AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Background

Scoliosis is the presence of 1 or more lateral rotatory curves of the spine in the coronal plane. Although defined as a side-to-side deformity, it is a 3-dimensional (3D) rotational deformity. Many causes of scoliosis are known; however, 80% of them are idiopathic. Idiopathic scoliosis is a diagnosis of exclusion.

Most cases of scoliosis are managed conservatively, but surgery is required in select cases to arrest further progression of the deformity, to correct the curve, and to manage severe pain. Imaging plays a crucial role in confirming the diagnosis, determining the cause, grading the severity of the curve, assessing maturity, identifying patients who need surgery, and assessing postoperative complications.

Pathophysiology

Development and biomechanics of scoliosis

The development of scoliosis can be explained biomechanically on the basis of the Heuter-Volkmann law, which states that pressure on epiphysis retards the rate of growth and that tension increases the rate of growth. Hence, the leading edge of the deformity grows more rapidly than trailing edge, increasing the rate of progression.

In scoliosis, the essential deformity is lordosis, with the spinous process deviated to the concavity of the lateral curve. As the rotation progresses, the load on the epiphysis on the side of body that is more anterior increases, resulting in a lateral deformity. Thus, scoliosis is a deformity of lordosis, rotation, and lateral wedging of the vertebrae.

Types of scoliosis

Scoliosis is broadly divided into 2 types: postural and structural. Idiopathic scoliosis is a type of the structural form.

Postural scoliosis

Postural scoliosis is a flexible deformity due to faulty positioning and is confirmed by spontaneous correction when the patient bends toward the convexity of the curve. No associated rotational deformity or wedging is observed. Although postural scoliosis is transient, it can become fixed and structural if it is habitual and chronic.

Common causes of postural scoliosis are habitual faulty posture, a shortened lower limb, disk prolapse, pain, and hysterical etiologies.

Structural scoliosis

Structural scoliosis is a rigid deformity that cannot be actively corrected by a change of posture.

Structural scoliosis has various causes, as follows:

• Idiopathic causes
• Congenital causes
  • Failure of formation - Wedge vertebra, hemivertebra
  • Failure of segmentation - Fused vertebra, fused ribs, unilateral fused bar
  • Combination of both failures
• Mesodermal causes
  • Neurofibromatosis (NF)
  • Osteogenesis imperfecta
  • Mucopolysaccharidosis
  • Marfan syndrome
• Neuromuscular causes
  • Spinal dysraphism
  • Myelomeningocele
  • Syringomyelia
  • Diastematomyelia
  • Tethered cord
  • Arnold-Chiari malformations
  • Muscular dystrophy
  • Poliomyelitis
  • Friedreich ataxia
  • Cerebral palsy
  • Arthrogryposis multiplex congenita
  • Motor neuron disease
  • Congenital hypotonia
• Radiation therapy
• Skeletal dysplasias
  • Spondyloepiphyseal dysplasia
  • Diastrophic dwarfism
  • Metatrophic dwarfism
  • Chondrodysplasia congenita
• Infections
  • Pyogenic osteomyelitis
  • Tuberculosis
  • Brucellosis
• Tumors
  • Osteoid osteoma
  • Osteoblastoma
  • Meningiomas
  • Neurofibromas
  • Astrocytomas
  • Ependymomas
  • Metastasis
• Miscellaneous causes
  • Congenital heart disease
  • Coarctation of the aorta
  • Cyanotic heart disease
  • Congenital torticollis
  • Ocular torticollis
  • Spondylolisthesis
  • Malignant hyperpyrexia
  • Familial dysautonomia
  • Metabolic bone disease
  • Endocrine bone disease

Idiopathic scoliosis

Idiopathic scoliosis is the most common type of scoliosis, accounting for 80% of cases. It occurs in 3 forms: infantile, juvenile, and adolescent.

The infantile form is seen in patients as old as 3 years, and it is more common in boys than in girls. It usually involves the thoracic region with convexity to the left side. Faulty positioning of the infant in cot is one of the theories of formation. This type is uncommon in America and more common in Europe and Asia. It is associated with skull and pelvic abnormalities. Although infantile scoliosis often spontaneously resolves, some cases can progress, especially in the first 18 months during the growth spurt of infancy.

The juvenile form occurs between 4 and 9 years of age. Most cases involve the dorsolumbar region with convexity to the left side. This type is usually progressive. Some of these cases are either slowly progressing infantile scoliosis that is diagnosed late or adolescent scoliosis that is diagnosed early.

The adolescent form is seen between 10 years of age and maturity. This is the most common type of idiopathic scoliosis, accounting for 80% of all cases. It is more common in female adolescents (95%) than in male adolescents. Most cases involve the thoracic region with convexity to the right side; the apex of the curve commonly at the level of T7 or T8. This form can occur in the lumbar vertebrae, which is commonly concave to the right side. Theoretically, most of these curves originate in juveniles and later manifest in adolescents.

In the simple Dickson classification, idiopathic scoliosis is divided into early-onset ( <5 y) and late-onset (>5 y) types.

The exact etiology of idiopathic scoliosis is not yet known. Many theories of formation have been proffered, implying the disease is likely to be multifactorial. Contributing factors are growth asymmetry, hormonal factors, abnormal equilibrium system in the brainstem, genetic factors, and soft tissue abnormalities.

Autosomal dominant inheritance is proposed, but multifactorial inheritance is most likely. Type I fibers in the erector spinae muscle on the concave side of scoliotic curve may be involved in idiopathic scoliosis. These fibers, which are resistant to fatigue, play an important role in sustained tonic activities, and a decrease in these fibers may be an etiologic factor.

Frequency

United States

The prevalence of idiopathic adolescent scoliosis is approximately 4.5%. The overall prevalence is 3-5%, for curves less than 20° and 0.5% for curves more than 20°. The prevalence of scoliosis more than 25° is 1.5 cases per 1000 population. Scoliosis is most common in tall and heavy people.

