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ECR 2012 / C-0469
Scoliosis imaging - a review of techniques, classification and case examples
Congress: ECR 2012
Poster No.: C-0469
Type: Educational Exhibit
Keywords: Congenital, Education, Conventional radiography, MR, CT, Neuroradiology spine, Musculoskeletal spine, Bones
Authors: A. U. Desai, S. Saha, G. Nussbaum, R. Houghton; London/UK
DOI:10.1594/ecr2012/C-0469

Imaging findings OR Procedure details

An understanding of the nomenclature and methods of measurement used to describe scoliosis is essential. Identification of the curve apex and significant vertebrae is imperative in defining the type of curve, selecting the surgical approach and determining the optimal level for fusion.  

 

NOMENCLATURE [1,2]

 

The apex is the vertebra or disc with the greatest rotation or furthest deviation from the centre of the vertebral column. It also has the least amount of tilt, as measured by the angle of the endplates (top and bottom edges of vertebral body).

 

The end/translational vertebrae are the most superior and inferior vertebra which are least displaced and rotated and have the maximally tilted end plate towards the apex of the curve. These vertebrae are used to measure the Cobb angle.

 

Vertebrae that show no evidence of rotation on standing frontal (either posteroanterior [PA] or anteroposterior [AP]) radiographs are called neutral vertebrae and usually have normal symmetrically positioned pedicles.

 

Neutral vertebrae may be at the same levels as end vertebrae, either above (proximal to) or below (distal to) the curve, but are never nearer to the apex than end vertebrae are.

 

Stable vertebrae are the vertebrae furthest cephalad that are bisected or nearly bisected by the central sacral vertical line (CSVL) at a level below the end vertebra of the distal curve.

 

IDENTIFICATION OF PRIMARY AND SECONDARY CURVES [1,2]

 

Major or primary curves are the largest abnormal curves in the scoliotic spine and are the first to develop. Minor curves (secondary curves), are smaller develop later to compensate for imbalance that occurs secondary to the progression of major curves by repositioning the head and trunk over the pelvis to maintain balance. The terms major curve and minor curve are sometimes used as synonyms for structural curve and non structural curve respectively, although the definitions of these entities do not correspond exactly.

 

A structural curve is not correctable with ipsilateral bending due to vertebral morphologic changes such as wedging and rotation. In contrast, there are no vertebral morphologic changes in a nonstructural curve, which is a mild compensatory curve enabling sagittal and coronal truncal balance and thus is correctable with ipsilateral bending.

 

A nonstructural curve does not usually progress. However, a nonstructural curve may progress to a structural curve if ligament shortening results from growth retardation on the concave side of curvature [6]. Differentiation between structural and nonstructural curves is important when selecting the appropriate level for fusion. A structural curve may be reliably defined as one with a Cobb angle of 25° or more on ipsilateral side-bending radiographic views. 

 

KEY MEASUREMENTS [1,2]

 

Cobb angle (Figure 2)

 

The Cobb angle is used for the evaluation of curves in scoliosis on an AP radiographic projection of the spine. When assessing a curve the apical vertebra is initially identified. The end/transitional vertebra are then identified through the curve above and below. A line is drawn along the superior end plate of the superior end vertebra and a second line drawn along the inferior end plate of the inferior end vertebra. If the end plates are indistinct the line may be drawn through the pedicles. The Cobb angle is defined either as the angle between the tangential lines or the angle between two lines drawn perpendicular to the tangents. When correctly measured these two angles are identical. Scoliosis is defined as a Cobb angle of 10 degrees or more.

 

Central sacral vertical line (Figure 3)

 

The central sacral vertical line (CSVL) is a roughly vertical line that is drawn perpendicular to an imaginary tangential line drawn across the top of the iliac crests on radiographs. It bisects the sacrum. The CSVL serves as a reference for identifying stable vertebrae, evaluating coronal balance and determining the curve type.

 

Plumb line

 

The plumb line is used to evaluate coronal balance on standing frontal radiographs and sagittal balance on standing lateral radiographs. A vertical line is drawn downwards from the odontoid or C7 vertebral body. The plumb line should fall through the L5/S1 disc space in both sagittal and coronal planes. Any other alignment suggests decompensation in the sagittal or coronal plane.

