Risk factors of second surgery for adjacent segment disease following anterior cervical discectomy and fusion: A 16-year cohort study

Background: Although the incidence of second surgery for adjacent segment disease (ASD) after anterior cervical discectomy and fusion (ACDF) has been reported, its risk factors remain elusive. Few studies have had a sufficiently large number of patients, long follow-up time, and high follow-up rate for investigation. To identify non-surgical risk factors of second surgery for ASD following ACDF, the study used a national cohort with comprehensive follow-up. Materials and methods: All second ACDF surgery after one year from the first ACDF were identified as a consequence of ASD that required another surgery. A multivariate competing risk survival model, Kaplan-Meier survivorship, and average time to events were calculated. Results: Among 38,149 patients who had the first ACDF, 1,092 (2.9%) later (mean 4.66 years) received a second ACDF surgery, during the nearly-perfect follow-up of 16 years. Young age and psychiatric disorders were independent risk factors. Patients who were aged under 40, 50, 60 and 70 years were, respectively, 4.56, 4.09, 3.09 and 2.17 times more likely than those older than 70 years. Also, patients with depression or psychoses were, respectively, 1.42 and 1.45 times more likely to have second surgery for ASD. (all p < 0.05). Conclusion: Young age and psychiatric disorders are independent risk factors of second ACDF surgery for ASD. Personalized strategies to ameliorate or postpone the development of ASD are therefore warranted for patients who need ACDF surgery.