| Part 1 Anatomic Observation and Electrophysiological Study of Lumbosacral Nerve Roots of SD RatsIntroductionSacral fractures account for 20%to 30%of pelvic fractures,and 22%to 60%of them are associated with neurological symptoms.When the sacrum is subjected to strong violence,it is easy to fracture,resulting in deformation and shrinkage of the sacral foramina,injury of the sacral nerve and corresponding dysfunction,which is the main cause of late disability.At present,there are still great differences in the treatment of sacrum fracture combined with nerve injury.How to evaluate nerve injury and recovery by fracture degree,whether nerve decompression is needed,when decompression and whether decompression of old injury is effective are controversial.Therefore,to study the mechanism of sacral nerve forced injury caused by sacral fracture and the relationship between nerve decompression and nerve function(sensation,movement,defecation and urination)has important clinical significance for determining surgical indications and selecting surgical timing.Anatomical studies have shown that the sacral plexus consists of the lumbosacral trunk(L4,5)and the anterior ramus of all the sacral nerves and the caudate nerves.The sciatic nerve consists of L4,5,S1?3 and is the largest nerve in the body.The pudendal nerve comes from the pudendal plexus,and the nerve fibers are composed of the anterior ramus of sacral 2,3 and 4 nerves,including many parasympathetic nerve fibers.The nerve injury caused by sacrum fracture is mainly sciatic nerve(S1)and pudendal nerve(S2-4).Therefore,we targeted the sciatic nerve and pudendal nerve.The sciatic nerve can reflect the sensory motor condition of the lower limbs,and the pudendal nerve is used to reflect the changes of the function of defecation and urination.There are few studies on sacrum fractures,especially those associated with nerve injury,mainly due to the difficulty in conducting in vivo studies,especially in humans.Based on the limitations of in vivo experiments,we considered to construct an effective animal model of lumbosacral nerve root compression injury to study the functional changes of nerve roots under different degrees of compression.In the study of nerve injury,the rat nerve injury model is a widely used experimental model.Various methods have been reported in the literature to prepare this kind of injury model,and the establishment of the rat nerve root compression injury model is still considered to be the most commonly used and the most reliable experimental model in the study of nerve injury.With the continuous progress of electrophysiology technology,electrophysiology not only provides effective judgment for the scope and degree of peripheral nerve injury,but also can determine the repair degree of peripheral nerve.We dissected the lumbosacral nerve roots in rats to determine the main composition and shape characteristics of the lumbosacral nerve roots,and designed and established an animal model of lumbosacral nerve root compression injury caused by sacrum fracture,so as to study the relationship between the lumbosacral nerve root compression injury and nerve compression and nerve function.The electrophysiological test of nerve root compression injury in rats was designed and performed to observe the changes of nerve function under different degrees of compression.Methods20 adult SD rats(Sprague Dawley),half male and half female,aged 9 weeks and weighing 250-300g,were selected.The rats were anesthetized with 2%pentobarbital and fixed on the animal anatomical table.The posterior median approach of the lumbar spine was taken and the subcutaneous fascia was cut layer by layer to expose and remove the bilateral paraspinal muscles,revealing the t12-s3 segment.The posterior lamina is widely incised into the intervertebral foramen.The L4-S1 nerve roots were completely exposed.The anatomy of the nerve was observed under the operating microscope(x10),and the diameter of the intervertebral foramen,the length and diameter of the nerve root in the spinal canal and the diameter of the spinal nerve formed after the intervertebral foramen were measured with a vernier caliper.The lumbosacral plexus was dissected and the composition of femoral nerve,sciatic nerve and pudendal nerve was observed under the operating microscope(x10).In addition,after anesthesia in rats,fixed in animal anatomy on the stage,laminectomy,previously cut show after the L5 nerve root and sciatic nerve,done by the same experimenter with 10 g,30 g,sterile vascular clamp clip weight of 60 g 3 times,each time clip sciatic nerve for 10 s,three times the interval is 10 s,clip,sham group rats do not do any processing.Electrophysiological