 

Coronal balance can be evaluated by measuring the distance between the CSVL and the plumb line. Sagittal balance is evaluated by measuring the distance between the posterosuperior aspect of the S1 vertebral body and the plumb line. A distance greater than 2 cm is considered abnormal for both coronal and sagittal measurements. For measurements of coronal balance, a plumb line located to the right of the CSVL is considered to reflect positive coronal balance, whereas a plumb line located to the left of the CSVL is considered to reflect negative coronal balance. For measurements of sagittal balance, a plumb line that is anterior to the posterosuperior aspect of the S1 body is considered to reflect positive sagittal balance, whereas a plumb line that is posterior to the posterosuperior aspect of the S1 body is considered to represent negative sagittal balance.

 

THE CLASSIFICATION OF SCOLIOSIS

 

The aetiology of scoliosis largely determines the natural history and treatment for the patient. The aetiology of scoliosis is broadly classified as idiopathic, congenital, neuromuscular, degenerative and pathological.

 

IDIOPATHIC SCOLIOSIS

 

Idiopathic scoliosis is the most common type of scoliosis and accounts for approximately 80% of cases. The exact aetiology is unknown, although it may be considered as a complex genetic trait disorder. A familial predisposition has been accepted, although the pattern of inherited susceptibility is uncertain.

 

Adolescent idopathic scoliosis (AIS)

 

Adolescent idiopathic scoliosis (AIS) can be subdivided according to three distinct peak period of onset; infantile (before the age of 3), juvenile (age 5-8 years), adolescent (age 10 years until the end of growth) [3] .

 

Infantile form (before the age of 3 years) 

  • More common in boys than in girls.
  • Usually involves the thoracic region with convexity to the left side
  • May be associated with skull and pelvic abnormalities.
  • Infantile scoliosis often spontaneously resolves, although some cases may progress, especially in the first 18 months.

Juvenile forms (between 4 and 9 years of age)

 

  • Most cases involve the dorsolumbar region with convexity to the left side.
  • Usually progressive.

Adolescent form (between 10 years of age and maturity)

 

  • Most common type of idiopathic scoliosis affecting females more than males.
  • 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.

Curve classification 

 

Curve classification is based on the apex of the curve:

  • Cervical – Apex between C1 and C6.
  • Cervicothoracic – Apex between C7 and T1.
  • Thoracic – Apex between T2 and the T11-T12 disc space.
  • Thoracolumbar – Apex between T12 and L1.
  • Lumbar – Apex between the L1-L2 disc space and L4.
  • Lumbosacral – Apex between L4-S1.

There are two main classification systems used to measure the curve and its magnitude:

 

The King Classification system is the traditional classification of thoracic curves and identifies five different types of thoracic scoliosis curves:

  • King I – Lumbar curve greater than the thoracic curve.
  • King II – Thoracic curve with a compensatory lumbar curve that crosses the midline.
  • King III – Thoracic curve with a lumbar curve that does not cross the midline.
  • King IV – Long thoracic curve in which L4 is tilted into the curve.
  • King V – Double thoracic curve.

 

The Lenke classification  (figure 4) is a more comprehensive system which takes into account the frontal curve of the spine (coronal plane), the curve of the spine from front to back (sagittal plane) and the side to side twisting of the spine (axial plane) [4]. Frontal, lateral and bending radiographs are required for evaluation. Each scoliosis curve is then classified in three steps by the region of the spine, the degree or angle of the curve, and the relationship of the side-to-side curve to the sagittal plane.

 

Step 1: Curve Type

The larger curve is always considered structural; smaller curves are structural if the patient fails to bend less than 25o.

  • Type 1 – Single thoracic.
  • Type 2 – Double thoracic.
  • Type 3 – Double major.
  • Type 4 – Triple major.
  • Type 5 – Lumbar curve without thoracic curve.
  • Type 6 – Lumbar curve with compensatory thoracic curve.

 

Step 2: Lumbar Spine Modifier

This is based on where the CSVL falls in relation to the apical lumbar vertebrae

  • A – CSVL falls between the pedicles.
  • B – CSVL falls on the pedicle or lateral to the pedicle within the vertebral body.
  • C – CSVL falls outside of the vertebral body.

 

Step 3: Thoracic Kyphosis Modifier

Measured from T5 to T12.

