下颈椎经椎弓根螺钉内固定相关解剖学观察

目的为下颈椎经椎弓根螺钉内固定提供应用解剖学基础及形态学资料。方法应用游标卡尺和量角器对24具成人颈椎干燥标本C3~7椎弓根的高度、宽度、骨性椎管长度、轴线长度、内外侧皮质厚度及轴线夹角进行解剖学测量,并分别计算各节段左右侧椎弓根测量值的均值和标准差,进行统计学分析。结果C3~7椎弓根的椎弓根最窄处截面上下皮质骨高度(PH)和松质骨高度(PSH)分别为4.21mm和7.64mm,宽度分别为3.64mm和5.88mm;轴线长度、骨性椎管长度及侧块部长度分别为15.75mm、32.20mm及8.12mm;最狭窄处内、外侧皮质厚度为0.68mm和1.65mm;椎弓根轴线与矢状线在水平面上的夹角C3:47.12°±3.05°、C4:43.47°±1.49°、C5:40.15±2.58°、C6:38.55°±2.45°、C7:35.16°±2.10°;椎弓根轴线与水平面间夹角C3:8.50°±2.50°、C4:4.83°±1.65°、C5:1.25°±1.45°、C6:-(4.50°±2.50°)、C7:-(8.50°±2.50°)。结论本实验实体测量数据与国内外数据无显著差异,但发现颈椎椎弓根解剖形态个体变异程度较大,术前必须对置钉椎体进行CT、X线片检查,确定适合个体的进钉点、进钉方向、螺钉直径及长度等。颈椎椎弓根螺钉技术仍然是一种相对安全、固定可靠的手术方法。     

下颈椎椎弓根螺钉内固定相关参数的解剖学和影像学测量

目的:测量成人下颈椎椎弓根相关径线,为临床应用下颈椎椎弓根螺钉内固定提供相关解剖参数.方法:成人干燥尸体颈椎C3～C7标本20具,分别用手工和CT测量椎弓根宽度、高度,从横断面CT图像上测量椎弓根的内部宽度、内部高度,从纵断面CT图像上测量椎弓根矢状角.随机在CT窒保存的100例成人患者的颈椎CT图像上测量椎弓根的宽度、自身长度和椎弓根通道全长、椎弓根内倾角.结果:下颈椎标本各节段椎弓根宽度、高度的手工测量值与CT测量值比较无统计学差异(P>0.05),椎弓根宽度小于高度;C3～C6节段CT测量椎弓根内部宽度平均为2.5～2.8mm,椎弓根内部高度平均为2.9～3.0mm,C7椎弓根的内部宽度和高度接近,约4.0mm;下颈椎标本CT测量椎弓根矢状角分别为C3 8.6°,C4 4.6°,C5-1.3.,C6-4.0°,C7-8.2°.100例成人下颈椎CT图像测量椎弓根宽度最小值为3.1mm(C3),最大值为9.3mm(C7),其中>3.5mm者为92.8%;椎弓根自身长度平均为19.1～20.5mm,椎弓根通道全长平均为33.2～35.0mm,椎弓根内倾角平均值C3～C5为43.2°～45.1°,C6为40.8°,C7为37.5°.结论:术前CT测量可为椎弓根准确置钉提供可靠的解剖参数,下颈椎椎弓根一般可接受直径3.5mm的螺钉同定.     

颈椎弓根钉固定的研究进展

脊柱经椎弓根螺钉固定系统由于具有牢靠的三维固定效果，已越来越受到国内外骨科学者青睐。目前此技术已被广泛用于胸腰椎的固定。近10年来，由于颈椎外科的发展及对颈椎局部解剖学不断深入的研究，此技术在颈椎亦得到应用，并取得了良好的临床疗效。本文就颈椎椎弓根的解剖学特点、椎弓根螺钉内固定的优缺点及其临床应用等方面作一综述。1颈椎椎弓根的解剖结构测量颈椎椎弓根结构复杂，其内部形态的三维结构变异较大。不同个体及同一个体不同椎体间都有较大的差异。1.1颈椎椎弓根的径线参数测量包括椎弓根的外径宽度、高度，内径宽度、高度…     

颈椎椎弓根钉内固定研制及置钉准确性研究

目的设计一种具有纵向撑开和压缩功能的颈椎椎弓根钉内固定,并行颈椎椎弓根钉置钉训练,研究其进钉准确性.方法(1)收集颈椎新鲜标本7具,先采用CT扫描椎弓根,测量椎弓根内外径的高度和宽度;(2)设计合适的椎弓根钉内固定系统;(3)在收集的7具颈椎新鲜标本70个椎弓根上行置钉操作训练,评价其置钉准确性.结果颈椎椎弓根直径一般>4.5mm,其高度大于宽度,可适于椎弓根钉内固定使用,颈椎椎弓根钉置钉的准确性高.但颈椎椎弓根存在个体差异,宜行个体化进钉.结论颈椎椎弓根解剖学上可以满足椎弓根钉内固定的使用.     

