Session Title: Orthopedics, Low Back Pain, and Rehabilitation
Session Type: Abstract Submissions (ACR)
Hip arthroplasty is the standard treatment of a painful hip destruction in rheumatoid arthritis and osteoarthritis. The use of metal-on-metal (MoM) bearing surfaces in total hip arthroplasty gained popularity especially in young and active patients during the last decade. Recently, worrisome failures due to inflammatory soft tissue reactions related to wear particles have been widely reported. The pathogenesis of this reaction is unknown. The aim of the present study was to clarify the inflammatory responses in peri-implant tissue in patients with a failure of MoM articulation.
Sixteen patients with a failed Articular Surface Replacement (ASR) implant were included in the study. Blood metal ion levels were analysed with coupled plasma mass spectrometry before revision surgery. Samples of peri-implant tissues collected during revision surgery were degraded by enzyme digestion and the distributions of cell populations were analysed by flow cytometry.
In macroscopic observation, peri-implant reactions had variable amounts of necrotic and granulomatous tissue and cystic pseudotumour formation. All patients expressed elevated levels of blood chromium and cobalt, but the patient-to-patient variation was significant. In histological examination, intensive inflammatory cell infiltration was a characteristic feature, but only few metal containing cells were observed. An analysis by flow cytometry showed that the distributions of the inflammatory cells were mainly polarized either to macrophage-rich (CD45+/CD14+) or T-lymphocyte-rich (CD45+/CD3+) phenotypes with the average portions being 54 % (macrophages) and 20 % (T-lymphocytes) in macrophage-dominated inflammation and 25 % (macrophages) and 54 % (T-lymphocytes) in T-lymphocyte-dominated conditions. The portions of B-lymphocytes (CD45+/CD19+) and granulocytes (CD45+/CD15+) were small. Interestingly, the levels of blood chromium and cobalt were significantly higher in patients with macrophage-dominated inflammation than in patients with T-lymphocyte-dominated inflammation.
The results suggest that the adverse reactions induced by MoM wear particles contain heterogeneous pathogeneses and the metal levels seem to be an important factor in the determination of inflammatory phenotype. The present results support the hypothesis that higher levels of metal particles cause tissue necrosis and macrophages are recruited to clear the necrotic debris. The lymphocyte-dominated inflammation may, on the other hand, reflect a delayed hypersensitivity reaction induced by lower metal concentrations.
E. L. Paukkeri,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/metal-concentrations-in-patients-with-failed-metal-on-metal-hip-prostheses-determine-the-inflammatory-phenotype-in-peri-implant-tissue/