What's New in Surgical and Medical Management of Equine Osteoarthritis?

There are two main goals for medical treatment of osteoarthritis (OA) in the horse: reducing pain (lameness) and minimizing progression of joint deterioration. When formulating a treatment plan, the optimization of these goals will be influenced by an accurate and specific diagnosis, the stage of disease, severity, available treatment modalities and rehabilitation time. Clinicians realize that treating joint disease is an art and does not follow any specific recipe. To make the correct decisions the clinician can be helped by scientific studies that have defined potential risks and benefits of certain medication. An extensive review of the research pertaining to joint medication is beyond the scope of this summary; however, highlights of some of the most common medications based on surveying equine practitioners will be discussed as well as surgical options. Recent information has become available on a few commonly used therapeutic medications hyaluronic acid (HA), pentosan polysulfate, polysulfated glycosaminoglycan (PSGAG) and polyglycan.

In the first study, HA and PSGAG were compared to each other as well as a placebo control. No significant improvements were noted in clinical signs of pain with either PSGAG or hyaluronan compared to placebo treated control horses. Histologically, the degree of synovial membrane vascularity and subintimal fibrosis was significantly reduced with PSGAG treatment (trend for HA p=value <0.07), compared with controls. Histologically, significantly less fibrillation was seen with hyaluronan treatment, compared with controls. Similarly when pentosan was assessed using a similar OA model no reduction in pain was observed; however, articular cartilage fibrillation was substantially reduced compared to controls. Further,theconcentrations of chondroitin sulfate 846 epitope (aggrecan synthetic marker) was significantly increased in the synovial fluid of osteoarthritic and non-osteoarthritic joints of treated horses. Intraarticular treatment of OA-affected joints with polyglycan resulted in significant improvement in clinical pain (lameness scores), bone proliferation radiographically and degree of full thickness articular cartilage erosion seen grossly when compared to placebo treated OA-affected joints. Administration of polyglycan intravenously resulted in improved cartilage erosion but more pathologic response to flexion as well as an increase radiographic pathology.3 The combination of triamcinolone acetonide and PSGAG has also been assessed. While this combination reduced the progression of radiographic OA the degree of gross articular cartilage damage was greater, the degree of synovial membrane hemorrhage greater, less synovial fluid glycosaminoglycan (GAG) and decreased cartilage GAG content when compared to PSGAG alone.  [...]