Analysis of Posterior Trunk Symmetry Index (POTSI) in scoliosis. Part 1

A new indicator to assess trunk asymmetry in scoliosis patients is introduc ed. The medio-lateral length difference index at the axilla and the waist, and off balance index at C7 were defined as Frontal Asymmetry lndex (FAI-C7 , FAI-A, FAI-T). The height difference at the shoulder, the axilla and the waist were defined as Height Difference Index ( HDI-S, HDI-A, HDI-T). The t otal sum of these six indices was defined as Posterior Trunk Symmetry Index ( POTSI). The average intra-observer and inter-observer error of POTSI wer e 5.5 and 6.4 respectively. Slight trunk asymmetries were detected in norma l children, whereas POTSI were significantly larger in scoliosis patients t han those in normal children. This measurement of trunk asymmetry defined a s POTSI is valid for the clinical assessment of scoliosis and to evaluate o bjectively the effect of surgery on trunk deformity.