Neurosecurity Study Of The Percutaneous Endoscopic Interlaminar Discectomy

Research backgroundLumbar disc herniation(LDH)is one of the most common diseases leading to pain in waist and lower extremities.Generally,it is managed by conservative therapy.Surgical treatment is necessary for patients who suffer from severe neurological dysfunctions and have no sufficient improvement from conservative treatment.Traditional posterior fenestration discectomy,a classical surgical procedure for LDH,often causes big surgical trauma and massive haemorrhage due to the open surgical method,does big damage to the spinal structure,and possibly leads to iatrogenic lumbar instability after operation.Furthermore,it often results in adhesion of nerve roots and epidural scar hyperplasia that trigger intractable failed back surgery syndrome(FBSS),which has brought enormous suffering to patients.Minimally invasive percutaneous endoscopic spine surgery has experienced rapid development in recent years due to less trauma,fast recovery after operation,less complications and a lower surgery cost.Percutaneous endoscopic lumbar discectomy(PELD)is achieved through transforaminal approach and interlaminar approach.Both the earliest Yeung endoscopy spine system(YSSS)and the popular transforaminal endoscopic surgery system(THESSYS)are transforaminal techniques.Although such approach has been improving unceasingly,the blockage of some levels by iliac crest,lumbar foramen stenosis and other unique anatomical characteristics limit its application in some patients.The failure rate of transforaminal technique is very high for intraspinal giant prolapsed or highly migrated LDH.Furthermore,since there are abundant vascular plexuses in intervertebral foramen and exiting nerve roots,transforaminal technique is very likely to cause massive haemorrhage and nerve root injury.For interlaminar technique,PELD is achieved through posterior interlaminar approach with which spine surgeons are familiar,and has been supported by many scholars at home and abroad due to such advantages as simple location technique,short X-ray exposure,less surgical trauma,less haemorrhage,short operation time and satisfying clinical efficacy.However,full-endoscopy spine surgery is subjected to bony structure,neuroanatomic structure and other factors,so it is mainly used at L5/S1 in clinical practice,and there are very few reports on its application at L4/5 and above.Constant improvements in instruments for spine surgery make it possible to accurately remove the inferior margin of vertebral plate by using micro milling drill and allow adequate exposure of interlaminar space and ligamentum flavum,without affecting the spine stability.Therefore,the feasibility and safety of full-endoscopy spine surgery through interlaminar approach for the treatment of LDH should be further studied.Minimally invasive spine surgery technique has a narrow surgical field,relatively insufficient operating space and less evident anatomic landmarks for reference during operation.Moreover,the morphology and positions of dural sac and nerve root are illegible under endoscope,which partially contributes to the high incidence of nerve injury during minimally invasive spine surgery.Hence,the development of minimally invasive spine surgery technique cannot be separated from intensive studies on spinal anatomy,especially those focusing on "neural structures".Surgeon are required to understand the anatomical layer of the surgical approach and master the inherent anatomical characteristics of neural structures and their positions in relation to the adjacent structures.The existing literatures on spinal anatomy mostly come from studies on cadavers.However,these researches based on shriveled cadavers cannot properly reflect the accurate positions of nerve roots relative to the adjacent structures since dehydration of muscular and nervous tissues leads to changes in the local fine anatomic structures.As for studies on fresh cadavers(mostly aged cadavers),it is nearly impossible to obtain the physiological and pathological data before their deaths,and degenerative changes often occur to the lower back.As a consequence,there might be some disparity between the anatomical data obtained from shriveled or fresh cadavers and those from normal persons.Therefore,to promote the development of minimally invasive spine surgery,it is imperative to carry out studies on living tissues of human body,especially those about the relationship between nerves and the adjacent anatomical structures in vivo.At present,X-ray and computed tomography(CT)are very common in the measurement of the osseous anatomy,but both cannot clearly display the nervous tissue.Although common magnetic resonance imaging(MRI)has unique advantages in measuring soft tissue,but it shows poor sensitivity to complex lumbosacral nerves.Along with the progress of imaging techniques,magnetic resonance neurography(MRN)is able to suppress the signals from muscles,fat,vessels and other adjacent tissues by resorting to diffusion tensor imaging(DTI),which better highlights the anatomical characteristics of nerves and provides necessary conditions and a foundation for furthering studies on the anatomy of nerve structures in vivo.Related literatures both at home and abroad have demonstrated that the MRN-based spinal nerve imaging technique is reliable,clear and relatively accurate in data measurement.MRN allows a direct display of the signal differences between spinal nerves and the surrounding vessels,muscles and fascia,and can even achieve the imaging effect similar to noninvasive dissection.Recently,some foreign scholars have begun to measure the nerve parameters in the operative region of transforaminal endoscopy spine surgery by using MRN to evaluate the surgical approach and intraoperative nerve safety,but the data of nervous structures in the operative region of interlaminar percutaneous endoscopic lumbar discectomy(IL-PELD)are scarcely measured.Hence,we propose to carry out a detailed and systematic study on lumbar nerves and the adjacent structures