title: Cartilage surface characterization by frictional dissipated energy during axially loaded knee flexion--an in vitro sheep model.
abstract: Cartilage defects and osteoarthritis (OA) have an increasing incidence in the aging population. A wide range of treatment options are available. The introduction of each new treatment requires controlled, evidence based, histological and biomechanical studies to identify potential benefits. Especially for the biomechanical testing there is a lack of established methods which combine a physiologic testing environment of complete joints with the possibility of body-weight simulation. The current in-vitro study presents a new method for the measurement of friction properties of cartilage on cartilage in its individual joint environment including the synovial fluid. Seven sheep knee joints were cyclically flexed and extended under constant axial load with intact joint capsule using a 6° of freedom robotic system. During the cyclic motion, the flexion angle and the respective torque were recorded and the dissipated energy was calculated. Different mechanically induced cartilage defect sizes (16 mm², 50 mm², 200 mm²) were examined and compared to the intact situation at varying levels of the axial load. The introduced setup could significantly distinguish between most of the defect sizes for all load levels above 200 N. For these higher load levels, a high reproducibility was achieved (coefficient of variation between 4% and 17%). The proposed method simulates a natural environment for the analysis of cartilage on cartilage friction properties and is able to differentiate between different cartilage defect sizes. Therefore, it is considered as an innovative method for the testing of new treatment options for cartilage defects.
authors.affiliation: Department of Orthopaedic Surgery, University Hospital Tübingen, Hoppe-Seyler-Straße 3, 72076 Tübingen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Lorenz
authors.forename: Stephan
authors.initials: S
authors.lastname: Rothstock
authors.forename: Evgenij
authors.initials: E
authors.lastname: Bobrowitsch
authors.forename: Alexander
authors.initials: A
authors.lastname: Beck
authors.forename: Gerhard
authors.initials: G
authors.lastname: Gruhler
authors.forename: Ingmar
authors.initials: I
authors.lastname: Ipach
authors.forename: Ulf G
authors.initials: UG
authors.lastname: Leichtle
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Wülker
authors.forename: Christian
authors.initials: C
authors.lastname: Walter
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002356:Cartilage / Q000502:physiology*; D006614:Hindlimb; D007596:Joints / Q000502:physiology*; D016059:Range of Motion, Articular; D012756:Sheep; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology