Effect of mechanical convection on the partitioning of an anionic iodinated contrast agent in intact patellar cartilage

Abstract

To determine if mechanical convection accelerates partitioning of an anionic contrast agent into cartilage while maintaining its ability to reflect the glycosaminoglycan (GAG) content in contrast-enhanced computed tomography (CECT) of cartilage. Bovine patellae (N=4) were immersed in iothalamate and serially imaged over 24h of passive diffusion at 34C. Following saline washing for 14h, each patella was serially imaged over 2.5h of mechanical convection by cyclic compressive loading (120N, 1Hz) while immersed in iothalamate at 34C. After similar saline washing, each patella was sectioned into 15 blocks (n=60) and contrast concentration per time point as well as GAG content were determined for each cartilage block. Mechanical convection produced 70.6%, 34.4%, and 16.4% higher contrast concentration at 30, 60, and 90min, respectively, compared to passive diffusion (p<0.001) and boosted initial contrast flux 330%. The correlation between contrast concentration and GAG content was significant at all time points and correlation coefficients improved with time, reaching R 2=0.60 after 180min of passive diffusion and 22.5min of mechanical convection. Mechanical convection significantly accelerated partitioning of a contrast agent into healthy cartilage while maintaining strong correlations with GAG content, providing an evidence-based rationale for adopting walking regimens in CECT imaging protocols. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1333-1340, 2014. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.