| With the increasing average life expectancy in China, the number of the cervical spondylosis patientswho are mainly with degeneration was also increased. In clinical practice,the type of cervical spondylosis can be divided into nerve-root, spinal cord, vertebral artery type, sympathetic, and mixed, the nerve root type (70%) is the most common. The clinical manifestationsof the nerve-root cervical spondylosis were sensory, motor and reflex disorder aligned with the spinal nerve root distribution. The compression of cervical nerve roots in the intervertebral foramen is one of the most common courses of clinical cervical radiculopathy. The exact anatomic structures that affect the nerve root vary from one individual to another. Nerve rootsgo throughthe lateral foraminal of the vertebral Canal, so they have a very close relationshipwith the surrounding soft tissue.The stenosis of the bone fibrouswithinthe intervertebral foramen, soft tissue hyperplasia, hypertrophy, pathological changes of adhesion cancompress the nerve roots causing disturbance of blood circulation, varying degrees of sensory and motor dysfunction. Pre-, inter-, and extraforaminal structures, such as the ligaments of Trolard, Hofmann, Spencer, suspensor radial ligaments, and the denticulate ligaments,have been regarded as a possible source for neuralgia. Therefore,determining the underlying cause of the irradiating pain more precisely should await detailed anatomical studies of the extraforaminal region particularly.Severe avulsion of the brachial plexus often causes nerve root or nerve damage, but the location, degree of nerve injurydiffers with different spinal nerves. Kawai reported that the injury ofC5 nerveoften occurred at the lateral side of the ganglion, butC7 and C8 nerve often occur inside the ganglion, the situation ofC6 and T1 nerve was neutral. Gu Yudong reported, C5, C6, C7 nerveare not prone tosimple root avulsion, they often causes postganglionic nerve damage in front of the avulsion. If the violence persists, the injury will occure occur inside the ganglion on the basis of the injury outside the ganglion, but the simple root avulsion in C8 and T1 nerve is very common. The exact anatomic structures that affect reasons vary from one individual to another. Most scholars believe that it is due to nerve root biomechanical differences and different characteristics ofthe nerve root anatomy.Along with the development of cervical spine surgery in spine surgery, people’s requirements about the effect of the surgery and security are increased. There is an urgent need for spine surgeons to improve the operative procedures and methods. In recent years, with the rapid developmentof the minimally invasive spine surgery, endoscopic techniques have been successfully applied in the cervical, which mainly through the anterior and posterior approach. Till now,lateral cervical intervertebral foramen approach technique hasn’t been reported. Whether a minimally invasive surgical approach through the lateral intervertebralintervertebral foramencan address all these problems of the clinical lesions of the cervical intervertebral foramen and its surrounding structures?Above, these are in urgent need of clinical anatomy of the cervical intervertebral foramen to provide more detailed anatomy basis. At present, the domestic and foreign scholars on the research of the cervical intervertebral foramen mainly concentrated in the bony structure of intervertebral foramen area, anatomic research for the surrounding soft tissue which has a closer relationshipwith the nerve rootin the cervical intervertebral foramenis very rare. That to some extent limits the development and progressof the related diseases diagnosis and treatment.Low back pain caused by lumbar disc herniation and lumbar spinal nerve branches entrapment is one of the most common diseases. Both surgical and conservative treatments, many of these methods are perfomed in the intervertebral foramen or transforaminal operation. At present, some enlightening researcheshave been conducted for the ligaments within the lumbar intervertebral foramina.The discussion forits physiology, pathology and clinical significance has been performed. Even though ligamentous structures associated with the IVFs of the human lumbar spine have been noted as early as the 19th century, it was not until 1969 that Golub and Silverman conducted the first serious study of these structures.They classified obliquely placed bands into superior and inferior corporotransverse ligaments while tranversely running bands were referred to as transforaminal ligaments. Although TFLs have usually been described as being anomalous, they have more recently been referred to as normal structures. They may serve as a protective mechanism against traction. In addition, these ligaments play an important role in the positioning