Age and Gender Based Spinopelvic and Regional Spinal Alignment in Asymptomatic Adult Volunteers: Results of the Multi-Ethnic Alignment Normative Study (MEANS)

Background. Spinal alignment can have a significant impact on a patient's overall quality of life. Predicting the ideal sagittal spinal alignment of a specific individual is still a difficult task. The Multi-Ethnic Alignment Normative Study (MEANS) investigated skeletal alignment, including the spine and lower extremities, of the largest multi-ethnic cohort of asymptomatic adult volunteers. In this analysis, the authors aim to assess normative values of spinopelvic parameters and the regional cervical, thoracic, and lumbar spinal alignment in asymptomatic volunteers stratified by age and sex. Materials and Methods. Asymptomatic volunteers between ages 18 and 80 years were enrolled prospectively from centers in France, Japan, Singapore, Tunisia, and the United States. Volunteers included reported no significant neck or back pain (Visual Analog Scale <= 2), nor any known spinal disorder(s). All volunteers underwent a standing full-body or full-spine low-dose stereoradiograph. Results. MEANS consisted of 468 volunteers with a mean age of 40.4 +/- 14.8 years. Mean cervical lordosis from C2 to C7 was -0.4 +/- 12.7 degrees. The T1-slope averaged 23.0 +/- 7.9 degrees and showed strong correlation (r=0.87) with the C7-slope mean of 19.8 +/- 8.6 degrees. Thoracic kyphosis (TK) from T4 to T12 showed a mean of 37.4 +/- 10.9 degrees. Average L1-S1 lumbar lordosis (LL) was -57.4 +/- 11.3 degrees. The mean pelvic incidence (PI) measured 52.0 +/- 10.7 degrees and pelvic tilt was 12.5 +/- 7.3 degrees. Sacral slope averaged 39.5 +/- 8.2 degrees. The average PI-LL was -5.4 +/- 10.7 degrees. Approximately 60% of volunteers met the PI-LL criteria within +/- 10 degrees, 8.3% were >= 10 degrees, while 32.1% were <=-10 degrees. LL showed moderate correlation with PI (r=0.53) and TK (r=0.50), while there was no correlation between TK and PI. Multiple linear regression including PI, TK, and age resulted in the following equation LL=14.6+0.57 (PI)+0.57 (TK)-0.2 (age) (r=0.75). Conclusions. LL did not change with increasing age in asymptomatic volunteers. However, TK did increase with age leading to an increase in T1-slope and a compensatory increase in cervical lordosis. TK did not correlate with PI and was an independent variable in the prediction of LL.