title: Frictional properties of the meniscus improve after scaffold-augmented repair of partial meniscectomy: a pilot study.
abstract: BACKGROUND
  To prevent further degeneration, it is desirable to fill a meniscal defect with a supportive scaffold that mimics the mechanics of native tissue. Degradable porous scaffolds have been used, but it is unclear whether the tissue that fills the site of implantation is mechanically adequate, particularly with respect to frictional performance.
  
  
  OBJECTIVE
  We therefore determined the frictional behavior of native and engineered meniscal replacement tissue from in vivo implantation over time.
  
  
  METHODS
  We evaluated boundary and mixed-mode friction coefficients of tissue generated in porous polyurethane scaffolds used to augment the repair of the meniscus of 13 skeletally mature sheep after partial meniscectomy. Implants were removed for evaluation at 3, 6, and 12 months. The friction coefficient, aggregate modulus, and hydraulic permeability were evaluated for tissue harvested from native meniscus adjacent to the implants, native meniscus from the intact contralateral knee, and repair tissue from the site of the scaffold implantation. The equilibrium friction coefficient (μ(eq)) was measured in the presence of a lubricant bath of either phosphate-buffered saline (PBS) or equine synovial fluid (ESF).
  
  
  RESULTS
  Boundary μ(eq) in PBS of engineered meniscus improved with time and was similar to native tissue after 6 months. ESF enhanced lubrication for all samples at nearly all time points demonstrating the efficacy of ESF as a joint lubricant for repair tissue as well as native meniscus. Modulus increased and permeability decreased with implantation, likely as a result of tissue ingrowth.
  
  
  CONCLUSIONS
  Promoting tissue ingrowth into porous scaffolds is a potential strategy for improving friction performance in meniscal repair.
authors.affiliation: Cornell University, 149 Weill Hall, Ithaca, NY 14853, USA.
authors.forename: Natalie K
authors.initials: NK
authors.lastname: Galley
authors.forename: Jason P
authors.initials: JP
authors.lastname: Gleghorn
authors.forename: Scott
authors.initials: S
authors.lastname: Rodeo
authors.forename: Russell F
authors.initials: RF
authors.lastname: Warren
authors.forename: Suzanne A
authors.initials: SA
authors.lastname: Maher
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Bonassar
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D017276:Friction; D008592:Menisci, Tibial / Q000473:pathology / Q000601:surgery*; D023421:Models, Animal; D010865:Pilot Projects; D011140:Polyurethanes / Q000737:chemistry*; D016062:Porosity; D012038:Regeneration; D012756:Sheep; D013582:Synovial Fluid; D013997:Time Factors; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds
chemical_list: D001672:Biocompatible Materials; D011140:Polyurethanes