Vitality of global alignment following adult spinal deformity surgery to long-term improvement of patient-reported outcomes regardless of regional alignment.

Objective: The objective of this study was to discern whether patients who achieve a cranial sagittal vertical axis to the hip (CrSVA-H) < 2 cm at 2 years of follow-up, regardless of mismatch between pelvic incidence and lumbar lordosis (PI-LL), have a greater improvement in patient-reported outcome measures (PROMs).

Methods: This was a retrospective analysis of a prospectively collected single-center database of adult spinal deformity (ASD) patients who underwent corrective surgery with a minimum follow-up of 2 years. Patient demographics, perioperative data, radiographic parameters, and PROMs were collected at baseline and follow-up. Patients were placed into four cohorts: combined aligned (CA) (CrSVA-H < 2 cm, PI-LL < 10°), globally aligned (GA) (CrSVA-H < 2 cm, PI-LL ≥ 10°), regionally aligned (RA) (CrSVA-H ≥ 2 cm, PI-LL < 10°), and completely malaligned (CM) (CrSVA-H ≥ 2 cm, PI-LL ≥ 10°) at final follow-up.

Results: A total of 162 patients were included (71 CA, 58 GA, 11 RA, and 22 CM patients). The CA cohort was younger (mean [standard error of the mean]: 44.1 [2.2] vs 57.6 [1.8] vs 54.7 [3.1] years, p = 0.0003) and had a smaller PI-LL (1.6° [2.3°] vs 27.9° [2.4°] vs 25.0° [4.8°], p < 0.0001) than the GA and CM cohorts. The CrSVA-H differed significantly between the CA and CM cohorts (-1.5 [0.5] vs 4.1 [1.2] cm, p = 0.0012). There was no significant difference in BMI or total instrumented levels across all four cohorts (p > 0.05). The CA and GA cohorts had greater baseline PROMs when compared with the CM cohort, specifically in the SRS-22r total score (p = 0.0025 and p = 0.0244, respectively), self-image (p = 0.0032 and p = 0.0074, respectively), and satisfaction (p = 0.0313 and p = 0.0011, respectively) domains. Baseline Oswestry Disability Index (ODI) scores differed only between the CA and CM cohorts (32.2 [2.5] vs 41.1 [2.4], p = 0.0312). The CA and GA cohorts possessed greater PROMs by the final follow-up, including the aforementioned PROMs (p = 0.0016) and ODI scores (p = 0.0044) when compared with the CM cohort. The mixed-effects model of PROMs demonstrated that the CA and GA cohorts experienced a greater increase in patient-reported outcomes when compared with the CM cohort (p < 0.05).

Conclusions: ASD patients with a CrSVA-H < 2 cm by the final follow-up improved significantly across the majority of PROMs regardless of regional alignment when compared with patients who were both globally and regionally malaligned. These results further emphasize that the position of the head relative to the hips is a vital measure for the long-term improvement of PROMs following ASD surgery.