Mechanics of the ideal surgical knot

Researchers have published a first study on the mechanics of surgical knots, with results that could be used to train surgeons to tie stronger, safer sutures - a skill that usually requires years of practice to master. Think about the last time you tied your shoe: maybe you tied it tightly, or tied multiple knots to ensure the laces wouldn't come undone. You likely relied on intuition to tell you how much tension to apply to keep the laces from untying, without pulling hard enough to break them. Perhaps surprisingly, surgeons also take an intuitive approach to knotting sutures. While simple square and granny sliding knots are often used in surgery, it takes years to master them so that they stay in place without loosening or breaking. Much mathematical research has been done on knot topology and geometry, but little is known about knot mechanics in the context of physical variables, like the material properties of knotted filaments. "It's astonishing to think how much we rely on knots, when we don't really understand how they work," says Pedro Reis, head of the Flexible Structures Lab in the School of Engineering (Institute of Mechanical Engineering).