Predictors of Superior Recovery Kinetics in Adult Cervical Deformity Correction: An Analysis Using a Novel Area Under the Curve Methodology.

STUDY DESIGN Retrospective review of a prospective database. OBJECTIVE Identify demographic, surgical, and radiographic factors that predict superior recovery kinetics following CD corrective surgery. SUMMARY OF BACKGROUND DATA Analyses of cervical deformity (CD) corrective surgery use area-under-the-curve (AUC) to assess health-related quality of life (HRQL) metrics throughout recovery. METHODS Outcome Measures: Baseline (BL) to 1-Year (1Y) HRQL (Neck Disability Index [NDI]). CD criteria: C2-7 Cobb angle>10°, coronal Cobb angle>10°, cSVA>4 cm TS-CL>10°, or CBVA>25°. AUC normalization divided BL and postoperative outcomes by BL. Normalized scores(y-axis) were plotted against follow-up(x-axis). AUC was calculated and divided by cumulative follow-up length to determine overall, time-adjusted recovery (Integrated Health State [IHS]). IHS NDI was stratified by quartile, uppermost 25% being 'Superior' Recovery Kinetics (SRK) vs. 'Normal' Recovery Kinetics (NRK). BL demographic, clinical, and surgical information predicted SRK using generalized linear modeling. RESULTS 98 patients included (62 ± 10yrs, 28 ± 6 kg/m2, 65%F, CCI:0.95), 6% smokers, 31% smoking history. Surgical approach: combined (33%), posterior (49%), anterior (18%). Posterior levels fused: 8.7, anterior: 3.6, EBL: 915.9ccs, operative time: 495 min. Ames BL classification: cSVA (53.2% minor deformity, 46.8% moderate), TS-CL (9.8% minor, 4.3% moderate, 85.9% marked), horizontal gaze (27.4% minor, 46.6% moderate, 26% marked). Relative to BL NDI (Mean: 47), normalized NDI decreased at 3-months (0.9 ± 0.5, p = 0.260) and 1Y (0.78 ± 0.41, p < 0.001). NDI IHS correlated with age (p = 0.011), gender (p = 0.042), anterior approach (p = 0.042), posterior approach(p = 0.042). Greater BL PT (SRK:25.6°, NRK:17°, p = 0.002), PI-LL (SRK:8.4°, NRK:-2.8°, p = 0.009), and anterior approach (SRK:34.8%, NRK:13.3%; p = 0.020) correlated with SRK. 69.4% met MCID for NDI(<Δ-15) and 63.3% met SCB for NDI(<Δ-10); 100% of SRK met both MCID and SCB. The predictive model for SRK included(AUC = 88.1%): BL VAS EQ5D(OR 0.96, CI:0.92-0.99), BL swallow sleep score(OR:1.04, CI:1.01-1.06), BL PT(OR:1.12, CI:1.03-1.22), BL mJOA (OR:1.5, CI:1.07-2.16), BL T4-T12, BL T10-L2, BL T12-S1 and BL L1-S1. CONCLUSIONS Superior recovery kinetics following cervical deformity surgery was predicted with high accuracy using baseline patient reported (VAS EQ5D, swallow sleep, mJOA) and radiographic factors (PT, TK, T10-L2, T12-S1, L1-S1). Awareness of these factors can improve decision-making and reduce postoperative neck disability.Level of Evidence: 3.