A comparative staining technique to detect mineral oil contaminants from orthopedic implants.

An adverse tissue response was reported in patients implanted with porous coated implants containing a mineral oil contaminant. A comparative staining technique was developed in a rabbit and sheep model to identify the presence of a mineral oil contaminant on porous coated implants by examining the surrounding tissues and end organs. The hypothesis for the study was that mineral oil, a saturated lipid, could be distinguished from unsaturated lipids such as animal fats. Frozen rabbit and sheep tissues were stained with hematoxylin and eosin, oil-red-O, and bromide-silver nitrate. Twenty-eight positive control rabbits were injected with mineral oil and 12 negative control rabbits were injected with saline into the paravertebral muscle and synovial cavity of the knee joint. Comparative analysis of tissue was conducted after 1, 3, 5, and 12 weeks. Thermally cleaned porous coated implants were implanted for 6, 12, and 24 weeks into cancellous bone of the distal femur of sheep to allow for a weight-bearing model. The comparative histological analysis of the positive control rabbit tissue allowed for detection of mineral oil in all tissues examined. Histological analysis of sheep tissue and saline-injected rabbit tissue showed no evidence of mineral oil or adverse tissue response.