Morphometric analysis of cervical intervertebral disc space to reduce neural complications during anterior approaches to the cervical spine

BackgroundAlthough neurovascular complications rarely occur during surgical procedures, they have serious consequences. We reviewed the limits of safe surgery to decrease the possibility of neurovascular injuries.MethodsFour measurements were performed for each patient at the vertebral levels adjacent to the intervertebral discs at C3–C4, C4–C5, C5–C6, and C6–C7. These measurements were: 1)midline anteroposterior diameter of the intervertebral disc, 2)transverse diameter of the intervertebral disc, 3)right and left measurements of the line vertically drawn to the disc anterior from the most lateral point of the dura mater, and 4)measurement of the distance from measurement 3 to the right and left root.ResultsAverage anteroposterior and transverse vertebral diameters were determined to be 18.11 and 27.15 mm, respectively. Average of the results of the 3rd measurement was 5.51 mm on the right and 5.36 on the left. Average of the 4th measurement was 7.8 mm on the right 7.75 mm on the left. The shortest interval was at the C3-4 level and the longest interval was at the C6-7 level.ConclusionDetermining the safe surgery limits will help surgeons evaluating suitable implant sizes and decreasing the perioperative complications during decompression to cervical vertebrae and instrument procedures.     

颈椎椎间盘退变对终板结构生物力学特性的影响

目的研究颈椎椎间盘对终板结构生物力学特性的影响。方法50节颈椎标本,采用Nachemson椎间盘分级标准将标本分为4组,正常组(n=22)、Ⅰ度退变组(n=10)、Ⅱ度退变组(n=9)、Ⅲ度退变组(n=9),对每一终板平面上20个特定的测试点进行压缩实验,直径2mm的半球形压头以003mm/s的速度垂直于终板平面下压2mm,由所得的力─位移曲线计算出最大压缩力及刚度,采用单因素方差分析、析因分析、SNK检验及相关分析对实验数据进行统计学分析。结果颈椎椎间盘退变可导致颈椎终板最大压缩力及刚度的显著性减小(P<001),且存在负相关关系(分别为rs=-0429,P<0001;rs=-0244,P<0001);上终板随着椎间盘退变的加重终板平面中央承力逐渐变弱,外周承力逐渐增强,下终板的力学分布无明显改变。结论颈椎椎间盘退变是影响终板结构生物力学特性的重要因素,在进行颈椎前路融合术时应警惕由于椎间盘退变引起的“植入物沉陷”。     

后路寰枢椎侧块关节融合器置入的临床应用解剖

目的了解国人寰枢椎侧块关节周围血管、神经的解剖关系,为后路寰枢椎侧块关节融合器准确、安全置入提供解剖学依据。方法选用成人尸体标本20具,冠状面上观察寰枢椎侧块关节后缘周围解剖关系;平枢椎侧块上关节面后缘测量C1、2间椎动脉内缘至颈髓硬脊膜外缘的距离,确定手术冠状位的"安全操作空间";测量枢椎下关节突后内缘的纵垂线与枢椎椎弓上缘交点(G点)至枢椎椎弓根上缘中线延长线的水平距离,确定手术切入点。结果 "安全操作空间"为(19.72±1.84)mm,水平距离为(2.23±0.45)mm。寰枢椎后膜下的静脉丛主要集中在寰枢椎侧块关节的外缘、上方和内缘,其下方尤其枢椎椎弓根上缘的静脉丛稀疏。位于寰椎椎弓根下方、寰枢椎侧块关节内上侧的C2神经根,距颈硬脊膜外缘5~7 mm处膨大成颈神经节,并发出前、后支。结论 G点恒定在枢椎椎弓根上缘中线延长线的内侧2.5 mm处,以此点向外水平旁开2.5 mm,向上推开寰枢后膜,内上骨膜下剥离并沿枢椎椎弓根上缘中线一并剥离枢椎椎弓根骨膜和寰枢椎侧块关节囊,即可显露寰枢椎侧块关节并置入融合器。以此入路在"安全操作空间"内置入融合器,可避免切开寰枢后膜而损伤血管和神经,保证了手术的安全。     

