This benchtop test provides empirical evidence for the continued structural integrity of the devices when subjected to mechanical fatigue. The test is accelerated to obtain results in less time than physiological rates would allow. Two typical types of tests for these devices are lateral distraction and longitudinal shear fatigue testing.
Testing objective is determining the lateral distraction resistance and the longitudinal shear resistance of sternal closure devices. The protocol is developed according to Wansgard et al, “Fatigue testing of three peristernal median sternotomy closure techniques”, J Cardiothorac Surg, 2008. Lateral distraction loading simulates breathing and coughing in a patient, while longitudinal shear simulates lateral flexion stretching, lying on one’s side, or supporting the body on one vertically oriented arm. A device failure is defined by the device manufacturer (for example, any visibly cracked or broken lead, or a change in conductivity / DC resistance). The device manufacturer will also examine the devices post-testing against the acceptance and/or failure criteria.
The test system utilizes special fixtures designed by MDT that are integrated with either an MTS Servohydraulic Tester or an EnduraTEC Servopneumatic Fatigue Tester. Two specialized fixtures were developed by MDT for these tests: a longitudinal shear fixture and a lateral distraction fixture (see pictures).
MDT tests are conducted in accordance with ANSI/ISO/IEC 17025-2005. Testing schedules and resource needs are determined during project kickoff meetings with MDT engineers and the customer. Services are performed in accordance with standard operating procedures and test protocols specific to the project. 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.
The test equipment software monitors the cycle count and displacement 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.
Inspection Services Offered:
MDT offers several inspection and monitoring methods including:
• High speed video inspection of devices or fixture validation
• Visual Inspections
Tests are conducted in accordance with ANSI/ISO/IEC 17025-2005. In compliance with this standard, MDT test reports include comprehensive documentation and summary 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, and other information collected during the test (see example test reports).
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.