The Applied Anatomical Studies Of Anterior Approaches To The Thoracolumbar Spine

The thoracolumbar spine which is always considered as the spine from T₁₁ to L₂, is a special region of the thoracocolmbar junction(TLJ),as cervicothoracic and lumbosacral instability is a potential site.At present,with the development of transportation,building industry,medical diagnosis,and the problem of population structure aging so on.The incidence trend of thoracolumbar spine fractures, tuberculosis,cancer and other diseases has increased significantly.Because of its unique anatomical structure and location,the spinal fracture-dislocation of this region is at the high incidence.According to statistics,the fractures of thoracolumbar spine account for about 2/3 or more,and many happened in the anterior,intermediate column of the spine.Acute injury of thoracolumbar spine and spinal cord has become more and more serious in the most common causes of disability,given a heavy burden to home and society.With the development of medical imaging,particularly CT and MRI applications,it is a growing recognition that,in spinal fractures,the spinal nerve against or oppression suffered mostly from the front spinal dura mater.Most scholars consider that it is by far the most effective treatment to release compression directly,pressure on the spinal cord was caused by objects in front of the spinal cord. To restorate the height of anterior spinal column is the main purpose of surgery. Kaneda thinks that thoracolumbar fractures,associated with nerve injury or front sustained placeholder prompted by spinal radiology examination,should be considered to be oporated through anterior surgery.According to the clinical study that it is not significant to rely on posterior longitudinal ligament to back the bone by posterior approach if intraspinal space was occupied more than 26%(average), however,anterior surgical approach seems an extremely good job.Zdeblick further clarifies that the fracture with incomplete paralysis shows that there would be oppression in front of spinal dura mater,this type of fractures should be operated through anterior approach absolutely.If the fractures,lasted more than 2～3 weeks and associated with nerve injury,can be operated by anterior decompression,and just then posterior surgery has been inappropriate.Thoracolumbar spine is the very site where high-energy burst fractures,incomplete paralysis,spinal tuberculosis and tumor diseases occured,as many diseases are in front of the spinal cord compression, anterior surgery is the preferred way.With anterior open surgery decompressing directly and thoroughly,nerve function may be recover in the greatest degree,integration site is in line with the biomechanical requirements.However,broad exposure,large injury and much bleeding often happen through the open anterior approach.Many complications, such as postoperative pulmonary atelectasis,deep incision infection,diaphragmatic hernia,chylothorax,cerebrospinal fluid effusion,and gastrointestinal dysfunction so on,are reported.In addition,the open anterior approach with defects such as large trauma,slow rehabilitation,long duration of hospitalization,give a heavy burden on the patiants' life and spirit.To develop a minimally invasive surgery with fewer complications,smaller trauma,less pain,and more reliable efficacy has been the direction of the spinal surgeons' efforts.Since from 1993,in which Mack first applied video-assisted thoracoscopic surgery(VATS) to the management of thoracic disc herniation,VATS has been gradually applied to treat the various diseases of the thoracic spine,lumbar spine. Compared to conventional open surgery,VATS has many advantages such as less trauma,less bleeding,faster recovery,etc.The old people with weak,poor cardiopulmonary function could be cared with less interference,and the surgical indications had been expanded greatly.Subsequently,Kim DH and Rudolf Beisse reported separately the feasibility and effectiveness of the thoracoscopic transdiaphragmatic approach(TTA) in the management of TLJ fractures.They both achieved good clinical results.TTA has become one of conventional approaches on clinical spinal surgery.Yong-Long Chi,etc.expanded the operating incision by video-assisted thoracoscopic surgery(enlarged manipulation incision of video-assisted thoracoscopic surgery,EMI-VATS).He changed VATS for EMI-VATS,which is the minimally invasive technique,only with the light source and camera system of thoracoscopic,connected conventional open surgery to video-assisted thoracoscopic surgery.Under direct observation and operation, mini-incision surgery applied to treat many spinal diseases,such as the thoracic vertebral body biopsy,fracture fixation,decompression surgery.And compared