Cytokine levels in synovial fluid from hips with well-functioning or looseprostheses

We analysed synovial fluid from 88 hips, 38 with osteoarthritis and 12 with well-functioning and 38 with loose hip prostheses. The levels of TNF-alpha , IL-1 beta (71 hips) and IL-6 (45 hips) were measured using the ELISA tech nique. Joints with well-functioning or loose prostheses had significantly i ncreased levels of TNF-alpha compared with those with osteoarthritis, Hips with aseptic loosening also had higher levels of IL-1 beta but not of IL-6 compared with those without an implant. The levels of TNF-alpha and IL-1 be ta did not differ between hips with stable and loose prostheses. Higher levels of TNF-alpha were found in hips with bone resorption of type II and type III (Gustilo-Pasternak) compared with those with type-I looseni ng. The level of cytokines in joint fluid was not influenced by the time in sit u of the implants or the age, gender or area of the osteolysis as measured on conventional radiographs. Our findings support the theory that macrophages in the joint capsule incre ase the production of TNF-alpha at an early phase probably because of parti cle load and in the absence of clinical loosening. Since TNF-alpha has an i mportant role in the osteolytic process, the interfaces should be protected from penetration of joint fluid.