两种长度的颈椎椎弓根螺钉和侧块螺钉钢板系统的稳定性比较

目的比较两种长度的颈椎椎弓根螺钉和侧块螺钉钛板系统固定的三维稳定性,探讨颈椎椎弓根螺钉的适宜长度。方法18具新鲜颈椎标本,制成C4-5节段三柱损伤模型,分别用长度为20mm、28mm的椎弓根螺钉,以及AXIS侧块螺钉钢板系统三种方法固定,测试它们在前屈、后伸、左右侧弯和轴向旋转运动状态的稳定性。结果两种长度的颈椎椎弓根螺钉钢板系统的稳定性无明显差异,但20mm的椎弓根螺钉固定的稳定性显著高于侧块螺钉固定。结论颈椎经椎弓根固定,选择20mm长度的螺钉,即可提供足够的稳定性,同时安全性相对较高。     

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。     

寰椎椎弓根螺钉与侧块螺钉有限元分析比较

[目的]应用有限元方法比较寰椎椎弓根螺钉(pedicle screws,PS)与侧块螺钉(lateral mass screws,LMS)的力学稳定性.[方法]依据一名正常男性寰椎CT扫描资料逆向重建寰椎三维模型,再以Hypermesh 12软件设置材料属性获得骨质疏松模型,最后运用Abaqus6.9软件分别测量寰椎P...     

经后路联合使用侧块钢板螺钉和椎弓根钉内固定治疗下颈椎损伤

目的探讨经颈后正中人路联合使用侧块钢板螺钉和T．椎弓根钉内固定手术在治疗下颈椎C6～C7损伤的应用。方法应用此项技术治疗下颈椎损伤8例。其中,C6-7 6例,C7 2例。术前ASIA分级3例为C级,5例为D级。手术采用颈椎侧块钢板螺钉和T1椎弓根钉联合内固定。结果本组8例患者平均随访15个月(5～37个月),术后脊髓损伤无加重,脊髓功能均有改善,无血管、神经并发损伤。结论经颈后正中人路联合颈椎侧块钢板螺钉和椎弓根钉内固定是治疗下颈椎损伤的一种好方法。     

颈胸段脊柱侧块螺钉和椎弓根螺钉的抗拔强度的研究

目的 分析颈胸段脊柱后路不同置钉方法的拔出强度。方法 5例新鲜尸体脊柱G6～T4椎骨，分解为单个椎体30个，共60个椎弓根。对其中的颈椎分为两组，分别为侧块螺钉固定组(Roy-Camille法，Magerl法，Anderson法，自行设计侧块螺钉植入法)和椎弓根螺钉固定组。将60个椎弓根分组进行拔出测试(5mm／min的速度垂直方向拔出)。胸椎全部用椎弓根螺钉固定。结果 Roy-Camille法和Magerl法最大的拔出力接近，自行设计侧块螺钉植入法较Magerl法明显增加，而椎弓根螺钉抗拔出力最大。结论选用侧块后正中线中下1／3作为进针点，其抗拔出强度明显增加，钉道增加，操作简便；而颈胸椎椎弓根螺钉的拔出强度均大于侧块螺钉。     

颈胸段脊柱侧块螺钉和椎弓根螺钉的抗拔强度的研究

目的　分析颈胸段脊柱后路不同置钉方法的拔出强度。方法　 5例新鲜尸体脊柱C6～T4椎骨 ,分解为单个椎体 30个 ,共 6 0个椎弓根。对其中的颈椎分为两组 ,分别为侧块螺钉固定组 (Roy -Camille法 ,Magerl法 ,Anderson法 ,自行设计侧块螺钉植入法 )和椎弓根螺钉固定组。将 6 0个椎弓根分组进行拔出测试 (5mm/min的速度垂直方向拔出 )。胸椎全部用椎弓根螺钉固定。结果　Roy-Camille法和Magerl法最大的拔出力接近 ,自行设计侧块螺钉植入法较Magerl法明显增加 ,而椎弓根螺钉抗拔出力最大。结论　选用侧块后正中线中下 1 / 3作为进针点 ,其抗拔出强度明显增加 ,钉道增加 ,操作简便 ;而颈胸椎椎弓根螺钉的拔出强度均大于侧块螺钉     

