title: Analysis of cartilage tissue on a cellular level in fresh osteochondral allograft retrievals.
abstract: BACKGROUND
  Fresh human osteochondral allografting is a biological cartilage replacement technique used to treat articular and osteoarticular defects in the knee. A small number of grafts fail, and we analyzed every retrieved graft during a 4-year period in order to learn more about the potential causes of failure.
  
  
  OBJECTIVE
  A large percentage of chondrocytes still remain viable many years after fresh osteochondral allografting.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Retrieval specimens were obtained at the time of revision surgery and immediately analyzed. Chondrocyte viability and viable cell density were determined using a live/dead staining technique followed by confocal microscopy. Glycosaminoglycan content was a measure of the cartilage matrix. Radiolabeled sulfate uptake served as a biochemical marker of chondrocyte metabolic activity. Cartilage and subchondral bone were examined histologically.
  
  
  RESULTS
  Fourteen patients yielded a total of 26 retrieval specimens that had been originally implanted as individual fresh osteochondral allografts. Average graft survival was 42 months. Chondrocyte viability was 82% +/- 17%, and chondrocyte viable cell density was 15 590 +/- 5900 viable cells/mm(3). Retrieved tissue demonstrated radiolabeled sulfate uptake of 437 +/- 270 counts per minute and 3.5% +/- 0.8% hexosamine per dry weight. Histologically, all specimens showed some degree of cartilage fibrillation. There was evidence of bone allograft incorporation in most specimens, as well as pannus formation in 4 specimens, but no evidence of immune rejection.
  
  
  CONCLUSIONS
  A small percentage of fresh osteochondral allografts fail, but the precise cause is unknown. The main theories for failure investigated here include immunologic rejection, failure of bony incorporation, and chondrocyte death causing breakdown of the cartilage matrix. We show that chondrocytes remain viable many years after transplantation, allograft bone incorporates, and immune rejection does not seem to play a primary role in failure.
  
  
  CONCLUSIONS
  Fresh osteochondral allografting is becoming more common in the treatment of articular cartilage defects in the knee. Our findings support the paradigm of fresh osteochondral allografting, the transplantation of hyaline cartilage with biological incorporation of the underlying bone scaffold. The reasons for failure of a small percentage of grafts remain unclear.
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, 9500 Gilman Drive, Mail Code 0630, La Jolla, CA 92093-0630, USA.
authors.forename: Seth K
authors.initials: SK
authors.lastname: Williams
authors.forename: David
authors.initials: D
authors.lastname: Amiel
authors.forename: Scott T
authors.initials: ST
authors.lastname: Ball
authors.forename: R Todd
authors.initials: RT
authors.lastname: Allen
authors.forename: William L
authors.initials: WL
authors.lastname: Tontz
authors.forename: Bryan C
authors.initials: BC
authors.lastname: Emmerson
authors.forename: Neil M
authors.initials: NM
authors.lastname: Badlani
authors.forename: Shawn C
authors.initials: SC
authors.lastname: Emery
authors.forename: Parviz
authors.initials: P
authors.lastname: Haghighi
authors.forename: William D
authors.initials: WD
authors.lastname: Bugbee
mesh_terms: D000328:Adult; D000368:Aged; D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000502:physiology / Q000637:transplantation; D002470:Cell Survival / Q000502:physiology; D019902:Chondrocytes / Q000502:physiology*; D005260:Female; D006084:Graft Rejection / Q000473:pathology / Q000503:physiopathology*; D006085:Graft Survival / Q000502:physiology*; D006801:Humans; D007718:Knee Injuries / Q000601:surgery; D007719:Knee Joint / Q000473:pathology / Q000502:physiology* / Q000601:surgery; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D012086:Reoperation; D013431:Sulfates; D013462:Sulfur Radioisotopes; D014184:Transplantation, Homologous; D019737:Transplants; D017211:Treatment Failure
chemical_list: D013431:Sulfates; D013462:Sulfur Radioisotopes