经口咽前路寰枢椎复位钢板内固定的外科解剖学研究

目的为经口咽前路寰枢椎复位钢板内固定设计和应用提供解剖学依据。方法对10例新鲜的头颈部标本使用经口咽前入路进行逐层的显微外科解剖,观察咽后壁的层次、椎动脉的走行、寰枢椎的解剖毗邻关系和寰枢椎前路钢板内固定的相关解剖参数等。结果(1)咽后壁分两层和两个间隙粘膜层、椎前筋膜层,咽后间隙和椎前间隙;(2)经此入路可显露从枕骨大孔前缘至C3椎体的范围;(3)寰椎和枢椎椎动脉距中线的距离分别为寰椎(252±23)mm和枢椎(184±26)mm;(4)寰椎和枢椎可显露宽度分别为(394±22)mm和(390±21)mm,寰椎进钉点(侧块中点)间距(a)为(314±33)mm,寰椎进钉点连线与枢椎进钉点(枢椎前表面中部上关节面内缘连线与前唇下缘线之间的等距离线位于矢状中线两侧旁开3～4mm的位置)连线的垂直间距(b)为(187±27)mm,a/b比值为15～17。结论经口咽前入路行寰枢椎前路钢板内固定可行,钢板的设计应以上述测量数据为依据。     

Roentgenological aspect of the basilar artery and its significance in clinical diagnosis--angiographical study a of the basilar artery (author's transl)

Topometric study of basilar arteries was performed, using 130 normal vertebral angiograms of cases consisting of 83 males and 47 females aged 2 to 67 (mean = 38.1). The cases having clinically and/or neuroradiologically had obvious positive findings such as cerebral atrophies, cerebrovascular diseases and space-taking lesions were excluded. Selective vertebral angiography using Seldinger's technique in 120 cases and retrograde brachial angiography in remaining 10 cases was carried out. The following results were obtained. 1) The position of vertebrobasilar junction was almost at the midline in frontal view with a mean distance of 0.3 mm +/- 3.6 leftward from the midline. 2) The length of basilar artery was 25.5 mm +/- 6.6 in frontal view and 32.8 mm +/- 5.8 in lateral view. 3) The position of basilar bifurcation was almost at the midline in frontal view with a mean of 0.0 mm +/- 2.0 from the midline, and 9.3 mm +/- 4.7 above the Twining's line and 24.5 mm +/- 3.4 posterior from tuberculum sellae in lateral view. 4) As for the configulation of basilar artery in frontal view, 'straight type' was common in young age and 'curved type' in old age. 'Curved type' was divided into four subtypes. The concave rightwards curved type and/ or the reversed S-formed tortuous type were almost twice many as the concave leftwards curved type and/or the S-formed tortuous type. This result seemed to support the reports on the hemodynamic mechanism of verteral arteries that the dominant flow was present on the left side at the rate of 50 to 80%. 5) Internal diameter of basilar artery at the point of 1 cm proximal to the apex was measured. The mean value was 3.3 mm +/- 0.6 in frontal view and 3.2 mm +/- 0.5 in lateral view. Maximum diameter of basilar artery was 3.5 mm +/- 0.7 in frontal view and 3.6 mm +/- 0.6 in lateral view.     

The anatomical study of transoral atlantoaxial reduction plate internal fixation

Irreducibleanterioratlantoaxialdislocationwithventralspinalcordcompressionpresentsadifficultsurgicalchallenge.Nowasagenerallyacceptedoptionforthiscondition,decompressionthroughtransoralapproachhastobefollowedby anotheroperationwithinstrumentationandfusionofthe uppercervicalspinetoachievesegmentalstability.HarmsandKandziora1havedescribeddirectinternal platefixationsthroughtransoralapproach,buttheplate adoptedbyHarmsdidnothavealockingmechanism andtheplateusedbyKandziorafailedtoachieve immediate…     

Anterolateral and posterolateral approaches to the foramen magnum: technical description and experience from 97 cases

Over a 12-year period (1981-1993), 97 lesions located in the foramen magnum area were treated using either the posterolateral or the anterolateral approach. The former is a lateral extent of the midline posterior approach; the latter is the technique of exposure of the cervical vertebral artery applied at the C-1 to C-2 level. The choice between the two types of lateral approaches was made following three modes of localization: anteroposterior attachment, relation to the dura, and relation to the vertebral artery. Both techniques are described in detail, with special attention paid to the bone and dural openings, which vary according to the localization.The treated lesions include 91 tumors, 4 craniocervical junction malformations, 1 synovial cyst, and 1 abcess. A complete resection was realized in 95% of the tumoral cases, with a very limited morbidity and mortality (3%).     

