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.

中文翻译：

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脊柱运动节段— II：生物理想性能的调整和优化

大多数市售的脊柱类似物都不打算用于生物力学测试，而少数适合与植入物和装置结合使用以允许在操作程序上进行实际操作的脊柱类似物非常昂贵，但这些都无法提供针对患者的类似物，可以在合理的时间和价格范围内访问。人造脊柱类似物还将避免围绕生物标本使用的伦理限制，以及因其固有的生物变异性而引起的并发症。在这里，我们试图改善我们最近提出的针对患者的运动段类似物的生物保真度和准确性。这些模型由丙烯腈丁二烯苯乙烯（ABS）在猪脊柱节段（T12-L5）的3D打印中根据microCT扫描数据制成，并在0.6 mm·min的轴向载荷下进行了测试^-1（应变率范围6×10 ^-4 s ^-1 –10×10 ^-4 s ^-1）。在本文中，我们一直致力于通过改善机械行为的两个最关键方面来改进这些模拟模型的生物保真度：用于椎间盘的材料和小关节的影响。变形之后使用数字图像相关性（DIC），因此，还探索并比较了不同的扫描分辨率和数据采集技术以确定其效果。我们发现选择合适的椎间盘模拟物（PT Flex 85）可以实现逼真的力/位移响应，并且小关节在整个运动节段的生物仿生行为中也起着关键作用。因此，我们总体上确认了通过快速且廉价的3D打印方法生产以下产品的可行性：