ASTM F2706 Occipital-cervical and occipital-cervical-thoracic spinal implant constructs
We offer test methods for the mechanical characterization of occipital-cervical and occipital-cervical-thoracal spinal implants in a vertebrectomy model according to ASTM F2706. These implants consist of several components that are designed to stabilize the spine during the process of arthrodesis. For all test methods, a vertbrectomy model is used in which the implants are connected superiorly and inferiorly with test-blocks made of polyacetal and a defined gap between the blocks simulating the absence of a vertebral body. The geometry of the test-blocks is specific to the intended implantation site and the type of connection to the spine. From the following range, we will select the appropriate test procedures for your individual spinal implants:
- Static test methods
1. Bending test under compression or tension:
The implants are connected to the respective test-blocks and a displacement of max. 25 mm/min is applied to one of the test-blocks. Depending on the direction of displacement, the construct is loaded under compression or tension. The respective force-displacement curve is recorded and evaluated with regard to the mechanical properties (including stiffness and strength) under pressure and tension.
2. Mechanical properties under rotation:
The implants are connected to the respective test-blocks and a torque of max. 60 °/min is applied to one of the test-blocks. The torque- angle curve is recorded and evaluated with regard to the mechanical properties (including stiffness and strength).
- Dynamic test method
Following the static tests, the tests are performed dynamically with new test specimens over 5 million cycles. The maximum load should be 25, 50 or 75% of the respective maximum load. In addition, a constant ratio of the maximum to the minimum load of R = 10 for the dynamic bending test and R = -1 for the rotational tests should be ensured. The dynamic examination is repeated with different maximum loads until the difference between two loads, at which the implant dynamically fails or survives, is less than 10%. The test is completed when 5 million load cycles are reached or a mechanical failure of the implants occurs. The tests should be carried out under laboratory conditions (air and room temperature), but can also be repeated in Ringer solution at 37 °C, if necessary, in order to simulate the physiological ambient conditions and to consider possible corrosive effects.