• Yusuke Hori, Akira Matsumura, Takashi Namikawa, Minori Kato, Masayoshi Iwamae, and Hiroaki Nakamura.
• Department of Orthopaedic Surgery, Osaka City General Hospital, Osaka, Japan.
• World Neurosurg. 2021 May 1; 149: e309-e315.

BackgroundUnderstanding the natural history of the spinopelvic alignment in adolescent idiopathic scoliosis (AIS) is important in developing surgical strategies for patients with adult idiopathic lumbar scoliosis (AdLS). Because it is challenging to follow individuals without any treatments, we sought to estimate its natural history by comparing radiographic characteristics of patients with AIS and AdLS.MethodsWe included patients with Lenke 5 AIS and patients with AdLS who were diagnosed with Lenke 5 AIS in adolescence. The Cobb angle of the curve and spinopelvic parameters were measured by whole spine radiographs. The AdLS patients were divided into 2 groups according to age <50 years (AdLS<50) or ≥50 years (AdLS≥50). Radiographic parameters were compared among the AIS, AdLS<50, and AdLS≥50 groups. The relationship between age and each parameter was analyzed using nonlinear regression analysis.ResultsWe analyzed 40 patients with AIS (all female, mean age 16.8 ± 3.2 years) and 35 patients with AdLS (34 female and 1 male, mean age 55.4 ± 12.1 years). Thoracolumbar/lumbar curve and thoracolumbar kyphosis was significantly greater in the AdLS<50 group compared with the AIS group, without progression after age 50 years. Lumbar lordosis and pelvic tilt deteriorated linearly with age. AIS and AdLS<50 patients maintained sagittal balance, which deteriorated in AdLS≥50 patients.ConclusionsOur results may predict the following natural course of Lenke 5 AIS: (1) progression of scoliotic deformity of thoracolumbar/lumbar curve with increased thoracolumbar kyphosis; (2) subsequent lumbar hypolordosis followed by pelvic retroversion; and (3) sagittal imbalance after failure of compensation.Copyright © 2021. Published by Elsevier Inc.

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