International

The prevalence of idiopathic scoliosis requiring treatment is 0.1-0.3%. Adolescent scoliosis is widely distributed all over the world. The prevalence of curves more than 10° is 2.5 cases per 100 population. The prevalence of curves more than 20° is 1 case in 2500.

The prevalence of scoliosis is 11% in first-degree relatives of patients with diagnosed scoliosis, 2.4% in second-degree relatives, and 1.4% in third-degree relatives.

Infantile scoliosis is uncommon in America and more common in Europe and Asia.

Mortality/Morbidity

The mortality rate in patients with scoliosis is twice than that of healthy population. The mean age at death is 45-60 years.

• Scoliosis produces cosmetic deformity, disability, pain, and severe restriction of the patient's capacity to work.
• Cardiovascular compromise occurs in severe scoliosis (curves >60°). One third of patients with curves of 60-100° and one half of those with curves of more than 100° have cardiac complications. Cardiac involvement is more common with thoracic curves than with curves in other locations.
• Respiratory failure, cor pulmonale, restrictive lung disease, and right-sided heart failure are common cardiopulmonary complications. The risk of cardiovascular complications is highest in individuals with early-onset, large-curve scoliosis. The risk is low in late-onset scoliosis, even if the curve is severe.

Race

Infantile scoliosis is uncommon in America and more common in Europe and Asia.

Sex

The overall female-to-male ratio is 1.25:1. With curves of 6-10°, the ratio is almost 1:1, but with curves more than 20°, the ratio is 5.4:1.

• The infantile type is most common in boys, but the adolescent type is more frequent in female adolescents (95 %).
• Progression of the curve is more common in female individuals than in male individuals. The disease progresses in approximately 15.4% of female patients with scoliosis of more than 10°, compared with the general rate of 6.8%.
• The prevalence of scoliosis in daughters of mothers with scoliosis is 15-27%.

Age

• Scoliosis is characterized by progression with age. The rate of progression depends on the cause and the patient's rate of growth, with the incidence of progression of 5-79%. Progression is marked during accelerated growth in infancy and adolescence. Approximately 60% of rapidly growing curves can worsen.
• Progression usually stops when maturity is attained, particularly if the curve is less than 30°. Curves of more than 30° can grow at the rate of 1° per year after maturity.
• The infantile type affects infants and children as old as 3 years. The juvenile type affects children aged 4-9 years. The adolescent type occurs between 10 years and adulthood, and the adult form occurs between ages 20 and 50 years. In the Dickson classification, scoliosis is identified as early onset ( <5 y) or late onset (>5 y).

Anatomy

Anatomy of the spine

A normal spine has a typical curvature of lordosis in the cervical and lumbar regions and kyphosis in the thoracic and sacral region. A straight line can be drawn through the cervicothoracic, thoracolumbar, and lumbosacral junctions.

Development of the spine

The spinal curvature varies in different stages of life. At birth, the spine has a single curve, which is concave anteriorly. In infants, the cervical lordosis is established when they start to keep their head in erect position. The lumbar lordosis develops in the second year, when the child develops the ability to stand erect.

The spine continues to grow mainly by means of the proliferation of the cartilage in the superior and inferior aspects of the primary ossification center in the vertebral body. The annular cartilages develop independent of the primary ossification center and do not contribute to longitudinal growth. This center fuses with the body only after it is completely developed. By puberty, the normal adult curve is established, with the cervical and lumbar lordoses and the thoracic and sacral kyphoses.

Clinical Details

Clinical findings

On clinical evaluation, patients with scoliosis have a lateral bending of the spine that cannot be corrected by a change of posture. On bending forward, the prominence of the posterior ribs on the convex side of curve becomes most obvious. The spine deviates from the midline in all the 3 planes. The displacement is lateral in the frontal plane, with lordosis in the sagittal plane and rotation of the vertebrae about their own axis toward the convex side of the curve.

Idiopathic scoliosis does not produce symptoms such as pain and disability. An asymmetrical spine is the only finding. The ribs and scapula are prominent on 1 side, with a raised shoulder or hip protrusion on the other side. The deformity is most obvious when the curve is high, especially in the thoracic position. In combined thoracolumbar curves, the visible deformity is lessened as a result of balancing of the curves, but shortening of the trunk is visible.

On occasion, the clinical and imaging features are not typical of idiopathic scoliosis. Comprehensive clinical and neurologic examination and imaging are indicated in these atypical cases.

Scoliosis is atypical if the patient is male or has a left-sided thoracic curve, rapid progression of the curve, neurologic deficits, headache, neck ache, backache, and/or foot deformity.

Complications

Pulmonary function can be affected in severe scoliosis. The deformity affects expansion of the lungs, resulting in a restrictive defect apparent on pulmonary function tests. Although dyspnea is not common in children, it can occur in adults, depending on the severity of scoliosis.

Cardiac anomalies can be associated with idiopathic scoliosis. Idiopathic scoliosis is seen in 1-5% of patients with congenital heart disease; the incidence is highest in those with cyanotic heart disease.

See also Mortality/Morbidity above.

Progression

Progression is indicated when the curve grows more than 5° per year. Scoliosis progresses with age at variable rate of 5-79%. The rate depends on the cause and the patient's rate of growth. Progression is marked during accelerated growth in infancy and adolescence, and 60% of rapidly growing curves can worsen.

The vertebrae continue to grow on the convex side and inhibited on the concave side. Curves less than 30 ° do not progress after maturity. Curves of 30-50° progress if they are rotated more than 25°, at the rate of 1° per year. Curves more than 50-75° progress regardless of maturity.

See also Age above.

Other problems to consider

Neuromuscular curve

This is usually a long curve and C shaped.

