Abstract
Most commercially available spine analogues are not intended for biomechanical testing, and the few that are suitable for using in conjunction with implants and devices to allow a hands-on practice on operative procedures are very expensive and still none of these offers patient-specific analogues that can be accessed within reasonable time and price range. Man-made spine analogues would also avoid the ethical restrictions surrounding the use of biological specimens and complications arising from their inherent biological variability. Here we sought to improve the biofidelity and accuracy of a patient-specific motion segment analogue that we presented recently. These models were made by acrylonitrile butadiene styrene (ABS) in 3D printing of porcine spine segments (T12−L5) from microCT scan data, and were tested in axial loading at 0.6 mm·min−1 (strain rate range 6×10−4 s−1–10×10−4 s−1). In this paper we have sought to improve the biofidelity of these analogue models by concentrating in improving the two most critical aspects of the mechanical behaviour: the material used for the intervertebral disc and the influence of the facet joints. The deformations were followed by use of Digital Image Correlation (DIC) and consequently different scanning resolutions and data acquisition techniques were also explored and compared to determine their effect. We found that the selection of an appropriate intervertebral disc simulant (PT Flex 85) achieved a realistic force/displacement response and also that the facet joints play a key role in achieving a biofidelic behaviour for the entire motion segment. We have therefore overall confirmed the feasibility of producing, by rapid and inexpensive 3D-printing methods, high-quality patient-specific spine analogue models suitable for biomechanical testing and practice.
Similar content being viewed by others
References
Friss E A, Pence D C, Graber C D, Montoya J A. Mechanical analogue model of the human lumbar spine: Development and evaluation. In: Melkerson M N, Griffith S L, Kirkpatric J S, eds., Spinal Implants: Are We Evaluating Them Appropriately?, ASTM International, West Conshohocken, PA, USA, 2003, 236.
Wilke H J, Krischack S, Claes L E. Formalin fixation strongly influences biomechanical properties of the spine. Journal of Biomechanics, 1996, 29, 1629–1631.
Holsgrove T P, Gill H S, Miles A W, Gheduzzi S. The dynamic, six-axis stiffness matrix testing of porcine spinal specimens. The Spine Journal, 2015, 15, 176–184.
Costi J, Hearn T, Fazzalari N. The effect of hydration on the stiffness of intervertebral discs in an ovine model. Clinical Biomechanics, 2002, 17, 446–455.
Smeathers J E, Joanes D N. Dynamic compressive properties of human lumbar intervertebral joints: A comparison between fresh and thawed specimens. Journal of Biomechanics, 1988, 21, 425–433.
Sawbones. Biomechanical Spine Product Research, [2018-02-05], http://www.sawbones.com/UserFiles/Documents/Product/BioSpine_info.pdf.
Wang T, Ball J R, Pelletier M H, Walsh W R. Initial experience with synthetic spinal motion segments: Biomechanical assessment of high cycle and implant performance. ORS Annual Meeting, New Orleans, LA, USA, 2014.
Domann J P. Development and Validation of an Analogue Lumbar Spine Model and its Integral Components, University of Kansas, Lawrence, KA, USA, 2011.
ASTM. Standard Test Methods for Spinal Implant Constructs in a Vertebrectomy Model, ASTM International, West Conshohocken, PA, USA, 2015.
Camisa W, Leasure J, Buckley J. Biomechanical validation of a synthetic lumbar spine. The Spine Journal, 2014, 14, 129–130.
Campbell J, Imsdahl S, Ching R. Evaluation of a Synthetic L2-L5 Spine Model for Biomechanical Testing, Orthopaedic Research Society, New Orleans, USA, 2010.
Franceskides C. Subject Specific Functional Model of Hard and Soft Tissues: Skull and Spine, PhD Thesis, Cranfield University, UK, 2018.
Franceskides C, Arnold E, Horsfall I, Tozzi G, Gibson M.C, Zioupos P. Spinal motion segments — I: Concept for a subject-specific analogue model. Journal of Bionic Engineering, 2020. (In press)
Inglis S. 3D Printing in the NHS and healthcare sciences. IPEM Scope, 2016, 25, 10–13.
Cantrell J, Rohde S, Damiani D, Gurnani R, Di Sandro L, Anton J, Young A, Jerez A, Steinbach D, Kroese C, Ifju P. Experimental characterization of the mechanical properties of 3D-printed ABS and polycarbonate parts. Conference Proceedings of the Society for Experimental Mechanics Series, 2017, 3, 89–105.
Zou R, Xia Y, Liu S Y, Hu P, Hou W B, Hu Q Y, Shan C L. Isotropic and anisotropic elasticity and yielding of 3D printed material. Composites Part B: Engineering, 2016, 99, 506–513.
