1070 Does Higher T1 Slope Predict Poor Outcomes Following Posterior Cervical Fusion for Degenerative Pathology?

INTRODUCTION: The success of posterior cervical fusion (PCF) depends on various patient-specific anatomical and biomechanical factors, among which includes the T1 slope angle. Despite the recognized association with cervical spine biomechanics, the influence of T1 slope angle on surgical outcomes remains understudied. METHODS: A single-institution retrospective cohort study of patients undergoing PCF for degenerative pathology were studied from 2010-2022. Primary exposure variable was postoperative T1 slope. Outcomes of interest included mechanical complications, reoperation rate, and PROMs, including neck disability index (NDI%), neck and arm pain visual analogue score, and quality of life (EQ5D) at 3, 12 and 24 months. Multivariable regression models were conducted for each outcome, controlling for age and BMI. RESULTS: Among 197 patients undergoing PCF, the mean age was 62.4±9.8, 111 (56.3%) were male, and mean follow-up time was 3.8±3.2 years. The median (IQR) T1 slope was 27.2º (21.4-33.4º). 33 (16.7%) patients had mechanical complications including pseudarthrosis (6.1%), hardware fracture (6.1%), and screw loosening (87.9%). Further, 10 (5.0%) patients underwent reoperation. Patients with mechanical complications had a greater mean T1 slope (30.6±8.0 vs. 27.0±8.4º, p=0.028) compared to patients without, though no difference was found in T1 slope among patients with and without reoperation (28.7±7.8 vs. 27.8±8.5º, p=0.747). On cox-proportional hazard regression, T1 slope was independently associated with an increased risk of developing mechanical complications (HR=1.04, 95%CI=1.01-1.09, p=0.020). T1-slope had no significant correlation to any PROMs on linear regression (p>0.050). CONCLUSIONS: In our cohort of patients undergoing PCF, a greater T1 slope increased the risk of developing mechanical complications, with no significant associations with reoperation or PROMs. These findings highlight the importance of considering T1 slope as a potential risk factor in surgical planning for PCF.