Abstract
Since the first pathography of Idiopathic Scoliosis (IS) and Scheuermann’s disease (SD) clinicians consider these two pathologies as separate nosological entities. The reason for this is different clinical implications of diseases. SD is known to be more common in boys, while IS is a sad privilege of girls. Kyphotic spinal deformity is typical for patients with Scheuermann’s disease while scoliotic one for patients with idiopathic scoliosis. Schmorl’s nodes are found more frequently in SD. Both deformities are attributed to the growth asymmetry, anterior growth plates are affected in SD and lateral ones – in IS. Despite different clinical presentations, these two nosologies have the same pathogenetic mechanism and semiology.
To our regret, there are no reports on comparative morphological and biochemical investigations of SD and IS. Long-term studies have given rise to the question of a single nature of scoliotic and kyphotic spine deformities.
Material and methods: Clinical and genetic examination with segregational analysis of pedigrees was performed in 350 families with IS and in 95 families with SD. Structural components of the spine obtained from IS and SD patients operated in our Institute were studied with morphological and biochemical techniques.
The potency for synthesis and structural organization of chondroblasts isolated from vertebral body growth plates of patients with IS and SD were subjects of morphological, biochemical, and ultrastructural analyses. Qualitative and quantitative composition of growth plates was investigated in culture mediums.
Results: Clinical and genetic examination of families with IS and SD have shown that both pathologies are inherited both from maternal and paternal lines. Families presented combinations of these pathologies. Segregational analysis of IS and SD pedigrees has revealed major gene dependence of both pathologies inherited by autosomal-dominant type with incomplete penetrancy genotypes according to gender and age. In experimental animal model of genetically dependent spine deformity there were cubs either with scoliosis or with kyphosis in one litter. The target organ for pathologies discussed is growth plate and secondary disorders of vertebral body and disc structure.
Morpho-histochemical study of the spine structural elements has revealed the same changes in patients with IS and patients with SD:
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Disturbance of structural and chondral organization of cells and matrix in vertebral body growth plate.
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Decrease of chondroitin sulfate content and increase of keratan sulfate content.
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Lower response to oxidation-reduction enzymes in cytoplasm of chondroblasts.
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Change of the ultrastructural organization of cells: Golgi complex with flat vacuoles and enlarged cisterns of endoplasmic reticulum.
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Extracellular matrix with fragmented collagen fibrils and small fragments of proteoglycans.
The changes observed in cultural mediums and in cultivated chondroblasts isolated from vertebral growth plates were similar for patients with IS and patients with SD. Some clinical differences of pathologies do not contradict the basic idea. The predominant involvement of thoracic spine and high penentrancy in boys is associated with concurrence of growth peak and thoracic spine development. The absence of vertebral body torsion in SD is associated with ventral vertebrae involvement and kyphosis development, which prevent torsion changes. Different localization of morphological changes – in ventral growth plates in SD and in lateral ones in IS – is attributed to independent development of each spine primordium. Different genes are expressed in the course of formation of different vertebral body zones. Depending on the mutant gene expression which regulates either lateral or ventral zone of vertebral body, either Idiopathic Scoliosis or Scheuermann’s disease develops. Thus, the fact of existence of the major gene responsible for occurrence of these pathologies allows to conclude that a pathogenetic mechanism of spine deformity formation is the mutation of gene programming growth plate modification in ventral zones in Scheuermann’s disease and in lateral ones in Idiopathic Scoliosis.
Correspondence should be addressed to Jeremy C T Fairbank at The Nuffield Orthopaedic Centre, Windmill Road, Headington, Oxford OX7 7LD, UK
