C1 plumb line and cervical sagittal balance predict the outcome of cervical laminectomy and fusion

The C1 plumb line (C1PL) is a vertical line extended from the anterior aspect of C1 representing the gravity vector of the weight of the head. The hypothesis of this study is that forward translation of the C1PL is associated with worse outcome of cervical laminectomy and fusion (CLF). Retrospective study of patients with cervical spondylotic myelopathy who underwent CLF for cervical spondylotic myelopathy from C3 to C7 most commonly between 2006 and 2008. Patients had at least 1-year follow-up. Trauma was excluded. Outcomes were assessed with Neck Disability Index (NDI), radiographs were reviewed and measured by a blinded observer. Measurements included the C1 plumb line (C1PL), occipital condyle plumb line (OCPL), and cervical lordosis. The interobserver correlation coefficient was increased in C1PL versus OCPL. Mean preop C1PL was 58.9 mm, SD = 23 (P = 0.02). The mean C1PL increased (average 12 mm) after cervical laminectomy and fusion surgery. There was a significant difference (P = 0.009) in change in C1PL between patients with NDI score < 40 (9.8 mm, SEM 3.2) and NDI score > 40 (22.3 mm and SEM 2.3). In conclusion, sagittal balance of the cervical spine was related to patient-reported outcome. Patients with moderate or severe neck pain had more forward sagittal imbalance (C1PL, 10 cm) compared to patients with mild neck pain (C1PL, 2 cm).