下颈椎前路椎弓根螺钉固定系统的设计与运用

目的：研究下颈椎前路椎弓根螺钉钢板系统运用的可行性,为临床使用提供依据。方法：对16具颈椎标本随机分割获得C3．4,C4加C5．6,C6,7各8个运动单元（functionalspinalunit,FSu）,共32个FSU。运用下颈椎前路椎弓根螺钉钢板系统模拟植入重建FSU稳定性。测量钢板螺钉与椎体之间的适应性,运用X线摄片及CT扫描及重建评估下颈椎前路椎弓根螺钉植入的准确性,对于穿破椎弓根的标本,解剖明确其累及周围组织的情况。结果：32个FSU共计植入下颈椎前路椎弓根螺钉64枚,所有螺钉均顺利植入,无术中植入困难者。螺钉植入后与钢板螺钉孔之间的匹配程度好,未见难以锁紧的情况。钢板与椎体之间适应性良好。X线片提示所有64枚下颈椎前路椎弓根螺钉植入位置满意,螺钉长短合适。CT横断位像提示共有6枚螺钉在下颈椎椎弓根穿出,2枚内侧皮质1度穿破,4枚1度外侧缘皮质穿破累及横突孔内侧缘,未见螺钉≥2度穿破椎弓根。2枚下颈椎前路椎弓根内侧皮质1度穿破的患者,解剖发现仅有椎管内椎弓根内侧的静脉丛累及,未见硬膜囊受压,未见神经根受累。4枚1度外侧缘穿破的患者有1枚横突孔内椎静脉的累及,未见椎动脉穿破累及的情况,但其中1枚螺钉紧换椎动脉而行。结论：下颈椎前路椎弓根螺钉钢板系统适应下颈椎前路椎弓根螺钉固定重建,有临床运用价值。     

颈椎斜位片在下颈椎椎弓根螺钉术的研究

目的通过C形臂X线机以不同角度拍摄的尸体颈椎样本的斜位片观测颈椎椎弓根。在此基础之上不同角度的颈椎斜位片上观察术前拟行下颈椎椎弓根钉植入的患者颈椎椎弓根影象学表现。在这两个观测的基础上找到颈椎椎弓根及螺钉植入的最佳斜位片角度。方法选用干燥的人颈椎(C3~7)标本在C形臂X线机辅助下通过透视不同的斜位角度(40°、45°、50°、55°、60°)观测椎弓根。同时在颈椎标本观测的基础上,对拟行颈椎椎弓根螺钉植入患者术前摄不同角度的颈椎斜位片(45°、50°、55°)观测颈椎椎弓根的显示。两次试验都是观测椎弓根的长度及对侧椎弓根在椎体上显影的位置(把椎体3等分)。结果通过测量发现55°颈椎双斜位片对椎弓根长度的显示及对侧椎弓根位置显示与其他角度斜位片相比有明显的统计学差异(P<0.05)。结论55°双斜位片对术前颈椎椎弓根的判断及术中椎弓根钉植入准确性的判断是斜位片的最佳角度。     

