Zehr Jackie D, Quadrilatero Joe, Callaghan Jack P
Human Performance Lab, University of Calgary, Calgary, AB, Canada.
Department of Kinesiology & Health Sciences, University of Waterloo, Waterloo, ON, Canada.
J Mech Behav Biomed Mater. 2024 Feb;150:106334. doi: 10.1016/j.jmbbm.2023.106334. Epub 2023 Dec 29.
This study characterized the regional indentation mechanics and native collagen content in cartilaginous endplates (CEPs) from the porcine cervical spine, young human lumbar spine, and aged human lumbar spine. Seventeen endplates were included in this study: six porcine cervical, nine young human lumbar, and two aged human lumbar. Width and depth measurements were obtained using a digital caliper and used to size-normalize and identify the central, anterior, posterior, and lateral regions. Regional microindentation tests were performed using a serial robot, where surface locations were loaded/unloaded at 0.1 mm/s and held at a constant 10 N force for 30 s. Loading stiffness and creep displacement were obtained from force-displacement data. Immunofluorescence staining for type I and type II collagen was subsequently performed on sagittal sections of all endplate regions. 255 images were obtained from which fluorescence intensity, sub-surface void area, and cartilage thickness were measured. CEPs from the young human lumbar spine were, on average, 27% more compliant, 0.891 mm thicker, had a lower fluorescence intensity for native collagen proteins within the cartilage (-58%) and subchondral bone (-24%), and had a sub-surface void area that was 19.7 times greater than porcine cervical CEPs. Compared to aged human lumbar CEPs, young human lumbar CEPs were 57% stiffer, 0.568 mm thicker, had a higher fluorescence intensity for native collagen proteins within the cartilage (+30%) and subchondral bone (+46%), and had a sub-surface void area that was 10.6 times smaller. Although not a perfect mechanical and structural surrogate, porcine cervical CEPs provided initial conditions that may be more representative of the young and healthy human lumbar spine compared to aged human cadaveric specimens. The indentation properties presented may have further applications to finite element models of the human lumbar spine.
本研究对来自猪颈椎、年轻人类腰椎和老年人类腰椎的软骨终板 (CEP) 的区域性压痕力学和天然胶原蛋白含量进行了表征。本研究共纳入 17 个终板，包括 6 个猪颈椎、9 个年轻人类腰椎和 2 个老年人类腰椎。使用数字卡尺获得宽度和深度测量值，并用于尺寸归一化和识别中央、前、后和侧区。使用串联机器人进行区域微压痕测试，其中表面位置以 0.1mm/s 的速度加载/卸载，并以恒定的 10N 力保持 30s。从力-位移数据中获得加载刚度和蠕变位移。随后对所有终板区域的矢状切片进行 I 型和 II 型胶原蛋白的免疫荧光染色。从这些切片中获得了 255 张图像，从中测量了荧光强度、亚表面空隙面积和软骨厚度。年轻人类腰椎的 CEP 平均柔顺性提高了 27%，厚度增加了 0.891mm，软骨和软骨下骨中天然胶原蛋白的荧光强度降低了（-58%和-24%），亚表面空隙面积增加了 19.7 倍与猪颈椎 CEP 相比。与老年人类腰椎的 CEP 相比，年轻人类腰椎的 CEP 硬度提高了 57%，厚度增加了 0.568mm，软骨和软骨下骨中天然胶原蛋白的荧光强度提高了（+30%和+46%），亚表面空隙面积减少了 10.6 倍。尽管不是完美的机械和结构替代物，但猪颈椎 CEP 提供的初始条件可能比老年人类尸体标本更能代表年轻和健康的人类腰椎。提出的压痕特性可能对人类腰椎的有限元模型有进一步的应用。
