In Vitro Activation of Monocyte Macrophages and Fibroblasts by Metal Particles

Several reports have documented the presence of focal bone lysis and aseptic loosening in patients after total hip replacement using noncementing techniques. A fibrous tissue reaction with histiocytic infiltration associated with metal debris adjacent to the femoral component has been described. The authors have used cell culture models to study the effects of metal particles on human monocyte/macrophages and connective tissue cells in order to define the potential mechanisms responsible for these clinical findings. We show that titanium, titanium alloy (Ti-6Al-4V), or cobalt-chrome-molybdenum particles activate monocyte/macrophages to release prostaglandin E₂ (PGE₂) and directly stimulate fibroblasts to increase collagen synthesis. These observations provide a potential mechanism by which the release of metal particulate debris could induce a fibrous connective tissue reaction and focal bone lysis at the bone/implant interface after noncemented total hip replacement.