How Three Methods for Fixing a Media Meniscal Autograft Affect Tibial Contact Mechanics

We evaluated three methods for fixing a medial meniscal autograft to determine which method restored tibial contact mechanics closest to normal. The contact mechanics (maximum pressure, mean pressure, contact area, and location of the center of maximum pressure) of the medial tibial articular surface were determined using pressure-sensitive film while knee specimens were loaded in compression to 1000 N at 0°, 15°, 30°, and 45° of flexion. Pressure was measured for the intact knee, the knee after meniscectomy, and the knee with the original meniscus removed and reimplanted as an autograft using three different fixation methods. The contact mechanics of the autograft reinserted with bone plug fixation were closest to normal; however, the maximum pressure was significantly greater than in the intact knee. Adding peripheral sutures neither improved nor worsened the contact mechanics. Fixation with sutures only did not restore normal contact mechanics. We concluded that medial meniscal transplantation requires anatomic fixation of bone plugs attached to the anterior and posterior horns to restore contact mechanics closest to normal. Fixation of the meniscal horns with sutures alone cannot be recommended. Removal of either the entire meniscus or a portion thereof may cause degenerative arthritis in the knee.10,12,13,17,18,28 The cause of the arthritis is increased contact stress on the articular cartilage, which increases in direct proportion to the amount of meniscus removed.6 Meniscal transplantation is being evaluated as a method to restore normal contact mechanics, with the long-term goal of preventing degenerative arthritis.19 One factor affecting the ability of a meniscal transplant to restore normal contact mechanics at the time of implantation is the method of fixation to the surrounding tissues. This factor is important because the menisci are connected to the surrounding tissues by a complex of attachments. The function of these attachments is to provide restraints that limit the movement of the meniscus when it bears load. Consequently, it would be expected that maintaining the restraints is important to the distribution of the com-pressive load transmitted by the joint.1 Because the restraints of a meniscal allograft are dictated by the surgical techniques used to fix the graft to the surrounding tissue, the methods of fixation were the focus of this study. Although previous research has examined the effect of different methods of meniscal fixation on the contact mechanics of the lateral compartment of the knee,11 we know of no previous research that has made such a study for the medial compartment. Study of the medial compartment is important because the medial meniscus is more commonly torn than the lateral meniscus16 and hence is more likely to be replaced. Because of anatomic differences between the lateral and medial compartments of the knee, the effect of fixation methods in the medial compartment warrants separate study from the effect of fixation methods in the lateral compartment. The purpose of this study was to evaluate three methods for fixing a medial meniscal transplant to determine which technique restored contact mechanics closest to normal. The methods studied included inserting bone plugs attached to the § Address correspondence and reprint requests to Stephen M. Howell, MD, 8100 Timberlake, Suite F, Sacramento, CA 95823. The opinions and assertions herein are the private view 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