Non-ionic CT Contrast Solutions Rapidly Alter Bovine Cartilage and Meniscus Mechanics

ObjectiveTo evaluate effects of a common CT contrast agent (iohexol) on the mechanical behaviors of cartilage and meniscus. MethodsIndentation responses of juvenile bovine cartilage and meniscus were monitored following exposure to undiluted contrast agent (100% CA), 50% CA/water, 50% CA/Phosphate Buffered Saline (PBS) or PBS alone, and during re-equilibration in PBS. The normalized peak force [Formula], effective osmotic strain ({varepsilon}osm), and normalized effective contact modulus [Formula] were calculated for every cycle, with time constants determined for both exposure and recovery via mono- or biexponential fits to [Formula]. ResultsAll cartilage CA groups exhibited long-term increases in [Formula] following exposure, although the hyperosmolal 100% CA and 50% CA/PBS groups showed an initial transient decrease. Meniscus presented opposing trends, with decreasing [Formula] for all CA groups. Re-equilibration in PBS for 1hr after exposure to 100% CA did not produce recovery to baseline [Formula] in either tissue. The recovery time for meniscus was substantially longer than that of cartilage. [Formula] increased with CA exposure time for cartilage but decreased for meniscus, suggesting an increased effective stiffness for cartilage and decreased stiffness for meniscus. Long-term changes to{varepsilon} osm in both tissues were consistent with changes in [Formula]. ConclusionExposure to iohexol solutions affected joint tissues differentially, with increased cartilage stiffness, likely relating to competing hyperosmotic and hypotonic interactions with tissue fixed charges, and decreased meniscus stiffness, likely dominated by hyperosmolarity. These altered tissue mechanics could allow non-physiological deformation during ambulatory weight-bearing, resulting in an increased risk of tissue or cell damage.