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Titanium Debris May Cause Inflammation of Artificial Joints
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MANY PEOPLE WITH PAINFUL‚ creaky knees and hips find relief after replacing their bad joints with new artificial joints made from titanium. But some of them develop painful inflammation that can lead to bone destruction and loosening of the new joint. A study led by researchers at NJMS and published by the Journal of Immunology suggests that tiny titanium particles that flake away from the artificial joints through normal wear and tear may play a direct role in that inflammation.
Prior studies have suggested that inflammation is caused by bits of bacteria that stick to dislodged titanium particles and activate an immune response. But Pankaj Mishra in the laboratory of William Gause‚ PhD‚ NJMS senior associate dean and director‚ Center for Immunity and Inflammation‚ in collaboration with Joseph Benevenia‚ MD‚ chair‚ Department of Orthopaedics‚ found that titanium particles themselves trigger inflammation in mice.
The type of inflammatory response that ensued when titanium particles were introduced — known as a Th2 response — is typically associated with allergic responses and parasitic worm infections and results in the generation of immune cells called alternatively activated macrophages (AAMs). The immune system thus responds to these "inert" micron–sized particles as if they were allergens or invading multicellular parasites. The potential effects of a Th2 response in the joint are not completely clear‚ but there is increasing evidence that AAMs contribute to bone destruction in prosthesis recipients and in patients with certain types of arthritis.