Jaumard N V, Welch W C, Winkelstein B A. Spinal facet joint biomechanics and mechanotransduction in normal, injury and degenerative conditions. Journal of Biomechanical Engineering, 2011, 133, 071010.
Pal G P, Routal R V. Transmission of weight through the lower thoracic and lumbar regions of the vertebral column in man. Journal of Anatomy, 1987, 152, 93–105.
Shore A F, Shore C P. Apparatus for Measuring the Hardness of Materials, US Patent, US1770045 (A)-1930-07-08, 1930.
Lott B D, Reece F N, Drott J H. Effect of preconditioning on bone breaking strength. Poultry Science, 1980, 59, 724–725.
Roberts S J, Smith C I, Millard A, Collins M J. The taphonomy of cooked bone: Characterising boiling and its physicochemical effects. Archaeometry, 2002, 44, 485–494.
Newell N, Little J P, Christou A, Adams M A, Adam C J, Masouros S D. Biomechanics of the human intervertebral disc: A review of testing techniques and results. Journal of the Mechanical Behavior of Biomedical Materials, 2017, 69, 420–434.
Palanca M, Tozzi G, Cristofolini L. The use of digital image correlation in the biomechanical area: A review. International Biomechanics, 2016, 3, 1–21.
Palanca M, Marco M, Ruspi M L, Cristofolini L. Full-field strain distribution in multi-vertebra spine segments: An in vitro application of digital image correlation. Medical Engineering & Physics, 2018, 52, 76–83.
Vassolera J M, Fancelloa E A. Error analysis of the digital image correlation method. Asociación Argentina de Mecánica Computacional, 2012, 29, 6149–6161.
Pan B, Lu Z, Xie H. Mean intensity gradient: An effective global parameter for quality assessment of the speckle patterns used in digital image correlation. Optics and Lasers in Engineering, 2010, 48, 469–477.
Lecompte D, Smits A, Bossuyt S, Sol H, Vantomme J, Van Hemelrijck D, Habraken A M. Quality assessment of speckle patterns for digital image correlation. Optics and Lasers in Engineering, 2006, 44, 1132–1145.
Sutton MA, Orteu J J, Schreier H. Image Correlation for Shape, Motion and Deformation Measurements, Springer, New York, USA, 2009.
Sutradhar A, Park J, Carrau D, Miller M J. Experimental validation of 3D printed patient-specific implants using digital image correlation and finite element analysis. Computers in Biology and Medcine, 2014, 52, 8–17.
Amiot F, Bornert M, Doumalin P, Dupré J-C, Fazzini M, Orteu J-J, Poilâne C, Robert L, Rotinat R, Toussaint E, Wattrisse B, Wienin J S. Assessment of digital image correlation measurement accuracy in the ultimate error regime: Main results of a collaborative benchmark. Strain, 2013, 49, 483–496.
Siebert T, Becker T, Spiltthof K. Error estimations in digital image correlation technique. Applied Mechanics and Materials, 2007, 7, 265–270.
Zioupos P, Smith C, Yuehuei A. Factors affecting mechanical properties of bone. In: Yuehuei A, Robert D A, eds., Mechanical Testing of Bone and the Bone-Implant Interface, CRC Press, Boca Raton, FL, USA, 1999, 65–85.
Smit T H. The use of a quadruped as an in vivo model for the study of the spine — biomechanical considerations. European Spine Journal, 2002, 11, 137–144.
Busscher I, van der Veen A J, van Dieën J H. In vitro biomechanical characteristics of the spine: A comparison between human and porcine spinal segments. Spine, 2010, 35, 35–42.
Dath R, Ebinesan A D, Porter K M, Miles A W. Anatomical measurements of porcine lumbar vertebrae. Clinical Biomechanics, 2007, 22, 607–613.
Acknowledgment
We acknowledge the work, skill and expertise of Karl Norris and the mechanical workshop of Cranfield University, Shrivenham, and Jolyon Cleaves of Vision Research for providing the high-speed cameras. Ethical approval was granted by the Cranfield University Research and Ethics committee (CURES). This paper is dedicated to our friend and colleague Dr Mike Gibson, whose untimely death is a great loss to us all.
Author information
Authors and Affiliations
Corresponding author
Additional information
Data accessibility
Data for this manuscript is available through the Cranfield University CORD data depository and preservation system (https://cranfield.figshare.com).
Rights and permissions
About this article
Cite this article
Franceskides, C., Arnold, E., Horsfall, I. et al. Spinal Motion Segments — II: Tuning and Optimisation for Biofidelic Performance. J Bionic Eng 17, 757–766 (2020). https://doi.org/10.1007/s42235-020-0061-0
Published:
Issue Date:
DOI: https://doi.org/10.1007/s42235-020-0061-0