Silver methenamine staining for scanning electron microscopy of bone sections containing biomaterials.

Sections of tissue containing orthopedic materials are currently used to study the compatibility of those materials and to perform electron probe microanalysis at the material-tissue interface. Identification of the cells in contact with the material by Scanning electron microscopy (SEM) is of interest. We have developed a method for staining cells and tissue structures embedded in polymethyl methacrylate with silver methenamine once the sections have been obtained. Sections were prepared by grinding, and the silver methenamine was applied after oxidation with periodic acid. The procedure was carried out in a microwave oven. Backscatter SEM showed staining of the cell nucleus membrane, chromatin, the nuclear organizers, and the chromosomes of dividing cells. The cytoplasm and the cytoplasmic membrane were also stained. Collagen fibers of the extracellular matrix and the mineralized matrix of bone were labeled. Material particles in the macrophages were easily recognizable and Energy-Dispersive Spectrometer were not impaired by the presence of silver in the preparation.

A study of structure and degradation of nonpolymeric biomaterials implanted in bone using reflected and transmitted light microscopy.

Orthopedic biomaterials currently are made of metal alloy coated with one or more thin layers of dense or porous ceramic or metal. Sections of these materials implanted in human bone were made without altering the implant or bone-implant interfaces. Bone containing an implant was fixed and then embedded in polymethylmethacrylate. Thick sections were made using a cooled, low speed diamond saw, then ground and polished. Some were stained by fuchsin-toluidine staining solution, others were acid etched to reveal the structure of the metal contained in the prosthesis. Observation by reflected and transmitted light microscopy revealed microstructure of the implant material as well as features of the surrounding tissues.

[Tartrate-resistant acid phosphatases (TRAP) and cytology of pseudosynovial membranes]. / Phosphatases acides tartrate résistantes (TRAP) et cytologie des membranes pseudo-synoviales.

Pseudo-synovial membranes are found at the interface between bone and aseptically lost prostheses. They are supposed to be due to the release of material debris at the interface with bone. They are mostly composed of macrophages and giant cells, and some fibrocytes in the deep layer of the membrane. The different histological structures present in these membranes have been largely described. Very recently, Kadoya et al. have demonstrated that a lot of giant cells present in the pseudo-synovial membranes show a tartrate resistant acid phosphatase activity in the presence of more than 100 mM tartrate. They have also shown that some of these cells were responsible for bone degradation. We have studied the tartrate acid phosphatase activity of a series of 10 membranes containing various material debris: titanium alloy, stainless steel, polymethylmethacrylate, polyethylene. Many mono or multinucleated cells showed a TRAP activity in their lysosomes in the presence of a 400 mM tartrate concentration. In certain membranes, these cells showed a TRAP activity located in the nucleus. This study shows that the macrophage population is very heterogeneous and the difference between osteoclasts and giant cells may be unclear.