寰椎椎弓根螺钉技术和侧块螺钉技术的临床疗效比较

目的：探讨寰椎椎弓根螺钉和侧块螺钉固定技术的临床疗效。方法：2006年1月-2010年1月,行寰椎椎弓根螺钉固定技术32例（A组）,行寰椎侧块螺钉固定技术28例（B组）。通过术中失血量,手术时间,颈枕区疼痛缓解,JOA评分和术后植骨融合情况评定疗效。结果：两组患者在JOA评分,颈枕区疼痛缓解WAS评分）和植骨融合率方面无明显差异。A组术中失血量和手术时间明显低于B组,有统计学意义。B组中有3例术后出现颈枕区疼痛加重。结论：寰椎椎弓根螺钉固定技术显露范围小,简化了操作程序,减少了术中、术后的并发症。在设计手术方案时,应优先考虑椎弓根螺钉技术,而侧块螺钉技术可以作为一种补充。     

寰椎椎弓根螺钉技术和侧块螺钉技术的临床疗效比较

目的：探讨寰椎椎弓根螺钉和侧块螺钉固定技术的临床疗效。方法：2006年1月至2010年1月,行寰椎椎弓根螺钉固定技术32例（A组）,行寰椎侧块螺钉固定技术28例（B组）。通过术中失血量、手术时间、颈枕区疼痛缓解（VAS评分）、JOA评分和术后植骨融合情况评定疗效。结果：两组患者在JOA评分,颈枕区疼痛缓解,和植骨融合率方面无明显差异。A组术中失血量和手术时间明显低于B组,有统计学意义（P〈0．05）。A组中2例出现寰椎后弓骨折。B组中有3例术后出现颈枕区疼痛加重,且伴有麻木。结论：寰椎椎弓根螺钉固定技术显露范围小,简化了操作程序,减少了术中、术后的并发症。在设计手术方案时,应优先考虑椎弓根螺钉技术,而侧块螺钉技术可以作为一种补充。     

Load sharing properties of cervical pedicle screw-rod constructs versus lateral mass screw-rod constructs

Lateral mass screws have a history of successful clinical use, but cannot always be used in the subaxial cervical spine. Despite safety concerns, cervical pedicle screws have been proposed as an alternative. Pedicle screws have been shown to be biomechanically stronger than lateral mass screws. No study, however, has investigated the load sharing properties comparing constructs using these screws. To investigate this, 12 fresh-frozen single cervical spine motion segments (C4–5 and C6–7) from six cadavers were isolated. They were randomized to receive either lateral mass or pedicle screw-rod constructs. After preloading, the segments were cyclically loaded with a uniplanar axial load from 0 to 90 N both with and without the construct in place. Pressure data at the disc space were continuously collected using a dynamic pressure sensor. The reduction in disc space pressure between the two constructs was calculated to see if pedicle screw and lateral mass screw-rod constructs differed in their load sharing properties. In both the pedicle screw and lateral mass screw-rod constructs, there was a significant reduction in the disc space pressures from the no-construct to construct conditions. The percentage decrease for the pedicle screw constructs was significantly greater than the percentage decrease for the lateral mass screw constructs for average pressure (p ≤ 0.002), peak pressure (p ≤ 0.03) and force (p ≤ 0.04). We conclude that cervical pedicle screw-rod constructs demonstrated a greater reduction in axial load transfer through the intervertebral disc than lateral mass screw-rod constructs. Though there are dangers associated with the insertion of cervical pedicle screws, their use might be advantageous in some clinical conditions when increased load sharing is necessary.     

Cervical pedicle screws vs. lateral mass screws: uniplanar fatigue analysis and residual pullout strengths

BACKGROUND CONTEXT: Although successful clinical use of cervical pedicle screws has been reported, anatomical studies have shown the possibility for serious iatrogenic injury. However, there are only a limited number of reports on the biomechanical properties of these screws which evaluate the potential benefits of their application. PURPOSE: To investigate if the pull-out strengths after cyclic uniplanar loading of cervical pedicle screws are superior to lateral mass screws. STUDY DESIGN: An in vitro biomechanical study. METHODS: Twenty fresh-frozen disarticulated human vertebrae (C3-C7) were randomized to receive both a 3.5 mm cervical pedicle screw and lateral mass screw. The screws were cyclically loaded 200 times in the sagittal plane. The amount of displacement was recorded every 50 cycles. After cyclical loading, the screws were pulled and tensile load to failure was recorded. Bone density was measured in each specimen and maximum screw insertion torque was recorded for each screw. RESULTS: During loading the two screw types showed similar stability initially, however the lateral mass screws rapidly loosened compared to the pedicle screws. The rate of loosening in the lateral mass screws was widely variable, while the performance of the pedicle screws was very consistent. The pullout strengths were significantly higher for the cervical pedicle screws (1214 N vs. 332 N) and 40% failed by fracture of the pedicle rather than screw pullout. Pedicle screw pullout strengths correlated with both screw insertion torque and specimen bone density. CONCLUSIONS: Cervical pedicle screws demonstrated a significantly lower rate of loosening at the bone-screw interface, as well as higher strength after fatigue testing. These biomechanical strengths may justify their use in certain limited clinical applications.     

