title: An In Vivo Lapine Model for Impact-Induced Injury and Osteoarthritic Degeneration of Articular Cartilage.
abstract: OBJECTIVE
  In this study, we applied a spring-loaded impactor to deliver traumatic forces to articular cartilage in vivo. Based on our recent finding that a 0.28-J impact induces maximal catabolic response in adult bovine articular cartilage in vitro using this device, we hypothesize that this impact will induce the formation of a focal osteoarthritic defect in vivo.
  
  
  METHODS
  The femoral condyle of New Zealand White rabbits was exposed and one of the following procedures performed: 0.28 J impact, anterior cruciate ligament transection, articular surface grooving, or no joint or cartilage destruction (control). After 24 hours, 4 weeks, or 12 weeks (n = 3 for each time point), wounds were localized with India ink, and tissue samples were collected and characterized histomorphometrically with Safranin O/Fast green staining and Hoechst 33342 nuclear staining for cell vitality.
  
  
  RESULTS
  The spring-loaded device delivered reproducible impacts with the following characteristics: impact area of 1.39 ± 0.11 mm(2), calculated load of 326 ± 47.3 MPa, time-to-peak of 0.32 ± 0.03 ms, and an estimated maximal displacement of 25.1% ± 4.5% at the tip apex. The impact resulted in immediate cartilage fissuring and cell loss in the surface and intermediate zones, and it induced the formation of a focal lesion at 12 weeks. The degeneration was defined and appeared more slowly than after anterior cruciate ligament transection, and more pronounced and characteristic than after grooving.
  
  
  CONCLUSIONS
  A single traumatic 0.28 J impact delivered with this spring-loaded impactor induces focal cartilage degeneration characteristic of osteoarthritis.
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Alexander
authors.affiliation: Department of Orthopaedic Surgery, George Washington University, Washington, DC, USA.
authors.forename: Jesse A
authors.initials: JA
authors.lastname: McCarron
authors.affiliation: Department of Orthopaedic Surgery, George Washington University, Washington, DC, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Levine
authors.affiliation: Office of Science and Technology, National Institute of Arthritis, and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Melvin
authors.affiliation: Department of Orthopaedic Surgery, George Washington University, Washington, DC, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Murray
authors.affiliation: Department of Orthopaedic Surgery, George Washington University, Washington, DC, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Manner
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Rocky S
authors.initials: RS
authors.lastname: Tuan
keywords: articular cartilage; cartilage degeneration; in vivo model; mechanical impact; osteoarthritis; trauma