Element’s mechanical testing capabilities extend to fusion and non-fusion spinal devices, as well as predicate components, for feasibility testing and regulatory submission requirements.
Common testing for spinal implants includes static and fatigue tests in a variety of loading modes, such as axial, torsional, shear, flexion/extension, bending, lateral bending, and axial rotation.
Typical components tested include:
- Interbody fusion devices (IBFDs)
- Cervical and Lumbar cages
- Vertebral Body Replacements (VBRs)
- Artificial disc replacements
- Interspinous implants
- Plate and screw systems
- Rod and screw systems
Spinal Cage Testing
Spinal cages are used to encourage interbody fusion by being fixated in the disc space and encouraging the growth of bone graft. Element utilizes both ASTM F2077 and ASTM F2267 to characterize the mechanical properties of these IBFDs and VBRs.
Static and Dynamic Testing (ASTM F2077): This method calls for various tests to determine mechanical properties, including static and dynamic compression, torsion, and shear. Prior to testing, profiled test pucks are manufactured to precisely mimic the profile of the device. These pucks are then affixed to the test frame along with the specimens, which are tested either statically or dynamically. Dynamic testing is generally performed in-vitro using saline solution to allow for SEM evaluation of the particulate generated during testing. In addition, mass-loss evaluations are performed to characterize the rate of wear during testing.Load Induced Subsidence Testing (ASTM F2267): This static axial compression test is performed to determine the likelihood of implant subsidence when subjected to compressive forces. Per ASTM F2267, the sample is placed between two Polyurethane test blocks and loaded until failure is achieved.
Spinal Construct Testing
Spinal constructs generally consist of a combination of rods, hooks, screws, and connectors. Depending upon the intended goal, device designs can vary greatly. By using standardized test methods, mechanical properties can be compared across designs.
Spinal Implant Constructs in a Vertebrectomy Model (ASTM F1717): This standard outlines the requirements for static and dynamic characterization. Prior to testing, the construct is carefully assembled and fixated to a pair of test blocks. These assemblies are then subjected to static or dynamic loading. ASTM F1717 specifies three static test methods: compression, torsion, and tension. The standard also calls for a dynamic compression curve consisting of at least two run-outs to 5,000,000 cycles under a constant axial load. Two additional pairs of constructs are tested at higher load levels to complete the curve.
For Occipital-Cervical and Occipital-Cervical-Thoracic constructs, ASTM F2706 provides additional static and fatigue test methods for these specific device types.
Subassemblies Used in Spinal Arthrodesis Implants (ASTM F1798): This test method evaluates the various subassemblies and interconnection mechanisms used in spinal implants, such as rods, hooks, screws, and bands. The goal of ASTM F1798 is to determine the fatigue strength and resistance to loosening during arthrodesis, or fusion. Loading methods include: static A-P load (Fx), transverse load (Fy), axial gripping capacity (Fz), transverse moment (My), and axial torque (Fz).
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