Anatomical variations of lumbosacral plexus

Basis

Deviations detected during spinal operations have motivated us to start research related to variations of lumbosacral plexus formation. Aim of this work was to find out deviations of its formation from ascension of particular roots from foramen invertebrale and foramina sacralia up to formation of terminal branches.

Set

One hundred lumbosacral plexi have been examined in 50 adult cadavers for a purpose to find out an incidence of neural variations. We have observed participation of Th₁₂ root, L₄ and L₅ roots in its formation, as well as various deviations from ascension of particular plexiform roots up to their ending branches. For lumbal plexus, we have observed four nerve roots and six lumbal nerves; for sacral one, three sacral roots with a share of S₄ and lumbosacral trunk formed of L₄ and L₅ roots and four sacral nerves. We have considered also their course, anastomoses and thickness. We highlight motoric innervation particularities in relation to diagnostics besides anatomical complexity and variability.

Results

Variations on the level of neural roots were common, nerve formations were uncommon. Thickness of neural roots, formation or their absence were dependent on the type of plexus, particularly in sacral area. For lumbal plexus, L₁ root was the thinnest and L₄ root was the thickest. L₃ root was the thickest in six cases. Fifth lumbal root usually completely filled foramen invertebrale. We have observed double ascension of L₄ root from foramen invertebrale in 25 cases and plexiform in five cases. In other cases it was branched in various distance following ascension from foramen invertebrale. Plexiform ascension of L₃ root along with L₄ root was present in two cases. Double ascension of L₃ root was present in four cases. L₂, L₃ along with L₅ roots were doubled in two cases. Iliohypogastric nerve was the longest, ilioinguinal was the thinnest and nervus femoralis was the thickest. Changes in sacral plexus on the level of neural roots have been observed 41-times. Double ascension of L₅ root was present in eight cases and plexiform in four cases. Double S₁ root at ascension from foramina sacralia was present 16 times, S₂ 8 times, S₃ once and S₁ along with S₂ 4 times. S₁, S₂ and S₃ roots were branched in various distance following ascension from foramina sacralia in 15 cases. Truncus lumbosacralis was thickened in 19 cases, a share from L₄ root was thicker as L₅ root in 11 cases. Low level of connection between truncus lumbosacralis and S₁ root was observed in 10 cases. Nervus ischiadicus has branched into tibial and peroneal portions already in minor pelvis in two cases. The level of distance of n. (nervus) gluteus superior, n. gluteus inferior, n. cutaneus femoris posterior and n. pudendus was dependent on the plexus type.

Conclusion

This study enabled us to find out and to describe extraordinary anatomical deviations in formation of neural roots and nerves of lumbal and sacral plexus, undescribed yet.     

A rare variation of posterior cord brachial plexus branching coexisting with the intercalated ectopic muscle

During a dissection of the brachial plexus we found a rare variation of left posterior cord branching coexisting with an unusual intercalated ectopic muscle. This muscle originated from the shoulder joint capsule at the lesser tubercle on insertion of the subscapularis then pierced between the brachial plexus, enclosed by two roots of the radial nerve, and inserted into the upper part of the latissimus dorsi muscle. The variant posterior cord divided into two roots; a thin lateral and thick medial root. The lateral root gave off the thoracodorsal nerve that penetrated and also innervated the ectopic muscle. The medial root gave off five nerve branches; two upper subscapular, one lower subscapular, one axillary and one terminal branch. A terminal branch fused with the lateral root to form a loop enclosing the ectopic muscle then continued as the radial nerve. This type of variation may be useful to interpret unexplained clinical signs and symptoms and provided additional knowledge to surgeons who perform brachial plexus surgery.     

