Tissue reaction to metal on metal total hip prostheses

The periprosthetic tissue reaction to polyethylene wear debris in metal on polyethylene total hip replacements is strongly implicated as the cause of osteolysis. This has led to a renewed interest in metal on metal total hip replacements. However, little is known about the role of wear debris in failures of these prostheses. Capsular and interface tissues from 9 long and short term metal on metal total hip replacement retrievals were studied to assess the tissue reaction around these prostheses. As compared with metal on polyethylene cases, the extent of the granulomatous inflammatory reaction and the presence of foreign body type giant cells was much less intense in metal on metal cases, likely because of the lower numbers and overall smaller size of metal wear debris particles. This may lead to a better transport of the particles from the joint tissues and a lower incidence of periprosthetic osteolysis around metal on metal hip replacement.