White Klane K, Oka Richard, Mahar Andrew T, Lowry Alexandra, Garfin Steven R
Department of Orthopaedic Surgery, University of California, San Diego, CA, USA.
Spine (Phila Pa 1976). 2006 May 20;31(12):E355-8. doi: 10.1097/01.brs.0000219394.48091.d6.
In vitro biomechanical comparison of two methods of pedicle screw placement in cadaveric thoracic spine vertebrae.
Compare the biomechanical integrity of extrapedicular and transpedicular screw fixation under axial and sagittal pullout loads.
Extrapedicular screw placement has been advocated as a safe and effective alternative to the transpedicular screw in thoracic vertebrae. Rigorous biomechanical comparison of these two techniques is presently lacking in the literature.
Thirty-seven vertebral bodies were dissected from six cadaveric thoracic spines. Each body had two polyaxial 5.0-mm screws placed: one transpedicular and one extrapedicular. The 62 screws were randomly designated for one of two loading methods: axial or sagittal. Failure load (N), taken as maximum force on the load-deformation curve, and stiffness (N/mm), calculated between 50 N and 400 N, were measured. RESULTS.: Transpedicular screws were statistically stronger in both testing methods (P = 0.008). Load direction, whether axial or sagittal, had no bearing on pullout strength (P = 0.6).
These data indicate that transpedicular screws are biomechanically superior to extrapedicular screws. This difference is small, however, and we think that extrapedicular screws offer an excellent alternative when anatomy dictates their use with other screws in segmental spinal constructs.
对尸体胸椎椎弓根螺钉置入的两种方法进行体外生物力学比较。
比较椎弓根外和经椎弓根螺钉固定在轴向和矢状面拔出负荷下的生物力学完整性。
椎弓根外螺钉置入已被提倡作为胸椎经椎弓根螺钉的一种安全有效的替代方法。目前文献中缺乏对这两种技术的严格生物力学比较。
从6具尸体胸椎中解剖出37个椎体。每个椎体置入两枚多轴5.0毫米螺钉：一枚经椎弓根，一枚椎弓根外。62枚螺钉被随机指定用于两种加载方法之一：轴向或矢状面。测量失效负荷（N），即负荷-变形曲线上的最大力，以及在50 N至400 N之间计算得出的刚度（N/mm）。结果：在两种测试方法中，经椎弓根螺钉在统计学上都更强（P = 0.008）。负荷方向，无论是轴向还是矢状面，对拔出强度均无影响（P = 0.6）。
这些数据表明经椎弓根螺钉在生物力学上优于椎弓根外螺钉。然而，这种差异较小，并且我们认为当解剖结构决定在节段性脊柱结构中与其他螺钉一起使用椎弓根外螺钉时，它是一种很好的替代选择。
