Background. Although there are frequent studies about normal range of thoracic kyphosis, there is still a controversy about the exact values of this curve. In nine reported studies on 10 to 20 years of age boys, the value ranged from 25.1° to 53.3°. Objective for the Study. The aim of the present research was investigation of normal ranges of thoracic kyphosis in school children in Kermanshah, western Iran. Methods. 582 male students aged 13 to 18 years old using cluster random sampling were recruited from schools in Kermanshah city, 97 students for each age. Thoracic curves were measured using the flexicurve method. Results. Mean thoracic kyphosis for whole population was 35.49° SD 7.83 and plus or minus two standard deviations ranged from 19.83° to 51.15°. It increased gradually from 13 to 16 and then there was a little decrease to 18 years. Mean values for each age (13–16) were 13 (34.41 SD 7.47°), 14 (34.86 SD 8.29°), 15 (35.79 SD 7.93°), 16 (36.49 SD 7.85°), 17 (35.84 SD 8.33°), and 18 (35.55 SD 7.07°). Conclusions. Our results are in agreement with previous reports and can be used as normal values for local and regional purposes. 1. Introduction The thoracic angle is the primary curve of the vertebral column which is comprised of 12 vertebrae [1]. The thoracic kyphosis angle increases with age and the increase is greater in females than in males [2, 3]. Hyperkyphosis or increase in thoracic curve greater than normal range is one of prevalent spinal disorders. Biomechanical data suggest that an increase in the thoracic kyphosis may be associated with significantly higher spinal loads and trunk muscle force in upright stance and this might accelerate degenerative process which in turn leads to further spinal dysfunction and pain [4]. An increase in thoracic kyphosis has also been associated with diminished physical function [5], impairment of respiratory function [6, 7], an increase in cervical pain [8, 9], headaches [10], and shoulder discomforts such as subacromial pain syndrome [11, 12]. In spite of frequent studies on normal range of thoracic angle, there is a controversy about the magnitude of this curve. For example in Willner and Johnson [13] study the least pronounced kyphosis was seen at the age of 10–12 years and mean kyphosis angle in 8 and 16 years was 35° and 44°, respectively [13]. Propst Proctor and Bleck [14] in a study on children aged from 2 to 20 years old reported an angle of 27° (range of 21–33°) as normal. The magnitude of thoracic kyphosis in the study of Voutsinas and MacEwen [15] averaged 38.l° in white boys and 34.3° in
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