Detection of mechanical injury of articular cartilage using contrast enhanced computed tomography

Osteoarthritic degeneration may be initiated by mechanical overloading of articular cartilage. Mechanical injury increases the permeability of tissue, thereby probably affecting the diffusion of contrast agents in articular cartilage. We investigated whether it is possible to detect acute cartilage injury by measuring contrast agent diffusion into articular cartilage using contrast enhanced computed tomography (CECT).

Osteochondral plugs (Ø=6.0 mm, n=36) were prepared from intact bovine patellae (n=9). Two of the adjacent samples were injured by impact loading, using a drop tower, while the others served as paired controls. The samples were imaged before immersion in contrast agent solution [ioxaglate (Hexabrix™) or sodium iodide (NaI)] and 1, 3, 5, 7, 10, 15, 20 and 25 h after immersion using a MicroCT-instrument. Contrast agent content, diffusion coefficient and diffusion flux were determined for each sample.

Already after 1 h the penetration of contrast agents into cartilage was significantly (P<0.05) greater in the injured samples. The diffusion coefficient was not altered by the injury, which suggests that reaching the diffusion equilibrium takes the same time in injured and intact cartilage. However, the diffusion flux of ioxaglate through the articular surface was significantly higher in injured samples at 30-60 min after immersion.

To conclude, CECT could diagnose articular cartilage injuries, and determination of the diffusion flux of ioxaglate helped to detect tissue injury without waiting for the diffusion equilibrium. These results are encouraging, however, in vivo application of CECT is challenging and systematic further studies are needed to reveal its clinical potential.