颈椎椎弓根钉内固定研制及置钉准确性研究

目的:设计一种具有纵向撑开和压缩功能的颈椎椎弓根钉内固定,并行颈椎椎弓根钉置钉训练,研究其进钉准确性。方法:(1)收集颈椎新鲜标本7具,先采用CT扫描椎弓根,测量椎弓根内外径的高度和宽度;(2)设计合适的椎弓根钉内固定系统;(3)在收集的7具颈椎新鲜标本70个椎弓根上行置钉操作训练,评价其置钉准确性。结果:颈椎椎弓根直径一般>4.5mm,其高度大于宽度,可适于椎弓根钉内固定使用,颈椎椎弓根钉置钉的准确性高。但颈椎椎弓根存在个体差异,宜行个体化进钉。结论:颈椎椎弓根解剖学上可以满足椎弓根钉内固定的使用。     

颈椎前路椎弓根螺钉置入的解剖学研究

[目的]分析颈椎前路椎弓根螺钉内固定的解剖学参数,研究其可行性;通过文献分析比较国内外相关数据。[方法]取42具成人正常干燥颈椎标本,分别用手工和三维CT测量C2^C7椎弓根高度和宽度,进钉点位置,进钉方向,前路椎弓根螺钉进钉轴线上的椎体长度、椎弓根长度及总长度,用统计学分析手工和CT测量差异。以"颈椎"、"前路"、"椎弓根"为关键词搜索CNKI、PubMed、Scopus,纳入含以上相关数据的文献进行比较分析。[结果]手工测量数据与CT数据无统计学差异。除6.4%的C3椎弓根宽度<4 mm外,C2C7椎弓根高度和宽度,进钉点位置,进钉方向,前路椎弓根螺钉进钉轴线上的椎体长度、椎弓根长度及总长度,用统计学分析手工和CT测量差异。以"颈椎"、"前路"、"椎弓根"为关键词搜索CNKI、PubMed、Scopus,纳入含以上相关数据的文献进行比较分析。[结果]手工测量数据与CT数据无统计学差异。除6.4%的C3椎弓根宽度<4 mm外,C2^C7椎体椎弓根平均高度和宽度均≥4 mm。进钉点位置:C3、C4位于椎体正中矢状面的对侧,距离正中为2C7椎体椎弓根平均高度和宽度均≥4 mm。进钉点位置:C3、C4位于椎体正中矢状面的对侧,距离正中为2³ mm;C53 mm;C5^C7位于同侧,距离正中C5:1.38 mm,C6、C7:4C7位于同侧,距离正中C5:1.38 mm,C6、C7:4⁵ mm。C35 mm。C3^C7距离椎体上终板的距离为5C7距离椎体上终板的距离为5⁸ mm。进钉点方向,与矢状面的夹角:C2、C5、C6为38°8 mm。进钉点方向,与矢状面的夹角:C2、C5、C6为38°⁴0°,C3、C4为43°40°,C3、C4为43°⁴7°;与横断面的夹角:C247°;与横断面的夹角:C2^C4角度为下倾,角度分别为19.43°,10.58°和5.93°;C5C4角度为下倾,角度分别为19.43°,10.58°和5.93°;C5^C7角度为头倾,分别为1.94°,6.29°和7.50°。各椎弓根轴线总长度为29C7角度为头倾,分别为1.94°,6.29°和7.50°。各椎弓根轴线总长度为29³2 mm,轴线上椎体长度约为14 mm。比较国内外文献中椎弓根宽度和高度以及进钉点位置显示:上述解剖学数据存在差异。[结论]该实验利用手工和三维CT进行大样本研究,为临床上应用颈椎前路椎弓根螺钉内固定提供了解剖学数据。同时针对国内外不同测量方法和测量对象得出的数据进行对比,为进一步研究其差异提供依据。     

