Hart Robert, Gillard Joel, Prem Shilpa, Shea Marie, Kitchel Scott
Orthopaedic Biomechanics Laboratory, Department of Orthopaedics, Oregon Health and Science University, Portland, Oregon 97239-3098, USA.
J Spinal Disord Tech. 2005 Feb;18 Suppl:S115-8. doi: 10.1097/01.bsd.0000132288.65702.6e.
Recently, an unpaired threaded cage has been introduced as a fusion device for the cervical spine. No biomechanical comparison of a stand-alone single interbody threaded cage to a standard plated Smith-Robinson construct has been reported. Accordingly, an in vitro biomechanical comparison of a single threaded cylindrical interbody fusion cage versus a plated Smith-Robinson cervical discectomy and fusion construct was conducted to establish whether a single cylindrical interbody cage in the cervical spine would perform mechanically as well as a plated structural interbody graft.
Six fresh-frozen human cadaveric cervical spines were used for biomechanical testing. Flexion-extension and load-to-failure testing were performed on two single-level discectomy and interbody fusion constructs from each specimen.
Initial range of motion (ROM) was significantly greater for the specimens implanted with a cage than specimens implanted with a structural graft and plate (9.1 degrees +/- 3.7 degrees vs 5.8 degrees +/- 2.4 degrees ; P = 0.040). Initial stiffness in flexion in caged specimens was significantly less than in plated specimens (0.7 +/- 0.3 vs 0.9 +/- 0.3 Nm/ degrees ; P = 0.028). Cage specimens also failed at a significantly lower load than plated specimens (9.8 +/- 3.5 vs 15.8 +/- 4.1 Nm; P = 0.0104).
This study demonstrates that a plated Smith-Robinson cervical discectomy and fusion construct provides greater stiffness and failure load and reduced ROM across operated levels than a single interbody cage construct. Although clinical success may not directly correlate with biomechanical data, these results raise concern regarding the use of a single threaded interbody cage as a stand-alone device for cervical interbody fusion.
最近，一种非配对螺纹融合器已被引入作为颈椎融合装置。目前尚无关于单独的单节段椎间螺纹融合器与标准钢板固定的史密斯-罗宾逊术式结构进行生物力学比较的报道。因此，进行了一项单节段圆柱形椎间融合器与钢板固定的史密斯-罗宾逊颈椎间盘切除融合术结构的体外生物力学比较，以确定颈椎单节段圆柱形椎间融合器在力学性能上是否与钢板结构性椎间植骨相当。
使用6个新鲜冷冻的人体尸体颈椎进行生物力学测试。对每个标本的两个单节段椎间盘切除椎间融合结构进行屈伸和破坏载荷测试。
植入融合器的标本初始活动范围（ROM）显著大于植入结构性植骨和钢板的标本（9.1度±3.7度对5.8度±2.4度；P = 0.040）。融合器标本在屈曲时的初始刚度显著低于钢板固定标本（0.7±0.3对0.9±0.3 Nm/度；P = 0.028）。融合器标本的破坏载荷也显著低于钢板固定标本（9.8±3.5对15.8±4.1 Nm；P = 0.0104）。
本研究表明，钢板固定的史密斯-罗宾逊颈椎间盘切除融合术结构比单节段椎间融合器结构在手术节段提供更大的刚度和破坏载荷，并减少了活动范围。尽管临床成功可能与生物力学数据没有直接关联，但这些结果引发了对使用单节段螺纹椎间融合器作为颈椎椎间融合独立装置的担忧。