Neurofibromatosis

NF usually involves a short, sharply angulated curve. The 2 most common types of NF are type I (NF-I) and type II (NF-II). NF-I, or von Recklinghausen disease, is characterized by peripheral neurofibromas, plexiform neurofibromas, café au lait spots, Lisch nodules in the iris, optic-nerve gliomas, bone dysplasias, and scoliosis. NF-II is characterized by bilateral acoustic neuromas, meningiomas, schwannomas, and posterior subcapsular cataracts. The defect in type I is on chromosome 17, and in type II, the defect is on chromosome 22.

Congenital heart disease

Congenital heart disease can be associated with scoliosis (1-5%). Unlike idiopathic scoliosis, scoliosis with this involvement is most common in male individuals and usually convex to the right side (3:1). It is more common and severe with cyanotic heart disease than with acyanotic heart disease. The incidence of congenital heart disease with aortic coarctation is high. The spine and skull can be thick and dense as a result of hypoxia due to cardiac failure.

Scoliosis in the elderly

This is a type of scoliosis seen in men older than 60 years. Scoliosis in the elderly has no particular cause, though it is believed to be secondary to severe degenerative disease. Unlike the curve in idiopathic scoliosis, the curve in elderly scoliosis is short, segmental, and without any lateral wedging or abnormalities of the neural arch.

Management of scoliosis

The management of scoliosis depends on the maturity of the skeleton and on the degree of curvature. With curves of less than 25° in an immature skeleton or less than 30° in a mature skeleton, management is conservative and includes regular follow-up and radiography. Curves less than 25° require management when they are rapidly progressive, especially in preadolescents. With curves of 25-50°, orthotic devices (eg, braces) are used to restore the curvature to acceptable levels and to prevent progression. However, such devices are not used if the patient has respiratory or neurologic compromise. With curves of greater than 50°, fusion is performed if patients present before maturity. Posterior spinal fusion with bone grafting is usually performed, and the spine is stabilized by using internal fixation devices, such as Harrington rods, a Luque system, or a Cotrel-Dubousset system with screws or wires or hooks.

Spontaneous improvement occurs in approximately 3% of patients, especially when the curve is less than 10°.

Aims of surgery are to prevent curve progression, to maintain balance, to reduce pain, to preserve respiratory and neurologic function, to facilitate nursing care, to improve cosmetic appearances (eg, of the large rib bump), to address failure of bracing, and to treat curves of greater than 40-50° in a growing child.

Prognosis

The prognosis depends on the age of the patient, the onset of menarche, the degree of spinal curvature, the number of vertebrae involved, the location of the curve, the rotational deformity, the maturation of the bone (as assessed by using the Risser index), the patient's family history, and the associated anomalies.

Preferred Examination

Clinical examination

Clinical examination should include neurologic examination to assess the deformity. A scoliometer is placed over the spinous process at the apex to measure the angle of trunk rotation (ATR). The measurement is significant if it is more than 5°.

Imaging examination

Radiography is the mainstay in assessment of scoliosis. It is used to confirm the clinical diagnosis of scoliosis, to exclude underlying causes (eg, segmentation abnormalities), to assess the curves and their severity, to monitor progression, to assess skeletal maturity, and to determine a patient's suitability for surgery. This study is also useful in diagnosing postoperative complications and in follow-up.

Bone scans are useful to evaluate cases of painful scoliosis and to identify tumors or infections. They are more sensitive than plain radiography.

CT scanning with sagittal and coronal reconstructions can provide all the information that a plain radiograph provides. With CT, 3D reconstructions are useful in assessing segmentation abnormalities. CT can also be used to assess the true extent of rotation and rib deformities. It plays an important role in evaluating postoperative complications.

The role of MRI is controversial. Although some institutes prefer to perform routine preoperative MRI in all patients, recent studies have shown that such an approach does not provide clinically significant results. MRI is useful for diagnosing associated spinal and neurologic lesions. Small tumors and infections can be localized by using MRI.

Limitations of Techniques

The main limitation of radiography is the radiation dose. The risk of carcinogenesis is increased because of the repeated examinations done to monitor curve progression. This risk can be reduced with the judicious use of radiography and proper protection techniques.

Radiography is less sensitive than bone scanning and MRI because tumors or infections are apparent only after 50% of the bone is destroyed. Radiographs cannot be used to assess abnormalities of the spinal cord.

CT scanning is not routinely indicated, but it is a good method for assessing rotation and segmentation abnormalities. Radiography can provide all of the information needed. MRI is not cost-effective, and it is not a good screening tool because its yield in depicting important clinical abnormalities that change management is minimal.

DIFFERENTIALS

Section 3 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Other Problems to be Considered

Neuromuscular curve
Neurofibromatosis
Congenital heart disease
Scoliosis in the elderly

RADIOGRAPH

Section 4 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Findings

Indications for radiography

Radiography is performed to confirm the diagnosis of scoliosis (which is made on clinical grounds), to exclude underlying bony segmentation abnormalities, to assess the severity of the curve, monitor progression of the curve (which is done by measuring indices), assess skeletal maturity by noting the ossification of the iliac apophysis, evaluate associated cardiac and pulmonary anomalies, and to assess the patient's progress and to evaluate complications during and after surgery.

Preoperative, postoperative, and follow-up imaging is also discussed in Surgical radiographic assessment, below.

Radiographic findings in idiopathic scoliosis

Radiographic findings and assessments in idiopathic scoliosis can be described as listed below.

