Elongation and Structural Properties of Meniscus Repair Using Suture Techniques in Distraction and Shear Force Scenarios

Introduction: Meniscal debridement remains the most commonly performed orthopaedic surgery in the US, even though several clinical long term studies have shown that total or partial meniscectomy may lead to cartilage degeneration and early onset of osteoarthritic changes. Repair should be considered depending on the type and the location of the meniscal tear. Good and excellent results have been obtained in the repair of peripheral meniscus tears in the vascularized zone (red-redzone). Several basic research studies have evaluated the structural properties of meniscal repair constructs. Most commonly, these studies test a “worst case scenario” or distraction test where the load is applied parallel to the axis of the tested fixation device. Frequently, meniscal injuries occur secondary to a rotational force in combination with an axial load. This may pull the central part of the meniscus while the peripheral part of the meniscus is still attached to the joint capsule and thereby leading to a rupture. The force directions can be subdivided into sagittal and coronal forces. The resulting force vector is in an oblique direction thereby matching the definition of a shear force scenario. The purpose of the current study was therefore to evaluate structural properties and elongation of meniscal repair using horizontal and vertical suture techniques after being subjected to a cyclic loading protocol in a distraction and in a shear force scenario. We hypothesized, that a vertical suture technique for meniscal repair subjected to cyclic loading in a shear force scenario will result in significantly less elongation when compared to horizontal sutures. Methods: In this study 40 fresh frozen porcine menisci were repaired using horizontal (group 1) and vertical (group 2) loop sutures using 2-0 Ethibond (Ethicon, Norderstedt, Germany) in an outside-in technique. The menisci were mounted in a custom made tissue clamp. In part one of the study, the loads were applied in line with the axis of the implants to simulate a distraction case scenario (Fig.1a). In part two, the repair complexes were subjected to shear forces with the load applied perpendicular to the repair complex (Fig.1b). Each meniscusimplant/suture construct was subjected to 1000 cycles of a load between 5 and 20 N and subsequently loaded to failure at a cross head speed of 12.5 mm/sec. Elongation after 100, 500, and 1000 cycles of load, ultimate failure load, mode of failure and stiffness were recorded. Data were analyzed using an ANOVA test with the level of significance set at p<0.05.