Influence of Preoperative Cervical Spine Curvature in Postoperative Radiographic Outcomes Following Anterior Cervical Discectomy and Fusion: A Single-Center Retrospective Study.

Background Anterior cervical discectomy and fusion (ACDF) is a common surgical procedure that patients undergo for cervical disc herniations and degenerative disc disease, aimed at relieving radicular symptoms and restoring cervical alignment. The impact of preoperative kyphotic cervical imbalance versus preoperative lordosis on postoperative radiographic outcomes in ACDF patients is unclear. The purpose of this study is to examine how preoperative cervical sagittal balance can influence quantified postoperative cervical sagittal balance. Methods This retrospective study studied patients who had an ACDF at the Virginia Commonwealth University Medical Center from 2005 to 2017. Patients with preoperative and postoperative cervical radiographs, with radiographs of at least 1.5 years postoperatively, were included. While follow-up time frames varied from patient to patient, participants were excluded if they had any missing preoperative or postoperative imaging at least 1.5 years after the surgery date. Additionally, patients were excluded if they had prior cervical spine surgery or trauma, or if they had missing information on postoperative or preoperative imaging. Cervical sagittal parameters, including the atlantoaxial C1-C2 angle, C2-C6 Cobb angle, C7 slope, and cervical sagittal vertical axis (cSVA), were measured using Surgimap, an analytical radiographic imaging software. Patients were divided into preoperative lordotic and kyphotic cohorts based on preoperative C2-C6 Cobb angle. Results Of the 507 patients undergoing ACDF, 65 met the inclusion criteria. There was no significant difference in follow-up between the surgery date and the first postoperative follow-up, among the kyphotic (129.8 ± 296.2 days) and lordotic (142.7 ± 393.3 days) cohorts (p=0.88). There was also no significant difference between the cohorts in the total follow-up duration from the time of surgery to the last follow-up (kyphotic:1217.2±803.7 days; lordotic: 1640.8±1112.7 days; p=0.087). The kyphotic cohort had a significant change in the C2-C6 Cobb angle postoperatively (-10.0º (95% CI -14.197º-5.809º); p<0.0001), sustained through the last documented follow-up (net change: -8.956º (95% CI -12.952º-4.960º), p<0.0001). There was no significant difference in the Cobb angle in the lordotic cohort both at the first postoperative follow-up (-2.19º (95% CI 6.76º -2.37º); p=0.34) and at the last documented follow-up (net change: 2.03º (95% CI 3.20-7.25); p=0.44). The postoperative Cobb angles at the last documented follow-up in the kyphotic (-2.6º±10.9º) and lordotic (-6.3º±13.1º) cohorts did not vary significantly (p=0.23).  Conclusion Long-term improvements following ACDF in patients with preoperative kyphosis suggests that the procedure, in the long term, is effective in restoring structural cervical lordosis and radiographic properties in the maintenance of cervical sagittal alignment, regardless of preoperative cervical alignment. Future studies can assess how preoperative kyphosis and lordosis influences clinical outcomes, such as functionality and pain following ACDF to determine whether preoperative alignment has a role in the procedure's outcomes.