A longitudinal study of congruent sagittal spinal alignment in an adult cohort

Study Design. A 10+-year longitudinal study of 100 adult volunteers. Objectives. To identify congruent lumbar lordosis in association with other sagittal spinopelvic parameters. Summary of Background Data. The aging spine poses difficult problems in determining appropriate lumbar lordosis. The concept of congruent spinal alignment is preferred over that of normal spinal alignment, yet the definition of sagittal spinal congruity in elderly population has not been well documented. Methods. A population-based recruitment of adult volunteers and follow-up of 10 + years was conducted. A total of 100 healthy volunteers with baseline age of 50 + years were subjected to standing entire spine radiographs. Radiologic parameters included lumbar lordosis, sacral inclination, sagittal spinal balance, and other sagittal alignments. Results. Average age of the subjects was 62.0 years at baseline and 73.9 years at follow-up. Lumbar lordosis with <5° change during observation was defined as stable lumbar lordosis ( n = 34). Regression analyses of the baseline parameters revealed that sacral inclination was the sole predictor of stable lumbar lordosis ( lumbar lordosis = 0.8 * sacral inclination, r = 0.94, P < 0.0001). Baseline lumbopelvic congruity, determined as 0.7 less than or equal to lumbar lordosis/sacral inclination less than or equal to 0.9, was associated with minimum alterations in sagittal spinal alignment, whereas subjects with incongruent lumbopelvic relationships were predisposed to developing kyphosis and spinal imbalance. Conclusions. Our study substantiates previous results showing that the strongest determinant of lumbar lordosis is sacral alignment. Appropriate lumbar lordosis was estimated to be 80% of sacral inclination using standing radiographs, and the proposed lumbopelvic congruity could measure stability in sagittal spinal alignment. This study provides practical data for the assessment of sagittal spinal alignment in the aging spine.