经后路寰椎椎弓根螺钉固定的置钉研究

目的探讨经后路寰椎椎弓根螺钉固定的可行性. 方法利用20具颈椎尸体标本,模拟经后路寰椎椎弓根螺钉固定.在寰椎后弓后缘表面,经枢椎下关节突中心点纵垂线与寰椎后弓上缘下方3 mm水平线的交点作为进钉点,按内斜10度、上斜5度钻孔,经寰椎椎弓根置入直径3.5 mm的皮质骨螺钉.测量进钉点与寰椎椎弓根中线平面的距离、螺钉最大进钉深度、螺钉内斜角度和螺钉上斜角度等解剖指标,观察螺钉是否突破椎弓根和侧块骨皮质,以及椎动脉、硬膜、脊髓是否损伤等. 结果共放置40枚寰椎椎弓根螺钉,测得进钉点与寰椎椎弓根中线的平均距离为(2.20±0.42) mm,螺钉最大进钉深度平均(30.51±1.59) mm,螺钉内斜角度平均(9.70±0.67)度,上斜角(4.60±0.59)度.其中1枚螺钉因上斜角度过大穿破椎弓根上缘,8枚因后弓高度过小而突破椎弓根下缘,5枚进钉过深突破寰椎侧块前缘皮质,但均未对脊髓和椎动脉造成损伤. 结论经后路行寰椎椎弓根螺钉固定是安全可行的,但应注意进钉角度和深度.     

寰椎后弓影像学的测量与新型寰椎后弓内固定器的设计

目的测量寰椎后弓CT影像学资料相关数据,并设计新型寰椎后弓内固定器。方法根据CT影像学资料测量,矢状面测量寰椎后弓高度,水平面测量寰椎后弓厚度、后弓弦长及后结节处至弦长的距离、后结节处到左右两侧椎动脉沟距离(内侧、外侧)、左右后弓夹角(内侧、外侧),分析寰椎后弓的解剖学特点并根据数据设计新型寰椎后弓内固定器。结果寰椎后弓外侧缘半径平均26.77(22.03~31.53)mm,后结节处高度平均10.45(7.13~14.83)mm,后结节处厚度平均8.12(4.80~12.57)mm,内侧后结节处至椎动脉沟距离平均13.60(10.86~19.38)mm,外侧后结节处至椎动脉沟距离平均20.48(15.81~25.90)mm,寰椎后弓内侧夹角平均141.23(116.15~157.49)°,寰椎后弓外侧夹角平均135.47(103.58~155.51)°。左侧与右侧距后结节5 mm、10 mm、15 mm处寰椎后弓高度、厚度,以及内外侧后结节处到两侧椎动脉沟距离差异无统计学意义(P>0.05)。结论经寰椎后弓CT测量数据设计的新型寰椎后弓内固定器适合寰椎后弓的解剖特点,置钉点安全,操作简单,固定坚强,提供了新的寰椎后路内固定方式。     

Posterior C1-2 fusion using a polyaxial screw/rod system for os odontoideum with bilateral persistence of the first intersegmental artery

The authors report the case of a patient with os odontoideum, myelopathy secondary to atlantoaxial instability, and bilaterally persistent first intersegmental artery at the craniovertebral junction. Instead of occipitocervical fusion, C1-2 posterior fusion was performed using a polyaxial screw/rod system. The information obtained from 3D CT angiography studies may highlight the potential risk of vertebral artery injury in advance and reduce the risk of an intraoperative vertebral artery injury. In addition, C-1 lateral mass screw placement may be a safe procedure for cases of atlantoaxial subluxation in which there are persistent C-1 intersegmental arteries.     

