The growth of different body length dimensions is not predictive for the peak growth velocity of sitting height in the individual child

The aim of this study was to determine whether the differences in timing of the peak growth velocity (PGV) between sitting height, total body height, subischial leg length, and foot length can be used to predict whether the individual patient with adolescent idiopathic scoliosis is before or past his or her PGV of sitting height. Furthermore, ratios of growth of different body parts were considered in order to determine their value in prediction of the PGV of sitting height in the individual patient. Ages of the PGV were determined for sitting height (n = 360), total body height (n = 432), subischial leg length (n = 357), and foot length (n = 263), and compared for the whole group and for the individual child in particular. Furthermore, the ages of the highest and lowest ratios between the body length dimensions were determined and compared to the age of the PGV of sitting height. The mean ages of the highest and lowest ratios were significantly different from the mean age of the PGV of sitting height in 3 out of 12 ratios in girls and 8 out of 12 ratios in boys. The variation over children was large and the ratios were too small, leading to a too large influence of measurement errors. The mean ages of the PGV all differed significantly from the mean age of the PGV of sitting height. However, the variation over individual children of the age differences in PGV between body dimensions was large, and the differences in timing of the PGV were not useful to predict whether the individual child is before or past his or her PGV of sitting height.