of the nerves in the intervertebral foramen. Meanwhile, many scholars agree with that TFLsmay reduce the space available for the spinal nerve root within the IVF. Regular physical activities that produce flexion, extension, lateral bending, or axial rotation in the spine without any pain or symptoms affect the anatomical relationship of the nerve root and adjacent connective tissue. Pathologies of ligaments, such as calcification, ossification and hyperplasia occur with degeneration. They hypothesize that these pathologies can also occur in transforaminal ligaments.In this circumstance, any compromise of the IVF may impinge on the nerve root. Pathological ligaments increase the sizes and change the shapes; as a result, changed transforaminal ligaments occupy more foraminal space. Since the boundaries of foramen areformed by bony tissue and stiff connection tissue, there is no adequate buffer space around nerve roots inside the foramen, and pathological transforaminal ligaments can possibly compress the nerve roots directly. Subsequent researchers also have disagreements, and made some relevant anatomy and biomechanical experiments. The intervertebral foramen ligamentsare regarded as an important cause of lumbocrural pain by the doctors who treat lumbar intervertebral disc protrusion by needle-knife therapy.Intraforaminal structures around the spinal nerve root were recognized by Hofmann, who observed that within the neural foramen the nerve root dural sleeves were linked to the periosteum by firm strands of fibers. Spencer in 1983 further described these ligaments and called them "lateral Hofmann ligaments". He then interpreted its function. Spencer stresses the existence of these lateral ligaments, they argue that these ligamets may play a dural role in pathogenesis of sciatica by their tethering the nerve root over a disc protrustion, a pressure-induced neuropathy can develop, by their applying traction forces to the posterior longitudinal ligament and vertebral periosteum, somatic pain may be produced.Akdemirs argued that, together with the fatty tissues, the intraforaminal ligaments provide support inside the root foramen and prevent it from touching the surrounding tissues. In this way, friction during the root’s flexion, extension, and lateral bending movements is eliminated.Additionally, these ligaments surrounding the dura make electrophysiological transmission, CSF flow, and blood circulation easier. In cases of disc surgery for herniation of disc material or conditions such as spondylolisthesis, the foramina can become degraded.Degenerative processes such as spinal stenosis or postoperative scar tissue cause constriction in the foramina and affect the intraforaminal ligaments. These kinds of pathological developments interfere with the intraforaminal ligaments and fatty tissues and obstruct the root’s mechanical movement or increase friction within the root foramen, causing pain. Any kind of foraminotomy affects the ligamentous structures and is believed to be responsible for postoperative pain.The detailed anatomy of the EFLs in the thoracic and lumbarregions has been described systematically. However, tillnow, only limited information was found on cervical EFLs.Sunderland who reported that only the fourth, fifth, and sixth cervicalspinal nerves have a strong attachment to the vertebral column,and this is only to the gutter of the vertebral transverseprocess. They think the fiber attachment has role in protecting against distraction injury of nerve root. Moreover, he said that the neural structures and theircoverings are not attached to the wall of the IVF.Herzberg et al performed an anatomic studyon the brachial plexus roots and concluded that, for the C5, C6, C7 spinal nerves, there seems to be a genuine posterosuperiorligament, semiconic in shape, which arises on the inferiorborder of the cranial transverse process and on the anterioredge of the intertransversary posteriors. They describedthere is no means of such fi xation on the level C8 and Tl.Kraan et al reported that the EFLsconsist of a ventral and dorsal part, and the ventral and dorsalEFLs consist of a superior and inferior part in which the inferiorventral and dorsal ligaments are attached to each other.From the second cervical to the first thoracic spinal nerve,the EFLs consist of a ventral and dorsal superior and inferior part. The ventral superior EFLs originate from the anterior tubercle of the transverse process. It inserts on the posterior tubercle of the transverse process. The ventral side of this ligament is attached to the spinal nerves. The dorsal superior EFL attaches the nerve dorsally and originates of the dorsal part of the transverse process. It inserts on the epineuriumof the spinal nerves.According to the direction of ligaments, they hypothesize that the mechanical function of the extraforaminal