Age-related variations in global spinal alignment and sagittal balance in asymptomatic Japanese adults

Objectives: The global spinal sagittal alignment varies widely among healthy individuals as it is affected by not only race, but also aging. We investigated age-related changes in the spinal alignment in asymptomatic Japanese individuals. Methods: The subjects comprised 220 individuals without any spine-related neurological symptoms or treatment history thereof who visited our outpatient clinic. Lateral radiographs of the whole spine were taken for all subjects in the standing position. Based on the images obtained, spino-pelvic parameters were calculated using Jackson's method so as to analyze any correlations with age. Results: TIA, TK, and C2-C7A were found to markedly increase with age from late middle age (P < 0.05). No correlation with aging was found for lumbosacral parameters or sagittal balance (P > 0.05). However, there were 22 subjects (10%) with C7SVA > 50 mm, with those aged 70 years or older accounting for half of this subpopulation. Sagittal balance tended to be retained even in elderly subjects if lumbosacral lordosis was large enough to compensate for thoracic kyphosis. A very strong correlation was found between the L1 slope and whole-spine sagittal balance (P < 0.0001, r = -0.497). Conclusions: Increases in cervicothoracic curvature occurring along with thoracic deformation underlie age-related changes in the spine. In contrast, the lumbosacral spine compensates in such a manner so as to maintain the sagittal balance. The whole-spine sagittal balance can deteriorate if the compensatory changes in the lumbosacral spine are insufficient. The L1 slope is a central parameter that defines the whole-spine sagittal balance.