椎动脉的解剖研究及在上颈椎椎弓根置钉中的应用

目的：测量上颈椎椎弓根与椎动脉的位置关系,提高上颈椎椎弓根螺钉置入的安全性。方法：成人头颈部尸体标本6具（12侧）,解剖椎动脉,测量寰椎椎弓根螺钉进钉点处椎动脉下缘距椎动脉沟底部的距离,枢椎横突孔內缘与椎动脉內缘的距离,横突孔内椎动脉的外径,记录数据并进行统计学处理。结果：寰椎椎弓根螺钉进钉点处椎动脉下缘距椎动脉沟底部的距离为左侧（1.96±0.72）mm,右侧（1.99±0.61）mm,枢椎横突孔內缘与椎动脉外缘的距离为左侧（2.23±0.43）mm,右侧（2.30±0.39）mm,横突孔内椎动脉的外径为左侧（3.03±0.48）mm,右侧（2.98±0.75）mm。结论：除了椎动脉高跨病例外,正确置入上颈椎椎弓根螺钉无损伤椎动脉之虞,椎弓根钉置入时应尽量个体化。     

Development of adjacent-level ossification in patients with an anterior cervical plate

BACKGROUND: It has been our experience that ossification occurs adjacent to anterior cervical plates. Our hypothesis was that the closer the plate is to the adjacent disc space, the greater the ossification. METHODS: We retrospectively reviewed the lateral radiographs of the cervical spine of 118 patients who had a solid fusion following an anterior cervical arthrodesis with a plate for the treatment of a degenerative cervical condition; none of the patients had had cervical spine surgery prior to the index arthrodesis. The plate-to-disc distance was measured on the postoperative lateral radiograph and was used to divide the patients into two groups for each of the two adjacent disc spaces. In group A the plate-to-disc distance was <5 mm, and in group B it was >/=5 mm. The mean duration of follow-up was 25.7 months. The severity of the ossification at the two adjacent disc spaces was classified on a scale ranging from grade 0 (no ossification) to grade 3 (complete bridging). Eighteen patients were excluded from the measurement of the severity of the caudal ossification because overlapping by the bone of the shoulder precluded adequate visualization of the caudal level. RESULTS: Ossification developed in seventy (59%) of the 118 cephalad adjacent disc spaces and twenty-nine (29%) of the 100 caudal adjacent disc spaces (p < 0.001). The mean cephalad plate-to-disc distance was shorter than the mean caudal plate-to-disc distance (p < 0.001). The rate of ossification was higher in group A than in group B, both at the cephalad adjacent disc spaces (67% compared with 24%) and at the caudal adjacent disc spaces (45% compared with 5%) (both p < 0.001). In addition, 93% (twenty-six) of the twenty-eight cases of moderate-to-severe ossification developed in group A. CONCLUSIONS: We found a positive association between adjacent-level ossification following anterior cervical plate procedures and the plate-to-disc distance. We now strive to place anterior cervical plates at least 5 mm away from the adjacent disc spaces in order to decrease the likelihood of moderate-to-severe adjacent-level ossification.     