cervical ligaments is to reduce longitudinal tension of the nerves.When moving the cervical spinal nerves in ventral and dorsal directions, the EFLs protect the spinal nerves from being pushed against the bony superior and inferior transverse process.The described ligaments seem to protect against noxious stimuli rather than being the cause of any form of neuralgia.At present, no available research data are related to the cervical intervertebral foramen ligaments. Any causal relation between the presence of the described ligaments and neuralgia is speculative which still existesbig controversy.In conclusion, cervical intervertebral foramina ligaments have important clinical significance. It is necessary to know detailed knowledge of the extraforaminalregion to better understand the role of the EFLs in the mechanics and the biomechanics in relation to the physiological and pathological loads on the cervical spinal nerves. The purpose of this study was to elucidate the anatomy and the clinical significance of these ligaments. Our research is divided into the following four parts:Chapter 1 The morphology and clinical significance of the extraforaminal ligaments at the cervical levelObjective:To identify and describe the extraforaminal ligaments (EFLs) in relation to the area of the cervical intervertebral foraminaand to evaluate their clinical significance.Method:Foraminal anatomy was studied in 6 previously prepared whole cadaverswith no evidence of previousspinal surgery (all the samples were provided by the Southern Medical University Department of Anatomy). Regional vascular injections were performed inthe cadavers using colored latex. All specimens showed noevidence of spinal pathology, such as deformities, arthritic orrheumatic conditions, degenerative disorders, and traumas, involving or disrupting the extraforaminal structures. The dissection was performed by approaching the IVFfrom the lateral side on both sides. The spinal nerve rootswithin the fascia were identified and followed to their respectivelVFs by meticulously removing the overlying remnantsof the muscle and the fascia. Using a surgicalmicroscope, the loose connectivetissue around the IVF was removed, with care taken topreserve any tough ligamentous structures encountered in thisprocess. The various EFLs were outlined and identified fromthe C1-C2 IVF to the C7-T1 IVF. At each level, the relationshipwith the spinal nerve and other surrounding structures ofthe IVF was photographically documented.At all levels, the distribution, morphology, origin, insertion,and the spatial orientation of the ligamentous structureswere determined. In addition, the length and width,or diameter and thickness of the ligamentous structureswere measured with a millimeter caliper (accurate to 0.01mm) under the surgical microscope.Measurement data were statistically processed by using SPSS20.0 software, The measurement data were expressed in theform of (x±s, mm). The comparision of the right side and left side of the measured value and the number of the EFLs was tested by independent samples t test and the values in different segments were performed factorial design variance analysis. The thickness or diameter and number of the EFLs in different segmentscompared with each other by the test LSD-t, P<0.05 said the difference was statistically significant.Results:The EFLs could be found from the second cervical to thefirst thoracic spinal nerve. These ligaments could be divided into 2types:radiating ligaments, all of the radiating ligaments terminatedoutside the external pole of the ganglion where they becamethe outer part of the periradicular sheath of the nerve.From the C1-C2 IVF to the C7-T1 IVF, the radiating ligamentsof the spinal nerves were bilaterally visible at all levels. The radiating ligaments anchored the spinal nerves radiatedto the transverse processes and the wall of the IVF, which consistof superior, inferior, posterior, and anterior ligamentousattachments.The occurrencerate of different types of the radiating ligaments of IVF is asfollows:superior (24.7%), inferior (61.5%), anterior (7.5%),and posterior (6.3%).Almost all of the spatial orientation of the radiatingligaments is from mediocranial to laterocaudal, and theorientation of the inferior radiating ligaments is in generalparallel to the cervical spinal nerves. Most of the radiatingligaments pulled the cervical spinal nerves toward the spinalcord to resist the lateral traction on the spinal nervewith topographic variations between subjects and betweenlevels.The radiating ligaments are particularly developed at the levelof C5-C6 IVF, followed by C4-C5, and then C6-C7 IVF; Transforaminal ligaments (TFLs), which originated fromthe anteroinferior margin of cranial transverse process and insertsin the superior margin of the anterior tubercle of caudal transverseprocess crossing