骶后孔(八髎穴)的临床应用解剖学

目的 :为八穴的针灸推拿以及骶后神经和骶管麻醉提供解剖学依据。方法 :我们测量了 30例骶骨标本 ,将骶后中线定为Y轴 ,将通过两骶角的连线定为X轴 ,测定骶后孔中点至两轴的距离 ;并测量骶后孔的口径 ,骶后孔中点至相应骶前孔中点的间距以及每侧 1～ 2 ,3～ 4骶后孔中点间距。结果 :根据统计分析 ,我们确定了两种骶后孔定位方法 ,取得了 1～ 2 ,3～ 4骶后孔中点间距的数值 ;4对骶后孔口径的大小顺序是 :1孔 >2孔 >4孔 >3孔。结论 :两种定位方法可帮助医生对骶后孔进行更为准确的定位 ,避免一些给患者带来的损伤 ,可使一些医疗麻醉等措施得以成功实施 ,有助于提高临床疗效     

骶外侧静脉的应用解剖研究

目的 通过骶外侧静脉的解剖研究,为临床提供形态学资料。方法 选用50具新鲜尸体,经乳胶灌注后,在体视显微镜下观察。结果 骶外侧静脉多为2支型,占51.9％,其中以直接注入髂内静脉的最多见 骶外侧静脉管径左侧为(1.03±0.33)mm,右侧为(1.04±0.28)mm。骶外侧静脉脊支在第1骶前孔多为2支型,在第2～4骶前孔以1支型为多见。在第1骶前孔内脊支多位于外上象限,占52.11％ 在第2～4骶前孔内多位于内上象限,各占63.33％,64.71％和80％。结论 骶前出血是多源性出血,骶外侧静脉出血时要依据其解剖学特点进行有效地止血     

腰骶部脊神经根的临床解剖学

通过临床选择性脊神经后根切断术中观察与测量,为临床提供了重要的参考数据。腰骶神经前、后根解剖会合点至椎间孔距离平均为1.5～2.0cm。前后两根相比,后根明显较前根粗,其中以L_5后根最粗、L_2～S_1各后根内小束的数目为4～18束,平均为7束,临床分离后根时可分为7束,以便进行电刺激选择。这些资料为腰骶部选择性脊神经后根切断术和马尾神经的手术提供了重要依据。     

Clinical importance of ligamentous and osseous structures in the cervical uncovertebral foraminal region

The vertebral artery, cervical spinal nerves, spinal nerve roots, and the bony and ligamentous tissue related to the cervical vertebrae are structures whose anatomy determines the path of a surgical approach. Defining the anatomy and, in particular, determining the precise location of vulnerable structures at the intervertebral foramen and the uncovertebral foraminal region (UVFR), a region defined by the uncinate process anteriorly, the facet joint posteriorly and the foramen transversarium laterally, has critical significance when selecting the safest surgical approach. We studied the anatomy of the vertebral artery, cervical spinal nerves, and spinal nerve roots within the UVFR in six cadaver specimens. We also obtained measurements of bony structures in 35 dry cervical vertebral columns, from C3-C7. The uncinate process (UP) projects superiorly from the posterolateral aspect of each cervical vertebral body, except for the first and second vertebrae. Because the posterior part of the UP lies adjacent to the vertebral artery, spinal nerve, and spinal nerve roots, its resection creates sufficient space to decompress these structures directly. The posterolateral surface of the UP is covered by ligamentous tissue that originates from the posterior longitudinal ligament and protects the neural and vascular structures during their decompression in the UVFR.     

The medial branch of the lateral branch of the posterior ramus of the spinal nerve

In the needle insertion of epidural anesthesia with the paramedian approach, the needle can pass through the longissimus muscle in the dorsum of the patients. When the needle touches a nerve in the muscles, the patients may experience pain in the back. Obviously, the needle should avoid the nerve tract. To provide better anesthetic service, analysis of the structure and where the concerned nerves lie in that region is inevitable. Material and method: We studied five cadavers in this study. Two cadavers were fixed with Thiel’s method. With these cadavers, we studied the nerve running of the posterior rami of the spinal nerve from the nerve root to the distal portion. Three of them were used for the study of transparent specimen, with which we studied the course and size of the nerve inside the longissimus muscle. Results: We observed there were three branches at the stem of the posterior rami of the spinal nerves between the body segment T3 and L5, i.e. medial branch, medial branch of the lateral branch and lateral branch of the lateral branch. The medial branch of the lateral branch supplied to the longissimus muscle. With the transparent specimen, we found that there were different nerve layouts between the upper thoracic, lower thoracic, upper lumbar, and lower lumbar segments in the medial branch of the lateral branch in the longissimus muscle. In the lower thoracic and upper lumbar segments, the medial branch of the lateral branch of the upper lumbar segments produced layers nerve network in the longissimus muscle. L1 and L2 nerves were large in size in the muscle. Conclusion: In the upper lumbar segments the medial branch of the lateral branch of the posterior rami of the spinal nerve produced dense network in the longissimus muscle, where the epidural needle has high possibility to touch the nerve. Anesthetists have to consider the existence of the medial branch of the lateral branch of the posterior rami of the spinal nerve when they insert the needle in the paramedical approach to the spinal column.     

