Torsion of monofilament and polyfilament sutures under tension decreases suture strength and increases risk of suture fracture.

BACKGROUND A continuous running suture is the preferential method for abdominal closure. In this technique the suture is secured with an initial knot and successive tissue bites are taken. At each tissue bite, the needle is rotated through the tissue; in doing so, the suture can twist around the knot which acts as an anchor. OBJECTIVE To determine the effect of axial torsional forces on sutures used in abdominal closure. METHODS The effect of axial twisting on polydioxanone (PDS*II), polyglactin (Vicryl), polypropylene (Prolene) and nylon (Ethilon) sutures was investigated using a uniaxial testing device. RESULTS The maximum tensile force withstood for untwisted sutures was determined: polydioxanone failed at a tensile force of 116.4±0.84 N, polyglactin failed at 113.9±2.4 N, polypropylene failed at 71.1±1.5 N and nylon failed at 61.8±0.5 N. Twisting decreased the maximum tensile force of all sutures; one complete twist per 10 mm (i.e., 15 twists) decreased the tensile strength of polydioxanone by 21%, polyglactin by 23%, polypropylene by 16% and nylon by 13%, p<0.001. Excessive twisting caused a nonlinear decrease in suture strength, with one twist per 75 mm (i.e., 20 twists) of polydioxanone decreasing strength by 39%, P<0.001. CONCLUSION The effect of excessive twisting on the mechanical properties of sutures is a previously unrecognised phenomenon. Surgeons should be aware that this can result in a decrease in suture strength and reduce the elasticity of the material, and therefore need to adapt their practice to reduce the torsional force placed on sutures.