with the further use of MRN and explore more about the safety of IL-PELD,which is of great significance for reducing complications related to operative procedures and guide the development of instruments for minimally invasive spine surgery.The objective of this study was to measure the anatomical parameters of nerves at L2?S1 and the surrounding structures by using MRN technique and to evaluate the nerve safety and feasibility of IL-PELD at L2/3?L5/S1.This project was implemented in two parts:First,the normal anatomical parameters of nerve roots at L2?S1 and the adjacent structures of healthy adults were measured by using MRN technique in order to provide theoretical evidence for the nerve safety of IL-PELD;Second,based on the measured anatomical parameters of nerves at L2?S1 and the surrounding structures by using MRN technique,we evaluated the feasibility of interlaminar approach,and observed and analyzed the clinical efficacy of IL-PELD to demonstrate the feasibility and nerve safety of such surgical method.PART ?Neuroimaging Study ofthe percutaneous endoscopic interlaminar discectomyObjectiveTo discuss the accuracy of spinal nerve imaging(MRN)in measuring the anatomical parameters of lumbar spinal nerve roots;To measure lumbar spinal nerve and anatomical parameters of adjacent structures of a group of adults,inorder to assess the neurological safety in treatment of lumbar intervertebral disc herniation by translaminar approach under complete endoscopy.MethodsAll patients underwent MRN,coronal scan and lumbosacral plexus reconstruction to measure the anatomical parameters of lumbar spinal nerve and adjacent structures.20 healthy adult male and female volunteers respectively,with no history of lumbar and leg pain,lumbar scoliosis or lumbar degenerative changes were selected.The three-dimensional images were scanned in sagittal,coronal and transverse positions,and the distances of nerve roots from the starting point of dural sac,the starting point of nerve roots to the corresponding upper end plate of vertebral body,the angle between nerve roots and dural sac,the distance between nerve roots and the lateral edge of dural sac,the distance between the facial center of inferior articular process and the lateral edge of dural sac were measured in coronal position.The corresponding imaging anatomical parameters were compared with the diameter and operating space of the spinal endoscopy cannula,and the above indexes were analyzed statistically.ResultsFrom L2 to S1,the lower vertebral body segment,the higher starting position of the nerve root,the bigger angle between the nerve root and the dural sac and the longer the positive distance from the starting point of the nerve root to the upper edge of the corresponding vertebral body.The distance between the nerve root and the ipsilateral dural sac edge,and the distance from the center of the articular surface of the inferior facet joint to the outer edge of the dural sac gradually increases.ConclusionMRN can accurately reflect the anatomical parameters of nerve roots and adjacent structures,which can be used to evaluate the neurological safety of the spinal nerve during the invasive surgical approach.PART ?Clinical application of magnetic resonance neurography in the percutaneous endoscopic interlaminar discectomyObjectiveTo measure the direct effects of pre-operativemagnetic resonance neurography(MRN),and analyze the procedure and clinical outcomes of the percutaneous endoscopic interlaminar discectomy,in order to demonstrate the feasibilityand safty of the interlaminar approach.MethodsIn this study,127 patients who underwent percutaneous endoscopic lumbar discectomy(PELD)and were followed up by more than 12 months,were retrospectively evaluated.The pre-operative demographic data were collected.In addition,the coronal scan and the reconstruction of the lumbosacral plexus were examined to measure the distance between the nerve root and the dural sac at the coronal plane.Furthermore,the post-operative and pre-operative visual analog scale(VAS)scores and Oswestry Disability Index(ODI)were compared.ResultsThe mean and minimum values of distance T between the nerve root and dural sac of L5/S1 to L2/3 on the operation side of the MRN images were all larger than 7.3mm,which is the diameter of the working canal.During the follow-up,VAS and ODI data improved significantly compared with their corresponding pre-operative scores(P<0.01).Regarding the post-operative complications,there were 2(1.57%)cases of hypesthesia and 3(2.36%)cases of neuropathic pain,which were transient and alleviated in 3 months.In addition,there was 1(0.79%)case of intervertebral space infection and 1(0.79%)dural tear.No relapse of disc herniation and iatrogenic instability occurred by the end of the last follow-up.ConclusionThe MRN indicates that the incidence of herniated disc impingement increases over the distance between the nerve root and the dural sac,thus making the interlaminar approach more suitable for the treatment of herniation.The procedures and clinical outcomes of the IL-PELD demonstrate the safety and advantages of the interlaminar approach.Research significanceThis reserch is dedicated to the neurosafety study of PELD.And the MRN technique was used to study the anatomical relationship between spinal nerve roots and adjacent structures in the spinal canal.It is determined that the L2/3?L5/S1 discectomy through the interlaminar approach has a safe nerve working area,which provides a neruoimaing basis for this surgical approach.At the same time,the neurological safety of PELD for the L2/3?L5/S1 disc herniation was confirmed through the clinical operation observation.The results of this study are helpful in reducing the intraoperative operation-related complications,and are of great significance for guiding the research of clinical surgical methods and the development and application of spinal minimally invasive surgical instruments.However,the clinical feasibility of the treatment of high lumbar disc herniation such as L2/3 and L3/4 still needs further investigation.