颈椎椎弓根螺钉徒手植入技术临床研究

目的：评价颈椎椎弓根螺钉徒手植入技术(无须术中影像技术引导)的安全性和可靠性。方法：作者应用Axis内固定系统(美国枢法模公司)对36例颈椎疾病患者进行颈后路经椎弓根内固定术,共植入螺钉144枚。椎弓根螺钉植入要点为：①术前仔细观察颈椎的侧位和双斜位x线片,并予以CT扫描以评估螺钉进针点、进针方向以及螺钉的长度及直径：②术中清晰地显露颈椎侧块和突间关节,用直径3．0mm高速球形磨钻去除侧块外卜象限处骨皮质,然后用2.0mm的自制手锥沿椎弓根事先确定的方向轻轻钻入,若遇阻力则需略改变方向,使其自然置入,深约2．0cm～2．5cm。确定无误后,则安置Axis钛板和置入长度合适的椎弓根螺钉;③安装完毕后,即用C掣臂作双斜位透视,无误后关闭切口。结果：从C3到C7,共植入根弓根螺钉144枚,其中10枚(6．8％)钉初次置入后感觉松动,经校正后二次置入成功,11枚(3．5％)钉道钻孔后出血较多,但及时处理后出血停止并无不良结果。术后X线斜位片及CT片显示,16枚(11．1％)螺钉穿破椎弓根,其中10枚(6．9％)螺钉穿破椎弓根外侧皮质,4枚(2,8％)钉穿破椎弓根上侧皮质,2枚(1．3％)钉穿破椎弓根卜侧皮质。随访未发现与螺钉置入穿破椎弓根皮质仃关的神经血管损伤问题。结论：本研究提示,在事先充分的埘每个患者颈椎椎弓根X线及CT解剖结构了解的情况下,徒手置入椎弓根螺钉行颈椎后路内同定是安全查行。     

颈椎椎弓根螺钉个体化置钉技术的研究

目的 颈椎椎弓根螺钉的个体化置钉的研究.方法 进行128枚椎弓根螺钉的置入,采用椎弓根螺钉的体化置入技术.手术前对患者颈椎的正侧位x线片进行研究,通过椎弓根纵轴在颈椎侧位像上的投射,确定椎弓根螺钉进钉点的横向进钉线(X线),通过对CT的研究,确定椎弓根纵轴在颈椎侧块上投射的点位,确定椎弓根螺钉进钉点的纵向定位线(Y线),在手术中通过两线的交点确定椎弓根螺钉的进钉点(O点),通过术前的X线确定椎弓根螺钉的头倾角和尾倾角,通过CT确定椎弓根螺钉的内倾角,最终确定椎弓根螺钉的进钉方向,结合手术中一定的操作技术,完成椎弓根螺钉的个体化置钉.结果 本组正确置入118枚,螺钉穿透椎弓根但基本在椎弓根内的6枚,4枚穿出经调整后准确置入.结论 颈椎椎弓根置钉应个体化.     

双侧斜位X线片判定颈椎椎弓根螺钉置入孔道准确性的实验研究

目的:探讨螺旋形导针配合双侧斜位X线片判断颈椎椎弓根螺钉置入孔道准确性的可行性。方法:在干燥人C3￣C7标本的椎弓根峡部环扎钢丝,拍摄X线片。做出通过椎弓根中央及破坏椎弓根内、外侧壁种孔3道,插入螺旋形导针,拍摄X线片。分别采用前后位与单侧斜位X线片相结合、单侧斜位X线片及双侧斜位X线片判定导针置入位置,比较X线片判定结果与实际所做孔道的符合率。结果:斜位X线片上,椎弓根椭圆形影是由椎弓根峡部形成的,螺旋形导针在判断椎弓根置入孔道位置时,双侧斜位X线片法的敏感性、特异性和准确性高于前后位与单侧斜位片结合法和单侧斜位片法。前后位与单侧斜位X线片相结合、单侧斜位X线片、双侧斜位X线片三种读片方法判定导针置入位置准确性分别为75.78%、88.89%、93.05%,三者之间存在显著性差异(P<0.05)。判断位于椎弓根中央、穿破内侧椎弓根皮质和穿破外侧皮质这3种孔道位置时,双侧斜位X线片法的准确性分别为90.21%、90.76%、94.74%,高于其它两种读片方法(P<0.05)。结论:螺旋形导针配合双侧斜位X线片用于判断颈椎椎弓根螺钉置入孔道位置的准确性是可行的。     

