title: Osseous metaplasia with functioning bone marrow in hydroxyapatite orbital implants.
abstract: BACKGROUND
  Bone formation within the hydroxyapatite implant has been reported in explanted spheres in humans. Bone-specific differentiation was observed to occur earlier in the pores of spherical hydroxyapatite implants enhanced with osteogenin within the rabbit socket. We observed previously unreported bone marrow formation in a coralline hydroxyapatite implant placed into the rabbit orbit after evisceration.
  
  
  METHODS
  One eye of each of 10 New Zealand white rabbits weighing between 2 and 3 kg was eviscerated and implanted with hydroxyapatite spheres. The explanted hydroxyapatite spheres 20 weeks after surgery were examined under the microscope.
  
  
  RESULTS
  Histopathologic examination of the excised implants showed the presence of trabeculae of mature bone with fatty marrow and hematopoietic elements. Scattered throughout the fatty tissue were bone marrow elements consisting of precursors of the granulocytic and erythroid series and also megakaryocytes.
  
  
  CONCLUSIONS
  The osseous metaplasia with functioning bone marrow was incidentally observed in the coralline hydroxyapatite implant without the addition of any osteogenesis-inducing agents.
authors.affiliation: Department of Ophthalmology, Institute of Vision Research, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: H
authors.initials: H
authors.lastname: Lew
authors.forename: D H
authors.initials: DH
authors.lastname: Shin
authors.forename: S Y
authors.initials: SY
authors.lastname: Lee
authors.forename: S J
authors.initials: SJ
authors.lastname: Kim
authors.forename: J W
authors.initials: JW
authors.lastname: Jang
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001846:Bone Development; D001853:Bone Marrow / Q000502:physiology*; D001854:Bone Marrow Cells / Q000166:cytology* / Q000502:physiology; D001842:Bone and Bones / Q000473:pathology*; D017234:Eye Evisceration; D006882:Hydroxyapatites; D008679:Metaplasia; D020273:Orbital Implants; D010012:Osteogenesis; D011817:Rabbits
chemical_list: D001672:Biocompatible Materials; D006882:Hydroxyapatites