【作者】 赵兴；

【导师】 范顺武；

【作者基本信息】 浙江大学 ， 外科学， 2010， 博士

【摘要】 研究背景：椎体后缘骨折块(Retropulsed bone fragment, RBF)形成是胸腰椎爆裂性骨折(Thoracolumbar burst fracture, TLBF)特征性的影像学表现,往往发生在椎体后上缘。它对判断神经损伤、椎管占位、骨折稳定性、后纵韧带损伤等具有重要意义；也是决定胸腰椎骨折是否需要手术和如何手术的重要决定因素。目前椎体RBF形成的确切机制不清。有研究认为,暴力作用导致终板骨折,椎间盘突入椎体,椎体内压力增高,随后椎体爆裂；同时暴力使椎弓根基底部应力集中区骨折,并产生沿椎弓根传递的剪力,对椎体产生切入效果,导致椎体RBF形成和移位。此外对上下终板生物力学的研究发现,上终板更容易骨折,解释了骨折块总是位于椎体后上缘的原因。然而,上述理论存在一个共同缺陷,即：忽视了椎体后缘一个明显骨质缺省区(椎基静脉孔)的存在对椎体RBF形成的影响。当前,国内解剖学教材并未对椎基静脉孔(Basivertebral foramen, BF)这一特殊的解剖结构进行描述；国外虽偶有文献报道,但也只是简单提及其大致位置,并未关注BF的形态特征及与椎体RBF形成的关系。研究目的：1、明确胸腰椎(T12、L1、L2和L3)BF的形态特征,包括：物理参数(宽、深、高绝对值和相对值)、在椎体中的位置、不同椎体BF的差异、BF的影响因素。2、通过临床和实验研究,明确BF与TLBF时RBF形成的关系。研究方法：1、对36例健康成人胸腰椎(T12、L1、L2和L3)进行螺旋CT薄层扫描、对每个节段单独进行正中矢状位和横断位重建。在CT横断位和正中矢状位重建图像上,测量BF宽(BFW)、深(BFD)、高(BFH)的绝对值,计算同一测量平面上BF相对于椎体宽、深、高的相对值(BFWr、BFDr、BFHr);测量BF距椎体左右边缘和上下终板的距离,观察BF在椎体中的确切位置。应用SPSS 11.5统计学软件对上述数据进行统计学分析,应用配对设计t检验分析同一个节段中BF距椎体左右边缘和上下终板的距离均数值的差异；应用单因素方差分析检验不同节段之间BFW、BFWr、BFD、BFDr、BFH、BFHr的差异。利用单因素方差分析检验性别与各个节段BFW、BFWr、BFD、BFDr、BFH、BFHr的相关性；利用Pearson检验分析年龄、体重指数与各个节段BFW、BFWr、BFD、BFDr、BFH、BFHr的相关性。P<0.05时具有统计学意义。2、在36例健康成人胸腰椎(T12、L1、L2和L3)的正中矢状位重建图像上测量BFSL (BF后上角距上终板后角的距离)和BFSW(由BF顶点向上终板作垂线,上终板后角距该垂线的距离)。应用配对设计t检验分析相邻节段BFSL平均值与中间椎体BFSL的关系；应用配对设计t检验分析相邻节段BFSW平均值与中间椎体BFSW的关系。P<0.05时差异具有统计学意义。收集临床胸腰椎爆裂性骨折患者50例,其中L1骨折29例、L2骨折21例。对骨折进行螺旋CT薄层扫描、三维重建,在CT正中矢状位重建图像上,测量骨折上下相邻椎体BFSL和BFSW测量骨折椎体RBF的参数,包括RBFL(骨折块的椎管侧长度)和RBFW(由骨折块前下角向骨折块上边做垂线,骨折块后上角距该垂线的距离)。利用相邻椎体BFSL和BFSW平均值分别代表骨折椎体的BFSL和BFSW,应用配对设计t检验分析其与骨折块RBFL、RBFW的差异,从而推测RBF形成与BF的关系。3、冻存胸腰椎节段标本9例(T12-L2),应用累积撞击模型复制L1爆裂性骨折,骨折前后应用螺旋CT薄层扫描、三维重建,测量和分析骨折前BFSL、BFSW与骨折后RBFL、RBFW的差异,推测RBF形成与BF的关系。在冰冻状态下对标本进行解剖,肉眼观察RBF与BF的关系。观察撞击后上下终板的骨折情况和后纵韧带损伤等。研究结果：1、CT横断位和矢状位重建图像上,81%BF表现为三角形或梯形；6%BF内部出现骨性间隔。相同测量节段的BFW、BFD和BFH最大值接近或超过同一测量平面椎体宽、深和高的1／3,平均宽、深和高接近或超过同一测量平面椎体的25%。在T12和L3,BF距椎体两端距离无统计学差异(P>0.05)；而在L1和L2,BF距椎体两边的距离具有统计学差异(P<0.05)。在T12、L1、L2和L3中,BF距上下终板的距离均存在统计学差异(P<0.05),更靠近于上终板。在不同测量节段,BFW、BFH、BFWr、BFHr的均数值均无统计学差异(P>0.05)；而BFD和BFDr在L3更大,其中,与T12、L1、L2绝对值比较均有统计学差异,与L1、L2的相对值比较存在统计学差异。性别与BF各测量参数无相关性；年龄与L1BFHr和L2BFHr相关；而体重指数与LIBFH、L2BFW、L3BFH、L3BFHr相关。2、对36例健康成人的BFSL和BFSW进行测量和统计学分析,结果显示：相邻上下椎体BFSL均数值与中间椎体BFSL无统计学差异(P>0.05)；相邻上下椎体BFSW均数值与中间椎体BFSW无统计学差异(P>0.05)。对29例L1爆裂骨折进行测量和统计学分析,结果显示：T12和L2的BFSL均数值与L1的RBFL无统计学差异(P>0.05)；T12和L2的BFSW均数值与L1的RBFW无统计学差异(P>0.05)。对21例L2爆裂骨折进行测量和统计学分析,结果显示：L1和L3的BFSL均数值与L2的RBFL无统计学差异(P>0.05)；L1和L3的BFSW均数值大于L2的RBFW,具有统计学差异(P<0.05)3、9例胸腰段标本,通过累积撞击模型成功复制骨折8例,撞击次数2-6次,平均3.75次。对比和测量撞击前后标本的正中矢状位CT重建图像显示,8例标本椎体后缘骨折块形成均与BF相关,骨折线通过BF；统计学分析显示：撞击后RBFL与撞击前BFSL无统计学差异(P>0.05)；撞击后RBFW小于撞击前BFSW,差异具有统计学意义(P<0.05)。4例标本出现不同程度的PLL损伤,损伤部位主要位于BF边缘。8例标本均出现不同程度的上终板损伤,2例标本出现下终板损伤。标本经正中矢状位切开后显示,6例标本椎体中出现突入的髓核或软骨终板,椎体骨折块的骨折线经过BF上边。研究结论：1、36例健康成人144个椎体后缘均存在BF。在CT横断位和矢状位上,BF最常见的形态结构为三角形或梯形。少数BF内部存在骨性间隔。CT横断位上,T12和L3的BF更倾向位于椎体的中央区域；而L1和L2的BF稍偏向于椎体左侧。CT矢状位上,T12、L1、L2和L3椎体的BF均更靠近上终板。在不同个体,BF的物理参数存在较大差异,BFW、BFD和BFH的最大值超过同一测量平面上椎体宽、深和高的1／3,平均宽、深和高接近或超过椎体的25%。BFW、BFWr、BFH、BFHr的均数值在T12、L1、L2和L3中无差异；而L3椎体具有更大的BFD。性别与BFW、BFWr、BFD、BFDr、BFH、BFHr无相关性。2、健康成人中,上下相邻椎体BFSL平均值与中间椎体BFSL无差异、上下相邻椎体BFSW平均值与中间椎体BFSW无差异。L1爆裂性骨折时,骨折上下相邻椎体BFSL平均值与骨折椎体RBFL无差异,骨折上下相邻椎体BFSW平均值与骨折椎体RBFW无差异,推测椎体BF与椎体RBF形成相关。L2爆裂性骨折时,骨折上下相邻椎体BFSL平均值与骨折椎体RBFL无差异,骨折上下相邻椎体BFSW平均值大于骨折椎体RBFW,推测椎体BF与椎体RBF形成相关。3、实验模拟的骨折标本中,RBF形成与BF密切相关。累积撞击方案是模拟胸腰椎爆裂骨折的有效方法。更多还原

