Biochemical and histological evaluation of human synovial-like membrane around failed total hip replacement prostheses during in vitro mechanical loading

The biochemical role of the synovial-like membrane formed at the interface of eight aseptic failed total hip prosthesis has been investigated during i n vitro mechanical loading. The study was carried out on four membranes fro m cemented prosthesis and four titanium alloy uncemented ones. Intermittent positive pressure leading to 20% deformation of the membrane (100g/cm(2)) was applied to the membrane fragments in cycles (300 cycles/15 min) repeate d three times at thirty minutes intervals in which interleukin-6 (IL6), pro staglandin-E2 (PGE2) and interleukin-1 beta (IL1 beta) levels were quantifi ed both in culture media and in tissue extracts. Histological, morphometric al and immunohistochemical studies were also carried out on the same membra nes. Mechanical stress evidenced an increase in the release of the examined cyto kines both in cemented and uncemented prosthesis tissues; particularly evid ent was IL6 trend of increase from cemented prosthesis and IL1 beta result from uncemented ones. Histomorphological and immunohistochemical data revea led no differences between membranes obtained from cemented and uncemented prosthesis as to cell proliferation, fibrosis, macrophages lymphocytes B an d T population, vessels and nervous fibers. The results indicate that mecha nical stress plays a fundamental role in increasing membrane production and release of cytokines known as bone-resorbing agents. Furthermore, the hist ologic finding of synovial-like membrane with the same histomorphological a nd immunohistochemical findings but with different biochemical response to mechanical stimulation, suggests that cells involved in the production and release of the considered mediators might have different strain behavior by different development conditions (previous contact with PMMA). (C) 2001 Kl uwer Academic Publishers.