Investigation of the Size Effect on Implant Fatigue Behavior in Intervertebral Cage Design Using the FEA Method

Öz

This study examines the biomechanical performance of intervertebral cage implants with different sizes and materials using the finite element analysis method. Static analysis revealed the impact of implant size and material type on the stress distribution in the spine, and it was determined that Ti alloy implants induce higher stresses compared to PEEK implants. While small-sized implants exhibited higher stress concentrations, larger implants distributed the load more evenly. Fatigue analyses based on the Goodman criterion indicated that implant size is a decisive factor in fatigue strength. In Ti alloy implants, the highest equivalent alternating stress values were observed in the larger designs, thereby reducing fatigue life. PEEK implants, owing to their lower stiffness, reduced the stress shield but resulted in greater deformation in the screw systems. In the M1 titanium cage, the highest equivalent alternating stress was recorded as 340.88 MPa, indicating reduced fatigue resistance in smaller implant designs. Conversely, the M3 PEEK cage exhibited the lowest stress value (32.31 MPa), demonstrating the benefit of larger, more compliant structures in distributing load effectively. The results demonstrate that in the design of intervertebral cages, the choice of size and material is critical for mechanical stability and long-term implant success. While larger implants optimize load distribution, material selection must be carefully evaluated to achieve biomechanical balance.

Anahtar Kelimeler

• Intervertebral cage
• Finite Element Analysis
• Fatigue Strength Spinal Biomechanics

FEA Yöntemi Kullanılarak Omurlar Arası Kafes Tasarımında İmplant Yorulma Davranışı Üzerindeki Boyut Etkisinin Araştırılması

Öz

Bu çalışma, farklı boyut ve malzeme kombinasyonlarına sahip intervertebral cage (omurlar arası kafes) implantlarının biyomekanik performansını sonlu elemanlar analizi (FEA) yöntemiyle incelemektedir. Statik analizler, implant boyutu ve malzeme türünün omurga üzerindeki gerilme dağılımını önemli ölçüde etkilediğini ortaya koymuş; titanyum alaşımlı implantların, PEEK implantlara kıyasla daha yüksek gerilmeler oluşturduğu belirlenmiştir. Küçük boyutlu implantlar daha yüksek gerilme yoğunlaşmaları gösterirken, büyük implantlar yükü daha dengeli bir şekilde dağıtmıştır. Goodman kriterine dayalı yorulma analizleri, implant boyutunun yorulma dayanımı üzerinde belirleyici bir faktör olduğunu göstermiştir. Titanyum alaşımlı implantlarda, en yüksek eşdeğer alternatif gerilme değerleri büyük tasarımlarda gözlemlenmiş ve bu durum yorulma ömrünün azalmasına neden olmuştur. Düşük elastikiyet modülüne sahip olan PEEK implantlar, stres korumayı azaltmış ancak vida sistemlerinde daha fazla deformasyona yol açmıştır. Özellikle, M1 titanyum kafeste en yüksek eşdeğer alternatif gerilme değeri 340,88 MPa olarak kaydedilmiş, bu da küçük boyutlu implantların yorulma direncinin düşük olduğunu göstermiştir. Buna karşılık, M3 PEEK kafes en düşük gerilme değerini (32,31 MPa) göstermiş ve daha büyük, esnek yapıların yükü daha etkili dağıttığını ortaya koymuştur. Elde edilen sonuçlar, intervertebral kafes tasarımında boyut ve malzeme seçiminin, mekanik stabilite ve uzun vadeli implant başarısı açısından kritik öneme sahip olduğunu ortaya koymaktadır. Daha büyük implantlar yük dağılımını optimize etse de biyomekanik dengeyi sağlamak adına malzeme seçimi dikkatle değerlendirilmelidir.

