title: Adjacent segment disease after anterior cervical discectomy and fusion: clinical outcomes after first repeat surgery versus second repeat surgery.
abstract: METHODS
  Retrospective clinical study.
  
  
  OBJECTIVE
  To study the long-term effects of repeat cervical fusion after development of adjacent segment disease (ASD).
  
  
  BACKGROUND
  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.
  
  
  CONCLUSIONS
  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.
  
  
  METHODS
  3.
authors.affiliation: *Department of Neurosurgery and †Spinal Column Biomechanics and Surgical Outcomes Laboratory, Johns Hopkins University School of Medicine, Baltimore, MD; and ‡Medical Scientist Training Program, Johns Hopkins School of Medicine, Baltimore, MD.
authors.forename: Risheng
authors.initials: R
authors.lastname: Xu
authors.forename: Mohamad
authors.initials: M
authors.lastname: Bydon
authors.forename: Mohamed
authors.initials: M
authors.lastname: Macki
authors.forename: Rafael
authors.initials: R
authors.lastname: De la Garza-Ramos
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Sciubba
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Wolinsky
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Witham
authors.forename: Ziya L
authors.initials: ZL
authors.lastname: Gokaslan
authors.forename: Ali
authors.initials: A
authors.lastname: Bydon
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000473:pathology / Q000601:surgery*; D017586:Diskectomy / Q000009:adverse effects* / Q000639:trends; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis* / Q000453:epidemiology*; D012086:Reoperation / Q000009:adverse effects* / Q000639:trends; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects* / Q000639:trends; D016896:Treatment Outcome