tests were performed on days 0,2,7 and 14 after treatment,respectively:nerve conduction velocity,curve area under composite action potential(AUC)and peak of composite action potential.ResultsAnatomical observation of lumbosacral nerve roots in SD rats:the lumbar spine of SD rats was divided into six segments(11-16),and the sacrum was divided into four segments(sl-s4).Four sacral vertebrae fused together to form a whole,and four pairs of sacral nerves were generated from four pairs of intervertebral foramen.Above the sacrum of SD rats is the lumbar 6 vertebra body,and the joints formed by the lumbar 6 vertebra and the sacrum can be partially mobile.The lumbar 6 nerve roots originate from the lumbar 6 vertebra body and the intervertebral foramen of the sacrum,and the lumbar 6 nerve roots are relatively thick(1.01±0.09mm).The femoral nerve and the obturator nerve are composed of 11-14,the sciatic nerve is composed of 14-15,the pudendal nerve is composed of 16-sl,and the caudal nerve trunk is composed of sl-s4.The nerve root of L5 is constant to form the sciatic nerve,and the nerve of L6 is constant to form the pudendal nerve.The length of L5 nerve roots was 3.67±0.15mm,and the length of L6 nerve roots was 3.01±0.22mm.Electrophysiological study of rat model of sciatic nerve compression injury:no significant change of conduction velocity was observed in each group at 0,2,7 and 14 days after compression.There was no significant decrease in the conduction velocity when the two groups were compared.In groups of 30g and 60g,the first action potential time after stimulation was significantly prolonged compared with sham group and 10g group,but no such change was observed in groups of 10g and sham group.The percentage of curve area(AUC)decreased gradually with the increase of time.After lOg compression,stimulate with 3v,2v and 1v,the Peak value increases at 1v and 2v,while 3v decreases.The Peak value was reduced under 3v,2v and 1v stimulation after compression of 30g and 60g,and there was a difference between the groups of 10g,30g and 60g(P<0.05).The 10g group found that the Peak value of 0d-14d of 1v stimulation increased gradually after compression,and the Peak value of 0d-14d of 2v stimulation increased gradually after compressionConclusionAccording to the anatomical study of the lumbosacral nerve roots in SD rats,SD rats,as one of the most commonly used experimental animals,have relatively constant nerve composition of L5 and L6 nerve roots,which are suitable for the study of nerve root compression injury.The L5 and L6 nerve root lengths were suitable for electrophysiological tests with electrodes to assess root injury after compression.The experimental model of nerve root compression injury in SD rats can be used to simulate the nerve root compression injury caused by human sacral fracture.Electrophysiology method is a more accurate and effective method to detect nerve function.The study found that compression of 10g had no significant effect on nerve function loss,but AUC and Peak value of nerve composite action potential increased,especially at 0d.This indicates that abnormal nerve discharge occurs when the compression is mild.Over time,neural function becomes more normal.The loss of nerve function occurred above 30g compression,and the loss of nerve function was more obvious at 60g compression,with no obvious recovery over time.PART2 Histological study of lumbosacral nerve roots compression injury in SD ratsIntroductionAfter sacrum fracture,compression of sacral nerve leads to sacral nerve injury.There are two main mechanisms of nerve compression injury:one is the direct primary nerve injury caused by mechanical compression;The other is that the compression of the nerve causes a blockage in the blood supply to the nerve leading to secondary damage.Mechanical compression injury produces a longitudinal thrust on the nerve trunk,leading to stenosis at the ranvier nodule site and high axial consistency.Under mechanical pressure,Ranfly's nodule and myelin were forced to protrude into the adjacent intertubercular area,and the basal membrane and axonal membrane of myelin schwann cells were torn,leading to the loss of myelin sheath and the formation of a typical interposing phenomenon.When the pressure ACTS on the nerves,compression of nerve section of mechanical deformation,nerve vascular injury,thus further damage nerve in microcirculation,nerve can happen ischemic change,ischemia can make myelin metabolic inhibition,cause demyelinating changes,cause nerve conduction dysfunction,clinical performance for loss reduction or sensory and motor function.The nerve injury caused by mechanical compression is related to the intensity of pressure.Usually,when