Assessing the dog as a model for human total hip replacement: analysis of 38 postmortem-retrieved canine cemented...

Thirty-eight cemented acetabular components that had been clinically implanted in client-owned dogs were retrieved postmortem and analyzed for mechanical stability, volumetric wear, and articular surface damage. Comparison of the results from this study with similar studies on autopsy-retrieved human components will provide insight into the adequacy of the dog as a model for human total hip replacement (THR). The canine average volumetric wear rate (6.7 +/- 4.2 mm(3) per year) was an order of magnitude lower than similar studies of human components; however, articular surface damage was considerably different from, and more severe than, that reported in the literature for human acetabular components. The incidence of mechanical loosening of the canine acetabular component was high, with 20 of 38 (52.6%) testing as loose. There was a positive correlation between articular surface damage and mechanical loosening of the acetabular component, but there was no significant correlation between volumetric wear and mechanical loosening, as seen in human retrieval studies. Initial failure events for the canine acetabular component appear to be mechanical in nature. Differences between human and canine acetabular components with regard to wear volume, articular surface damage, and mechanical loosening need to be taken into account when one is designing studies using dogs as the animal model for human THR.