Pack Years of Tobacco Cigarette Smoking as a Predictor of Bony Fusion After Anterior Cervical Discectomy and Fusion

Objective: Smoking tobacco cigarettes negatively impacts bone healing after spinal fusion. Smoking history is often assessed based on current smoker and nonsmoker status. However, in current research, smoking history has not been quantified in terms of pack years to estimate lifetime exposure and assess its effects. Our goal was to investigate the influence of smoking history, quantified in pack years, on bony fusion after anterior cervical discectomy and fusion (ACDF).

Methods: A retrospective chart review of consecutive patients who underwent ACDF for cervical disc degeneration between September 21, 2017 and October 17, 2018 was conducted. Patient demographics, procedural variables, and postoperative outcomes were analyzed. Multivariate logistic regression analysis was performed to identify predictive factors for bony fusion following ACDF. Receiver operating characteristic (ROC) curve analysis was used to determine the optimal discrimination threshold for smoking history pack years in association with nonfusion.

Results: Among 97 patients identified, 90 (93%) demonstrated bony fusion on postoperative imaging. Mean number of smoking history pack years was 6.1±13 for the fusion group and 16 ±21 for the nonfusion group. Multivariate logistic regression analysis suggested that increased pack years of tobacco cigarette smoking was a significant predictor of nonfusion (95% confidence interval, [1.0,1.1], p=0.045). The ROC curve analysis revealed that 6.1 pack years best stratified the risk for nonfusion (area under the curve, 0.8).

Conclusion: Patients with a history of tobacco cigarette smoking >6.1 pack years may have an increased risk of nonfusion after ACDF.