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。     

Surgical anatomy of the cervical and infraclavicular parts of the long thoracic nerve

OBJECT: There is insufficient information in the neurosurgical literature regarding the long thoracic nerve (LTN). Many neurosurgical procedures necessitate a thorough understanding of this nerve's anatomy, for example, brachial plexus exploration/repair, passes for ventriculoperitoneal shunt placement, pleural placement of a ventriculopleural shunt, and scalenotomy. In the present study the authors seek to elucidate further the surgical anatomy of this structure. METHODS: Eighteen cadaveric sides were dissected of the LTN, anatomical relationships were observed, and measurements were obtained between it and surrounding osseous landmarks. The LTN had a mean length of 27 +/- 4.5 cm (mean +/- standard deviation) and a mean diameter of 3 +/- 2.5 mm. The distance from the angle of the mandible to the most proximal portion of the LTN was a mean of 6 +/- 1.1 cm. The distance from this proximal portion of the LTN to the carotid tubercle was a mean of 3.3 +/- 2 cm. The LTN was located a mean 2.8 cm posterior to the clavicle. In 61% of all sides the C-7 component of the LTN joined the C-5 and C-6 components of the LTN at the level of the second rib posterior to the axillary artery. In one right-sided specimen the C-5 component directly innervated the upper two digitations of the serratus anterior muscle rather than joining the C-6 and C-7 parts of this nerve. The LTN traveled posterior to the axillary vessels and trunks of the brachial plexus in all specimens. It lay between the middle and posterior scalene muscles in 56% of sides. In 11% of sides the C-5 and C-6 components of the LTN traveled through the middle scalene muscle and then combined with the C-7 contribution. In two sides, all contributions to the LTN were situated between the middle scalene muscle and brachial plexus and thus did not travel through any muscle. The C-7 contribution to the LTN was always located anterior to the middle scalene muscle. In all specimens the LTN was found within the axillary sheath superior to the clavicle. Distally, the LTN lay a mean of 15 +/- 3.4 cm lateral to the jugular notch and a mean of 22 +/- 4.2 cm lateral to the xiphoid process of the sternum. CONCLUSIONS: The neurosurgeon should have knowledge of the topography of the LTN. The results of the present study will allow the surgeon to better localize this structure superior and inferior to the clavicle and decrease morbidity following invasive procedures.     

Posterolateral protrusion of the vertebral artery over the posterior arch of the atlas: quantitative anatomical study using three-dimensional computed tomography angiography

OBJECT: The vertebral artery (VA) often takes a protrusive course posterolaterally over the posterior arch of the atlas. In this study, the authors attempted to quantify this posterolateral protrusion of the VA. METHODS: Three-dimensional CT angiography images obtained for various cranial or cervical diseases in 140 patients were reviewed and evaluated. Seven patients were excluded for various reasons. To quantify the protrusive course of the VA, the diameter of the VA and 4 parameters were measured in images of the C1-VA complex obtained in the remaining 133 patients. The authors also checked for anomalies and anatomical variations. RESULTS: When there was no dominant side, mean distances from the most protrusive part of the VA to the posterior arch of the atlas were 6.73 +/- 2.35 mm (right) and 6.8 +/- 2.15 mm (left). When the left side of the VA was dominant, the distance on the left side (8.46 +/- 2.00 mm) was significantly larger than that of the right side (6.64 +/- 2.0 mm). When compared by age group (< or = 30 years, 31-60 years, and > or = 61 years), there were no significant differences in the extent of the protrusion. When there was no dominant side, the mean distances from the most protrusive part of the VA to the midline were 30.73 +/- 2.51 mm (right side) and 30.79 +/- 2.47 mm (left side). When the left side of the VA was dominant, the distance on the left side (32.68 +/- 2.03 mm) was significantly larger than that on the right side (29.87 +/- 2.53 mm). The distance from the midline to the intersection of the VA and inner cortex of the posterior arch of the atlas was approximately 12 mm, irrespective of the side of VA dominance. The distance from the midline to the intersection of the VA and outer cortex of the posterior arch was approximately 20 mm on both sides. Anatomical variations and anomalies were found as follows: bony bridge formation over the groove for the VA on the posterior arch of C-1 (9.3%), an extracranial origin of the posterior inferior cerebellar artery (8.2%), and a VA passing beneath the posterior arch of the atlas (1.8%). Conclusions There may be significant variation in the location and branches of the VA that may place the vessel at risk during surgical intervention. If concern is noted about the vulnerability of the VA or its branches during surgery, preoperative evaluation by CT angiography should be considered.     