Surgical anatomy of the infratemporal fossa using the transmaxillary approach

Abstract In this study we evaluated the ability of the transmaxillary route to expose the elements of the infratemporal fossa (ITF). Five adult cadaver heads were dissected on both sides, after making a paralateronasal incision. The maxillary branch of the trigeminal nerve served as a superior landmark to progress into the retroantral space and pterygopalatine fossa. The maxillary artery, lateral pterygoid muscle, pterygoid venous plexus, foramen rotundum and foramen ovale were identified. Distances between those elements and angle of approaches of the foramen ovale and foramen rotundum were measured in the horizontal plane. In all cases, the anterior loop of the maxillary artery and the sphenopalatine artery were located in the proximal retroantral fatty space and could be ligated without optic magnification. The maxillary nerve could be followed up to the foramen rotundum at a 44 mm mean distance from the opening. The mean angle of vision to the foramen rotundum was 31°. Under the greater sphenoid wing and lateral to the pterygoid process, desinsertion and partial resection of the lateral pterygoid muscle were required to identify the pterygoid venous plexus and foramen ovale. The pterygoid venous plexus was organized as a compact network of channels between and superior to the muscle fibers it was in close relation with the foramen ovale. Access to the foramen ovale was deep (mean 56 mm) and narrow (20°). Our results indicate that the transmaxillary approach is a minimally invasive procedure that gives an appropriate window to the structures of the retroantral space and to the pterygomaxillary fissure and pterygopalatine fossa. Monitoring of the retropterygoid portion of the infratemporal fossa by this route is inadequate.     

神经根型颈椎病解剖因素探讨

目的　探讨颈神经在椎间孔及脊神经沟处受嵌压的解剖学因素。方法　取 6 0具成尸 (男 2 8,女32 ) ,对颈椎间孔及其脊神经根的前后径、上下径进行观测 ,统计出颈神经根前后径、上下径分别大于或等于椎间孔的前后径、上下径的出现率 ;同时观测脊神经沟外口宽度及其沟内段脊神经前支横径 ,统计出脊神经前支横径大于或等于脊神经外口宽度的出现率。结果　①颈神经根在椎间孔处可造成嵌压 ,其出现率为 2 4 6 % ,其中女性为 35 2 %明显高于男性的 12 5 % (P <0 0 1) ;②颈神经前支在颈椎脊神经沟处可造成嵌压 ,其出现率为 6 3% ,其中男性为 8 9%明显高于女性的 2 9% (P <0 0 1)。结论　颈神经受累不仅与椎间孔狭窄有关 ,而且与脊神经根外径和周围软组织损伤有关 ,临床诊断颈椎病应采用X线片与临床表现相结合方可减少漏诊率。     

腰段脊柱的形态变化与腰腿痛的关系

本文对10具正常和10具腰椎退变尸体解剖观察及20例腰椎平片X线对照分析证实，椎间盘病变，椎体唇状骨质增生，关节突骨质增生，前后纵韧带的钙化使腰椎失稳，由于腰神经在椎间孔内系由内上向外下走行，故当椎间隙变窄，后纵韧带钙化和上关节突骨质增生均可使椎间孔径缩小并压迫脊神经根，引起腰腿痛。     

