The effect of hyaluronan injections into human knees on the number of bone and cartilage wear particles captured by bio-ferrography

Osteoarthritis is characterized by degradation of cartilage and subchondral bone, releasing wear particles into the synovial fluid. Intra-articular injections of exogenous hyaluronan are often given to patients suffering from osteoarthritis in order to compensate for the reduction in the level of endogenous hyaluronan and to restore the rheological properties of the synovial fluid. The exact effect of these injections is still ambiguous. In this work bio-ferrography was used to capture magnetically labeled cartilage and bone debris from the synovial fluid in human knees before each of four injections (Euflexxa™). The wear particles were counted and characterized microscopically and chemically. WOMAC, VAS, SF-36 and KS questionnaires indicated significant pain relief during the treatment, but suffered from inconsistency. Bio-ferrography showed a reduction in the concentration of both cartilage and bone particles, with a minimum after the third hyaluronan injection. The advantages of bio-ferrography as a primary assessment tool are discussed. The results indicate that while hyaluronan treatment may temporarily slow the wear rate to an extent beyond a placebo effect, it does not prevent joint degradation altogether.