后路经侧块关节螺钉内固定技术治疗寰枢椎不稳

目的：评价Magerl法内固定治疗寰枢椎不稳或脱位的临床疗效。方法：寰枢椎不稳14例,男10例,女4例;年龄17～62岁,平均38.6岁。均实施后路复位,Magerl法经关节螺钉内固定和自体髂骨植骨。结果：14例患者共植入经关节螺钉28枚。所有患者获随访,时间9～35个月,平均16个月,术后JOA评分13.8～15.8分,平均（14.50±0.66）分。改善率平均（76.12±4.94）%。术后无椎动脉和脊髓损伤发生,植骨全部融合。结论：Magerl法固定是治疗寰枢椎不稳的良好方法之一,无须加用结构性植骨和辅助内固定,自体颗粒状松质骨植骨即可实现有效的骨性融合。     

Atlantoaxial transarticular screw fixation and posterior fusion using polyester cable: a 10-year experience

Purpose

To retrospective review the clinical outcomes of the modified operative technique using a polyester suture material (Ethibond* Excel) for atlantoaxial transarticular screw fixation and posterior fusion.

Methods

The retrospective reviews were conducted from 2002 to 2012. The patient’s medical record reviews included demographic data, cause of atlantoaxial instability, orthopedic and surgical history, clinical presentation, radiographic finding including plain radiography, complications, operative detail, and outcome of treatment. Fusion of C1–C2 was defined as either graft consolidation or absence of C1–C2 movement on lateral flexion–extension radiograph.

Results

Twenty-three patients demonstrated clinical and radiographic evidence of atlantoaxial instability (13 men and 10 women, with a mean age of 42 years). Majority of atlantoaxial instability was caused by trauma. Most common clinical symptom was neck pain with or without cervical myelopathy. Bilateral screws were placed in 18 of the 23 patients. Five patients underwent placement of unilateral screws. The 13 patients were inserted by screws with diameter 4.0 mm. The means screw length was 40.33 mm. The means of operative time and estimated blood loss were 3.6 h and 234 ml, respectively. The mean of follow-up duration was 18 months. All 41 screws were positioned satisfactorily in C1 lateral mass. All 23 patients achieved fusion (100 % fusion rate). After a period of follow-up, 9 of the 10 neurological deficit patients had completely recovered.

Conclusions

We concluded that the atlantoaxial transarticular screw fixation and posterior fusion using polyester cable can be used for C1–2 fusion with a high fusion rate and less complications in various cases.     

The original hole-in-one guide for atlantoaxial transarticular screw fixation

Atlantoaxial fusion by transarticular screw fixation provides firm fixation, and good results have been reported. However, there are also problems, such as injury of the vertebral artery at the time of screw insertion. For accurate facet fusion, we developed a new hole-in-one guide for screw fixation and obtained good results with its use. In 60 adult subjects, we measured the antero-posterior and transverse axes and determined the center of the atlantoaxial surface and the insertion point of the screw in three dimensions on computed tomography scans. Based on these values, we measured the optimum screw insertion angle on sagittal and coronal planes, and the distance between the center and the posterior margin of the joint surface; our new hole-in-one guide was produced with these data. When the guide tip is determined to be located at the center posterior margin of the axial joint surface, and the guidewire insertion point is determined to be located at the center of the axial inferior facet immediately above the C2/3 joint, the guidewire is passed through the axial pedicle and the center of the atlantoaxial joint. Since April 1997, we have used this hole-in-one guide technique in eight patients with atlantoaxial instability. The screws passed the pars interarticularis and the center of the atlantoaxial joint in all patients with safety and accuracy. No complications associated with this technique occurred. Received: December 24, 1999 / Accepted: August 25, 2000     

Disappearance of retro-odontoid pseudotumor after C1-C2 transarticular fixation screw

Atlantoaxial degenerative articular cysts are described in various situations like rheumatoid arthritis, dialysis, and fractures... and in the C1-C2 subluxations of degenerative origin. The treatment of these retro-odontoid tumors does not consist in excision of the pseudotumor but in the reduction of instability by cervical fusion. The procedures are varied and comprise neurological and vascular risks. We report a case of C1-C2 subluxation associated with a pseudocyst compressing the cervical spinal cord, which was treated successfully by transarticular screwing without wiring procedure. This technique has never been used previously in this indication. However, the peroperational risks are less important and the results are similar to those of the other procedures.     