Anatomic study of the cervicothoracic spinal nerves and their relation to the pedicles

Twelve cadavers were dissected for the study of the cervicothoracic junction. The results showed that the mean heights and widths of the ganglia tend to decrease from the C-6 to T-4 nerve. The mean distances between the dura and the ganglion and the mean spinal nerve angles increased consistently from C-5 to T-4. The mean distances from the spinal nerves to the superior and inferior pedicles ranged 0.8-2.3 mm. It was noted that the mean value was significantly greater for the distance from the spinal nerve to the superior pedicle than that to the inferior pedicle for the spinal nerves C5-7 (P< or =.05). This information, in conjunction with imaging studies, may minimize spinal nerve injury during posterior pedicle screw fixation in the cervicothoracic spine.     

Aneurysms of the posterior inferior cerebellar artery-vertebral artery complex: variations on a theme

Aneurysms of the posterior inferior cerebellar artery-vertebral artery complex are relatively uncommon lesions. They include aneurysms at the origin of the posterior inferior cerebellar artery (PICA-VA), aneurysms on the distal artery (PICA) and aneurysms at the junction of the vertebral and basilar arteries (VA-BA). We have had the opportunity to treat 17 patients and study the radiological records of 9 additional patients in the past 8 years. The aneurysms ranged in size from 3 to 30 mm, with mean values of 10.6, 7.3, and 9 mm for PICA-VA lesions, distal PICA lesions, and VA-BA lesions, respectively. Three of the 4 VA-BA aneurysms were located at the midline, and the mean distance of the PICA-VA aneurysms from the midline was 7.6 to 9.4 mm; 2 aneurysms crossed the midline from their parent VA. The aneurysms were located slightly more often on the left side (left:right ratio, 1:2), were found more frequently in women (2.25:1), and occurred at a mean age of 50 years. Ten aneurysms at the origin of the PICA and 4 VA-BA aneurysms were treated via a lateral suboccipital craniectomy; 3 distal PICA aneurysms were exposed by a midline craniectomy. Surgery was carried out acutely in 5 patients. Tortuousness of the VA required contralateral approaches in 2 patients, an exploratory craniectomy in 1 patient, and an approach toward the dome of 1 patient with a VA-BA aneurysm. Morbidity was primarily due to cranial nerve dysfunction. There were no perioperative deaths. These aneurysms can easily be missed on initial radiographic examination; one appeared only on the second study, one was seen to grow over 16 days, and one was discovered at the level of C1 extracranially. Our radiographic and surgical approach to the treatment of these lesions is presented.     

寰椎椎弓根形态分类与椎弓根螺钉植钉方法研究

目的探讨寰椎椎弓根形态分类及椎弓根螺钉固定的植钉方法。方法寰椎椎弓根形态分类研究：取成人干燥寰椎标本48个，行CT三维重建，建立经过椎动脉沟底部下2mm处横切面和椎弓根中外1／3矢状面的切面图：以螺钉直径3．50mm，半径1．75mm为标准，根据通过椎弓根中外1／3矢状面的椎动脉沟底部骨质厚度，将寰椎椎弓根解剖形态分为3型：普通型40个（83％），轻度变异型6个（13％），重度变异型2个（4％）。以通过寰椎椎弓根中外1／3矢状面与通过椎动脉沟底部下方约2mm处横断面的交线为进钉通道，以进钉通道在后弓后方骨皮质上的投影点为进钉点，采用电子游标卡尺在干燥寰椎骨标本上测量以下指标：进钉点与侧块后缘的距离（L1），进钉处寰椎椎弓根高度（L2），进钉点至侧块下关节面的垂直距离（L3），进钉处侧块高度（L4），进钉处侧块宽度（L5），进钉处寰椎椎弓根宽度（L6），钉道处椎动脉沟底椎弓根厚度（H1）。寰椎椎弓根螺钉植钉方法的研究：取12个新鲜成人冷冻寰椎标本，左右侧钉道处椎动脉沟底部骨质厚度分别打磨为：1．5mm和2．5mm，1．5mm和4．0mm，2．5mm和4．0mm，每种厚度4个标本；以通过寰椎椎弓根的中外1／3矢状面与通过椎动脉沟底部下约2mm处横断面的交线为进钉通道植钉。结果左侧L1（5．79&#177;1．24）mm，L2（4．55&#177;1．29）mm，L3（5．12&#177;1．06）mm，L4（12．43&#177;1．01）mm，L5（12．66&#177;1.37）mm，L6（7．86&#177;0．77）mm，H1（4．11&#177;1．25）mm；右侧0L1（5．81&#177;1．26）mm，L2（4．49&#177;1．22）mm，L3（5．15&#177;1．05）mm，L4（12．49&#177;0．98）mm，L5（12．65&#177;1．38）mm，L6（7．84&#177;0．78）mm，H1（4．13&#177;1．29）mm；两侧比较差异均无统计学意义（P〉0．05）。模拟植钉后所有标本无螺钉向上突破椎动脉沟底骨质。结论对于寰椎后弓高度偏小的患者，可部分经寰椎后弓或跨越寰椎后弓实现寰椎的椎弓根螺钉固定，进钉位置应以术前三维CT重建和术中探查结合考虑。     

