title: The Biological Response following Autogenous Bone Grafting for Large-Volume Defects of the Knee: Index Surgery through 12 to 21 Years' Follow-up.
abstract: OBJECTIVE
  This report focuses on the biological events occurring at various intervals following autogenous bone grafting of large-volume defects of the knee joint's femoral condyle secondary to osteochondritis dissecans (OCD) or osteonecrosis (ON). It was hypothesized that the autogenous bone graft would integrate and the portion exposed to the articular surface would form fibrocartilage, which would endure for years.
  
  
  METHODS
  Between September 29, 1987 and August 8, 1994, there were 51 patients treated with autogenous bone grafting for large-volume osteochondral defects. Twenty-five of the 51 patients were available for long-term follow-up up to 21 years. Patient follow-up was accomplished by clinical opportunity and intentional research. Videotapes were available on all index surgeries for review and comparison. All had preoperative and postoperative plain film radiographs. Long-term follow-up included MRI up to 21 years. Second-look arthroscopy and biopsy were obtained on 14 patients between 8 weeks and 20 years.
  
  
  RESULTS
  Radiological assessment showed the autogenous bone grafts integrated with the host bone. The grafts retained the physical geometry of the original placement. MRI showed soft tissue covering the grafts in all cases at long-term follow-up. Interval biopsy showed the surface covered with fibrous tissue at 8 weeks and subsequently converted to fibrocartilage with hyaline cartilage at 20 years.
  
  
  CONCLUSIONS
  Autogenous bone grafting provides a matrix for large osteochondral defects that integrates with the host bone and results in a surface repair of fibrocartilage and hyaline cartilage that can endure for up to 20 years.
authors.affiliation: Okemos, MI, USA.
authors.forename: Lanny L
authors.initials: LL
authors.lastname: Johnson
authors.affiliation: Department of Radiology, College of Human Medicine, Michigan State University, East Lansing, MI, USA.
authors.forename: Mark C
authors.initials: MC
authors.lastname: DeLano
authors.affiliation: Tissue Engineering, VA Boston Healthcare System, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Myron
authors.initials: M
authors.lastname: Spector
authors.affiliation: Tissue Engineering, VA Boston Healthcare System, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA ; Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Lily
authors.initials: L
authors.lastname: Jeng
authors.affiliation: Okemos, MI, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Pittsley
authors.affiliation: Department of Radiology, College of Human Medicine, Michigan State University, East Lansing, MI, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gottschalk
keywords: articular cartilage < tissue; biopsy < research methods; histology: staining < research methods; knee < joint involved; magnetic resonance imaging < diagnostics