CT-observations of the intra- and extracanalicular disc herniation

Summary A retrospective analysis of 45 patients with intra- and extracanalicular lumbar disc herniations (ICDH, ECDH), collected over a 3 year period, is presented. When an intra- or extracanalicular DH was suspected, 1.5 mm axial cuts were made with a GE 9800 from the cranial pedicle through the intervertebral canal to the pedicle of the lower vertebral body. Constructions were then made in coronal and paraxial planes to identify the pathology and its relation to the nerve root. 47% of all ICDH and ECDH were found at the level L4/5, 24% each at the levels L3/4 and L5/S1 respectively and 4% at the level L2/3. In 78% of our patients, the disc fragment was extruded and found well above the level of the disc space, in 22% at the level of the disc space. The coronal reformated views were in general better for demonstrating the course of the compressed nerve root at the levels L2/3–L4/5, while at L5/S1 the paraxial reformated view may yield better images. The distance from the midline of the spinal canal to the medial and lateral edge of the ECDH averages 16.4±3.4 and 33.3±3.6 mm and in some cases the lateral edge was found 39–44 mm from the midline. Pitfalls in the diagnosis of ECDH may be caused by scar tissue, sometimes by an upwardly displaced nerve root or ganglion and, very rarely, by a neurinoma. Pitfalls in therapy, i.g. false negative intraspinal exploration in cases of intraor extracanalicular disc herniations or exploration of the wrong intervertebral canal, may result due to insufficient neuroradiological analysis or from insufficient consideration of the anatomical situation by the neurosurgeon.     

Alterations in axial curvature of the cervical spine with a combination of rotation and extension in the conventional anterior cervical approach

Purpose

Alterations of three-dimensional cervical curvature in conventional anterior cervical approach position are not well understood. The purpose of this study was to evaluate alignment changes of the cervical spine in the position. In addition, simulated corpectomy was evaluated with regard to sufficiency of decompression and perforation of the vertebral artery canal.

Methods

Fifty patients with cervical spinal disorders participated. Cervical CT scanning was performed in the neutral and supine position (N-position) and in extension and right rotation simulating the conventional anterior approach position (ER-position). Rotation at each vertebral level was measured. With simulation of anterior corpectomy in a vertical direction with a width of 17 mm, decompression width at the posterior wall of the vertebrae and the distance from each foramen of the vertebral artery (VA) were measured.

Results

In the ER-position, the cervical spine was rotated rightward by 37.2° ± 6.2° between the occipital bone and C7. While the cervical spine was mainly rotated at C1/2, the subaxial vertebrae were also rotated by several degrees. Due to the subaxial rotation, the simulated corpectomy resulted in smaller decompression width on the left side and came closer to the VA canal on the right side.

Conclusions

In the ER-position, the degrees of right rotation of subaxial vertebrae were small but significant. Therefore, preoperative understanding of this alteration of cervical alignment is essential for performing safe and sufficient anterior corpectomy of the cervical spine.     

颈椎病术后早期神经功能严重恶化原因分析

目的 分析12例颈椎病术后神经功能恶化患者的危险因素并探讨其预防措施.方法 回顾性分析2002年9月至2007年9月间手术治疗颈椎退变性疾病3703例,术后早期(1周内)突发神经症状恶化12例(占O.3%).统计患者年龄、病程、病变范围、JOA评分、术前合并症及术后脑脊液漏等一般资料;X线片测量椎管矢状径、Povlov比值、动态狭窄参数等指标;MRI矢状位中轴层测量受压最严重节段椎管侵占率.动态狭窄参数参照改良Rao等的方法,分别测量手术节段上位椎体后下缘与下位椎板前上缘之间(UV-LL)距离,以及下位椎体后上缘与上位椎板前下缘之间(LV-UL)距离.结果 12例术后神经功能恶化者中男9例,女3例.平均年龄51岁,平均病程71个月.术前JOA评分平均10分.症状恶化后JOA评分平均5分.随访2～5年,平均末次随访时间3年6个月.末次随访时JOA评分平均9分.术前手术节段椎管矢状径平均11.8 mm,Povlov比值平均O.65.术前UV-LL间距平均11.2mm,术后12.7mm;术前LV-UL平均15.1 mm,术后13.6mm.结论 术前合并高血压、糖尿病,颈椎椎管狭窄,颈椎动力性狭窄,病变节段3节段以上是颈椎病患者术后神经功能严重恶化的危险因素.致压物呈前上后下形压迫,而患者本身又存在UV-LL间距减小的动力性狭窄,前路手术应避免患者过度仰伸;致压物形态以前下后上形为主者,后路手术应尽量避免患者颈部过度屈曲.     

