Yi Seong, Rim Dae-Cheol, Park Seoung Woo, Murovic Judith A, Lim Jesse, Park Jon
Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
Department of Neurosurgery, Stanford University Medical Center, Stanford, California, USA.
World Neurosurg. 2015 Jun;83(6):976-81. doi: 10.1016/j.wneu.2015.01.056. Epub 2015 Mar 10.
In vertebrae with low bone mineral densities pull out strength is often poor, thus various substances have been used to fill screw holes before screw placement for corrective spine surgery. We performed biomechanical cadaveric studies to compare nonaugmented pedicle screws versus hydroxyapatite, calcium phosphate, or polymethylmethacrylate augmented pedicle screws for screw tightening torques and pull out strengths in spine procedures requiring bone screw insertion.
Seven human cadaveric T10-L1 spines with 28 vertebral bodies were examined by x-ray to exclude bony abnormalities. Dual-energy x-ray absorptiometry scans evaluated bone mineral densities. Twenty of 28 vertebrae underwent ipsilateral fluoroscopic placement of 6-mm holes augmented with hydroxyapatite, calcium phosphate, or polymethylmethacrylate, followed by transpedicular screw placements. Controls were pedicle screw placements in the contralateral hemivertebrae without augmentation. All groups were evaluated for axial pull out strength using a biomechanical loading frame.
Mean pedicle screw axial pull out strength compared with controls increased by 12.5% in hydroxyapatite augmented hemivertebrae (P = 0.600) and by 14.9% in calcium phosphate augmented hemivertebrae (P = 0.234), but the increase was not significant for either method. Pull out strength of polymethylmethacrylate versus hydroxyapatite augmented pedicle screws was 60.8% higher (P = 0.028).
Hydroxyapatite and calcium phosphate augmentation in osteoporotic vertebrae showed a trend toward increased pedicle screw pull out strength versus controls. Pedicle screw pull out force of polymethylmethacrylate in the insertion stage was higher than that of hydroxyapatite. However, hydroxyapatite is likely a better clinical alternative to polymethylmethacrylate, as hydroxyapatite augmentation, unlike polymethylmethacrylate augmentation, stimulates bone growth and can be revised.
在骨矿物质密度较低的椎骨中，拔出强度通常较差，因此在进行脊柱矫正手术放置螺钉之前，已使用各种物质填充螺钉孔。我们进行了生物力学尸体研究，以比较在需要插入骨螺钉的脊柱手术中，未增强的椎弓根螺钉与羟基磷灰石、磷酸钙或聚甲基丙烯酸甲酯增强的椎弓根螺钉在螺钉拧紧扭矩和拔出强度方面的差异。
通过X射线检查7具人类尸体的T10 - L1脊柱，共28个椎体，以排除骨骼异常。采用双能X射线吸收法扫描评估骨矿物质密度。在28个椎体中的20个椎体同侧，通过荧光透视法在6毫米的孔中填充羟基磷灰石、磷酸钙或聚甲基丙烯酸甲酯，随后进行经椎弓根螺钉置入。对照组为对侧半椎体的椎弓根螺钉置入，未进行增强。使用生物力学加载框架对所有组进行轴向拔出强度评估。
与对照组相比，羟基磷灰石增强的半椎体中椎弓根螺钉的平均轴向拔出强度增加了12.5%（P = 0.600），磷酸钙增强的半椎体中增加了14.9%（P = 0.234），但两种方法的增加均无统计学意义。聚甲基丙烯酸甲酯增强的椎弓根螺钉与羟基磷灰石增强的椎弓根螺钉相比，拔出强度高60.8%（P = 0.028）。
在骨质疏松性椎体中，羟基磷灰石和磷酸钙增强与对照组相比，显示出椎弓根螺钉拔出强度增加的趋势。聚甲基丙烯酸甲酯在置入阶段的椎弓根螺钉拔出力高于羟基磷灰石。然而，羟基磷灰石可能是比聚甲基丙烯酸甲酯更好的临床替代物，因为与聚甲基丙烯酸甲酯增强不同，羟基磷灰石增强可刺激骨生长且可进行翻修。
