title: Meniscal allograft transplantation in the sheep knee: evaluation of chondroprotective effects.
abstract: BACKGROUND
  Early protection of articular cartilage, before degenerative changes appear on radiographs, should result in better long-term results, but scientific evidence regarding the effectiveness of meniscal transplantation is lacking.
  
  
  OBJECTIVE
  To assess the chondroprotective effects of a new meniscal allograft transplantation animal model and evaluate a magnetic resonance imaging parameter, T2 mapping, in articular cartilage after meniscectomy and meniscal transplantation.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Forty-five skeletally mature sheep were placed into 3 surgical groups: lateral meniscectomy (n = 24), meniscal allograft transplant (n = 17), and sham (n = 4). Animals were sacrificed at 2, 4, or 12 months. Cartilage was assessed by gross inspection, magnetic resonance imaging, T2 mapping, biomechanical testing, and semiquantitative histologic analysis.
  
  
  RESULTS
  There were no differences between the sham operation and nonoperated control limbs. Compared with control limbs, meniscectomy resulted in significant increases in cartilage degeneration by all objective criteria (P < .01). Compared with meniscectomy, meniscal allograft transplantation resulted in significant decreases in cartilage degeneration (P < .02). There were significant correlations between T2-mapping data and all other traditional outcomes measures (P < .05, r(2) = 0.37-0.67). Compared with the nonoperated control limbs, allograft transplants demonstrated no significant differences at 2 months in any category, except magnetic resonance imaging data. By 4 months, nonoperated control limbs demonstrated significantly less wear compared to allograft limbs in all categories except modified Mankin scores.
  
  
  CONCLUSIONS
  This model demonstrated significant chondroprotection compared with meniscectomy but demonstrated more cartilage wear at 4 months compared to control limbs. A high degree of allograft cell viability and vascular ingrowth was seen in allograft explants. T2 mapping may provide an accurate noninvasive measure of early cartilage degeneration after meniscectomy, as well as cartilage protection after meniscal allograft transplantation.
  
  
  CONCLUSIONS
  This study establishes a reliable animal model for meniscal allograft transplantation and provides evidence for the utility of T2 mapping at clinically relevant magnetic resonance imaging field strengths for evaluation of early cartilage degeneration.
authors.affiliation: Hospital for Special Surgery, New York, NY 10021, USA. kellyb@hss.edu
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Kelly
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
authors.forename: Xiang-Hua
authors.initials: XH
authors.lastname: Deng
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Pearle
authors.forename: A Simon
authors.initials: AS
authors.lastname: Turner
authors.forename: Russell F
authors.initials: RF
authors.lastname: Warren
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rodeo
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002470:Cell Survival; D005260:Female; D008279:Magnetic Resonance Imaging / Q000379:methods; D008592:Menisci, Tibial / Q000033:anatomy & histology / Q000503:physiopathology* / Q000637:transplantation*; D008859:Microscopy, Polarization; D023421:Models, Animal; D012720:Severity of Illness Index; D012756:Sheep; D014184:Transplantation, Homologous