How In Vivo Alteration of Hip Replacement Wear Mode Can Cause a Voluminous Inflammatory Reaction and an Excessive Titanium Exposure

Background: Wear particle reaction is present in every arthroplasty. Sometimes, this reaction may lead to formation of large pseudotumors. As illustrated in this case, the volume of the reaction may be out of proportion to the volume of the wear scar. This case also is the first description of elimination kinetics of systemic titanium exposure caused by wear of a hip arthroplasty. Methods: Case report. Results: A 85-year-old male required revision after total hip arthroplasty due to aseptic loosening of the cup. A massive local adverse reaction to metal and polyethylene debris developed before revision, much larger than the implant damage would intuitively suggest. In this case, in vivo transition in wear mode from edge loading to impingement wear resulted in excessive titanium and polyethylene wear and subsequently a voluminous macrophage reaction and an excessive systemic titanium exposure, with blood concentrations showing a very long elimination half-life of more than two years. Conclusions: The volume of the wear particle reaction is dictated by the volume of the inflammatory cells, not of the wear particles. To the best of our knowledge, this is the first description of elimination kinetics in case of systemic titanium exposure. While the tissue response is caused by a sudden increase of titanium and polyethylene debris, titanium is detectable through whole blood, not serum, analysis and thus be an indicator for risk of failure due to abnormal articulation of the joint replacement. Such measurement may be useful if changes in implant position are detected radiographically. Major elevations of titanium concentrations may require revision, as for any other metal ions.