ASTM F2267 – Standard Test Method for Measuring Load Induced Subsidence of Intervertebral Body Fusion Device Under Static Axial Compression
This test method specifies the materials and methods for the axial compressive subsidence testing of non-biologic intervertebral body fusion devices, spinal implants designed to promote arthrodesis at a given spinal motion segment. This test method is intended to provide a basis for the mechanical comparison among past, present, and future non-biologic intervertebral body fusion devices. This test method is intended to enable the user to mechanically compare intervertebral body fusion devices and does not purport to provide performance standards for intervertebral body fusion devices. This test method describes a static test method by specifying a load type and a specific method of applying this load. This test method is designed to allow for the comparative evaluation of intervertebral body fusion devices.
Intervertebral body fusion devices are generally simple geometric shaped devices, which are often porous or hollow in nature. Their function is to support the anterior column of the spine to facilitate arthrodesis of the motion segment. This test method is designed to quantify the subsidence characteristics of different designs of intervertebral body fusion devices since this is a potential clinical failure mode. These tests are conducted in vitro in order to simplify the comparison of simulated vertebral body subsidence induced by the intervertebral body fusion devices. The static axial compressive loads that will be applied to the intervertebral body fusion devices and test blocks will differ from the complex loading seen in vivo, and therefore, the results from this test method may not be used to directly predict in vivo performance. The results, however, can be used to compare the varying degrees of subsidence between different intervertebral body fusion device designs for a given density of simulated bone.
All tests shall have a minimum of five (5) test samples. The Yield point location is the intersection point between the test data and the offset line. The offset line runs parallel to the first linear section of the test data. The offset line location is 1 mm for cervical disc devices, 1.5 mm for thoracic devices and 2 mm for lumbar devices. Example of test results are shown below.