Minimally invasive anterior transarticular screw fixation and microendoscopic bone graft for atlantoaxial instability

Purpose

Even though transarticular screw (TAS) fixation has been commonly used for posterior C1–C2 arthrodesis in both traumatic and non-traumatic lesions, anterior TAS fixation C1–2 is a less invasive technique as compared with posterior TAS which produces significant soft tissue injury, and there were few reports on percutaneous anterior TAS fixation and microendoscopic bone graft for atlantoaxial instability. The goals of our study were to describe and evaluate a new technique for anterior TAS fixation of the atlantoaxial joints for traumatic atlantoaxial instability by analyzing radiographic and clinical outcomes.

Methods

This was a retrospective study of seven consecutive patients with C1–C2 instability due to upper cervical injury treated by a minimally invasive procedure from May 2007 to August 2009. Bilateral anterior TAS were inserted by the percutaneous approach under Iso-C3D fluoroscopic control. The atlantoaxial joint space was prepared for morselized autogenous bone graft under microendoscopy. The data for analysis included time after the injuries, operating time, intraoperative blood loss, X-ray exposure time, clinical results, and complications. Radiographic evaluation included the assessment of atlantoaxial fusion rate and placement of TAS. Bone fusion of the atlantoaxial joints was assessed by flexion extension lateral radiographs and 1-mm thin-slice computed tomography images as radiographic results. Clinical assessment was done by analyzing the recovery state of clinical presentation from the preoperative period to the last follow-up and by evaluating complications.

Results

A total of 14 screws were placed correctly. The atlantoaxial solid fusion without screw failure was confirmed by CT scan in seven cases after a mean follow-up of 27.5 months (range 18–45 months). All patients with associated clinical presentation made a recovery without neurologic sequelae. Postoperative dysphagia occurred and disappeared in two cases within 5 days after surgery. There were no other complications during the follow-up period.

Conclusions

Percutaneous anterior TAS fixation and microendoscopic bone graft could be an option for achieving C1–C2 stabilization with several potential advantages such as less tissue trauma and better accuracy. Bilateral TAS fixation and morselized autograft affords effective fixation and solid fusion by a minimally invasive approach.     

下颈椎可屈性与寰枢关节Magerl固定术的可行性分析

目的:探讨下颈椎的屈曲程度与后路经寰枢关节螺钉固定术的可能性。方法:回顾已施行经寰枢关节螺钉固定术病例的术前颈椎过屈位X线像,测量C2～C7间的角度,复习手术经过,分析可完成螺钉固定的颈椎曲度及其它相关因素。结果:在已完成后路经寰枢关节螺钉固定术的75例患者中有58例屈颈侧位X线像显示下颈椎呈后凸状态,后凸角平均为17.25°;另17例屈颈侧位片见下颈椎呈前凸状态,但这些病例都是体形瘦长者。结论:后路经寰枢关节螺钉固定术仅适合于下颈椎可以很好屈曲及体形瘦长的病例。     