  • ‘-‘ – Kyphosis less than 10o.
  • ‘N’ – Kyphosis between 10o and 40o.
  • ‘+’ – Kyphosis greater than 40o

Adult idiopathic scoliosis

 

Adult idiopathic scoliosis refers to a patient with history of AIS with increasing symptoms or progression of the deformity into adulthood.

 

It is defined as a coronal plane Cobb angle greater than 10 degrees in a patient older than 20 years. It often presents with symptoms of associated back pain and/or leg pain. The natural history of the curve in mature patients is variable. Curve progression is usually not seen if less than 40 degrees. If greater than 50 degrees, curve progression occurs at approximately 1 degree per year. The rate of curve progression is not constant and risk factors for progression of lumbar curves include lateral apical rotation and lateral and rotatory listhesis. For double curves, the lumbar curves tend to progress more rapidly than the thoracic curve.

 

Treatment of adult scoliosis can be far more challenging than that of AIS for the following reasons:

  • Greater curve stiffness.
  • Presence of degenerative change.
  • Associated medical conditions including osteopaenia.
  • Need for neural decompression which can lead to extended surgery and removal of areas for bony fusion.
  • Sagittal and coronal plane imbalance
  • Frequent need for longer fusions and more combined anterior or posterior procedures.

The systematic imaging assessment of idopathic scoliosis

 

Plain radiographs

 

Posteroanterior-Anterior (PA) Standing

  • Cobb Method for measurement of upper thoracic, thoracic, thoracolumbar or lumbar curves.
  • Determine the deviation of C7 plumb line from the centre-sacral-vertical line (CSVL).
  • Trunk shift: Deviation of the mid distance of the rib margins to CVSL.
  • Risser stage to determine skeletal maturity
    • Risser 0: No ossification of the iliac apophysis.
    • Risser 1-4: Ossification beginning laterally and finishing medially when the iliac wing is divided into four sections.
    • Risser 5: Fusion of the ossified iliac apophysis to the ilium.
    • Status of triradiate cartilage – open or closed.

 

Lateral Radiograph

  • Cobb method to assess for thoracic kyphosis and lumbar lordosis.
  • Assess junctional kyphosis:
    • Between the structural upper thoracic and middle thoracic curves.
    • Between the structural middle thoracic and the thoracolumbar or lumbar curves.
    • Sagittal balance: C7 plumb line normally falls at the posterior edge of L5-S1.
    • Report the presence of thoracic hypokyphosis or apical lordosis. This is normal in adolescent idiopathic scoliosis. Its absence may indicate neural axis pathology.

Bend Films

  • Bolster view – most commonly used technique in our centre:
    • Patient lies on a bolster positioned at the apex of the spinal deformity
    • Allows evaluation of how flexible the curve is and may give useful pre-operative information
  • Supine anteroposterior best effort bend – most commonly used:
    • Patient lies supine on a table and bends to the right and the left.
  • Patient Prone Test:
    • Patient is prone and the examiner pushes medially and anteriorly on the rotational prominence
  • Fulcrum Bend Test:
    • Patient lies in a lateral position with the apex of curve on a large roll (how is this different from a bolster view).
    • May be better for the assessment of thoracic curve flexibility.
  • Traction Films:
    • Supine patient has manual traction applied.
    • Standing patient has halter traction applied (what is halter traction).

Bend films are used to determine curve type – more than 25 is structural and determine the flexibility index for each curve. The flexibility index can be calculated by subtracting the bend Cobb angle from the PA Cobb angle and dividing by PA Cob x 100.

 

The role of MR imaging in idopathic scoliosis

 

Absolute indications:

  • Neurological abnormalities.
  • Juvenile and infantile onset.
  • Congenital vertebral anomalies.
  • Cutaneous manifestations of dysraphism.

 Relative Indications:

  • Atypical curve pattern – left thoracic curve or thoracic kyphosis.
  • Rapidly progressing curve.
  • Painful scoliosis. Bone scan may be helpful in painful scoliosis without known aetiology. 

CONGENITAL SCOLIOSIS

 

Congenital scoliosis is a lateral curvature of the spine that is caused by anomalous vertebral development in the embryo. These vertebral anomalies despite being present at birth, may not present clinically until later on in childhood, when progressive scoliosis is evident.

 

Congenital spinal deformity can be classified according to the three types of anomalies using the MacEwen classification.

