The structural adaptations in compressed articular cartilage by microscopic MRI (μMRI) T2 anisotropy  Hisham A. Alhadlaq, M.S., Yang Xia, Ph.D.  Osteoarthritis and Cartilage  Volume 12, Issue 11, Pages 887-894 (November 2004) DOI: 10.1016/j.joca.2004.07.006 Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions

Fig. 1 The compression device, which was made completely out of nonmetallic, nonmagnetic materials, and can be incorporated inside the 5-mm NMR tube within the RF coil. (a) The device consists of a base for the specimen and a top layer that can be compressed against the cartilage surface with the help of micro fasteners. (b) A compressed cartilage–bone plug inside the NMR tube. Osteoarthritis and Cartilage 2004 12, 887-894DOI: (10.1016/j.joca.2004.07.006) Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions

Fig. 2 (a) T2-weighted proton images (at ∼0°) of control cartilage, at ∼12% and ∼22% strain. (b) Calculated T2 maps (at ∼0°) of control cartilage, at ∼12% and ∼22% strain. (c) T2-weighted proton images (at ∼55°) of control cartilage, at ∼12% and ∼22% strain. (d) Calculated T2 maps (at ∼55°) of control cartilage, at ∼12% and ∼22% strain. The images shown above are from the same sample at different stages. The numbered vertical lines on the side of control images in (a) and (b) correspond to the following: 1: saline, 2: cartilage, 3: bone, and 4: the plastic layer. T2 weighting for (a) and (c) was 16ms. The angle is defined as the angle between the normal to the articular surface of cartilage and the direction of the magnetic field (B0). Osteoarthritis and Cartilage 2004 12, 887-894DOI: (10.1016/j.joca.2004.07.006) Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions

Fig. 3 T2 profiles of a control sample with and without the top plastic layer at 0° and 55°. The plastic layer was touching the top of the cartilage sample with no compression force. Osteoarthritis and Cartilage 2004 12, 887-894DOI: (10.1016/j.joca.2004.07.006) Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions

Fig. 4 T2 profiles from one sample at three stages: control, compressed at ∼12%, and compressed at ∼22%. The graphs correspond to T2 profiles: (a) vs absolute depth at ∼0°; (b) vs relative depth at ∼0°; (c) vs absolute depth at ∼55°; and (d) vs relative depth at ∼55°. The error bars in graph (b) and (d) represent the variation in T2 when averaged within the selected region of interest in the middle of the specimen. The vertical lines in graph (b) demonstrate the shift of the middle of the transitional zone upon compression. Osteoarthritis and Cartilage 2004 12, 887-894DOI: (10.1016/j.joca.2004.07.006) Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions

Fig. 5 Changes in the ‘bulk’ T2 in cartilage as a function of the thickness reduction (strain) when the specimens were oriented approximately at 0° and 55° in the magnet. Osteoarthritis and Cartilage 2004 12, 887-894DOI: (10.1016/j.joca.2004.07.006) Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions

Fig. 6 Effect of compression on the thickness of individual zones. The left vertical axis represents the thickness percentage of superficial and transitional zone. The right vertical axis represents the thickness percentage of radial zone. T2 profiles from the control and compressed cartilage (at different strain values) were used to sub-divide the entire depth of tissue into three histological zones: (superficial, transitional, and radial zone). Each data point represents the percentage thickness of that particular zone over the entire thickness at the given strain value. The error bars represent the margin of error of determining the zone boundaries calculated from the standard deviation of each T2 profile. Osteoarthritis and Cartilage 2004 12, 887-894DOI: (10.1016/j.joca.2004.07.006) Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions

Fig. 7 A schematic model for the orientational adaptation of collage fibers across the cartilage depth as a result of mechanical compression based on T2 anisotropy data. Each solid line represents the overall orientation of the collagen fibrils at this particular depth in cartilage; these lines are numbered to track the changes in zone boundaries upon compression. The left figure (a) shows the three classical zones in uncompressed articular cartilage (SZ: superficial zone, TZ: transitional zone, and RZ: radial zone). The right figure (b) shows the orientational changes at different depths due to external loading in cartilage. Osteoarthritis and Cartilage 2004 12, 887-894DOI: (10.1016/j.joca.2004.07.006) Copyright © 2004 OsteoArthritis Research Society International Terms and Conditions