Analysis of Anterior Trunk Symmetry Index (ATSI) in healthy school children based on 2D digital photography: normal limits for age 7-10 years

Methods The study comprised 421 school children, both sexes, aged 7-10 years, with no clinical evidence of scoliosis (Angle of Trunk Rotation <5o). One frontal photograph of anterior trunk in spontaneous standing position was taken with a digital camera in standardized manner. The semi-automatic software for calculation of photogrammetric parameters was developed in collaboration with an IT specialist. The photographs were analyzed to obtain a quantitative assessment of the ATSI parameter. The intra-observer error was calculated by the first author by measuring the pictures of 14 children three times, selected randomly, at the interval of at least two days. The inter-observer error was calculated by one surgeon and two experienced physiotherapists by measuring the pictures of 60 children, selected randomly. The normal upper value limit was calculated as mean + 2SD. Results The mean ATSI value for 421 children was 24.3. ±12.7 (girls 24.4.±12.1, boys 24.0.±13.5). The ATSI values for each age group were: (1) 7-year-old children (N=117): 26.0 ±12.9 (girls 25.9 ±12.5, boys 26.2 ±13.4); (2) 8-yearold children (N=85) 23.3 ±13.7 (girls 23.0 ±12.2, boys 23.7 ±16.1); (3) 9-year-old children (N=109) 24.5 ±12.7 (girls 23.9 ±11.9, boys 26.1 ±14.1); and (4) 10-year-old children (N=110) 22.9 ±11.7 (girls 24.5 ±11.6, boys 21.8 ±11.5). For all age groups, the mean ATSI for boys did not differ significantly from the mean ATSI for girls (P>0.05). For both boys and girls, the mean ATSI did not differ among the four age groups (P>0.05). The intra-observer error was 1.07. The inter-observer error for the three observers was 4.06. The upper value limit was: (1) for 7-year-old children: girls=50.9 and boys=53.0; (2) for 8-year-old children: girls=47.4 and boys=55.9; (3) for 9-year-old children: girls=49.9 and boys=47.7; and (4) for 10-year-old children: girls=47.7 and boys=44.8.