Clinical Orthopaedics and Related Research

Shanbhag A.S., Jacobs J.J., Black J., Galante J.O., Glant T.T.


An in vitro study was conducted to determine the ability of particle challenged human peripheral monocytes to modulate fibroblast proliferation and bone resorption. The effects of commercially pure titanium and titanium-aluminum-vanadium as well as ultra high molecular weight polyethylene wear debris, either fabricated or retrieved from patients with failed total hip arthroplasties, were examined as a function of the composition, size and dose of particles. In vitro generated particles were selected to be closely matched in particle size distribution t that found in vivo. Dosages were controlled by standardizing the ration of particle surface area to mean monocyte surface area. The results support the hypothesis that, in vitro, challenge of monocytes by particulate wear debris results in a biphasic dose response. For the metal particles, fibrogenesis was observed over the range of 0.1X to 10X surface area ratio, the surface area of particles to the surface area of cells, while for both metallic and polyethylene particles saturated doses of 10X surface area ratio were required to stimulate bone resorption. Furthermore, metallic particles were able to stimulate fibrogenesis at doses at which both simulated and retrieved polyethylene were ineffective. While there may be a non-osteolytic chronically tolerable annual dose of ultra high molecular weight polyethylene wear debris corresponding to approximately 1 X surface area ratio, lower doses, especially of metallic debris, may produce reactive fibroblast proliferation and fibroplasia which may contribute to implant loosening and failure.