Effect of plate position on clinical outcome after anterior cervical spine surgery

BACKGROUND CONTEXT: Anterior cervical plates are commonly used to provide immediate stabilization after a variety of cervical spine procedures. It has been assumed that the ideal position for anterior cervical spine plates is centered in the horizontal plane without significant angulation and without overlap of adjacent unfused levels. Nevertheless, postoperative radiographs often demonstrate actual plate position to be lateralized, rotated, or encroaching on the adjacent disc space. There have been no reported systematic studies examining the effect of variations in plate position in a large clinical population. PURPOSE: To evaluate the association between plate position and short-term clinical outcomes after anterior cervical discectomy and instrumented fusion (ACDF). STUDY DESIGN/SETTING: Review of prospectively collected clinical outcomes measures and radiographs. PATIENT SAMPLE: Patients undergoing ACDF surgery by a group of spine surgical specialists at a single institution. OUTCOME MEASURES: Direct and calculated plain radiographic measurements, visual analog scores for neck and arm pain, and SF-36 scores. METHODS: The study population included 200 patients undergoing a one-, two-, or three-level ACDF with instrumentation. Thirteen separate direct measurements and two calculated values of plate position on immediate postoperative radiographs, including lateralization, rotation, and proximity to adjacent disc spaces, were performed in blinded fashion by 3 independent reviewers. Statistical correlation with prospectively collected patient outcomes measures, including VAS for neck and arm pain and SF-36 scores, was performed. RESULTS: In the study population, average plate position was 3.3 mm from the cephalad disc space, 6.4 mm from the caudal disc space, 3.9 degrees angulation in the frontal plate, and 26% laterally displaced from the midline. At average 18.6 months of follow-up, no significant association was identified between any plate position measure and clinical outcomes. CONCLUSIONS: The use of anterior cervical plating by experienced spine surgeons is associated with variation in terms of plate position on postoperative radiographs. Within the range of positions analyzed in this study, no significant association was found between lateralized or rotated plates or plates placed in proximity to adjacent disc spaces and worse short-term clinical outcomes. It should be emphasized that these results and conclusions are based on relatively short-term clinical follow-up and that the long-term effects of variation in implant position remain unknown.     

The vascular anatomy anterior to the L5-S1 disk space

STUDY DESIGN: Dissection of 37 human cadavers was performed to assess the variability in the vascular anatomy anterior to the L5-S1 disc space. OBJECTIVES: To determine the variability of the anterior vascular anatomy at the L5-S1 disc space, and to assess its reliability as an anatomic landmark for the placement of anterior interbody fusion devices. SUMMARY OF BACKGROUND DATA: Although multiple studies have defined both the lumbar spinal anatomy and the anatomy of the great vessels, the relation of the great vessels to the anterior L5-S1 disc space has not been quantified directly. METHODS: This study investigated 35 human cadavers (17 males and 18 females). The anterior L5-S1 disc space and great vessel bifurcation were exposed through a transabdominal approach. Two independent observers each obtained 10 measurements in each specimen. RESULTS: The middle sacral artery was present in 100% of the specimens, averaging 2.5 mm in width. Its location in relation to the midline was quite variable, with a range greater than 2 cm in both the top and bottom of the disc. The distance from the bifurcation to the top of the L5-S1 disc averaged 18 mm (range, 7-36 mm). The total width between the left common iliac vein and the right common iliac artery averaged 33.5 mm (range, 12-50 mm). CONCLUSIONS: The middle sacral artery, present in 100% of the specimens, is a poor anatomic landmark for locating the midline at L5-S1. Because the average space available between the left common iliac vein and the right common iliac artery is 33.5 mm, and because the left common iliac vein averages only 12 mm from midline, the surgeon must be prepared to mobilize the local vasculature in most cases to expose the L5-S1 disc space adequately.     

