title: Hydrogel meniscal replacement in the sheep knee: preliminary evaluation of chondroprotective effects.
abstract: BACKGROUND
  Meniscal allograft transplantation has become a viable surgical alternative for a select group of patients with deficient or irreparable menisci. Subjective results are encouraging; long-term success, durability, and safety of allograft meniscal transplantation are uncertain.
  
  
  OBJECTIVE
  To evaluate a novel hydrogel meniscal replacement implant in an ovine model and assess chondroprotective effects of this hydrogel meniscal replacement using several validated outcome measures.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Fourteen skeletally mature sheep underwent hydrogel meniscal replacement; 45 additional animals had previously undergone 1 of 3 operations: lateral meniscectomy (24), meniscal allograft transplant (17), and sham (4). Animals were sacrificed at 2, 4, or 12 months. Cartilage was assessed by magnetic resonance imaging, gross inspection, biomechanical testing, and semiquantitative histological analysis.
  
  
  RESULTS
  There were no differences between the sham operation and nonoperated control limbs. Compared with meniscectomy, hydrogel meniscal replacement resulted in significantly decreased cartilage degeneration with all outcome parameters (P < .05). Compared with nonoperated control limbs, hydrogel meniscal replacements demonstrated no significant differences at 2 months in any category. By 4 months, hydrogel limbs demonstrated significantly greater cartilage degeneration than did nonoperated control limbs in all categories. Compared with meniscal allograft transplantation animals, hydrogel meniscal replacements demonstrated no differences at 2 months but had significantly increased cartilage degeneration in the peripheral zone of the tibial plateau at 4 months (P < .05). At 1 year, all hydrogel implants had developed complete radial splits in the posterior third of the implant.
  
  
  CONCLUSIONS
  Although promising preliminary results for hydrogel meniscal replacement were seen at early time points, significant cartilage degeneration and implant failure were seen at 1 year, and overall performance was worse than was allograft transplantation. Improvements in hydrogel material properties and surface characteristics and more accurate size matching may improve outcomes.
  
  
  CONCLUSIONS
  Improvements in the hydrogel material properties and surface characteristics and more accurate size matching may lead to the use of hydrogel implants in humans.
authors.affiliation: Hospital for Special Surgery, New York, NY 10021, USA. kellyb2847@hotmail.com
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Kelly
authors.forename: William
authors.initials: W
authors.lastname: Robertson
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
authors.forename: Xiang-Hua
authors.initials: XH
authors.lastname: Deng
authors.forename: A Simon
authors.initials: AS
authors.lastname: Turner
authors.forename: Stephen
authors.initials: S
authors.lastname: Lyman
authors.forename: Russell F
authors.initials: RF
authors.lastname: Warren
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rodeo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D007720:Knee Prosthesis; D008279:Magnetic Resonance Imaging; D008592:Menisci, Tibial / Q000601:surgery*; D034561:Sheep, Domestic; D018709:Statistics, Nonparametric
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate