Race Amos, Miller Mark A, Ayers David C, Mann Kenneth A
Musculoskeletal Science Research Center, Institute for Human Performance, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
J Biomech. 2003 Apr;36(4):489-96. doi: 10.1016/s0021-9290(02)00460-8.
This study aimed to improve understanding of the mechanical aspects of cemented implant loosening. After aggressive fatigue loading of stem/cement/femur constructs, micro-cracks and stem/bone micro-motions were quantified to answer three research questions: Are cracks preferentially associated with the stem/cement interface, the cement/bone interface or voids? Is cement damage dependent on axial position? Does cement damage correlate with micro-motion between the stem and the bone? Eight Charnley Cobra stems were implanted in cadaveric femora. Six stem/cement/femur constructs were subjected to "stair-climbing" loads for 300 kcycles at 2Hz. Loads were normalized by construct stiffness to avoid fracture. Two additional constructs were not loaded. Transverse sections were cut at 10mm intervals, stained with a fluorescent dye penetrant and examined using epi-fluorescence stereomicroscopy. Crack lengths and cement areas were recorded for 9 sections per specimen. Crack length-density was calculated by dividing summed crack length by cement mantle area. To isolate the effect of loading, length-density data were offset by the baseline length-density measured in the non-loaded specimens. Significantly more cracks were associated with the interdigitated area (35.1%+/-11.6%) and the cement/bone interface (31.0%+/-6.2%) than with the stem/cement interface (11.0%+/-5.2%) or voids (6.1%+/-4.8%) (p<0.05). Load-induced micro-crack length-density was significantly dependent on axial position, increasing proximally (p<0.001). Micro-motions were small, all stems rotated internally. Cement damage did not correlate with micro-motion.
本研究旨在增进对骨水泥型植入物松动力学方面的理解。在对柄/骨水泥/股骨结构进行剧烈疲劳加载后，对微裂纹和柄/骨微动进行量化，以回答三个研究问题：裂纹是否优先与柄/骨水泥界面、骨水泥/骨界面或孔隙相关？骨水泥损伤是否取决于轴向位置？骨水泥损伤与柄和骨之间的微动是否相关？将八个Charnley Cobra柄植入尸体股骨中。六个柄/骨水泥/股骨结构在2Hz下承受“爬楼梯”载荷300千次循环。通过结构刚度对载荷进行归一化以避免骨折。另外两个结构未加载。每隔10mm切取横向切片，用荧光染料渗透剂染色，并使用落射荧光立体显微镜检查。记录每个标本9个切片的裂纹长度和骨水泥面积。通过将总裂纹长度除以骨水泥套面积来计算裂纹长度密度。为了分离加载的影响，长度密度数据通过在未加载标本中测量的基线长度密度进行偏移。与柄/骨水泥界面（11.0%±5.2%）或孔隙（6.1%±4.8%）相比，与指状交叉区域（35.1%±11.6%）和骨水泥/骨界面（31.0%±6.2%）相关的裂纹明显更多（p<0.05）。载荷诱导的微裂纹长度密度显著取决于轴向位置，在近端增加（p<0.001）。微动很小，所有柄均向内旋转。骨水泥损伤与微动无关。
