P104. Identifying C2 slope and T1 slope thresholds for optimal functional and clinical outcomes in cervical deformity correction

BACKGROUND CONTEXT Surgical correction of cervical deformity (CD) has been associated with superior alignment and functional outcomes. It has not yet been determined whether baseline and postoperative T1 slope and C2 slope correlate with health-related quality of life (HRQL) metrics and radiographic complication. PURPOSE To determine the impact of T1S and C2S deformity severity on HRQL metrics and DJK development in operative cervical deformity patients. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE A total of 119 CD patients. OUTCOME MEASURES Radiographic parameters; HRQLs. METHODS Included: Operative CD patients with UIV above C7 and with pre-(BL) and up to 2-year (2Y) postop radiographic/HRQL data. Cervical deformity was defined as meeting at least one of the following radiographic parameters: C2-C7 lordosis 35°, segmental cervical kyphosis >15° across any 3 vertebra between C2-T1, C2-C7 SVA >4cm, McGregor's slope >20°, or CBVA > 25°. Spearman's rank-order correlation and linear regression analysis assessed the impact of baseline T1 slope (T1S) and C2 slope (C2S) on baseline HRQL metrics (NDI, mJOA, EQ5D, NRS Neck, NRS Back), and the impact of postoperative T1S and C2S on follow-up HRQLs. Logistic regression and conditional inference tree (CIT) machine learning were used to determine baseline radiographic thresholds for improving in ≥2 HRQL metrics from BL to 2Y, and 2Y radiographic thresholds for developing DJK or DJF by 2Y postop. RESULTS A total of 119 CD patients met inclusion criteria (61.2±10.5years, 63%F, BMI 29.0±7.5kg/m2, CCI: 1.00±1.31) and underwent surgery (levels fused 7.5±3.7, EBL 990mL, op time 547min). By approach, 19.3% anterior-only, 44.5% posterior-only, and 36.1% combined. Mean BL radiographic parameters: PT 19.6°, PI-LL 1.4°, SVA 1.9mm, T2-T12 kyphosis -46.8°, C2-C7 lordosis -9.0°, T1S 29.0°, TS-CL 38.2°, C2S 37.7°, cSVA 44.0mm, and C2-T3 -18.0°. Mean BL HRQLs were as follows: NRS back 5.0, NRS neck 6.7, NDI 47.9, mJOA 13.5, and EQ5D 0.74. Spearman correlation and linear regression identified no association between baseline T1S or C2S and HRQL metrics, or between 2Y postop T1S and HRQLs (all p>0.05). Correlation and linear regression found significant associations of higher C2S with higher NDI (p=0.042), lower mJOA (p=0.011), and lower EQ5D (p=0.009), all indicating higher degree of disability at 2Y postop. Logistic regression with CIT identified thresholds for improving in 2 or more HRQL metrics by 2Y postop: baseline T1S 45.3° (OR: 16.0) and C2S >32.5° (OR: 6.07); both p CONCLUSIONS Baseline deformity severity in terms of T1 slope and C2 slope can be predictive of postoperative functional outcomes in cervical deformity patients, while postoperative deformity in T1S and C2S can be predictive of DJK and DJF occurrence. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.