title: Long-term results following cranial hydroxyapatite prosthesis implantation in a large skull defect model.
abstract: BACKGROUND
  A large skull defect may occur after different events such as trauma, tumor resection, and vascular injuries. There is still some doubt about the best material to use for reconstruction. Hydroxyapatite ceramic is one of the materials in use, and its biocompatibility and osteoconductivity are well established. This study evaluated the interaction of a commercial hydroxyapatite custom-made prosthesis implanted in a large skull defect, to assess its osteointegration and its habitability with newly formed bone over time.
  
  
  METHODS
  Ten sheep underwent craniectomy and reconstruction of the skull defect with a porous hydroxyapatite cranial prosthesis. The animals were divided into two groups: animals in group A were euthanized after 6 months and animals in group B were euthanized after 12 months. At the end of the experimental periods, each implant was evaluated macroscopically and radiologically, and analyzed by micro-computed tomography, histology, histomorphometry, and microhardness techniques.
  
  
  RESULTS
  During the study, no adverse events occurred, and there was no evidence of inflammation or negative tissue reactions. Histology and histomorphometry showed new bone formation inside the implant in both experimental periods; newly formed bone had increased significantly (p < 0.05) by over 300 percent between 6 and 12 months. Three-dimensional micro-computed tomographic analysis showed new bone formation and material remodeling. Microhardness analysis indicated that the mineralization process and the mechanical properties of newly formed bone were not altered.
  
  
  CONCLUSIONS
  The hydroxyapatite prosthesis showed its osteoconductivity and good biocompatibility. A low rate of fibrous tissue formation and a high rate of bony regeneration were found.
authors.affiliation: Bologna, Lugo, and Faenza, Italy From the Laboratory of Preclinic and Surgical Studies, Rizzoli Orthopaedic Institute; the Laboratory of Biocompatibility, Technological Innovations, and Advanced Therapies, Rizzoli Research Innovation Technology; the Division of Neurotraumatology, Umberto I Hospital; the Division of Neurotraumatology, Bellaria Hospital; and Fin-Ceramica Faenza S.p.A.
authors.forename: Lucia
authors.initials: L
authors.lastname: Martini
authors.forename: Guido
authors.initials: G
authors.lastname: Staffa
authors.forename: Gianluca
authors.initials: G
authors.lastname: Giavaresi
authors.forename: Francesca
authors.initials: F
authors.lastname: Salamanna
authors.forename: Annapaola
authors.initials: A
authors.lastname: Parrilli
authors.forename: Elena
authors.initials: E
authors.lastname: Serchi
authors.forename: Daniele
authors.initials: D
authors.lastname: Pressato
authors.forename: Elena
authors.initials: E
authors.lastname: Arcangeli
authors.forename: Milena
authors.initials: M
authors.lastname: Fini
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001861:Bone Regeneration; D017886:Durapatite; D005260:Female; D006245:Hardness Tests; D016348:Osseointegration; D016062:Porosity; D019919:Prosthesis Implantation; D012756:Sheep; D012886:Skull / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed
chemical_list: D001672:Biocompatible Materials; D017886:Durapatite