In vivo study of post-traumatic arthritis in rabbit knees

The purposes of this study were to determine a threshold force for which the post-traumatic arthritis of a joint is inevitable and to produce a viable model for arthritic studies. Impacts of varying weights were made to the medial femoral condyles of 36 New Zealand white rabbits. One knee in each rabbit was impacted, and the contralateral knee underwent all of the same surgical treatments as the impacted knee to ensure that the surgery itself was not a cause of arthritic development. The impactors used were of two types: flat and customized. The customized impactors were made using polymethyl methacrylate bone cement shaped to the knee´s contours, allowing for application of uniform stress over the impact area. Varying the type of impactor and the amount of force applied, the amount of stress that the knee was subjected to on impact was varied. The rabbits were sacrificed at periods of six months and one year and their knees were harvested and observed for gross and histological evidence of arthritis. Such signs of arthritis include thinning of cartilage, osteophytic formation at the sites of increased stress, and spread of bone and cartilage into the articular spaces. Upon completion, this study will present a threshold stress for post-traumatic arthritis and a viable model for arthritic studies. Knowing a threshold stress will aid in the prevention of post-traumatic arthritis by suggesting better safety designs. If impact stresses can be kept below those found to cause post-traumatic arthritis, its development can be avoided. Furthermore, the animal model developed can be used to test drugs for the treatment and prevention of arthritis