Age- and Gender-based Global Sagittal Spinal Alignment in Asymptomatic Adult Volunteers: Results of the Multiethnic Alignment Normative Study (MEANS)

Abstract

Study Design. Multicenter Cohort. Objective. Assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers stratified by age and gender. Summary of Background Data. Our understanding of ideal sagittal alignment is still evolving. The Multiethnic Alignment Normative Study (MEANS) investigated skeletal alignment of the largest multiethnic cohort of asymptomatic adult volunteers. We aim to assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers stratified by age and gender. Materials and Methods. Asymptomatic volunteers between the ages of 18-80 years were enrolled prospectively and then analyzed retrospectively from six different centers. Volunteers included reported no significant neck or back pain, 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. Thoracic kyphosis (TK) from T4 to T12 showed a mean of 37.4 ± 10.9°. The average L1-S1 lumbar lordosis (LL) was −57.4 ± 11.3°. LL did not show significant differences across the five age groups. TK showed a significant difference based on age (P < 0.0001). Sagittal vertical axis increased across age groups from −14.2 mm in young adults to 17.0 mm in patients > 64. Similar trend was seen for T1 pelvic angle with a mean of 5.0°in young adults and 13.7°in those older than age 64. Knee flexion increased across age groups without a significant change in odontoid-knee distance which is a surrogate for the center of the head aligned over the knees. Conclusions. In asymptomatic volunteers, sagittal alignment parameters showed a slow and steady change across age groups exemplified by an increase in TK. However, LL did not show a significant decrease across age groups. Volunteers used compensatory mechanisms such as slight pelvis retroversion, knee flexion, and neck extension to maintain an aligned sagittal posture with their head centered over their knees (odontoid-knee).

Personalized Medicine in Orthopaedic Surgery: The Case of Spine Surgery

“…Roussouly et al 2 further expanded this concept to describe variations in normative alignment based on the reciprocal relationship between each individual's pelvic incidence, sacral slope, and pelvic tilt while more recently the Multiethnic Alignment Normative Study demonstrated that thoracic kyphosis progresses slowly with age, whereas lumbar lordosis remains stable in asymptomatic patients. 9 Additional studies have demonstrated that deformity and spinal malalignment are directly associated with quality-of-life outcomes and failure to address these parameters may increase the risk of mechanical complications after spine surgery. 10 Given the importance of these measurements on long-term outcomes, the rationale for tailoring treatment based on each individual's alignment goals becomes evident.…”