A novel approach to observing articular cartilage deformation in vitro viamagnetic resonance imaging

The design of a pressure cell that compresses a cartilage specimen in one d imension within an imaging magnet is presented, One-dimensional projection images in a direction perpendicular to the articular surface of the cartila ge specimen were used to generate a uniaxial confined deformation creep cur ve for normal and trypsin-degraded cartilage specimens during a continuous 0.690 MPa (100 psi) pressure application, The resulting curves are shown to fft a two time constant viscoelastic model well and also indicate that the elastic modulus of cartilage decreases and the deformation rate increases upon trypsin proteolysis, Furthermore, cartilage permeability is shown as a function of cartilage strain for both the normal and trypsin-degraded case . Several two-dimensional slice-selective images were collected both before and after 80 minutes of continuous compression. These images were used to evaluate the relative changes in the spin-lattice, T1, and spin-spin, T2, r elaxation time constant maps for both normal and degraded cartilage specime ns in response to compression. The results of this study demonstrate the ut ility of a novel, non-magnetic, cartilage compression device and also suppo rt the validity of a simple two-component rheological model of articular ca rtilage. (C) 1999 Wiley-Liss, Inc.