Freslon M, Mosnier T, Gayet L-E, Skalli W
Service d'Orthopédie-Traumatologie, CHU de la Milétrie, Hôpital Jean-Bernard, BP 577, 86021 Poitiers.
Rev Chir Orthop Reparatrice Appar Mot. 2007 May;93(3):213-21. doi: 10.1016/s0035-1040(07)90242-1.
Burst fractures generally occur due to trauma to the thoracolumbar spine. Surgery is indicated for unstable fractures. Posterior instrumentation with pedicular screws is generally proposed. In certain circumstances, hooks may be preferred due to excessive risk of insertion of the pedicular screw. The purpose of this study was to compare two posterior instrumentations, one using pedicular screws on either side of the fracture each protected by hoods and a second composed of the same pedicular screws inserted under the fracture hooks above.
Twelve spinal specimens from human cadavers composed of segments T10 to L2 were used. Range of flexion, extension, lateral inclination, and rotation were noted on T10 up to application of 7 Nm. Spinal segments were tested first intact, then in four configurations: 1) instrumented without lesion, 2) lesion simulating burst fracture of L1 without section of the interspinous ligament, 3) and with section of the interspinous ligament, and 4) with L1 corporectomy. Finally a test to rupture was performed by applying a flexion moment up to fracture.
Mean flexion-extension of the instrumented spine was limited compared with the intact spine for both instrumentation configurations and irrespective of the lesion. The same behavior was observed for lateral inclination with less pronounced motion with the first instrumentation. For rotation, the range of motion increased clearly with the second instrumentation and this with the first lesion while with the first instrumentation, rotation amplitude remained below that of the intact spine. There was however an increase in the vertical displacement during flexion-extension for both instrumentations. For the rupture test, the mean flexion moment at rupture was 14.4 Nm (10.6-22 Nm) with no difference between the two instrumentations.
This mode simulating burst fractures of the spine appears to be reproducible and more realistic than corporectomy. Attention should be taken concerning the limits of this type of study since fractures can occur for forces as small as 10.6 Nm. Thus we observed that pedicle screw configurations and also fractures produced mean ranges of motion greater than intact segments irrespective of the type of lesion simulated. However, the net increase in motion was observed during rotation movements when hooks were used, even when they were placed only below the fracture. Putting pressure on the hooks does not prevent them from slipping along the lamina. But neither of these two configurations controls the fracture gap. A vertebral reinforcement might be necessary.
爆裂性骨折通常因胸腰椎创伤而发生。不稳定骨折需进行手术治疗。一般建议采用椎弓根螺钉进行后路内固定。在某些情况下，由于椎弓根螺钉置入风险过高，可能更倾向于使用钩。本研究的目的是比较两种后路内固定方法，一种是在骨折两侧各使用一枚由保护罩保护的椎弓根螺钉，另一种是在骨折上方的钩下方插入相同的椎弓根螺钉。
使用12个来自人类尸体的脊柱标本，由T10至L2节段组成。记录T10在施加7 Nm力之前的屈伸、侧倾和旋转范围。首先对脊柱节段进行完整测试，然后测试四种构型：1）无损伤情况下进行内固定；2）模拟L1爆裂性骨折且棘间韧带未切断；3）棘间韧带切断；4）L1椎体切除。最后通过施加屈曲力矩直至骨折进行断裂测试。
对于两种内固定构型且无论损伤情况如何，内固定脊柱的平均屈伸与完整脊柱相比均受限。对于侧倾，第一种内固定的运动不太明显，情况相同。对于旋转，第二种内固定的运动范围明显增加，在第一种损伤情况下是这样，而第一种内固定的旋转幅度仍低于完整脊柱。然而，两种内固定在屈伸过程中的垂直位移均增加。对于断裂测试，断裂时的平均屈曲力矩为14.4 Nm（10.6 - 22 Nm），两种内固定之间无差异。
这种模拟脊柱爆裂性骨折的模式似乎是可重复的且比椎体切除更具现实性。由于小至10.6 Nm的力就可能导致骨折，因此应注意此类研究的局限性。因此我们观察到，无论模拟何种损伤类型，椎弓根螺钉构型以及骨折都会使运动范围大于完整节段。然而，当使用钩时，即使仅将其置于骨折下方，在旋转运动过程中仍观察到运动净增加。对钩施加压力并不能防止其沿椎板滑动。但这两种构型都无法控制骨折间隙。可能需要进行椎体强化。
