title: Radiological changes in anterior cervical discectomy and fusion with cage and plate construct: the significance of the anterior spur formation sign.
abstract: METHODS
  Retrospective review.
  
  
  OBJECTIVE
  To analyze the changes of fusion process and radiological parameters during the postoperative period after anterior cervical discectomy and fusion with cage and plate construct (ACDF-CPC).
  
  
  BACKGROUND
  Because of its well-reported efficacy, plate augmentation has been performed to avoid the various complications associated with the cage-alone procedure. The radiological changes at the fusion site after ACDF-CPC have yet to be fully explored.
  
  
  METHODS
  Seventy-eight patients (122 fusion sites) who underwent ACDF-CPC were observed at 6 weeks and at 3, 6, 12, and 24 months postoperatively. Fusion status was classified into 3 categories: Type I (pseudoarthrosis), Type II (borderline), and Type III (fusion). Changes at the fusion site were described through radiological parameters at each follow-up time point. In addition, the ability of the radiological parameters to predict fusion rates was analyzed.
  
  
  RESULTS
  The fusion process after ACDF-CPC progresses slower when compared with the standard procedure utilizing autograft. Fusion between bone graft chips begins at 6 weeks post surgery. At 3 months, initial bone bridging between graft and host bones begins to form. Anterior spur formation occurs at 3 to 6 months, and "kissing" lesions form at 6 to 12 months. Bony incorporation is achieved at 1 to 2 years. Persistent or newly developed Type I at the 1-year follow-up exhibited significantly higher pseudoarthrosis rates in comparison with rates determined at the 3- and 6-month time points. Among 29 subsidence cases, 9 of the 16 (56.3%) cases that exhibited anterior spur formation eventually achieved fusion, whereas 2 of the 13 (15.4%) cases that did not exhibit anterior spur formation eventually achieved fusion. In cases that demonstrated anterior spur formation, the fusion rate was significantly higher than in cases without it (P = 0.016).
  
  
  CONCLUSIONS
  The fusion process after ACDF-CPC progresses slower than the standard procedure utilizing autograft. Cage subsidence of greater than 2 mm, a radiolucent defect, or a halo sign are poor prognostic signs indicating a high probability for pseudoarthrosis when detected radiographically after 1 year postoperatively. The anterior spur formation sign and "kissing" lesion, on the contrary, represent signs for eventual successful fusion.
authors.affiliation: Department of Radiology, Chonbuk National University Medical School, Research Institute of Clinical Medicine, Chonbuk National University Hospital, Jeonju, Chonbuk, Korea.
authors.forename: Jisoo
authors.initials: J
authors.lastname: Song
authors.forename: Cyrus E
authors.initials: CE
authors.lastname: Taghavi
authors.forename: David W
authors.initials: DW
authors.lastname: Hsu
authors.forename: Kyung-Jin
authors.initials: KJ
authors.lastname: Song
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Song
authors.forename: Kwang-Bok
authors.initials: KB
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001860:Bone Plates; D016025:Bone Transplantation; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D017586:Diskectomy / Q000379:methods*; D005260:Female; D006801:Humans; D016268:Internal Fixators; D007403:Intervertebral Disc / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D011859:Radiography; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000379:methods*; D016896:Treatment Outcome