It was previously postulated that the IV disc wedging is a significant progressive factor for mild IS curves. The present report introduces an innovative comprehensive model of IS curves progression based on intervertebral disc (IV) diurnal variation and the subsequent patho-biomechanics of the deforming “three joint complex”, where vertebral growth occurs.

Throughout day and night, due to sustained loading and unloading, the scoliotic wedged IV disc expels fluid and imbibes it more convex-wise. The convex side of the IV sustains a greater amount of cyclic expansion than the concave side. Consequently the imposed, convex-wise, asymmetrical concentrated cyclical loads to the adjacent immature vertebral end plates and posterior elements of the spine lead to asymmetrical vertebral growth. More specifically the loading on the two facet-joins asymmetrically increases during the day, as the wedged IV space narrows due to expelled water and it asymmetrically decreases during the night, as the IV space swells due to imbibed water.

This 24 hour period cyclic asymmetric loading leads both to asymmetric growth of the end plates and wedging of the vertebral bodies, and to similarly asymmetric growth of the pedicles and arches posteriorly as an effect of Hüeter-Volkmann law. This model explains the well described anatomical findings of the more elongated pedicles and the larger facet joints in the convex side than in the concave in scoliotic spines

The aim of school screening is to identify most or all the individuals with unrecognized idiopathic scoliosis (IS) at an early stage when a less invasive treatment is more effective. The present study summarises the contribution of school screening in research of IS epidemiology, natural history and aetiology. In addition, school screening is a unique tool for research of IS in humans, as in most published articles, all aetiopathogenetic factors are studied in animals and not in humans.

Such contribution is beyond the original aim of school screening but is very important to expand our knowledge and adequately understand the pathogenesis of IS. The role of biological factors such as the menarche, the lateralization of the brain, the handedness, the thoracic cage, the intervertebral disc, the melatonin secretion, as well as the role of environmental factors such as the light and the impact of the geographical latitude in IS prevalence were studied in children referred from school screening. The present study provides evidence to support that school screening programs should be continued not only for early detection of IS but also as a basis for epidemiological surveys until we learn much more about the aetiology of IS

Melatonin’s concentration is high in early childhood and declines gradually thereafter. In the elderly serum melatonin levels are very low. Melatonin, the “light of night”, among other functions is involved in human sexual maturation and in osteogenesis.

Hormesis is the response of cells or organisms to an exogenous (eg drug or toxin) or intrinsic factors (eg hormone), where the factor induces stimulatory or beneficial effects at low doses and inhibitory or adverse effects at high doses [bimodal dose-response] or vice versa.

At the age around 10 years, when idiopathic scoliosis may appear, the circulating melatonin level is about 120 pg/ml – positive hormesis for menses – and menarche appears. Melatonin deficiency may result in a delay of the age at menarche and consequently the girl is susceptible to scoliosis. In these terms melatonin could be certainly involved in the scoliosis pathogenesis. Around the age of 45 years when the circulating melatonin levels are about 20 pg/ml – negative hormesis for menses, menopause starts and the woman has an increased risk for osteoporosis and fractures.

It is documented the bone-protecting effect of melatonin in ovariectomized rats which can depend in part on the free radical scavenging properties of melatonin. Additionally, melatonin may impair development of osteopenia associated with senescence by improving non-rapid eye movement sleep and restoring GH secretion. Whether modulation of melatonin blood levels can be used as a novel mode of therapy for scoliosis and augmenting bone mass in diseases deserves to be studied