经皮椎弓根螺钉技术的解剖学基础及其临床意义

目的：为经皮椎弓根螺钉技术提供解剖学基础并在此基础上分析经皮植入椎弓根螺钉较常规开放植入椎弓根螺钉临床应用的优点。方法：选用10具经防腐固定，在解剖显微镜下对胸腰段脊柱后部结构进行逐层解剖，重点观测脊神经后支及其分支、脊柱节段动静脉的后支的来源、走行以及分布规律。结果：脊神经后支的内侧支经骨纤维管下行沿途支配横突棘肌，支配下方小关节突、筋膜和韧带。外侧支向外下行走，沿途支配背部深层肌肉。节段动脉的后支在椎间孔的上外方绕向后下方，走行于脊神经的下方和下位脊椎上关节突的外方，分为内外两支穿行于腰部深层肌肉。节段静脉后支与同名动脉伴行，并与对侧、相邻节段同名静脉在棘突和横突部位构成静脉丛。结论：避免损伤脊神经后支和节段动静脉的后支并运用可视化操作系统的经皮椎弓根螺钉植入技术，是微创脊柱外科一种新的技术手段。     

The female inferior hypogastric (= pelvic) plexus: anatomical and radiological description of the plexus and its afferences—applications to pelvic surgery

AIM OF THE STUDY: We wanted to determine the anatomical features of the inferior hypogastric plexus (IHP), and the useful landmarks for a safe surgical approach during pelvic surgery. MATERIALS AND METHODS: We dissected the IHP in 22 formolized female anatomical subjects, none of which bore any stigmata of subumbilical surgery. RESULTS: The inferior hypogastric plexus (IHP) is a triangle with a posterior base and an anterior inferior top. It can be described as having three edges and three angles; its inferior edge stretches constantly from the fourth sacral root to the ureter's point of entry into the posterior layer of the broad ligament; its cranial edge is strictly parallel to the posterior edge of the hypogastric artery, along which it runs at a distance of 10 mm; its posterior (dorsal) edge is at the point of contact with the sacral roots, from which it receives its afferences. They most frequently originate from S3 or S4 (60%) and then, in one or two branches, often from S2 (40%), never from S1 and in exceptional cases from S5 (20%). There are sympathetic afferences in 30% of cases, usually through a single branch of the second, third or fourth sacral ganglion. All IHPs have at least one sacral afference and sometimes there may be up to three afferences from the same sacral root. Its dorsal cranial angle, which is superior, comes after the SHP (hypogastric nerve or presacral nerve filament); its anterior inferior angle is located exactly at the ureter's point of entry into the posterior layer of the broad ligament. This is the top of the IHP; its posterior inferior angle is located at the point of contact with the fourth sacral root. At its entrance at the base of the parametrium the pelvic ureter is the anterior, fundamental positional reference for the IHP. The vaginal efferences come out of the top of the IHP through branches leading to the bladder, the vagina and the rectum, which originate through two trunks exactly underneath the crossing point of the ureter and the uterine artery: (i) one trunk leading to the bladder runs along and underneath the ureter and divides into two groups, which are lateral and medial, trigonal. (ii) the trunk leading to the vagina runs along the inferior edge of the uterine artery. At the point of contact with the lateral edge of the vagina, it splits into two groups: anterior thin and posterior voluminous. Some of its branches perforate the posterior wall of the vagina and are distributed to the rectovaginal septum in a tooth comb pattern. The inferior branches, which emerge from the inferior edge of the IHP, reach the rectum directly. The dissection of the 22 specimens allowed us to describe three efferent plexuses: a vaginal rectal plexus, a vesical plexus and a inferior rectal plexus. So the IHP's anterior, fundamental positional reference is the pelvic ureter at the point where it enters at the base of the parametrium, then at the crossing point of the uterine artery. The ureter is the vector for vesical efferences, the uterine artery is the vector for vaginal efferences, which are thus sent into the vesicovaginal septum and the rectovaginal septum. This surgical point of reference is of vital importance in nerve sparing during the course of a simple or extended hysterectomy. Any dissection carried out underneath and outside of the ureter inevitably carries a risk of lesions to its efferent, lateral vesical or medial, rectovaginal fibres.     