颈椎椎间孔螺钉、侧块螺钉及椎弓根螺钉的生物力学强度比较

目的比较椎间孔螺钉(paravertebral foramen screws,PVFS)、侧块螺钉(lateral mass screws,LMS)与椎弓根螺钉(pedicle screws,PS)的生物力学强度。方法选取8具新鲜冰冻尸体,男4具、女4具,死亡时年龄(45.3±11.2)岁。CT检查排除骨折、畸形、感染、肿瘤等疾病引起的骨质破坏或其他异常,最终筛选出30个C3~C6颈椎脊椎。将制备完成的颈椎节段标本顺序编号,应用随机数字表法将其随机分为三组,每组10个标本,分别用于双侧置入椎间孔螺钉(4.5 mm×12 mm螺钉)、侧块螺钉(3.5 mm×14 mm)与椎弓根螺钉(3.5 mm×24 mm螺钉)。随机选取一侧进行直接拔出力测试(速度5 mm/min),另一侧进行疲劳测试(位移±1.0 mm,频率1 Hz,循环500次)及残余拔出力测试。结果椎间孔螺钉的直接拔出力为(327.10±17.07)N,侧块螺钉为(305.71±11.63)N,椎弓根螺钉为(635.67±22.82)N。椎间孔螺钉的残余拔出力为(265.62±18.19)N,侧块螺钉为(192.80±17.10)N,椎弓根螺钉为(494.89±41.79)N。椎间孔螺钉、侧块螺钉和椎弓根螺钉的残余拔出力较直接拔出力均有不同程度降低(tPVFS=7.795,tLMS=17.267,tPS=9.349,P<0.001),分别下降了18.8%、36.93%和22.15%。椎弓根螺钉的直接拔出力高于椎间孔螺钉和侧块螺钉(t=34.245,t=40.741,P<0.001),椎间孔螺钉略高于侧块螺钉(t=3.275,P=0.004)。残余拔出力椎弓根螺钉最高,椎间孔螺钉次之,侧块螺钉最小(F=314.619,P<0.001)。椎间孔螺钉的首次循环载荷和首次达到设定位置时载荷均高于侧块螺钉(t=3.625,P=0.002;t=5.388,P<0.001)和椎弓根螺钉(t=2.575,P=0.019;t=2.680,P=0.015),侧块螺钉与椎弓根螺钉的差异无统计学意义(t=0.609,P=0.550;t=1.953,P=0.067)。椎间孔螺钉与椎弓根螺钉的末次循环载荷均高于侧块螺钉(t=5.341,P<0.001;t=3.439,P=0.003),但椎间孔螺钉与椎弓根螺钉的差异无统计学意义(t=1.606,P=0.126)。结论椎间孔螺钉的直接拔出力略高于侧块螺钉,残余拔出力明显高于侧块螺钉,抗疲劳性能与椎弓根螺钉相近并明显优于侧块螺钉,因此,颈椎椎间孔螺钉具有作为侧块螺钉和椎弓根螺钉有效替代的潜能。     

颈椎经关节椎弓根螺钉固定与标准椎弓根螺钉固定的生物力学比较

目的 比较颈椎经关节椎弓根螺钉固定和标准椎弓根螺钉固定的拔出强度.方法 取10具新鲜尸体颈椎标本(C_3～T_1),游离成三个颈椎运动节段(C_(3,4),C_(5,6),C_7T_1).在椎体两侧随机进行经关节椎弓根螺钉固定或标准椎弓根螺钉固定,置入直径3.5 mm皮质骨螺钉.经关节椎弓根螺钉固定以上位椎骨侧块外下象限中点为进钉点,在直视椎弓根下,螺钉在冠状面内倾约45°、矢状面尾倾约50°.由上位椎骨下关节突经关节突关节、下位椎骨的椎弓根,进入下位椎骨的椎体内.标准椎弓根螺钉固定以侧块外上象限中点为进钉点,在直视椎弓根下,螺钉方向参考CT测量结果 ,尽量与椎弓根倾斜角度保持一致,在横断面上内倾约45°、矢状面上螺钉指向椎体的上1/3.在生物力学试验机上行拔出强度试验,比较两种螺钉固定的最大轴向拔出力.结果 颈椎经关节椎弓根螺钉固定平均最大轴向拨出力为(694±42)N,标准椎弓根螺钉固定为(670±36)N,两者比较差异有统计学意义(P<0.05).结论 颈椎后路经关节椎弓根螺钉固定的拔出强度大干标准椎弓根螺钉固定,从生物力学强度方面考虑经关节椎弓根螺钉固定可以作为标准椎弓根螺钉固定的一种补充方法.     

