Influence of Alignment Goal Achievement on Patient-reported Outcomes in Adult Spinal Deformity Surgery

Introduction: In adult spinal deformity (ASD) surgery, achieving specific alignment goals, such as goal T4 Pelvic Angle (T4PA) and L1 Pelvic Angle (L1PA), is hypothesized to impact functional outcomes. However, the relationship between these alignment targets and patient-reported outcome measures (PROMs), such as the Oswestry Disability Index (ODI), remains unclear. This study investigates the association between achieving alignment goals and the likelihood of reaching minimal clinically important difference (MCID) and substantial clinical benefit (SCB) in ODI scores.

Methods: A retrospective analysis was conducted on ASD patients with recorded ODI scores pre- and postoperatively (n = 108). Patients were divided into four groups based on goal achievement: both T4PA and L1PA goals, L1PA goal only, T4PA goal only, or neither goal. MCID and SCB were defined as ODI score reductions of ≥12.8 and ≥18.8 points, respectively. Fisher’s Exact Test was used to evaluate statistical significance between goal groups and outcome achievement.

Results: Achievement rates for MCID were similar across groups, with 64.7% in the both-goals group, 74.2% in the L1PA-only group, 66.7% in the neither-goal group, and 72.2% in the T4PA-only group. SCB rates were 49.0% (both goals), 58.1% (L1PA only), 55.6% (neither goal), and 72.2% (T4PA only). No statistically significant differences were observed in MCID (p = 0.8347) or SCB (p = 0.4062) achievement rates between groups.

Conclusion : While alignment goals such as T4PA and L1PA are essential for achieving structural correction in ASD surgery, their impact on PROMs, such as ODI, appears limited. These findings underscore the multifactorial nature of PROMs, which are influenced by a range of factors beyond spinal alignment. Therefore, the utility of alignment targets should not be assessed solely by their influence on PROMs but rather by their role in reducing mechanical failure and reoperation rates. Future research should explore additional factors impacting functional recovery to optimize patient-centered results.