【Abstract】 BackgroundThe retropulsed bone fragment (RBF) is the characteristic of the thoracolumbar burst fracture (TLBF) in axial CT images. It always comes from the posterior superior vertebral body. It is very important to evaluate the neurologic deficit, canal compromise, stability or instability in TLBF, and posterior longitudinal ligament injury. Also, it is one of the indications for the surgery and making a choice for surgical approach in TLBF. The mechanism of the RBF is not absolutely clear. Various studies in the literature have dealt with the issue. Under the axial impact, the endplate in the central portion is failure, allowing the nucleus material to enter the vertebral body, thereby pressurizing it more, squeezing the fat and marrow contents of the vertebral body out of the cancellous bone. When nucleus material enters the vertebral body faster than fat and marrow being expulsed, burst fracture is said to occur. At the same time, the shear force at the facet joints is transmitted through the pedicles to the posterior half of the vertebral body, creating a wedging effect, which dislodges and displaces the bony fragments. Additionally, the biomechanical study of the endplates has demonstrated that comparing with the caudal endplate, the cranial endplate is preferential failure under the same stress. This finding have accounted for the phenomenon that the RBF always originates from the posterior superior vertebral body. However, there is a same defect in these theories, that is an obvious bone default (Basivertebral foramen, BF) in the posterior vertebral body has been ignored. Nowadays, Chinese anatomy textbooks do not even describe this special anatomic structure, and English anatomy textbooks only provided a brief description of the approximate location. The morphological features of the BF and its relevance to the RBF in TLBF are not still clear.Objective1. to observe the morphological features of the BF in T12, L1, L2 and L3,including BF weight (BFW), BF depth (BFD), BF high (BFH), BF relative to the body weight (BFWr), BF relative to the body depth (BFDr), BF relative to the body high (BFHr). the location in the vertebral body, the difference of BF in different levels.2. To certify the relationship between the BF and the RBF in TLBF by clinical and experiment study.Methods1. A total of 36 health adults were underwent multi-slice CT thin slice scans and three-dimensional reconstruction for T12, L1, L2 and L3. In the horizontal and sagittal CT reconstruction images, the BFW, BFD, BFH, BFWr, BFDr and BFHr were measured. The distance between the BF and each side in the horizontal and sagittal CT images were also measured, to investigate the precise location in the body. The correlation between the measured parameters of BF and the gender, age, body mass index (BMI) were analyzed statistically.2.In the midsagittal reconstruction images of 36 health adults (T12, L1, L2 and L3), The BFSL (the distance