title: Cellular reactions in hip prosthesis loosening.
abstract: Based on the results obtained in histological examinations carried out on periprosthetic tissues in a large series of cases of prosthetic hip joint explants, the authors analyze the cellular events that may occur in loosening phenomena as compared to what occurs in the paraphysiological repair process that is observed in the stable prosthesis. Like other authors, they believe that the principal role in the mechanism of loosening is played by macrophages which are recalled in a large number, at times together with multinucleate giant cells, at the bone-implant interface, after micromovements of the prosthesis and the formation of wear particles have occurred. The macrophages would be capable of favoring resorption of the periprosthetic bone tissue, producing areas of osteolysis in which the transmission of the mechanical stress of loading is modified. The ensuing prosthetic instability increases wear phenomena, causes a greater amount of osteolysis, and, in a vicious cycle, loss of the relationship between bone and implant, and, thus, prosthetic loosening. Finally, the authors report a hypothesis on the pathogenesis of the phenomenon, based on which non-physiological stress, associated with wear and eventually infection, leads to loosening.
authors.affiliation: Laboratorio di Biocompatibilità dei Materiali da Impianto, Istituti Ortopedici Rizzoli, Bologna.
authors.forename: A
authors.initials: A
authors.lastname: Pizzoferrato
authors.forename: S
authors.initials: S
authors.lastname: Stea
authors.forename: G
authors.initials: G
authors.lastname: Ciapetti
authors.forename: E
authors.initials: E
authors.lastname: Cenni
authors.forename: C
authors.initials: C
authors.lastname: Tarabusi
authors.forename: A
authors.initials: A
authors.lastname: Toni
mesh_terms: D001843:Bone Cements; D001862:Bone Resorption / Q000209:etiology / Q000473:pathology; D003141:Communicable Diseases / Q000150:complications / Q000473:pathology; D006621:Hip Joint / Q000473:pathology*; D006622:Hip Prosthesis; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000473:pathology; D009336:Necrosis; D011474:Prosthesis Design; D011475:Prosthesis Failure
chemical_list: D001843:Bone Cements