以有限元法比较前路腰椎间融合后路关节突关节螺钉/椎弓根螺钉的固定应力*☆

背景：对腰椎前路腰椎间融合后辅助固定的各种关节突关节螺钉的生物力学安全性存在普遍担忧,限制其临床应用,未见文献报道与椎弓根螺钉固定的比较研究。 目的：建立L4~5椎前路椎间融合后路分别用双侧椎弓根螺钉、经椎板关节突螺钉及经关节突椎弓根螺钉固定的三维有限元模型,施加相同的负荷和转矩,比较分析3种螺钉和椎间融合器的应力状况。 设计、时间及地点：对比观察,于2008-02/2009-01在南方医科大学珠江医院骨科实验室完成。 材料：PHILIPS Brilliance64排螺旋CT扫描仪,数据输出DICOM 3.0 格式;Mimics 11.1软件;Simpleware3.1软件;Abaqus6.8软件;Photoshop 7.0软件;DEPUY AcroMed皮质骨螺钉和Zimmer椎间融合器;GSS椎弓根螺钉系统。 方法：建立L4~5椎前路椎间融合后路分别用双侧椎弓根螺钉、经椎板关节突螺钉及经关节突椎弓根螺钉固定的三维有限元模型。对3种螺钉固定的有限元模型施加500 N/6 N•m载荷模拟前曲、后伸、左侧弯、左旋运动,用Abaqus 6.8软件比较分析3种螺钉和椎间融合器的应力变化和分布特点。 主要观察指标：应力峰值,应力集中区云图。 结果：在500 N/6 N•m载荷下,椎弓根螺钉在屈、伸时的应力较两种关节突关节螺钉固定应力小,在侧弯和轴向旋转时较大;两种关节突关节螺钉应力特点相似。在椎弓根螺钉坚强固定时,椎间融合器有应力遮挡现象。 结论：在较小的转矩下,前路腰椎间融合后两种关节突关节螺钉固定的安全性和椎弓根螺钉固定相近。使用关节突关节螺钉固定,除减少创伤、节约成本等优点外,还可减少对椎间融合器的应力遮挡效应。     

自发性寰枢关节脱位后路复位内固定术中枢椎椎弓根螺钉置入不能时的备选方法

目的探讨自发性寰枢关节脱位后路内固定过程中枢椎椎弓根螺钉置入不能时,其他备选螺钉内固定技术的安全性及有效性。方法对贵州省人民医院神经外科未采用枢椎椎弓根螺钉内固定治疗的11例自发性寰枢关节脱位患者的临床资料进行回顾性分析。在枢椎椎弓根螺钉置入不能时,采用枢椎椎板螺钉、峡部螺钉、枢椎下关节突螺钉及延长固定节段至C3侧块螺钉来增加稳定性的方法。手术前后分别行CT及MRI检查,评价脊髓受压程度、脱位复位情况、螺钉位置、骨融合情况;通过比较术前、术后日本骨科协会(JOA)评分来评价疗效。结果 11例患者均为枢椎椎弓根置钉不能,改用备选方法置钉,全部行枕颈钉棒内固定。共置入枢椎椎板锣钉14枚,枢椎峡部螺钉5枚,枢椎下关节突螺钉1枚,延长固定节段至C3侧块螺钉4枚。术中均未发生椎动脉和脊髓神经根损伤。11例患者的寰枢关节脱位均得到不同程度的复位,随访中无患者出现螺钉松动、滑脱、断钉及复位丢失等情况,JOA评分为显著增加。结论对自发性寰枢关节脱位后路内固定过程中枢椎椎弓根螺钉置入不能时,可根据情况,个性化选用枢椎椎板螺钉、峡部螺钉、枢椎下关节突螺钉及延长固定节段至C3侧块螺钉的方法来固定,是可行且有效的。     