Surgical anatomy of the internal branch of the superior laryngeal nerve

The internal branch of the superior laryngeal nerve (ibSLN) may be injured during anterior approaches to the cervical spine, resulting in loss of laryngeal cough reflex, and, in turn, the risk of aspiration pneumonia. Such a risk dictates the knowledge regarding anatomical details of this nerve. In this study, 24 ibSLN of 12 formaldehyde fixed adult male cadavers were used. Linear and angular parameters were measured using a Vernier caliper, with a sensitivity of 0.1 mm, and a 1° goniometer. The diameter and the length of the ibSLN were measured as 2.1±0.2 mm and 57.2±7.7 mm, respectively. The ibSLN originates from the vagus nerve at the C1 level in 5 cases (20.83%), at the C2 level in 14 cases (58.34%), and at the C2–3 intervertebral disc level in 5 cases (20.83%) of the specimens. The distance between the origin of ibSLN and the bifurcation of carotid artery was 35.2±12.9 mm. The distance between the ibSLN and midline was 24.2±3.3 mm, 20.2±3.6 mm, and 15.9±4.3 mm at the level of C2–3, C3–4, and at the C4–5 intervertebral disc level, respectively. The angles of ibSLN were mean 19.6±2.6° medially with sagittal plane, and 23.6±2.6° anteriorly with coronal plane. At the area between the thyroid cartilage and the hyoid bone the ibSLN is the only nerve which traverses lateral to medial. It is accompanied by the superior laryngeal artery, a branch of the superior thyroid artery. The ibSLN is under the risk of injury as a result of cutting or compression of the blades of the retractor at this level. The morphometric data regarding the ibSLN, information regarding the distances between the nerve, and the other consistent structures may help us identify this nerve, and to avoid the nerve injury.     

经皮前路侧块螺钉内固定植骨融合治疗C1,2不稳

目的　创建一种经皮前路侧块螺钉内固定植骨融合治疗C1,2 不稳的手术方法。方法　取 4 0名正常人影像学测量寰枢椎正位、侧位片的标准角、安全角、椎动脉内壁至寰椎上下缘中点连线的距离等相应数据 ,并用自行研制手术器械 ,对 15例C1,2 创伤性不稳的患者。男 10例 ,女 5例 ;寰枢椎 (半 )脱位 7例 ,陈旧齿状突骨折伴脱位 1例 ;Jefferson骨折 3例 ;C1前弓骨折 4例。在C臂X光机监视下行经皮前路侧块螺钉内固定前路植骨融合技术治疗 ,并分析其治疗结果。结果　正位片上其标准角右侧为 2 4 0°± 3 7° ,左侧为 2 3 8°± 1 8°;安全角右侧为 15 2°～ 30 3° ,左侧为 14 8°～ 32 1°;椎动脉内壁至寰椎上下缘中点连线的距离右侧为 (5 6± 2 2 )mm ,左侧为 (5 8± 1 9)mm ;侧位片的标准角为 2 4 1°± 1 8° ;安全角为 12 6°～ 2 6 8°。 15例患者内固定均获得了满意效果 ,螺钉位置佳。无脊髓、椎动脉和食管损伤等并发症发生。穿刺创口无感染。结论　经皮前路侧块螺钉内固定治疗C1,2 不稳操作简单 ,出血少 ,创伤小 ,恢复快 ,可一期行侧块关节固定植骨融合。手术有一定风险 ,如使用合理的配套器械 ,并熟悉其解剖特点 ,在X线透视下正确选择进针点、角度和深度 ,操作规范 ,此技术是安全的。     

Radiologic landmark accuracy for optimum coronal placement of total disc arthroplasty in the lumbar spine

