Pulsating compressive strength tests (R=0.1) are performed on six specimens with a test frequency of up to 5 Hz. Result: Generation of an S-N curve with a number of cycles up to 5 million. This corresponds to approximately 2 years in vivo; approximately 7000 cycles per day. The first runout is confirmed.
In addition to purely axial tensile, compression and flexure tests, a pure or combined torsion load can be applied to spinal systems in compliance with standards including ASTM F1717-9, ASTM F2706-8 or ISO 12189-08.
- ASTM F1717-9 Standard test Methods for Spinal Implant Constructs in a Vertebrectomy Model
- ASTM F2706-8 Standard Test Methods for Occipital-Cervical and Occipital-Cervical-Thoracic Spinal Implant Constructs in a Vertebrectomy Model
- ISO 12189-8 Implants for surgery – Mechanical testing of implantable spinal devices – Fatigue test method for spinal implant assemblies using an anterior support
These tests can be performed under physiological (in-vivo) conditions (for example, tempered saline solution) using a ZwickRoell thermoregulation bath.
For practical statistical evaluations of fatigue tests in the finite life range (high cycle fatigue) and in the transitional range to infinite life (long life fatigue), ZwickRoell offers the technical-scientific program SAFD (Statistical Analysis of Fatigue Data).
For static and dynamic tests on spinal implants in a vertebrectomy model to ASTM F1717-9. A spinal implant, usually consisting of a screw and rod system, is tested under static and dynamic loads.
The implants are mounted on a vertebral replacement test block made of ultra-high molecular weight polyethylene (UHMWPE). The use of simulated vertebral bodies improves the reproducibility of the tests compared to those using human material.