A biomechanical study of four different meniscal repair systems, comparing pull-out strengths and gapping under cyclic loading.
Most studies comparing the biomechanical properties of different meniscal repair systems have simply investigated load to failure. Meniscal tissue is highly anisotropic, and far weaker under tension in the radial direction. Radially oriented loading to failure may not therefore be the most physiologically relevant in vitro test for repair of circumferential tears, and determining gapping across repair sites under cyclical loading at lower loads may be of greater importance. Using bovine menisci, vertical circumferential incisions were repaired using a simple vertical 2-0 PDS suture, Meniscal Arrow, Meniscal Fastener or T-Fix. Repairs were tested by simple loading to failure in a materials testing machine, and by cyclic loading between 5 and 10 N for 25 cycles. Initial gapping across the repairs was measured using a digital micrometer, and the increase in gapping under cyclic loading measured using a Differential Voltage Reluctance Transducer. The mean loads to failure for each of the repair groups were: sutures 72.7 N, Arrows 34.2 N, Fasteners 40.8 N and T-Fix 49.1 N. The load to failure was significantly greater with sutures than with Arrows or Fasteners. The mean gapping across the repairs for each of the repair groups after 25 loading cycles were: sutures 3.29 mm, Arrows 2.18 mm, Fasteners 3.99 mm and T-Fix 3.47 mm. The mean gapping was significantly less with Arrows than with Sutures, Fasteners or T-Fix. These results confirm that meniscal repair by suturing gives the highest load to failure, but show that Arrows give superior hold under lower loads, with the least gapping across repairs under cyclic loading of the four methods tested.