Thoracic Insufficiency Syndrome and Exotic Scoliosis

Abstract

Most spinal curves can be described as standard scoliosis and are due to adolescent idiopathic scoliosis. In patients with standard scoliosis, the thorax is usually spacious, having achieved most of its adult volume through growth, and has near normal vital capacity. Standard scoliosis is characterized on an anteroposterior radiograph by the level and degree of the curve and is treated by bracing or definitive spinal fusion to effect a decrease in the Cobb angle. Treatment has a negligible effect on thoracic growth or long-term pulmonary outcome. Exotic scoliosis describes an early-onset spinal deformity that is more complex in nature, often associated with a thorax that has been distorted by spinal lordosis and curve rotation, thus having a volume-depletion deformity as well as thoracic growth inhibition with indirect adverse effects on lung growth (Fig. 1). Exotic means “foreign,” “outlandish,” or “alien,” and the curves of exotic scoliosis are easily recognizable. In the coronal plane, this scoliosis is not only a “lateral curve” but, from a three-dimensional thoracic viewpoint, can be considered a lateral flexion contracture of the thorax with volume depletion on the concave side and often additional volume depletion on the convex side, in the transverse plane, from a windswept deformity of the thorax. Primary rib-cage abnormalities, such as absent or fused ribs, add further thoracic disability. The typical treatment approaches to spine deformity may be impractical for the treatment of exotic scoliosis because of potential spine and thoracic growth inhibition from early fusion or because of additional comorbidities (e.g., the bone stock may be insufficient or too osteopenic to hold the instrumentation, the patient may be too small for standard spinal implants, or the lung function may be so poor that the patient would not survive surgery). In addition, a spine fusion may be unable to address the three-dimensional …