Anahtar Kelimeler

• Omurlar Arası Kafes
• Sonlu Elemanlar Analizi
• Yorulma Dayanımı
• Spinal Biyomekani

Kaynakça

1. Amiri, S., Naserkhaki, S., & Parnianpour, M. (2019). Effect of whole-body vibration and sitting configurations on lumbar spinal loads of vehicle occupants. Comput Biol Med, 107, 292–301. Scopus. https://doi.org/10.1016/j.compbiomed.2019.02.019
2. Cheng, X., Bai, J., & Wang, T. (2023). Biomimetic Design of Fatigue-Testing Fixture for Artificial Cervical Disc Prostheses. Metals, 13(2), 299. https://doi.org/10.3390/met13020299
3. Chong, E., Pelletier, M. H., Mobbs, R. J., & Walsh, W. R. (2015). The design evolution of interbody cages in anterior cervical discectomy and fusion: A systematic review Orthopedics and biomechanics. BMC Musculos Disord, 16(1). https://doi.org/10.1186/s12891-015-0546-x
4. Chuah, H. G., Rahim, I. A., & Yusof, M. I. (2010). Topology optimisation of spinal interbody cage for reducing stress shielding effect. Comput Methods Biomech and Biomed Engin, 13(3), 319–326. https://doi.org/10.1080/10255840903208189
5. Committee, A. H. (1996). Fatigue Fract. ASM International. https://doi.org/10.31399/asm.hb.v19.9781627081931
6. De Bartolo, L., Morelli, S., Bader, A., & Drioli, E. (2001). The influence of polymeric membrane surface free energy on cell metabolic functions. J Mater Science: Materials in Medicine, 12(10–12), 959–963. Scopus. https://doi.org/10.1023/A:1012857031409
7. De Biase, G., Gruenbaum, B. F., Bojaxhi, E., Patterson, J. S., Sabetta, K., Quinones-Hinojosa, A., & Abode-Iyamah, K. (2025). Awake Minimally Invasive Surgery Transforaminal Lumbar Interbody Fusion Under Spinal Anesthesia: Screw Placement Accuracy and 1 Year Follow-Up. World Neuro, 194, 123478. https://doi.org/10.1016/j.wneu.2024.11.061
8. Fan, W., & Guo, L.-X. (2019a). A comparison of the influence of three different lumbar interbody fusion approaches on stress in the pedicle screw fixation system: Finite element static and vibration analyses. International J Numer Methods Biomed Engin, 35(3), e3162. https://doi.org/10.1002/cnm.3162

