Cause of idiopathic scoliosis.

Idiopathic scoliosis is a three-dimensional deformity of the spine with lateral curvature combined with vertebral rotation. The primary lesion, however, lies in the median sagittal plane, taking the form of a lordosis. It was first described by Hippocrates, and the term “scoliosis” was first used by Galen (AD 131–201). Although the clinical manifestations of scoliosis have been well described, no one has been able to determine the cause and pathogenesis. Throughout the 18th and 19th centuries, scoliosis was believed to be caused by postural positioning of the body. Historically, idiopathic scoliosis has been attributed to a wide variety of conditions ranging from poor posture to poor nutrition. Nutritional deficiency was proposed as a cause in the beginning of this century, and most spinal curves were thought to be secondary to rickets. Brunk, however, showed that the curves identified as rickets presumably caused by vitamin D deficiency never became severe and actually were reversible by treatment. Recently, the search for the cause of idiopathic scoliosis has focused on the structural elements of the spine, spinal musculature, collagenous structures, endocrine system, central nervous system, and genetics. Of all these studies, none has shown convincing evidence of the cause of idiopathic scoliosis. Results of experiments on various animal models and clinical studies have indicated possible anatomic or functional influences in the cause of idiopathic scoliosis, but many of them may be epiphenomena rather than causes. More recently, Kindsfater et al have reported that the level of platelet calmodulin in skeletally immature patients with a progressive spine curve is significantly higher than in those with a stable curve. Machida et al found significantly decreased nighttime melatonin levels in adolescents with progressive curves, whereas those with stable curves had a level that is normal for adolescents There is a strong interaction of melatonin with calmodulin. Other researchers have suggested a genetic component in idiopathic scoliosis because of the similarity of curve pattern in twins who both have scoliosis. This is a review of various causative factors thus far proposed for idiopathic scoliosis and a discussion of where research is heading to determine the cause of idiopathic scoliosis.