Rheologic behavior of osteoarthritic synovial fluid after addition of hyaluronic acid: a pilot study.

Viscosupplementation is a symptomatic treatment of osteoarthritis (OA) intended to restore rheologic homeostasis of the synovial fluid by injecting hyaluronic acid intraarticularly. Despite the long history of this therapy, little is known about its mechanisms of action and differences between commercial preparations. We investigated the rheologic behavior of OA synovial fluid with time, when stored at 4 degrees C, before and after the addition of two hyaluronic acid commercial preparations (linear and cross-linked). Thirteen OA synovial fluids were stored at 4 degrees C and assayed using steric exclusion chromatography, which allows hyaluronic acid to be separated from the remaining pool of proteins and its molecular weight and concentration to be determined without any pretreatment and calibration. The synovial fluid rheology also was studied in vitro, before and after addition of two viscosupplements, over 6 weeks. The non-Newtonian behavior of synovial fluid throughout followup appears to be the result of loose interactions between proteins and hyaluronic acid. When mixed with the linear hyaluronic acid, synovial fluid becomes less non-Newtonian whereas the non-Newtonian behavior was reinforced when mixed with the cross-linked hyaluronic acid. The rheology was nearly unchanged for all synovial fluids over 6 weeks. Our preliminary trial shows it is possible to study synovial fluid, stored at 4 degrees C, over a long time and suggests the enzymatic degradation of hyaluronic acid is negligible under these experimental conditions.

Factors predicting long-term efficacy of Hylan GF-20 viscosupplementation in knee osteoarthritis.

OBJECTIVES: To describe the long-term effects of Hylan GF-20 viscosupplementation in patients with knee osteoarthritis and to identify factors predicting efficacy. METHODS: One hundred and fifty-five patients (80 women and 75 men; mean age, 69 years) with symptomatic knee osteoarthritis each received three intraarticular Hylan GF-20 injections. Effectiveness, safety, and satisfaction were evaluated 7-14 months later based on a physician's examination and a five-item questionnaire. Radiological data (distribution and degree of joint space loss), size of the effusion (none, moderate, large), injection route (anterior, medial to the patella, or lateral to the patellar), and side effects were recorded. Factors predicting effectiveness were looked for by univariate analysis followed by multivariable analysis with adjustments on age, body mass index, gender, and time from treatment to questionnaire administration. RESULTS: Satisfaction was good in 78% and 58.9% of the patients according to the physician examination and questionnaire, respectively. Safety was considered excellent or good in 96.2% of the patients. Factors significantly (P < 0.05) associated with a good outcome were a moderate effusion, injection lateral to the patella, joint space loss in a single compartment, and radiological meniscal calcinosis. CONCLUSION: The factors predictive of a good response to Hylan GF-20 in this study need to be confirmed, and their impact quantitated, in prospective studies.