椎间融合器植入并双侧下关节突切除治疗退变性腰椎管狭窄症

背景：对退变性腰椎管狭窄治疗可行全椎板减压内固定置入、单侧或双侧开窗减压、后路全椎板减压等方法。但采取何种方式治疗中是否需行椎间融合器植入内固定目前还没有定论。 目的：评价以cage椎间植骨融合椎弓根内植入固定并腰后路全椎板及双侧下关节突切除减压、自体小关节骨质移植治疗退变性腰椎管狭窄症的效果。 方法：选择经3个月保守治疗无效的退变性腰椎管狭窄症患者41例,男23例,女18例,平均年龄60.3岁,行腰后路全椎板及双侧下关节突切除减压、自体小关节骨质及cage椎间植骨融合植入椎弓根内固定治疗,随访24个月,术前及术后随访时JOA评分评价患者疗效,放射学检查患者植骨融合情况及手术节段椎体稳定性。 结果与结论：随访时JOA评分较术前有明显提高(P < 0.01),临床优良率为90%;40例获得骨性融合,融合率98%,1例患者有腰椎不稳征象。术后均无内固定物松动、断裂等并发症发生,但有2例发生硬脊膜撕裂,1例发生椎弓根位置偏斜,1例假关节形成。结果提示腰后路全椎板及双侧下关节突切除减压、自体小关节骨质及cage椎间植骨融合植入椎弓根内固定治疗退变性腰椎管狭窄症具有良好的临床效果。     

单纯后路复位及固定治疗自发性寰枢椎脱位

目的 利用单纯后路复位,同时行内固定治疗寰枢椎脱位的方法,既不需要颅骨牵引,也不需经口腔齿状突切除.方法 2004年5月至2007年12月,收治自发性寰枢椎脱位病人20例,手术前后利用CT及MRI进行影像学测量,评价脱位及脊髓延髓受压程度.根据是否合并寰枕融合分别采用C1侧块～C2椎弓根螺钉技术3例及C2椎弓根～枕骨螺钉技术17例.手术中向前推压C2棘突或通过C2椎弓根及枕骨螺钉间撑开将齿状突向前、下牵拉以恢复齿状突与C1前弓的解剖关系.结果 20例病人随访6-48个月,1例术后1周因基底动脉内血栓形成死亡,其余19例均明显改善.手术后影像学检查见脊髓延髓均获彻底减压,合并脊髓空洞的5例病人,空洞均明显缩小;各项影像学测量指标均明显好转(P<0.01).1例于术后3个月时CT提示复位部分丢失,但螺钉位置良好,脊髓延髓减压良好,脊髓空洞继续缩小,6个月时骨性融合.结论 首先选择后路复位及固定,而不是前路经口腔齿状突切除减压,是治疗寰枢椎脱位简单有效,相对安全的方法.     

单纯后路复位及固定治疗自发性寰枢椎脱位

目的 利用单纯后路复位,同时行内固定治疗寰枢椎脱位的方法,既不需要颅骨牵引,也不需经口腔齿状突切除.方法 2004年5月至2007年12月,收治自发性寰枢椎脱位病人20例,手术前后利用CT及MRI进行影像学测量,评价脱位及脊髓延髓受压程度.根据是否合并寰枕融合分别采用C1侧块～C2椎弓根螺钉技术3例及C2椎弓根～枕骨螺钉技术17例.手术中向前推压C2棘突或通过C2椎弓根及枕骨螺钉间撑开将齿状突向前、下牵拉以恢复齿状突与C1前弓的解剖关系.结果 20例病人随访6-48个月,1例术后1周因基底动脉内血栓形成死亡,其余19例均明显改善.手术后影像学检查见脊髓延髓均获彻底减压,合并脊髓空洞的5例病人,空洞均明显缩小;各项影像学测量指标均明显好转(P<0.01).1例于术后3个月时CT提示复位部分丢失,但螺钉位置良好,脊髓延髓减压良好,脊髓空洞继续缩小,6个月时骨性融合.结论 首先选择后路复位及固定,而不是前路经口腔齿状突切除减压,是治疗寰枢椎脱位简单有效,相对安全的方法.     

