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Experimental Study on the Characteristics and Mechanisms of Craniocerebral Injury Caused by the Handgun Bullet Impact on the Helmet-protected Head

Author: HuangYiFeng
Tutor: XuMinHui
School: Third Military Medical University
Course: Neurosurgery
Keywords: brain injuries cognitive function mechanisms gunshot head protectivedevices
CLC: R651.1
Type: Master's thesis
Year: 2012
Downloads: 45
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Abstract


Ⅰ.BackgroundLike the weapons, helmet is the product of the war. And it is renewed with thedevelopment of the weapons, just like the evolution that bronze helmet for cold weapons tobulletproof helmet for bullets. Now the use of modern military helmet has significantlydecreased the incidence rate and mortality of penetrating injury. But the cases of bluntcraniocerebral injury which is caused by the blast-fragments and high-velocity bulletsincreased more and more with the large uses of explosive and high-energy weapons. Theincrement of casualty and nervous system dysfunction because of blunt craniocerebralinjury has aroused the attention of many governments and army. In recent decades, thestudy of blunt craniocerebral injury by corpse head model and mathematical simulation hasbeen developed overseas. They regarded that the characteristics of blunt craniocerebralinjury resembled the traditional craniocerebral injury but the mechanism was differentsubstantially. Although the corpse head model and mathematical simulation have solvedmany problems of biomechanics, physiological, pathological, and biochemical reactionscan’t be observed by corpse head model and craniocerebral injury can’t be observed bymathematical simulation. So the foundation of animal experiment model is significant forthe study of characteristics and mechanisms of blunt craniocerebral injury which is causedby bullets collided with the bulletproof helmet.Ⅱ.ObjectiveThe first objective of our experiments is to clear the characteristics of bluntcraniocerebral injury after bullet collision with the helmet, as follows:①earlyphysiological response stage after injury;②Early change of electroencephalogram (EEG)after injury;③Early general, microscopically, and ultra-micro pathological change of craniocerebral injury after injury;④Early change of biomarkers in serum and cerebralspinal fluid (CSF) after injury.Second, we study the major mechanism of blunt craniocerebral injury caused bybullets collided with the helmet, by testing the dynamic transfiguration of bulletproofhelmet and change of intracranial pressure caused by stress.Third, we wish to offer evidences for the prophylaxis, treatment, and prognosis ofblunt craniocerebral injury caused by bullets collided with the helmet.Ⅲ.MethodIn the first part of our experiments, we take the young-adult long-white pigs as studyobjects, aramid bulletproof helmet as defending material, foam interleaver as buffermaterial within pig head and bulletproof helmet In injury group there are three velocities of9mm plumbum core bullets as injury member, including280m/s(low speed, n=3)、360m/s(normal speed, n=9)、420m/s(high speed, n=3); In control group (n=5) there are9mm unarmed bullet as injury member. To establish an animal model, we aimed at themidpoint of march between brow and coping of porcine head and the injury distance is10m.After injury, we investigated the physiological change (blood pressure, heart rate, breathfrequency) change of electroencephalogram (frequency, amplitude, chart power),changeof organs (skin, skull, and brain tissue), microscopical change of tissues(pallium,hippocampus) and ultra-micro pathological change of tissues(hippocampus), expression ofbiomarkers (NSE、MBP、S-100β、αII-spectrin).We also evaluated the score of AIS.In the second part, we established animal model of active-avoidance response. And wetook propofol for a short-time narcosis and fixed the pigs. until the pigs were quiet, we tookthe same injury way as the part one apart used9mm plumbum core bullets of360m/s(normal speed, n=5) and control group (n=5) with9mm unarmed bullets.After thatwe observed the function change of normal conditions, movement and active-avoidanceresponse.In the third part, we took the pigs fit with intracranial pressure sensor as study object.In injury group there are three velocities of9mm plumbum bullets as injury member,including280m/s (low speed, n=6),360m/s (normal speed, n=6),420m/s (high speed, n=6);in control group (n=5) there are9mm non-warhead bullets as injury member. the pigs wereinjuried as the part one, then intracranial pressure wave was detected, and its peak value was measured.In additional, we test the bulletproof helmet dynamic transfigurationimpacted by three velocities of9mm plumbum core bullets including280m/s(low speed,n=3),360m/s(normal speed, n=3),420m/s(high speed, n=3), by using high speedphotography.Then combined the bulletproof helmet vestigial transfiguration of part oneand intracranial pressure characteristics, we discussed the injury mechanisms ofcraniocerebral injury.