The main goal of the « ACTISURF » project is to propose a new generation of joint prosthesis (hip, knee, ankle) made of bioactive titanium alloy TAl6V, capable of limiting and preventing joint infections. Even though conditions of prevention are drastic, about 1.5% of joint prostheses will be infected. The aging of the population associated with the increase of annual joint prosthesis implantations, make this new generation of biomaterial very attractive because it allows significant redcution of joint infection rates and the direct and indirect costs associated to these pathologies - reeducation, compensation of after-effects, temporary lost of salary, professional reclassifying. Among the 220 000 implanted joint prostheses, 4000 will be infected representing a minimal cost of about 400 millions euros. Titanium alloy is bioactive by chemical grafting of a polyanionic polymer exhibiting inhibition properties of bacterial adhesion. In addition, the grafted polymer is compatbile to osseous tissues and allows to control the inflammatory response. The partners of ACTISURF project present the complentary expertises in chemistry, biology and medicine necessary to this pluridisciplinary study : industrial partner commercialsing joint protheses, surface chemists, biologists of the in vitro cell response, microbiologists specialiezd in infection and inflmmatory response in vitro and in vivo, clinicians veterinary, orthopedists in charge of a reference center for the treatment of joint infections.