title: Quantitative in vivo fusion assessment by (18)F-fluoride PET/CT following en bloc spondylectomy.
abstract: OBJECTIVE
  The purpose of this retrospective analyses was to evaluate the bone viability in the ventral column of the spine following large segmental defect reconstructions. Osseous integration of implants following spinal fusion procedures is an essential precondition to provide adequate mechanical strength to any applied forces and subsequently satisfying patient outcomes. Although CT scan is the non-invasive gold standard for fusion assessment, it lacks the ability to visualize bone viability and, therefore, discrepancy remains about sensitivity and specificity of CT as evaluation tool of spinal fusion.
  
  
  METHODS
  A novel modality, (18)F Fluoride PET/CT, specifically allows quantitative in vivo evaluation of metabolic activity of the osseous integration. Bone viability following large segmental reconstructions in patients after mono- and multi-level en bloc spondylectomies (EBS) was analyzed. Spinal fusion was assessed on plain radiographs and CT scans according to the FDA fusion criteria as well as (18)F PET/CT.
  
  
  RESULTS
  A total of eight patients underwent (18)F PET/CT were included (one 4-level-, one 3-level, two 2-level and four 1-level EBS). The average follow-up between EBS and radiographic studies was 24.8 months. On plain radiographs and CT scans, successful fusion was confirmed in all patients. However, (18)F PET/CT showed non-union in all cases. The metabolic bone activity within the cage was fourfold decreased compared to the reference vertebra, whereas the metabolic activity of the adjacent endplates was 1.6-fold increased compared to the reference vertebra.
  
  
  CONCLUSIONS
  This study suggests a discrepancy between fusion rates assessed by plain radiographs and CT scan compared to (18)F PET/CT.
authors.affiliation: Department of Spine Surgery, Center for Musculoskeletal Surgery, Charité, Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany. matthiaspumberger@gmail.com.
authors.forename: Matthias
authors.initials: M
authors.lastname: Pumberger
authors.affiliation: Department of Nuclear Medicine, Charité Universitätsmedizin Berlin, Berlin, Germany. vikas.prasad@charite.de.
authors.forename: Vikas
authors.initials: V
authors.lastname: Prasad
authors.affiliation: Department of Spine Surgery, Center for Musculoskeletal Surgery, Charité, Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Druschel
authors.affiliation: Department of Spine Surgery, Center for Musculoskeletal Surgery, Charité, Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Disch
authors.affiliation: Department of Nuclear Medicine, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Winfried
authors.initials: W
authors.lastname: Brenner
authors.affiliation: Department of Spine Surgery, Center for Musculoskeletal Surgery, Charité, Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Schaser
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005462:Fluorine Radioisotopes; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D016348:Osseointegration; D049268:Positron-Emission Tomography; D011184:Postoperative Period; D012189:Retrospective Studies; D013123:Spinal Fusion; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D014057:Tomography, X-Ray Computed
chemical_list: D005462:Fluorine Radioisotopes
keywords: 18F-Fluoride PET/CT; Bone viability; Cage fusion; En bloc spondylectomy; Fusion assessment; Non-union; Spine fusion