Objective To evaluate the effects of fatigue loading on the pull out strength of medial and lateral unicortical and bicortical sacral screws Methods Eleven fresh specimens of human sacrum were used in this study Bone mineral density (BMD) at the vertebral body and the ala were determined by peripheral quantitative computed tomography Seven millimeter compact CD sacral screws were inserted into the sacrum anteriomedially,anteriolaterally, unicortically and bicortically,and the insertion torque for each screw was measured Cyclic loading from 40 N to 400 N was applied to each screw at a frequency of 2 Hz up to 20 000 cycles Pull out tests were conducted after completion of the fatigue tests Results The average bone density at the S 1 body was 0 38 g/ml, and 0 24 g/ml at the S 1 ala The insertion torque and average pull out force following cyclic loading were significantly higher in bicortical fixation than that in unicortical fixation However, the pull out strength and insertion torque of medially oriented fixation was always higher than lateral fixation, regardless of whether the insertion was unicortical or bicortical The pull out force of unicortical and bicortical medial screw fixations following cyclic loading showed significant linear correlations with both the insertional torque and the bone mineral density of the S 1 body Conclusion In a group of young population, screw orientation(anterolateral or anteromedial) is more important in determining pull out strength than screw depth(unicortical or bicortical) following fatigue loading, anteromedially directed screws being significantly stronger than laterally placed screws Bone mineral density of the S 1 body and insertion torque are good preoperative and intraoperative indicators of screw pull out strength目的 研究骶骨螺釘固定在承受周期性載荷后的拔出強度,評價前內、前外側和單、雙邊皮質螺釘固定的生物力學作用。方法 對11 具新鮮成人尸體的骶骨行定量CT(QCT)掃描以確定S1 椎體和骶骨翼的骨礦物質密度。CCD骶骨螺釘分別放置在骶骨的前內、前外側和單、雙邊皮質等四個位置上,測量螺釘固定時旋入的力矩。對螺釘施加40～400 N 的垂直周期性載荷,載荷頻率為2Hz,加載次數為20 000 次。然后行螺釘拔出試驗,獲得螺釘最大拔出力。結果 S1 椎體和骶骨翼的平均骨礦物質密度分別為0-38 g/ml 和0-24g/ml。雙邊皮質螺釘固定時的旋入力矩和最大拔出力均顯著大于單邊皮質螺釘。而無論是單邊或雙邊皮質固定, 內側螺釘固定的旋入力矩和最大拔出力都顯著高于外側螺釘。內側螺釘固定的最大拔出力與S1 椎體的骨礦物質密度和旋入力矩呈線性相關。結論對于年輕人群, 骶骨螺釘固定的方向對螺釘固定的最大拔出力的影響比螺釘插入深度的影響要大,前內側螺釘固定要明顯強于前外側螺釘固定。S1 椎體骨礦物質密度和螺釘旋入力矩可分別反映螺釘在術前和術中的固定強度
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机译：目的评估疲劳负荷对内侧和外侧单皮质和双皮质骨螺钉抗拉强度的影响。方法本研究使用11例新鲜的human骨标本，通过椎体和椎弓根的骨密度测定外周定量计算机断层扫描术将7毫米紧凑型CD骨螺钉分别前，前，单侧和双侧插入into骨，并测量每个螺钉的插入扭矩，以2的频率对每个螺钉施加40 N至400 N的循环载荷Hz高达20000次循环疲劳测试完成后进行拔出测试结果S 1体的平均骨密度为0 38 g / ml，S 1 ala的平均骨密度为0 24 g / ml插入扭矩和平均值在双皮质固定中，循环载荷后的拔出力明显高于在单皮质固定中。但是，无论插入是单皮质还是双皮质，内侧定向固定始终高于外侧固定。周期性载荷后，单皮质和双皮质内侧螺钉固定的拔出力显示出与S的插入扭矩和骨矿物质密度显着线性相关1体结论在一群年轻人中，疲劳载荷后，螺钉方向（前外侧或前内侧）在确定拔出强度方面比螺钉深度（单皮质或双皮质）更重要，前向固定螺钉明显强于侧向放置螺钉骨矿物质密度S 1身体的硬度和插入扭矩是术前和术中螺钉拔出强度的良好指标。目的研究骶骨螺钉固定在承受骨折后的拔出强度，评价前内，前外侧和单，胫骨螺钉固定的生物力学作用。方法对11具新鲜成人尸体的骶骨行定量CT（QCT）扫描S1椎体和骶骨翼的骨矿物质密度。CCD骶骨螺钉分别放置在骶骨的前内，前外侧和单，多次对螺钉施加40〜400 N的垂直位移变量，变形频率为2Hz，加载次数为20000次。然后行螺钉拔出试验，获得螺钉。最大结果S1椎体和骶骨翼的平均骨矿物质密度分别为0-38 g / ml和0-24g / ml。少量螺钉固定时的旋入扭曲和最大拔出力均显着大于单边皮革螺钉。而无论是单边或全长皮革固定，螺钉螺钉固定的旋入扭曲和最大拔出力都显着性高于侧面螺钉。螺钉固定的最大拔出力与S1椎体的骨矿物质密度。对于年轻群，骶骨螺钉固定的方向对螺钉固定的最大拔出力的影响比螺钉插入深度的影响要大，前螺钉固定要明显强于前侧面螺钉固定。 S1椎体骨矿物质密度和螺钉旋入初始化可分别反映螺钉在术前和术中的固定强度
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