Scoliosis (plural: scolioses) is defined as an abnormal lateral curvature of the spine. It is quite common in young individuals and is often idiopathic and asymptomatic. In some cases, however, it is the result of underlying structural or neurological abnormalities.
On this page:
Terminology
Early onset scoliosis refers to scoliosis with a onset <10 years regardless of cause 8.
Scoliosis imaging has extensive terminology that should be used precisely to avoid confusion 1.
Scoliosis
By definition, scoliosis is any lateral spinal curvature with a Cobb angle >10°. Asymptomatic lateral curvature of the spine that is stable, with a Cobb angle ≤10° is known as spinal asymmetry 2.
Naming curves
Each curve of a scoliosis can be described in terms of the direction of convexity as
levoscoliosis: curvature towards the left
dextroscoliosis: curvature towards the right
The most pronounced curve is usually the one at which the main structural abnormality is present and thus in most patients the terms primary curve, major curve and structural curve are interchangeable 1. Secondary curves, minor curves and non-structural curves usually all refer to the less pronounced compensatory curves that develop above and/or below the primary curve to maintain balance 1.
Apex
The apex is the vertebral body or disc space which demonstrates the greatest rotation and/or furthest deviation from the expected center of the vertebral column 1. The endplates of the apical vertebra are often horizontal or near horizontal.
End vertebrae
The end vertebrae are present on either side of the apex and are the vertebrae that are most tilted towards each other 1,4. They form the basis of the Cobb angle.
Neutral vertebrae
Neutral vertebrae are present on either side of the apex and are the vertebrae that demonstrate no rotation (axial plane). In some cases, they will be the same as the end vertebrae although usually, they will be few segments more distal to the apex. They are never closer to the apex than the end vertebrae 1.
Stable vertebra
The stable vertebra is the first vertebra below the lowest curve which is roughly bisected by the central sacral vertical line (CSVL).
Clinical presentation
In most instances, scoliosis is obvious if severe. On examination, the Adams forward bend test (a clinical test for assessing scoliosis) may be positive where a rib hump forms on the side of the convexity.
Pathology
Etiology
The majority (80%) of scolioses have no apparent underlying cause and are termed idiopathic 1. Idiopathic scoliosis can be broken down into infantile, juvenile and adolescent based on the age of the patient.
The remaining 20% of scolioses are the result of other causes. There are many ways to potentially group these causes, but a simple three-pronged grouping strategy is:
neuromuscular: conditions that cause neurological or muscular deficits that result in asymmetric muscular tone resulting in spinal curvature
congenital bony: an underlying bony abnormality of the vertebra that results in a relatively fixed spinal curve
tumor or treatment: this is a bit of a catch-all for the remainder of causes, most of which relate to an adjacent tumor, or previous treatment, e.g. radiotherapy or cardiac surgery
Causes
-
segmentation and fusion abnormalities (e.g. hemivertebrae)
-
tumors
bone: osteoid osteoma, osteoblastoma, metastases, neurofibromas in neurofibromatosis type I
soft tissues: meningioma, neurofibroma, astrocytoma, ependymoma
infection resulting in bony abnormalities (e.g. pyogenic osteomyelitis, tuberculous spondylitis)
Associations
pars interarticularis defect (spondylolysis): ~5% in idiopathic scoliosis 9
Radiographic features
Assessment and monitoring of scoliosis is primarily achieved with long-spine plain films. CT and MRI have roles to play in assessing for underlying abnormalities as well as, in certain situations, preoperative planning.
Plain radiograph
Scoliosis imaging will vary depending on patient and treatment particulars but will generally include a long (full spine) PA with or without lateral projections. Additionally, lateral bending films can be obtained to help determine structural vs non-structural curves 1.
Examination of spinal films should be systematic, and the following features should be assessed and commented upon 1:
presence of structural osseous abnormalities
major and minor curves
apex
end vertebrae
neutral vertebrae
stable vertebra
Structural osseous abnormalities
The presence of vertebral body wedging, segmentation abnormalities (such as hemivertebrae), spina bifida, or destructive lesions should be sought.
Sagittal and coronal balance
Sagittal balance and coronal balance refer to the overall alignment of the C7 vertebra with respect to the S1 vertebra. They require standing full spine films for assessment.
Lateral flexion views
Lateral flexion views, often with a bolster, are designed to determine how fixed a curve is. If a curve cannot be straightened to below a Cobb angle of 25° it is considered structural, otherwise, it is a non-structural compensatory minor curve 1.
Note: In some centers, scoliosis radiographs are displayed laterally (left to right) flipped to all other imaging to replicate what the clinician views when standing behind the patient who is facing away. Care must be taken to examine side markers.
Treatment and prognosis
Management depends on the magnitude of the curve(s), their rate of progression and (in a child) whether they are still growing. In general, treatment can be broken down into three main groups:
exercise
bracing (moderate and still growing)
surgical intervention (severe: over 50 degrees) 6
History and etymology
The Cobb angle was first described in 1948 by American orthopedic surgeon John R Cobb (1903-1967) 7.
Unable to process the form. Check for errors and try again.