OBJECTIVE: This study was performed to determine which of the radiographic markers visible on an anteroposterior (AP) radiograph of the spine-the vertebral body, the pedicles, and the spinous process-provided the most accurate guide to correctly placing an intervertebral disc replacement in the coronal midline. METHOD: The coronal midline was defined as the perpendicular bisector of a line drawn between the midpoints of the two facet joints. Axial CT images were reconstructed from 35 abdominal and renal computed tomograms to compare how consistently the midpoints of the above structures fell on the coronal midline. RESULTS: The mean distance (SD) from the vertebral body midpoint, the interpedicular midpoint, and the spinous process midpoint from the coronal midline, respectively, were 0.55 mm (SD 0.45 mm), 0.19 mm (SD 0.40 mm), and 1.30 mm (SD 1.30 mm). Sixteen percent of the distances from the coronal midline to the spinous process midpoint were greater than or equal to 3 mm compared with 0% of the distances to the interpedicular midpoint or the vertebral body midpoint. CONCLUSIONS: We concluded that the interpedicular midpoint is the most accurate guide to the coronal midline. We recommend that this landmark be used in preference to the spinous processes or the midpoint of the vertebral bodies when placing the implant in intervertebral disc arthroplasty.     

下颈椎椎弓根螺旋CT扫描的三维重建及测量

目的 评价应用多层螺旋CT扫描三维重建技术测量下颈椎椎弓根相关参数的可行性. 方法 8具成年男性颈椎标本经螺旋CT扫描后,把信息传送至随机工作站(Silicon Graphics O2),结合下颈椎榷弓根置钉的参数需求,进行三维重建[容积成像(VR)和多平面重组(MPR)]后测量椎弓根各个相关数据.然后对这些数据进行分析. 结果本组下颈椎椎弓根的外展角平均为42.02°±7.55°,C_7最小(35.63°±6.34°),C_4最大(46.94°±5.69°);头倾角平均为76.30°±12.01°,C_3最小(72.93°±6.57°),C,最大(81.27°±13.34°);入点至下关节缘距离平均为(11.23±1.78)mm,C_3最小[(10.54±1.25)mm],C_6最大[(12.05±1.40)mm];入点至侧块外缘距离各椎体相筹较大,平均为(2.65±1.21)mm,C_4最小[(1.69±0.81)mm],C_7最大[(3.74±0.99)mm];入点至椎体前缘距离各椎体差异较小,平均为(31.42±2.13)mm;椎弓根皮质骨高度平均为(8.43±1.30)mm,宽度半均为(5.54±1.26)mm;椎弓根松质骨高度平均为(3.69±1.19)mm,宽度平均为(2.67±1.15)mm;椎弓根皮质高度一般大于宽度,C_4内径最小,C_7内径最大. 结论 VR、MPR重建图像可满足椎弓根参数测量要求,其所测量的下颈椎椎弓根参数可满足经椎弓根手术的术前评估需求;下颈椎椎弓根变异较大.     

Cricoid Pressure Displaces the Esophagus: An Observational Study Using Magnetic Resonance Imaging

Background: Cricoid pressure (CP) is often used during general anesthesia induction to prevent passive regurgitation of gastric contents. The authors used magnetic resonance imaging to determine the anatomic relationship between the esophagus and the cricoid cartilage ("cricoid") with and without CP.

Methods: Magnetic resonance images of the necks of 22 healthy volunteers were reviewed with and without CP. Esophageal and airway dimensions, distance between the midline of the vertebral body and the midline of the esophagus, and distance between the lateral border of the cricoid or vertebral body and the lateral border of the esophagus were measured.

Results: The esophagus was displaced laterally relative to the cricoid in 52.6% of necks without CP and 90.5% with CP. CP shifted the esophagus relative to its initial position to the left in 68.4% of subjects and to the right in 21.1% of subjects. Unopposed esophagus was seen in 47.4% of necks without CP and 71.4% with CP. Lateral laryngeal displacement and airway compression were demonstrated in 66.7% and 81.0% of necks, respectively, as a result of CP.     

