Experimental Study on the Prevention of Posttraumatic Osteoarthritis in the Rabbit Knee Using a Hinged External Fixator in Combination with Exercises.

To report the design and effect of our proprietary hinged external fixator, used in combination with treadmill exercise for rabbits with intra-articular inflammation and cartilage degeneration. Thirty-two white rabbits were randomly allocated into four groups: No treatment (NT), Distraction only (D), Exercise only (Ex), and Distraction plus exercise (D + Ex). Each rabbit underwent an anterior cruciate ligament transection on the right knee, with the contralateral knee used as a sham control (C). In the D + Ex group, the levels of Interleukin (IL)-1β and Tumor necrosis factor (TNF)-α in synovium and TNF-α in joint effusion were significantly lower, while the expression of IL-10 in joint effusion and blood was significantly higher. The ratio of IL-10/TNF-alpha in blood was also the highest in the D + Ex group. The condition of collagen loss was examined: the D + Ex group had the lowest level of type II collagen in effusion and C-telopeptides of type II collagen (CTX-II) in blood. On the other hand, the D + Ex group had the highest expression of cartilage regeneration genes, including type II collagen, Aggrecan (AGN), and SRY-box 9 (SOX9). Finally, the histology showed an attenuation of cartilage degeneration with a lower OA score in the D + Ex group. Our hinged external fixator combined with treadmill exercise up-regulated cartilage regeneration genes, reduced synovial and intra-articular inflammation, and reduced type II collagen and proteoglycan loss, indicating the use of the fixator in combination with treadmill exercise could prevent progression of posttraumatic osteoarthritis of knee joint in rabbits.