脊柱虚拟手术系统测量下颈椎椎弓根固定相关参数精确性的实验研究

目的通过与多层螺旋CT(multi-spiral CT,MSCT)工作站测量参数进行比较,评价自主研发的脊柱虚拟手术系统(spinal virtual surgery system,SVSS)三维重建技术测量数据的精确性。方法取7具成年男性颈椎标本经MSCT扫描后,分别将信息传送至MSCT工作站及SVSS,结合下颈椎椎弓根植钉参数要求,采用两系统进行容积重建和多平面重组,重建后测量椎弓根10个参数。然后应用SPSS11.0统计软件包对两系统测量数据进行对比分析。2009年6月-2010年3月,临床应用SVSS辅助下颈椎椎弓根固定手术6例。结果 SVSS测量时发现7具标本中1个椎弓根缺失(C3)、4个椎弓根冠状位直径<3 mm(C4 1个、C5 2个、C6 1个),与MSCT工作站测量结果一致。统计学分析显示,除C3左侧椎弓根皮质骨高度、C4两侧椎弓根皮质骨宽度、C4右侧椎弓根松质骨宽度、C6左侧椎弓根入点至侧块边缘切距、C3两侧椎弓根入点至下关节突下缘距离、C3两侧及C5左侧椎弓根入点至椎体前缘矢状位距离,以及C3两侧、C5左侧、C6右侧椎弓根入点至椎体前缘轴位距离共计14组数据,两系统比较差异有统计学意义(P<0.05)外;其余数据差异均无统计学意义(P>0.05)。临床应用6例共植钉34枚,术后MSCT复查发现30枚(88.24%)完全位于椎弓根内,4枚(11.76%)穿破。参照Richter等的分级标准,1级穿破2枚(5.88%),2级穿破2枚(5.88%),无3级穿破发生。结论 SVSS与MSCT工作站测量数据的准确性基本相同。     

颈椎椎弓根与其周围神经结构的解剖学关系

目的　确定颈椎弓根与其周围神经根及硬膜囊结构的解剖学关系。方法　 2 0具尸体标本后侧冠状面经椎弓根切开 ,观察测量颈椎弓根与其附近神经根及硬膜囊的关系。去除标本后侧的棘突 ,椎板及侧块 ,显露颈椎3～ 7椎弓根之峡部 ,神经根及硬膜囊 ,直接测量椎弓根上下缘及其内侧缘到神经根及硬膜囊之间的距离 ;同时 ,对椎弓根峡部的高度、宽度也予以测量。结果　颈3～ 7椎弓根与其上侧方之神经根及其内侧硬膜囊之间没有间隙。椎弓根与其下方之神经根之间的距离为 1.4～ 1.6mm ,椎弓根高度和宽度分别为 6 .0～ 6 .5mm和 4 .7～ 5 .3mm。男女之间椎弓根的高度具有显著性差异 (P <0 .0 0 1) ,而其宽度在颈4和颈6也有差异 (P <0 .0 5 )。结论　椎弓根螺钉穿破其上侧皮质及内侧皮质容易导致神经损伤 ,而穿破下侧皮质则较少见     

经骶髂关节置入骶1椎弓根螺钉的解剖学和影像学测量

目的:通过S1椎弓根的解剖学和影像学测量,探讨经骶髂关节置入S1椎弓根螺钉的可行性。方法:测量16具尸体骨盆标本双侧S1椎弓根前后缘的高度、深度(S1椎弓根最狭窄处的宽度)、骶翼深度、骶翼高度。测量骨盆出口位X线片上S1椎弓根的高度,并与解剖学测量结果比较。在轴位CT上测量髂骨后缘到骶翼、S1椎弓根、S1椎弓根纵轴的距离、髂骨外板与骶椎前缘皮质的距离。观察S1椎弓根矢状切面,评估置入2枚经S1椎弓根骶髂螺钉的安全区。结果:S1椎弓根前、后缘的高度平均为30.2mm和26.1mm,椎弓根深度和骶翼深度平均为27.8mm和45.8mm,骶翼后部平均高度为28.7mm。骨盆出口位X线片上S1椎弓根的平均高度是20mm,小于解剖学测量结果(P<0.0001)。轴位CT上,S1椎弓根纵轴在髂骨外板投影点到髂骨后缘的距离平均为32.5mm,到坐骨大切迹最高点的距离平均为38.6mm,髂骨外板到S1椎体前缘皮质的距离平均为105.2mm。结论:置入1枚S1椎弓根螺钉是安全的,常规置入2枚椎弓根螺钉可能较困难。     

