title: Interval cranioplasty: comparison of current standards.
abstract: BACKGROUND
  Although different cranioplasty storage methods are currently in use, no study has prospectively compared these methods. The authors compare freezing and subcutaneous storage methods in a rat model.
  
  
  METHODS
  Trephine defects (10 mm) were created in 45 Sprague-Dawley rats. The cranial bone grafts were stored in an autologous subcutaneous pocket (n = 15), frozen at -80°C (n = 15), immediately analyzed (n = 12), or immediately replanted into the defect (n = 3). After 10 days of storage, the subcutaneous or frozen grafts were either replanted (subcutaneous, n = 3; frozen, n = 3) or analyzed (subcutaneous, n = 12; frozen, n = 12). Grafts underwent histologic analysis, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, alkaline phosphatase assay, mechanical testing, and micro-computed tomographic imaging.
  
  
  RESULTS
  After 10 days of storage, physiologic assays demonstrated a significant decrease in cellular functionality (e.g., alkaline phosphatase assay concentration: fresh, 18.8 ± 0.77 mM/mg; subcutaneous, 12.2 ± 0.63 mM/mg; frozen, 8.07 ± 1.1 mM/mg; p < 0.012 for all comparisons). Mechanical integrity (maximal load) of fresh grafts was greatest (fresh, 9.26 ± 0.29 N; subcutaneous, 6.27 ± 0.64 N; frozen, 4.65 ± 0.29 N; fresh compared with frozen, p < 0.001; fresh compared with subcutaneous, p = 0.006). Replantation of subcutaneously stored and frozen grafts resulted in limited bony union and considerable resorption after 12 weeks; in contrast, replanted fresh grafts demonstrated bony union and little resorption.
  
  
  CONCLUSIONS
  Current preservation methods for interval cranioplasty do not maintain bone graft viability. Subcutaneous storage appears to provide a small advantage compared with freezing.
authors.affiliation: New York, N.Y. From the Institute of Reconstructive Plastic Surgery Laboratories, New York University Medical Center, and the New York University College of Dentistry.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Sultan
authors.forename: Edward H
authors.initials: EH
authors.lastname: Davidson
authors.forename: Parag
authors.initials: P
authors.lastname: Butala
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Schachar
authors.forename: Lukasz
authors.initials: L
authors.lastname: Witek
authors.forename: Caroline
authors.initials: C
authors.lastname: Szpalski
authors.forename: Jack L
authors.initials: JL
authors.lastname: Ricci
authors.forename: Pierre B
authors.initials: PB
authors.lastname: Saadeh
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Warren
mesh_terms: D000818:Animals; D016025:Bone Transplantation / Q000379:methods*; D003399:Craniotomy / Q000379:methods*; D062109:Dermatologic Surgical Procedures; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D005615:Freezing; D008297:Male; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley; D012092:Replantation / Q000379:methods*; D012886:Skull / Q000000981:diagnostic imaging / Q000601:surgery*; D014021:Tissue Preservation / Q000379:methods*; D055114:X-Ray Microtomography