Wear debris from hip prostheses characterized by electron imaging

The characterization of wear particles is of great importance in understanding the mechanisms of osteolysis. In this unique study, thirty-one tissue samples were retrieved at revision surgeries of hip implants and divided into four groups according to the composition of metal prosthetic components. Tissue samples were first analyzed histologically and then by scanning electron microscopy (SEM) combined with back-scattered electron imaging and energy dispersive X-ray spectroscopy. Therefore, particles were studied directly in situ in tissue sections, without the requirement for particle isolation. The composition of metal wear particles detected in the tissue sections corresponded to the composition of the implant components. A considerable number of large metal particles were actually clusters of submicron particles. The clustering of submicron particles was observed primarily with CoCrMo (cobalt-chromiummolybdenum) and, to a lesser extent, for stainless steel particles. SEM secondary and back-scattered electron imaging was an appropriate and selective method for recognizing the composition of metal particles in the in situ tissue sections, without destroying their spatial relationship within the histology. This method can be used as a screening tool for composition of metal and ceramic particles in tissue sections, or as an additional method for particle identification.