The projection of the cervical disc and uncinate process on the posterior aspect of the cervical spine

BACKGROUND: Surgical techniques of foraminotomy for decompression of the cervical nerve have been well described in the literature. Excessive resection of the facet joint and laminae may decrease segmental stability and increase scar formation. How much bony resection is adequate to remove a soft or hard disc herniation is not known. No studies regarding this subject are available. METHODS: Thirty-nine adult dry bone spines from C3 to C7 were used and four measurements on each vertebra were taken in this study. The first three measurements included the vertical distances between the superior borders of the lamina and the vertebral body measured at the midline of the laminae, the middle of the lamina, and the lamina-facet junction, respectively. The fourth was the horizontal distance between the medial most border of the superior facet and the tip of the uncinate process. RESULTS: No significant differences between male and female specimens were found in any measurements in this study. The mean vertical distances from the superior border of the lamina inferior to the superior border of the vertebral body measured at the three points for all levels were approximately 1-3 mm, although the standard deviations for those were relatively high. The tip of the uncinate process was located from 2 mm at C3 to 1 mm at C6 medial to the medial most border of the superior facet, and then changed to be located 1 mm lateral to the medial most border of the superior facet. CONCLUSIONS: This study suggests that a semicircular laminotomy placed on the inferior aspect of the lamina above may be adequate for a lateral soft disc herniation because the inferior border of the disc is higher than the superior border of the inferior lamina, whereas a traditional foraminotomy is needed for a hard disc pathology.     

Surgical anatomy of the cervical sympathetic trunk during anterolateral approach to cervical spine

The sympathetic trunk is sometimes damaged during the anterior and anterolateral approach to the cervical spine, resulting in Horner’s syndrome. No quantitative regional anatomy in fresh human cadavers describing the course and location of the cervical sympathetic trunk (CST) and its relation to the longus colli muscle (LCM) is available in the literature. The aims of this study are to clearly delineate the surgical anatomy and the anatomical variations of CST with respect to the structures around it and to develop a safer surgical method that will diminish the potential risk of CST injury. In this study, 30 cadavers from the Department of Forensic Medicine were dissected to observe the surgical anatomy of the CST. The cadavers used in this study were fresh cadavers chosen at 12–24 h postmortem. The levels of superior and intermediate ganglions of cervical sympathetic chain were determined. The distance of the sympathetic trunk from the medial border of LCM at C6, the diameter of the CST at C6 and the length and width of the superior and intermediate (middle) cervical ganglion were measured. Cervical sympathetic chain is located posteromedial to carotid sheath and just anterior to the longus muscles. It extends longitudinally from the longus capitis to the longus colli over the muscles and under the prevertebral fascia. The average distance between the CST and medial border of the LCM at C6 is 11.6 ± 1.6 mm. The average diameter of the CST at C6 is 3.3 ± 0.6 mm. Superior ganglion of CSC in all dissections was located at the level of C4 vertebra. The length and width of the superior cervical ganglion were 12.5 ± 1.5 and 5.3 ± 0.6 mm, respectively. The location of the intermediate (middle) ganglion of CST showed some variations. The length and width of the middle cervical ganglion were 10.5 ± 1.3 and 6.3 ± 0.6 mm, respectively. The CST’s are at high risk when the LC muscle is cut transversely, or when dissection of the prevertebral fascia is performed. Awareness of the CST’s regional anatomy may help the surgeon to identify and preserve it during anterior cervical surgeries.     

经前路颈椎多节段椎管扩大术的实验研究

目的设计颈椎前路椎管扩大术式并探讨该术式的可行性,为颈椎管多节段狭窄症提供新的手术方法。方法标本实验:选用4具C1～T1尸体颈椎标本,去除前方肌肉,保留后侧肌肉及固有韧带,解剖出横突孔,沿椎动脉走行,穿入直径3mm橡胶管,注入造影剂。沿C4～6椎体前正中纵行劈开,依次横向撑开3、6、9、12mm,并用木块填塞,三维CT下观察椎管前后径、横径、截面积、两侧椎动脉的直径、间距,神经根管变化。动物实验:用4只成年绵羊,麻醉后暴露出C3,4颈椎前方,将C3,4椎体纵向劈开,横向撑开9mm,取同侧胫骨9mm×9mm×15mm骨块植入撑开区。术后观察四肢运动恢复情况。结果标本在撑开3、6、9mm后,椎管前后径平均增加1.14%、3.53%、5.15%,横径增加7.92%、14.62%、22.74%,截面积增加8.52%,17.99%,25.01%;在撑开3、6、9mm时,两侧椎动脉走行间距平行,撑开12mm时,在C3,4和C6,7椎间椎动脉间距相差2mm,但走行无折屈、受压。撑开前后神经根管各径及长度无变化。标本在撑开3、6、9mm时未见骨折,撑开12mm时2具左侧、1具右侧椎板靠近棘突部骨折,均为裂纹骨折,无移位。4只绵羊术后第2d四肢可以自由行走,无神经、血管损伤征兆。结论经前路颈椎体纵向劈开扩大术,可以增加椎管容积、不影响脊柱三柱稳定结构。动物实验表明椎体横向撑开一定范围内(≤9mm)对颈髓及周围组织无损伤迹象。实验结果初步证实经前路颈椎椎管扩大术安全有效。     