颈椎椎弓根螺钉内固定系统的临床应用

目的：探讨对颈椎伤病行颈椎椎弓根螺钉系统(cervical pedicle screw system，CPSS)内固定的临床应用价值。方法：回顾性分析52例颈椎伤病患者行CPSS内固定的应用情况。每位患者术前均行X线、CT等影像学检查，术中在“C”型臂X线机侧位或斜位监视下置钉，术后均摄X线片观察螺钉位置。38例平均随访13个月，观察内固定及神经症状恢复情况。介绍置钉方法，总结CPSS的应用价值，分析可能发生的并发症，探讨适应证。结果：52例螺钉均成功置入，术中无脊髓、椎动脉损伤，其中9例(10侧)经椎弓根置钉时出现神经根刺激症状，调整置钉方向后置入成功。术后X线片提示螺钉位置良好。随访时未发现断钉、脱钉现象。临床应用证实CPSS内固定有椎间撑开作用，并对向椎管内移位的骨折块及创伤性椎间盘突出有间接复位作用。结论：CPSS内固定是可供选择的颈椎后路固定方法之一，但应严格掌握适应证，术中须谨慎操作。     

导航辅助置入下颈椎椎弓根螺钉的误差分析

[目的]探讨导航辅助置入下颈椎椎弓根螺钉的准确性和产生误差的原因.[方法]25例下颈椎疾患手术病人,导航辅助下置入144枚颈椎(C3-7,)椎弓根螺钉,术后行X线、CT检查,横断位测量螺钉中线与椎弓根内壁的相对位置、与椎体中线的角度;矢状位测量螺钉中线与椎弓根上壁的相对位置、与椎体上缘的角度;并与导航图像的对应数据进行统计学分析.[结果]2枚螺钉穿出椎弓根上壁,3枚螺钉穿出椎弓根外壁入椎动脉孔,其它螺钉术后CT和术中导航图像所显示的位置角度无显著性差异,导航图像的显示是基于坚硬物体原则,颈椎手术本身特点不可能完全满足如此要求,两者偏差表现为"漂移"现象.[结论]导航辅助置入下颈椎椎弓根螺钉准确性显著提高,术中漂移是置钉偏差的原因.     

颈椎椎弓根技术在下颈椎疾患应用的临床疗效观察

[目的]探讨颈椎椎弓根内固定技术在下位颈椎疾患应用的临床疗效。[方法]回顾2000年8月~2007年8月对118例患者,置入490枚椎弓根螺钉治疗下颈椎疾患,其中颈椎骨折脱位81例,颈椎病合并椎管狭窄21例,颈椎黄韧带骨化11例,颈椎后突畸形2例,强直性脊柱炎3例。术前应用图像存储传输系统(简称PACS),采用X线片及64排CT片,对患者下位颈椎椎弓根的冠状位、矢状位、横断位进行精确测量,得出椎弓根的长度、宽度、高度、向内侧倾斜、向头侧倾斜角度的数据值,以指导术中选钉及置钉。术中应用自行研制的颈椎椎弓根定位导向器,准确定位入钉点及角度,打孔、置钉、固定。[结果]术后102例患者获13~65个月随访,平均随访时间18.95个月。采用JOA评分标准[1],结果:优82例,良15例,可3例,差2例,优良率95.01%。术后X线及CT示固定节段稳定,颈椎椎体高度和生理曲度维持良好,内固定位置良好,无植骨块脱出或钢板、螺钉松动、断裂等并发症,无脊髓及椎动脉损伤。2例患者植骨块吸收未融合,融合率为97.04%。[结论]下颈椎椎弓根螺钉技术是相对安全的操作,可用于需从后路固定的颈椎疾患病例,可维持良好的颈椎生理曲度,远期临床效果满意。     