 

Failure of formation.

  • Partial failure of formation (wedge vertebra)
  • Complete failure of formation (hemivertebra)

 Failure of segmentation.

  • Unilateral failure of segmentation (unilateral unsegmented bar)
  • Bilateral failure of segmentation (block vertebra)

 Mixed.

  • Elements of failure of formation and of failure of segmentation
    • Anterior formation failure results in a kyphosis, which is sharply angulated.
    • Posterior formation failure is rare but can produce a lordotic curve.
    • Lateral formation failure occurs frequently and produces the classic hemivertebrae of congenital scoliosis.
    • Anterior segmentation failure (anterior unsegmented bar) leads to progressive kyphosis due to absence of anterior vertebral growth.
    • Posterior segmentation failure, if symmetrical results in lordotic deformities.
    • Lateral segmentation failure (unilateral unsegmented bar) often results in some of the worst and most unrelenting scoliotic curves.
    • Total segmentation failure produces block vertebrae, resulting in shortening of the spine.
    • Posterolateral and anterolateral segmentation failures are rare and produce a lordoscoliosis and kyphoscoliosis, respectively.

Variations in the structure of hemivertebrae are common and the prognosis depends on specific patterns seen.

 

Hemivertebrae can be subclassified as follows:

  • Incarcerated hemivertebrae usually do not produce alignment abnormalities as the vertebral bodies above and below the abnormal segment are shaped to accommodate the hemivertebrae.
  • Nonincarcerated hemivertebrae lie at the apex of a scoliosis with the curve magnitude depending on the size of the wedged segment.
  • Segmented (figure 5) or free hemivertebrae have a normal disk above and below and are more likely to result in a progressive curvature, due to unbalanced growth from the wedge-oriented endplates.
  • Unsegmented hemivertebrae lack disk spaces between the wedged and normal adjacent vertebral bodies.
  • Semisegmented hemivertebrae have a normal disk space on one side and are unsegmented at the opposite end.

The natural history of these congenital deformities is essential as it dictates the prognosis and treatment [5]. The rate of deterioration and final severity of congenital scoliosis and thus prognosis is dependent on several factors:

 

1. Type of vertebral anomaly.

 

  • Unilateral unsegmented bar with contralateral hemivertebrae at the same level causes the most severe scoliosis. A unilateral unsegmented bar with or without contralateral hemivertebra, is associated with a poor prognosis and should be treated immediately, without a period of observation
  • Next in severity is a scoliosis caused by a unilateral unsegmented bar alone, followed by 2 unilateral fully segmented hemivertebrae, a single fully segmented hemivertebra, and a wedge vertebra
  • The least severe scoliosis is caused by a block vertebra
  • Congenital scoliosis caused by unclassifiable anomalies are often difficult to predict and requires careful monitoring

 

 2. Site of the anomaly.

 

  • The rate of deterioration of scoliosis is most severe in the thoracic and thoracolumbar regions and is usually less severe in the cervicothoracic and lumbar regions.

 

3. Age of the patient at the time of diagnosis.

 

  • Congenital scoliosis progresses most rapidly during the preadolescent growth spurt after the age of ten.
  • Scoliosis presenting as a clinical deformity in the first few years of life has a particularly bad prognosis as the growth imbalance will continue throughout the period of growth, resulting in severe deformity.

 

4. Balance and pattern of the curve.

  • Multiple balanced anomalies throughout the spine in general do not progress.
  • Unbalanced anomalies are more likely to progress.

Systematic imaging assessment in congenital scoliosis

 

Plain radiographs 

  • PA and lateral radiographs used for initial evaluation.
  • Standing films show the characteristics of the curve under gravity, with its compensation and torso-pelvic relationships.
  • Supine, coned-down views of the anomalous region may be helpful to visualise the defects and their patterns further.
  • Bending films allow evaluation of rigidity or flexibility of the curves and their adjacent motion segments.
  • Assessment of disc spaces to ascertain whether convex growth is possible: If the disk spaces are present and clearly defined and the convex pedicles clearly formed, convex growth is possible, the prognosis is poor. If the convex disks are not clearly formed and the convex pedicles are poorly demarcated, less convex growth potential is present, and the prognosis is better [6].
  • Rib vertebral angle (RVA) - angle formed by perpendicular line from apical vertebral end plate and a second line from the mid-neck to mid-head of the adjacent rib.
  • The rib vertebral angle difference is the difference between two RVA on the concave and convex sides of the curve – a curve greater than 20 degrees is considered progressive.