胸椎经椎弓根内固定的解剖学研究与内固定器的研制

目的　为胸椎经椎弓根内固定的应用提供解剖学依据 ,设计一种胸椎经椎弓根内固定器。方法　用游标卡尺对 10具成人T1～ 11椎体干燥标本、 2 0份X线片、 2 0份MRI和CT片的椎弓根高度、宽度、长度、进钉点定位及椎弓根轴线的角度、椎弓根之间的宽度、椎弓根的毗邻等进行观测。结果　确定进钉点在上位椎体下关节突下缘的外缘线上 3mm处 ,与矢状线的夹角在 15°～ 2 0°,T4 以上椎体可容纳直径 5 0mm、长度 3 0～ 3 5cm的椎弓根螺钉 ,T4 以下椎体可容纳直径 4 5mm、长度 3 5～ 4 0cm的椎弓根螺钉。结论　胸椎经椎弓根螺钉可较安全地置入椎弓根 ,内固定器能很好的复位骨折椎体 ,间接减压椎管     

Anatomy of large animal spines and its comparison to the human spine: a systematic review

Animal models have been commonly used for in vivo and in vitro spinal research. However, the extent to which animal models resemble the human spine has not been well known. We conducted a systematic review to compare the morphometric features of vertebrae between human and animal species, so as to give some suggestions on how to choose an appropriate animal model in spine research. A literature search of all English language peer-reviewed publications was conducted using PubMed, OVID, Springer and Elsevier (Science Direct) for the years 1980–2008. Two reviewers extracted data on the anatomy of large animal spines from the identified articles. Each anatomical study of animals had to include at least three vertebral levels. The anatomical data from all animal studies were compared with the existing data of the human spine in the literature. Of the papers retrieved, seven were included in the review. The animals in the studies involved baboon, sheep, porcine, calf and deer. Distinct anatomical differences of vertebrae were found between the human and each large animal spine. In cervical region, spines of the baboon and human are more similar as compared to other animals. In thoracic and lumbar regions, the mean pedicle height of all animals was greater than the human pedicles. There was similar mean pedicle width between animal and the human specimens, except in thoracic segments of sheep. The human spinal canal was wider and deeper in the anteroposterior plane than any of the animals. The mean human vertebral body width and depth were greater than that of the animals except in upper thoracic segments of the deer. However, the mean vertebral body height was lower than that of all animals. This paper provides a comprehensive review to compare vertebrae geometries of experimental animal models to the human vertebrae, and will help for choosing animal model in vivo and in vitro spine research. When the animal selected for spine research, the structural similarities and differences found in the animal studies must be kept in mind.     

Pedicle morphology of the immature thoracolumbar spine

STUDY DESIGN: Human vertebral morphologic data were compiled from anatomic skeletal collections from three museums. OBJECTIVES: To quantify the morphometric characteristics of the pedicles of the immature thoracolumbar spine. SUMMARY OF BACKGROUND DATA: Little is known of pedicle morphology of the immature spine as related to pedicle screw fixation. METHODS: A total of 75 anatomic skeletal specimens were acquired from C1 to L5 in the age range of 3 to 19 years. The data were collected and analyzed using a computerized video analysis system. Each vertebral pedicle was measured in the axial and sagittal planes. The measurements included the minimum pedicle width, the pedicle angle, the distance to anterior cortex, and anteroposterior and interpedicular spinal canal diameters. RESULTS: Wide variation in pedicle morphology between specimens at each vertebral level was found in the young population. In general, compared with the average adult data, a younger spine demonstrated a near uniform reduction in the linear pedicle dimensions at each vertebral level. Pedicles from the lower lumbar vertebrae attained dimensions acceptable for standard screw sizes at an earlier age than in the thoracic vertebrae. CONCLUSIONS: The data in this study indicates that pedicle screws may be used in the adolescent spine. However, care should taken to accurately ascertain pedicle size before surgery so that improper use of screws can be avoided. Growth of the pedicles in relation to the spinal canal indicates that the increase in pedicle size is lateral to the spinal canal.     