Magerl术治疗未获完全复位的寰枢椎脱位

目的：探讨Magerl术治疗未获完全复位的寰枢椎脱位的可行性及手术技巧。方法：2003年12月至2005年3月．对12例术前无固定神经定位体征、术中未获完全复位的寰枢椎不稳患者行后路经寰枢椎侧块关节UCSS空心螺钉固定（Maged术）、植骨融合术，对寰椎后弓完整的8例患者同期行后路寰枢椎钛缆固定术（Gauie术式）。通过随访并摄寰枢椎张口位和颈椎侧位X线平片，评估螺钉位置和植骨融合情况。结果：所有患者均完成双侧经关节螺钉固定，症状明显改善，无神经症状加重表现，无神经血管损伤等并发症发生。随访4～18个月（平均8个月），术后寰枢关节仍存在前脱位或（和）侧方脱位，但螺钉均通过寰枢椎侧块关节，所有置入螺钉位置准确，无寰枕关节活动受限。术后3-6个月均获骨性融合。结论：不能完全复位的寰枢关节脱位并不是Magerl术的绝对禁忌证，只要术前作好寰枢椎影像学检查并认真评估其可行性．术中采用“个体化”进钉方案，保证关节螺钉通道周围有充足的骨质，Magerl术仍是安全、可靠的。     

后路寰枢椎椎弓根钉板固定融合治疗上颈椎不稳

目的 :探 讨寰 枢 椎椎 弓根 钉 板固 定融 合 治疗 上颈 椎 不稳 的可 行 性。 方法 :在 气管 插 管全 麻 下对 13 例 患者施 行了 寰 枢椎 椎弓 根 钉板 固定 术 ,并行 自 体髂 骨植 骨 。寰 椎椎 弓 根螺 钉的 进 钉点 位于 枢 椎侧 块中 线 上 ,距 寰椎后 弓上 缘 最少 3m m ,内斜 10° ,上斜 5°枢 椎椎 弓根 螺 钉的 进钉 点 位于 枢椎 侧 块内 上象 限 ,显 露枢 椎椎 弓 内缘 。直视 下进 钉 ,内斜 25°上斜 25° 螺 钉直 径 3.5m m ,寰 椎椎 弓 根螺 钉长 28￣32m m ,枢 椎椎 弓根 螺 钉长 24￣28m m 。 , 。结果 :全 组病 例未 发 生椎 动脉 、脊 髓 损伤 ,术 后临 床症 状 得到 不同 程 度的 改善 。随 访 3￣21 个月 ,平 均 6.7 个月 。 X线、CT 复查 示螺 钉 位置 良好 ,无 松动 、断 钉 ,植骨 3 个月 后均 达 到满 意融 合 。结 论 :寰 枢 椎 椎 弓根 钉 板 固 定治 疗上颈 椎不 稳 效果 良好 ,是 寰枢 椎 后路 固定 可 供选 择的 术 式之 一。     

寰枢椎后路经关节螺钉固定术

目的评价参照枢椎椎管内壁行寰枢椎后路经关节螺钉固定（Naged技术）的可行性。方法2002年1月～2005年1月，对31例寰枢椎不稳患者行后路经关节螺钉内固定术，男18例，女13例；平均年龄36．8岁。螺钉置入方法：紧贴枢椎椎管内壁确定距离中线的距离，以枢椎椎板下缘上2帅为进针高度，两线交叉点即为螺钉进针点。螺钉平行矢状面，指向寰枢关节面后缘高度，通过C型臂机侧位像确认螺钉向上倾斜角度。术后结合正、侧位x线片、螺旋CT三维重建及断层扫描图像，评价螺钉置入准确程度。根据螺钉与寰枢椎关节面的位置关系分为A、B、C三区，A区螺钉通过寰椎下关节面；B区螺钉在关节面的前方或后方（前方为B1，后方为B2）；C区为螺钉在关节面的内侧或外侧（内侧为C1，外侧为C2）。结果共置入60枚螺钉。术中无椎动脉、颈脊髓、颈神经根及颅神经损伤。所有患者获得6～18个月（平均9个月）的随访，植骨融合时间为3～12个月，平均5个月，颈脊髓及神经根症状改善明显者3例，部分改善者5例，无改善者1例，无神经症状加重患者。枕颈部疼痛完全缓解者8例，部分缓解者6例，无缓解者2例。60枚螺钉中，A区58枚（96．7％），B1区2枚（3．3％），无B2及C区螺钉。结论参照枢椎椎管壁行寰枢椎后路经关节螺钉固定是安全可靠的。     