Anatomic relationship of the cervical nerves to the lateral masses

Eight cervical specimens were transversely sectioned with slices approximately 2 mm to 3 mm in thickness to evaluate the anatomic relationship of the spinal nerves to the lateral masses. Results showed that the spinal nerve either does not appear or, when it does, is situated anteromedially to the superior facet on the cross sections through the upper portion of the superior facet. The anterolateral aspect of the superior facet is free from the spinal nerve. Cross sections through the lower pedicle of the vertebra showed that the spinal nerve rested on the transverse process anterolateral to the lateral mass. The mean distances between the posterior midline of the lateral mass and the posterior border of the spinal nerve measured 15 degrees in the lateral direction were 16.1+/-1.7 mm for C3, 16.5+/-1.8 mm for CA, 16.8+/-1.2 mm for C5, 16.3+/-2.0 mm for C6, and 8.5+/-0.9 mm for C7. This study suggests that the anterolateral corner of the superior facet and the anterior aspect of the lateral mass lateral to the origin of the transverse process would be safer zones for screw exit. Attention should therefore be paid to the screw orientation for the Magerl technique and to the screw length for the Roy-Camille technique. Care should be taken to insert the screw into the C7 lateral mass.     

Biomechanical analysis of a novel hook-screw technique for C1-2 stabilization

The Food and Drug Administration has not cleared the following medical devices for the use described in this study. The following medical devices are being discussed for an off-label use: cervical lateral mass screws. Object As an alternative for cases in which the anatomy and spatial relationship between C-2 and a vertebral artery precludes insertion of C-2 pedicle/pars or C1-2 transarticular screws, a technique that includes opposing laminar hooks (claw) at C-2 combined with C-1 lateral mass screws may be used. The biomechanical stability of this alternate technique was compared with that of a standard screw-rod technique in vitro. Methods Flexibility tests were performed in 7 specimens (occiput to C-3) in the following 6 different conditions: 1) intact; 2) after creating instability and attaching a posterior cable/graft at C1-2; 3) after removing the graft and attaching a construct comprising C-1 lateral mass screws and C-2 laminar claws; 4) after reattaching the posterior cable-graft at C1-2 (posterior hardware still in place); 5) after removing the posterior cable-graft and laminar hooks and placing C-2 pedicle screws interconnected to C-1 lateral mass screws via rod; and 6) after reattaching the posterior cable-graft at C1-2 (screw-rod construct still in place). Results All types of stabilization significantly reduced the range of motion, lax zone, and stiff zone compared with the intact condition. There was no significant biomechanical difference in terms of range of motion or lax zone between the screw-rod construct and the screw-claw-rod construct in any direction of loading. Conclusions The screw-claw-rod technique restricts motion much like the standard Harms technique, making it an acceptable alternative technique when aberrant arterial anatomy precludes the placement of C-2 pars/pedicle screws or C1-2 transarticular screws.     

