Comparing ACDF Outcomes by Cervical Spine Level: A Single Center Retrospective Cohort Study.

Background: Previous research suggests a relationship between complications associated with anterior cervical discectomy and fusion and level involvement; however, there is limited research comparing postoperative outcomes of upper cervical fusions (UCFs) with middle-to-lower cervical fusions (MLCFs). This study aims to compare the outcomes of UCF with MLCF.

Methods: A retrospective medical record review was conducted on 835 anterior cervical discectomy and fusion patients from 2012 to 2022. Patients were classified as UCF, defined as inclusion of C3 to C4 disc space, or MLCF, defined as lacking C3 to C4 disc space. Demographics were compared using χ ² or Fisher exact tests. Clinical characteristics were compared in univariable analysis using χ ² tests, linear-mixed effects models, or generalized linear-mixed models depending on distribution. Significant pre- and intraoperative characteristics were included in multivariable models to minimize confounding.

Results: Of the 835 patients included, 562 underwent MLCF and 281 underwent UCF. Median follow-up time was 211 days for UCF and 200 days for MLCF. UCF led to a 1.5-day longer length of stay in both univariable (1.5 vs 3.1, P < 0.0001) and multivariable analysis (2.3 days [95% CI: 1.8, 3.0] vs 3.3 days [2.6, 4.2], P < 0.0001). MLCF patients reported symptom improvement or resolution more often than UCF patients (0.43 [95% CI: 0.30, 0.62] and 0.46 [95% CI: 0.30, 0.70]). Additionally, a significantly higher rate of dysphagia was reported in the UCF group on both univariate and multivariable analysis, respectively (1.72 [95% CI: 1.18, 2.49] and 1.66 [95%CI: 1.08, 2.56]).

Conclusions: To our knowledge, this is the first study to investigate the link between cervical fusion level and outcomes. UCF patients demonstrated greater rates of dysphagia, longer length of stay, and lower likelihood of improvement in neurological symptoms postoperatively both before and after controlling for differences in pre- and intraoperative characteristics.

Clinical relevance: This study highlights that UCFs may be associated with worse postoperative outcomes when compared to MLCFs, which can inform surgical decision-making and patient counseling.

Level of evidence: The study represents Level 3 evidence due to its retrospective design and potential biases, indicating a need for future prospective randomized controlled trials to validate these findings.