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

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.