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Wear, metal hypersensitivity can lead to pseudotumor-like reactions
Campbell P. Clin Orthop Relat Res. 2010;468:2321-2327. doi:10.1007/s11999-010-1372-y.
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Study results implicate wear and metal hypersensitivity in the formation of pseudotumors.
Pat Campbell, PhD, of Orthopaedic Hospital/UCLA, Los Angeles, and colleagues studied tissue samples from 32 revised hip replacements with pseudotumor-like reactions.
The researchers examined the synovial lining integrity, inflammatory cell infiltrates and tissue organization of the samples. Then, using a 10-point histological score, they ranked the degree of aseptic lymphocytic vasculitis-associated lesions (ALVAL). They semiquantitatively rated lymphocytes, macrophages, plasma cells, giant cells, necrosis and metal wear particles, and they used a coordinate measuring machine to measure implant wear.
Based on clinical, radiographic and retrieval findings, the researchers then separated the cases into two groups: those suspected of having high wear and those suspected of having metal hypersensitivity. They compared histological features with the Mann-Whitney test.
The tissues from patients revised for suspected high wear had lower ALVAL scores, fewer lymphocytes than tissue from patients with suspected metal hypersensitivity. The high-wear group also had more macrophages and metal particles. Patients with pain and suspected metal hypersensitivity had the highest ALVAL scores and the least component wear.
“Painful hips with periprosthetic masses may be caused by high wear, but if this can be ruled out, metal hypersensitivity should be considered,” the authors wrote.
Histologic features such as synovial integrity, inflammatory cell infiltrates, tissue organization and metal particles can help identify the cause of pseudotumor-like reactions.