Kotani Y, Cunningham B W, Cappuccino A, Kaneda K, McAfee P C
Orthopaedic Biomechanics Laboratory, Union Memorial Hospital, Baltimore, Maryland, USA.
Spine (Phila Pa 1976). 1996 Feb 1;21(3):278-87. doi: 10.1097/00007632-199602010-00005.
Using a sheep model, clinically practical posterolateral intertransverse process fusion was successfully achieved and biomechanically tested to determine the load-sharing environment provided by spinal instrumentation and posterolateral fusion mass following solid arthrodesis.
To quantify the in vivo load-sharing capacity of spinal instrumentation on augmenting the posterolateral intertransverse fusion. The hypothesis was that transpedicular screw fixation maintains the biomechanical contribution to the posterolateral fusion stability even after successful arthrodesis because of its providing anterior and middle column support.
Although many previous studies have documented the biological and biomechanical advantages of posterolateral fusion, it is known that posterolateral fusion without spinal instrumentation allowed significant remaining motion at the fused segment even after the solid arthrodesis. Whether spinal instrumentation, especially transpedicular screw fixation, augments in vivo posterolateral fusion stability after solid arthrodesis has not been previously investigated.
Radiographic, macroscopic, and biomechanical analyses of a posterolateral intertransverse process fusion model were performed on 18 sheep at 4 months postoperatively. The load-sharing contribution of the spinal instrumentation was calculated based on the stability with or without spinal instrumentation tested in five loading modalities. Histomorphometry of the vertebral body spanned by spinal instrumentation provided the information regarding the biological effect of the load-sharing capacity of spinal instrumentation on bone remodeling.
All sheep who received posterolateral intertransverse process fusion demonstrated successful solid arthrodesis and high biomechanical quality of the posterolateral fusion mass when compared to previous posterolateral fusion models. The significant difference in stiffness between fixation and subsequent fixation removal was observed in flexion, despite maintaining high lateral bending stiffness equivalent to the fixation (with instrumentation) level. This significant load-sharing contribution of spinal instrumentation detected in flexion corresponded to 27% when compared to the fixation level. The qualitative and quantitative bone histology showed 64% of the volumetric density of bone in the fixation group when compared to that of the sham group as well as narrow trabeculae and reduced connection of trabeculae.
The continuance in support offered by transpedicular screw fixation was assured in vivo after the solid posterolateral intertransverse process fusion. This was clearly demonstrated under eccentric loads in a sagittal plane, suggesting that transpedicular screw fixation was able to provide anterior and middle column support and resist eccentric loads.
利用绵羊模型，成功实现了临床实用的后外侧横突间融合，并进行了生物力学测试，以确定在坚实的关节融合术后脊柱内固定器械和后外侧融合块所提供的负荷分担环境。
量化脊柱内固定器械增强后外侧横突间融合的体内负荷分担能力。假设是，即使在成功的关节融合术后，椎弓根螺钉固定因其提供前柱和中柱支撑，仍能对后外侧融合稳定性做出生物力学贡献。
尽管此前许多研究记录了后外侧融合的生物学和生物力学优势，但已知即使在坚实的关节融合术后，无脊柱内固定器械的后外侧融合在融合节段仍允许显著的剩余活动。脊柱内固定器械，尤其是椎弓根螺钉固定，在坚实的关节融合术后是否能增强体内后外侧融合稳定性，此前尚未进行研究。
对18只绵羊在术后4个月进行后外侧横突间融合模型的影像学、宏观和生物力学分析。基于在五种加载方式下测试有无脊柱内固定器械时的稳定性，计算脊柱内固定器械的负荷分担贡献。对脊柱内固定器械跨越的椎体进行组织形态计量学分析，以提供有关脊柱内固定器械负荷分担能力对骨重塑的生物学效应的信息。
与先前的后外侧融合模型相比，所有接受后外侧横突间融合的绵羊均显示出成功的坚实关节融合以及后外侧融合块的高生物力学质量。尽管在侧方弯曲时保持与固定（使用内固定器械）水平相当的高刚度，但在屈曲时观察到固定与随后去除固定之间的刚度存在显著差异。与固定水平相比，在屈曲时检测到的脊柱内固定器械的这一显著负荷分担贡献相当于27%。定性和定量骨组织学显示，与假手术组相比，固定组的骨体积密度为64%，且小梁狭窄，小梁连接减少。
在坚实的后外侧横突间融合术后，椎弓根螺钉固定在体内提供的支撑得以持续。这在矢状面偏心负荷下得到了明确证明，表明椎弓根螺钉固定能够提供前柱和中柱支撑并抵抗偏心负荷。