• Lateral curvature to the spine is present and described in terms of the convex or concave side.
• Four patterns are seen in idiopathic scoliosis: (1) thoracic curve, (2) lumbar curve, (3) thoracolumbar curve on the same side, and (4) thoracic and lumbar curves on opposite sides.
• The number of vertebrae involved in the curve should be assessed.
• In a healthy person, a straight line can be drawn through the cervicothoracic, dorsolumbar, and lumbosacral junctions. The degree of deviation in the cervicothoracic angle from the sacral center is measured.
• Hypokyphosis of less than 20° or lordosis is present. The normal thoracic kyphosis is 20-45°.
• The apical vertebrae show increased height in the anterior aspect of vertebral body and decreased height in the posterior aspect.
• Vertebral bodies and intervertebral disk spaces are wider on the convex side than on the concave side.
• The posterior ribs are pushed posteriorly on the convex side, where they produce a hump. They are positioned anteriorly on the concave side.
• The ribs are closely approximated on the concave side and separated on convex side.
• At the end of the curve, the disk spaces are equal or widened on the concave side. The vertebrae and neural arches are thick on the concave side.
• The spinous process is shifted toward the concave side, and the pedicle and vertebral body are shifted toward the convex side.
• The rotation is marked at the apex of the curve and almost neutral at the end vertebrae. Rotation can be intersegmental (between vertebrae) or intrasegmental (between elements of 1 vertebrae); the latter is uncorrectable.
• The psoas shadow is absent on the concave side of the curve.

Radiographic classification systems

Many classification systems are used to describe the types of scoliotic curves. Classification helps surgeons in deciding appropriate management because the prognosis and treatment of the various curves differ.

Ponseti-Friedman classification

The Ponseti-Friedman classification has 5 types: I is a single major lumbar curve at T11-L3 with an apex at L1-2 (This is the most benign type and affects 23% of patients). II is a single major dorsolumbar curve at T6-7 to L1-2 with an apex at T11-12 (16%). III is combined thoracic and lumbar (37%) with a dorsal curve on the right side at T5-6 or T10-11 and an apex at T7-8 and a lumbar curve on the left side at T10-11 to L3-4 with an apex at L1-2. IV is a single major thoracic curve at T5-6 to T11-12 with an apex at T8-9 (22%). V is cervicothoracic at C7-T1 or T4-5 with an apex at T3.

King-Moe classification

The King-Moe classification has 4 types: I, which is lumbar dominant and S shaped (10%); II, which is thoracic dominant and S shaped (33%); III, which is thoracic where the thoracic and lumbar curves do not cross the midline (33%); and IV, long thoracic or double thoracic with T1 tilted into the upper curve where (the upper curve is structural (10%).

Lenke classification

The Lenke classification has 3 components: (1) type of curve, (2) lumbar modifier, and (3) sagittal thoracic modifier. Type of curves are as follows: I, primary thoracic; II, double thoracic scoliosis; III, double major scoliosis; IV, triple major scoliosis; and V, dorsolumbar-lumbar scoliosis. The lumbar modifier is based on the relationship of the central sacral vertical line to the apex of the lumbar curve and is classified into A, B, and C categories. The sagittal thoracic modifier is the sagittal curve measurement from T5-12; designations are - for less than 10°, N for 10-40°, and + for greater 40°.

Radiographic views

The classic views obtained in the evaluation of scoliosis are listed below.

• Posteroanterior (PA) erect view of the entire spine from cervical to sacral spine and including the iliac crest: This view is ideally obtained with the patient's shoulders outstretched.
• AP recumbent view of entire spine, cervical to sacral
• Lateral view of dorsolumbar spine: The patient's forearm must be kept horizontal by resting it on a stand.
• Lateral profile at the apex of scoliosis to eliminate kyphosis and show the true extent of the scoliosis
• Stagnara image (planed election view) perpendicular to the true coronal plane of the apical vertebra
• Leeds image, a true lateral view 90° perpendicular to the Stagnara view
• Left and right lateral bending views: These are obtained to exclude postural scoliosis. Postural scoliosis disappears when bending toward the side of convexity. These views are also used to assess structural scoliosis, asymmetry and loss of normal mobility of primary curve, and wedging rotation of individual vertebra, and to dynamically assess the postural nature of secondary compensatory curves in the preoperative period and to select fusion levels.
• AP view of the left hand to assess bone age
• Biplanar views with digital enhancement
• Ferguson view perpendicular to the L5-S1 disks to detect anomalies at this junction
• Coned views of focal vertebral anomalies

In routine practice, not all these views are necessary. Full-length frontal and lateral views, as well as right and lateral bending views, are enough.

Common views obtained before surgery are PA and lateral image, which are obtained with long-cassette film to cover the whole spine beginning from the craniocervical junction and including the pelvis to assess the Risser grade; supine, standing, or sitting images if patient is unable to stand; and lateral bending views to assess the extent of compensatory curves.

For subsequent follow-up imaging, the frontal PA view is sufficient, and lateral views are required only if a superimposed kyphotic element is present.

Terminology used to describe scoliosis

The apical vertebra is the vertebra that is displaced and rotated most. Its endplates are least tilted.

The end vertebrae are the most superior and inferior vertebrae in the curve. These bones are least displaced and rotated, with maximal tilting of the endplates toward the concavity of the curve. They are laterally wedged, longer in the convex side and compressed on the concave side.

The neutral vertebra is not rotated on the anteroposterior (AP) image.

The stable vertebra is bisected by the central sacral line.

The primary curve the structural curve, with wedging, angulation, rotation, and an abnormal position. The primary curve is deformed and develops structural changes simultaneously. It is not corrected spontaneously or with mechanical correction. The following characteristics are helpful in identifying the primary curve: (1) The vertebrae are deviated to the convexity of the curve. (2) If 3 curves are present, the middle one is usually the primary curve. (3) If 4 curves are present, the middle 2 are the primary ones. (4) The primary curve may be the greatest curve.

The secondary curve is the nonstructural curve that develops in response to the primary structural curve. The structural changes in this curve occur slowly. It can be corrected spontaneously, and any mechanical correction is retained. The vertebrae are displaced to the concavity of the curve.

The compensatory curves are curves formed to balance the primary curve. If a primary curve is formed in 1 direction, another curve of same magnitude should be formed in the opposite direction to fully compensate for the deformity. For example, if the primary curve is 50°, 1 or 2 compensatory curves may be present and add to equal 50° in the opposite direction.