Comparison of revision strategies for failed C2-posterior cervical pedicle screws: a biomechanical study

Study purpose

With increasing usage within challenging biomechanical constructs, failures of C2 posterior cervical pedicle screws (C2-pCPSs) will occur. The purpose of the study was therefore to investigate the biomechanical characteristics of two revision techniques after the failure of C2-pCPSs.

Materials and methods

Twelve human C2 vertebrae were tested in vitro in a biomechanical study to compare two strategies for revision screws after failure of C2-pCPSs. C2 pedicles were instrumented using unicortical 3.5-mm CPS bilaterally (Synapse/Synthes, Switzerland). Insertion accuracy was verified by fluoroscopy. C2 vertebrae were potted and fixed in an electromechanical testing machine with the screw axis coaxial to the pullout direction. Pullout testing was conducted with load and displacement data taken continuously. The peak load to failure was measured in newtons (N) and is reported as the pullout resistance (POR). After pullout, two revision strategies were tested in each vertebra. In Group-1, revision was performed with 4.0-mm C2-pCPSs. In Group-2, revision was performed with C2-pedicle bone-plastic combined with the use of a 4-mm C2-pCPSs. For the statistical analysis, the POR between screws was compared using absolute values (N) and the POR of the revision techniques normalized to that of the primary procedures (%).

Results

The POR of primary 3.5-mm CPSs was 1,140.5 ± 539.6 N for Group-1 and 1,007.7 ± 362.5 N for Group-2; the difference was not significant. In the revision setting, the POR in Group-1 was 705.8 ± 449.1 N, representing a reduction of 38.1 ± 32.9 % compared with that of primary screw fixation. For Group-2, the POR was 875.3 ± 367.9 N, representing a reduction of 13.1 ± 23.4 %. A statistical analysis showed a significantly higher POR for Group-2 compared with Group-1 (p = 0.02). Although the statistics showed a significantly reduced POR for both revision strategies compared with primary fixation (p < 0.001/p = 0.001), the loss of POR (in %) in Group-1 was significantly higher compared with the loss in Group-2 (p = 0.04).

Conclusions

Using a larger-diameter screw combined with the application of a pedicle bone-plastic, the POR can be significantly increased compared with the use of only an increased screw diameter.     

Perforations and angulations of 324 cervical medial cortical pedicle screws: a possible guide to avoid lateral perforations with use of pedicle screws in lower cervical spine

Background Context

More than half of the perforations reported with usage of cervical pedicle screws (CPS) are lateral perforations, endangering the vertebral artery. The medial cortical pedicle screw (MCPS) technique with partial drilling of the medial cortex shifts the trajectory of pedicle screws medially, decreasing the lateral perforations.

Freehand determination of the trajectory angle for cervical lateral mass screws: how accurate is it?

Different methods of lateral mass screw placement in the cervical spine have been described with separate trajectories for each technique in the sagittal and parasagittal planes. In the latter, plane 30° has been recommended in the modified Magerl’s technique as the optimum angle to avoid injury to the vertebral artery and nerve root. The estimation of this angle remains arbitrary and very much operator dependant. The aim of this study was to assess how accurately the lateral trajectory angle of 30° is achieved by visual estimation amongst experienced surgeons in a tertiary spinal unit and to determine the likelihood of neurovascular injury during the procedure. We chose an anatomical ‘sawbone’ model of the cervical spine with simulated lordosis. The senior author marked the entry points. Five spinal consultants and five senior spinal fellows were asked to insert 1.6-mm K wires into the lateral masses of C3 to C6 bilaterally at 30° to the midsagittal plane using the marked entry points. The lateral angulation in the transverse plane was measured using a custom protractor and documented for each surgeon at each level and side. The mean and standard deviation (SD) of the data were obtained to determine the inter observer variability. Utilising this data, measurements were then made on a normal axial computerised tomography (CT) scan of the cervical spine of an anonymous patient to determine if there would have been any neurovascular compromise. Among the 10 surgeons, a total of 80 insertion angles were measured from C3 to C6 on either side. The overall mean angle of insertion was 25.15 (range 20.4–34.8). The overall SD was 4.78. Amongst the 80 measurements between the ten surgeons, two episodes of theoretical vertebral artery violation were observed when the angles were simulated on the CT scan. A moderate but notable variability in trajectory placement exists between surgeons during insertion of cervical lateral mass screws. Freehand estimation of 30° is not consistently achieved between surgeons and levels. In patients with gross degenerative or deformed cervical spine anatomy, this may increase the risk of neurovascular injury. The use of the ipsilateral lamina as an anatomical reference plane is supported.     