between the posterior superior corner of BF and posterior corner of cranial endplate) and BFSW (the distance between posterior corner of cranial endplate and perpendicular from the end of BF to the cranial endplate) were measured. The difference between the average of BFSL in upper and lower level and BFSL of middle level was analyzed statistically. The BFSW was analyzed statistically by the same method. A total of 50 TLBF cases,29 cases in L1 and 21 cases in L2. All cases were underwent multi-slice CT thin slice scans and three-dimensional reconstruction. In the midsagittal reconstruction images, the parameters of BF in upper and lower adjacent fracture level were measured, including BFSL and BFSW. In the midsagittal reconstruction images, the parameters of RBF in fracture level were also measured, including RBFL (the length of RBF closed to the canal) and RBFW (the distance between posterior corner of cranial endplate and perpendicular from the anterior inferior corner of RBF to the cranial endplate). The difference between the average of BFSL in upper and lower adjacent fracture level and RBFL was analyzed statistically. Also, the difference between the average of BFSW in upper and lower adjacent fracture level and RBFW was analyzed statistically. By the statistical analysis, the relationship between the BF and RBF was studied.3. A total of 9 frozen samples of thoracolumbar motion segment (T12-L2). An incremental trauma model was applied to reproduce the L1 burst fracture. Before and after fracture, the multi-slice CT thin slice scans and three-dimensional reconstruction was undergone in all samples. The BFSL and BFSW of L1 were measured before fracture, and the RBFL and RBFW of L1 were measured after fracture. The difference between the BFSL and RBFL was analyzed statistically, to investigate the relationship between the BF and RBF. The difference between the BFSW and RBFW was also analyzed statistically for the same purpose. The samples were cut through midsagittal plane to observe the relationship between the BF and RBF by eye.Results1.In the horizontal and sagittal reconstruction images,81% BF was triangular or trapezoid. There was a bone interval within 6% BF. In the same level in 36 cases, the maximum of BFW was approximately 1/3 vertebral body width, which was measured in the same plane as BFW. The maximum of BFD and BFH respectively were also approximately 1/3 vertebral body depth and high. The average BFW, BFD and BFH were approximately 25% vertebral body in the same plane. In T12 and L3, the distance from the BF to right vertebral border was no significant difference than the distance from the BF to left vertebral border (P> 0.05). In the L1 and L2, however, there was statistical difference (P<0.05). In all four levels, the distance from the BF to the cranial endplate was shorter than to the caudal endplate (P<0.05). The mean BFW, BFH. BFWr, BFHr in different levels were no significant difference (P> 0.05). The mean BFD and BFDr in L3, however, were greater than other levels. There was not a correlation between gender and BFW, BFWr, BFD, BFDr, BFH, BFHr. There