title: Radiologic Assessment of Subsidence in Stand-Alone Cervical Polyetheretherketone (PEEK) Cage.
abstract: OBJECTIVE
  Aim of study was to find a proper method for assessing subsidence using a radiologic measurement following anterior cervical discectomy and fusion (ACDF) with stand-alone polyetheretherketone (PEEK), Solistrade mark cage.
  
  
  METHODS
  Forty-two patients who underwent ACDF with Solistrade mark cage were selected. With a minimum follow-up of 6 months, the retrospective investigation was conducted for 37 levels in 32 patients. Mean follow-up period was 18.9 months. Total intervertebral height (TIH) of two fused vertebral bodies was measured on digital radiographs with built-in software. Degree of subsidence (DeltaTIH) was reflected by the difference between the immediate postoperative and follow-up TIH. Change of postoperative disc space height (CT-MRDeltaTIH) was reflected by the difference between TIH of the preoperative mid-sagittal 2D CT and that of the preoperative mid-sagittal T1-weighted MRI.
  
  
  RESULTS
  Compared to preoperative findings, postoperative disc height was increased in all cases and subsidence was observed only in 3 cases. For comparison of subsidence and non-subsidence group, TIH and CT-MRDeltaTIH of each group were analyzed. There was no statistically significant difference in TIH and CT-MRDeltaTIH between each group at 4 and 8 weeks, but a difference was observed at the last follow-up TIH (p=0.0497).
  
  
  CONCLUSIONS
  ACDF with Solistrade mark cage was associated with relatively good radiologic long-term results. Fusion was achieved in 94.5% and subsidence occurred in 8.1% by the radiologic assessment. Statistical analysis reveals that the subsidence seen later than 8 weeks after surgery and the development of subsidence does not correlate statistically with the change of the postoperative disc space height.
authors.affiliation: Department of Neurosurgery, Korea University Medical Center Ansan Hospital, Ansan, Korea.
authors.forename: Sung-Kon
authors.initials: SK
authors.lastname: Ha
authors.forename: Jung-Yul
authors.initials: JY
authors.lastname: Park
authors.forename: Se-Hoon
authors.initials: SH
authors.lastname: Kim
authors.forename: Dong-Jun
authors.initials: DJ
authors.lastname: Lim
authors.forename: Sang-Dae
authors.initials: SD
authors.lastname: Kim
authors.forename: Sang-Kook
authors.initials: SK
authors.lastname: Lee