. It is the most common type of adult scoliosis and involves the thoracolumbar and lumbar spinal regions.

• Type 2: Progressive idiopathic scoliosis consists mainly of adult patients who developed idiopathic scoliosis during adolescence, which was unrecognized or left untreated. Coronal plane curvatures may involve the thoracic, thoracolumbar, or lumbar spinal regions, and may be associated with spinal degenerative changes.

• Type 3: Secondary adult scoliosis consists of two subtypes:

  • Type 3A deformities result from conditions within the spine such as an adjacent idiopathic, neuromuscular, or congenital curve; a lumbosacral anomaly; or from conditions outside the spine such as pelvic obliquity, leg length inequality, or hip pathology.

  • Type 3B deformities develop as a consequence of metabolic bone disease or osteoporotic fractures.

3

Compare and contrast de novo adult scoliosis and idiopathic scoliosis in adulthood.

See Table 51.1.

4

What are some factors associated with curve progression in patients with adult scoliosis?

Patients with adult scoliosis may experience curve progression. Curve progression occurs in a high percentage of adult patients with degenerative scoliosis. Reported curve progression rates in degenerative scoliosis patients vary from 1° to 6° per year and average 3° per year. Multiple rotatory subluxations, curve magnitude >30°, and a relative lack of osteophyte formation are factors associated with curve progression. In adult idiopathic scoliosis patients, curves in excess of 50° are estimated to progress at a mean rate of slightly less than 1° per year. A relatively small percentage of curves between 30° and 50° progress, and progression of thoracic curves less than 30° is unlikely. Each patient, however, is unique, and one cannot always predict whether lumbar or thoracic curves will progress in adulthood.

5

Outline some key components involved in the evaluation of an adult patient with scoliosis.

• Detailed patient history: Inquire when spinal deformity was first observed. Identify the main reason for seeking medical treatment (pain? neurologic symptoms? impaired function in activities of daily living? increasing deformity? cardiorespiratory symptoms?). If pain is present, describe its location, severity, duration, frequency, exacerbating and relieving factors, and whether pain is related to activity or present at rest.

• Medical history: Have prior diagnostic studies or spine treatments been performed? Are there any associated or general medical problems? Are risk factors for osteoporosis present?

• Medications: Record dose, route, and frequency for each medication

• Allergies

• Review of major organ systems

• Family history: Is there a family history of spinal deformity?

• Social history: Record occupation, history of use of tobacco, alcohol, or narcotics

• Comprehensive physical examination:

  • Inspection. Assess for asymmetry of the neckline, shoulder height, rib cage, waistline, flank, pelvis, and lower extremities. Observe the patient’s gait.

  • Palpation . Palpate the spinous processes and paraspinous region for tenderness, deviation in spinous process alignment, or a palpable step-off.

  • Spinal range of motion . Test spinal flexion-extension, side-bending, and rotation.

  • Neurologic examination. Assess sensory, motor, and reflex function of the upper and lower extremities.

  • Spinal alignment and balance assessment in the coronal plane . Normally the head should be centered over the sacrum and pelvis. A plumb line dropped from C7 should fall through the gluteal crease.

  • Spinal alignment and balance assessment in the sagittal plane . When the patient is observed from the side, assess the four physiologic sagittal curves (cervical and lumbar lordosis, thoracic and sacral kyphosis). When the patient is standing with the hips and knees fully extended, the head should be aligned over the sacrum.

  • Extremity assessment . Assess leg lengths. Assess joint range of motion in the upper and lower extremities.

6

What imaging studies are necessary to comprehensively assess a patient with adult scoliosis?

Standing full-length posteroanterior (PA) and lateral radiographs are required and should permit visualization from the occiput proximally to atleast the level of the femoral heads distally. If neurologic symptoms are present or if surgery is considered, spinal magnetic resonance imaging is obtained. Computed tomography is obtained to assist with surgical planning on a case-by-case basis. Assessment of bone mineral density (BMD) with dual-energy x-ray absorptiometry (DEXA) is performed for patients with risk factors for osteoporosis.

7

Why is it important to visualize the femoral heads on the lateral standing spine radiograph?

There is an interrelationship between the orientation of the distal lumbar spine, sacrum, and the pelvic unit, which influences sagittal alignment of the spine. Three pelvic parameters are measured: pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT). Pelvic incidence (PI) is a fixed anatomic parameter unique to the individual. Sacral slope (SS) and pelvic tilt (PT) are variable parameters. The relationship among the parameters determines the overall alignment of the sacropelvic unit according to the formula PI = PT + SS . Increased pelvic tilt is a compensatory mechanism for a positive shift in sagittal vertical axis (SVA) and should be considered when planning reconstructive spinal surgery for sagittal imbalance.

8

Summarize the basic radiographic parameters that should be assessed in patients with adult scoliosis.

• Coronal plane

  • Magnitude of each curve (Cobb angle)

  • Central Sacral Line

  • C7 plumb line

  • Fractional lumbar curve (if present)

• Sagittal plane

  • Thoracic kyphosis (TK)

  • Thoracolumbar kyphosis (TLK)

  • Lumbar lordosis (LL)

  • Sagittal vertical axis (SVA)

• Pelvic parameters

  • Pelvic incidence (PI)

  • Pelvic tilt (PT)

  • Sacral slope (SS)

• Curve flexibility in the coronal and sagittal planes

  • Comparison of standing and supine radiographs

  • Side-bending radiographs

( Fig. 51.1 A, B)

9

Is coronal or sagittal plane spinal alignment most closely correlated with functional status in patients with adult scoliosis?

Spinal deformity in the coronal plane has not been strongly correlated with patient-reported pain or disability. In contrast, sagittal plane parameters have been highly correlated with adverse health status outcomes. Patients with adult scoliosis involving the lumbar spine generally have coexistent disc degeneration over multiple levels. This results in loss of anterior disc space height, segmental kyphosis, and positive sagittal malalignment. To maximize health-related quality of life following reconstructive surgery for adult scoliosis, ideal sagittal alignment goals have been identified as: sagittal vertical axis (SVA) <50 mm, pelvic tilt (PT) <20°, and pelvic incidence (PI) minus lumbar lordosis (LL) <10°.

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