The role of CT/MRI in imaging congenital scoliosis   

 

  • CT may be used to evaluate congenital spinal deformities, especially the presence and extent of unsegmented bars and incarceration of hemivertebrae (Figures 6 - 11).
  • Three dimensional CT images may provide further depiction of congenital anomalies and their interrelationships [7]
  • CT and MRI are particularly useful in detailing bony canal anatomy and associated spinal cord dysraphism (Figures 12 - 17) (Figures 18 - 23) - these evaluations are mandatory prior to surgical intervention because spinal cord tethering and diastematomyelia must be identified and released prior to correction of the curve.

NEUROMUSCULAR SCOLIOSIS

 

Progressive neuromuscular scoliosis is a common deformity, which can occur in a number of neuromuscular diseases such as poliomyelitis, cerebral palsy, spina bifida, muscular dystrophy or spinal cord injuries. The pattern and incidence of neuromuscular scoliosis varies greatly, however, the prevalence of spinal deformity in a patient with a neuromuscular disorder is much higher than in the general population.

 

Scoliosis associated with neuromuscular disorders has been classified by the Scoliosis Research Society into neuropathic and myopathic types. Neuropathic conditions are subdivided into those with:

  1. Upper motor neuron lesions e.g. cerebral palsy, syringomyelia and spinal cord trauma.
  2. Lower motor neuron lesions including poliomyelitis and spinal muscular atrophy.

The myopathic conditions include arthrogryposis, muscular dystrophy, and other forms of myopathy.

 

Typical neuromuscular scoliosis deformity involves the entire thoracic and lumbar spine with the apex usually occuring near thoracolumbar junction, often creating pelvic obliquity and postural problems. (Figure 24 - 25 ) Progressive deformity interferes not only with general health and well-being, but with ambulation, sitting-balance and wheelchair transmission. This disability ultimately leads to decubiti, costopelvic impingement pain, and worsening of pulmonary status [8].

 

Systematic imaging assessment of neuromuscular scoliosis

 

Plain radiographs 

  • Supine anteroposterior and lateral spinal radiographs reserved for patients who are unable to sit.
  • Upright anteroposterior and lateral spinal radiographs – provides accurate depiction of the true magnitude of the spinal deformity under the effect of gravity and of pelvic obliquity and spinal balance.
  • Traction spinal radiographs using manual distraction with head halter and leg traction can be used to evaluate the flexibility of the curves.

ADULT DEGENERATIVE (DE NOVO) SCOLIOSIS

 

Adult degenerative scoliosis (ADS) is typically diagnosed in patients over the age of 40 years and without a history of AIS. Symptomatic patients usually present during the sixth and seventh decade of life with pain secondary to neurogenic claudication and radicular symptoms. The prevalence of de novo curves is approximately 1-10%. In general, the deformity usually begins as the intervertebral discs start to deteriorate. Subsequent degeneration leads to an eventual lack of competency of the posterior elements especially the facet joints and axial rotation of the involved spinal segments leads to lateral listhesis and ligament laxity. The deformity is usually a lumbar curves measuring > 10o with associated distal fractional curves. These lumbar curves are not associated with structural thoracic curves, although compensatory thoracic curves can occur. The average curve progression is approximately 3o per year.

 

Systematic imaging assessment of adult degenerative (de novo) scoliosis

 

Plain radiographs

 

 

PA and lateral radiographs should include cervical spine down to the pelvis.

 

 

PA Radiographs

  • Assessment of Cobb angle of all curves.
  • Coronal imbalance (measured as trunk shift from the CSVL or a deviation of a C7 plumb from the CSVL).
  • Rotator listhesis or subluxation.
  • Disc height and wedging.
  • Osteophyte formation.

Lateral Radiographs

  • Cobb measurement for thoracic kyphosis (T5-T12) and lumbar lordosis (L1-L5) – loss of lumbar lordosis usually seen.
  • Sagittal balance – The C7 plumb line should fall on the posterior aspect of the L5-S1 disc level.
  • Disc space and height.
  • Assessment of osteopaenia.
  • Degree of facetal degeneration.