手持式颈椎椎弓根螺钉置钉瞄准器的研制及意义

目的:研制能三维调节角度的手持式置钉瞄准器,为颈椎椎弓根螺钉置钉提供帮助。方法:制作以杠杆百分表显示偏摆角度的瞄准器,利用图形矢量化软件快速处理术前轴位CT图和45°斜位X线片,精确确定进钉点、置入角度、螺钉直径与长度,推导出椎弓根术前影像学数据与瞄准器钻套调整角的关系公式,采用正弦规校验瞄准器钻套调整角。以瞄准器为钻模在9具新鲜成人标本颈椎椎弓根上进行钻孔,并进行个体化置钉。结果:共置入椎弓根螺钉46枚,42枚位置正确,正确率为91%。结论:手持式颈椎椎弓根螺钉置钉瞄准器可提高置钉的准确性和安全性,有临床应用前景。     

钉道设计在颈椎椎弓根固定中的应用

[目的]探讨钉道设计在颈椎椎弓根固定中的应用.[方法]2006～2009年16例患者在本院接受下颈椎椎弓根螺钉内固定术,术前采用颈椎螺旋CT三维重建,测量该组患者颈椎椎弓根的长度、宽度、高度、向内侧倾斜、向头侧倾斜、向尾侧倾斜角度的数据,以此为指导行术中置入椎弓根螺钉.术后半月内采用与术前程序一致的螺旋CT三维重建及钉道扫描,观察椎弓根螺钉与椎弓根各壁的关系.[结果]颈椎弓根变异较大.本组共置钉66枚,57枚螺钉完全位于椎弓根内,9枚螺钉穿破椎弓根外侧皮质壁,其中5枚穿破距离为1 mm,4枚螺钉穿破距离为2～3 mm,无椎动脉和脊髓损伤发生,置钉准确率为93%.[结论]钉道设计对术中个体化置入颈椎弓根螺钉有重要意义.     

Accuracy of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis in the pediatric population

This is a retrospective review of pedicle screw placement in adolescent idiopathic scoliosis (AIS) patients under 18 years of age who underwent robot-assisted corrective surgery. Our primary objective was to characterize the accuracy of pedicle screw placement with evaluation by computed tomography (CT) after robot-assisted surgery in AIS patients. Screw malposition is the most frequent complication of pedicle screw placement and is more frequent in AIS. Given the potential for serious complications, the need for improved accuracy of screw placement has spurred multiple innovations including robot-assisted guidance devices. No studies to date have evaluated this robot-assisted technique using CT exclusively within the AIS population. Fifty patients were included in the study. All operative procedures were performed at a single institution by a single pediatric orthopedic surgeon. We evaluated the grade of screw breach, the direction of screw breach, and the positioning of the patient for preoperative scan (supine versus prone). Of 662 screws evaluated, 48 screws (7.2 %) demonstrated a breach of greater than 2 mm. With preoperative prone position CT scanning, only 2.4 % of screws were found to have this degree of breach. Medial malposition was found in 3 % of screws, a rate which decreased to 0 % with preoperative prone position scanning. Based on our results, we conclude that the proper use of image-guided robot-assisted surgery can improve the accuracy and safety of thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis. This is the first study to evaluate the accuracy of pedicle screw placement using CT assessment in robot-assisted surgical correction of patients with AIS. In our study, the robot-assisted screw misplacement rate was lower than similarly constructed studies evaluating conventional (non-robot-assisted) procedures. If patients are preoperatively scanned in the prone position, the misplacement rate is further decreased.     

Cervical pedicle screw placement: feasibility and accuracy of two new insertion techniques based on morphometric data

