Comparison of cervical alignment between electromagnetic and traction-based head positioning systems

The goal of this study was to compare pre- and postoperative radiographic spinal parameters and clinical outcomes for patients who underwent ≥3 level posterior cervical fusion using bivector traction (BVT) and an electro-mechanical head positioner (EMHP). We reviewed cervical fusions performed between 1/1/2019-7/31/2022. Demographic and surgical information, and preoperative and minimum 6-months postoperative Neck Disability Index (NDI) scores were collected. Pre- and post-operative C2 slope, T1 slope, cervical lordosis, and C2-C7 sagittal vertical axis (cSVA) were measured. One hundred-thirty patients (56M:74F) were included. Mean age was 61.3±10.5 years and BMI 30.1±6.4 kg/m 2 . EMHP was used in 75 cases and BVT in 55. The average number of levels fused (6.7 vs. 5.4, p<0.001) and number of intrabodies (3.1 vs. 2.8, p=0.34) was higher in the EMHP group versus the BVT group while time to pseudoarthrosis (14.2 vs. 18.0 months, p=0.31) was lower. The EMHP group had significant increases in T1 slope (3.2°, p=0.01), C2 slope reduction (5.1°, p=0.04), cervical lordosis (6.5°, p=.001), and cSVA (0.4cm, p=0.02) postoperatively. The BVT group showed significant improvements in T1 slope (4.8°, p=0.005), cervical lordosis (2.2°, p=0.006), but no significant change in C2 slope or cSVA. NDI improved significantly in both groups at follow-up (EMHP: 10.6 points, p<0.001; BVT: 12.7 points, p<0.001). Using the EMHP and BVT resulted in significant radiographic improvements in this cohort. However, this didn't correlate with greater improvements in NDI, suggesting BVT or EMHP are acceptable options for head positioning in posterior cervical deformity correction surgery.