Full-Body Analysis of Adult Spinal Deformity Patients' Age-Adjusted Alignment at 1 Year

Previous studies have built a foundation for understanding compensation in patients with adult spinal deformity (ASD) by using full-body stereographic assessments. These mechanisms, in relation to age-adjusted alignment targets, have yet to be studied fully. The aim of this study was to assess lower-limb compensatory mechanisms of patients failing to meet age-adjusted alignment goals. Patients with ASD ≥40 years with full body baseline and follow-up radiographs were included. Patients were stratified by age (40–65 years, >65 years) and spinopelvic correction. Lower-limb compensation parameters (pelvic shift, hip extension, knee flexion [KA], ankle flexion [AA], and global sagittal angle [GSA]) for patients who matched and failed to match age-adjusted alignment targets were compared with analysis of variance and t-test analysis. In total, 108 patients were included. At 1 year, AA increased with age in the “match” pelvic tilt (PT) and spinopelvic mismatch (PI-LL) cohorts (PT: AA, 5.6–7.8, P = 0.041; PI-LL: 4.9–8.8, P = 0.026). KA, AA, and GSA increased with age in the “match” sagittal vertical axis (SVA) cohort (KA: 3.8–13.1, P = 0.002; AA: 5.8–10.2, P = 0.008; GSA: 3.9–7.8, P < 0.001), as did KA and GSA in the “match” T1 pelvic angle group (KA: 1.8–8.7, P = 0.020; GSA: 2.6–5.7, P = 0.004). Greater compensation captured by KA and GSA was associated with age progression in the “match” SVA and T1 pelvic angle cohorts. In addition, older SVA, PT, and PI-LL “match” cohorts used increased AA, suggesting that ideal postoperative alignment of aged individuals with ASD involves increased compensation. •Levels of KA and GSA increased with age in the “match” cohorts of SVA and TPA.•The >65-year cohort exhibited greater levels of AA than the younger cohort.•The match cohorts of PI-LL exhibited similar levels of PS, SFA, KA, and GSA.•All subjects reaching their age-adjusted ideals used a similar degree of SFA.•Future research is needed to better understand compensation in the ASD population.