步枪弹击中背部防弹衣后脊柱脊髓钝性损伤的生物力学机制

Biomechanical mechanism of blunt spinal cord trauma after rifle bullets hitting back of body armor

目的 探讨步枪弹击中防弹衣后产生的压力波在脊柱区与颅内的传导规律,以及不同速度的步枪弹所致的压力及加速度（瞬时位移）与击中防弹衣后脊柱脊髓钝性损伤的关系.方法 雄性长白猪25头,其中20头按随机数字表法分为高速组、中速组、低速组、对照组,每组5头.采用防弹衣被击中后钝性损伤动物模型,根据肌力判定标准（10分法）给双侧后肢评分以明确脊髓损伤程度.另5头用于测量颈动脉压力、颅内压以及T10处加速度,并对损伤程度及各指标进行回归分析.结果 高速组中3头双侧后肢评分为5分,2头为7分;中速组中l头为8分,其余4头未见运动功能障碍;低速组、对照组均未出现运动功能障碍.高速组、中速组、低速组颅内压分别为（98.7±36.8） kPa、（41.1 ±7.8）kPa、（38.9±8.7） kPa（P ＜0.05）;T10处加速度分别为（3 853.4±806.0）g、（2 501.3 ±226.9）g、（1 949.0±118.4） g（P ＜0.01）.回归分析显示,压力与加速度呈正相关（R2 =0.85,P ＜0.01）,速度与脊柱区压力呈正相关（R2 =0.56,P＜0.01）,速度与脊柱区加速度呈正相关（R2=0.70,P＜0.01）,脊髓损伤程度与加速度呈线性相关（F=137.05,R2=0.94,P＜0.01）.结论 步枪弹击中背部防弹衣时在脊柱区和颅内可产生压力波和加速度,最终导致脊柱脊髓钝性损伤.

Objective To investigate the transmission pattern of the pressure wave generated by rifle bullets impacting the back of the body armor and the relationship of spinal injury with pressure and acceleration generated by the bullets with different velocities.Methods Twenty male pigs were randomly divided into high velocity group,middle velocity group,low velocity group and control group,with 5 pigs per group.Behind armor blunt trauma animal models were applied.Degree of spinal cord injury was evaluated by the variation of the muscle strength.Another 5 male pigs were used for the examination of pressure of common carotid artery,intracranial pressure and acceleration at T10 vertebrae.The results were analyzed through regression.Results Bilateral hindlimb score was 5 points in 3 pigs and 7 points in 7 pigs in high velocity group.Except for 1 pig of 8 points in bilateral hindlimb score,the remained presented normal motor function in middle velocity group.There was no motor dysfunction in low velocity and control groups.High,middle and low velocity groups showed intracranial pressure of （98.7 ±36.8） kPa,（41.1 ± 7.8） kPa,and （38.9 ± 8.7） kPa respectively （P 〈 0.05） and acceleration at T10 of （3 853.4 ± 806.0） g,（2 501.3 ± 226.9） g,and （1 949.0 ± 118.4） g respectively（P 〈 0.01）.Logistic analysis revealed positive correlation of pressure with acceleration（R2 =0.85,P 〈0.01）,positive correlation of acceleration with pressure at spinal cord （R2 =0.56,P〈0.01）,positive correlation of velocity with acceleration at spinal cord （R2 =0.70,P 〈 0.01）,and linear correlation of injury severity with acceleration （F =137.05,R2 =0.94,P 〈 0.01）.Conclusion Rifle bullet impacting the back of body armor generates pressure wave and acceleration which leads to blunt trauma of the spinal cord.