Bone marrow edema is seen in osteoarthritis, avascular necrosis, and other clinical conditions including the bone marrow edema syndrome. Bone marrow edema is associated with bone pain and may be related to the pathophysiology of osteoarthritis. Our hypothesis is that bone marrow edema is associated with a reduction in perfusion in subchondral bone, which contributes to focal and segmental bone necrosis and cartilage breakdown. We further hypothesize that altered fluid dynamics in subchondral bone comprise part of the physicochemical environment to which osteocytes are highly sensitive and alter their cytokine expression profile in response to changes in fluid flow, pressure, and oxygen gradients. We have used contrast-enhanced magnetic resonance imaging with Gd-DTPA to characterize changes in subchondral bone perfusion in two relevant and related models-the Dunkin-Hartley guinea pig model of osteoarthritis and human bone marrow edema associated with osteoarthritis and avascular necrosis. Pharmacokinetic modeling was used to extract dynamic parameters of perfusion. Representative time-intensity curves are derived, which characterize normal bone and bone with marrow edema. Dynamic contrast-enhanced magnetic resonance imaging may be a useful tool for the early diagnosis of bone perfusion abnormalities and may be used to characterize marrow edema associated with a number of clinical conditions. This technique may also shed light on the pathophysiology of subchondral perfusion in osteoarthritis and avascular necrosis.

Osteoarthritis and avascular necrosis are common clinical entities with unknown etiologies. Recently, vascular changes have been implicated in the pathogenesis of both conditions. This review discusses the use of novel non-invasive imaging techniques, using dynamic contrast-enhanced magnetic resonance imaging, as a means of assessing bone perfusion and therefore quantifying differences seen in both osteoarthritis and avascular necrosis. We have found changes in fluid dynamics in both osteoarthritis and avascular necrosis as compared to normal bone as well as changes between osteoarthritis and avascular necrosis. Review of our human data suggest that the magnetic resonance imaging contrast dye is retained for longer periods of time, suggesting decreased perfusion out of regions of osteoarthritis and avascular necrosis. This finding was corroborated in a guinea-pig animal model of osteoarthritis. Use of such a non-invasive measure of assessing bone perfusion could be useful in the diagnosis, prevention, and treatment of not only osteoarthritis and avascular necrosis but many other entities that affect the musculoskeletal system.