Karakaşlı Ahmet, Ceçen Berivan, Erduran Mehmet, Taylan Orçun, Hapa Onur, Havıtcıoğlu Hasan
Department of Biomechanics, Dokuz Eylül University, Health Sciences Institute, 35210 Alsancak, İzmir, Turkey.
Eklem Hastalik Cerrahisi. 2014;25(1):42-6. doi: 10.5606/ehc.2014.09.
This study aims to examine the motion and stability of the adjacent segment following rigid fixation of the lumbar spine.
The study included 17 fresh-frozen lamb lumbar spines (including the sacrum to T12). Biomechanical testing was performed using an axial compression testing machine. Axial compression was applied to all the specimens using a loading speed of 5 mm min-1. A specifically designed fixture was used to generate torque ≤8400 Nmm. The fixture was used with each specimen to achieve flexion and extension, axial neutral compression, and right and left bending. All specimens were tested intact, and again after implantation using posterior pedicle screws and rod fixation. During testing intervertebral displacement at the adjacent level (L5-S1) was recorded continuously via extensometry.
Axial compression and superior-inferior displacement were lower in the adjacent segment (L5-S1) than anterior-posterior displacement following rigid fixation. Statistical analysis showed that there was a numerical difference and a significant change between the intact spine and the adjacent segment in the axial compression and extension positions (p<0.027). The intact spines demonstrated the maximum displacement and the difference in extension positions were significant (p<0.015).
Rigid fixation of the lumbar spine altered the range of motion at the adjacent segment level. As such, abnormal stress on the adjacent segment causes spinal instability, which may subsequently cause facet joint degeneration and low back pain.
本研究旨在探讨腰椎刚性固定后相邻节段的运动及稳定性。
本研究纳入17个新鲜冷冻的羊腰椎标本（包括骶骨至胸12）。使用轴向压缩试验机进行生物力学测试。以5毫米/分钟的加载速度对所有标本施加轴向压缩。使用专门设计的夹具产生≤8400牛毫米的扭矩。该夹具用于每个标本以实现屈伸、轴向中立位压缩以及左右弯曲。所有标本在完整状态下进行测试，并且在使用后路椎弓根螺钉和棒固定植入后再次测试。在测试过程中，通过引伸计连续记录相邻节段（腰5-骶1）的椎间位移。
刚性固定后，相邻节段（腰5-骶1）的轴向压缩和上下位移低于前后位移。统计分析表明，完整脊柱与相邻节段在轴向压缩和伸展位置存在数值差异及显著变化（p<0.027）。完整脊柱表现出最大位移，且伸展位置的差异具有显著性（p<0.015）。
腰椎的刚性固定改变了相邻节段水平的运动范围。因此，相邻节段的异常应力会导致脊柱不稳定，进而可能导致小关节退变和腰痛。
