Department of Orthopaedic Surgery, Stanford University Medical Center.
Spine (Phila Pa 1976). 2010 May 1;35(10):1039-43. doi: 10.1097/BRS.0b013e3181d85ec8.
Biomechanical analysis of derotational load-to-failure of pedicle screw (PS) instrumentation in cadaveric thoracic spinal segments.
To investigate the derotational torque that can be applied to the thoracic spine through different linked constructs and evaluate the modes of failure.
Thoracic derotation with PSs has been shown to provide better 3 plane correction than other methods but the effects of linked PS constructs has not been studied.
Four groups of thoracic segments with different PS constructs were loaded to failure with a rotational torque applied to the construct to simulate the left to right derotational force applied to a typical idiopathic dextrorotary thoracic scoliosis curve. Single screw T4 segments instrumented on the medial (group 1M) and lateral (group 1L) sides, bilaterally-linked T5 segments (group 2), unilaterally-linked T6-T9 segments on the medial (group 3M) and lateral (group 3L) sides, and quadrangularly-linked T6-T9 segments (group 4) were loaded with MTS machine in a simulated thoracic derotation model.
Single T4 PSs on the medial and lateral sides failed at 4.0 +/- 1.4 Nm (group 1M) and 6.1 +/- 2.5 Nm (group 1L), respectively. Bilaterally-linked T5 screws failed at 11.9 +/- 3.1 Nm (group 2). Unilaterally linked T6-T9 PS constructs on the medial and lateral sides failed at 21.2 +/- 7.5 Nm (group 3M) and 17.9 +/- 11.1 Nm (group 3L), respectively. Quadrangularly-linked PSs failed at 42.5 +/- 14.5 Nm (group 4). CONCLUSION.: A near linear increase in relative torque applied before failure was found with each additional PS linked. Linked constructs allow for significantly greater torque with less risk of PS breach of the spinal canal.
尸体胸段椎弓根螺钉（PS）器械抗旋转失效的生物力学分析。
通过不同的连接结构研究可施加于胸段的抗旋转扭矩，并评估失效模式。
与其他方法相比，PS 胸段旋转已被证明可提供更好的三平面矫正，但尚未研究连接 PS 结构的影响。
将不同 PS 结构的四组胸段进行加载直至失效，通过对结构施加旋转扭矩模拟典型特发性右旋胸脊柱侧凸曲线的左右旋转力。单侧 T6-T9 节段连接的双侧 T5 节段（组 2）、单侧 T6-T9 节段（组 3M）和单侧 T6-T9 节段（组 3L），连接的 T4 节段在 medial（组 1M）和 lateral（组 1L）侧分别为 4.0+/-1.4 Nm 和 6.1+/-2.5 Nm。双侧 T5 螺钉的失败扭矩为 11.9+/-3.1 Nm（组 2）。单侧 T6-T9 PS 结构在 medial（组 3M）和 lateral（组 3L）侧的失败扭矩分别为 21.2+/-7.5 Nm 和 17.9+/-11.1 Nm。四边形 PS 的失败扭矩为 42.5+/-14.5 Nm（组 4）。结论：发现随着连接 PS 数量的增加，失效前施加的相对扭矩呈近线性增加。连接结构允许施加更大的扭矩，同时降低 PS 穿透椎管的风险。