Atlantoaxial arthrodesis using C1-C2 transarticular screw fixation in a case of Morquio syndrome

Prophylactic or therapeutic arthrodesis is recommended for atlantoaxial instability in Morquio syndrome. Occipitocervical fusion, the common approach for upper cervical fusion in Morquio syndrome sacrifices the movements at the occipitoatlantal joints. The use of C1-C2 transarticular screws for achieving C1-C2 arthrodesis, without compromising mobility at the occipitoatlantal joint in Morquio syndrome has not been reported. We report a case of Morquio syndrome with atlantoaxial instability and odontoid hypoplasia, where we successfully achieved C1-C2 arthrodesis using transarticular screws and bone graft. The advantages of this method over other methods of atlantoaxial arthrodesis in Morquio syndrome have also been discussed.     

Atlantoaxial fusion using anterior transarticular screw fixation of C1–C2: technical innovation and biomechanical study

This study is an attempt to describe a new technique for anterior transarticular screw fixation of the atlantoaxial joints, and to compare the stability of this construct to posterior transarticular screw fixation with and without laminar cerclage wiring. Nine human cadaveric specimens were included in this study. The C1–C2 motion segment was instrumented using either anterior transarticular screws (group 1), posterior transarticular screws alone (group 2), or posterior screws with interlaminar cerclage wires (group 3). Using an unconstrained mechanical testing machine, the specimens were tested in rotation, lateral bending, and flexion-extension using nondestructive loads of ±2 N m. The specimens were also tested in translation using nondestructive loads of ±100 N. All values for the three groups with regards to anterior-posterior displacement, rotation, and lateral bending were similar as determined using a Kruskal–Wallis rank sum test with a significance level of p<0.05. The only significant difference was registered in flexion-extension where the cerclage wire added some strength to the construct. Anterior transarticular screw fixation of the atlantoaxial spine has several advantages over posterior fixation techniques, and is as stable as posterior transarticular fixation in all clinically significant planes of motion. The addition of posterior interlaminar cerclage wiring further improves resistance to flexion-extension forces. Anterior transarticular screw fixation of the atlantoaxial joint is a useful technique for achieving C1–C2 stabilization.     

Computer-assisted Magerl's transarticular screw fixation for atlantoaxial subluxation

We report two patients with rheumatoid arthritis in whom posterior atlantoaxial fixation was carried out using transarticular screws with computer assistance. Two bilateral transarticular screws were inserted in one patient; however, in the other patient, only a unilateral screw was used, because computerized images showed that the vertebral artery at the other side was placed too medially to allow insertion of the screw. Neither of these patients had any neurovascular complications after surgery. Computer-assisted surgery is useful for avoiding neurovascular complications with transarticular screw fixation of C1-2. Received: January 26, 2001 / Accepted: August 13, 2001     

后路经关节螺钉固定颗粒状植骨融合治疗寰枢关节不稳定

目的:探讨后路经C1、C2侧块关节螺钉固定、颗粒状松质骨植骨行寰枢关节融合治疗寰枢关节不稳的效果。方法:自1999年12月~2003年4月对58例因齿状突不连、寰椎横韧带断裂或松弛导致寰枢关节不稳定的病例施行了后路经C1、C2侧块关节的螺钉固定术,然后在C1、C2后弓间植入颗粒状松质骨。术中不用钛缆固定寰椎后弓与枢椎棘突。术后不需任何外固定。结果:无手术中损伤脊髓和椎动脉的病例。49例获得随访,时间6个月～3年10个月,平均20个月,全部获得了骨性融合。结论:当寰枢关节不稳定时用两枚螺钉由后路经C1、C2侧块关节固定即可起到足够的稳定作用;在C1、C2后弓间植入颗粒状松质骨可获得很高的融合率。     

