Spinopelvic Imbalance Is Associated With Increased Sway in the Center of Gravity: Validation of the "Cone of Economy" Concept in Healthy Subjects.

Cross-sectional study. To investigate the effects of pelvic compensation on standing balance in healthy volunteers. The 180 healthy volunteers were recruited at a basic health checkup. The inclusion criteria were: 1) age ≥ 65 years, 2) underwent a whole spine radiograph and stabilometry, 3) well-balanced standing posture with a sagittal vertical axis <50 mm, and 4) a visual analog scale of lower back pain of <20 mm. Based on the pelvic incidence (PI) and lumbar lordosis (LL) mismatch, subjects were divided into harmonious (PI-LL ≤ 10°) or unharmonious (PI-LL > 10°) groups. Participants in the unharmonious group were significantly older compared with the harmonious group (70.2 ± 4.4 vs. 72.0 ± 4.6 years, Healthy elderly subjects with poor spinopelvic harmony had relatively unstable standing balance. The "cone of economy" was demonstrated, showing that unharmonious spinopelvic balance had a non-economic effect on standing.