the spinal nerve ventrally.The number of the TFLs was signifi cantly different betweenindividuals. Some specimens contained up to 7 ligaments,but some others had none. According to our observations, asingle IVF always contained no more than 1 TFL,Conclusions:Between the cervical spinal nerves and nearbystructures, there are 2 types of the EFLs. The radiating ligamentsmay serve as a protective mechanism against traction and play animportant role in the positioning of the nerves in the intervertebralforamen. However, in all probability, the transforaminal ligamentsmay be the underlying cause of the cervical radiculopathy.Chapter 2 The morphology and clinical significance of intraforaminal ligaments at the cervical LevelObjective:To identify and describe the intraforaminal ligaments (IFLs) in relation to the area of the cervical intervertebral foraminaand to evaluate their clinical significance.Method:Foraminal anatomy was studied in 6 previously prepared,whole cadavers with no evidence of previousspinal surgery. Regional vascular injections were performed inthe cadavers using colored latex. All specimens showed noevidence of spinal pathology, such as deformities, arthritic orrheumatic conditions, degenerative disorders, and traumas, involving or disrupting the extraforaminal structures. The vertebral canal was dividedto expose the dural sac and the spinal nerve roots, and the spinalcord was removed. The morphology, quantity, and attachment of theintraforaminal ligaments in the cervical region wereobserved.The dissection was performed by approaching the IVFfrom the inside on both sides. Using surgicalmicroscope, the loose connectivetissue around the IVF was removed, with care taken topreserve any tough ligamentous structures encountered in thisprocess.Results:The intraforaminal ligaments are present within the intervertebral foraminaof each cervical segment, connected the nerve root radially to the wall of the vertebral foramen. The dissections showed four distinct bands extending radially from the nerve root sleeve.Cervical intraforaminal ligaments appeared a more constantoccurrence rate, whichwere divided into two parts:entrance area and the central district. Entrance area ligaments can be divided into four parts, respectively connected the nerve rootsto the the facet joint capsule,superior margin of the caudal pedicle, inferiormargin of the crania pedicle pedicle edge as well as theintervertebral disc.Entrance area ligament is surrounded by membranous structure packages, open the membrane is a funicular fibrous tissue.Central districtintraforarninal ligament were more slender fibrous tissue, interwoven with net around the nerve root, loose adhere to the nerve root and blood vessel walls of fat clearance. The quantity of these ligament is more, and it is difficult to statistics.In comparison, the intraforaminal ligaments within the C2-C4 IVFwere looser slender and fewer than that of C4-C7 IVF.Conclusion:In cervical intervertebral foramen entrance area and central area, the nerve roots are surrounded by intraforaminal ligaments, which may act in conjunction with thedura and periosteum to protect the nerve roots mechanically.The intraforaminal ligaments do not have any ability to resist this stretching. Due to their being fine and easily snapped, the intraforamina lligaments’ purpose is to preventthenerve root from touchingits surroundings and enable electrophysiological transmissions, CSF flow, and blood circulation. The pain and neurological deficits patients experience following surgery or degenerative diseases can be caused by damage to these intraforaminal ligaments. Surgeons should bear in mind that there are fragile ligaments around the nerve root besides the better-known transforaminal ligaments.Chapter 3 Biomechanical study on the fixation effect of the cervical extraforaminal ligaments on the nerve rootObjective:From a biomechanical perspective to investigate the fixed effect of the cervical extraforaminal ligaments on brachial plexus root and the difference between and different nerve roots.Methods:A total of 10 healthy adult cadavers that were fixed in 10%formalin were used. After dissecting the postvertebral muscles, the posterior laminaes at the level of C5, C7 or C6, C8 were removed to expose the posterior spinal nerve root inside the spinal canal. Locating pin was placed on the bony structure around the intervertebral foramen and nerve root, and then through the pulley to connect the nerve root to the tray. Weight load was loaded on nerve root gradually (50 g weight was one by one joined in the pallet, a total of 60).At the end of the experiment, we selectively cut off part of EFLs to observe the displacement changes of the nerve roots. The displacement change locating pin head was captured by Canon EOS 50 D digital camera. Put the image into computer, using Adobe Photoshop