Tensile Testing of Surgical Sutures
Methods and Equipment for Suture Testing
Sutures are some the most commonly used hospital consumables. Used in most surgeries and wound closures to join body tissues, sutures are typically either absorbable, meaning they will naturally decompose after the wound has healed, or non-absorbable and need to be removed by a physician. They can also be coated or non-coated, with a coating typically exhibiting antibiotic properties to reduce the chances of infection.
It is extremely important that suture manufacturers are confident in the tensile strength of their products. Sutures are first subjected to tensile strength during the application process and then need to maintain near constant tension on tissues while the healing process occurs. The risks of failure are high: sutures used internally can cause internal bleeding or other fatal complications should they break or become too slack.
Tensile properties can change depending on the material, size, and coating of the suture. Though the ASTM and ISO organizations do not have a standard specifically dedicated to the testing of sutures, biomedical manufacturers still perform tensile tests in order to obtain a full mechanical profile. Tensile tests are typically performed on the suture with and without a knot to mimic real world use.
Most biomedical testing is performed on a single column materials testing system such as Instron's 3400 Series. Though suture testing typically only requires maximum load measurements, more advanced testing systems such as Instron's 6800 Series can be a better choice for labs with multiple testing applications. For those with high throughput needs, Instron's AT6 automation system can be configured for testing sutures along with many other materials.
|Suture Test Setup|
|1)||3400 Series Universal Testing System
|2)||Bluehill Universal Software
|3)||2530 Series Load Cell
|4)||2712-041 Pneumatic Side-Action Grips
The most challenging part of suture testing is finding the correct gripping solution. Coated sutures can be extremely slippery, requiring special gripping surfaces to maintain contact until failure. Instron has many different jaw face options with surfaces that are purposefully designed for slippery materials. Pneumatic cord and yarn grips are the best solution for smaller diameter products, whereas larger sutures can be tested using pneumatic side action grips. Suture size is highly dependent on the application, with the smallest sutures being only 0.01 mm in diameter and the largest going up to 1 mm in diameter. Because of this, load cell capacity can range from approximately 10 N to 500 N.