Daftari T K, Horton W C, Hutton W C
Department of Orthopaedics, Emory University, Decatur, Georgia.
J Spinal Disord. 1994 Apr;7(2):139-45. doi: 10.1097/00002517-199407020-00007.
The bone-screw interface is critical in the use of spinal instrumentation. The purpose of these experiments described here was twofold. First, to determine whether a correlation existed between torque generated during screw insertion and the pullout strength. Second, to determine how differing surgical methods of screw hole preparation influenced torque of insertion and screw pullout strength. A series of experiments were carried out in which screws were inserted into synthetic bone (experiment 1) and into calf vertebrae (experiment 2). The method of screw hole preparation (i.e., diameter of entrance hole and pilot hole) was varied while the resulting torque of insertion and the pullout strength of the screw was measured in each case. A torque screwdriver was used to measure the torque of insertion of the screws. Screw pullout strength was measured using a materials testing machine. Two important results emerged from these experiments. First, a higher torque of insertion correlated with a higher screw pullout force. This correlation may be useful intraoperatively in evaluating fixation. Second, torque of insertion and pullout force were more influenced by cortex over-drill diameter than pilot hole diameter. These experiments show the importance of the dorsal cortex in pedicle screw fixation.
骨螺钉界面在脊柱内固定器械的使用中至关重要。此处所述的这些实验有两个目的。其一，确定螺钉植入过程中产生的扭矩与拔出强度之间是否存在相关性。其二，确定不同的螺钉孔制备手术方法如何影响植入扭矩和螺钉拔出强度。进行了一系列实验，将螺钉分别植入合成骨（实验1）和小牛椎骨（实验2）。在每种情况下，改变螺钉孔制备方法（即入口孔和导向孔的直径），同时测量由此产生的螺钉植入扭矩和拔出强度。使用扭矩螺丝刀测量螺钉的植入扭矩。使用材料试验机测量螺钉拔出强度。这些实验得出了两个重要结果。其一，较高的植入扭矩与较高的螺钉拔出力相关。这种相关性在术中评估固定时可能有用。其二，植入扭矩和拔出力受皮质过度钻孔直径的影响大于导向孔直径。这些实验表明了背侧皮质在椎弓根螺钉固定中的重要性。
