Solochrome cyanine: A histological stain for cobalt-chromium wear particles in metal-on-metal periprosthetic tissues

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.

Fig. 1

Representative HE-stained sections of MoM periprosthetic tissue showing: a macrophages containing fine brown corrosion Co-Cr metal wear particles; b necrotic superficial zone (*) on the surface of an MoM pseudotumour in which can be seen at high-power c viable and apoptotic/necrotic macrophages and numerous pigmented Co-Cr metal wear particles (some arrowed); d ALVAL with a collection of lymphoid cells (arrowed) around small vessels

Fig. 2

a Low-power and b High-power views of SC cytoplasmic staining of macrophages and giant cells containing metal wear (some arrowed); ALVAL lymphoid cells (asterisk) and other connective tissue elements are unstained. c SC staining of the superficial necrotic zone with d high-power view of SC-stained metal wear debris (arrowed)

Fig. 3

Cystic MoM pseudotumour showing: a blue SC staining for metal wear debris and b absence of (Goldners) trichrome staining for fibrin in the superfical necrotic zone (*)

Fig. 4

Prussian Blue staining of MoM periprosthetic tissue, showing positive (blue) staining for Fe³⁺ of some but not all pigmented foreign body macrophages and no staining of particulate Co-Cr metal wear debris (some arrowed)

Fig. 5

Non-MoM periprosthetic tissues from failed hip arthroplasty showing absence of SC staining of: a UHMWP wear particles (some arrowed) in macrophages [strongly birefringent under polarised light in b] and c black titanium particles in macrophages and giant cells

Fig. 6

Diffuse TSGCT with Fe³⁺—containing haemosiderin deposit (arrowed), showing: a strong blue staining with PB but b no staining with SC