The tensile strength of different methods of anterior cruciate ligament graft end stitches in an animal model

Abstract

Background

There are several methods for stitching graft ends in anterior cruciate ligament reconstructive surgery. The tendon-suture construct should be able to withstand tensioning until the graft is stabilized with an implant.

Methods

In this biomechanical study, 40 porcine lower extremity tendons ends were stitched with No. 2 suture, secured to the grips of the Zwick-Roell testing machine and tested for load at failure and type of failure (tendon v/s suture thread). The applied force was linear, the results are given in Newtons (N) as a mean. The Mann-Whitney U test was used for statistical analysis. The following constructs were compared: a whipstitch of each tendon end individually with 3, 4, and 5 passes through the tendon, a whipstitch of both tendon ends folded together and a tendon end knot without stitching.

Results

All specimens survived the minimum tensile load of 80 N. The load at failure for whipstitch with 3,4 and 5 passes were 175 N, 211 N and 254 N respectively. The load at failure was greater for individual whipstitch than for both ends folded together (261 N v/s 152 N). The mean load at failure for braided graft was 209 N. The braided graft slips off the tendon before failure leading to uneven strength distribution during tensioning.

Conclusion

Increasing number of suture passes resulted in higher load at failure. Individual tendon ends whipstitched with 5 passes was the strongest construct. All of the investigated techniques are sufficient to withstand the suggested optimal graft tension of 80 N.