Impact Tests On Orthopedic Implants

A medical condition called Osteoarthritis is caused when there is minimal joint moment in human body. Lack of joint moment can result into damaged or dysfunctional joints. Orthopedic implants are designed to replace the damaged joint (s) and increase the mobility of an affected part in the human body. To name a few, implants used for hip, knee, shoulder or elbow joints are commonly made of stainless steel. It is important for manufacturers of such orthopedic implants to test their components (various implants) to characterize the impact resistance of their product.

Instron 9400 series is a good fit for such a testing requirement. Since the implants for various body parts are of different shapes & sizes, the testing has to be performed using various custom fixtures. We used a T-slot plate which was bolted at the bottom of 9450. A custom fixture with a clamped knee implant was mounted on the T-slot plate at base of the tower. A 45 kN strain gauge striker was used to impact the knee implant. A Data Acquisition System (DAS) and Bluehill Impact software were used in conjunction with the drop impact machine to collect the force/velocity data and analyze the impact performance.

Alternatively a general purpose plate as seen in the picture can be used instead of a T-slot plate.These versatile plates give flexibility to manufacturers to mount a wide range of custom fixtures as per their own requirements. Such impact tests can be customized to an extent where they can replicate the real life low and high velocity impacts during the actual surgical procedures.

Note: The customer's actual test set up is confidential and hence is not displayed in this application note.