Study design: Retrospective clinical study.
Objective: To study the long-term effects of repeat cervical fusion after development of adjacent segment disease (ASD).
Summary of background data: ASD is a well-recognized development after anterior cervical discectomy and fusion (ACDF). Although there are data on the development of ASD after ACDF, the incidence of ASD after repeat ACDF has not been well established.
Methods: We collected 888 consecutive patients who underwent ACDF for cervical degenerative disease during a 20-year period at a single institution. Patients were followed for an average of 94.0 ± 78.1 months after the first ACDF.
Results: Of the 888 patients who underwent ACDF, 108 patients developed ASD, necessitating a second cervical fusion. Among these 108 patients, 27 patients later developed recurrent ASD, requiring a third cervical fusion. Thus, in this series, the incidence of ASD after ACDF is 12.2%, statistically increasing to 25% after a second cervical fusion (P = 0.0002). Notably, ASD occurred 47.0 ± 44.9 months after the first ACDF and statistically decreased to 30.3 ± 24.9 months after a second cervical fusion (P = 0.01). Of the 77 patients who underwent a second cervical fusion via an anterior approach, 23 developed recurrent ASD requiring a third cervical fusion. In contrast, of the 31 patients who had a posteriorly approached second cervical fusion, only 4 developed recurrent ASD requiring a third cervical fusion.
Conclusion: We present a cohort of patients undergoing multiple sequential operations due to ASD during a 20-year period. In this series of 888 patients, the incidence of ASD development is lowest after the first ACDF. Patients who undergo a second cervical fusion develop ASD at both higher and faster rates. Moreover, patients who had a second cervical fusion via an anterior approach had a higher chance of developing recurrent ASD versus patients who had a posterior approach.
Level of evidence: 3.