Abstract
Metal-on-metal (MoM) hip arthroplasties produce abundant implant-derived wear debris composed mainly of cobalt (Co) and chromium (Cr). Cobalt-chromium (Co-Cr) wear particles are difficult to identify histologically and need to be distinguished from other wear particle types and endogenous components (e.g., haemosiderin, fibrin) which may be present in MoM periprosthetic tissues. In this study we sought to determine whether histological stains that have an affinity for metals are useful in identifying Co-Cr wear debris in MoM periprosthetic tissues. Histological sections of periprosthetic tissue from 30 failed MoM hip arthroplasties were stained with haematoxylin-eosin (HE), Solochrome Cyanine (SC), Solochrome Azurine (SA) and Perls’ Prussian Blue (PB). Sections of periprosthetic tissue from 10 cases of non-MoM arthroplasties using other implant biomaterials, including titanium, ceramic, polymethylmethacrylate (PMMA) and ultra-high molecular weight polyethylene (UHMWP) were similarly analysed. Sections of 10 cases of haemosiderin-containing knee tenosynovial giant cell tumour (TSGCT) were also stained with HE, SC, SA and PB. In MoM periprosthetic tissues, SC stained metal debris in phagocytic macrophages and in the superficial necrotic zone which exhibited little or no trichrome staining for fibrin. In non-MoM periprosthetic tissues, UHMWP, PMMA, ceramic and titanium particles were not stained by SC. Prussian Blue, but not SC or SA, stained haemosiderin deposits in MoM periprosthetic tissues and TSGT. Our findings show that SC staining (most likely Cr-associated) is useful in distinguishing Co-Cr wear particles from other metal/non-metal wear particles types in histological preparations of periprosthetic tissue and that SC reliably distinguishes haemosiderin from Co-Cr wear debris.
Highlights
Metal-on-metal (MoM) implant components are composed of approximately 62% cobalt, 27–30% chromium, 5–7% molybdenum by weight with small amounts of nickel, iron, silicon, carbon and manganese [1,2,3,4]
In most cases there was a prominent lymphoid infiltrate around blood vessels (Fig. 1d), a feature that has been termed aseptic lymphocytedominated vasculitis-associated lesion (ALVAL) [22]
On the necrotic tissue surface of pseudotumours, where apoptotic and necrotic macrophages released their cytoplasmic contents, there was a variable amount of purple staining (Fig. 2c, d); this necrotic tissue/exudate appeared to contain (Co-Cr) wear debris rather than fibrin as trichrome staining showed that fibrin was either absent or a relatively minor component in the superficial zone (Fig. 3a, b)
Summary
Metal-on-metal (MoM) implant components are composed of approximately 62% cobalt, 27–30% chromium, 5–7% molybdenum by weight with small amounts of nickel, iron, silicon, carbon and manganese [1,2,3,4]. Co-Cr particles and Co and Cr ions are cytotoxic and can elicit an adaptive cell-mediated immune response; as a consequence, there is marked necrosis and inflammation in periprosthetic tissues and MoM arthroplasties have been associated with early implant failure and pseudotumour formation [5,6,7,8,9,10]. Co-Cr particles are too tiny to be visible under the light microscope but small aggregates of these particles or shards of the metal implant can be identified histologically in MoM periprosthetic tissues [12, 13]. Non-MoM total hip arthroplasties that employ a modular Co-Cr femoral stem generate metal wear debris and uncommonly this can cause similar (MoM-associated) pathology and complications [15, 16]
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