Biomechanical Comparison of Meniscal Repair Systems in Shear Loading

Abstract

A meniscal tear is an injury that often occurs as a result of a varus or valgus rotation of the femur on the tibia coupled with axial rotation while the knee is partially flexed, thus creating preferential loading of the posterior horn and shear forces on the meniscus. Such injuries can be repaired surgically, either with standard suturing techniques or with commercially available all-inside meniscal repair devices, which are designed to make the repair surgery faster, easier, and potentially safer. Many prior biomechanical studies have loaded an excised, repaired meniscus in tension and found that the repaired meniscus performs similarly to an uninjured sample. However, it is more appropriate to apply shear forces to the tissue in order to simulate the mechanism of injury. To date, three prior studies have investigated the biomechanical properties of meniscal repairs in shear, all of which used isolated meniscal tissue samples. The present study used an in situ bovine model to investigate the strength of commercially available meniscal repair systems under a shear loading regime. Medial menisci were torn and subsequently repaired using one of three techniques: standard inside-out vertical mattress sutures, Depuy Mitek Omnispan, or Smith & Nephew Fast-Fix. A control group was left unrepaired. Samples were subjected to a battery of cyclic side loading to create shear forces within the knee. Statistical analysis (ANOVA) demonstrated no significant difference in the stiffness, shear force, or subsidence between groups. The conclusion that the repair techniques perform similarly is consistent with tensile and in situ testing. Pathological observations showed no significant differences between repair devices, but all repaired samples demonstrated less wear than unrepaired samples, indicating that the experimental model is an effective method for creating wear within the knee. This result indicates that the flexible all-inside devices are mechanically comparable to the more commonly performed conventional suturing techniques. It is concluded that the mechanical performance may not be the best indicator of success of the surgical repair, as long as the device is able to anatomically reduce the tear.