Skeletal growth velocity of adolescent idiopathic scoliosis: abnormal in spine but normal in lower limbs

BACKGROUND: Abnormal spinal overgrowth has been identified in patients with adolescent idiopathic scoliosis (AIS), which may be attributed to a secondary change. However, growth velocity in adolescents with different maturity statuses, and the final length of the lower extremities were not investigated in patients with AIS. Here, we compared the peak height velocity (PHV) time point of the lower limbs between AIS and healthy adolescents and analyzed whether abnormal growth of the lower limbs exists in patients with AIS. METHODS: Female AIS patients with a thoracic Cobb angle of 20° to 60° were enrolled in the current study. The major Cobb angle, length of the spine (LOS), length of the lower limbs (LLL), and height of the pelvis (HOP) were measured. In addition, RatioSL was defined as LOS/LLL; RatioSP was defined as LOS/HOP; and RatioPL was defined as HOP/LLL. All patients and healthy controls were classified into three groups according to skeleton maturity status: pre-PHV, defined as Risser 0, and open triradiate cartilage (TC); during-PHV (Risser 0, and closed TC); and post-PHV (Risser ranging from 1 to 5). RESULTS: RatioSL and RatioSP were significantly higher in scoliosis patients at Risser ≥4 compared to healthy controls (all, P<0.05). However, RatioPL was similar between patients with AIS and healthy controls in both the Risser 0 and Risser ≥4 groups. The change in ratio from pre-PHV to post-PHV showed similar trends between patients with AIS and healthy controls; both RatioSL and RatioPL were significantly lower in the during-PHV group (all, P<0.05). CONCLUSIONS: The final length of the lower extremities was similar between groups, while the peak growth of the lower extremities was earlier than that of pelvis and spine in both patients with AIS and healthy adolescents, indicating that lower limb growth pattern was not altered in AIS patients.