If the physical examination suggests spinal deformity standing PA (posterior-anterior) and lateral whole spine radiographs will be required. Most xrays are taken AP (Anterior to posterior) in order to reduce the magnification of the image.

This patient has an adolescent idiopathic scoliosis with thoracolumbar curves measuring between 38 and 40 degrees - credit Dr. L. Davidson

Why are scoliosis x-rays routinely taken in the PA direction? This relates to the demographics of this disorder discussed in the previous section.

Check answer

Scoliosis is quantified by measuring the size of the curve at each visit. This is normally done using a technique called the "Cobb angle". Using a standing, full lenghth PA x-ray, the vertebrae at each end of the curve (or curves) are identified. These are described as the vertebrae the "most tipped" away from the normal horizontal orientation. Lines are drawn along the endplates of these vertebrae and the intersection of two further lines, draw perpendicular to the vertebral endplates is measured.

The scoliosis angle is interpreted in light of growth remaining which is estimated using radiologic criteria (often a hand and wrist x-ray that can be compared to a bone age atlas).

1. Children with a small curve (10o) and little growth remaining are unlikely to have long term problems.
2. Children with a large curve (20o or more) and much growth remaining should be followed carefully as they are likely to progress their curve and have long term concerns.
3. In adults, scoliotic curves less than 40o are unlikely to progress.
4. Larger curves (>40o) will progress insidiously and create problems in mid-life.

Curve progression can be halted is some cases by application of a custom-made brace worn 12-23 hours/day. If this is unsuccessful, surgical correction and fusion of the spine is indicated.