Study: High rate of hip resurfacing wear associated with pseudotumors
In this study, researchers from the United Kingdom concluded the
majority of pseudotumors seen in patients with failed metal-on-metal hip
resurfacing implants are due to implant wear.
“This increased wear is associated with soft tissue necrosis and a
heavy nonspecific foreign-body macrophage response coupled with a
variable adaptive or specific immune response,” David W. Murray, FRCS(Orth),
and colleagues wrote in the study abstract. “A minority of pseudotumors
are associated with low wear and a prominent immune response.”
Murray and colleagues examined 56 metal-on-metal hip resurfacing
implants – 45 cases had a symptomatic tumor as the reason for failure,
according to the abstract. They found that 80% of tumors were from a
“highly worn” implant and substantial necrosis and a heavy macrophage
infiltrate was present in most periprosthetic soft tissue. They also
noted aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
infiltrate in many patients. However, even low wear was correlated with a
strong ALVAL infiltrate response, according to the abstract.
“These findings confirm that minimizing wear from metal-on-metal hip
resurfacing arthroplasty prostheses would lead to a reduction in the
incidence of pseudotumor,” the authors wrote. “However, a small number
of pseudotumors are still likely to occur, which may be due to an
exacerbated adaptive immune response.”
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