Book Description

The most important factor contributing to short-term and long-term success of cementless total joint arthroplasties is osseointegration. Osseointegration is the process by which a direct structural and functional connection between living bone and the surface of an implant is made. Surface contaminants may remain on orthopaedic implants after sterilization procedures and impair osseointegration. For example, specific lots of hip replacement Sulzer Inter-OPTM acetabular shells that were associated with impaired osseointegration and early failure rates were found to be contaminated with both bacterial debris and machine oil residues. However, few osseointegration studies have focused on surface contaminants and their effect on implant integration is unknown. Therefore, we developed a novel murine model that provides quantitative and reproducible measurements of osseointegration to study the effect of surface contaminants. We found that a rigorous cleaning procedure significantly enhances osseointegration compared to implants that were autoclaved. The most likely interpretation of these results is that surface contaminants on the autoclaved implants inhibit osseointegration. Using our murine model, we also found that Gram-negative bacterial derived LPS or machine oil residues on implants inhibit osseointegration. Ultrapure LPS adherent to titanium alloy discs had no detectable effect on early stages of MC3T3-E1 osteogenesis in vitro such as attachment, spreading or growth but inhibited later stages of osteogenic differentiation and mineralization. In contrast, machine oil on titanium alloy discs inhibited osteoblast attachment, spreading, growth, differentiation and mineralization in vitro. These results demonstrate that both adherent LPS and machine oil can significantly impair osseointegration through direct effects on osteoblasts; however, they do so by inhibiting distinct steps in the process. The presence of both LPS and machine oil could lead to synergistic impairment of osseointegration, which may account for the impaired osseointegration in the failed lots of Sulzer Inter-OPTM implants. These results highlight bacterial debris and machine oil as types of surface contaminants that can impair the osseointegration of orthopaedic implants. In addition, these results justify the need for the development of better detection and removal techniques for contaminants on orthopaedic implants.