Abstract
Introduction
The sagittal plane is the primary driver of disability in patients with ASD and spinopelvic radiographic thresholds have been established for pelvic tilt (PT), pelvic incidence (PI), and lumbar lordosis mismatch (PI–LL), and C7 sagittal vertical axis (SVA) in which disability occurs based on an ODI of ≥ 40. However, the patients' age was not accounted for in determining these thresholds and ODI has been shown to vary with age. The objective was to determine new thresholds based on age.
Patients and Methods
This is a multicenter, prospective study of consecutive patients with ASD. Inclusion criteria included patients with ASD with the age > 18 years. Patients were stratified into the following age groups: ≤ 45, 46 to 64, 65 to 74, and ≥75 years. Multivariate linear regressions were conducted for baseline PT, PI-LL, and SVA with baseline ODI and age on all patients. On the basis of the previous studies, an ODI of 40 was used as the threshold for disability. Individual patient thresholds were calculated based on their age. The thresholds were averaged across the age groups.
Results
A total of 833 patients were included (396 operative and 437 nonoperative). Patients with only sagittal deformity for the age groups were the following: ≤ 45 (18.8%), 46 to 64 (19.4%), 65 to 74 (40.1%), and ≥ 75 (50%). Age alone significantly predicted ODI (r2 = 0.17, p < 0.0001). Regressions for PT (r2 = 0.27, p < 0.0001), PI-LL (r2 = 0.27, p < 0.0001, SVA (r2 = 0.32, p < 0.0001) including age were all predictive of ODI. Thresholds for the entire cohort were the following: PT = 21.9 ± 4.7 degrees, PI-LL = 11.6 ± 7 degrees, SVA = 6.7 ± 2.5 cm. Thresholds for the age groups were the following: PT (deg): ≤ 45 (15.3 ± 2.3), 46 to 64 (22.6 ± 1.5), 65 to 74 (26.2 ± 0.8), ≥ 75 (29.1 ± 0.8). PI-LL (deg): ≤ 45 (1.7 ± 3.5), 46 to 64 (12.5 ± 2.2), 65 to 74 (18 ± 1.2), ≥ 75 (22.4 ± 1.3). SVA (cm): ≤ 45 (3.3 ± 1.2), 46 to 64 (7.1 ± 0.8), 65 to 74(9.0 ± 0.4), and ≥ 75 (10.5 ± 0.4).
Conclusion
Spinopelvic radiographic thresholds correlated to moderate-to-severe regional low back disability increase as patients age. These results suggest that preoperative surgery planning and patient counseling should consider the patients' age. Further study of Schwab–SRS sagittal modifier correction goals for individual age groups is warranted.