Cyclic testing of meniscal sutures

Suturing the meniscus has become a standard procedure for repairable tears. Studies investigating the outcome of meniscal sutures report a considerabl e rate of failures. Regarding the indications, which have been extended to the avascular zones, and regarding some accelerated rehabilitation protocol s, the need for further in vitro investigations has become obvious. The aim of this study was to compare different meniscal suture types (vertical and horizontal mattress sutures) and materials (absorbable monofilament PDS 2- 0, and nonabsorbable braided Ethibond 2-0 [Ethicon, Somerville, NJ]) under standard and cyclic loading conditions. Testing was performed on medial por cine menisci. In group A, specimens were tested to failure at a cross-head speed of 50 mm/minute. In group B, cyclic testing (100 cycles) was performe d first within different load intervals (5 to 20 N and 5 to 40 N). Finally, the specimens were loaded until failure. In both groups, the failure loads were recorded and the failure modes were analyzed. In group A, there was n o difference between suture type or suture material, with a mean failure lo ad of 60 N. The failure modes were significantly different for vertical (10 0% suture failure) and horizontal sutures (50% suture failure) (P < .0001). In group B, 13% of the sutures failed under cyclic loading (7 with 40-N lo ad, 1 with 20-N load). The gap of the sutured tear that appeared within the first load cycles was broader in horizontal sutures (P < .001). During the first cycles, the thread cut through the meniscus tissue and disappeared f rom the surface (partial tissue failure). There was no difference according to suture material. The ultimate failure loads after cyclic loadings did n ot differ from the values of group A. These results show that meniscal sutu res may fail under repetitive loading conditions and that a gap appears bet ween the meniscal margins within the first loading cycles irrespective of t he suture type and suture material used. The appearance of the gap and sutu re disappearance on the meniscal surface because of partial tissue failures (which were more pronounced in the horizontal sutures) confirmed the super ior resistance of meniscal tissue to vertical sutures.