颈椎经关节椎弓根螺钉固定与标准椎弓根螺钉固定的生物力学比较

Objective To compare biomechanical pullout strength of cervical transfacet pedicle screws to that of standard pedicle screws. Methods Ten fresh human cadaveric cervical spines were harvested. On one side, transfacet pedicle screws were placed at the C3,4, C5,6, and C7T1 levels. On the other side, pedicle screws were, placed at the C3, C5, and C7 levels. The screw insertion technique at each level was randomized for right or left. The starting point for the transfacet pedicle screw insertion was about located at the midpoint of the inferolateral quadrant of the lateral mass and the direction of the screw was about 50° caudally in the sagittal plane and about 45° medially in the axial plane. Screws were placed across the facet joint and the pedicle into the body of the caudal vertebra. The entry points for pedicle screw was located at the midpoint of the superolateral quadrant of the lateral mass and the direction of the screw was about 45° toward the midline in the transverse plane and toward the upper third of the vertebral body in the sagittal plane. The pedicle screws were oriented along the axis of the pedicle in an effort to avoid violations of the cortical wall. All the screw insertions were based on direct observation and the CT scan on the pedicles. After screw placement, axial pullout testing was performed. Results The mean pullout strength for the transfacet pedicle screws was (694±42) N. This compares with (670±36) N for the pedicle screws (P< 0.05). The greatest difference at a single level in pullout strength was observed at the C5,6 level, with a mean difference of 38 N. Conclusion Transfacet pedicle screws exhibited statistically greater pullout strength to pedicle screws. At each level the transfacet pedicle screws exhibited greater pullout strength than the pedicle screws. Posterior transarticular pedicle screw fixation in the cervical spine affords an alternative to standard screw placement for plate fixation and cervical stabilization.     

下颈椎经关节螺钉与侧块钉棒固定的生物力学比较

目的 :比较下颈椎经关节螺钉与侧块钉棒系统固定的生物力学特点。方法 :采用8具新鲜尸体下颈椎标本(C5~T1),用牙托石膏粉包埋后,通过脊柱试验机对标本施加最大2.0Nm纯力偶矩,在不同测试状态下,包括完整(A组)、C5/6后方韧带复合体切除(B组)、C5~C7经关节螺钉固定(C组)、C5~C7侧块钉棒系统固定(D组),测量屈伸、侧弯及旋转方向上的三维运动范围(ROM)。在C6椎体前缘粘贴应变片,测量不同状态下椎体前柱载荷变化。结果:A组C5/6节段屈伸、侧弯和旋转方向上的ROM分别为13.6°±1.2°、6.1°±0.5°、4.2°±1.6°;B组为14.4°±1.2°,6.4°±0.6°,4.8°±0.8°,C组为2.8°±0.7°、0.7°±0.3°、0.4°±0.1°,D组为1.2°±0.3°、0.5°±0.2°、0.8°±0.3°,在屈伸方向上B组的ROM较A组明显增大(P0.05),C组和D组在各方向上均较A组和B组明显减小(P0.05);在屈伸方向上,C组与D组比较有统计学差异(P0.05),在侧弯和旋转方向上,C组和D组无统计学差异(P0.05)。A组C6/7节段屈伸、侧弯和旋转方向上的ROM分别为12.3°±1.4°、5.5°±1.2°、2.7°±0.9°;B组为12.0°±1.3°、5.6°±1.0°、2.8°±0.9°,C组为2.9°±0.9°、0.4°±0.2°、0.4°±0.1°,D组为1.2°±0.3°、0.4°±0.1°、0.7°±0.3°,A、B两组在各方向上的ROM无显著性差异(P0.05);在屈伸方向上,C组和D组的ROM有统计学差异(P0.05),在侧弯和旋转方向上,两组无统计学差异(P0.05)。C组C6椎体前柱的应变在侧弯方向上较A组明显减小(P0.05),D组在前屈、后伸、侧弯方向上较A组明显减小(P0.05),C、D组在前屈方向上比较有统计学差异(P0.05)。结论:下颈椎后方韧带复合体损伤可造成屈伸和侧弯方向上失稳,经关节螺钉固定在轴向旋转和侧弯方向上与侧块钉棒系统固定效果相似,但限制屈伸运动的能力较弱。