This morphometric and experimental study was designed to assess the dimensions and axes of the subaxial cervical pedicles and to compare the accuracy of two different techniques for subaxial cervical pedicle screw (CPS) placement using newly designed aiming devices. Transpedicular fixation is increasingly used for stabilizing the subaxial cervical spine. Development of the demanding technique is based on morphometric studies of the pedicle anatomy. Several surgical techniques have been developed and evaluated with respect to their feasibility and accuracy. The study was carried out on six conserved human cadavers (average age 85 years). Axes and dimensions of the pedicles C3-C7 (60 pedicles) were measured using multislice computed tomography (CT) images prior to surgery. Two groups consisting of 3 specimens and 30 pedicles each were established according to the screw placement technique. For surgical technique 1 (ST1) a para-articular mini-laminotomy was performed. Guidance of the drill through the pedicle with a handheld aiming device attached onto the medial aspect of the pedicle inside the spinal canal. Screw hole preparation monitored by lateral fluoroscopy. In surgical technique 2 (ST2) a more complex aiming device was used for screw holes drilling. It consists of a frame with a fully adjustable radiolucent arm for carrying the instruments necessary for placing the screws. The arm was angled according to the cervical pedicle axis as determined by the preoperative CT scans. Drilling was monitored by lateral fluoroscopy. In either technique 3.5 mm screws made of carbon fiber polyetheretherketone (CF-PEEK) were inserted. The use of the CF-PEEK screws allowed for precise postoperative CT-assessment since this material does not cause artifacts. Screw placement was qualified from ideal to unacceptable into four grades: I = screw centered in pedicle; IIa = perforation of pedicle wall less than one-fourth of the screw diameter; IIb = perforation more than one-fourth of the screw diameter without contact to neurovascular structures; III = screw more than one-fourth outside the pedicle with contact to neurovascular structures. Fifty-six pedicle screws could be evaluated according to the same CT protocol that was used preoperatively. Accuracy of pedicle screw placement did not reveal significant differences between techniques 1 and 2. A tendency towards less severe misplacements (grade III) was seen in ST2 (15% in ST2 vs. 23% in ST1) as well as a higher rate of screw positions graded IIa (62% in ST2 vs. 43% in ST1). C4 and C5 were identified to be the most critical vertebral levels with three malpositioned screws each. Because of the variability of cervical pedicles preoperative CT evaluation with multiplanar reconstructions of the pedicle anatomy is essential for transpedicular screw placement in the cervical spine. Cadaver studies remain mandatory to develop safer and technically less demanding procedures. A similar study is projected to further develop the technique of CPS fixation with regard to safety and clinical practicability.     

Prospective evaluation of thoracic pedicle screw placement using fluoroscopic imaging

BACKGROUND: In this prospective 18-month study, 29 patients underwent posterior thoracic instrumentation with placement of 209 transpedicular screws guided by intraoperative fluoroscopic imaging and anatomic landmarks. We assessed the safety, accuracy, complications, and early stability of this technique. METHODS: Pedicle and pedicle-rib units were measured, and screw cortical penetrations were graded on anatomy and depth of penetration. All 29 patients underwent preoperative computed tomographic (CT) imaging, and 28 underwent postoperative CT imaging (199/209 screws). RESULTS: From T2 to T12, screw diameters were >or=5 mm with mean medial screw angulation measuring 20-25 degree. Of the 209 screws placed from T1 to T12, 111 had diameters greater than or equal to the pedicle width. From T3 to T9, the mean diameter of the pedicle screws exceeded the mean pedicle width. Lateral pedicle wall penetration occurred significantly more often than superior, inferior, and medial pedicle wall penetrations and anterolateral vertebral body penetration. Five of six high-risk screw penetrations occurred in one patient when intraoperative technique was compromised. We observed no new postoperative neurologic deficits, visceral injuries, or pedicle screw instrumentation failures. The three high-risk anterolateral vertebral body penetrations at T1 and T2 were associated with a significantly decreased mean screw transverse angle; the three high-risk medial pedicle wall penetrations occurring from T3 to T9 were associated with a significantly increased mean screw transverse angle. Among all 26 patients available at postoperative follow-up (mean 11.9 months), the mean loss of kyphosis correction was 2.0 degree. CONCLUSIONS: Guided by intraoperative fluoroscopic imaging and anatomic landmarks, thoracic pedicle screws can be placed safely. Early clinical follow-up reveals excellent results with minimal loss of kyphosis correction.     