寰枢椎椎弓根螺钉内固定术治疗儿童寰枢椎脱位的初步报告

目的:探讨寰枢椎椎弓根螺钉内固定手术治疗儿童寰枢椎脱位的可操作性和近期疗效。方法:2005年9月~2011年3月对16例儿童寰枢椎脱位患者采用寰枢椎椎弓根螺钉内固定术治疗,男9例,女7例;年龄5～13岁,平均9.1岁。均有枕颈部疼痛、颈部僵硬;3例有高位颈脊髓病表现,ASIA分级:D级2例,C级1例。术前均行颈椎正侧位及过伸过屈位X线片、CT和MRI检查,均诊断为寰枢椎脱位,其中寰椎横韧带断裂1例,寰枢椎骨折脱位1例,先天性齿状突畸形12例,寰枢椎固定旋转半脱位2例;颈脊髓受压5例。寰椎后弓(椎弓根)高度2.5~3.8mm,平均3.0mm;寰齿前间隙6~14mm,平均9mm。术前常规行牵引1~2周复位,完全复位7例,部分复位5例,不能复位4例。术中采用"寰椎椎弓根显露置钉法",在直视下行C1、C2置钉,复位固定,植骨融合。随访患者症状和神经功能改善情况,定期行颈椎X线片及CT复查,了解内固定及植骨融合情况。结果:16例均行双侧寰枢椎椎弓根螺钉内固定,手术过程顺利,64枚螺钉均成功置入,复位固定满意,无术中、术后神经和血管并发症。术中出血150~650ml,平均300ml;手术时间100~190min,平均130min。12例随访12~72个月,平均28.5个月,术后3~6个月寰枢椎均骨性融合;末次随访时,颈枕症状明显改善,3例术前有脊髓功能损害者均好转,2例术前ASIA分级D级者恢复到E级,1例术前ASIA分级C级者恢复到D级;未发现螺钉松动、断钉和寰枢椎再移位现象,未发现曲轴现象。结论:采用"寰椎椎弓根显露置钉法"行寰椎椎弓根螺钉内固定可操作性强,置钉安全性高;寰枢椎椎弓根螺钉内固定治疗儿童寰枢椎脱位的近期疗效满意。     

内窥镜辅助下前路经寰枢关节螺钉固定植骨融合术治疗上颈椎不稳

目的:探讨内窥镜辅助下前路经寰枢关节螺钉固定植骨融合术治疗上颈椎不稳的临床可行性及其疗效。方法:2006年1月至2009年12月采用内窥镜辅助下前路经寰枢关节螺钉固定植骨融合术治疗上颈椎不稳患者13例,男8例,女5例;年龄17~65岁,平均46.8岁。JeffersonⅡ型骨折6例,JeffersonⅢ型骨折1例,寰枢椎脱位3例,陈旧性齿状突骨折3例。患者均有枕颈部不适和活动受限,术前VAS评分为3.2～4.1分,平均3.8分;2例伴有不同程度脊髓功能损害者,按Frankel分级C级1例,D级1例。随访患者临床症状改善和植骨融合情况。结果:均在内镜辅助下顺利完成手术,13例患者共置入26枚螺钉;手术时间60～130min,平均80min;术中出血110~290ml,平均190ml。术中无脊髓、椎动脉损伤等并发症。术后复查CT显示1枚螺钉位置欠佳,螺钉外斜角偏小且上斜角偏大,螺钉部分进入椎管,但未损伤脊髓,未做处理;25枚位置良好。寰枢关节基本复位,固定可靠。术后随访12~60个月,平均18个月,末次随访时VAS评分降至1.0～2.0分,平均1.3分,与术前比较有统计学差异(P<0.05)。2例伴颈髓损伤患者的症状均有改善,Frankel分级C级者恢复到D级,D级者恢复到E级。12例患者术后3个月开始出现植骨融合,末次随访时寰枢关节间隙植骨均达到融合;1例患者未见明显植骨融合,但寰枢关节稳定性良好,未出现断钉等并发症。结论:内窥镜辅助下前路经寰枢关节螺钉固定植骨融合术治疗上颈椎不稳是可行的,能取得较好的治疗效果,且在一定程度上克服了传统手术显露困难的缺点,从而减少手术并发症。     

CT evaluation of upper thoracic spine for surgical application of transarticular screw placement

Introduction

Although pedicle screw fixation has been increasingly used in the upper thoracic spine in recent years, controversies exist about the safety and complications such as nerve or vascular intrusion associated with the technique. In this study, an alternative method of transarticular screw fixation was validated.