9. Fan, W., Guo, L.-X., & Zhao, D. (2019). Stress analysis of the implants in transforaminal lumbar interbody fusion under static and vibration loadings: A comparison between pedicle screw fixation system with rigid and flexible rods. J Mater Science: Mater Medicine, 30(10), 118. https://doi.org/10.1007/s10856-019-6320-0
10. Jhong, G.-H., Chung, Y.-H., Li, C.-T., Chen, Y.-N., Chang, C.-W., & Chang, C.-H. (2022). Numerical Comparison of Restored Vertebral Body Height after Incomplete Burst Fracture of the Lumbar Spine. J Personal Medicine, 12(2), 253. https://doi.org/10.3390/jpm12020253
11. Jiang, Y., Shi, K., Zhou, L., He, M., Zhu, C., Wang, J., … Zhang, L. (2023). 3D-printed auxetic-structured intervertebral disc implant for potential treatment of lumbar herniated disc. Bioactive Materials, 20, 528–538. https://doi.org/10.1016/j.bioactmat.2022.06.002
12. Kang, J., Dong, E., Li, X., Guo, Z., Shi, L., Li, D., & Wang, L. (2021). Topological design and biomechanical evaluation for 3D printed multi-segment artificial vertebral implants. Mater Science and Engin: C, 127, 112250. https://doi.org/10.1016/j.msec.2021.112250
13. Khalaf, K., & Nikkhoo, M. (2022). Comparative biomechanical analyses of lower cervical spine post anterior fusion versus intervertebral disc arthroplasty: A geometrically patient-specific poroelastic finite element investigation. Journal of Orthopaedic Translation, 36, 33–43. https://doi.org/10.1016/j.jot.2022.05.008
14. Kumar, M., Meena, V. K., & Singh, S. (2022). Static and Fatigue Load Bearing Investigation on Porous Structure Titanium Additively Manufactured Anterior Cervical Cages. BioMed Research International, 2022(1), 6534749. https://doi.org/10.1155/2022/6534749
15. Kurtz, S. M. (2019). Chapter 15—Development and Clinical Performance of PEEK Intervertebral Cages. In S. M. Kurtz (Ed.), PEEK Biomaterials Handbook (Second Edition) (pp. 263–280). William Andrew Publishing. https://doi.org/10.1016/B978-0-12-812524-3.00015-6
16. Kurtz, S. M., & Devine, J. N. (2007). PEEK biomaterials in trauma, orthopedic, and spinal implants. Biomaterials, 28(32), 4845–4869. https://doi.org/10.1016/j.biomaterials.2007.07.013
17. Lin, C.-Y., Wirtz, T., LaMarca, F., & Hollister, S. J. (2007). Structural and mechanical evaluations of a topology optimized titanium interbody fusion cage fabricated by selective laser melting process. Journal of Biomedical Materials Research Part A, 83A(2), 272–279. https://doi.org/10.1002/jbm.a.31231
18. Maher, C., Underwood, M., & Buchbinder, R. (2017). Non-specific low back pain. The Lancet, 389(10070), 736–747. https://doi.org/10.1016/S0140-6736(16)30970-9
19. Martin, B. I., Mirza, S. K., Spina, N., Spiker, W. R., Lawrence, B., & Brodke, D. S. (2019). Trends in Lumbar Fusion Procedure Rates and Associated Hospital Costs for Degenerative Spinal Diseases in the United States, 2004 to 2015. Spine, 44(5), 369. https://doi.org/10.1097/BRS.0000000000002822
20. McGilvray, K. C., Easley, J., Seim, H. B., Regan, D., Berven, S. H., Hsu, W. K., … Puttlitz, C. M. (2018). Bony ingrowth potential of 3D-printed porous titanium alloy: A direct comparison of interbody cage materials in an in vivo ovine lumbar fusion model. Spine Journal, 18(7), 1250–1260. Scopus. https://doi.org/10.1016/j.spinee.2018.02.018
21. Noiset, O., Schneider, Y.-J., & Marchand-Brynaert, J. (1999). Fibronectin adsorption or/and covalent grafting on chemically modified PEEK film surfaces. Journal of Biomaterials Science, Polymer Edition, 10(6), 657–677. Scopus. https://doi.org/10.1163/156856299X00865
22. Oxland, T. R., & Lund, T. (2000). Biomechanics of stand-alone cages and cages in combination with posterior fixation: A literature review. European Spine Journal, 9(SUPPL.1), S095-S101. Scopus. https://doi.org/10.1007/pl00010028
23. Parisien, A., Wai, E. K., Elsayed, M. S. A., & Frei, H. (2022). Subsidence of Spinal Fusion Cages: A Systematic Review. International Journal of Spine Surgery, 16(6), 1103–1118. Scopus. https://doi.org/10.14444/8363
24. Phillips, F. M., Cunningham, B., Carandang, G., Ghanayem, A. J., Voronov, L., Havey, R. M., & Patwardhan, A. G. (2004). Effect of supplemental translaminar facet screw fixation on the stability of stand-alone anterior lumbar interbody fusion cages under physiologic compressive preloads. Spine, 29(16), 1731–1736. Scopus. https://doi.org/10.1097/01.BRS.0000134570.08901.30
