Pitt | Swanson Engineering
Influence of Bone Mineral Density on ACL Graft Fixation

Influence of Bone Mineral Density and Insertion Torque on ACL Soft Tissue Graft Fixation with Interference Screws

Due to the increased athletic participation of middle-aged and older people, more sports related injuries have occurred for these age groups. When performing surgery on these patients, surgeons must consider a possibly decreased bone mineral density (BMD). Following anterior cruciate ligament (ACL) reconstruction procedures, the graft fixation strength needs to withstand forces during physical therapy as well as strenuous activities once the patient gets back to sports. Particularly when using interference screws, the graft fixation strength depends on the BMD of the subjects and insertion torque of the interference screw. However, the influence of different screw sizes has not been examined. Therefore, the purpose of this study is to investigate the influence of BMD and insertion torque on load-to-failure and stiffness of two interference screws for ACL soft tissue graft fixation. Further, the two screw geometries will be compared to an extra-cortical fixation device. Based on prior studies that investigated the screw geometry, it was hypothesized that 1) oversizing the interference screw by one millimeter relative to the bone tunnel diameter will result in a higher load-to-failure and stiffness compared to an interference screw matching the bone tunnel diameter, and 2) extra-cortical fixation strength of ACL soft tissue grafts does not depend on BMD.
The study will be performed in collaboration with the Department of Health and Physical Activity.