CS6 for accurate measurement.The result were put into 20.0 statistics software SPSS to calculate the displacement rate of every segment of nerve root. The displacement rate of the spinal nerve inside and outside the spinal canal was tested by the paired t test. The displacement rate of C5, C6, C7, C8 nerve root inside the spinal canal was performed bvariance analysis, P<0.05 was considered statistically significant.Results:The displacement of C5, C6, C7, C8 nerve root increased with increasing traction load. The displacement rate of the spinal nerve root inside the spinal canal was smaller than that of the outside the intervertebral foramen (paired t test, P<0.05). Within a certain load range, the EFLs could absorb some pulling loads on thenerve root, and the load range of C5 nerve root was the max. At last, cutting off radiate ligament, especially the inferior radiating ligaments,displacement variation of the nerve root was obvious. However,when cut off the EFLs, the displacement of the nerve root did not change significantly.Conclusions:Cervical extraforaminal radial ligament, especially the inferior radiating ligament could convey traction to the disc and fibrous capsuleof the cervical vertebrae, and hence distracts tensile forcesfrom the intraforaminal nerve roots.These radiating ligaments form a first line of defence toprotect the spinal nerve roots against traction. The protective effect of the radiating ligaments for C5 nerve root is thebest, which probably accounts for the low frequency of avulsion of C5 spinal nerves. The protective effect of the cervical TFLs on the nerve root is not obvious.Chapter 4 A comparative study of anatomy and 3D-FIESTA sequences for the extraforaminal ligaments in cervical intervertebral foramenObjective:Based on thegold standard results of the autopsy dissection imaging to evaluate the capabilitie of MR3D-FIESTA sequencefor scaning the extraforaminal ligaments of cervical spine.Methods:Divided into three parts, the first part:A total of 5 adult cervical embalmed cadaverswith no evidence of previous spinal surgery (all the samples were provided by the Southern Medical University Department of Anatomy). Regional vascular injections were performed in the cadavers using colored latex. All specimens showed no evidence of spinal pathology, such as deformities, arthritic or rheumatic conditions, degenerative disorders, and traumas, involving or disrupting the extraforaminal structures. The specimens were numbered before performing MRI. The EFLs C4-T1 intervertebral foramina were identified in the MR images by a radiologist who had mastered the knowledge of cervical intervertebral foramen ligamentous structure.The results were recorded in the cervical model. The second part:After the specimen scanning, the dissection was performed by approaching the C4-TlIVFfrom the lateral side on both sides. The spinal nerve roots within the fascia were identified and followed to their respective FVFs by meticulously removing the overlying remnants of the muscle and the fascia. Using a surgical microscope, the loose connective tissue around the IVF was removed, with care taken to preserve any tough ligamentous structures encountered in this process. At each level, the relationship with the spinal nerve and other surrounding structures of the IVF was photographically documented. At all levels, the distribution, morphology, origin, insertion, and the spatial orientation of the ligamentous structures were determined. The results were also recorded in the modlel. The third partUsing the gold standard of anatomy results to evaluatethe MR 3D-FIESTA sequence scans of the anatomic specimens. Determine the Sensitivity, specificity, positive predictive value, negative predictive value and accuracy.Results:The occurrence rate of the TFLsin C4-T1 intervertebral foramina is 50%. In the MR3D-FIESTAsequence,the radiating ligaments showed high density signal, which was the same as the nerve roots. However, the TFLs showed a low density signal. In the MR 3D-FIESTA sequence scanning images, the ability of a trainedradiologist to identify the cervical TFLs are as follows:specificity=91.7%, sensitivity=35.3%, positive predictive value= 75%, negative predictive value= 66.7%, accuracy= 68.3%.Conclusion:Compared with other cervical segments, the occurrence rate of the TFLs in the C4-T1 intervertebral foramina is higher. MR3D-FIESTA sequences can provide very good resolution, and aslo can clearly show the EFLs in cervical intervertebral foramen, which has very high clinical value, In the MR 3D-FIESTA sequence scanning images, if a trained radiologist identifies a TFL, there isan70% chance that one is present, and if a trained radiologist does not identify a TFL in an intervertebral foramen, there remains a 30% chance that one is present. |
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