title: Biocompatibility and implantation properties of 2 differently braided, biodegradable, self-reinforced polylactic acid urethral stents: an experimental study in the rabbit.
abstract: OBJECTIVE
  Biodegradable urethral stents have been in clinical use for more than 10 years. To solve the problems connected with the helical spiral configuration of the stents used to date we developed a new tubular mesh configuration and evaluated the biocompatibility properties and degradation time of 2 differently braided stents in the rabbit urethra.
  
  
  METHODS
  The biodegradable, self-expanding stents were made of self-reinforced polylactic acid polymer blended with BaSO4 (Alfa Chem, Kings Point, New York). Two braiding patterns, namely a diamond 1/1 and a regular 2/2 + 1 (Prodesco, Perkasie, Pennsylvania), were used to produce a tubular mesh configuration. Stainless steel stents with 1/1 braiding served as controls. The stents were inserted into the posterior urethra of 36 male rabbits. The animals were sacrificed after 1 week, 1 month, 6 months or 12 months. Light microscopy and scanning electron microscopy analyses were done.
  
  
  RESULTS
  Tissue reactions to operative trauma were seen in all specimens at week 1. The changes gradually abated in the biodegradable stent groups, whereas chronic inflammatory changes and fibrosis were increasingly seen with metallic stents after 6 months. Epithelial hyperplasia increased with time for all stent types and materials. As expected, stent fragmentation started at 6 months.
  
  
  CONCLUSIONS
  Biodegradable polymers are suitable materials for braided urethral stents. However, the braided configuration of the stent with a decreased mass of material does not prevent the development of epithelial hyperplasia. The biodegradable, self-expanding, braided stents functioned well in the rabbit urethra and are suitable for clinical studies.
authors.affiliation: Department of Surgery, Päijät-Häme Central Hospital, Keskussairaalankatu 7, 15850 Lahti, Finland. taina.isotalo@phks.fi
authors.forename: Taina
authors.initials: T
authors.lastname: Isotalo
authors.forename: Juha-Pekka
authors.initials: JP
authors.lastname: Nuutinen
authors.forename: Anu
authors.initials: A
authors.lastname: Vaajanen
authors.forename: Paula M
authors.initials: PM
authors.lastname: Martikainen
authors.forename: Marita
authors.initials: M
authors.lastname: Laurila
authors.forename: Pertti
authors.initials: P
authors.lastname: Törmälä
authors.forename: Martti
authors.initials: M
authors.lastname: Talja
authors.forename: Teuvo L J
authors.initials: TL
authors.lastname: Tammela
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation; D020099:Coated Materials, Biocompatible / Q000008:administration & dosage*; D005355:Fibrosis; D005500:Follow-Up Studies; D019344:Lactic Acid / Q000008:administration & dosage*; D008297:Male; D023421:Models, Animal; D011091:Polyesters; D011108:Polymers / Q000008:administration & dosage*; D011817:Rabbits; D015607:Stents; D013997:Time Factors; D014521:Urethra / Q000187:drug effects* / Q000473:pathology / Q000601:surgery*
chemical_list: D020099:Coated Materials, Biocompatible; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)