寰枢椎后路椎弓根螺钉固定的生物力学评价

目的：评价寰枢椎后路椎弓根螺钉固定的生物力学稳定性。方法：6具新鲜颈椎标本，按随机顺序，对每一标本先后行C1-C2椎弓根螺钉、Magerl螺钉、Brooks钢丝以及螺钉联合钢丝固定，在脊柱三维运动实验机上测量其三维运动范围。结果：Magerl螺钉或C1-C2椎弓根螺钉联合Brooks钢丝组成的固定系统的三维运动范围最小。C1-C2椎弓根螺钉固定的前后屈伸运动范围与Brooks钢丝固定无差异，但大于Magerl螺钉；其左右侧屈运动范围小于Brooks钢丝固定，大于Magerl螺钉；其轴向旋转角度明显小于Brooks钢丝固定，但与Magerl螺钉无统计学差异。结论：C1-C2椎弓根螺钉的三维稳定性与Magerl螺钉相当，联合Brooks钢丝固定可进一步提高其稳定性。     

寰椎侧块螺钉与寰椎椎弓根螺钉的解剖与生物力学对比研究

目的对寰椎侧块螺钉和寰椎椎弓根螺钉进行解剖和生物力学研究,为临床选择寰椎螺钉的固定方式提供依据。方法利用12例新鲜标本的寰椎进行单皮质和双皮质的椎弓根螺钉或侧块螺钉固定,测试比较其螺钉拔出强度和钉道长度。结果寰椎椎弓根螺钉的最大进钉长度为29·79mm±1·68mm,其中10·15mm在寰椎后弓内,19·65mm在寰椎侧块内。寰椎侧块螺钉的最大进钉长度为24·88mm±0·41mm,其进钉点与寰椎后弓后缘的平均距离为9·93mm±1·35mm。双皮质寰椎椎弓根螺钉的拔出力量最大,平均1757·0N±318·7N;单皮质寰椎椎弓根螺钉(1192·5N±172·6N)与双皮质寰椎侧块螺钉(1243·8N±350·0N)无明显差异,单皮质寰椎侧块螺钉最小(794·5N±314·8N)。结论在同时适用寰椎椎弓根螺钉和寰椎侧块螺钉固定的患者,宜首先选择寰椎椎弓根螺钉固定,次选寰椎侧块螺钉固定。     

单纯寰椎侧块螺钉固定选择性治疗不稳定寰椎骨折的生物力学分析

【摘要】 目的：测试单纯寰椎侧块螺钉固定治疗不稳定寰椎骨折的生物力学稳定性,为临床应用提供理论依据。方法：取新鲜成人的完整枕骨及颈椎（C0-C3）标本6具,聚甲基丙烯酸甲酯包埋,在电子生物力学试验机上分别测定完整标本（A组）,寰椎骨折合并横韧带离断+寰椎侧块螺钉固定（B组）,横韧带、纵向韧带离断+寰椎侧块螺钉固定（C组）的前屈/后伸、左/右侧屈的运动变化以及前屈时C1-2的相对位移ADI（atlantodental interval）值,进行统计学分析,评价单纯寰椎侧块螺钉固定治疗不稳定寰椎骨折的生物力学稳定性,分析上颈椎韧带复合体的生物力学作用。结果：寰椎横韧带切断内固定后,载荷为50~90N时,A组与B组的ADI值、前屈、后伸相比,无统计学差异（P＞0.05）;当载荷为100N时,B组ADI值2.76mm、前屈11.66°、后伸14.05°,载荷为150N时,B组ADI值3.15mm、前屈15.27°、后伸16.25°,与A组相比均有统计学差异（P＜0.05）。横韧带切断后,载荷小于100N时,B组左、右侧屈与A组比较差异均无统计学意义（P＞0.05）;载荷100N时,B组左侧屈7.51°,与A组比较差异无统计学意义（P＞0.05）,B组右侧屈8.43°,与A组相比存在统计学差异（P＜0.05）;载荷150N时,B组左侧屈8.79°、右侧屈10.67°,与A组比较均有统计学差异（P＜0.05）。进一步切断纵向韧带,稳定性明显丧失,C组的ADI值和前屈、后伸、左右侧屈范围与A组相比均有显著统计学差异（P＜0.05）。结论：单纯寰椎侧块螺钉固定治疗寰椎骨折,恢复C0-2之间的高度,即恢复纵向韧带的张力能够维持生理载荷下寰枢椎的稳定性。     

颈椎椎弓根皮质骨螺钉固定的钉道影像学测量与生物力学研究测试

目的:探讨颈椎椎弓根皮质骨螺钉在临床使用可行性、钉道的参数和置钉后生物力学分析.方法:随机选取我院2014年1月～2018年6月住院行颈椎CT三维重建的住院患者CT资料30例,男性16例,女性14例,年龄30～60岁(48.0±5.6岁),采集患者颈椎(选取C4～C6)CT连续扫描数据,测量每个椎弓根的形态学数据:椎弓...     

