Frankel Bruce M, D'Agostino Sabino, Wang Chiang
Department of Neurosurgery, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
J Neurosurg Spine. 2007 Jul;7(1):47-53. doi: 10.3171/SPI-07/07/047.
Instrumentation of the osteoporotic spine can be fraught with complications such as hardware failure. A cadaver study was performed to determine the biomechanical performance of polymethylmethacrylate (PMMA)-augmented pedicle screws.
Three osteoporotic human cadaveric specimens with a mean bone mineral density of 0.70 g/cm2 were used to evaluate the performance of a novel fenestrated bone tap in pedicle screw augmentation. On this device, tap threads serve a dual purpose in preventing backflow of cement toward neural elements while allowing for a custom form for subsequent screw placement. The tap was used to inject a mean volume of 3.7 ml PMMA/pedicle (range 2-8.0 ml PMMA/pedicle) followed by pedicle screw placement between L-5 and T-5, alternating between augmented and nonaugmented instrumentation. Axial pullout testing was then performed.
Pedicle screw pullout strength was increased in both primary and salvage procedures by 119% (p = 0.001) and 162% (p = 0.01), respectively, after PMMA augmentation. Additionally, the injected cement volumes were divided into two groups, a low-cement group (< or = 2.8 ml/pedicle) and a high-cement group (> or = 5.5 ml/pedicle). Interestingly, the pullout strength did not significantly change with increased cement usage between the two groups (p > 0.05 for all comparisons).
Polymethylmethacrylate-augmented pedicle screw fixation results in a significant increase in the axial pullout strength of augmented pedicle screws in both primary and revision procedures. This technique may be a valuable adjunct in cases in which bolstering of the screw-bone interface is necessary.
骨质疏松性脊柱的器械植入可能充满诸如内固定失败等并发症。进行了一项尸体研究以确定聚甲基丙烯酸甲酯（PMMA）增强椎弓根螺钉的生物力学性能。
使用三个平均骨密度为0.70 g/cm²的骨质疏松症人体尸体标本，评估一种新型开窗式骨钻在椎弓根螺钉增强中的性能。在该装置上，钻螺纹具有双重作用，可防止骨水泥向神经组织回流，同时为后续螺钉置入提供定制形状。使用该骨钻向每个椎弓根平均注入3.7 ml PMMA（范围为2 - 8.0 ml PMMA/椎弓根），然后在L - 5和T - 5之间交替进行增强和未增强器械置入的椎弓根螺钉置入。随后进行轴向拔出试验。
在PMMA增强后，初次手术和翻修手术中椎弓根螺钉的拔出强度分别增加了119%（p = 0.001）和162%（p = 0.01）。此外，将注入的骨水泥体积分为两组，低骨水泥组（≤2.8 ml/椎弓根）和高骨水泥组（≥5.5 ml/椎弓根）。有趣的是，两组之间随着骨水泥用量增加，拔出强度没有显著变化（所有比较p > 0.05）。
聚甲基丙烯酸甲酯增强椎弓根螺钉固定在初次手术和翻修手术中均能显著提高增强椎弓根螺钉的轴向拔出强度。在需要加强螺钉 - 骨界面时，该技术可能是一种有价值的辅助方法。
