A histological study of polyethylene wear particles in a rabbit model

A significant problem affecting the stability of hips and knees in the total joint arthroplasty is the aseptic loosening of the implants due to the osteolysis by the ultra molecular weight polyethylene (UHMWPE) wear particles. Recently, Oil Red O (ORO) stain was used in identifying these particles in the tissues retrieved from the failed implants. The objective of the authors' study was to examine the effect of two micron polyethylene particles (4 mg) implanted into the rabbit knees for periods of 6 and 9 months. The authors examined the sections of liver, kidneys, popliteal lymph nodes, femurs and tibias to detect the presence of UHMWPE particles. Soft tissue or bones were first embedded in paraffin blocks and five micron sections were cut. One section was stained with Hematoxylin and Eosin (H&E) stain and the other with ORO stain. The slides were viewed under a polarized light using a light microscope. The results showed the presence of the polyethylene particles in the soft tissues such as liver, kidneys and popliteal lymph nodes as well as in the tibia and femurs. They demonstrated that these polyethylene particles are easily seen either with H&E or ORO stain. They were either round or needle shaped. A visible comparison of tissue sections appeared to indicate the presence of greater number of particles in the specimens from the 9 month animal than those seen in the 6 month animals.