前路经枢椎体至寰椎侧块螺钉内固定的解剖学研究及初步临床应用

目的为临床行前路经枢椎体至寰椎侧块螺钉内固定提供理论依据。方法对21具成人寰枢椎标本进行解剖学测量,计算前路经枢椎体至寰椎侧块螺钉内固定术中螺钉走向的最小外偏角α、最大外偏角β和最大后倾角γ;21具寰枢椎标本摄正、侧位X线片,在X线片上测量此术式中螺钉走行的α、β和γ,将标本上所测的数据与在X线片上测的数据作统计学分析,并在标本上模拟这一术式。2004年10月～2006年7月,此术式应用于临床治疗5例陈旧性寰枢椎脱位患者,男3例,女2例;年龄30～55岁;病程3～24个月。脊髓损伤程度按Frankel分级,B级1例,C级2例,D级2例。术后摄X线片及CT。结果利用直角三角形的反正弦原理,由各个测量指标计算出的α、β及γ,与在X线片上所测量出的α、β及γ比较差异无统计学意义（P〉0.05）。故将数据合并后α为14.0±1.6°,β为30.0±2.3°,γ为29.0±2.9°。模拟术式中实际应用角度：α为11.2±1.6°,β为28.8±2.3°,γ为29.3±2.9°。所有寰枢椎标本经固定后肉眼观察螺钉全部位于寰枢椎中,未出现螺钉穿出寰枢椎椎体外和寰椎侧块上、椎管内及损伤椎动脉。X线片示所有螺钉均位于理想位置。临床应用5例患者术后随访6～30个月,平均14个月,X线片及CT均示效果良好;术后3个月脊髓功能恢复,采用改良Frankel分级,C级1例,D2级1例,D3级3例。结论只要正确掌握螺钉的进钉方向,采用前路经枢椎体至寰椎侧块螺钉内固定治疗寰枢椎脱位则是安全可行的;但只能使寰椎在复位的位置获得暂时稳定,尚需一期或二期加行后路寰枢植骨融合,以达到永久的牢固固定。     

Anatomical relationship of the internal carotid artery to C-1: clinical implications for screw fixation of the atlas

OBJECT: Various C1-2 instrumentation techniques have been developed to treat atlantoaxial instability. Screw fixation of C1-2 poses a risk of injury to the vertebral artery and internal carotid artery (ICA). Injury to the ICA caused by C-1 screws is extremely rare, but has been described. To characterize this risk, the authors studied the anatomical relationship of the ICA to the lateral mass of C-1. METHODS: The authors studied 100 patients who had undergone computed tomography scanning and magnetic resonance imaging of the neck to assess the position of the ICA in association with the C-1 lateral mass. Each ICA was classified into 1 of the following 4 zones: Zone 1 (medial to lateral mass), Zone 2 (medial half of lateral mass), Zone 3 (lateral half of lateral mass), and Zone 4 (lateral to lateral mass). For patients with an ICA ventral to the lateral mass, the shortest distance between the ICA and lateral mass was measured to determine the margin of error with an overpenetrated bicortical screw. RESULTS: Of the 100 patients, 58% had a left ICA in Zones 2 and 3 with a mean distance from the anterior cortex of 3.5+/-1.5 mm (+/- standard deviation), and 74% had a right ICA in Zones 2 and 3 with a mean distance from the anterior cortex of 3.9+/-1.6 mm. Both ICAs anterior to the lateral mass were noted in 47% of patients, and 84% had >or= 1 ICA anterior to the lateral mass. When the ICA was anterior to the lateral mass, it was more commonly in the lateral half (left ICA in 91% and right ICA in 92%). The left ICA was in Zone 1 in 1% and Zone 4 in 41%. The right ICA was in Zone 1 in 1% and Zone 4 in 25%. CONCLUSIONS: A high percentage of patients demonstrate an ICA directly ventral to the C-1 lateral mass, which poses a risk of ICA injury caused by an overpenetrated bicortical screw.     

The lateral spinal artery of the upper cervical spinal cord. Anatomy, normal variations, and angiographic aspects

The lateral spinal artery corresponds to the most rostral extent of the posterolateral arterial axis of the spinal cord. It supplies the posterior and lateral aspects of the spinal cord, and courses anterior to the posterior roots of the upper cervical spinal nerves (C-1 to C-4), and posterior to the dentate ligament. The lateral spinal artery anastomoses rostrally with the branches of the posterior inferior cerebellar artery (PICA) at the restiform body and laterally with the extraspinal arteries at the emergence of each nerve. It may originate either from the vertebral artery or from the PICA lateral to the medulla. Certain variations will cause an unusual but normal enlargement of the vessel in a specific portion of its course; these variations include vertebral artery duplication, a C-1 or C-2 vertebral origin of the PICA, a C-1 or C-2 occipital origin of the PICA, and an intradural course of the vertebral artery at C-2. Knowledge of these variations in the arterial supply to the area allows for an understanding of the different anatomic peculiarities present and their angiographic importance.     

