Impact Performance of Medical Implants
Successful completion of certain surgical procedures, such as vertebrae fusions, and hip or knee replacements, require the use of implants. During the course of these procedures the implants are subjected to repeated impacts from the implanting – extracting tools or from surrounding bones and tissue. A mechanical failure with the implant may lead to complications during surgery, such as unwanted debris in the surgical field; excessive trauma to surrounding bone or tissue, and it may require the patient to spend a longer period of time under anesthesia, possibly leading to a longer recovery time.
It is critical for manufacturers of medical implants to earn the confidence and respect of surgeons by providing a product that has been thoroughly tested under end-use conditions. Without sophisticated testing equipment, manufactures may not be able to accurately simulate force, geometries and other impact characteristics that the implants may be subjected to in the operating room.
In order to identify areas of the implant most likely to fail, we set up a test, which simulated surgical impact conditions, on our CEAST 9350. Custom fixturing was assembled to grip the implant - in this case a vertebrae fusion cage - and a 1/8-inch hemispherical tup insert, which replicated the implant tool, was used. We also installed the Anti-Rebound Device to prevent secondary impacts on the implant.
The DAS (Data Acquistion System) and Visual Impact software were set up to enable the tower to perform automatic testing – effectively reproducing the same motions of a surgeon repeatedly striking the implant with the implant tool.
Impact resistance is one of the most important properties for component designers to consider, as well as the most difficult to quantify. Impact resistance is a critical measure of service life and more importantly these days, it involves the perplexing problem of product safety and liability. With the combined experience of Dynatup® and CEAST, Instron® has more than 80 years experience in designing impact testing systems to simulate real-life impact conditions.
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