脊突間裝置(Coflex and Coflex-F)在非融合與融合手術的生物力學分析

Abstract

在脊椎病變中，椎間盤初期退化常造成神經壓迫，形成腰椎狹窄症(Stenosis)。為改善神經壓迫而施予減壓手術，傳統的減壓手術會造成其他後續病發症，因此近年發展屬於非融合手術(Non-Fusion)的脊突間裝置Coflex希望能減少此類問題。椎間盤退化程度嚴重時會造成椎體不穩定，因此需要使用融合手術(Fusion)，新型的脊突間裝置Coflex-F可以改善傳統椎弓螺釘在手術過程的風險。 本研究利用有限元素軟體建構出五節的腰椎模型。第一階段，將脊突間裝置Coflex與Coflex-F分別放置腰椎第三與第四椎節之間，探討在非融合手術時的影響。第二階段，則將TLIF和 ALIF椎間融合術搭配Coflex-F於腰椎第三與第四椎節之間，探討融合手術的效果。第三階段，則將TLIF椎間融合術搭配Coflex-F於腰椎第三與第四椎節之間，探討是否可以使用在微創的融合手術。以上研究的邊界條件則都施加400N的跟隨負荷(Follower load)，並使用混合控制方式(Hybrid test method)針對腰椎生理學動作進行分析比較。 第一階段結果發現，Coflex在手術端可以穩定後彎(角度減少70%)、側彎(角度減少8%)與扭轉(角度減少4.3%)，並且保留了前彎的活動(角度增加8%)；對於鄰近端，後彎時有明顯的影響(角度增加20~24%)。然而Coflex-F在手術端可以穩定所有動作，特別是前彎動作(角度減少52%)；在鄰近端，前彎(角度增加17~18%)與後彎(角度增加20~24%)有明顯的影響。第二階段結果發現，ALIF融合術搭配Coflex-F的穩定效果較好。第三階段結果發現，TLIF融合術搭配Coflex-F無法提供較好的穩定效果。

In current society, degenerative disc disease is a very common situation. It can cause nerve root compression, lumbar spinal stenosis, and lumbar instability. In order to relief patients’ symptom, decompression and spinal fusion surgery were common practices by surgeons. In recent years, the concept of interspinous process Coflex device of non-fusion surgery is emerging to improve the complication of decompression surgery. The Coflex-F device is a minimally invasive lumbar fusion device that provides significant segmental stability with all the advantages of an interspinous implant. It can alternative to traditions pedicle screw fixation as an adjunct to spinal fusion. This study was divided into three researches with purposes to investigate the biomechanical behavior between the Coflex and Coflex-F devices using finite element model of the L1-L5 lumbar spine. The first research was to investigate the biomechanical differences between the Coflex and Coflex-F implanted into the L3-L4 segment in non-fusion surgery. The second was to investigate the biomechanical characteristics of TLIF and ALIF spinal fusion combined with Coflex-F and with pedicle screw fixation implanted into the L3-L4 segment in fusion surgery. The third was to investigate the biomechanical characteristics of TLIF combined with Coflex-F and with unilateral pedicle screw fixation and translaminar facet screw fixation implanted into the L3-L4 segment in minimally invasive lumbar fusion. A 400 N follower load and a 10 N-m moment were applied to the intact model to mimic physiological motions. The other implanted models to be compared with the intact model were also subjected to 400 N follower load and moments that produced overall motions equal to those of the above intact model (i.e. the hybrid test method). The result of the first research showed that, the Coflex implantation can provide stability in extension (ROM decreased 70%), lateral bending (ROM decreased 8%), and axial rotation (ROM decreased 4.3 %) at the surgical segment, and retain flexible in flexion (ROM increased 8%). It had no influence at adjacent segments except during extension (ROM increased 20~24%). The Coflex device can restraint extension motion, and provide more space for foramen and spinal canal. Therefore, The Coflex device may improve or relieve the stenosis. In addition, the Coflex-F implantation can provide stability in all motions, especially in flexion (ROM decreased 52%). It had influence at adjacent segments during flexion (ROM increased 17~18%) and extension (ROM increased 20~24%). Therefore, the Coflex-F device can be used to treat stenosis combined with mild degenerative disc disease. The result of the second research showed that, the ALIF combined with Coflex-F can provide more stability. The result of the third research showed that, the TLIF combined with Coflex-F cannot provide sufficient stability.