Analysis Of The Disc Working Zone For Percutaneous Endoscopic Lumbar Discectomy

Objective：Anatomize the healthy adult bodies, measure the anatomical data of theintervertebral foramen of L1-L5and surrounding structure of them，analyze the discworking zone for percutaneous posterolateral approach to the lumbar disc.Methods：Ten cadaveric spines (age：40-60years；height：156-174cm) weredissected.The intervertebral disc height (idh) and the upper diameter of Intervertebralforamen (a1) and the Minimum diameter (a2) and the Bottom diameter (a3) were measured.The distances from nerve root to the lateral edge of articular process at the plane of theinferior endplate of the upper vertebra (c1) and the plane of the superior endplate of thevertebra below (c2) were measured. We also measured the distance between the nerve rootand the dura at two planes of the vertebra endplate (d1, d2) after removing the lamina andarticular processes. The size and morphology of intervertebral foramen were observed.Thedata were recorded and analysized by SPSS19.0.Results：The disc in the intervertebral foramen is contained in the trapezoid shapedzone at sagittal plane or coronal plane. The parameters of the two plane are displayed：idhis （6.87±0.63）mm, h is (14.46±1.18) mm,a1is (9.58±0.74) mm，a2is (5.23±0.72) mm,a3is (6.12±0.49) mm,c1is (8.19±2.48) mm,c2is (9.62±3.26) mm. The values of c1,c2,d1,d2increase as the level goes down, the values of h,a1,a2,a3increase as the level goes downexcept the value of L5-S1segment is lower than L4-L5segment.Conclusion:Normal intervertebral foramen of the upper part is bigger than the lowerpart which looks like a pear shape.Nerve root walks on the upper part of the intervertebralforamen which is the most wide part of the intervertebral foramen. It is surrounded by softtissue to avoid nerve root is being squeezed from peripheral osseous tissue of intervertebralforamen.Intervertebral foramen mirror technology working channel diameter should beless than intervertebral disc height that surgery should choose the right sleeve bymeasuring the CT data in the preoperative.Kambin’s triangle is a three-dimensional structure,in order to facilitate understanding it can be divided into sagittal and coronaryplane two trapezoidal, in the YESS technology discectomy should be done through thesagittal alignment trapezoidal area into coronary the trapezoidal area adept.TESSYS is notthrough Kambin’s triangle to get the intervertebral disc area, it remove the outer edge ofarticular process which can expand intervertebral foramen area，that would make thepiercing of work sleeve easier and it can avoid the intraoperatie injury of nerve root.