Pull-out and shear failure strengths of arthroscopic meniscal repair systems

Meniscal repair is common and recommended in young patients. Suture techniques and fixation devices were developed for stronger, more facile repairs. Three devices (T-Fix, Meniscal Staple, Meniscus Arrow) were biomechanically compared to horizontal PDS suture. Peripheral tears were created in porcine menisci and repaired using the manufacturer's technique. An Instron was used to distract the menisci at 50 mm/min in axial-pullout and longitudinal shear loads. Load to failure curves and peak failure loads were noted. Load to failure in axially loaded pull-out mode was: Staple, 4.195+/-3.70 N; Arrow, 39.755+/-11.37 N; T-Fix, 45.892+/-13.99 N; Suture, 107.65+/-22.37 N. Analysis of variance with post hoc testing revealed Staple failure at lower load than all devices and Suture failure at higher loads than all devices; Arrow and T-Fix were similar. The data varied significantly from that obtained in shear. Shear loads to failure were: Staple, 8.39+/-8.62 N; Arrow, 27.67+/-14.33 N; T-Fix, 57.47+/-17.05 N; Suture, 64.15+/-17.05 N. Analysis of variance, power analysis, and pair-wise multiple comparisons revealed significant differences between: Suture and Staple, Suture and Arrow, and T-Fix and Staple. No differences were noted between Suture and T-Fix, T-Fix and Arrow, or Arrow and Staple. In pullout, Suture and T-Fix maintained better apposition at low loads. As load increased, the menisci separated until device failure. Arrows allowed low load separation but held tissue until failure. Staples failed at low load. For shear, the menisci attempted to reorient parallel to the force. The devices failed in a pull-slide pattern. Suture failed by pull-through. Meniscal repair devices are easy to use and may provide resistance to shear and pull out. The resistance to pullout loads was very different than the resistance to longitudinal shear loads.