A decompensated curve is a compensatory curve that does not fully correct the deformity. An example is a 40° compensatory curve for a 50° primary curve results in decompensation.

An overcompensated curve is a compensatory curve that is more than the primary curve. An example is a 60° compensatory curve or a combination of curves adding to 60° that overcompensates for a 50° primary curve.

Indices used to assess scoliosis

The following techniques, measures, and indices are used to assess scoliosis: the Cobb-Webb technique, the Ferguson technique, the Greenspan method, the Nash-Moe technique of measuring vertebral rotation, the Cobb method of assessing vertebral rotation, the Risser index, the observation for ossification of the vertebral ring apophysis, the difference in the rib-vertebral angle, the Perdriolle method, the Lytilt method, and other methods of assessing skeletal maturity.

Cobb-Webb technique

This is the most commonly used technique to measure the severity of scoliosis. The result determines further management and helps in predicting the prognosis.

The superior and inferior end vertebrae of the scoliotic curve are identified by carefully observing the rotation of vertebral bodies and the width of the intervertebral space. The intervertebral space is almost normal, and the vertebrae are in neutral position without substantial rotation in the superior and inferior end vertebra.

Lines are drawn tangential to superior endplate of the superior end vertebra and the inferior endplate of the inferior vertebra. The Cobb-Webb angle is the angle formed at the intersection of these lines or the angle formed at the intersection of the lines perpendicular to these lines. A Cobb angle of at least 10° is essential for diagnosing scoliosis.

Limitations of Cobb-Webb angle include the following:

• Uniplanar measurement of a 3D deformity
• Interobserver variation
• Diurnal variation, with angles 5° greater in the afternoon than in the morning
• Variations that occur with changes in supine and upright positioning, rotation, body shape, and radiographic technique
• Spinal growth of 1° per month during periods of rapid growth (Frequent assessments (eg, every 3-4 mo) are need for accurate measurements of the curve.)
• Angle of curvature determined only by the orientation of the end vertebra
• Values higher than those obtained with other measurement techniques

A 10° measurement difference should be present to be 95% confident that the curve is progressing.

The Lippman-Cobb classification of scoliotic curvature is as follows:

• I = Less than 20°
• II = 21-30°
• III = 31-50°
• IV = 51-75°
• V = 76-100°
• VI = 101-125°
• VII = Greater than 125°

Ferguson technique

A line is drawn from the center of the apical vertebra to the center of the superior end vertebra. Another line is drawn from the center of the apical vertebra to the center of the inferior end vertebra. The angle between these lines is used to assess the severity of the deformity.

Greenspan index

This technique provides a measurement of the scoliotic curve more comprehensive than that obtained with other methods. The midpoint of the vertebra above the upper end vertebra and the midpoint of the vertebra below the lower end vertebra are joined to form a vertical spinal line. Lines are drawn from the center of each vertebra in the scoliotic curve to the vertical spinal line. The value of these individual lines are added and divided by the length of the vertical spinal line. A correction factor is added for magnification. In a healthy person, the value is zero. This method is superior to the Lippman-Cobb technique because it allows the clinician to measure the deviation at each individual vertebral level. This technique is also valuable in measuring short-segment or small curvatures.

Nash-Moe technique of assessing vertebral rotation

This is a measure of rotational deformity of the vertebra. On frontal images, the vertebra is divided into 6 segments, and the rotation is quantified on the basis of where the pedicle is located. The pedicles are normally situated in the outer segments. The rotation is graded according to the extent of migration of the pedicle toward the convex side of the curve.

Cobb method of assessing vertebral rotation

The Cobb technique uses the position of spinous process for assessing the degree of vertebral rotation. The vertebra is divided into 6 equal segments by drawing 5 vertical lines. The spinous process is normally situated in the midpart of the vertebra overlying the third line. With increasing rotation, the spinous process is rotated toward the convex side of the curve.

Risser index

The Risser index is used to measure ossification of the iliac apophysis, which is graded as follows: Grade I is ossification of the lateral 25% of the iliac apophysis. Grade II is ossification of the lateral 50%. Grade III is ossification of the lateral 75% of the apophysis. Grade IV is ossification of the entire apophysis. Grade V is fusion of ossified epiphysis to the iliac wing.

Scoliotic curves usually progress during periods of rapid growth, such infancy and adolescence, and they stop growing after spinal maturation is complete. Spinal growth is completed at approximately 15 years 3 months of age in female adolescents and 15 years 10 months of age in male adolescents. This maturation coincides with the completion of ossification in the iliac apophysis, which begins at around 15 years in male adolescents and around 14 years in female adolescents. The whole process of ossification from stage I to stage IV requires 12-18 months.

After ossification, the apophysis fuses with iliac crests in 2 years in girls and slightly faster than this in boys. Progression usually does not happen after grade IV maturity of iliac apophysis is achieved. If the curve is 50-80° at the time of maturity, it tends to progress even after the apophysis fuses, especially if the curve is in the thoracic and lumbar region. However, this progression is far slower than the progression that occurs during adolescence.

Limitations of Risser index can be summarized as follows: (1) Ossification starts earlier than previous thought; hence, this index is not reliable. (2) The index is less reliable in male patients than in female patients because their ossification starts early. In male patients, growth should be considered completed when a Risser index of only 5 is achieved. (3) Recent data indicate that this index is not an accurate measure of completed maturity, spinal growth, or progression of the deformity.

Observation for ossification of the vertebral ring apophysis

This is an alternate method for assessing skeletal maturity. Before skeletal maturity, the vertebral ring apophysis is absent, or it is incompletely formed or completely formed without fusing to the body. After skeletal maturity, the vertebral ring apophysis fuses to the body. This occurs by 16 years in female adolescents and 19 years in men.

