title: Chronic changes in rabbit retro-patellar cartilage and subchondral bone after blunt impact loading of the patellofemoral joint.
abstract: Animal models of acute joint injury are useful for study of changes in joint tissues that may eventually lead to degradative disease. Our laboratory has developed a joint trauma model using a single blunt impact to the patellofemoral joint of rabbits and documented softening of retro-patellar cartilage and thickening of its underlying bone out to 12 months post-trauma. In the present study, we examined changes in these joint tissues out to 36 months post-impact. Forty-nine Flemish giant rabbits were impacted on the right patellofemoral joint and sacrificed at one of six times: 0, 4.5, 7.5, 12, 24, and 36 months post-impact. A 30% reduction in the compressive modulus of traumatized retro-patellar cartilage occurred at 4.5 months versus the contralateral, non-impacted limb and remained at this reduced level out to 36 months. The fluid permeability of traumatized cartilage also increased over time from baseline and versus the non-impacted limb. Tissue thickness increased slightly at 4.5 months and then decreased over time to a 45% difference from baseline at 36 months post-trauma. While impacted cartilage revealed a significantly greater length of surface fissuring than contralateral, non-impacted cartilage, no time-dependent changes were evident in this study. Moreover, the number and depth of these impact surface lesions did not change as a function of time. Finally, the histological analyses indicated that the thickness of underlying subchondral bone increased over time from baseline and versus that in the non-impacted limb. This long-term study suggested an association between a decrease in the characteristic time constant of traumatized cartilage and thickening of the underlying subchondral bone. Any potential cause and effect relationship, however, must be investigated in future studies.
authors.affiliation: Orthopaedic Biomechanics Laboratories, College of Osteopathic Medicine, Michigan State University, East Lansing 48824, USA.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Ewers
authors.forename: Brian T
authors.initials: BT
authors.lastname: Weaver
authors.forename: Eric T
authors.initials: ET
authors.lastname: Sevensma
authors.forename: Roger C
authors.initials: RC
authors.lastname: Haut
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001826:Body Fluids / Q000378:metabolism; D002358:Cartilage, Articular / Q000473:pathology* / Q000503:physiopathology; D007718:Knee Injuries / Q000473:pathology* / Q000503:physiopathology; D007719:Knee Joint / Q000473:pathology* / Q000503:physiopathology; D010539:Permeability; D011817:Rabbits; D013997:Time Factors; D014949:Wounds, Nonpenetrating / Q000473:pathology* / Q000503:physiopathology