3-D T 1 relaxation time measurements in an equine model of subtle post-traumatic osteoarthritis using MB-SWIFT.

To assess whether articular cartilage changes in an equine model of post traumatic osteoarthritis (PTOA), induced by surgical creation of standard (blunt) grooves, and very subtle sharp grooves, could be detected with ex vivo T 1 relaxation time mapping utilizing 3-D readout sequence with zero echo time. Grooves were made on the articular surfaces of the middle carpal and radiocarpal joints of nine mature Shetland ponies, and osteochondral samples were harvested at 39 weeks after being euthanized under respective ethical permissions. T 1 relaxation times of the samples (n = 8+8 for experimental and n = 12 for contralateral controls) were measured with a variable flip angle (VFA) 3-D multiband (MB) SWIFT sequence. Equilibrium and Instantaneous Young's moduli and proteoglycan (PG) content from optical density (OD) of Safranin-O-stained histological sections, were measured and utilized as reference parameters for the T 1 relaxation times. T 1 relaxation time was significantly (p<0.05) increased in both groove areas, particularly in the blunt grooves, compared to control samples, with the largest changes observed in the superficial half of the cartilage. T 1 relaxation times correlated weakly (R s ≈0.33) with equilibrium modulus and PG content (R s ≈0.21). T 1 relaxation time in the superficial articular cartilage is sensitive to changes induced by the blunt grooves, but not to the much subtler sharp grooves, at the 39-week time-point post-injury. These findings support that T 1 relaxation time has potential in detection of mild PTOA, albeit the most subtle changes could not be detected. This article is protected by copyright. All rights reserved.