Difference in the rib-vertebral angle

This parameter is useful in predicting the progression of the curve in the idiopathic infantile type of scoliosis.

A line is drawn along the inferior border of the apical vertebra, and another line is drawn perpendicular to the first. The midpoints of the head and neck of ribs on either side of the apical vertebra are connected by lines. These lines are extended to meet the perpendicular line drawn initially, and the angles they make are called rib-vertebral angles.

In thoracic curves, the angle is usually smaller on the convex side than the concave side because of the greater obliquity of the ribs on the convex side. In combined thoracic and lumbar curves, the angle is low at level of apical thoracic vertebra and can be greater on the convex side. This curve can be further negative because of the associated drooped 12th rib on the concave side of the curve.

In resolving curves, the angle is less than 20° and more than 20° in progressive curves. Subsequent images obtained after 2-3 months show a decreased angle in resolving curves and the same or increased angle in progressive curves.

Perdriolle method

The Perdriolle method is used to measure apical vertebral rotation.

Lytilt method

The Lytilt method is used to measure the angle between the L4 vertebra and a line connecting the iliac crests.

Other methods of assessing skeletal maturity

Ossification and maturation of the epiphysis of the left hand and wrist are compared with standards. Two main methods are used. The first is the Greulich-Pyle method in which the radiograph of hand and wrist is compared with standard radiographs in the atlas. The second is the Tanner-Whitehouse method in which the epiphysis of the hand and wrist are compared with those of the atlas. A score is assigned to each of them, and the sum is compared with values on standard tables. Thus, bone age is assessed.

Surgical radiographic assessment

Immediate preoperative radiographic assessment

The immediate preoperative assessment should include Chest radiographs for cardiovascular assessment, supine and recumbent AP views of the spine, right and left lateral bending images, and traction views.

The bending and traction views are helpful in assessing the site of fusion, the degree of correction required, and the placement of spinal devices.

Surgeries for scoliosis

Surgeries for scoliosis include the following techniques: (1) A single rod can be used to fix the upper and lower end of curves with a posterior approach. Disadvantages are prolonged immobilization or use of braces and suboptimal results. (2) Two Harrington or Luque rods can be used to accomplish segmental stabilization at each level of spine using sublaminar wires. (3) Use of the Cotrel-Dubousset system with multiple hooks with rods may improve 3D results. (4) Use of pedicular screws to fix the spine increases fixation, reduces the number of levels fused, and reduces the number of junctional problems above and below the fused vertebra. (5) An anterior approach can be used with thoracotomy or thoracoscopy in which single or double rods with screws are attached to each vertebral body. Better results. Results are better than those of other methods, and this approach treats the rib bump at same time.

Postoperative radiographic assessment

In the immediate postoperative period, chest radiographs are used to assess for complications. Frontal and lateral spinal images are required to assess the postoperative pine. The degree of correction of the curve can also be evaluated.

Recognized complications are damage to the rods or wires, dislocation or migration of the rods, loosening of a device, spondylolysis, pseudoarthrosis, aortic aneurysm, retroperitoneal fibrosis, gastric volvulus, and progression of the deformity (crankshaft phenomenon). This last complication occurs when surgery is performed before maturity (Risser index <1 and age <10 y). The unfused vertebrae and portions of the vertebrae not included in the fusion continue to grow, producing progressive deformity. This effect is marked in posterior fusion, in which the anterior portions of vertebra continue to grow and produce a new curve.

Follow-up assessment

Follow-up assessment should be routinely performed until the patient reaches maturity.

Radiation protection

The radiation dose is an important factor in evaluation of scoliosis. Studies by Nash et al indicate that the risk of carcinogenesis is mildly increased.

Techniques for radiation protection include the use of the following: PA view to reduce exposure to the breast; rare-earth screens; high kilovolt setting; high speed film; filters for upright views; tube head filters; good beam collimation; digital radiographic techniques; and breast, gonad, and thyroid shields.

CT SCAN

Section 5 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Findings

CT findings

The scoliotic deformity can be visualized on CT scans of the thorax and abdomen. Associated lesions, such as osteoid osteoma, osteoblastoma, infection, tumors, disk prolapse, and costovertebral dislocation, can be found.

CT techniques

With modern multidetector-row CT scanners, thin sections of the whole body can be obtained within a few seconds and reconstructed in any plane: sagittal, coronal, oblique, or axial. Even 3D reconstruction with shaded-surface display or volume rendering is possible.

CT myelography is not routinely done, and it is not needed in idiopathic scoliosis. This is useful for evaluating intraspinal lesions, such as diastematomyelia, a tethered cord, or intraspinal tumors. Compression of the spinal cord can also be assessed.

Role of CT in evaluating scoliosis

CT is performed for an evaluation of segmentation abnormalities with 3D reconstructions, though MRIs have largely replaced these scans. CT is also used to evaluate postoperative complications because MRIs may show metallic artifacts. In addition, CT helps in evaluating intrinsic rotational deformity. Scoliotic deformity can be visualized on CT scans of the thorax and abdomen. Associated lesions, such as osteoid osteoma, osteoblastoma, infection, tumors, disk prolapse, and costovertebral dislocation, can be found. Finally, associated rib-cage deformity is best assessed with CT scans. The rib-cage deformity is well correlated with the longitudinal deformity at the level of the apical vertebra.

CT myelography is done to assess suspected radiculopathy, intraspinal lesions, or cord compression.

Indices used to assess rib-cage deformity

The apical vertebra of the primary curve is identified by using plain radiography. CT scans are then acquired at this level to help in assessing the longitudinal deformity. Several lines are used.

Line 1 is drawn from the center of the posterior aspect of the vertebral foramen to the center of the vertebral body and extended to the anterior chest wall. Line 2 extends from the center of the posterior aspect of vertebral foramen to the anterior midline of the body. Line 3 is a horizontal line is through the center of the posterior aspect of the vertebral foramen. A perpendicular is then drawn from the center of the posterior aspect of vertebral foramen to meet the anterior chest wall.

