Variation of Global Sagittal Alignment Parameters According to Gender, Pelvic Incidence, and Age

Abstract

Study Design: Retrospective cross-sectional study. Objective: The aim was to describe existing global sagittal alignment parameters across ages and to analyze differences according to gender and pelvic incidence (PI). Summary of Background Data: Variability with age has been reported. It remains unclear how gender and spinopelvic morphology could additionally influence global alignment parameters. Materials and Methods: Radiographs of 2599 individuals (5–93 y) were analyzed. Translation parameters were: Sagittal Vertical Axis (SVA)-C7, SVA-C2, SVA-Center Acoustic Meatus (CAM), C7/Sacrofemoral Distance (SFD) ratio. Inclination parameters were: C7-Vertical Tilt (VT), T1-VT and T9-VT, Odontoid-Hip Axis (OD-HA), OD-CAM. Pelvic compensation parameters were: T1-Pelvic Angle (TPA), Global Tilt (GT), Spino-Sacral Angle (SSA). Global sagittal alignment (GSA) was considered among formulae. The distribution of parameters was analyzed using a Bayesian inference. Correlations with spinopelvic parameters were investigated. Results: SVA-C7, SVA-C2, SVA-CAM were larger in males and high PI, and increased significantly after 50 years (Pr>0.9999). C7/SFD decreased during growth and was larger in low PI (Pr=0.951). There was no correlation with spinopelvic parameters. Age-related variations of inclination parameters were nonsignificant. T1-VT and T9-VT increased with PI and were significantly larger in high PI (Pr>0.95). C7-VT was significantly larger in low PI (Pr>0.9999). OD-HA and OD-CAM were constant and increased after 80 years. TPA and GT increased with PI (Pr>0.9999) and age after 35 years (Pr>0.9999). SSA decreased nonsignificantly after 50 years. TPA correlated with PI (ρ=0.6130) and pelvic tilt (PT) (ρ=0.8375). GT correlated with PI (ρ=0.5961) and PT (ρ=0.8996). SSA correlated with sacral slope (ρ=0.9026). GSA was larger in high PI (Pr>0.9999) and increased after 35 years (Pr>0.9999). GSA correlated with PT (ρ=0.7732). Conclusion: Translation parameters increase with age, more prominently in males and high PI. Variations of inclination parameters are smaller. Pelvic compensation parameters and GSA increase with age and are closely related to PT and spinopelvic morphology. Level of Evidence: Level III.

Can Lumbopelvic Parameters Be Used to Predict Thoracic Kyphosis at all Ages? A National Cross-Sectional Study

“…Other parameters of the equation also vary over age: LL decreases and PT increases as degenerative changes occur in the lumbar spine, whereas PI also tends to increase in the elderly. [21][22][23] This reflects the typical modifications of sagittal parameters with age, as previously described. 19,[21][22][23][24][25] In a cohort of Japanese adults, average values of sagittal alignment parameters 24 were: 50°± 11 for LL, 54°± 11 for PI, 14°± 8 for PT, and 39°± 8 for SS.…”

“…[21][22][23] This reflects the typical modifications of sagittal parameters with age, as previously described. 19,[21][22][23][24][25] In a cohort of Japanese adults, average values of sagittal alignment parameters 24 were: 50°± 11 for LL, 54°± 11 for PI, 14°± 8 for PT, and 39°± 8 for SS. Our results were similar for SS, PI, PT, LL, whereas TK was higher in our cohort (45°±13 vs 36°± 10).…”

Sagittal Alignment in the Degenerative Lumbar Spine

“…Recent studies have furthered the understanding of a harmonious sagittal plane, reporting the mean segmental lordosis values based on PI 34,35 . Table I includes the mean segmental lordosis per PI category; these values were extrapolated from recent normative segmental lordosis publications 34,35 . The table provides a general reference for surgical planning; however, surgical planning should be personalized for each patient’s spinopelvic anatomy.…”

“…PI is thought to remain unchanged in adulthood, even with degeneration [31][32][33] . However, recent data revealed that PI actually may change over time via increased stress over the sacroiliac joints and subsequent remodeling of these joints and the sacral end plate, a process evident in patients with long fusions involving S1 as the lower instrumented vertebra 34,35 . Nevertheless, given the relative stability of PI compared with SS, LL is often evaluated relative to PI 25 .…”

“…The historical target was "as much lordosis as possible." This continued until several authors, including Schwab et al and Lafage et al, proposed matching PI to LL within 10°, which has been shown to improve outcomes even in surgical procedures for degenerative pathology 35,[40][41][42][43][44][45][46][47][48][49][50][51] . It has been suggested to correct LL to PI 1 10°if the PI is low and to PI 2 10°if the PI is high 52 .…”