Jacob Arun T, Ingalhalikar Aditya V, Morgan John H, Channon Scott, Lim Tae-Hong, Torner James C, Hitchon Patrick W
Department of Neurosurgery, University of Iowa, Iowa, USA.
J Neurosurg Spine. 2008 Jan;8(1):52-7. doi: 10.3171/SPI-08/01/052.
The pedicle screw (PS) is the cornerstone of spinal instrumentation, and its failure often entails additional surgery. Screw pullout is one of the most common reasons for screw failure, particularly in the elderly population. In this study the authors undertook a biomechanical comparison of the maximum pullout force (MPF) required for single- and dual-lead PSs in cadaver vertebrae.
Radiographs of 40 cadaveric vertebrae (T11-L5) were obtained, and bone mineral density (BMD) was measured in the lateral plane using dual-x-ray absorptiometry with a bone densitometer. One screw of each design was implanted for side-by-side comparison. Vertebrae were potted and mounted on an MTS test frame for accurate measurement of MPF. A total of 80 PSs were tested, 40 each of single- and dual-lead design types.
The average MPF for dual-lead screws (533.89 +/- 285.7 N) was comparable to that of single-lead screws (524.90 +/- 311.6 N) (p = 0.3733). The BMD had a significant correlation with MPF for both dual-lead (r = 0.56413, p < 0.0001) and single-lead screws (r = 0.56327, p < 0.0001).
Barring the effect of BMD, this in vitro biomechanical test showed no significant difference in MPF between single- and dual-lead PSs. Dual-lead PSs can be used to achieve a faster insertion time, without compromising pullout force.
椎弓根螺钉（PS）是脊柱内固定的基石，其失效往往需要进行额外的手术。螺钉拔出是螺钉失效的最常见原因之一，在老年人群中尤为如此。在本研究中，作者对尸体椎骨中单导和双导PS所需的最大拔出力（MPF）进行了生物力学比较。
获取40具尸体椎骨（T11-L5）的X线片，使用双能X线骨密度仪在侧位平面测量骨密度（BMD）。每种设计的一枚螺钉并排植入以进行比较。将椎骨装盆并安装在MTS测试框架上以准确测量MPF。共测试80枚PS，单导和双导设计类型各40枚。
双导螺钉的平均MPF（533.89±285.7 N）与单导螺钉（524.90±311.6 N）相当（p = 0.3733）。BMD与双导螺钉（r = 0.56413，p < 0.0001）和单导螺钉（r = 0.56327，p < 0.0001）的MPF均有显著相关性。
排除BMD的影响，这项体外生物力学测试表明单导和双导PS在MPF方面无显著差异。双导PS可用于实现更快的插入时间，而不影响拔出力。
