Chutkan Norman B, Zhou Haitao, Akins John P, Wenger Karl H
Department of Orthopaedic Surgery, Medical College of Georgia, Augusta, GA, USA.
Spine (Phila Pa 1976). 2008 Oct 15;33(22):E828-35. doi: 10.1097/BRS.0b013e318183bb6d.
Biomechanical assessment using calf lumbar motion segments.
To determine whether facetectomy affects the primary stability of posterior lumbar interbody fusion.
To improve visualization and access to the disc space, the facet joints frequently are removed. Previous biomechanical studies have indicated a fundamental role for the facet joints in maintaining spinal segment stability.
Single motion segments from calf lumbar spines were tested for pure-moment flexibility in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). After testing intact, an interbody cage and pedicle screw system were implanted. Next, a bilateral facetectomy was performed, and finally a crosslink was added. Flexibility testing was repeated at each stage of implantation. Data are reported for range of motion (ROM), neutral zone (NZ), and a new compliance parameter (COM), based on the slopes of the moment-angle curve in the neutral and elastic regions.
With posterior lumbar interbody fusion implantation, ROM in FE was reduced 82% +/- 4% (mean +/- standard deviation) and NZ 78% +/- 7% over intact (P < 0.015: Wilcoxon). Reduction in LB was slightly more, whereas reduction in AR was considerably less and did not achieve statistical significance for NZ. After facetectomy, ROM in FE increased 0.3 degrees (P < 0.05), on average, and NZ did not change. In LB neither changed significantly. In AR, ROM increased 0.6 degrees (P < 0.05), and NZ increased 0.2 degrees (P < 0.05). The addition of a crosslink changed ROM and NZ less than 0.1 degrees in FE and LB, whereas in AR it restored half of the stability lost due to facetectomy in ROM (P < 0.05), and had a similar trendwise effect on NZ. The new compliance measure, COM, was found to agree with the direction of change in ROM more consistently than did NZ.
Facetectomy causes a nominal increase in ROM and NZ in FE and LB, which are not affected by the addition of a crosslink. Although the effect of facetectomy is greater in AR-and crosslink has a measurable restoring effect-all differences are within a few tenths of a degree under this loading paradigm. Thus, the clinical utility of adding a crosslink may not be justified based on these small biomechanical changes. COM can serve as a complement to ROM and NZ, or even as a surrogate when its 2 components are reported together, as it shows strong agreement with ROM, effectively distinguishes between lax and elastic region behaviors, and provides a measure of flexibility independent of the load range.
使用小牛腰椎运动节段进行生物力学评估。
确定椎板切除术是否会影响腰椎后路椎间融合术的初始稳定性。
为了改善对椎间盘间隙的可视化和操作，通常会切除小关节。先前的生物力学研究表明，小关节在维持脊柱节段稳定性方面具有重要作用。
对小牛腰椎的单个运动节段进行屈伸（FE）、侧屈（LB）和轴向旋转（AR）的纯力矩柔韧性测试。在测试完整状态后，植入椎间融合器和椎弓根螺钉系统。接下来，进行双侧椎板切除术，最后添加横向连接装置。在植入的每个阶段重复柔韧性测试。报告基于中性区和弹性区力矩-角度曲线斜率的运动范围（ROM）、中性区（NZ）和一个新的顺应性参数（COM）的数据。
在进行腰椎后路椎间融合植入后，FE中的ROM比完整状态降低了82%±4%（平均值±标准差），NZ降低了78%±7%（P<0.015：Wilcoxon检验）。LB中的降低幅度稍大，而AR中的降低幅度小得多，且NZ未达到统计学显著性。椎板切除术后，FE中的ROM平均增加了0.3度（P<0.05），NZ没有变化。在LB中两者均无显著变化。在AR中，ROM增加了0.6度（P<0.05），NZ增加了0.2度（P<0.05）。添加横向连接装置后，FE和LB中的ROM和NZ变化小于0.1度，而在AR中，它恢复了因椎板切除术在ROM中损失稳定性的一半（P<0.05），并且对NZ有类似的趋势性影响。发现新的顺应性测量指标COM比NZ更一致地与ROM的变化方向相符。
椎板切除术导致FE和LB中的ROM和NZ有一定程度的增加，添加横向连接装置对此无影响。尽管椎板切除术在AR中的影响更大，且横向连接装置有可测量的恢复作用，但在这种加载模式下，所有差异都在十分之几度以内。因此，基于这些微小的生物力学变化，添加横向连接装置的临床实用性可能不合理。COM可以作为ROM和NZ测量的补充，或者当它的两个组成部分一起报告时甚至可以作为替代指标，因为它与ROM显示出很强的一致性，有效地区分了松弛和弹性区域的行为，并提供了一个独立于负荷范围的柔韧性测量指标。