单纯后路复位及固定治疗自发性寰枢椎脱位

目的 利用单纯后路复位,同时行内固定治疗寰枢椎脱位的方法,既不需要颅骨牵引,也不需经口腔齿状突切除.方法 2004年5月至2007年12月,收治自发性寰枢椎脱位病人20例,手术前后利用CT及MRI进行影像学测量,评价脱位及脊髓延髓受压程度.根据是否合并寰枕融合分别采用C1侧块～C2椎弓根螺钉技术3例及C2椎弓根～枕骨螺钉技术17例.手术中向前推压C2棘突或通过C2椎弓根及枕骨螺钉间撑开将齿状突向前、下牵拉以恢复齿状突与C1前弓的解剖关系.结果 20例病人随访6-48个月,1例术后1周因基底动脉内血栓形成死亡,其余19例均明显改善.手术后影像学检查见脊髓延髓均获彻底减压,合并脊髓空洞的5例病人,空洞均明显缩小;各项影像学测量指标均明显好转(P<0.01).1例于术后3个月时CT提示复位部分丢失,但螺钉位置良好,脊髓延髓减压良好,脊髓空洞继续缩小,6个月时骨性融合.结论 首先选择后路复位及固定,而不是前路经口腔齿状突切除减压,是治疗寰枢椎脱位简单有效,相对安全的方法.     

单纯后路复位及固定治疗自发性寰枢椎脱位

目的 利用单纯后路复位,同时行内固定治疗寰枢椎脱位的方法,既不需要颅骨牵引,也不需经口腔齿状突切除.方法 2004年5月至2007年12月,收治自发性寰枢椎脱位病人20例,手术前后利用CT及MRI进行影像学测量,评价脱位及脊髓延髓受压程度.根据是否合并寰枕融合分别采用C1侧块～C2椎弓根螺钉技术3例及C2椎弓根～枕骨螺钉技术17例.手术中向前推压C2棘突或通过C2椎弓根及枕骨螺钉间撑开将齿状突向前、下牵拉以恢复齿状突与C1前弓的解剖关系.结果 20例病人随访6-48个月,1例术后1周因基底动脉内血栓形成死亡,其余19例均明显改善.手术后影像学检查见脊髓延髓均获彻底减压,合并脊髓空洞的5例病人,空洞均明显缩小;各项影像学测量指标均明显好转(P<0.01).1例于术后3个月时CT提示复位部分丢失,但螺钉位置良好,脊髓延髓减压良好,脊髓空洞继续缩小,6个月时骨性融合.结论 首先选择后路复位及固定,而不是前路经口腔齿状突切除减压,是治疗寰枢椎脱位简单有效,相对安全的方法.     

单纯后路复位及固定治疗自发性寰枢椎脱位

目的 利用单纯后路复位,同时行内固定治疗寰枢椎脱位的方法,既不需要颅骨牵引,也不需经口腔齿状突切除.方法 2004年5月至2007年12月,收治自发性寰枢椎脱位病人20例,手术前后利用CT及MRI进行影像学测量,评价脱位及脊髓延髓受压程度.根据是否合并寰枕融合分别采用C1侧块～C2椎弓根螺钉技术3例及C2椎弓根～枕骨螺钉技术17例.手术中向前推压C2棘突或通过C2椎弓根及枕骨螺钉间撑开将齿状突向前、下牵拉以恢复齿状突与C1前弓的解剖关系.结果 20例病人随访6-48个月,1例术后1周因基底动脉内血栓形成死亡,其余19例均明显改善.手术后影像学检查见脊髓延髓均获彻底减压,合并脊髓空洞的5例病人,空洞均明显缩小;各项影像学测量指标均明显好转(P<0.01).1例于术后3个月时CT提示复位部分丢失,但螺钉位置良好,脊髓延髓减压良好,脊髓空洞继续缩小,6个月时骨性融合.结论 首先选择后路复位及固定,而不是前路经口腔齿状突切除减压,是治疗寰枢椎脱位简单有效,相对安全的方法.     