Cervical human vertebrae. Quantitative three-dimensional anatomy of the middle and lower regions

In this study, the three-dimensional quantitative anatomy of middle and lower cervical vertebrae was determined. The three-dimensional coordinates of various marked points on the surface of the vertebra were measured with a specially designed morphometer instrument. From these coordinates, linear dimensions, angulations, and areas of surfaces and cross-sections of most vertebral components were calculated. The results showed two distinct transition regions: 1) toward the thoracic spine by the wider C7 vertebra but narrower spinal canal; and 2) toward the upper cervical region with the larger pedicle and spinous process of C2. Based on the study of 72 human cervical vertebrae, mean and standard error of the mean values of some clinically important dimensions of vertebral body, spinal canal, pedicles, transverse processes, spinous process, and uncovertebral joints are given for C2-C7 vertebrae. The areas of the end plates, spinal canal, and pedicles were modeled by elliptical and triangular shapes, and results were compared with the actual measurements.     

颈椎弓根毗邻神经解剖结构观察及置钉相关性研究

目的：测量颈椎弓根和毗邻结构之间的量化关系值,为在颈椎弓根内安全置钉提供帮助,以减少并发症。方法：在15具经福尔马林防腐处理的尸体上,去除颈椎棘突,椎板,相关韧带及侧块,上、下关节突,暴露出颈椎弓根的狭窄部及毗邻的神经组织。直接测量椎弓根内壁与硬膜囊的距离（PDSD）、椎弓根狭窄部内壁间的距离（IPD）以及该节段硬膜囊横径（DSW）。结果：15具标本中,PDSD：0～6．2mm,IPD：21．0～25．4mm,DSW：13．5～18．3mm。男女之间有差异。并图示了硬膜外静脉丛与椎弓根的关系。结论：大多数情况下,颈椎弓根与毗邻的神经结构之间存在一定的距离。向颈椎弓根的内、上方置入椎弓根螺钉是相对安全的。     

Quantitative three-dimensional anatomy of lumbar vertebrae in Singaporean Asians

This paper details the quantitative three-dimensional anatomy of lumbar vertebrae L1-L5 from Asian (Singaporean) subjects based on 60 lumbar vertebrae from 12 cadavers. The purpose of the study was to measure the dimensions of the various parameters of the lumbar vertebrae and thereafter to compare the data with a study performed on Caucasian specimens. Measurements were taken with the aid of a three-dimensional digitiser. The means and standard errors for linear, angular and area dimensions of the vertebral body, spinal canal, pedicle, and spinous and transverse processes were obtained for each lumbar vertebra. From this comparison, it was found that the dimensions of the vertebral body of the Asian subjects are slightly larger, with a maximum average difference of 8% for the posterior vertebral body height. The dimensions of the spinal canal, pedicle, and spinous and transverse processes of Asian subjects are smaller. The greatest difference can be found in the spinal canal area and pedicle width, which are smaller by an average of 30% and 20%, respectively. With the exception of the spinal canal depth, spinal canal area and pedicle width, all other parameters compared show a similar trend. The findings can provide more accurate modelling for analysis and spinal implant design and also allow more precise clinical diagnosis in sub-Asian groups.     

Comparative anatomy of the porcine and human thoracic spines with reference to thoracoscopic surgical techniques

Background This study compared porcine and human thoracic spine anatomies for a better understanding of how structures encountered during thoracoscopy differ between training with a porcine model and actual surgery in humans. Methods Parameters were measured including vertebral body height, width, and depth; disc height; rib spacing; spinal canal depth and width; and pedicle height and width. Results Although most porcine vertebral structures were smaller, porcine pedicle height was significantly greater than that of humans because the porcine pedicle houses a unique transverse foramen. The longus colli and psoas attach, respectively, to T5 and T13 in swine and to T3 and T12 in humans. In swine, the azygos vein generally was absent. The intercostal veins drained into the hemiazygos vein. Conclusions Several thoracoscopically relevant anatomic differences between human and porcine spinal anatomies were identified. A thoracoscopic approach in a porcine model probably is best performed from the right side. The best general working area is between T6 and T10.     