to the traditional open surgery,the former is much better in surgical time,length of stay and bleeding than open surgery.The technology not only has advantages of open anterior surgery,such as decompressing directly and thoroughly,non-injury of the posterior column stability,and integration site is in line with the biomechanical requirements,but also leaves patients less trauma,less pain,faster recovery,less complications and good appearance.However,anatomical structures among the thoracolumbar,such as blood vessels,nerves,lymphatic vessels,are more complex. Complications,such as hemorrhage,chylothorax,sympathetic trunk and nerve root injury,are still existed during endoscopic surgery. Whether open or video-assisted anterior thoracolumbar surgery,postoperative complications are caused by many reasons.To a large extent,the operators without being familiar with the location of the local anatomy often cause complications.At home or abroad,there are a lot of applied anatomical studies of posterior surgery on thoracolumbar spine.At present,the applied anatomy of retroperitoneal space has also been studied a lot,but many of them pay much attention on the surgical approach of lower lumbar spine,kidney and adrenal.The systematic study of applied anatomy on the anterolateral thoracolumbar spine is not perfect,and the patients who requir to be treated through anterior surgery has gradually increased trend.To further clarify the positions of the local anatomical structures,and to explore the advantages of anterior approach on thoracolumbar spinal surgery,we carried out the applied anatomical research.Our research includes the following two parts:Chapter.1 The Applied Anatomical observation and measurement of vessels and nerves on the lateral face of thoracolumbar spineObjective:Observe the anatomical relationship of vertebral body,intervertebral disc and their surrounding anatomical structure on the lateral face of thoracolumbar spine,to provide the basic anatomy for the anterior surgical approach to thoracolumbar spine.Methods:16 adult human cadaveric specimens(8 male,8 female,32sides) were observed to record the course,distribution and relation of vessels and nerves on the lateral face of thoracolumbar spine.Measurement indicators:Firstly,at the median line on the side of spine,the distance between upper segmental artery and lower segmental vein (absence of segmental vessels,the distance between upper segmental artery and vein or the mid-level of vertebral body was measured);Secondly,the distance between intervertebral foramen and the sympathetic trunk;Thirdly,at the mid-point of disc, the distance between sympathetic trunk and the greater splanchnic nerve.Results:On the lateral face of the thoracolumbar spine,there was a "safe region" which was constituted by segmental vessels,sympathetic trunk,greater splanchnic nerve or lumbar plexus.Intervertebral space without any important vessels and nerves existed in the "safe region".In T_10/11 and T_11/12 intervertebral spaces,"safe region" in the bilateral area exists significant difference(P＜0.05).On the left side,the area of each "safe region" was followed by 17.54mm×17.53mm,20.50mm×14.56mm.On the right side,it was followed by 17.54mm×27.85mm,20.50mm×21.47mm.However,in T₁₂/L₁,L_1/2 and L_2/3 intervertebral spaces,there was no significant difference in the bilateral area(P＞0.05),followed by 24.56mm×19.95mm,27.37mm×25.31mm, 28.28mm×27.51 mm.Conclusions:1.On the lateral face of the thoracolumbar spine,intervertebral space existed in the "safe region" without any important vessels and nerves.Must spaces can be provided during the anterior surgical operation.Single-segmental surgery can be carried out at the region between the adjacent segment of artery without segmental artery ligation;In order to minimize segmental artery ligation,intervertebral disc could be considered as anatomical landmark so that vessel and nerve would be less injuried.The incidence rate of operative complications would be decreased.2.On the lateral face of the thoracolumbar spine,when lesions in the T_10/11, T_11/12 intervertebral space,a relatively larger operation space can be provided through the right side approach;At T₁₂/L₁,L_1/2,L_2/3 vertebral space,there is no significant difference in operation spaces between the left and the right side,surgical approach could be selected according to the site of lesion.However,actually,the aortic and its branch is of good elasticity,less artery-related complications occur during surgery;While the right side of surgery at the thoracolumbar spine,operation spaces is near the inferior vena cava,what's more,the wall of the inferior vena cava is very thin,badly flexible,easily to damage.And the effects of diaphragmatic elevated by the liver,so