The rotation of apical vertebra from the anterior midline of the body (RAML) is the angle between the line 1 and line 2. The rotation of the apical vertebra from the sagittal plane (RASag) is the angle between the line 1 and line 3. This is the most definitive method for assessing the severity of scoliosis with CT scans. The results are significantly correlated with the Cobb-Webb angles on plain radiographs. The angle of lateral deviation of the apical vertebra from the midline of body (Mldev) is the angle between line 2 and line 3.

RAML is the sum of RASag and Mldev.

Rib-hump index

The rib-hump index is measured at the level of the rib hump by using several lines. Line 1 is a horizontal line drawn through the center of the posterior aspect of the vertebral foramen to the lateral chest wall on both sides. Line 2 is a horizontal line parallel to the first; this line passes through the peak of the inner rib cage on the hump side. Line 3 is parallel to the first and passes through the peak of the inner rib cage on the side opposite the hump. Line 4 is a perpendicular line drawn from the peak of the inner rib cage on the hump side to meet the first line at point 0.

The rib-hump index is defined as (X - Y)/Z, where X is the distance between line 1 and line 2, Y is the distance between lines 1 and 3, and Z is the distance between point 0 and the center of posterior aspect of the vertebral foramen.

The rib-hump index is directly correlated with RASag.

Postoperative CT

Postoperative CT scanning can be done to assess for the development of complications such as hemorrhage, fracture, or pseudoarthrosis.

MRI

Section 6 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Findings

Role of MRI in evaluating idiopathic scoliosis

MRI is not used for diagnosing scoliosis. It is useful for assessing other etiologic factors, especially spinal-cord anomalies, that can change the diagnosis. Such anomalies are most common in the infantile and juvenile types and include syringomyelia, hydromyelia, spinal-cord tumors, dysraphism, a tethered cord, diastematomyelia, lipomas, neurofibromas, and Chiari malformations.

Idiopathic scoliosis is diagnosed only after its differential diagnoses are excluded. In 1 study, 50% of all cases previously designated as being idiopathic involved some spinal lesion.

Untreated syringomyelia contributes to paraplegia after surgery.

MRI is also used to investigate occult intraspinal tumors, which can occur with scoliosis but without any neurologic symptoms or signs; to exclude other underlying abnormalities, such as tumors, infections, and disk prolapse; to evaluate atypical scoliosis or an atypical curve in a child with normal neurologic findings; to evaluate the patient before surgery because assessment of the spinal cord in patients with postoperative neurologic symptoms can be difficult because surgical devices that produce artifacts; to evaluate rotational deformity and distinguish intervertebral from intravertebral rotation (Standard derotational surgery is suboptimal in those with predominant intravertebral rotation.); and to ascertain the severity of the curve.

Atypical features for which MRI is warranted includes the following:

• Abnormal neurologic finding
• Painful scoliosis
• Signs of dysraphism
• Neck pain, headache
• Weakness, pes cavus, ataxia
• Back pain
• Atypical curves (left-sided thoracic curve, juvenile onset)
• Rapid progression
• Associated lower-limb deformity
• Increased kyphosis
• Thoracic deformity
• Wide spinal canal
• Thin pedicles
• Abnormal somatosensory evoked potentials

In 2001, Twee et al found that only 7 of 327 patients with diagnosed idiopathic scoliosis had other abnormalities on routine MRI. None of the newly diagnosed pathologies were clinically important in terms of future management.

MRI technique

MRI is performed in the sagittal, axial, and coronal planes by using T1- and T2-weighted sequences. Proper technique is difficult, especially if the patient has more than 1 curve.

Postoperative MRI

MRI is indicated if the patient develops neurologic deficits after the procedure. If MRI is being done for the first time, occult spinal and cord lesions cannot be detected. Imaging might be difficult because of the presence of spinal instruments. Hemorrhage, pseudoarthrosis, and tumors can be detected.

Degree of Confidence

Important considerations are intraspinal tumors. Intraspinal tumors occasionally cause scoliosis and no other symptoms. In such cases, idiopathic scoliosis might be diagnosed. Only MRI can depict intraspinal tumors. The identification of notable neurologic and other diseases alters management.

If the patient develops neurologic symptoms postoperatively, assessment of the spinal cord is difficult because of the surgical devices, which produce artifacts. Hence, a routine preoperative MRI is considered useful.

False Positives/Negatives

Although MRI has been advocated in patients with atypical scoliosis, data confirming the benefit of this approach are lacking.

MRI can depict a number of findings; however, a recent study revealed no significant difference in the incidence of anomalies between those with atypical findings and patients without atypical findings. Even if anomalies such as syringomyelia and Chiari malformation are found, they do not affect management. Therefore, the effectiveness of MRI as a diagnostic tool is questioned.

Some centers still routinely use MRI, and others use it only if surgery is contemplated or if atypical signs are present.

ULTRASOUND

Section 7 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Findings

Ultrasonography has only limited application in scoliosis. If scoliosis is seen in a neonate or child with spina bifida, a sonogram of the spine can be obtained to assess the spinal cord. The position of the cord, including tethering, can be evaluated. Associated lesions, such as myelomeningocele, lipomas, epidermoids, those due to diastematomyelia, are also seen.

It can be useful to assess soft-tissue complications, such as hematomas and abscesses, after surgery.

NUCLEAR MEDICINE

Section 8 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Findings

Bone scanning is not routinely performed in idiopathic scoliosis. Bone scans are obtained to evaluate atypical or painful scoliosis and to exclude infection. Focal hot spots can be seen in osteoid osteomas, osteoblastomas, infections, and other primary tumors that can cause painful scoliosis. Bone scans may also help in assessing for surgical complications including infection. A WBC scan may be required to differentiate infection from postoperative changes in the spine. Focal hot spots are also seen in stress fractures, spondylosis, and pseudoarthrosis in the fused segments.

