Metal allergy, metal implants and fracture healing

The rabbit tibia was used as a model to study the effects of metal sensitivity reactions on the healing of fractures. Animals were injected with nickel chloride in Freund's complete adjuvant to cause sensitivity, and fractures were stabilized with 316L stainless steel intramedullary rods and followed for 16 weeks. A control group received no injections. The response was evaluated biomechanically with torsional testing at sacrifice, radiologically by examining the roentgenograms for evidence of loosening, and histologically. The results demonstrated a slight decrease in strength, a moderate increase in resorption and a significant decrease in cellularity and new bone formation in the sensitive animals as compared to control. These results are consistent with a reaction of comparatively short duration.