that surgery should choose the left side.Chapter.2 The applied anatomical studies on trans-diaphragmatic anterior approaches with video-assisted thoracoscopic surgery on the upper lumber spineObjective:To study the anatomical landmark to anterior surgical approach surgery on the upper lumber spine,to provide basic anatomy for transdiaphragmatic anterior approaches with video-assisted thoracoscopic surgery on the upper lumber spine.Methods:8 adult human cadaveric specimens(5 male,3 female) were selected to imitate transdiaphragmatic anterior approaches with video-assisted thoracoscopic surgery on the upper lumber spine.Exposure of the spine below L₁ usually requires detachment of the diaphragm.Leaving a 1～2cm rim of the attachment to facilitate closure,After departed diaphragm along the spine-line,retroperitoneal space was exposed,then isolated the medial arcuate ligament of diaphragm muscle,and then separated and removed psoas major muscle.At last,lumbar blood vessels,nerves and other structures were fully exposed on the left side of the upper lumber spine.Observed diaphragm and inferior phrenic artery,assessed the applied anatomical significance of pleural polyline,retroperitoneal space,medial arcuate ligament and crura of diaphragm in the surgical approach.Measurement indicators:Firstly,the distance between pleural polyline and artery of L₂,and medial arcuate ligament,and the piercing point of greater splanchnic nerve.Secondly,the distance between medial arcuate ligament and artery of L₁,and artery of L₂,and the piercing point of sympathetic trunk(absence of segmental vessels,the distance between upper segmental artery and vein or the mid-level of vertebral body was measured).Results:L₁ artery located in the middle of the L₁ vertebral body,about(19.68±1.27) mm below the pleural polyline,can be easily exposed through separating down parietal pleura at the spaces of T₁₂/L₁ disc.Greater splanchnic nerve,which is on the spinal anterolateral,aortic rear,semi-azygos vein lateral side,always passes through diaphragm on the anterolateral side at the Medium-up L₁ vertebral body,about (27.96±1.40) mm below the pleural polyline.After departed diaphragm,the retroperitoneal adipose tissue was exposed,and there are no important blood vessels, nerves and other structures at the retroperitoneal space.The existence of non-vascular plane is possible;Surgical process at this level can be more free,you can not damage internal organs,blood vessels and nerves.The retroperitoneal adipose tissue could be regarded as a very important surgical plane for transdiaphragmatic anterior approaches with video-assisted thoracoscopic surgery on the upper lumber spine.The medial arcuate ligament,upward from the level of L₁ artery about(5.37±0.95)mm,down from the level of L₂ artery about(22.94±2.76)mm, covers the upper part of the psoas major muscle,attaching from the sides of first and second lumbar vertebrae to the tip of the L₁ and L₂ transverse processes. Sympathetic trunk passes through diaphragm between medial crus and middle crus, the distance between the highest point of the medial arcuate ligament and the piercing point of sympathetic trunk is about(23.43±1.12) mm.Sympathetic trunk will not be injuried if the operation was carried out at the back-lateral side of middle crus.Intervertebral space existed in the "safe region" without any important vessels and nerves.A longitudinal separation of psoas major muscle at the junction of the former and medium is very safe for avoiding the injury of lumbar sympathetic trunk, lumbar plexus and the vascular in the deep surface.Conclusions:1.On the side of the upper lumbar spine,pleural polyline(pleural lower bound), medial arcuate ligament and middle crus are the very important anatomical marks for transdiaphragmatic anterior approaches with video-assisted thoracoscopic surgery on the upper lumber spine.2.There are no important blood vessels,nerves and other structures at the retroperitoneal space.The existence of non-vascular plane is possible;Surgical process at this level can be more free,you can not damage internal organs,blood vessels and nerves.The retroperitoneal adipose tissue could provids a very important surgical plane for transdiaphragmatic anterior approaches with video-assisted thoracoscopic surgery on the upper lumber spine.3.Intervertebral space existed in the "safe region" without any important vessels and nerves.A longitudinal separation of psoas major muscle at the junction of the former and medium is very safe for surgical approach to the upper lumber spine.4.From the point of the anatomy,we can concluded that transdiaphragmatic anterior approaches with video-assisted thoracoscopic surgery on the upper lumber spine surgical approach is safe and feasible.