Scope:
This benchtop provides empirical evidence for the continued structural integrity of the devices when subjected to mechanical torsion replicating in vivo conditions. The test is accelerated to obtain results in less time than physiological rates would allow. The test may be conducted under simulated physiological conditions with saline at 37C.
Objective:
The testing objective is to meet the appropriate standard requirements, as identified by the device manufacturer and may include ISO guidelines (25539-1, 7198:1998, and 99128), for in vitro mechanical fatigue. The test demonstrates the device integrity when subjected to torsion for an appropriate posti-implantation time perdiod, fatigue tests will be conducted for minimum of 10 years post-implantation while feasibility or strength characterization tests may be shorter. 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 and provide acceptance and/or failure criteria.
Equipment:
The test system utilizes a torsion 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 torsion fixture makes the single axis rotary motion available to all 16 devices. Torsion testing can also be combined with tension/compression testing, please see our In Vitro Simulated Gait Motion page for more details.
| Device OD | Mock Artery # | Rotation | Frequency* |
| 1.5mm- 10mm | 16 | 1° - 100° | 1Hz - 10Hz |
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:
The test equipment software monitors the cycle count, displacement, and pressure throughout the duration of the test. MDT engineers monitor the test daily and record the temperature and pressure for the system, as well as the outside radial strain at predetermined positions for each device being tested. MDT sends weekly updates to ensure customers are apprised of the status of their test. Updates include raw data collected throughout the week for the customer's analysis.
Inspections & Services Offered:
MDT offers several inspection and monitoring methods including:
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 by MDT are clearly marked as such. Any 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.
