Ultrastructural findings after intraarticular application of hyaluronan in a canine model of arthropathy.

We investigated the effect of intraarticularly applied hyaluronic acid (hyaluronan) on the cartilaginous structure of experimentally induced chondromalacia patellae in dogs. For the induction of chondromalacia, we used the Pond-Nuki technique, which involved severance and resection of the anterior cruciate ligament, as a canine model of arthropathy in 27 foxhounds (three groups of nine animals each). In a pilot study, we evaluated the effect of resection of the anterior cruciate ligament with no therapy. Patellar specimens were retrieved at 3, 6, and 12 weeks postoperatively. Subsequently, we compared a treatment group that received intraarticular injections of hyaluronan with a placebo group that received saline solution. The groups were compared at 3, 6, and 12 weeks postoperatively. Three animals from the treatment and placebo groups received five injections of hyaluronan during one of the 4-week intervals (weeks 3-6, 6-9, or 12-15). Specimens were retrieved 5 weeks after the last injection. In both groups, the uninvolved contralateral knee served as a control. The specimens were taken from the medial and lateral patellar poles. Histological analysis included light microscopy and transmission electron microscopy. The structural and ultrastructural changes were assessed qualitatively and were quantified with use of a modified Mankin score. Our results indicate that chondromalacia patellae may be induced with the Pond-Nuki technique. We found a significant reduction (p < 0.01) of cartilaginous lesions in the hyaluronan group compared with the placebo group. Our results suggest that intraarticularly applied hyaluronan is effective in delaying the degenerative process of cartilage degradation. Therefore, we conclude that the use of hyaluronan may be indicated during the early stages of chondromalacia.