25. Rao, P. J., Pelletier, M. H., Walsh, W. R., & Mobbs, R. J. (2014). Spine Interbody Implants: Material Selection and Modification, Functionalization and Bioactivation of Surfaces to Improve Osseointegration. Orthopaedic Surgery, 6(2), 81–89. https://doi.org/10.1111/os.12098
26. Schwitalla, A., & Müller, W.-D. (2013). PEEK dental implants: A review of the literature. The Journal of Oral Implantology, 39(6), 743–749. https://doi.org/10.1563/AAID-JOI-D-11-00002
27. Seaman, Scott, Kerezoudis, P., Bydon, M., Torner, J. C., & Hitchon, P. W. (2017). Titanium vs. polyetheretherketone (PEEK) interbody fusion: Meta-analysis and review of the literature. J Clinic Neuro, 44, 23–29. https://doi.org/10.1016/j.jocn.2017.06.062
28. Shen, H., Chen, Y., Liao, Z., & Liu, W. (2021). Biomechanical evaluation of anterior lumbar interbody fusion with various fixation options: Finite element analysis of static and vibration conditions. Clinic Biomech, 84, 105339. https://doi.org/10.1016/j.clinbiomech.2021.105339
29. Silva, L. C., Batalha, G. F., Miranda, F., & Coelho, R. S. (2023). Validation of lumbar fusion device TILIF (Ti-6Al-4 V) manufactured by EBM additive manufacturing through fem modeling high cycle fatigue tests. Materials Today: Proceedings. https://doi.org/10.1016/j.matpr.2023.05.050
30. Skolasky, R. L., Wegener, S. T., Maggard, A. M., & Riley, L. H. (2014). The impact of reduction of pain after lumbar spine surgery: The relationship between changes in pain and physical function and disability. Spine, 39(17), 1426–1432. Scopus. https://doi.org/10.1097/BRS.0000000000000428
31. Smit, T., Aage, N., Haschtmann, D., Ferguson, S. J., & Helgason, B. (2024). Anatomically and mechanically conforming patient-specific spinal fusion cages designed by full-scale topology optimization. J Mech Behavior Biomed Mater, 159, 106695. https://doi.org/10.1016/j.jmbbm.2024.106695
32. Tsai, P.-I., Hsu, C.-C., Chen, S.-Y., Wu, T.-H., & Huang, C.-C. (2016). Biomechanical investigation into the structural design of porous additive manufactured cages using numerical and experimental approaches. Comput Bio Med, 76, 14–23. https://doi.org/10.1016/j.compbiomed.2016.06.016
33. Tsantrizos, A., Andreou, A., Aebi, M., & Steffen, T. (2000). Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs. European Spine J, 9(1), 14–22. Scopus. https://doi.org/10.1007/s005860050003
34. Tseng, J.-W., Liu, C.-Y., Yen, Y.-K., Belkner, J., Bremicker, T., Liu, B. H., … Wang, A.-B. (2018). Screw extrusion-based additive manufacturing of PEEK. Mater Design, 140, 209–221. Scopus. https://doi.org/10.1016/j.matdes.2017.11.032
35. Umale, S., Yoganandan, N., Baisden, J. L., Choi, H., & Kurpad, S. N. (2022). A biomechanical investigation of lumbar interbody fusion techniques. J Mech Behavior Biomed Mater, 125, 104961. https://doi.org/10.1016/j.jmbbm.2021.104961
36. Wang, L., Kang, J., Shi, L., Fu, J., Li, D., Guo, Z., … Jiang, X. (2018). Investigation into factors affecting the mechanical behaviours of a patient-specific vertebral body replacement. Proceedings of the Institution of Mechanical Engineers, Part H: J Engineering Med, 232(4), 378–387. https://doi.org/10.1177/0954411918754926
37. Welsch, G., Boyer, R., & Collings, E. W. (1993). Materials Properties Handbook: Titanium Alloys. ASM International.
38. Wu, Y.-J., Wang, C.-Y., Feng, K.-C., Chien, R. R., Mana-ay, H., Kung, S.-Y., … Lai, P.-L. (2023a). Ti-6Al-4V intervertebral fusion cage with compatible stiffness, enhanced fatigue life, and osteogenic differentiation. J Alloys Compounds, 957, 170450. https://doi.org/10.1016/j.jallcom.2023.170450
39. Zhang, Z., Li, H., Fogel, G. R., Xiang, D., Liao, Z., & Liu, W. (2018). Finite element model predicts the biomechanical performance of transforaminal lumbar interbody fusion with various porous additive manufactured cages. Comput Biology Med, 95, 167–174. https://doi.org/10.1016/j.compbiomed.2018.02.016
40. Zhang, Zhenjun, Li, H., Fogel, G. R., Xiang, D., Liao, Z., & Liu, W. (2018). Finite element model predicts the biomechanical performance of transforaminal lumbar interbody fusion with various porous additive manufactured cages. Comput Biology Med, 95, 167–174. https://doi.org/10.1016/j.compbiomed.2018.02.016