Contact Mechanics of the Medial

The goal of this study was to determine how well a medial meniscal allograft restores the normal contact mechanics of the medial tibial plateau at the time of implantation. We measured maximum pressure, mean pressure, and contact area of the intact human cadaveric knee, the knee after meniscectomy, the knee with the original meniscus removed and reimplanted as an autograft, and the knee with an allograft. Measurements were made using pressure-sensitive film in 10 specimens loaded in compression to 1000 N at 0° 15° 30°, and 45° of flexion. The autograft and the allograft were identically implanted by cementing bone plugs attached to the meniscal horns in anatomic transtibial tunnels and suturing the outer edge of the meniscus to the remnant of the original meniscus. A medial meniscal allograft did not consistently restore normal contact mechanics because the process of implantation and the degree of match between the original and allograft meniscus affected the immediate load-bearing performance of the transplant. However, the allograft did significantly reduce the contact pressure compared with the knee after men‡Address correspondence and reprint requests to Maury L. Hull, PhD, Biomedical Engineering Graduate Group, Department of Mechanical Engineering, Bainer Hall, University of California at Davis, Davis, CA 95616. The opinions and assertions herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Air Force or the Department of Defense. No author or related institution has received any financial benefit from research in this study. iscectomy. If the results from this study can be extrapolated to patients, then using an allograft to restore contact mechanics to normal may require improvements in surgical technique and graft selection. To counsel a patient considering meniscal allograft transplantation, it would be helpful to know if the procedure prevents degenerative arthritis. The observations that a meniscal allograft heals and that some patients experience shortterm pain relief and an improvement in function have been used to measure success and justify the use of the procedure in selected patients. 19 However, studies in animal models have shown that degenerative changes still occur even when the meniscal transplant has healed. Because degenerative arthritis in a human knee takes years to evolve, long-term outcome studies have not been completed. A short-term method for evaluating whether degenerative arthritis can be prevented would be to determine if the maximum pressure, mean pressure, and contact area (that is, the contact mechanics) of the medial tibia1 articular surface in an intact knee are restored by a medial meniscal allograft at the time of implantation. The method of implantation and the allograft selected by the tissue bank may affect the restoration of normal contact mechanics, and each can be evaluated using human cadaveric knees. Identifying how each factor affects the contact mechanics might be useful for developing a strategy to improve the initial and long-term mechanical performance of meniscal allografts In this study, we chose to evaluate the effect of implanting a meniscal allograft in the medial hemijoint instead of the