Materials and methods

Morphometric analysis was performed on computed tomography (CT) scans of the upper thoracic zygapophysial joints of C7, T1, T2 and T3 in 20 male and 20 female patients in the axial and sagittal planes. The degree of screw angulation was recorded in the sagittal and axial planes and the screw length was measured at the spinal level from C7 to T3.

Results

The smallest medial–lateral diameter and anterior–posterior diameter of IAP was found at T3 in the female patients and C7 in the male patients. The screw trajectory length ranged from 14.9 to 20.5 mm in all patients. All the above measurements were significantly different between male and female patients at all levels (P < 0.05). The mean value of screw trajectory angle was 19.3°–20.1° in the axial plane and 44.3°–45.7° in the sagittal plane. There was no statistically significant difference (P > 0.05) between male and female patients in the axial and sagittal angles.

Conclusion

The morphometric data of C7–T3 zygapophysial joints indicate the suitable screw diameter and screw length for this technique. Transarticular screw fixation proved to be a potentially safe alternative to pedicle screw fixation in this region.     

C2/3经关节螺钉固定的临床应用解剖研究

目的研究C2/3侧块关节螺钉固定的解剖可行性,为颈椎后路钉板固定在枢椎提供新的螺钉锚点.方法利用20例配套颈椎干骨标本,测量枢椎和第三颈椎侧块的宽度和高度.设定C2/3侧块关节螺钉的进钉点和进钉方向,即进钉点在头尾方向上位于枢椎侧块的中下1/3交界处,在内外方向上位于枢椎侧块的中央,螺钉穿枢椎侧块经由C2/3侧块关节进入C3侧块;进钉方向与人体矢状面平行,并与C2/3侧块关节面呈90°角,测量螺钉分别在枢椎和第三颈椎侧块内的长度.结果枢椎侧块的平均宽度和高度分别是14.83mm和9.63mm;第三颈椎侧块的平均宽度和高度分别是13.86mm和11.27mm.螺钉在枢椎和第三颈椎侧块内的平均长度分别是6.24mm和9.70mm,螺钉总长平均15.94mm.结论经C2/3侧块关节进行螺钉固定在解剖学上是可行的,可以作为枢椎后路螺钉固定的补充方法.     

寰枢椎前路侧块螺钉内固定的生物力学测试

目的比较寰枢椎前路侧块螺钉和前路钛网、前路钢板内固定后颈椎标本的稳定性,分析不同前路内固定方法对寰枢椎各个方向运动的控制作用,为临床选择应用提供参考。方法 5具新鲜冷冻保存的尸体标本,快速分离出C0～T1节段,去除表面肌肉组织,放射测定,排除骨溶解、骨折及有其他病变的标本,以自凝型牙托粉包埋C2～7节段。包埋好的标本以特殊夹具固定于三思牌测力机上进行前屈、后伸和左右侧屈刚度的测试。旋转刚度在自制的测力机上测定。结果与正常组和损伤组相比,三种内固定方法均能明显提高寰枢椎各向活动的刚度,统计检验P<0.05;术式间的比较前路螺钉组的活动刚度明显高于前路钢板(各个方向P<0.05)和前路钛网(各个方向P<0.05);前路钢板的活动刚度明显高于前路钛网(各个方向P<0.05)。结论体外颈椎标本的生物力学实验表明,无论与正常组或损伤组相比前路双侧块螺钉、前路钢板和前路钛网内固定均能提高寰枢椎的稳定性,其中前路双侧块螺钉内固定提供的稳定性最强,与简单外固定配合使用可满足临床需要,当必须行寰枢椎前路内固定时应优先考虑使用。前路钢板和前路钛网单独使用稳定性较差,虽与后路内固定术式联用或改进设计可提高稳定性,但提高了并发症风险和经济负担。     

