Scoliosis and developmental theory: adolescent idiopathic scoliosis.

Abstract

Statistical analysis of maturity and asymmetry criteria in adolescent idiopathic scoliosis. To explore the hypothesis that scoliosis is a manifestation of developmental destabilization under physiologic stress. Advances in genetics and theoretical biology have broadened the understanding of morphogenesis and the controlling mechanisms for the development of the adult form. The morphologic genome can be viewed as a cybernetic control system, and the homeobox genes can be viewed as the master controls for the specific subroutines. Deformity will occur from a faulty "program" or a disturbance in the running of that program. An early and subtle indication of such an occurrence is failure of bilateral symmetry. An analysis of variance in Cobb angle, age at diagnosis, and apical site in 327 girls with spinal curves 5 degrees or greater according to prospectively maintained scoliosis screening records was performed. Dermatoglyphics were compared in 114 female control individuals and 164 female patients with adolescent idiopathic scoliosis (minimum Cobb angle, 10 degrees), and then by subdivision into school screening (n = 86) and general clinic referrals (n = 78). Girls from the screening program (from the years 1979-1990) had statistically significant associations between age and apical vertebra, suggesting an age-deformity relationship independent of maturation and growth spurt. Girls with adolescent idiopathic scoliosis from a later cohort, both screened and unscreened, had increased directional asymmetry, as previously reported. There was a statistically significant increase in fluctuating asymmetry in general clinic referrals when compared with school screening referrals. Developmental instability can explain adolescent idiopathic scoliosis as part of wider developmental theory without the necessity of a disease process in the etiology. The differences between screening and general clinic referrals suggest the need for natural history studies, and treatment protocols also should consider the provenance of the individuals described.