对带横连杆的椎弓根钉固定胸腰段脊柱骨折(T11～L3)的稳定性评价

目的评价带横连杆椎弓根钉固定胸腰椎骨折后脊柱的稳定性。方法将新鲜小牛胸腰椎标本(T11～L3)用椎体楔行切除法在L1椎体上制作严重压缩性骨折模型,部分骨折标本作带或不带横连杆的椎弓根钉内固定。这样共有4种脊柱标本:(1)正常标本;(2)未固定骨折标本;(3)用带横连杆椎弓根钉固定的骨折标本;(4)用不带横连杆椎弓根钉固定的骨折标本。用三维激光扫描仪依次测量各脊柱标本在前屈-后伸、左-右侧屈和左-右旋转6个方向的运动范围,然后将其标准化为稳定指数以比较4种标本的差异。结果与未固定骨折标本相比,两种固定均能显著提高损伤脊柱在各个运动方向的稳定性。带横连杆椎弓根钉固定的骨折标本稳定性虽优于无横连杆固定,但无统计差异。结论椎弓根钉内固定,无论有无横连杆,均能有效提高损伤脊柱的稳定性,而横连杆似乎未能进一步增加稳定效果。

Assessment for the stability of fracture thoracic lumber spine(T11~L3) fixed with crossbar equipped pedicle screws

Objective To determine the stability of fracture thoracic lumber spine (T11~L3) fixed with crossbar equipped pedicle screws. MethodThe thoracic lumber spine segments (T11~L3) were obtained from calves. A wedge cut was performed on L1 vertebral body to produce a model resembling severe vertebral compressive fracture. Some of the fracture spine segments were fixed with pedicle screws with and without crossbar. Thus, 4 types of spine segments were available: (1) normal segments; (2) unfixed fracture; (3) fracture fixed with crossbar equipped pedicle screws and (4) fracture fixed with pedicle screws without crossbar. The segmental stability was determined by measuring the range of motion (ROM) at directions of flexion/extension, left/right axial rotation and left/right lateral bending using a three dimensional laser scanner. Each ROM was standardized into a stability potential index (SPI) for the comparison among 4 groups. ResultsCompared to unfixed fracture, both fixations significantly increase stability of injuried specimens at each motion direction. The stability of injured segment fix with crossbar equipped pedicle screws is higher than that fixed without crossbar, but the difference does not reach statistically significant. ConclusionsPedicle screw fixation can significantly increase the stability of fracture spine. However, crossbar may not play a further role in raising fixative stability.