title: Effect on tissue differentiation and articular cartilage degradation of a polymer meniscus implant: A 2-year follow-up study in dogs.
abstract: BACKGROUND
  Replacement of the meniscus by an implant could potentially avoid cartilage degeneration.
  
  
  OBJECTIVE
  An implant of degradable polycaprolacton-polyurethane should act as a temporary scaffold enabling regeneration of a new meniscus by slow degradation of the polymer and simultaneous in-growth and differentiation of tissues into the typical cartilage-like tissue of the meniscus.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  In 13 dogs' knees, the lateral meniscus was replaced with a porous polymer implant (6 and 7 for 6- and 24-month follow-up, respectively); in 7 knees only a meniscectomy was performed. In 6 knees, no surgery was performed. After 6 and 24 months, the implants and the articular cartilage were histologically evaluated. Compression-stress tests were performed on implant biopsy specimens.
  
  
  RESULTS
  The implants were fully integrated into the tissue without formation of a capsule. The foreign body reaction did not exceed grade I. Differentiation from fibrous- to cartilage-like tissue was pronounced after 24 months. Viable cells were particularly absent after 24 months in central parts of the most anterior part of the scaffold. The mechanical properties of the implants were intermediate between the scaffold before implantation and native meniscus tissue and were not different between 6 and 24 months. After both 6 and 24 months, small areas of the implant were not covered with tissue. Cartilage degeneration was not prevented.
  
  
  CONCLUSIONS
  A final remodeling of tissue into neomeniscus tissue could not take place since the original structure of the polymer was still present after 24 months. The implant did not prevent cartilage degradation. Several factors are discussed that may be responsible for this.
  
  
  CONCLUSIONS
  Although clinical application of a polymer implant for the replacement of the entire meniscus is not supported by this study, the authors strongly believe in the concept, but further improvements in the implant and surgical technique are needed before such an implant can be recommended for human clinical use.
authors.affiliation: Orthopaedic Research Laboratory, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands.
authors.forename: Roy T C
authors.initials: RT
authors.lastname: Welsing
authors.forename: Tony G
authors.initials: TG
authors.lastname: van Tienen
authors.forename: Navin
authors.initials: N
authors.lastname: Ramrattan
authors.forename: Ralf
authors.initials: R
authors.lastname: Heijkants
authors.forename: Arend Jan
authors.initials: AJ
authors.lastname: Schouten
authors.forename: René P H
authors.initials: RP
authors.lastname: Veth
authors.forename: Pieter
authors.initials: P
authors.lastname: Buma
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000009:adverse effects; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000187:drug effects* / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D004285:Dogs; D005260:Female; D005500:Follow-Up Studies; D005549:Foreign-Body Reaction / Q000473:pathology; D020007:Implants, Experimental; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology / Q000601:surgery*; D011091:Polyesters / Q000009:adverse effects; D011140:Polyurethanes / Q000009:adverse effects; D019919:Prosthesis Implantation; D054457:Tissue Scaffolds / Q000009:adverse effects*
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters; D011140:Polyurethanes; C016240:polycaprolactone