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[Mechanical study of spinal interbody implants--characteristics and limits of standardized testing]
E Steinhauser1, R Bader, H Rechl
1Klinik für Orthopädie und Sportorthopädie, Technische Universität München. erwin.steinhauser@lrz.tum.de
Biomedizinische Technik. Biomedical Engineering
|January 10, 2002
Summary
This study tested carbon fibre reinforced polymer (CFRP) spinal fusion cages, finding adequate strength for the implant body. However, surgical technique modifications are crucial to protect the cage's table-tracks from failure under physiological loads.
Area of Science:
- Orthopedic biomechanics
- Biomaterials science
- Spinal surgery
Context:
- Spinal interbody fusion increasingly utilizes implants made of metal or reinforced polymers.
- A standardized mechanical testing setup based on ASTM proposals was adapted for spinal interbody implants.
- Carbon fibre reinforced polymer (CFRP) lumbar fusion cages were evaluated.
Purpose:
- To mechanically evaluate the axial compression, shear, and torsional strengths of CFRP spinal interbody fusion cages.
- To assess the performance of the implant's table-track features under various loads.
- To determine the implications of implant design and mechanical testing on surgical technique.
Summary:
- CFRP cages demonstrated sufficient axial compression, shear, and torsional strength in their main body.
- The table-tracks on the cages had a lower maximum axial compression tolerance than potential physiological lumbar spine loading.
- Modifications to the surgical technique, involving intra-operative grooving of vertebral end plates, are necessary to protect the table-tracks.
Impact:
- The study highlights the importance of specific surgical techniques for successful implantation of CFRP cages to prevent in vivo failure.
- Proper surgical technique ensures axial compressive loads are directed to the implant body, safeguarding the table-tracks.
- Combined with supplementary instrumentation, this technique is expected to prevent in vivo failure of the table-tracks under physiological spinal loading.