Measurement of stress-strain relationship and stress relaxation in various synthetic ligaments.

In an experimental study various synthetic augmentation devices for knee ligament surgery were tested in a servo-mechanical universal tensile testing machine under uniaxial loading. Two tests were done to elucidate the mechanical behaviour: stress relaxation and stress-strain relationship. Regarding the point of failure or rupture, the strongest ligament was the Trevira at 1800 N, followed by the 8-mm-wide Kennedy LAD at 1720 N. At a working load of 500 N the Gore-tex band, the Trevira, and the Kennedy-LAD stretched by between 2% and 3%. For synthetic augmentation in repair of proximally ruptured anterior cruciate ligaments we recommend a synthetic ligament that reaches failure point at a load of more than 1000 N with an alteration in length of less than 5%. Otherwise, stress protection of the biological reconstruction in full extension will be impossible. The requisite criteria were fulfilled by the Trevira, Kennedy-LAD and Gore-tex synthetic ligaments.