Ⅳ.Result1. Physiological response: In injury group, the blood pressure decreased, heart rate andbreath frequency increased after injured by three different velocities of bullets, especiallythe contraction pressure was decreased significantly at the moment of injured and the extentwas positive correlated with bullet speed. And the change of control group is not notable.2. Change of EEG: In normal speed group, the frequency of EEG was decreased3minafter injury. But the amplitude was increased, power of δ、θ、α、β wave bands wereincreased, especially the θ wave band(P<0.05).15-30min after injury, the frequency ofEEG was decreased lightly, power of four wave bands recovered to the level of uninjuredgradually.3. Change of general morphology: In injury groups, there was a pale area surroundedby a flush circle in the skin of animals head after injury. The skin injury was severer withthe increase of bullet speed. The subcutaneous parenchyma was bruised and bleeding3hafter injury. The degree of subcutaneous parenchyma injury was increased along with shootspeed. skull fracture appeared in normal speed group(3/9) and high speed group(1/3),mainly showed linearity fracture and splintered fracture individually. Brain injuries wereappeared in low speed group(2/3), normal speed group(9/9), and high speed group(3/3),which presented local brain impact injury and counterblow that caused subdural spacebleeding, subarachnoid space bleeding, intracerebral hemorrhage, and pituitary hyperemiaand bleeding, and the impact injury was severer than counterblow. The AIS score of were:1.67±0.58(low speed group),2.44±0.73(normal speed group),3.67±0.58(high speedgroup), and the high speed group is statistic significant(P<0.05)than the other groups.4. Histological and pathological change: microscopic observations of pallium was thatsubarachnoid space bleeding was found in area of impact and counterblow area while brainbleeding was not found in normal speed group and high speed group. Pycnosis denaturalization and necrotic changes were found in pallium neurons of the area of impactand counterblow area, and the impact injury was severer than bump. The degree of palliuminjury was increased along with shoot speed. The individual nucleolus, medullated nervefiber, nonmyelinated nerve fiber of hippocamp cortical neurons was found pycnosisdenaturalization in injury group. The degree of hippocamp cortical neurons injury wasincreased along with shoot speed.5.Biomarkers of brain injury: In injury groups NSE、MBP、S-100B、αII-spectrin ofCSF were increased notable along with shoot speed3h after injury. Apart from the S-100B,all the other biomarkers in CSF3h after injury in normal speed grop were statisticsignificant(P<0.05)compared with pre-injury and the control group3h after injury. Ininjury groups, the concentration of NSE、MBP in plasma was increased obviously as timewent by and with shoot speed,while S-100B increased lightly. And the concentration ofNSE3h post-injury in normal speed grop was significant difference compared withpre-injury and the control group3h after injury(P<0.05).6. Function and ethology change: It’s not found with coma in normal speed group earlybut fantod, bluntness and anorexia. Some pigs were found vomiting(1/5), amyostasia(3/5).Decreased extremities myodynamia, limited joint activity, staggering, slippery arise werefound at the moment after injury and recovered within30min-2h. Active avoidanceresponse was decreased in different degree3h after injury, which implied the memorydysfunction.But in control group it’s not found with function and ethology handicap asdescription.7. Test of biomechanics: The wave of intracranial pressure was composed of graduallydecreased peak value and short duration stress waves. And the peak value of intracranialpressure was positive correlated with impact power and negative correlated with distance ofimpact distance.8. Transmogrification of bulletproof helmet: In the animal experiment, thetransfiguration of bulletproof helmet was severer along with higher shoot speed. The bulletaperture area, convexity area, convexity height in different group was statistically different(P<0.05)when used pair wise comparison. The result of high speed photograph wasindicated that the convexity height in most dynamic transfiguration was more notable thanin final transfiguration(P<0.05),and the convexity height in final transfiguration was more notable than in vestigial transfiguration of the animal experimen(tP<0.05). Most dynamictransfiguration in bulletproof helmet was the key reason of craniocerebral injury. The AISscore and the maximum transfiguration had the relationship of logarithm when analyzedusing function mathematics model.Ⅴ.Conclusion1. The specialties of blunt craniocerebral injury caused by9mm plumbum core bulletsimpacted on the bulletproof helmet were as follows:(1) Localized impact injury and counterblow are the major characteristics of bluntcraniocerebral injury, and impact injury is severer than counterblow and positive correlatedwith the impact power.(2)The hippocamp also can be acute injured. Its nerve cells were founddenaturalization and were positive correlated with impact power.(3) The craniocerebral injury may cause the obstacle of function ethology, such asanorexia、vomiting, amyostasia, Motor dysfunction, cognize dysfunction.2. The mechanisms of blunt craniocerebral injury caused by9mm plumbum corebullets impacted on the bulletproof helmet were as follows:The bullet shot on bulletproof helmet caused instant maximum transfiguration and theimpact of short-time, high-speed and low-mass affected on brain caused the stress. And thestress passed through the brain tissue and asymmetry distributed in trans-brain, whichcaused the strain of brain tissue. It may be the major mechanism of the craniocerebralinjury.

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