Anatomic considerations for anterior instrumentation of the lumbar spine.

One hundred seventy lumbar vertebrae from L1-L4 were used to quantitatively evaluate the lumbar vertebral body and examine the relationship of the maximum posterior angles of screw placement to the spinal canal. Anatomic evaluation included dimensions of the vertebral body. Three entrance points on the lateral aspect of the vertebral body for screw insertion and an additional point 3 mm from the posterolateral corner of the spinal canal were defined and marked. The maximum posterior screw angles were determined as the angles between the line connecting the entrance point with the additional point and the coronal plane. Results showed that vertebral body dimensions increased from L1-L4. The average vertebral body depth, width, and height were approximately 26 mm, 36 mm, and 22 mm at L1, and 30 mm, 44 mm, and 23 mm at L4, respectively. The spinal canal may be penetrated if the screws are directed posteriorly 2 degrees-5 degrees at L1 - L2 and 9 degrees - 14 degrees at L3-L4 starting at the junction between the pedicle and vertebral body, 22 degrees - 32 degrees at L1-L4 from the level of 10 mm anterior to the junction, and 43 degrees -50 degrees from the level of 20 mm anterior to the junction. Therefore, mid-body screws should be directed perpendicular to the lateral plane of the vertebral body. For a more anteriorly placed screw, slightly posterior angulation is recommended.     

Vulnerability of the sympathetic trunk during the anterior approach to the lower cervical spine

STUDY DESIGN: Anatomic dissection and measurements of the cervical sympathetic trunk relative to the medial border of the longus colli muscle and lateral angulation of the sympathetic trunk relative to the midline on both sides were performed. OBJECTIVE: To determine the course and location of the sympathetic trunk quantitatively and relate this to the vulnerability of the sympathetic trunk during the anterior approach to the lower cervical spine. SUMMARY OF BACKGROUND DATA: The sympathetic trunk is sometimes damaged during the anterior approach to lower cervical spine, resulting in Horner's syndrome with its associated ptosis, meiosis, and anhydrosis. No quantitative regional anatomy describing the course and location of the sympathetic trunk and its relation to the longus colli muscle is available in the literature. METHODS: In this study, 28 adult cadavers were used for dissection and measurements of the sympathetic trunk. The distance between the sympathetic trunk and the medial borders of the longus colli muscle at C6 and the angle of the sympathetic trunk with respect to the midline were determined bilaterally. The distance between the medial borders of the longus colli muscle from C3 to C6 and the angle between the medial borders of the longus colli muscle also were measured. RESULTS: The sympathetic trunk runs in a superior and lateral direction, with an average angle of 10.4 +/- 3.8 degrees relative to the midline. The average distance between the sympathetic trunk and the medial border of the longus colli muscle is 10.6 +/- 2.6 mm. The average diameter of the sympathetic trunk at C6 is 2.7 +/- 0.6 mm. The length and width of the middle cervical ganglion were 9.7 +/- 2.1 mm and 5.2 +/- 1.3 mm, respectively. The distance between the medial borders of the longus colli muscle was 7.9 +/- 2.2 mm at C3, 10.1 +/- 3.1 mm at C4, 12.3 +/- 3.1 mm at C5, and 13.8 +/- 2.2 mm at C6, and the angle between the medial borders of the longus colli muscle was 12.5 +/- 4. 7 degrees. CONCLUSIONS: The sympathetic trunk may be more vulnerable to damage during anterior lower cervical spine procedures because it is situated closer to the medial border of the the longus colli muscle at C6 than at C3. The longus colli muscles diverge laterally, whereas the sympathetic trunks converge medially at C6. As the transverse foramen or uncovertebral joint is exposed with dissection or transverse severance of the longus colli muscle at the lower cervical levels, the sympathetic trunk should be identified and protected.