 Bend Films

  • Supine right sided and left sided bend films conducted to assess flexibility – especially useful if anterior surgery is being considered and are useful in aiding level of fusion.
  • Traction films – useful for assessment of flexibility and selection of fusion level.
  • Ferguson view – Provides excellent view of lumbosarcral junction and involves X-ray beam being directed 30 degrees cephalad with focus on lumbosacral junction.

The role of CT imaging in assessing adult degenerative scoliosis 

  • CT has now largely been replaced by MRI.
  • Indications for CT include (1) inability to get MRI (2) assessment of central and lateral recess stenosis and presence of disc herniations in the setting of previous spinal intervention and (3) assessment of integrity of spinal fusion.
  • CT is still an accurate method for evaluation of bone density, anatomy, canal and foraminal stenosis and bony fusion.

The role of MR imaging in assessing adult degenerative scoliosis 

  • Axial and sagittal T1 and T2 weighted images acquired
  • Assessment of central and lateral recess stenosis, disc herniation and degeneration.
  • Allows planning for fusion levels.

PATHOLOGICAL SCOLIOSIS

 

Pathological scoliosis can occurs secondary to a number of causes. The most common causes are discussed below:

 

Neurofibromatosis

 

Neurofibromatosis type 1 (NF1) or von Recklinghausen disease is an autosomal dominant multisystem disorder caused by a mutation of a gene located on the long arm of chromosome 17. Clinical manifestations include plexiform neurofibromas, which are the hallmark of the disease, schwannomas, and dermatological manifestations such as cafe au lait spots and axillary freckling.

 

Scoliosis is the most common osseous defect associated with NF1 and may vary in severity from mild and nonprogressive to severe curvatures. Approximately 2% of patients with scoliosis have neurofibromatosis, whereas 10-20% of patients with neurofibromatosis have some form of spinal disorder. All preadolescent children with neurofibromatosis should be evaluated with scoliosis screening, or the bend test, to exclude a spinal deformity, which usually occurs earlier in children with neurofibromatosis.

 

Two primary types of scoliosis are observed in neurofibromatosis:

 

Dystrophic scoliosis 

  • Short-segmented, sharply angulated scoliosis that includes fewer than 6 spinal segments.
  • Tendency to progress to a severe deformity [9].

Non dystrophic scoliosis

  • This form is similar to the idiopathic curvature observed in adolescents and usually involves 8-10 spinal segments.
  • The deformity is usually convex to the right.

Osteoid osteoma [10]

 

Osteoid osteomas are benign osseous tumours which, are usually less than 1.5 cm in diameter and contains a central nidus surrounded by a zone of reactive bone (Figures 26 - 27). Osteoid osteomas account for approximately 10% of benign bone tumours and more commonly affects males than females.

 

Osteoid osteoma of the spine is the most common cause of a painful scoliosis in adolescents. Up to 25% of all osteoid osteomas are found in the spine (usually in the posterior elements), of which 60% are located within the lumbar spine, 27% in the cervical, 12% in the thoracic and 2% on the sacrum.

 

Back pain is an uncommon complaint in adolescents and young adults, and when it occurs in association with paravertebral muscle spasm and scoliosis, osteoid osteoma of the spine must be suspected.

 

Osteoblastoma [10]

 

Osteoblastomas are uncommon primary neoplasms of the bone. They have similar clinical and histologic manifestations to those of an osteoid osteoma and are therefore sometimes considered as two variants of the same disease, with osteoblastoma representing a giant osteoid osteoma. However, an aggressive type of osteoblastoma has been recognized, making the relationship between the lesions less clear.

 

Patients with osteoblastomas usually present with pain of several months' duration. In contrast to the pain associated with osteoid osteomas, the pain of an osteoblastoma is usually less intense.

 

Approximately 40% of all osteoblastomas are located in the spine. The tumors usually involve the posterior elements (Figures 28 - 30), and 17% of spinal osteoblastomas are found in the sacrum.

 

Spinal lesions can cause painful scoliosis, although this is less common with osteoblastomas than with osteoid osteomas. It is though that scoliosis in patients with spinal osteoblastoma is due to paravertebral muscle spasm, although this may not be the case for lesions in the cervical spine. In addition, they may produce neurological deficits secondary to mechanical interference with the spinal cord or nerve roots.