寰枕关节后路经关节螺钉固定的解剖学研究

目的 :对 枕寰 枢 复合 体进 行 解剖 学研 究 ,为临 床 上枕 寰枢 后 路经 关节 螺 钉固 定提 供 解剖 学 依据 。 方 法 :对 100 例 中 国成 年人 枕 骨髁 和寰 椎 干燥 标本 进 行解 剖学 测 量;对 12 例 新鲜 尸体 枕 颈部 标本 进 行枕 寰 枢 后 部结构解 剖学 观 察。结 果:枕骨 髁与 寰 椎侧 块上 关 节面 咬合 成 寰枕 关节 ,枕 髁关 节 面呈 内倾 。其 中枕 髁关 节 面舌 下神经管 间距 为 9.66±1.13m m ,枕 髁 关节 面的 前 后 径 和横 径 、寰椎 侧 块 上 关节 面 前 后 径、侧 块上 关 节 面 横径 、侧 块与后弓 移行 处 侧块 厚度 均 在 5m m 以 上。新 鲜尸 体标 本 观察 发现 ,椎 动脉 第 三段 恒定 行 走于 椎动 脉 沟。第 颈 神经 1背侧 支和 第 2 颈 神经 背 侧支 与寰 椎 侧块 下关 节 突后 方几 乎 无交 叉,并有 一定 的 活动 度。 结 论:寰枕 关 节 的解 剖学形 态与 其 生物 力学 性 质密 切相 符 ;寰枕 关 节后 路经 关 节螺 钉内 固 定在 解剖 学 上是 可行 的 。     

Lateral radiological evaluation of transarticular screw placement in the lower cervical spine

This study assessed the ideal district of lateral radiograph in evaluation of transarticular screw placement in the lower cervical spine. To assess the ideal zone of lateral radiographs in determining the safe or hazardous locations of the screw tips during transarticular screw implantation in the lower cervical spine. Transarticular screw in the lower cervical spine had been used as an alternative technique to achieve posterior cervical spine stability. Injury to the spinal nerves caused by transarticular screws which are too long must be identified quickly to minimize the neurologic complication. No previous radiological study regarding evaluation of the transarticular screw placement using lateral radiographs has been reported. Twelve cervical spines were removed from embalmed cadavers. Four transarticular screw placements with Dalcanto’s technique under direct visualization, including placement of the screw tip staying the ventral cortex, 2, 4 and 6 mm over-penetration of the ventral cortex, were performed on each specimen. Following each placement, a lateral radiograph was taken. Each vertebral body was divided vertically into four equal zones, and another equal zone posterior to the posterior border of the vertebral body was defined as Zone pre-1. The numbers of screw tips seen in each zone were quantified for each placement. Partitions of χ ² method was used to evaluate the ideal zone on lateral radiograph for transarticular screw insertion. At C34 and C45, no significant difference was found between Zone pre-1 and Zone 1 (χ ² = 0.18, P > 0.50), while there was significant difference between Zones 1 and 2 (χ ² = 73.6, P < 0.005), as well as Zones 2 and 3 (χ ² = 13.2, P < 0.005). At C56 and C67, No significant difference was found between Zones 2 and 3 (χ ² = 0.25, P > 0.50), while there was significant difference between Zone pre-1 and Zone 1 (χ ² = 66.2, P < 0.005), as well as Zones 1 and 2 (χ ² = 10.5, P < 0.005). Ideal screw tip positions on lateral radiograph for transarticular screw by Dalcanto’s technique should be in Zone 1 at C34 and C45, in Zone pre-1 at C56 and C67. If the screw tip was in Zones 3 and 4, the safe rate will be decreased significantly and it might be too deep and be dangerous.