title: Histological examination of frozen autograft treated by liquid nitrogen removed after implantation.
abstract: BACKGROUND
  Several oncological sterilization methods involving autoclaving, irradiation, or pasteurization have been developed for limb reconstruction of large bone defects following tumor excision. Studies involving histological examinations of these autografts have all found that osteogenesis occurs slowly. We have used frozen autografts treated by liquid nitrogen for limb reconstruction and have achieved excellent results for bone union. To determine if frozen autografts exhibit early bone remodeling, we investigated the repair processes of the frozen bones.
  
  
  METHODS
  We analyzed frozen autografts treated by liquid nitrogen, retrieved at a mean of 19.1 months (2-75 months) after implantation because of complications or local tumor recurrence. The specimens were obtained from six patients with a mean age of 36.2 years (8-68 years). The six grafts comprised three osteoarticular grafts, two intercalary grafts, and one joint graft. We histologically reviewed the autograft-containing sections for tumor cell necrosis, evidence of cortical repair, the cortical junction, and joint cartilage.
  
  
  RESULTS
  Tumor cells were completely eradicated from the frozen bone in all cases. In a specimen retrieved 5 months after implantation, a small area of the bone showed active osteocytes and osteoblasts. In three cases retrieved more than 1 year after implantation, osteocytes and osteoblasts were observed in broad portions of the frozen bones, indicating the onset of osteogenesis in the frozen bone at an early stage. The cortical host-graft junction showed incorporation along with continuity of bone trabeculae. In addition, we were able to fi nd normal chondrocytes on the articular surface.
  
  
  CONCLUSIONS
  The frozen bone specimens in this study thus showed evidence of newly formed bone and earlier osteogenesis than has been previously reported. Our results suggest that frozen autografts may be considered one of the most useful recycled materials for biological reconstruction.
authors.affiliation: Department of Orthopaedic Surgery, Kanazawa University School of Medicine, 13-1 Takaramachi, Kanazawa 920-8641, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Tanzawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsuchiya
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shirai
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Hayashi
authors.forename: Zen
authors.initials: Z
authors.lastname: Yo
authors.forename: Katsuro
authors.initials: K
authors.lastname: Tomita
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001859:Bone Neoplasms / Q000601:surgery*; D016723:Bone Remodeling; D016025:Bone Transplantation; D002356:Cartilage / Q000637:transplantation; D002648:Child; D019902:Chondrocytes / Q000637:transplantation*; D015331:Cohort Studies; D005260:Female; D005615:Freezing; D006801:Humans; D023821:Limb Salvage / Q000379:methods; D008297:Male; D008875:Middle Aged; D010012:Osteogenesis; D012086:Reoperation; D013048:Specimen Handling / Q000379:methods*; D013242:Sterilization / Q000379:methods*; D014182:Transplantation, Autologous / Q000379:methods* / Q000502:physiology; D055815:Young Adult