Assessing vertebral body rotation for percutaneous pedicle screw placement in scoliosis surgery

Study DesignRetrospective Review.ObjectiveThe aim of this study was to evaluate the incidence and magnitude of pedicle asymmetry as well as spinous process deviation in the healthy lumbar spine.Summary of Background DataMinimally invasive spine surgery relies on fluoroscopic imaging as bony landmarks used for instrumentation are not exposed. The precision of techniques used to determine vertebral body rotation intraoperatively may be confounded by anatomic variation or pathology. Here, we investigate the physiologic variation in different anatomic structures of the lumbar spine used for percutaneous pedicle screw placement.Methods100 normal lumbar CT scans, without evidence of acute deformity, significant spondylosis, scoliosis, or spondylolisthesis were reviewed to assess for pedicle height, width and spinous process angle (SPA) to compare symmetry between right and left sided pedicles for each vertebral body. Spinous process deviation of ≥5° in the axial plane was considered a relevant finding and the magnitude of offset from midline was calculated using the deviation angle and spinous process length.ResultsAnalysis of CT scans found that 17.5% of lumbar spinous processes had an average angular variation ≥5°. This calculates to a clinically significant 3.53 mm average offset of spinous processes from midline in 17.5% of lumbar vertebrae. Pedicle height and width measurements did not show statistically or clinically significant variation when comparing right to left lumbar pedicles.ConclusionThese results suggest that using the spinous process as a fluoroscopic landmark during intraoperative imaging to determine neutral rotation of lumbar vertebrae can be an unreliable technique. Rotational alignment can be determined more reliably by comparing left to right pedicle symmetry. These findings should be considered when selecting an operative technique to assess neutral vertebral alignment during percutaneous pedicle screw instrumentation.     

The anatomic variability of human cervical pedicles: considerations for transpedicular screw fixation in the middle and lower cervical spine

Transpedicular screw fixation has recently been shown to be successful in stabilizing the middle and lower cervical spine. Controversy exists, however, over its efficacy, due to the smaller size of cervical pedicles and the proximity of significant neurovascular structures to both lateral and medial cortical walls. To aid the spinal surgeon in the insertion of pedicle screws, a number of studies have been performed to quantify the gross dimensions and angulations of the cervical pedicle. Notwithstanding these quantitative studies, there has been a conspicuous absence of research reporting the qualitative characteristics of the cervical pedicle. The purpose of our study was to provide comparative graphical data that would systematically document the anatomic variability in cervical pedicle morphology. Such information should better elucidate the complexity of the pedicle as a three-dimensional structure and provide the spinal surgeon with a more complete understanding of cervical pedicle architecture. Twenty-six human cervical vertebrae (C3–C7) from six fresh-frozen spines were secured to a thin sectioning apparatus to produce three 0.7-mm- thick pedicle slices along its axis. Radiographs taken of these pedicle slices were scanned, digitized, and traced to facilitate visual comparison. The pedicle slices were found to exhibit substantial variability in composition and shape, not only between individual spines and vertebral levels, but also within the pedicle axis. However, the lateral cortex was consistently found to be thinner than the medial cortex in all samples. These physical findings must be noted by surgeons attempting transpedicular screw fixation in the cervical spine. Received: 3 May 1999/Revised: 13 August 1999/Accepted: 21 August 1999     

Internal morphology of human cervical pedicles

STUDY DESIGN: The internal architecture of cervical spine pedicles was investigated by thin sectioning and digitization of radiographic images. OBJECTIVES: To provide quantitative information on the internal dimensions and cortical shell thicknesses of the middle and lower cervical pedicles. SUMMARY OF BACKGROUND DATA: Although there have been a number of studies presenting data on the external dimensions of the cervical pedicle, little is known regarding its internal architecture and cortical shell thickness along the pedicle axis. METHODS: Twenty-five human cervical vertebrae (C3-C7) were secured to a thin-sectioning machine to produce three 0.7-mm-thick pedicle slices along its axis. Plain radiographs of the pedicle slices were scanned and digitized to facilitate measurement of the internal dimensions. Computer software was specifically developed to determine the external dimensions (i.e., pedicle height and width) and the internal dimensions (i.e., cortical shell thicknesses of the superior, inferior, lateral, and medial walls and the cancellous core height and width) of cervical pedicles. RESULTS: Superior and inferior wall cortical thicknesses of pedicle thin slices were similar, whereas the lateral wall cortical thickness was significantly smaller than the medial wall thickness. The medial cortical shell (average value range: 1.2-2.0 mm) was measured to be 1.4 to 3.6 times as thick as the lateral cortical shell (average value range: 0.4-1.1 mm). When medial and lateral cortical thicknesses were normalized for external dimensions, the combined cortical shell thickness was thinnest at C7 (average value range: 18. 6-25.6% of the external width), and this result was statistically significant when compared with other vertebral levels. CONCLUSIONS: The cervical pedicle is a complex, three-dimensional structure exhibiting extensive variability in internal morphology. Characteristics of the cervical pedicle at different spinal levels must be noted before transpedicular screw fixation.