单纯后路复位及固定治疗自发性寰枢椎脱位

目的 利用单纯后路复位,同时行内固定治疗寰枢椎脱位的方法,既不需要颅骨牵引,也不需经口腔齿状突切除.方法 2004年5月至2007年12月,收治自发性寰枢椎脱位病人20例,手术前后利用CT及MRI进行影像学测量,评价脱位及脊髓延髓受压程度.根据是否合并寰枕融合分别采用C1侧块～C2椎弓根螺钉技术3例及C2椎弓根～枕骨螺钉技术17例.手术中向前推压C2棘突或通过C2椎弓根及枕骨螺钉间撑开将齿状突向前、下牵拉以恢复齿状突与C1前弓的解剖关系.结果 20例病人随访6-48个月,1例术后1周因基底动脉内血栓形成死亡,其余19例均明显改善.手术后影像学检查见脊髓延髓均获彻底减压,合并脊髓空洞的5例病人,空洞均明显缩小;各项影像学测量指标均明显好转(P<0.01).1例于术后3个月时CT提示复位部分丢失,但螺钉位置良好,脊髓延髓减压良好,脊髓空洞继续缩小,6个月时骨性融合.结论 首先选择后路复位及固定,而不是前路经口腔齿状突切除减压,是治疗寰枢椎脱位简单有效,相对安全的方法.     

单纯后路复位及固定治疗自发性寰枢椎脱位

目的 利用单纯后路复位,同时行内固定治疗寰枢椎脱位的方法,既不需要颅骨牵引,也不需经口腔齿状突切除.方法 2004年5月至2007年12月,收治自发性寰枢椎脱位病人20例,手术前后利用CT及MRI进行影像学测量,评价脱位及脊髓延髓受压程度.根据是否合并寰枕融合分别采用C1侧块～C2椎弓根螺钉技术3例及C2椎弓根～枕骨螺钉技术17例.手术中向前推压C2棘突或通过C2椎弓根及枕骨螺钉间撑开将齿状突向前、下牵拉以恢复齿状突与C1前弓的解剖关系.结果 20例病人随访6-48个月,1例术后1周因基底动脉内血栓形成死亡,其余19例均明显改善.手术后影像学检查见脊髓延髓均获彻底减压,合并脊髓空洞的5例病人,空洞均明显缩小;各项影像学测量指标均明显好转(P<0.01).1例于术后3个月时CT提示复位部分丢失,但螺钉位置良好,脊髓延髓减压良好,脊髓空洞继续缩小,6个月时骨性融合.结论 首先选择后路复位及固定,而不是前路经口腔齿状突切除减压,是治疗寰枢椎脱位简单有效,相对安全的方法.     

Screw fixation of craniocervical junction

In recent years an increase has been observed of the use of screw techniques for the fixation of the craniocervical junction. For clinical use two techniques have been introduced: (1) transarticular screw fixation, and (2) transpedicular screw fixation. In the former the screw is inserted through the C2 lateral mass, the fissure of the C1-C2 joint, and the C1 lateral mass. (2) in the latter the screw is inserted into the C2 pedicle and anchored in C2 vertebral body. Transarticular or pedicle screws can be easily connected to longitudinal elements such as rods or plates, and combined with lateral mass screws of the remaining cervical vertebrae or occipital screws. In comparison to sublaminar wiring or interlaminar clamping the screw techniques: (a) strengthen the stiffness of the construct and speed up fusion, (b) allow fixation in the absence or deficiency of laminae as a result of trauma or laminectomy, and (c) can selectively include only the affected segments. Increased construct stiffness is due to deep anchorage of the screw in bone providing thus a solid grip on the vertebra. Both techniques require preoperative assessment of the course of the vertebral artery using imaging methods. In about 18% of cases abnormal course of the artery precludes screw use. Pedicle screw insertion requires direct control of the medial and superior walls of C2 pedicle with dissector introduced into the vertebral canal, which requires removal of the atlantoaxial ligament. Additional control can be achieved with lateral fluoroscopy. The entry point for transarticular screw is on the lateral mass of the odontoid 2-3 mm laterally to the medial margin of C2 facet and 2-3 mm above the C1/C2 articular fissure. The screw trajectory is 0-10 degrees in horizontal plane and towards the anterior C1 tuberculum in sagittal plane.     

Atlantoaxial fixation: overview of all techniques

Over the past century, steady advances have been made in fixating an unstable atlantoaxial complex. Current options for fixation of the atlantoaxial complex include posterior clamps, posterior wiring techniques, C1-C2 transarticular screw fixation, posterior C1 lateral mass screw with C2 pars or pedicle screw fixation, and anterior transoral C1 lateral mass to C2 vertebral body fixation.     