下颈椎侧方椎间孔镜入路的应用解剖

目的　探讨经下颈椎侧方臂丛后解剖间隙进行椎间孔镜手术的可行性。 方法　40侧成人尸体标本,沿胸锁乳突肌后缘对应C3~7椎体作纵切口,由浅入深经臂丛前、后方按临床手术显露椎间孔途径逐层解剖观测至椎体及附件结构,并模拟手术,牵拉相应组织,测量其牵拉角度、范围。 结果　①臂丛C5~8根长度、根角度及根间距测量结果表明臂丛前、后入路均可直视神经根对椎间孔周围病变进行操作;② C4~6横突与膈神经的距离测量结果表明与臂丛前入路相比,臂丛后入路不易伤及膈神经;③C3~7横突与颈交感干的距离测量结果表明与臂丛前入路相比,臂丛后入路不易伤及颈交感干;④胸导管70%在C7~T1水平汇入静脉角,C7水平臂丛前入路要注意保护胸导管,臂丛后入路不易损伤胸导管;⑤在C7横突水平处将椎动脉向外牵拉的距离为(2.5±0.4)cm,臂丛前、后入路均应注意保护椎动脉;⑥C7横突末端下方至胸膜顶的距离为(1.9±0.4)cm,C7水平臂丛前、后入路均可能伤及胸膜顶。 结论　下颈椎侧方臂丛后解剖间隙可为颈椎间孔镜手术提供安全的手术入路。     

颈椎椎间孔组织对神经根固定作用的生物力学研究

目的：从生物力学角度观察椎间孔组织对神经根的固定作用及其各根之间的差异。方法：采用６例新鲜颈椎标本,保留椎间孔组织,后路暴露神经根。椎间孔外牵神经干,传感器测量椎管内神经根张力。结果：神经根张力随加载外力的增加而增大,其中Ｃ８神经根变化最明显。外力在５００ｇ以内时,Ｃ５、Ｃ６、Ｃ７神经根张力上升缓慢,超过此值,上升明显。Ｃ５、Ｃ６、Ｃ７与Ｃ８神经根断裂时,外力相差１０００ｇ左右。结论：颈椎椎间孔对Ｃ５、Ｃ６、Ｃ７神经根存在明显固定作用,而Ｃ８神经根的固定作用相对较弱。这可能是Ｃ８神经根节前损伤较为多见的生物力学原因     

Anatomy of the presacral venous plexus: implications for rectal surgery

The presacral venous plexus results from anastomoses between the lateral and median sacral veins, and courses into the pelvic fascia covering the anterior aspect of the body of the sacrum. The presacral venous plexus is not directly visible during rectal surgery, and injuries to this plexus may be life-threatening. Dissection of the retrorectal plane or anchoring of the rectum to the sacral promontory as in rectal prolapse surgery exposes the patient to the risk of injury to the presacral venous plexus. The aim of this study was to identify some avascular areas in the anterior aspect of the sacrum in order to lower the occurrence of such injuries during rectal surgery. The pelvis of 10 fresh cadavers was dissected after injection of a colored resin into the inferior vena cava, and the presacral venous plexus was studied. Four avascular tetragonal areas were common to all the specimens. The corners of a square with a side of 3 cm, centered on the anterior aspect of the body of sacrum, were always contained in the avascular areas. The upper side of this square was parallel to a line passing through the sacral promontory, at a 3 cm distance from it. Staples or sutures should be placed in the avascular areas to avoid injuries to the presacral venous plexus.     

Anatomical basis of the extraspinal cord compression

Knowledge of anatomical landmarks of the spinal cord within the vertebral foramen is essential to understand the pathogenesis of spinal cord compression by tumor growth. The spinal cord can spread in the intervertebral foramen, the epidural space, the vertebral body, and the posterior neural arch. The morphology of the spinal cord, the relations of the spinal roots with the vertebrae, the principal fiber tracts, the spinal membranes, and the arterial and venous distribution are described in order to explain and analyze signs and disorders caused by the most frequent tumors involved in spinal cord compression.     