枢椎椎板螺钉联合寰椎椎弓根螺钉固定治疗寰枢椎脱位

目的 评价枢椎椎板螺钉联合寰椎椎弓根螺钉固定融合治疗寰枢椎脱位的临床可行性.方法 对5例枢椎椎弓根细小的寰枢椎脱位患者,在气管插管全身麻醉下施行了枢椎椎板螺钉联合寰椎椎弓根螺钉固定术.枢椎椎板螺钉的进钉点位于棘突两侧椎板交界处,交叉置人对侧椎板内;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3 mm,内斜10°,上斜5°.螺钉直径3.5 mm,枢椎椎板螺钉长26～32 mm,寰椎椎弓根螺钉长28～32 mm,结合自体髂骨植骨.结果 患者获得随访3～18个月,平均7.5个月.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,X线、CT复查螺钉位置良好,无松动、断钉,植骨3个月后均达到满意融合.结论 枢椎椎板螺钉联合寰椎椎弓根螺钉固定治疗寰枢椎脱位效果满意,是又一可供选择的寰枢椎后路固定术式.     

枢椎后路3种螺钉固定技术生物力学测试的对比研究

目的：评价单皮质和双皮质枢椎椎弓根螺钉、枢椎侧块螺钉和枢椎椎板螺钉的固定强度,为临床选择后路螺钉的固定方式提供生物力学依据。方法：利用30具新鲜尸体枢椎标本,进行单皮质和双皮质的枢椎椎弓根螺钉、枢椎侧块螺钉、枢椎椎板螺钉固定,测试比较其螺钉拔出强度。结果：双皮质枢椎椎弓根螺钉的拔出力量最大,为（1255.8±381.9）N;单皮质枢椎椎弓根螺钉[（901.8±373.3）N]、双皮质枢椎侧块螺钉[（776.1±306.8）N]和双皮质枢椎椎板螺钉[（640.8±302.9）N]之间差异无统计学意义。结论：枢椎后路螺钉固定宜首选椎弓根螺钉,枢椎侧块螺钉和枢椎椎板螺钉可作为枢椎后路补充固定技术,且以双皮质骨固定为宜。     

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.     

寰椎经后弓侧块螺钉和寰椎侧块螺钉固定技术治疗寰枢椎失稳的前瞻性自身对照研究

[摘要]目的：评估寰椎经后弓侧块螺钉和寰椎侧块螺钉固定技术的临床疗效和应用价值。方法：2006年6月～2011年2月,对66例寰枢椎失稳的患者随机选择一侧寰椎经后弓侧块螺钉固定和一侧经寰椎侧块螺钉固定结合枢椎椎弓根螺钉固定进行治疗。通过寰椎螺钉置钉操作的手术时间、失血量、术中并发症、日本骨科协会（JOA）评分、疼痛视觉模拟（VAS）评分和术后内固定稳定情况评定疗效。     

寰枢椎椎弓根螺钉固定的研究进展

寰椎椎弓根螺钉固定技术．即通常所说的经寰椎后弓侧块螺钉固定技术，与寰椎侧块螺钉固定技术不是等同的概念。有很多文献将其混淆。寰椎椎弓根螺钉固定技术由Resnick等于2002年首次提出．用于治疗齿状突骨折引起的寰枢椎不稳。枢椎椎弓根螺钉固定技术首先由Leconte于1964年用于枢椎创伤性滑脱的治疗。近年来在寰枢椎后路内固定术中寰枢椎椎弓根螺钉固定技术发展越来越快，     

