26 - Can Baseline Disability Predict Outcomes in Adult Spinal Deformity Surgery?

Introduction: Surgical intervention has previously been shown to be an effective treatment modality for adult spinal deformity (ASD), yet patient reported outcomes vary even when patients are optimally realigned. Identifying patients most likely to benefit from operative intervention is of substantial clinical interest.

Aims/

Objectives: To understand the association between baseline disability and postoperative maximum improvement in ASD patients.

Methods: This is a retrospective analysis of prospectively enrolled patients from a single center ASD database. Patients with baseline (BL) and 2-year (2Y) data were included. Disability was assessed by BL ODI and cohort was then ranked by BL ODI into 5 disability groups: Q1 (lowest ODI score) to Q5 (highest ODI score). Logistic regression analyses generated odds ratios (OR) for reaching ≥ 1 MCID in SRS-22 Pain, SRS-22 Activity, and SF-36 PCS at 2Y across disability groups Q1 – Q4 with respect to Q5. All analyses adjusted for BL age, BL deformity and realignment at 6-weeks post-op, respective BL HRQL scores as well as surgical invasiveness, major complications, and reoperations. Sensitivity tests were performed, excluding patients with any “0” Schwab modifiers at BL.

Results: 356 patients met inclusion (59.3yrs, 81.1% F, CCI: 1.5, BMI: 27.0kg/m2). Mean BL ODI of the disability groups were as follows: Q1 (N=71): 16±7, Q2 (N=67): 32±3, Q3 (N=72): 41±2, Q4 (N=72): 51±3, and Q5 (N=74): 67±8. LR found that comparted to patients in Q5, odds of reaching MCID in SRS-22-Pain at 2Y were significantly higher for those in Q1 (OR: 3.771), Q2 (OR: 3.006), and Q3 (OR: 2.897), all p<.021. Similarly, compared to patients in Q5, odds of reaching MCID in SRS-22-Activity at 2Y were significantly higher for those in Q2 (OR: 3.454) and Q3 (OR: 2.801), both p<.02. Lastly, compared to patients in Q5, odds of reaching MCID in SF-36-PCS at 2Y were significantly higher for patients in Q1 (OR: 5.350), Q2 (OR: 4.795) and Q3 (OR: 6.229), all p<.004. After excluding patients with “0” Schwab modifiers at BL, 152 patients remained for sensitivity testing. Mean BL ODI of the disability groups were as follows: Q1 (N=23): 19±10, Q2 (N=36): 36±3, Q3 (N=29): 45±3, Q4 (N=25): 55±3, and Q5 (N=39): 68±8. Compared to those in Q5, patients in Q2 had significantly higher odds of reaching MCID in SRS-22 Pain (OR: 4.910), MCID in SRS-22 Activity (OR: 4.321), and MCID in SF-36 PCS (OR: 4.470), all p<.036.

Conclusions: This study found that patients presenting with moderate disability at BL (ODI < 40) consistently surpassed HRQL outcomes as compared to those presenting with greater levels of disability. We propose that a baseline ODI of 40 represents a disability threshold within which operative intervention maximizes patient reported outcomes. Furthermore, delaying intervention until patients progress to severe disability, may limit benefits of surgical correction in ASD patients.