 

Osteoblastomas typically continue to enlarge without intervention, unlike osteoid osteomas, which have limited growth potential and may even regress spontaneously. When clinical and radiographic findings are consistent with the diagnosis of osteoblastoma, an excisional biopsy is appropriate.

 

Mesenchymal disorders

 

This group includes Marfan’s syndrome, mucopolysaccharidoses, osteogenesis imperfecta and juvenile rheumatoid arthritis. The severity and prevalence of scoliosis occurring in mesenchymal disorders is largely dependent on the severity of the underlying disease. Special note is made of Marfan's syndrome below.

 

Marfan's syndrome

 

Marfan’s syndrome is an inherited chromosomal disorder of connective tissue caused by a  defect in the fibrillin gene. Its pathogenesis mainly affects the skeletal, cardiovascular and ocular system, although respiratory, skin, and central nervous system manifestations are well recognised.

 

The incidence of scoliosis in Marfan’s syndrome is 40%-86%, and differs from idiopathic adolescent scoliosis with regard to curve pattern, progression, and symptoms.

 

The double right thoracic – left lumbar curve is the most common type among patients with Marfan’s syndrome, whereas a single pattern is usually seen in the idiopathic type.

 

The onset of scoliosis in Marfan’s syndrome is earlier with severely rigid, painful, and deforming curves, as well as a higher incidence of curve progression. The curve progression is approximately 7-10° per year after the onset of scoliosis, and the curve often progresses rapidly in the early adolescent period during maximal vertebral growth. When it occurs in combination with straight back syndrome, kyphosis, or a chest wall deformity, it may contribute to cardiopulmonary compromise and restriction of lung volume.

 

 

PRINCIPLES OF MANAGEMENT [1,2]

 

Management depends on curve severity, the likelihood of curve progression over time, and the patient’s perception of the deformity and symptoms. Observation, bracing, and surgery are recognised treatment options. All these options are available for the treatment of adolescent idiopathic scoliosis. In contrast bracing has no role in adult idiopathic scoliosis (skeletally mature patients). For congenital scoliosis and other forms of scoliosis with known underlying causes, surgery is the only option when intervention is necessary.

 

Observation

 

Regular observation is a valid approach if a patient with adolescent idiopathic scoliosis has a curvature with a Cobb angle of less than 20° or if a skeletally mature patient has a curvature with a Cobb angle of less than 30° at presentation. Patients are generally followed up at 4- to 12-month intervals.

 

Bracing

 

The aim of bracing is to avoid surgery. Bracing is an option for curves with a Cobb angle of 20°–45° in patients with adolescent idiopathic scoliosis. For curves of 20°–30°, bracing is started only when progression of 5° or more occurs between consecutive visits. On the other hand, when a patient is evidently skeletally immature (Risser grade 2 or lower) and presents with a 30°–45° curve, bracing is commenced at the first visit.

 

Surgery

 

The main goal of surgery in idiopathic scoliosis is to prevent curve progression by achieving bone fusion of the involved vertebral segments. The secondary goals are curve correction, trunk balance restoration, and sagittal contour preservation, while leaving as many mobile segments in the lumbosacral spine as possible. In nonidiopathic scoliosis, the aims of surgery depend on the underlying cause. In the presence of degenerative scoliosis, the goal is primarily spinal decompression and truncal balance correction, whereas in neuromuscular scoliosis it is curve correction. The objectives of curve correction in neuromuscular scoliosis are to restore seating balance, in order to ease wheelchair use, pain control and to support the trunk to augment respiratory function.

 

For idiopathic scoliosis, surgery is generally indicated in skeletally immature patients with a Cobb angle of 45° or more at presentation. Surgery is also advocated for patients with curve progression despite the use of a brace and for those who cannot tolerate the use of a brace. In addition, for skeletally mature patients, surgery is recommended for curves with a Cobb angle of 45° or more, given that curve progression is mostly accompanied by pain (8). Progressive congenital scoliosis, in which the involved spinal segment is usually too short or too inflexible to brace with good results, is also treated surgically.

 

Treatment outcomes have been shown to be better when surgeons endeavour to spare mobile segments of the lower lumbar region when performing fusion so as to minimize the loss of lumbar lordosis and avoid postoperative low back pain. Low back pain has been shown to occur in most patients who undergo fusion beyond the L3 level.

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