the pressure intensity is high,the nerve injury is mainly caused by the direct mechanical effect and the indirect biological effect.When the pressure is low,nerve damage is mainly caused by indirect damage effects such as nerve blood supply and nutrient transport barrier.At higher pressures(200-400 MMHG),even for a short period of time,the compression will cause neurological structural changes and dysfunction.So the degree of nerve damage is related to the intensity of the compression.This experiment constructed the lumbosacral nerve root compression injury model of SD rats,designed the nerve root compression injury under different compression forces,and conducted the nerve root histological detection under different time after compression.The subject studied the relationship between different compression degree and the change of nerve function and the degree of injury through the neurohistological method.MethodsHistological Study of nerve root compression injury Rats were divided into four groups:SHAM(sham operation group),10g group,30g group and 60g group,with 24 rats in each group.After 0,2,7 and 14 days after the lumbosacral nerve root compression injury model was prepared,the rats in each group were further dissected for histological analysis after neuroelectrophysiological detection,and the nerves weretaken for histological observation at the corresponding neuroelectrophysiological test points.Each specimen was cut into 9 sections(distal 3,comression 3,and proximal 3),and one tissue section was taken from each part for different staining.Fixed,paraffin-embedded,section-dyed,observed under microscope and collected to computer by digital image acquisition system.Twenty fields of high power fields(HPFs)were taken from each section.Finally,image analysis and scoring were performed by subjects familiar with the pathology experiment but not involved in the study.HE staining was used to observe the rupture of blood vessels,APP staining was used to observe the staining of nerve fibers,and silver staining was used to observe the nerve fiber Spaces and fractures.ResultsObservation of HE staining:nerve fibers in the Sham group were stained uniformly and with good continuity.A small amount of red blood cells were found after 10g compression of the nerve root,and the accumulation of inflammatory cells in the nerve root was observed after 2d.Inflammatory cells were reduced and nerve root edema was observed after 7 days.After 14d,the intracerebral hemorrhage was observed to disappear,and the edema was also reduced.On the 0d after 30g compression,the intracerebral hemorrhage was aggravated compared with 10g.After 2d,intracerebral hemorrhage,inflammatory cell infiltration,and vacuol-like changes in nerve roots were observed.After 7d,intracerebral hemorrhage was reduced,axonal edema was observed,and inflammatory cell infiltration was observed.Both axonal edema and inflammatory cell infiltration were reduced on day 14,but axonal disruption was observed after compression.On the 0d after 60g compression,the intracerebral hemorrhage was serious.The interruption of axonal continuity was observed in 2d,and red blood cells and a large number of inflammatory cells could still be seen in the nerve root at 7d,as well as vacuol-like changes.After 14d,red blood cells and inflammatory cells were reduced,but axonal fracture was obvious.Observation of social-app staining:positive staining in the axons of the hypoapp nerve was observed in all the compression groups after 2d and the positive expression was still observed after 14d.Observation by silver staining:after 10g compression,the axon morphology of nerve root was basically intact,and obvious axon edema was found in 2d.Axonal fracture was observed after 30g compression.The axon of 60g compressed nerve root was seriously injured.On day 0d,there was significant edema.ConclusionThe histology around the nerve fibers can change with different degree and time of injury.Studies show that nerve function is almost unaffected when the degree of compression is low(10g),30g of nerve function begins to be lost,and 60g of nerve function is severely lost The degree of loss of nerve function was positively correlated with the degree of compression.After early decompression,the nerve function of 30g compression was observed to recover 14 days later,while no obvious recovery was observed in the 60g compression group.These results may play an important guiding role in the selection of repair time and prognosis after sciatic nerve injury.This study was limited to the histological study of sciatic nerve injury,and did not further study the treatment scheme after the injury. |
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