title: What happens to the bone flap? Long-term outcome after reimplantation of cryoconserved bone flaps in a consecutive series of 92 patients.
abstract: BACKGROUND
  Reimplantation of cryoconserved autologous bone flaps is a standard procedure after decompressive craniotomies. Aseptic necrosis and resorption are the most frequent complications of this procedure. At present there is no consensus regarding the definition of the relevant extent and indication for surgical revision. The objective of this retrospective analysis was to identify the incidence of bone flap resorption and the optimal duration of follow-up.
  
  
  METHODS
  Between February 2009 and March 2012, 100 cryoconserved autologous bone flaps were reimplanted at the Department of Neurosurgery, Inselspital Bern. Three patients were not available for follow-up, and five patients died before follow-up. All patients underwent follow-up at 6 weeks and a second follow-up more than 12 months postoperatively. A clinical and CT-based score was developed for judgment of relevance and decision making for surgical revision.
  
  
  RESULTS
  Mean follow-up period was 21.6 months postoperatively (range: 12 to 47 months); 48.9 % (45/92) of patients showed no signs of bone flap resorption, 20.7 % (19/92) showed minor resorption with no need for surgical revision, and 30.4 % (28/92) showed major resorption (in 4 % of these the bone flap was unstable or collapsed).
  
  
  CONCLUSIONS
  Aseptic necrosis and resorption of reimplanted autologous bone flaps occurred more frequently in our series of patients than in most reports in the literature. Most cases were identified between 6 and 12 months postoperatively. Clinical observation or CT scans of patients with autologous bone flaps are recommended for at least 12 months. Patient-specific implants may be preferable to autologous bone flaps.
authors.affiliation: Department of Neurosurgery, Zurich University Hospital, 8091, Zurich, Switzerland, lennart.stieglitz@usz.ch.
authors.forename: Lennart Henning
authors.initials: LH
authors.lastname: Stieglitz
authors.forename: Christian
authors.initials: C
authors.lastname: Fung
authors.forename: Michael
authors.initials: M
authors.lastname: Murek
authors.forename: Jens
authors.initials: J
authors.lastname: Fichtner
authors.forename: Andreas
authors.initials: A
authors.lastname: Raabe
authors.forename: Jürgen
authors.initials: J
authors.lastname: Beck
mesh_terms: D000328:Adult; D001862:Bone Resorption / Q000453:epidemiology*; D003399:Craniotomy / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012086:Reoperation / Q000706:statistics & numerical data*; D012092:Replantation / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D013524:Surgical Flaps / Q000706:statistics & numerical data*; D016896:Treatment Outcome