后路寰枢椎经关节螺钉结合寰椎椎板钩与寰枢椎椎弓根螺钉固定融合治疗寰枢椎脱位的疗效比较

目的:比较后路寰枢椎经关节螺钉结合寰枢椎板钩固定融合与寰枢椎椎弓根螺钉固定融合治疗可复性寰枢椎脱位的临床疗效。方法:回顾性分析2006年6月~2012年3月行寰枢椎经关节螺钉结合寰椎椎板钩固定融合治疗的74例可复性寰枢椎脱位患者(钉钩组)的临床资料,以同时期相同纳入标准采用后路寰枢椎椎弓根螺钉固定融合治疗的63例患者(钉棒组)作为对照。记录术前疼痛视觉模拟量表(VAS)评分、脊髓功能(ASIA分级)、颈部僵硬度、颈椎功能障碍指数(NDI)、术中出血量、手术时间。以末次随访时植骨融合率、VAS评分、ASIA分级、NDI、颈部僵硬度及患者满意度评价治疗效果,并比较两组间的临床疗效。结果:两组患者的年龄、性别比和术前VAS评分、NDI、ASIA分级差异均无统计学意义(P0.05),具有可比性。钉钩组随访时间为76.3±14.0(48~110)个月,平均手术时间为126.1±8.6min,平均术中出血量为207.8±34.2ml,植骨融合率为100%,平均融合时间为4.6±0.9个月;钉棒组随访时间为72.0±12.0(48~96)个月、平均手术时间为129.8±7.9min,平均术中出血量为225.8±30.0ml,植骨融合率为98%,平均融合时间为4.8±1.2个月。两组随访时间、手术时间、植骨融合率和融合时间的差异均无统计学意义(P0.05),钉钩组的平均术中出血量与钉棒组比较差异有统计学意义(P0.05)。两组患者末次随访时VAS评分、NDI和颈部僵硬度均较术前降低(P0.05)。有神经症状的患者,钉钩组的49例与钉棒组的37例末次随访时ASIA分级较术前提高1~2级。末次随访时,VAS评分、ASIA分级、颈部僵硬度、患者满意度及NDI两组间差异均无统计学意义(P0.05)。结论:后路寰枢椎经关节螺钉结合寰椎椎板钩固定融合与寰枢椎椎弓根螺钉固定融合治疗可复性寰枢椎脱位均能达到满意的临床疗效,但前者术中出血量更少。     

枢椎椎板螺钉与椎弓根螺钉抗拔出强度的比较

目的:比较枢椎椎板螺钉与枢椎椎弓根螺钉的抗拔出强度,为临床应用枢椎椎板螺钉固定提供生物力学依据。方法:在7具成年男性新鲜尸体枢椎标本上进行枢椎单皮质椎弓根螺钉和双皮质椎板螺钉固定,测试螺钉拔出力。结果:单皮质枢椎椎弓根螺钉的最大拔出力平均为875.3±403.2N,双皮质枢椎椎板螺钉的最大拔出力平均为679.5±308.2N;椎弓根螺钉的最大拔出力大于椎板螺钉,但二者之间无统计学差异。结论:枢椎椎板螺钉进行双皮质固定具有可靠的力学固定强度,可作为枢椎椎弓根螺钉的补充固定技术。     

寰椎椎弓根螺钉联合经寰枢关节螺钉内固定稳定性的生物力学研究

目的:评估寰椎椎弓根螺钉联合经寰枢关节螺钉固定技术的力学稳定性.方法:选取成人颈椎新鲜标本6具,解剖剔除肌肉制备上颈椎完整模型(完整组),用生物力学测试及计算机视觉分析软件测量在1.5Nm力矩下前屈后伸、左右侧弯和左右旋转时C 1-C2的活动度(ROM);破坏寰椎前弓和侧块制备不稳模型(失稳组),再次测量相同力矩下各运...     

新型寰椎内径锥形螺钉的设计与拔出力的测试

目的比较两种设计的寰椎椎弓根钉的最大拔出力,为临床选择寰椎推弓根钉类型提供生物力学依据。方法设计制作两种寰椎椎弓根钉,根据螺纹部分分为皮质骨螺钉(A型螺钉)、内径锥形螺钉(B型螺钉),利用24节新鲜猪寰椎标本,置入两种类型的椎弓根钉,进行拔出试验,测定每种螺钉的最大拔出力,进行统计学分析比较。结果同一长度,不同设计的螺钉抗拔出力接近,均无显著性差异;同一直径两种设计的螺钉,28 mm比26 mm的抗拔出力略大,但均无显著性差异。结论新型寰椎内径锥形螺钉(3.0 mm)抗拔力高,螺钉根部强度好,抗弯曲、断裂性能好,可提供足够的即刻稳定性,是寰椎椎弓根固定的理想螺钉类型。     