Degree of Confidence

Bone scanning is highly sensitive in the diagnosis of bone lesions. Osteoid osteoma is the most common cause of painful scoliosis. Bone scanning is helpful in assessing this condition and for showing increased uptake.

MULTIMEDIA

Section 9 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Multimedia
• References

Media file 1:  Mild juvenile scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 2:  Anteroposterior (AP) radiograph shows mild adolescent scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 3:  Lateral view of mild adolescent scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 4:  Moderate scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 5:  Severe infantile scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 6:  Severe typical scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 7:  Line diagram illustrates the common terms used in describing scoliosis.
	View Full Size Image
Media type:  Image

Media file 8:  Plain radiograph illustrates the common terms used in describing the scoliotic curve. The upper and lower end vertebrae and apical vertebra are illustrated. The vertebrae and disk spaces are smaller on the concave side and larger on the convex side. The spinous process is rotated towards the concave side. The ribs are crowded on the concave side.
	View Full Size Image
Media type:  X-RAY

Media file 9:  Line diagram illustrates measurement of the Lippman-Cobb angle.
	View Full Size Image
Media type:  Image

Media file 10:  Radiograph shows measurement of Lippman-Cobb angle.
	View Full Size Image
Media type:  X-RAY

Media file 11:  Line diagram illustrates measurement of the Cobb angle by using a modified technique.
	View Full Size Image
Media type:  Image

Media file 12:  Radiograph shows modified Cobb angle.
	View Full Size Image
Media type:  X-RAY

Media file 13:  Line diagram shows the Risser-Ferguson technique.
	View Full Size Image
Media type:  Image

Media file 14:  Radiograph shows measurement by using the Ferguson technique.
	View Full Size Image
Media type:  X-RAY

Media file 15:  Line diagram illustrates the Greenspan technique.
	View Full Size Image
Media type:  Image

Media file 16:  Radiograph shows measurement of the Greenspan index of scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 17:  Line diagram shows the Nash-Moe method of measuring vertebral rotation.
	View Full Size Image
Media type:  Image

Media file 18:  Line diagram illustrates the Cobb method of measuring vertebral rotation.
	View Full Size Image
Media type:  Image

Media file 19:  Radiograph shows various grades of vertebral rotation in the spine. The pedicles are normal in the bottom vertebra, but they are moving toward the center in the upper vertebra. The spinous process is in midline in the bottom vertebra, and it is displaced in the upper vertebrae.
	View Full Size Image
Media type:  X-RAY

Media file 20:  Line diagram shows rib–vertebral angle difference (RVAD) (Mehta, 1976).
	View Full Size Image
Media type:  Image

Media file 21:  Radiograph shows measurement of difference in the rib-vertebral angle.
	View Full Size Image
Media type:  X-RAY

Media file 22:  Line diagram illustrates the Risser index.
	View Full Size Image
Media type:  Image

Media file 23:  Vertebral apophysis maturation. Left image shows the ossification center. Ossification is complete in the middle image. Right image shows fusion indicating vertebral maturation.
	View Full Size Image
Media type:  Image

Media file 24:  Right lateral bending view of a patient with scoliosis.
	View Full Size Image
Media type:  X-RAY

Media file 25:  Left lateral bending of the same patient as in image 24 shows persistence of the scoliotic curve, which indicates its structural nature.
	View Full Size Image
Media type:  X-RAY

Media file 26:  MRIs show cervical scoliosis.
	View Full Size Image
Media type:  MRI

Media file 27:  Sagittal MRIs show lumbar scoliosis.
	View Full Size Image
Media type:  MRI

Media file 28:  Axial MRI shows apical vertebra.
	View Full Size Image
Media type:  MRI

Media file 29:  Sagittal MRI shows an Arnold-Chiari I malformation and syringomyelia.
	View Full Size Image
Media type:  MRI

Media file 30:  3-dimensional (3D) reconstruction of mild scoliotic curve without segmentation anomaly.
	View Full Size Image
Media type:  Image

Media file 31:  Coronal reconstructions from multidetector-row CT show several hemivertebrae. Idiopathic scoliosis is diagnosed only after underlying structural conditions such as these are excluded.
	View Full Size Image
Media type:  CT

Media file 32:  3-dimensional (3D) reconstructed CT scan of the same patient as in Image 31 shows the hemivertebrae.
	View Full Size Image
Media type:  CT

Media file 33:  CT is good for assessing rotation of the vertebra.
	View Full Size Image
Media type:  CT

Media file 34:  Line diagram illustrates measurement of the CT index.
	View Full Size Image
Media type:  Image

Media file 35:  Line diagram illustrates measurement of the CT rib-hump index.
	View Full Size Image
Media type:  Image

Media file 36:  CT scan illustrates the indices useful for assessing the extent of rotation.
	View Full Size Image
Media type:  CT

Media file 37:  Bone scans in a patient with painful atypical scoliosis are normal.
	View Full Size Image
Media type:  Image

Media file 38:  Intraoperative image shows screw fixation.
	View Full Size Image
Media type:  X-RAY

Media file 39:  Intraoperative image shows screw fixation.
	View Full Size Image
Media type:  X-RAY

Media file 40:  Harrington rods with wires, hooks, and screws.
	View Full Size Image
Media type:  X-RAY

Media file 41:  Harrington rods with wires, hooks, and screws as shown on a lateral radiograph.
	View Full Size Image
Media type:  X-RAY

Media file 42:  Anteroposterior (AP) view of fixation by using pedicle screws.
	View Full Size Image
Media type:  X-RAY

Media file 43:  Lateral view of pedicle screws.
	View Full Size Image
Media type:  X-RAY

Media file 44:  Coronal CT appearance of pedicle screws.
	View Full Size Image
Media type:  C