1067 Level Selection in Posterior Cervical Fusion: The Clinical Impact of Junctional Crossing

INTRODUCTION: The impact of extending posterior fusion (PCF) beyond the CTJ in combination with an upper instrumented vertebra extending to the upper cervical junction, is still unclear. Based on the biomechanical differences between the upper cervical and the subaxial cervical spine, we suggest the C2-C3 segment be considered a functional junction with potential clinical relevance. METHODS: A single-institution study of PCF patients from 2010-22 was conducted. The primary independent variable was PCF construct, regarding the upper (C2-C3) and lower (C7-T1) cervical junctions. Patients were categorized into: 1) neither junction crossed (NJX), 2) one junction crossed (OJX), or 3) both junctions crossed (BJX). Outcomes included reoperations, hardware failure, and PROs, including neck disability index (NDI%), neck and arm pain visual analogue score (VAS), and quality of life (EQ5D) at 3, 12 and 24 months. Cox-proportional hazard models were conducted controlling for age and BMI. RESULTS: Among 443 patients undergoing PCF for degenerative cervical pathology, the mean age was 62.32±10.12; 268 (60.8%) were male. Of these, 88 (19.9%) patients had BJX, 139 (31.4%) OJX, and 216 (48.8%) NJX. OJX was associated with increased risk for reoperation versus NJX (HR=3.85, 95%CI=1.90-7.79, p<0.001) and BJX (HR=3.19, 95%CI=1.44-7.03, p=0.004). OJX (OR=3.85, 95%CI=1.90-7.79, p=<.001) and BJX (OR=3.19, 95%CI=1.44-7.03,p=.004) increased the odds of hardware failure versus NJX. NJX reported less 3-month NDI% (29.36±17.93 vs. 34.16±15.08 vs. 35.07±18.61, p=.013) than BJX and OJX patients, with no difference in other PROs. CONCLUSIONS: In our cohort of patients undergoing PCF, patients with OJX had greater rates of reoperation than patients with BJX and NJX. Patients with NJX had less hardware failure and 3 month NDI% than patients with BJX and NJX, with no difference in other PROs.