伤椎后路椎弓根螺钉置入并椎体内植骨重建胸腰椎椎体的高度

背景：后路短节段经椎弓根内固定器械可使骨折达到近似解剖复位效果,明显提高疗效,但远期随访矫形度数丢失、内固定失败等并发症较普遍。 目的：探讨经伤椎椎弓根螺钉置入固定结合经椎弓根植骨治疗胸腰椎骨折的可行性。 方法：对73例胸腰椎骨折应用椎弓根钉棒系统后路伤椎一侧椎弓根螺钉置入内固定,对侧经椎弓根通道采用自体骨和同种异体骨行椎体内植骨。 结果与结论：73例随访6个月内均获骨性愈合,脊柱植骨融合率100%,无螺钉松动、折断。1例Frankel分级C级无变化,1例D级无变化,其余患者神经功能及腰背痛明显改善;置入后6个月损伤节段后凸平均Cobb角、伤椎椎体前缘高度、椎管前后径残留程度均较治疗前明显恢复。表明经伤椎椎弓根钉置入内固定结合经椎弓根植骨治疗骨折可获得满意复位,重建椎体高度,增强脊柱的抗压稳定性,减少内固定因应力过大造成的断钉、矫正丢失等并发症。     

Inferolateral Entry Point for C2 Pedicle Screw Fixation in High Cervical Lesions

Objective

The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation.

Methods

Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle 30° to 45° toward the midline in the transverse plane and 40° to 50° cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans.

Results

There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036).

Conclusion

Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.     

椎弓根螺钉植入物断裂18例相关因素分析*

目的：分析胸腰椎骨折中椎弓根螺钉断裂的相关因素。 方法：选择2001-03/2008-03桂林医学院附属医院脊柱外科收治的胸腰段骨折行椎弓根钉内固定患者374例,其中使用不锈钢材料的246例,使用钛合金材料的128例。术后出现椎弓根钉断裂患者18例(实验组),男8例,女10例;年龄19~61岁,平均38.6岁。随机抽取18例具有可比性的未断钉治疗效果良好的患者进行对比(对照组),男9例,女9例;年龄21~57岁,平均37.5岁。阅读所有观察对象的脊柱正侧位片,测量病椎的椎间隙高度、椎弓钉位置,观察骨性融合程度和横杆使用情况。 结果：246例使用不锈钢材料的患者中12例发生断钉,断钉率4.88%。128例使用钛合金材料的患者6例发生断钉,断钉率4.69%。两者相比,差异无显著性意义(P > 0.05),提示椎弓根钉的断钉和其材料无明显关系。通过对实验组和对照组4个观察指标的分析,病椎椎间隙的高度与椎弓根钉的断钉无明显关系,但是椎弓根钉置入的位置、植入骨的骨性融合程度及是否使用横杆和椎弓根钉的断钉有明显关系。 结论：胸腰椎骨折中螺钉断裂与其材料性质无明显关系,与椎弓根钉位置﹑骨性融合程度、横杆使用等因素密切相关,是多因素共同作用的结果。     

Cage椎弓根内固定联合自体颗粒骨打压植骨的即时生物力学稳定性

背景：自体骨移植结合椎间融合器联合椎弓根螺钉常运用于椎体融合,但单纯颗粒骨打压联合椎弓根钉的临床生物力学研究报道不多。 目的：比较后路自体颗粒骨打压植骨内固定及Cage内固定的即时生物力学稳定性。 方法：利用腰椎后路附件逐级破坏和椎间盘切除制作腰椎不稳模型。12具猪腰椎标本随机分为两组：打压植骨结合椎弓根螺钉内固定组(实验组),Cage结合椎弓根螺钉内固定组(对照组)。使用脊柱三维运动测试机模拟人体对两组标本在正常、不稳、融合3个状态下进行前屈、后伸、左右侧屈、左右旋转等各个活动的生物力学测试,三维激光扫描仪测定不同载荷下不稳节段的运动范围。 结果与结论：正常状态下,两组间L2~3节段各方向运动范围差异无显著性意义(P > 0.05),说明两组标本均衡性好,具有可比性;与正常状态相比,两组不稳状态各方向运动范围亦明显增加(P < 0.05);融合后对照组L2~3节段椎间各方向运动范围均较实验组小,但差异无显著性意义(P > 0.05)。说明自体颗粒骨打压植骨内固定与Cage内固定均能明显提高脊柱的即时生物力学稳定性,而且两组对于改善脊柱稳定性无显著性差异。     