Systematization of the vesical and uterovaginal efferences of the female inferior hypogastric plexus (pelvic): applications to pelvic surgery on women patients

Objective To locate and describe the various efferences of the plexus in order to make it easier to avoid nerve lesions during pelvic surgery on women patients through a better anatomical knowledge of the inferior hypogastric plexus (IHP). Materials and methods We dissected 27 formalin embalmed female anatomical subjects, none of which bore any stigmata of subumbilical surgery. The dissection was always performed using the same technique: identification of the inferior hypogastric plexus, whose posterior superior angle follows on from the hypogastric nerve and whose top, which is anterior and inferior, is located exactly at the ureter’s point of entry into the base of the parametrium, underneath the posterior layer of the broad ligament. Results The IHP is located at the level of the posterior floor of the pelvis, opposite to the sacral concavity. Its top, which is anterior inferior, is at the point of contact with the ureter at its entry into the posterior layer of the broad ligament. The uterovaginal, vesical and rectal efferences originate in the paracervix. Three efferent nerves branch, two of them from its top and the third from its inferior edge: (1) A vaginal nerve, medial to the ureter, follows the uterine artery and divides into two groups: anterior thin, heading for the vagina and the uterus; posterior, voluminous, heading in a superior rectal direction (=superior rectal nerve). (2) A vesical nerve, lateral to the ureter, divides into two groups, lateral and medial. (3) The inferior rectal nerve emerges from the inferior edge of the IHP, between the fourth sacral root and the ureter’s point of entry into the base of the parametrium. Conclusion The ureter is the crucial point of reference for the IHP and its efferences and acts as a real guide for identifying the anterior inferior angle or top of the IHP, the origin of the vaginal nerve, the level of the ureterovesical junction and the division of the vesical nerve into its two medial and lateral branches. Dissecting underneath and inside the ureter and the uterine artery involves a risk of lesion of the vaginal nerve and its uterovaginal branches. Further forward, between the intersection and the ureterovesical junction, dissecting and/or coagulating under the ureter involves a risk of lesions to the vesical nerve, which are likely to explain the phenomena of denervation of the anterior floor encountered after certain hysterectomies and/or surgical treatments of vesicoureteral reflux.     

小鼠臂丛离断对脊髓运动神经元树突结构与形态退变的影响

目的 研究臂丛离断后脊髓运动神经元树突退变与时间和损伤距离的相关性。 方法 在距离椎间孔3 mm或10 mm处处离断小鼠臂丛,术后7、14、28、56 d取材,采用MAP2免疫荧光染色和体视学分析、Golgi-Cox染色和Sholl分析观测颈膨大处脊髓前角运动神经元的树突结构和形态变化;术后28 d比较距离椎间孔3 mm和10 mm臂丛离断对脊髓运动神经元树突的影响。 结果 MAP2免疫荧光显示臂丛离断导致脊髓前角内树突的密度和完整性随时间延长逐渐下降;Golgi-Cox染色和Sholl分析显示运动神经元最长树突、总树突长度、树突最大跨度、树突3级分支的数量均呈时间依赖性下降。与距离椎间孔10 mm处离断组相比,3 mm处离断引起的树突长度退变更为明显。 结论 脊髓运动神经元树突在周围神经损伤后会发生退变,随时间延长其退变程度加重,随损伤部位与脊髓的距离延长树突长度退变程度减轻。     

Stratificational relationship among the main nerves from the dorsal division of the sacral plexus and the innervation of the piriformis.

In order to comprehend more completely the morphology of the nerves to the piriformis, it is necessary to obtain a detailed understanding of the relationship of the origin and the course of these nerves from the dorsal division of the sacral plexus, with reference to the superior and inferior gluteal nerves. Twelve of seven human pelvic halves were carefully dissected in order to examine the origins of the nerves from the dorsal division of the sacral plexus. Six of these pelvic halves were further dissected under a stereomicroscope to examine the nerves to the piriformis. 1. The origin of the superior gluteal nerve was more proximal and dorsal in the sacral plexus than that of the inferior gluteal nerve. 2. The superior gluteal nerve consisted of a thick cranial part and a thin caudal part; the former continued as the inferior branch of the nerve, and the latter, the superior branch. The cranial and caudal parts crossed before reaching the glutei medius and minimus. 3. The nerves to the piriformis arose from three main nerves from the dorsal division of the sacral plexus: 1) the caudalmost root of the superior gluteal nerve, 2) the caudal roots of the inferior gluteal nerve and 3) the common peroneal nerve. Considering the stratificational relationship among the main nerves from the dorsal division of the sacral plexus, the piriformis appears to be composed of parts from different muscle layers.