Scope:
This benchtop test provides empirical evidence for the continued structural integrity of the devices when subjected to mechanical fatigue replicating in vivo conditions. The test is designed to simulate the device radial fatigue due to expansion and contraction of the surrounding vessel. Physiological strain of a healthy vessel is first modeled using mock arteries implanted with the device. The test is then accelerated to obtain results in less time than physiological rates would allow. The test is conducted under simulated physiological conditions with saline at 37C.

 Objective:
The testing objective is to meet the appropriate requirements, as identified by the device manufacturer, for in vitro mechanical fatigue. The test demonstrates the device integrity when subjected to torsional, axial, and bending mechanical motion for a minimum of 10 years post-implantation. A device failure is defined by the device manufacturer; for example, any broken or cracked strut visible at 30x magnification during or at the end of the test. The device manufacturer will also examine the devices post-testing against the acceptance and/or failure criteria.

Equipment:
The test system utilizes a gait fixture designed by MDT that is integrated with an ElectroForce® 3300 Test Instrument. The ELectroForce tester operates using linear and rotary motors rated 2250N (500 lbs) and 28.2 Nm (250 in-lbs) respectively.  MDT’s gait motion fixture converts the linear/rotary motion into a simulated gait motion. The fixture first applies tension to 16devices and then compresses and bends them simultaneously; The process is then reversed and the cycle repeated at a 2Hz typical frequency to provide a full 10 million cycle test (10 years post-implantation) in less than 2 months.

Test Protocol & Set Up:
MDT tests are conducted in accordance with ANSI/ISO/IEC 17025-2005. Testing schedules and resource needs are determined during project kick off meetings with MDT engineers and the customer. The services are performed in accordance with standard operating procedures and test protocols specific to the service. Standard tests do not begin without a protocol signed by both the customer and an MDT representative. For feasibility or non-standard tests MDT will develop a method and protocol with customer input and will review the final process with the customer prior to initiation of the test. Click here to view a sample Test Protocol.

Test Monitoring & Weekly Updates:
WinTest software monitors parameters such as the cycle count and displacement throughout the duration of the test. MDT engineers monitor the test daily and record various system parameters, as well as other customer identified parameters such as; load, displacement, and rotation. MDT sends weekly customer updates to ensure you have the up to date status of your test. Updates include raw data collected throughout the week for your analysis.

Inspections & Services Offered:

MDT offers several inspection methods including:

• Endoscopic inspections with photo, video, or written documentation (mock arteries must be removed from the tester to gain access to the inner lumen)
• High-speed video inspection of devices or fixture validation
• Visual Inspections

Test Reports:
MDT tests are conducted in accordance with ANSI/ISO/IEC 17025-2005. In compliance with this standard, MDT test reports include comprehensive documentation of the test protocol and results. Any test method deviations, additions or exclusions are documented and reviewed with the customer prior to beginning the test. Information within the report includes the specific test conditions, statements of compliance with test protocol and the estimated measurement uncertainty.   The reported results only relate to the items tested. Any opinions and interpretations provided will be clearly marked as such in the test report. Additional information required by customer specific methods will also be noted. At the conclusion of the test MDT provides the customer with a Microsoft Windows formatted CD containing copies of all raw data, inspection results, or other information collected during the test. Click here to view a sample Test Report.

Please take a few moments to tell us more about your device and test requirements in our short questionnaire, and we will be happy to provide you with a quote.