Measuring the strength of knotted suture materials

There is no international standard method for measuring the strength of knotted suture materials, and although several methods have been published, there has been minimal investigation on the effects of test variables on measured properties (e.g. speed, gauge length, and knot tensioning force). Methods investigated in this work were the “ear method” (with and without a rod inside the loop), and the “cut-loop and ear method”. The test environment, material, and type of knot were constant. Effects of varying gauge length, test speed, and knot-tensioning force on tenacity and strain were investigated and compared with data for nonknotted sutures. Different values of tenacity and strain were evident for the different test methods; lower values of tenacity for specimens with shorter gauge lengths and tested at greater speeds; lower values of strain for specimens with longer gauge lengths and tested at greater speeds. Thus, tensile properties of suture materials tested at one gauge length or one test speed, as widely reported in the literature, may be misleading. Knot tensioning force neither affect tenacity nor strain.