In vivo accuracy of thoracic pedicle screws.

STUDY DESIGN: A retrospective observational study of 279 transpedicular thoracic screws using postoperative computed tomography (CT). OBJECTIVE: To determine the accuracy of transpedicular thoracic screws. SUMMARY OF BACKGROUND DATA: Previous studies have reported the importance of properly placed transpedicular thoracic screws. To our knowledge, the in vivo accuracy of pedicle screw placement throughout the entire thoracic spine by CT is unknown. METHODS: The accuracy of thoracic screw placement within the pedicle and vertebral body and the resultant transverse screw angle (TSA) were assessed by postoperative CT. Cortical perforations of the pedicle were graded in 2-mm increments. Screws were regionally grouped for analysis. RESULTS: Forty consecutive patients underwent instrumented posterior spinal fusion using 279 titanium thoracic pedicle screws of various diameters (4.5-6.5 mm). The regional distribution of the screws was 39 screws at T1-T4, 77 screws at T5-T8, and 163 screws at T9-T12. Fifty-seven percent of screws were totally confined within the pedicle. Although medial perforation of the pedicle wall occurred in 14% of screws, in <1% there was >2 mm of canal intrusion. Lateral pedicular perforation occurred in 68% of perforating screws and was significantly more common than medial perforation (P < 0.0005). Seventeen screws penetrated the anterior vertebral cortex by an average of 1.7 mm. Screws inserted between T1 and T4 had a decreased incidence of full containment within the pedicle (P < 0.0005) and vertebral body (P = 0.039) compared with T9-T12. The mean TSA for screws localized within the pedicle was 14.6 degrees and was significantly different from screws with either medial (mean 18.0 degrees ) or lateral (mean 11.5 degrees ) pedicle perforation (P < 0.0005). Anterior vertebral penetration was associated with a smaller mean TSA of 10.1 degrees (P = 0.01) and with lateral pedicle perforation (P < 0.0005). There were no neurologic or vascular complications. CONCLUSIONS: Ninety-nine percent of screws were fully contained or were inserted with either < or =2 mm of medial cortical perforation or an acceptable lateral breech using the "in-out-in" technique. Anterior cortical penetration occurred significantly more often with lateral pedicle perforation and with a smaller mean TSA. The incidence of fully contained screws was directly correlated with the region of instrumented thoracic spine.     

管道疏通法行颈椎弓根螺钉置入的研究

目的：通过解剖学测量及临床应用探讨“管道疏通法”（dredging pipe method,DPM)对提高颈椎弓根螺钉置入的成功率、安全性及可操作性方面的应用价值。方法：（1）颈椎骨测量：成人C3－C7干燥骨42套，共210块椎骨，在实体及CT片上，测量椎骨的相关参数；92）临床应用：颈椎失稳症患者32例，术前X线、CT测量，参照标本及患者影像测量数据和管道疏通器自动寻迹的原理，个体化设计各椎节的置钉方案。在直视下显露椎弓根管口及其管腔，确定置钉方向和位置，扩孔攻丝置钉。术后观察对比相应指标，评价置钉的位置、方向。结果：91）与DPM相关的国人颈椎实体测量数据与CT测量数据比较无显著性差异（P＞0．05）；6．67％（28／42）椎弓根的宽度小于4mm;(2)32例患者共置入颈椎弓根钉146枚，术后CT复查96枚钉，其中5枚螺钉穿破椎弓根骨皮质，成功率94．8％。未出现神经血管损伤病例。结论：（1）术前影像学测量结果可人为个体化设计手术方案的重要依据，采用DPM置钉技术实施经颈椎弓根钉内固定手术，具有直视下操作、置钉准备率高、可操作性强等特点；（2）解剖学测量表明，极少部分人（6．67％）的C3－C7的椎弓根宽度不适宜做椎弓根钉内固定。     