Thoracolumbar fracture dislocation: a study of 30 patients

Open reduction and wiring of the spinous processes were carried out in patients with a thoracolumbar fracture dislocation. Clinical and X-ray examinations were performed on 30 patients 5 or more years following operation. At the time of the initial examination, an anterior angulation of 30 degrees or more was noted in 18 patients, but only in 4 cases at the time of the follow-up examination. Anterior displacement of the vertebral bodies was seen in 30 patients, but it was found to be normal in 26 patients at the time of follow-up. There were 7 patients with lateral angulation of 5 degrees or more, but only 2 patients at the time of follow-up. Lateral displacement of 5 mm or more was observed in 10 patients, but only 3 patients could be seen at the time of follow-up. In comparison with spinal instrumentation with the use of large long metallic materials, wiring of the spinous processes has several advantages such as limited surgical invasion, firm fixation, no effect on spinal mobility and no need for repeat surgery for removal of metallic materials. It is an adequate alternative method for the internal fixation of rotational fracture dislocations of the thoracolumbar region of the spine, without fracture of the posterior wall of the vertebral body and pedicle fracture.     

A Computed Tomography-Based Anatomic Comparison of Three Different Types of C7 Posterior Fixation Techniques : Pedicle, Intralaminar, and Lateral Mass Screws

Objective

The intralaminar screw (ILS) fixation technique offers an alternative to pedicle screw (PS) and lateral mass screw (LMS) fixation in the C7 spine. Although cadaveric studies have described the anatomy of the pedicles, laminae, and lateral masses at C7, 3-dimensional computed tomography (CT) imaging is the modality of choice for pre-surgical planning. In this study, the goal was to determine the anatomical parameter and optimal screw trajectory for ILS placement at C7, and to compare this information to PS and LMS placement in the C7 spine as determined by CT evaluation.

Methods

A total of 120 patients (60 men and 60 women) with an average age of 51.7±13.6 years were selected by retrospective review of a trauma registry database over a 2-year period. Patients were included in the study if they were older than 15 years of age, had standardized axial bone-window CT imaging at C7, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and inner cancellous), maximal screw length, and optimal screw trajectory were measured, and the maximal screw length of the lateral mass were measured using m-view 5.4 software. Statistical analysis was performed using Student''s t-test.

Results

At C7, the maximal PS length was significantly greater than the ILS and LMS length (PS, 33.9±3.1 mm; ILS, 30.8±3.1 mm; LMS, 10.6±1.3; p<0.01). When the outer cortical and inner cancellous width was compared between the pedicle and lamina, the mean pedicle outer cortical width at C7 was wider than the lamina by an average of 0.6 mm (pedicle, 6.8±1.2 mm; lamina, 6.2±1.2 mm; p<0.01). At C7, 95.8% of the laminae measured accepted a 4.0-mm screw with a 1.0 mm of clearance, compared with 99.2% of pedicle. Of the laminae measured, 99.2% accepted a 3.5-mm screw with a 1.0 mm clearance, compared with 100% of the pedicle. When the outer cortical and inner cancellous height was compared between pedicle and lamina, the mean lamina outer cortical height at C7 was wider than the pedicle by an average of 9.9 mm (lamina, 18.6±2.0 mm; pedicle, 8.7±1.3 mm; p<0.01). The ideal screw trajectory at C7 was also measured (47.8±4.8° for ILS and 35.1±8.1° for PS).

Conclusion

Although pedicle screw fixation is the most ideal instrumentation method for C7 fixation with respect to length and cortical diameter, anatomical aspect of C7 lamina is affordable to place screw. Therefore, the C7 intralaminar screw could be an alternative fixation technique with few anatomic limitations in the cases when C7 pedicle screw fixation is not favorable. However, anatomical variations in the length and width must be considered when placing an intralaminar or pedicle screw at C7.