寰椎后弓变异患者寰椎椎弓根螺钉的置钉策略

目的:探讨寰椎后弓变异患者寰椎椎弓根螺钉的置钉方法及其安全性.方法:回顾性分析2005年1月～2011年1月寰椎后弓变异行寰椎椎弓根螺钉固定的28例患者,其中男11例,女17例;年龄6～75岁,平均36.2±15.5岁.根据CT重建图像将寰椎椎弓根划分为后弓表面、椎动脉沟底和椎弓根侧块交界区3个切面,并将每个切面再分为内侧、外侧2个部分.对各部位相应切面的后弓高度进行测量,根据所测结果,将变异寰椎后弓分为3种类型,并采用相应的椎弓根螺钉置钉方法:Ⅰ型(寰椎后弓表面高度＜3.5mm,椎动脉沟底椎弓根高度＞3.5mm),采取后弓下置钉;Ⅱ型(后弓表面高度及椎动脉沟底椎弓根高度均＜3.5mm),采取椎弓根侧块交界点处置钉;Ⅲ型(后弓表面高度＞3.5mm,椎动脉沟底椎弓根高度＜3.5mm),采取in-out-in技术置钉.术后采用CT片评价置钉准确性,并观察并发症发生情况.结果:56个寰椎后弓变异的椎弓根中,Ⅰ型34个,Ⅱ型18个,Ⅲ型4个.术中成功置钉54枚,成功率96.4％;2个Ⅱ型变异后弓椎弓根(2例一侧)因椎弓根过小无法置钉而改用椎板钩固定.术后CT显示理想和可接受置钉52枚(96.3％);不可接受置钉2枚(3.7％),均表现为螺钉穿入椎管.2例患者术后出现枕大神经刺激症状,1例经对症处理、1例拆除内固定后症状缓解.术中与术后均未发生大出血,无椎动脉、神经根及脊髓损伤,无寰椎后弓骨折等其他并发症.结论:寰椎后弓变异患者仍可采用寰椎椎弓根螺钉固定,在实施时应根据不同分型采用相应的置钉策略.     

Biomechanical advantage of C1 pedicle screws over C1 lateral mass screws: a cadaveric study

Purpose

The established technique for posterior C1 screw placement is via the lateral mass. Use of C1 monocortical pedicle screws is an emerging technique which utilizes the bone of the posterior arch while avoiding the paravertebral venous plexus and the C2 nerve root. This study compared the relative biomechanical fixation strengths of C1 pedicle screws with C1 lateral mass screws.

Methods

Nine human C1 vertebrae were instrumented with one lateral mass screw and one pedicle screw. The specimens were subjected to sinusoidal, cyclic (0.5 Hz) fatigue loading. Peak compressive and tensile forces started from ±25 N and constantly increased by 0.05 N every cycle. Testing was stopped at 5 mm displacement. Cycles to failure, displacement, and initial and end stiffness were measured. Finally, CT scans were taken and the removal torque measured.

Results

The pedicle screw technique consistently and significantly outperformed the lateral mass technique in cycles to failure (1,083 ± 166 vs. 689 ± 240 cycles), initial stiffness (24.6 ± 3.9 vs. 19.9 ± 3.2 N/mm), end stiffness (16.6 ± 2.7 vs. 11.6 ± 3.6 N/mm) and removal torque (0.70 ± 0.78 vs. 0.13 ± 0.09 N m). Only 33 % of pedicle screws were loose after testing compared to 100 % of lateral mass screws.

Conclusions

C1 pedicle screws were able to withstand higher toggle forces than lateral mass screws while maintaining a higher stiffness throughout and after testing. From a biomechanical point of view, the clinical use of pedicle screws in C1 is a promising alternative to lateral mass screws.     

Cervical anterior transpedicular screw fixation (ATPS)—Part II. Accuracy of manual insertion and pull-out strength of ATPS

Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications in a previous study in Part I of our project. Consequently, the objectives of the current study were to assess the ex vivo accuracy of placing ATPS into the cervical vertebra as well as the biomechanical performance of ATPS in comparison to traditional vertebral body screws (VBS) in terms of pull-out strength (POS). Twenty-three ATPS were inserted alternately to two screws into the pedicles and vertebral bodies, respectively, of six cadaveric specimens from C3–T1. For insertion of ATPS, a manual fluoroscopically assisted technique was used. Pre- and post insertional CT-scans were used to assess accuracy of ATPS insertion in the axial and sagittal planes. A newly designed grading system and accuracy score were used to delineate accuracy of ATPS insertion. Following insertion of screws, 23 ATPS and 22 VBS were subjected to pull-out testing (POT). The bone mineral density (BMD) of each specimen was assessed prior to POT. Statistical analysis showed that the incidence of correctly placed screws and non-critical pedicles breaches in axial plane was 78.3%, and 95.7% in sagittal plane. Hence, according to our definition of “critical” pedicle breach that exposes neurovascular structures at risk, 21.7% (n = 5) of all ATPS inserted showed a critical pedicle breach in axial plane. Notably, no critical pedicle perforation occurred at the C6 to T1 levels. Pull-out testing of ATPS and VBS revealed that pull-out resistance of ATPS was 2.5-fold that of VBS. Mean POS of 23 ATPS with a mean BMD of 0.566 g/cm² and a mean osseus screw purchase of 27.2 mm was 467.8 N. In comparison, POS of 22 VBS screws with a mean BMD of 0.533 g/cm² and a mean osseus screw purchase of 16.0 mm was 181.6 N. The difference in ultimate pull-out strength between the ATPS and VBS group was significant (p < 0.000001). Also, accuracy of ATPS placement in axial plane was shown to be significantly correlated with POS. In contrast, there was no correlation between screw-length, BMD, or level of insertion and the POS of ATPS or VBS. The study demonstrated that the use of ATPS might be a new technique worthy of further investigation. The use of ATPS shows the potential to increase construct rigidity in terms of screw-plate pull-out resistance. It might diminish construct failures during anterior-only reconstructions of the highly unstable decompressed cervical spine. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biomechanical analysis of anterior cervical spine plate fixation systems with unicortical and bicortical screw purchase

