BIOMECHANICAL EVALUATION OF MEDIAL FEMORAL CONDYLAR SUBCHONDRAL CYSTIC LESIONS AND THE EFFECTS OF TREATMENT WITH INTERNAL FIXATION

Professional Biological Sciences: 2nd Place (The Ohio State University Edward F. Hayes Graduate Research Forum)Purpose of the study: Subchondral cystic lesions (SCLs) in the medial femoral condyle are a common equine orthopedic problem occurring most commonly in the first two years of life. They are located on the weightbearing surface of the condyle and are frequently associated with lameness. While the pathophysiology of SCLs is poorly understood, they are believed to be the result of either osteochondrosis or trauma, or perhaps both. Similar to bone cysts in adolescent children, there are many treatments recommended for SCL, and like in children, recurrence and treatment failure rates are unacceptably high . Conservative management includes stall rest with or without intra-articular medication. Surgical management consists of intra-cystic injection with corticosteroids, cystic debridement, cancellous bone grafting, mosaic arthroplasty, and placement of chondrocytes or mesenchymal cells in fibrin glue. The goals of treatment are to maximize the amount and quality of subchondral and epiphyseal bone within the defect leading to a reduction in the inflammation caused by the contact of joint fluid with epiphyseal bone, and improve the attachment of the articular cartilage overlying the defect. There is very little information available about the biomechanics of the stifle joint of the horse either in health or disease, and no treatments of SCLs address the possible changes in biomechanics generated by what is often a large void in a critical weight-bearing area of the medial femoral condyle. The objectives of this study were to identify and measure the strain on the medial femoral condyle before and after the creation of a defect similar to a SCL and evaluate if that strain is altered with the placement of a cortical bone screw placed in lag fashion across the defect. The first hypothesis was that there would be a decrease in the bone strain measured on the abaxial aspect of medial femoral condyle and proximal tibia, and a corresponding increase in strain on the medial meniscus, after the experimental creation of a medial femoral condylar subchondral bone defect. A second hypothesis was that internal fixation of the subchondral bone defect with a 4.5mm cortical bone screw placed in lag fashion would return bone strain to a level similar to the pre-defect measurements.No embarg