Review of intra-articular 2.5% polyacrylamide hydrogel, a new concept in the management of osteoarthritis

Recent observational and experimental trials have demonstrated that intra-articular 2.5% injectable polyacrylamide hydrogel (2.5 iPAAG) is highly effective, lasting and safe for the treatment of equine osteoarthritis (OA). Over the last decade, intra-articular 2.5 iPAAG has shown to be a potent and promising drug in the medication of OA in horses, as no other single medical treatment for OA has such prolonged efficacy. Preliminary observations on the mechanisms of action of intra-articular 2.5 iPAAG support a mechanical effect through integration into the synovial membrane, an increase in joint elasticity possibly reducing overall joint capsule stiffness, and provision of lasting viscosupplementation which contributes to protecting articular surfaces. Because 2.5 iPAAG is an inert and biocompatible hydrogel, no effects on arthrocentesis cytology parameters have been observed. Studies also suggest that the positive effects of 2.5 iPAAG occur in the absence of intra-articular neurotoxicity or fibrosis, with a low-level macrophage-driven foreign body response. The effect on the synovial membrane and joint capsule and the long-acting viscosupplementation represent new concepts in the management of equine OA.