Development of Trunk Asymmetry in a Cohort of Children Ages 11 to 22 Years

STUDY DESIGN: A cohort study with a follow-up period of 11 years. OBJECTIVES: To study the growth of the spine with a focus on the development of trunk asymmetry and scoliosis. SUMMARY OF BACKGROUND DATA: Trunk asymmetry, a common phenomenon at adolescence, can be considered the clinical expression of scoliosis. The importance of the pubertal growth spurt has been stressed in the natural history of scoliosis. However, no cohort studies have focused on the ascending and descending phase of the spine's peak growth and the development of trunk asymmetry. METHODS: The cohort consisted of all the fourth-grade school children in the Western school district of Helsinki, Finland, in the spring of 1986. These 1060 children (515 girls and 545 boys), from the average age of 11 to 14 years, were invited to undergo annual examinations. The 855 children (80.7%) who had participated in the study at the age of 14 years were invited to a reexamination at the age of 22 years. This invitation was accepted by 430 (208 women and 222 men; 54%) of those invited. The forward bending test, the spinal pantography, and the anthropometric measurements were carried out by the same author (M.N.) throughout this study. RESULTS: At 22 years of age, 30% of the adults were found to be symmetric, with a hump less than 4 mm in the forward bending test, whereas 51% had a hump of 4 to 9 mm, and 19% had a hump 10 mm or larger (major asymmetry). The directional asymmetry of trunk surface, a skew to the right at the thoracic level and to the left at the lumbar level at puberty, remained constant at adult age. The prevalence of major trunk asymmetry at adult age was the same in both women and men, in contrast to the female predominance at puberty in this cohort. There were close correlations in the degrees of thoracic and lumbar asymmetry between puberty and adult ages. CONCLUSIONS: The shape of the back develops mainly during the pubertal growth spurt at ages 12 to 14 years in girls and boys. Trunk asymmetry (and mild scoliosis) seems as prevalent in young adult women as in men, although at puberty idiopathic scoliosis was twice as prevalent among girls as among boys in this cohort.