Goel V K, Winterbottom J M, Weinstein J N
Department of Biomedical Engineering, University of Iowa, Iowa City 52242.
J Biomech. 1994 Nov;27(11):1383-8. doi: 10.1016/0021-9290(94)90048-5.
Spinal devices/instrumentation are used to augment the stability of a decompressed spinal segment during surgery. Like any other mechanical component, the device can fail. A standard in vitro test protocol, was developed to determine load vs number of cycles to failure curve for a pedicle screw-plate/rod type spinal device. The protocol based on the use of an 'artificial spine' model, is clinically relevant. The protocol was used to characterize the load-carrying capacities and failure modes of a specific pedicle screw-rod type fixation device to demonstrate its appropriateness. The devices (Kaneda) were tested in the quasi-static as well as fatigue bending modes. In the bending fatigue mode, the devices failed at loads significantly smaller than the corresponding quasi-static failure load magnitude (806 N). The device exhibited an endurance limit in the fatigue bending mode. The device is not likely to exhibit failure if subjected to cyclic loads which cause less than 380 N axial compression (and an accompanying bending moment relative to the device of less than 13.57 Nm). The failures observed in specimens subjected to the fatigue tests ranged from complete to partial breakage of the paraspinal rods as opposed to failure due to permanent deformation (yielding) of the rods in the quasi-static bending test specimens. The protocol developed can be used for any other screw-plate/rod type spinal instrumentation. The use of a standard protocol by researchers would enable a comparison of various devices currently available in the market. Such comparative data would be useful for the scientific community, and agencies such as the FDA and ASTM.(ABSTRACT TRUNCATED AT 250 WORDS)
脊柱器械/植入物用于在手术期间增强减压脊柱节段的稳定性。与任何其他机械部件一样，该器械可能会失效。已制定了一项标准体外测试方案，以确定椎弓根螺钉-钢板/杆型脊柱器械的载荷与失效循环次数曲线。基于“人工脊柱”模型的该方案具有临床相关性。该方案用于表征特定椎弓根螺钉-杆型固定器械的承载能力和失效模式，以证明其适用性。对这些器械（Kaneda）进行了准静态以及疲劳弯曲模式测试。在弯曲疲劳模式下，器械在远小于相应准静态失效载荷大小（806 N）的载荷下失效。该器械在疲劳弯曲模式下表现出疲劳极限。如果承受小于380 N轴向压缩（以及相对于器械小于13.57 Nm的伴随弯矩）的循环载荷，该器械不太可能出现失效。在疲劳测试的标本中观察到的失效范围从椎旁杆的完全断裂到部分断裂，这与准静态弯曲测试标本中杆因永久变形（屈服）而失效不同。所制定的方案可用于任何其他螺钉-钢板/杆型脊柱植入器械。研究人员使用标准方案将能够比较市场上目前可用的各种器械。此类比较数据将对科学界以及美国食品药品监督管理局和美国材料与试验协会等机构有用。（摘要截断于250字）
