Spine-pelvis index: a novel ratio to predict spinal growth in adolescent idiopathic scoliosis patients

Methods A total of 75 female patients with AIS, 86 healthy agematched girls and 40 age-matched patients with CS due to excrescent hemivertebra were included into this study. Long-cassette standing coronal radiographs of the spine and pelvis were obtained from the subjects in fiston-clavicle position. The radiographic parameters were measured including length of spine (LOS), height of spine (HOS), length of thoracic vertebrae (LOT), height of thoracic vertebrae (HOT), width of pelvis (WOP), height of pelvis (HOP) and width of thorax (WOT). SPI was defined as the ratio between length of the spine and height of the spine, namely LOS/HOP. Four age cohorts (10~11 yrs, 12~13 yrs, 14~15 yrs and 16~18 yrs) were determined in AIS patients and normal controls. In addition, the theoretical value of LOS in CS patients was calculated according to the normal SPI measured in healthy controls.