Lehman Ronald A, Kuklo Timothy R, Belmont Philip J, Andersen Romney C, Polly David W
Department of Orthopaedic Surgery and Rehabilitation, Walter Reed Army Medical Center, Washington, DC, USA.
Spine (Phila Pa 1976). 2002 Apr 15;27(8):806-11. doi: 10.1097/00007632-200204150-00006.
A biomechanical study of human cadaveric sacra using insertional torque and bone mineral density was conducted to determine the optimal sagittal trajectory of S1 pedicle screws.
To measure the maximal insertional torque of sacral promontory versus bicortical pedicle screw fixation.
Fixation of instrumentation to the sacrum is commonly accomplished using S1 pedicle screws, with previous studies reporting biomechanical advantages of bicortical over unicortical S1 screws. The biomechanical effect of bicortical screws (paralleling the endplate) versus screws directed into the apex of the sacral promontory is unknown.
For this study, 10 fresh frozen cadaver sacra were harvested and evaluated with dual-energy radiograph absorptiometry to assess bone mineral density. Matched 7.5-mm monoaxial stainless steel pedicle screws then were randomly assigned by side (left versus right) and placed bicortically or into the apex of the sacral promontory under direct visualization. Maximum insertional torque was recorded for each screw revolution with a digital torque wrench (TQJE1500, Snap-On Tools, Kenosha, WI).
Maximum bicortical S1 screw insertional torque averaged 5.22 +/- 0.83 inch-pounds, as compared with the maximum sacral promontory S1 screw insertional torque of 10.34 +/- 1.94 inch-pounds. This resulted in a 99% increase in maximum insertional torque (P = 0.005) using the "tricortical" technique, with the screw directed into the sacral promontory. Mean bone mineral density was 940 +/- 0.25 mg/cm2 (range, 507-1428 mg/cm2). The bone mineral density correlated with maximal insertional torque for the sacral promontory technique (r = 0.806; P = 0.005), but not for the bicortical technique (r = 0.48; P = 0.16).
The screws directed into the apex of the sacral promontory of the S1 pedicle resulted in an average 99% increase in peak insertional torque (P = 0.005), as compared with bicortical S1 pedicle screw fixation. Tricortical pedicle screw fixation correlates directly with bone mineral density.
进行了一项关于人类尸体骶骨的生物力学研究，采用植入扭矩和骨密度来确定S1椎弓根螺钉的最佳矢状轨迹。
测量骶岬与双皮质椎弓根螺钉固定的最大植入扭矩。
将器械固定于骶骨通常使用S1椎弓根螺钉，先前研究报告双皮质S1螺钉比单皮质S1螺钉具有生物力学优势。双皮质螺钉（平行于终板）与指向骶岬顶点的螺钉的生物力学效应尚不清楚。
在本研究中，收集10具新鲜冷冻的尸体骶骨，并用双能X线吸收法评估骨密度。然后将匹配的7.5毫米单轴不锈钢椎弓根螺钉按侧别（左侧与右侧）随机分配，并在直视下双皮质置入或置入骶岬顶点。使用数字扭矩扳手（TQJE1500，Snap-On Tools，基诺沙，威斯康星州）记录每颗螺钉旋转时的最大植入扭矩。
双皮质S1螺钉的最大植入扭矩平均为5.22±0.83英寸磅，而骶岬S1螺钉的最大植入扭矩为10.34±1.94英寸磅。采用“三皮质”技术将螺钉指向骶岬，最大植入扭矩增加了99%（P = 0.005）。平均骨密度为940±0.25毫克/平方厘米（范围为507 - 1428毫克/平方厘米）。骨密度与骶岬技术的最大植入扭矩相关（r = 0.806；P = 0.005），但与双皮质技术无关（r = 0.48；P = 0.16）。
与双皮质S1椎弓根螺钉固定相比，指向S1椎弓根骶岬顶点的螺钉峰值植入扭矩平均增加了99%（P = 0.005）。三皮质椎弓根螺钉固定与骨密度直接相关。
