Assessment of Intravenous or Intra-articular Hyaluronic Acid, Chondroitin Sulfate, and N-acetyl-D-glucosamine in Treatment of Osteoarthritis Using an Equine Experimental Model

1. Introduction
Hyaluronic acid, chondroitin sulfate and N-acetyl-D-glucosamine (HACSAG) has been formulated into a new product, Polyglycan®.^a  Safe and effective clinical usage has been anecdotally reported to the manufacturer in horses intra-articularly (IA) and intravenously (IV) for 3 years.

2. Materials and Methods
Osteoarthritis (OA) was induced in one middle carpal joint (MCJ) of 24 horses (n = 8/treatment group). All MCJs were treated with 125 mg of amikacin.^b  Placebo (PCB) and IV HACSAG horses also received 5 ml of sterile saline in both MCJs, whereas IA HACSAG treated horses received 5 ml of HACSAG^a  in the OAaffected joint on days 0, 7, 14, and 28. IV HACSAG treated horses received 5 ml of HACSAG^a  intravenously every fifth day throughout the study. Evaluations (0–4 scale) included clinical, radiographic, gross, and histologic examinations as well as synovial fluid, histochemical, and biochemical analyses. Data were analyzed using a mixed model analysis of variance (p < 0.05 was significant).

3. Results
No adverse treatment-related events were detected. IA HACSAG significantly improved lameness as well as radiographic and bone proliferation scores compared with PCB-treated OA-affected joints. Full-thickness cartilage erosion was also significantly improved in both IA HACSAG and IV HACSAG treatment groups. Response to flexion and radiographic interpretation differed when the IV HACSAG was compared with the IA HACSAG or PCB OA-affected limbs; this finding is under further investigation. [...]