was a correlation between the age and L1BFHr and L2BFHr,and a correlation between BMI and L1BFH, L2BFW,L3BFH and L3BFHr.2.In all 36 health adults, BFSL and BFSW were measured and statistically analyzed. The mean of BFSL of the upper and lower levels was no significant difference than the BFSL of the middle level (P> 0.05). The mean of BFSW of the upper and lower levels was also no significant difference than the middle level (P> 0.05).In all L1 and L2 TLBF cases, there was no significant difference between the mean of BFSL of upper and lower levels and RBFL in fracture level (P> 0.05). There was also no significant difference between the mean of BFSW of upper and lower levels and RBFW in L1 (P> 0.05). However, the mean of BFSW of upper and lower levels was greater than RBFW in L2 (P<0.05).3. Experimental fracture was reproduced successfully by incremental trauma model in 8 frozen samples. The number of impact was 2-6 times, the average was 3.75 times. By comparing the midsagittal CT images pre- and post-fracture, the RBF was directly related with the BF, and the fracture line of RBF passed through the top border BF. There was no significant difference between the BFSL pre-fracture and the RBFL post-fracture (P>0.05). The BFSW pre-fracture was greater than the RBFW post-fracture (P<0.05). Posterior longitudinal ligament was torn variously in 4 samples. The fracture of cranial endplate was observed in all 8 samples, and only 2 samples showed the fracture in caudal endplate. The samples were cut through midsagittal plane and revealed that the nucleus material or cartilage endplate entered the vertebral body and the fracture line of RBF passed through the top border of BF.Conclusions1. There was a BF in all 144 levels in 36 health adults. In the horizontal and sagittal CT images, the most common appearance of BF was triangular or trapezoid. There was a bone interval within a few BF. The location of BF in T12 and L3 was more central than L1 and L2 in the horizontal CT images, and the BF was closer to the cranial endplate in all four levels in the sagittal CT images. In different individuals, the physical parameters of BF were quite different. The maximum of BFW,BFD and BFH respectively were approximately 1/3 vertebral body width, depth and high. The average BFW, BFD and BFH respectively were approximately 25% vertebral body in the same plane. The mean BFW, BFH, BFWr and BFHr in different levels were no significant difference. The mean BFD and BFDr in L3, however, were greater than other levels. There was not a correlation between gender and BFW, BFWr, BFD, BFDr, BFH, BFHr.2. In health adults, the mean of BFSL of the upper and lower levels was no significant difference than the BFSL of the middle level. The mean of BFSW of the upper and lower levels was no significant difference than the BFSW of the middle level. In 50 TLBF cases, the RBF was closely related to the BF.3. The RBF was closely related to the BF. The incremental trauma model was an effective method to reproduce the experimental fracture, which meet the purpose of this study.更多还原