Biomaterial surface properties, via alterations in the adsorbed protein layer, and the presence of specific functional groups can influence integrin binding specificity, thereby modulating cell adhesion and differentiation processes. The adsorption of fibronectin, a protein directly involved in osteoblast adhesion to the extracellular matrix, has been related to different physical and chemical properties of biomaterial surfaces. This study used blasting particles of different sizes and chemical compositions to evaluate the response of MG63 osteoblast-like cells on smooth and blasted titanium surfaces, with and without fibronectin coatings, by means of real-time reverse transcription-polymerase chain reaction (qRT-PCR) assays. This response included (a) expression of the α(5), α(v) and α(3) integrin subunits, which can bind to fibronectin through the RGD binding site, and (b) expression of alkaline phosphatase (ALP) and osteocalcin (OC) as cell-differentiation markers. ALP activity and synthesis of OC were also tested. Cells on SiC-blasted Ti surfaces expressed higher amounts of the α(5) mRNA gene than cells on Al(2)O(3)-blasted Ti surfaces. This may be related to the fact that SiC-blasted surfaces adsorbed higher amounts of fibronectin due to their higher surface free energy and therefore provided a higher number of specific cell-binding sites. Fn-coated Ti surfaces decreased α(5) mRNA gene expression, by favoring the formation of other integrins involved in adhesion over α(5)β(1). The changes in α(5) mRNA expression induced by the presence of fibronectin coatings may moreover influence the osteoblast differentiation pathway, as fibronectin coatings on Ti surfaces also decreased both ALP mRNA expression and ALP activity after 14 and 21 days of cell culture.

SummaryA study of metallic implants consecutively removed from 133 patients at the Hospital for Special Surgery during a 2-year period was conducted to evaluate their performance. They had been implanted for 2 weeks to over fifteen years. The implants studied consisted of prostheses and internal fixation devices used for open reduction of fractures or immobilization of osteotomies. The implants had been fabricated from either stainless steel or cobalt-chromium alloys.Case histories and roentgenograms were reviewed. A detailed inspection of each implant was performed including failure analysis when required. Crevice or fretting corrosion was noted on all but one stainless steel implant of the plate and screw type, and to a lesser extent with the cobalt-chromium alloy implants. Extreme wear was noted on contact areas of articulating prosthetic components made of cobalt chromium alloy. Complete mechanical failures of internal fixation devices were attributable to fatigue, design deficiencies or misuse of the implant. These findings are discussed in light of the clinical results.