Introduction

Although the association between osteoporosis and adolescent idiopathic scoliosis (AIS) has become widely accepted, the mechanism behind the development of osteoporosis and AIS remains unknown. To elucidate this relationship, we investigated the radiological and histological changes in a model of scoliosis in chickens, focusing on the cervical vertebrae that are not affected by scoliosis.

Objective: To clarify whether serum melatonin levels in adolescent idiopathic scoliosis correlate with curve progression, and whether the exogenous melatonin treatment is effective in patients with decreased levels of endogenous melatonin in adolescent idiopathic scoliosis.

Method: A total of 63 adolescents were studied; 38 with adolescent idiopathic scoliosis and 25 age matched control subjects. We divided the patients into stable (28 patients) and progressive (10 patients) groups based on the scoliotic curve measured radiographically at three to six month intervals. The level of melatonin was considered low if it fell below the mean – 2.0 standard deviation established in normal adolescents throughout the 24 hour period or nocturnal (0:00 – 6:00 hour) integrated concentration. Oral melatonin replacement (3mg / before bedding) was administered in patients with decreased endogenous melatonin. The patients with low melatonin were treated with a brace, melatonin or both combined. During melatonin treatment, the level of melatonin was measured yearly for a period ranging from three to six years.

Results: In all subjects the melatonin levels showed diurnal variations; low during the day and high at night. Of 38 patients with adolescent idiopathic scoliosis, 22 patients had normal melatonin and 16 had low melatonin. Of 22 patients with a normal melatonin, 10 of 15 treated with brace and 6 of 7 untreated patients had stable scoliosis, and the remaining six had a progressive scoliosis. Of 16 patients with low melatonin, eight of nine treated only with melatonin, and four of seven treated with melatonin and brace had stable scoliosis. The remaining four had a progressive course. Of the 10 patients who had progressive scoliosis in normal and low levels of melatonin, nine had greater than 40 degrees of curve at the initial examination.

Conclusion: These findings suggest that transient melatonin deficiency may be associated with deterioration of scoliosis and that melatonin level may serve as a useful predictor for progression of spine curvature in patients with idiopathic scoliosis. Also, the results of this study suggest a possible role of melatonin supplement in the prevention of progressive scoliosis especially in mild cases showing less than a 40° curve.

Supported by the Fondation Yves Cotrel, Institut de France.

We studied the possible role of melatonin deficiency in experimentally-induced scoliosis. A total of 90 chickens underwent pinealectomy on the third day after hatching: 30 were treated with serotonin, 30 with melatonin and 30 received no therapy (control group). Scoliosis developed in all the control group, in 22 of the serotonin group, and in only 6 of the melatonin group. The six melatonin-treated chickens with scoliosis had less severe spinal deformities than those in the serotonin-treated group. There were lower blood melatonin concentrations in chickens with scoliosis than in those without. Our findings suggest that melatonin deficiency contributes to the aetiology of this experimental scoliosis, probably by interfering with the normally symmetrical growth of the proprioceptive system involving the paraspinal muscles and the spine.