The short and long-term effects of high moleculer weight hyaluronic acid (Hylan G-F 20) on experimentally temporomandibular joint osteoarthritis: A radiologic and histologic study

The aim of this study is to determine the radiologic, and histologic findings of short and long-term efficacy of high molecular weight HA (Hylan G-F 20) on experimental TMJ osteoarthritis. This study was performed on 24 male, 3.5 months old, 3.5 kg weight, and white New Zealand rabbits. Each rabbits received a bilateral intraarticular injection of 50 µl of a 3 mg/ml solution of sodium mono-iodoacetate (MIA). 4 weeks after MIA injection, 0,5ml of 4mg Hylan G-F 20 was injected into one joint and 5ml of 0,9% saline solution into the contralateral joints served as control. (once a week for 3 weeks). After computed tomography (CT) was obtained pre-injection and post-injection at the 4., 6., and 8. weeks. Radiologic scores of osteoarthritic changes were performed on CT. The radiographic signs of osteoarthritis (OA) (erosions, sclerosis, ostephytes, and flattening of the condyle) were localized and registered in 3 parts of the mandibular condyle; the medial, the central, and the lateral part. The histological changes of the cartilage, osteochondral junction, condrocytes and subchondral bone were determined. Histological findings were obtained at 4., 6., and 8. weeks in cartilage (50%, 25%, 25%), osteochondral junction (62,5%, 50%, 37,5%), chondrocytes appereance (87,5%, 37,5%, 12,5%), and subchondral bony changes (62,5%, 50%, 50%), respectively. In the cartilage changes on condyle, there was a statistically significant difference between two groups at 4 weeks (p?0,05). A significant decrease of cartilage changes was found in controls between 4 and 6 weeks follow-up (p?0,05). The changes of chondrocytes apperance at 4 and 8 weeks were observed 6 (75%) and 2 (25%) joints in controls, 7 (87,5%) and 1 (12,5%) in experimental joints, respectively. The changes of chondrocyte apperance were significantly decreased in experimental group at all follow-ups (p?0,05). Cartilage changes were observed in 6 (75%) controls and 4 (%50) experimental joints at 4 weeks follow-up. The mean pre and post-injection BT scores in both groups at 4 weeks were 1,5±1,41, 0,5±0,53 and 3,25±2,31, 1,25±0,89, respectively. A possitive correlation between pre-injection BT values and histologically cartilage changes was found at 4 weeks follow-up (p?0,05). We concluded that intraarticular injection of Hylan G-F 20 decreased the cartilage changes in early stage of TMJ OA and the clustering of chondrocytes demonstrated that chondroprotective effects of Hylan G-F 20 caused by the hypertrophic responses.Keywords: Temporomandibular Joint, osteoarthritis, viscosupplementation, Hylan G-F 20.