Anterior plate fixation with unicortical screw purchase does not involve the risk of posterior cortex penetration and possible injuries of the spinal cord. However, there are very few biomechanical data about the immediate stability of non-locking plate fixation with unicortical or bicortical screw placement. The aim of the present study was to evaluate the immediate biomechanical properties in terms of flexibility of a non-locking anterior plate system with 4.5-mm screw fixation and unicortical or bicortical screw purchase applied to a single destabilized cervical spine motion segment. Using fresh cadaveric cervical spine specimens C3-C7, multidirectional flexibility was measured at the level C4-C5 before and after destabilization and fixation with an anterior plate with either unicortical or bicortical screw purchase. The results showed that fixed cervical spine segments with anterior plate and bicortical screw purchase were more rigid than intact specimens in all modes of testing. The difference was statistically significant for flexion and extension (P<0.001). Plate fixation with unicortical screw purchase had statistically significant decreased ranges of motion compared to the intact specimen only in extension. Neither unicortical nor bicortical screw purchase decreased the range of motion significantly in axial rotation compared to the intact specimens. This in vitro study documented that neither unicortical nor bicortical screw purchase with non-locking plate fixation can increase stability in all modes of testing, in axial rotation in particular. Direct comparison between the group with uni- and that with bicortical screw fixation did not reveal significant differences, and therefore no advantage was shown for either type of screw fixation. Therefore, we demonstrated that both uni- and bicortical screw purchase with non-locking plate fixation can decrease immediate flexibility of the tested motion segment, with better results for bicortical purchase. No significant differences were found comparing the two groups of screw fixation. These data suggest that unicortical screw fixation can be used for anterior plate fixation with a comparable immediate stability to bicortical screw fixation.Supported by the German Research Foundation, DFG, Bonn, Germany     

Biomechanical comparison of unicortical versus bicortical C1 lateral mass screw fixation

STUDY DESIGN: Biomechanical study of pullout strength of unicortical versus bicortical C1 lateral mass screws using a cadaveric cervical spine model. OBJECTIVE: To compare pullout strength of unicortical versus bicortical C1 lateral mass screws. SUMMARY OF BACKGROUND DATA: The internal carotid artery and hypoglossal nerve lie over the anterior aspect of the lateral mass of the atlas and are at risk from bicortical C1 lateral mass screws. Unicortical screws would reduce the risk of injury to these neurovascular structures; however, no data are available on the relative strength of unicortical versus bicortical C1 lateral mass screws. METHODS: Fifteen cadaveric cervical spine specimens underwent axial pullout testing of C1 lateral mass screws. A unicortical C1 lateral mass screw was placed on 1 side with a contralateral bicortical screw. RESULTS: The mean pullout strengths of the unicortical screws and bicortical screws were 588 N (range, 212 to 1234 N) and 807 N (range, 163 to 1460 N), respectively (P=0.008). CONCLUSIONS: Bicortical C1 lateral mass screws were significantly stronger than unicortical screws; however, the mean pullout strength of both the unicortical and bicortical C1 screws were greater than previously reported values for subaxial lateral mass screws. On the basis of these data, the clinical necessity for using bicortical screw fixation in all patients must be questioned. If similar strength can be achieved using unicortical C1 lateral mass screw to that currently accepted in the subaxial spine, bicortical screws might not be justified for the C1 lateral mass. However, the ability to extrapolate C1-C2 data to subaxial spine data is uncertain because of the difference in normal physiologic loading at these levels.