颈椎椎弓根螺钉徒手植入技术的临床研究

目的 评价颈椎椎弓根螺钉徒手植入技术（无须术中影像技术引导）的安全性和可靠性。方法应用Axis内固定系统（美国枢法模公司）对36例颈椎疾病患者进行颈后路经椎弓根内固定术,共植入螺钉144枚,方法如下：①术中清晰地显露颈椎侧块和突间关节,用直径3,0mm高速球形磨钻去除侧块外上象限处骨皮质,然后用2．0mm的自制手锥沿椎弓根事先确定的方向轻轻钻入,若遇阻力则需略改变方向,使其自然置入,深约2～2,5cm。确定无误后,则安置Axis钛板和置入长度合适的椎弓根螺钉。②安装完毕后,即用C型臂X线机作双斜位透视,无误后关闭切口。结果从G～G,共植入根弓根螺钉144枚,其中10枚（6．8％）钉初次置入后感觉松动,经校正后二次置入成功,11枚（3．5％）钉道钻孔后出血较多,但及时处理后出血停止并无不良结果。术后X线斜位片及CT片显示,16枚（11．1％）螺钉穿破椎弓根,其中10枚螺钉（6．9％）穿破椎弓根外侧皮质,4枚（2．8％）穿破椎弓根上侧皮质,2枚（1．3％）穿破椎弓根下侧皮质。随访未发现与螺钉置入穿破椎弓根皮质有关的神经血管损伤问题。结论本研究提示,在事先充分的对每个患者颈椎椎弓根X线及CT解剖结构了解的情况下,徒手置入椎弓根螺钉行颈椎后路内固定安全可行。     

Analysis of accuracy of computer‐assisted navigation in cervical pedicle screw installation

Objective: To observe the accuracy of computer‐assisted navigation (CAN) in cervical pedicle screw installation and to analyze the reasons for screw malposition. Methods: From October 2004 to December 2009, 144 cervical pedicle screws were installed in 25 patients with cervical spinal diseases using CAN. Screw position and direction were measured on sagittal and transection images from intraoperative navigation and postoperative CTs. Results: Among 144 screws inserted from C3 to C7, two perforated the upper pedicle wall and three deviated from the lateral pedicle wall. The rate of accurate cervical pedicle screw placement with CAN was 96.5% (139/144) in our group. There was no statistical difference in the position and direction of the pedicle screws according to navigation images and CT scans. Conclusion: CAN can result in high accuracy of cervical pedicle installation. The excursion phenomenon is responsible for malposition of pedicle screws. Only by understanding the navigational principles of CAN and the characteristics of cervical spinal surgery, together with personal experience, can good use be made of CAN.     

胸椎椎弓根螺钉置入位置的CT评价

目的:探讨胸椎椎弓根螺钉置入的准确性和安全性。方法:对37例胸椎椎弓根螺钉内固定患者术后行CT断层扫描,观察螺钉在椎弓根内的位置,记录螺钉穿透骨壁的位置、数目和距离。结果:37例患者共置入405枚胸椎椎弓根螺钉,124枚螺钉(30.61%)穿透骨壁,其中76枚(18.77%)穿透椎弓根外侧壁,32枚(7.90%)穿透椎弓根内侧壁,16枚(3.95%)穿透椎体前壁。66枚(16.30%)穿透距离<2mm,37枚(9.14%)穿透距离在2mm~4mm之间,21枚(5.9%)穿透距离>4mm。结论:胸椎椎弓根螺钉骨壁穿透率较高,应严格按照胸椎椎弓根螺钉置入方法,仔细操作,避免出现因螺钉置入不当造成神经、血管或内脏损伤等并发症。     

Clinical accuracy of cervicothoracic pedicle screw placement: a comparison of the "open" lamino-foraminotomy and computer-assisted techniques

