How ‘debris’ from joint replacements causes pain

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Researchers have discovered why many people with joint replacements experience harmful inflammation and bone loss.

The findings could lead to new therapies to prevent pain and the need for follow-up surgeries.

As many as 15 percent of joint replacements will fail, which can require revision surgery to replace the implant.

Prosthetic devices can release microparticles—known as “wear debris”—that promote inflammation, and can lead to pain, bone tissue disappearance, implant loosening, and ultimately failure of the implant to affix to the bone.

But, until now, the specific pathways through which these particles promote inflammation were not clear.

Researchers discovered that white blood cells, called macrophages, respond to the particles as if they were harmful invaders and engulf them. The cells then die, and secrete a specific molecule that triggers an even stronger immune response—including inflammation which can cause tissue damage and bone destruction which leads to loosening of the implants.

“Bone degradation can occur within 10 to 15 years and often requires complex revision surgery to replace the implant and treat bone loss,” says lead author William Gause, director of the Center for Immunity and Inflammation at Rutgers New Jersey Medical School.

“However, many people start experiencing pain from this inflammation shortly after surgery. They are prescribed medications for the pain, but the loosening continues.”

Researchers can use the findings to identify ways to regulate the inflammation and bone degradation associated with these released particles, potentially without harming components of the patient’s immune response needed for protection against infectious pathogens, Gause says.

More generally, the study reveals new insights into how inert and sterile microparticles, including pollutants such as diesel exhaust particles or silica, can cause robust and harmful inflammation, ultimately leading to disease, Gause says.

“Although we typically think of infectious agents or toxins as causing disease, apparently the response of the body to these particles, which have essentially no intrinsic activities, can result in considerable tissue damage and pathology.”

The study appears in Nature Materials.

Source: Rutgers University