title: Dynamic impact force and association with structural damage to the knee joint: an ex-vivo study.
abstract: No systematic, histologically confirmed data are available concerning the association between magnitude of direct dynamic impact caused by vertical impact trauma and the resulting injury to cartilage and subchondral bone. The aim of this study was to investigate the association between dynamic impact and the resulting patterns of osteochondral injury in an ex-vivo model. A mechanical apparatus was employed to perform ex-vivo controlled dynamic vertical impact experiments in 110 pig knees with the femur positioned in a holding fixture. A falling body with a thrust plate and photo sensor was applied. The direct impact to the trochlear articular surface was registered and the resulting osteochondral injuries macroscopically and histologically correlated and categorized. The relationship between magnitude of direct impact and injury severity could be classified as stage I injuries (impact <7.3MPa): elastic deformation, no histological injury; stage II injuries (impact 7.3-9.6MPa): viscoelastic imprint of the cartilaginous surface, subchondral microfractures; stage III injuries (impact 9.6-12.7MPa): disrupted cartilage surface, chondral fissures and subchondral microfractures; stage IV injuries (impact >12.7MPa): osteochondral impression, histologically imprint and osteochondral macrofractures. The impact ranges and histologic injury stages determined from this vertical dynamic impact experiment allowed for a biomechanical classification of direct, acute osteochondral injury. In contrast to static load commonly applied in ex-vivo experiments, dynamic impact more realistically represents actual trauma to the knee joint.
authors.affiliation: Department of Radiology, Klinikum Augsburg, Augsburg, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Brill
authors.affiliation: Department of Radiology, University of Regensburg, Regensburg, Germany.
authors.forename: Walther A
authors.initials: WA
authors.lastname: Wohlgemuth
authors.affiliation: Berufsgenossenschaftliche Unfallklinik, Murnau, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Hempfling
authors.affiliation: MR Center of Excellence, Department of Radiology, University of Vienna, Vienna, Austria.
authors.forename: Klaus
authors.initials: K
authors.lastname: Bohndorf
authors.affiliation: F. Hoffmann-La Roche Ltd., Basel, Switzerland.
authors.forename: Ursula
authors.initials: U
authors.lastname: Becker
authors.affiliation: Department of Cell Biology, Ludwigs-Maximilians University, Munich, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Welsch
authors.affiliation: Center for Radiology and Nuclear Medicine, Murnau, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kamp
authors.affiliation: Department of Radiology, University of Erlangen-Nuremberg, Erlangen, Germany; Department of Radiology, Klinikum Augsburg, Augsburg, Germany. Electronic address: frank.roemer@uk-erlangen.de.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Roemer
mesh_terms: D000054:Acceleration; D000058:Accidental Falls; D000818:Animals; D066298:In Vitro Techniques; D007718:Knee Injuries / Q000473:pathology* / Q000503:physiopathology*; D007719:Knee Joint / Q000473:pathology* / Q000503:physiopathology*; D013314:Stress, Mechanical; D013552:Swine; D014949:Wounds, Nonpenetrating / Q000473:pathology* / Q000503:physiopathology*
keywords: Dynamic impact; Histology; Knee; Osteochondral injury