OBJECTIVE: Posterior transpedicular fixation at the cervicothoracic junction (CTJ) is increasing in popularity. However, the clinical accuracy of pedicle screw placement at the CTJ has not been specifically assessed. METHODS: Between January 2000 and July 2004, 60 consecutive patients underwent a variety of posterior spinal procedures necessitating pedicle screw placement at C7, T1, and T2. Thirty-two patients had cervicothoracic screws (3.5 to 4.5 mm) placed by an "open" technique (laminectomies or lamino-foraminotomies) and 28 patients with either a closed (before any decompression) 2-dimensional (n=19, fluoroscopy) or 3-dimensional (n=9, CT) computer-assisted technique. Screws were independently assessed for pedicle breach on postoperative CT and scored using a points-based classification system. RESULTS: The total number of screws placed was 86, 63 and 45 in the open, closed-2-dimensional and closed-3-dimensional groups, respectively. Overall, 61(70.9%), 51(81%), and 40(89%) screws were completely within the pedicle. In the open group, the majority of pedicle breaches were more than 2 mm [n=3 (<2 mm), n=20 (2-4 mm), n=2 (>4 mm)]. Screw violation occurred laterally 11/25(44%), medially 3/25(12%), inferiorly 7/25(28%), and superiorly 4/25(16%). In the closed technique, all breaches were lateral. Seventeen screws (n=11-2-dimensional, n=5-3-dimensional) breached the pedicle by a margin of less than 2 mm and 1 screw (2-dimensional) by 2 to 4 mm. Pedicle screw accuracy was significantly improved with computer-assisted techniques. However, there was no significant difference between the 2-dimensional and 3-dimensional techniques. For all patients, there were no clinically significant screw misplacements, nor any need for screw revision. CONCLUSIONS: Computer-assisted surgery allows for more accurate placement of pedicle screws at the CTJ. Although a higher proportion of major pedicular breaches occurred in the "open lamina/lamino-foraminotomy" group, no screws required revision in either group.     

Accuracy and complications of transpedicular C2 screw placement without the use of spinal navigation

The objective of the study was to describe the technique, accuracy of placement and complications of transpedicular C2 screw fixation without spinal navigation. Patients treated by C2 pedicle screw fixations were identified from the surgical log book of the department. Clinical data were extracted retrospectively from the patients’ charts. Pedicle screw placement accuracy was assessed on postoperative CT scans according to Gertzbein and Robbins (GRGr). A total of 27 patients were included in the study. The mean age of the patients was 56 ± 22.0 years; 51.9% of them were female. As much as 17 patients suffered from trauma, 5 of degenerative disease, 3 of inflammations and 2 of metastatic disease. A total of 47 C2 transpedicular screw fixations were performed. The canulated screws were inserted under visual control following the preparation of the superior surface of the isthmus and of the medial surface of the pedicles of the C2. Intraoperative fluoroscopy was additionally used. The postoperative CT findings showed in 55.3% GRGr 1, in 27.7% GRGr 2, in 10.6% GRGr 3, and in 6.3% GRGr 4 pedicle screw insertion accuracy. Screw insertions GRGr 5 were not observed. Screw malpositioning (i.e., GRGr 3 and 4) was significantly associated with thin (<5 mm) pedicle diameters and with surgery for C2 fractures. In the three patients with screw insertions GRGr 4, postoperative angiographies were performed to exclude vertebral artery affections. In one of these three cases, the screw caused a clinically asymptomatic vertebral artery compression. Hardware failures did not occur. In one patient, postoperative pneumonia resulted in the death of the patient. Careful patient selection and surgical technique is necessary to avoid vertebral artery injury in C2 pedicle screw fixation without spinal navigation. A slight opening of the vertebral artery canal (Gertzbein and Robbins grade ≤3) does not seem to put the artery at risk. However, the high rate of misplaced screws when inserted without spinal navigation, despite the fact that no neurovascular injury occurred, supports the use of spinal navigation in C2 pedicle screw insertions.