Feasibility Study Of Percutaneous Endoscopic Transforaminal Oblique Fixation From Posterior Corner In Lumbar Spine

Background:For common and frequently occurring diseases in the spinal field,such as lumbar disc herniation and lumbar spinal stenosis,we often adopt open surgery after failure of conservative treatment.Lumbar interbody fusion is one of the classic surgical methods for the treatment of degenerative lumbar diseases with a history of more than 100 years.Clinical practice shows that lumbar interbody fusion can effectively improve the out-of-balance state of the spine,maintain the stability of the surgical segment,and promote the interbody fusion.However,strong internal fixation will reduce the original activity of the diseased segments,and increase the compensable motion amplitude of the adjacent segments,thereby leading to abnormal stress distribution of the interbody discs and facet joints in adjacent segments,and accelerating adjacent segment degeneration.At the same time,the disadvantages such as large trauma,excessive bleeding,high cost,long recovery time and postoperative low back pain cannot be ignored.Nowadays,spinal surgery is developing towards minimally invasive as a whole.Form MIS-TLIF to UBE,these techniques have facilitated the development of minimally invasive spine to some extent.There are also many characteristics such as"false minimally invasive,really open" and "big-channel,multi-channel","multiple incisions,large incisions","decompression and fusion separated with fixation","need to general anesthesia or epidural anesthesia","need to transform the intraoperative position","big cage cannot be opened and fixed",etc.View of the present status in the minimally invasive spinal field,our team wants to invent a kind of minimally invasive spinal surgery technique and equipment This new technique can complete decompression,fusion and fixation all at once under a single conventional 7.5mm sleeve.Objective:1.Inspired by the posterior extrapedicular screw fixation on thoracic spine,we creatively proposed percutaneous endoscopic transforaminal oblique fixation from posterior corner in lumbar spine through Kambin' s triangle.The anatomical feasibility and safety of the technique were evaluated by radiographic anatomy and neuroimaging.2.To provide anatomical parameters for the minimally invasive spinal instrument(new interbody fusion cage)developed in the next step,and to carry out finite element analysis on it.Methods:1.Forty-five normal dry adult cadaver specimen were included.Anatomical parameters were measured.Anatomical parameters:?.the anatomical relationship between transverse process and pedicle:the distance from the horizontal center line of transverse process to the center and the superior and inferior border of the pedicle.II.the anatomical relationship between transverse process and rib:the overlap portion between the costal neck and the transverse process.?.the anatomical relationship between transverse process and vertebral body:the relative position of the horizontal midline of transverse process and the vertebral body.?.the anatomical relationship between pedicle and rib:the overlap portion between the costal neck and the pedicle.2.Sixty volunteers(22 men and 38 women)who underwent lumbar CT scans were collected and sent to the GEAW4.4 workstation.As a cohort study,the distances and angles of each path in the sagittal and axial planes were measured and analyzed statistically.3.Sixty volunteers(27 males and 33 females)underwent lumbar MR examination(VISTA,3D-STIR-TSE Sequence).The distances from the working targets to exiting nerve roots and dural sac/traversing nerve roots in the coronal and sagittal planes,and the distances from the exiting roots to the dural sac/traversing nerve roots in the upper and lower endplate planes were measured and statistically analyzed.4.The realization of the new technology puts forward the urgent need for the minimally invasive spine instrument.According to the characteristics of the new technology,we designed a new integrated fixable interbody fusion cage,which can achieve one-stop completion of decompression,fusion and fixation under a single conventional 7.5mm sleeve.At the same time,the finite element analysis of this new integrated fixable interbody fusion cage is carried out.Results:1.The midline of transverse process was located within the range of superior and inferior borders of the pedicle in the thoracic spine.The distance between the midline of transverse process and the center of pedicle was the closest at T6 and T7,but the farthest at T11 and T12.The anterolateral part of transverse process was mostly covered by rib from T1 to T8,but it was less covered from T9 to T12.The midline of transverse process corresponded to the upper 1/3 or middle 1/3 of the vertebral body.The pedicle is completely or mostly overlapped by the rib from T1 to T9 on the anterolateral side.But from T10 to T12,the rib overlapped the pedicle partially.2.The lengths of each path are not less than 40mm,and the longest can be up to 46mm.The paths in full-length group are about 5mm longer than that in medium group.PE(from point P to target E)path was the optimal path.The angles of each path were significantly different(P?0.001),namely,a1>a2>a3,b1>b2>b3,and c1<c2<c3.3.In L1/2-L5/S1,the P values of paired t-test for the distances(c1,c2,c3,c4,c5 and c6)were all less than 0.05.The distances(d1,d2)gradually increased in L1/2-L5/S1(P<0.0001)and the means of d2 were greater than d1(P<0.05).The P values of paired t-test for the distances(s1,s2,s3,s4,s5,s6)were all less than 0.05.4.According to the urgent need for minimally invasive spine instrument,we design the four patents(two patents of invention and two patents of utility model).5.The finite element model of a new integrated fixable interbody fusion cage was established and introduced into Abaqus 6.14-4 software for finite element analysis.There are 223,281 nodes and 551,584 units in Model A(8mm),223,413 nodes and 552,141 units in Model B(10mm),and 223,507 nodes and 552,497 units in Model C(12mm).The maximum stress and maximum displacement values of lumbar vertebral body and lumbar fusion cage in different surgical models were recorded.Conclusions:1.The pedicle-rib unit is a three-dimensional anatomical structure.The pedicle,transverse process,and rib are not completely in the same plane,and their position are varying in different segments.The pedicle-rib unit screw fixation is anatomically feasible.It can be an effective supplement for pedicle screw fixation on thoracic spine.2.Our study confirms anatomic feasibility for PETOFPC and provides anatomic data for the design of new integrated fixable and fused interbody cage.PETOFPC may be a very promising technology and have great clinical significance.3.Kambin's triangle can be used as a working area for oblique fixation from posterior corner in lumbar spine,but the actual safe area is smaller than original cognition.The intersection point(P2)is an ideal "target" for oblique fixation from posterior corner in lumbar spine.It is neuroanatomically feasible to achieve one-stop complete decompression,fusion,and fixation in a single channel under spinal endoscopy.4.A large number of minimally invasive spinal instrument have been designed and developed,among which four patent applications have been accepted by the State Intellectual Property Office,and other patents are being actively application.5.According to the engineering mechanics of finite element analysis,the new interbody cage has high strength and can bear the load of human lumbar movement.It will not destroy the adjacent endplate and cause the settlement.