Anatomical study of the cervical nerve roots for posterior foraminotomy: cadaveric study

Background

Anatomical study of the relationship among the cervical nerve roots, intervertebral disc, and lateral mass is important for the neurosurgeon to avoid complications of posterior cervical foraminotomy.

Methods

Six adult cadavers were studied. The muscles of the back of the neck were removed to expose the cervical vertebrae posteriorly from C3 to C7. We measured the length, height, extent, and angulations of the nerve roots from the medial point of the facet (MPF) after a total laminectomy, then after one-half facetectomy. The height, width, anteroposterior diameter of the lateral mass, then the height and anteroposterior diameter of the neural foramen were also measured.

Results

After total laminectomy from C3 to C7, all measures were taken from MPF showed that the mean length of the exposed root was 6.5–8.8 mm while vertical distance was 4–5.4 mm and the horizontal distance was 5.1–7.1 mm. Following a medial one-half facetectomy; the mean length of the exposed root was 8.9–12.3 mm, the vertical distance was 5.5–7.3 mm while the horizontal distance was 7.1–9.8 mm. The mean angulations of the nerve roots were 50.9–53.3º. There was a significant difference after total laminectomy and medial one-half facetectomy.

Conclusion

Anatomic and morphologic study of the cervical nerve roots and their relationships to the lateral mass and the intervertebral disc are useful landmarks to reduce the operative complications of the posterior foraminotomy.     

Correlation of cervical endplate strength with CT measured subchondral bone density

Cervical interbody device subsidence can result in screw breakage, plate dislodgement, and/or kyphosis. Preoperative bone density measurement may be helpful in predicting the complications associated with anterior cervical surgery. This is especially important when a motion preserving device is implanted given the detrimental effect of subsidence on the postoperative segmental motion following disc replacement. To evaluate the structural properties of the cervical endplate and examine the correlation with CT measured trabecular bone density. Eight fresh human cadaver cervical spines (C2–T1) were CT scanned and the average trabecular bone densities of the vertebral bodies (C3–C7) were measured. Each endplate surface was biomechanically tested for regional yield load and stiffness using an indentation test method. Overall average density of the cervical vertebral body trabecular bone was 270 ± 74 mg/cm³. There was no significant difference between levels. The yield load and stiffness from the indentation test of the endplate averaged 139 ± 99 N and 156 ± 52 N/mm across all cervical levels, endplate surfaces, and regional locations. The posterior aspect of the endplate had significantly higher yield load and stiffness in comparison to the anterior aspect and the lateral aspect had significantly higher yield load in comparison to the midline aspect. There was a significant correlation between the average yield load and stiffness of the cervical endplate and the trabecular bone density on regression analysis. Although there are significant regional variations in the endplate structural properties, the average of the endplate yield loads and stiffnesses correlated with the trabecular bone density. Given the morbidity associated with subsidence of interbody devices, a reliable and predictive method of measuring endplate strength in the cervical spine is required. Bone density measures may be used preoperatively to assist in the prediction of the strength of the vertebral endplate. A threshold density measure has yet to be established where the probability of endplate fracture outweighs the benefit of anterior cervical procedure.