胸椎椎弓根根外固定螺钉拔出力的实验研究

目的:比较两种胸椎椎弓根根外固定方法与经椎弓根固定方法的螺钉拔出强度,评价胸椎椎弓根根外固定的生物力学效果。方法:新鲜胸椎标本4具,共32个肋骨-椎骨序列,根据螺钉固定方法不同分为3组,A组采用经椎弓根固定,B组采用经横突-椎体固定,C组采用经改良肋横突法固定。根据所用螺钉规格不同将其分为4种不同测试条件:D1,螺钉直径5.5mm,长度40mm;D2,螺钉直径5.5mm,长度45mm;D3,螺钉直径6.5mm,长度45mm;D4,螺钉直径6.5mm,长度50mm。测试3种固定方法下的螺钉拔出力,并做统计学分析对比。结果:D1条件下A组拔出力为787.0±119.3N,B组为706.2±109.4N,C组为616.1±82.3N,3组间比较有显著性差异(P<0.01);D2条件下A组拔出力为862.3±128.7N,B组为811.4±113.6N,C组为655.1±92.2N,A、B组间比较无显著性差异(P>0.05),A、B组与C组比较有显著性差异(P<0.01);D3条件下,A组拔出力为855.3±117.1N,B组为938.0±131.5N,C组为861.3±117.8N,A、C组间比较无显著性差异(P>0.05),A、C组与B组比较有显著性差异(P<0.01);D4条件下A组拔出力为864.3±120.9N,B组为959.6±135.2N,C组为941.2±115.4N,A组与B、C组比较均有显著性差异(P<0.01),B、C组间比较无显著性差异(P>0.05)。结论:使用直径6.5mm、长度45～50mm的螺钉固定时,胸椎椎弓根根外固定螺钉拔出力优于椎弓根固定,有较好的生物力学效果。     

胸椎椎弓根-肋骨单元与椎弓根的CT测量

目的:比较经胸椎椎弓根-肋骨单元(pedicle rib unit;PRU)置钉与传统经椎弓根置钉技术的相关径线;为临床应用提供依据.方法:对30例患者脊柱T1～T10节段进行薄层CT扫描;层厚为1mm;选择有完整PRU结构的CT横断面图像进行以下指标测量:(1)PRU宽度(PRU-W);椎弓根宽度(PW);(2)PRU钉道长度(PRU-L);椎弓根钉道长度(PL);(3)PRU中轴与矢状面夹角(PRU-A);椎弓根中轴与矢状面夹角(PA);(4)经PRU置钉的安全角度范围(△A).结果:PRU-W和PW均以T5最小;以T1为最大;由T1至T5逐渐减小;由T5至T10逐渐增大.PRU-L和PL以T1为最小;以T10为最大;由T1至T10逐渐增大.PRU-A和PA以T1为最大;以T10最小;由T1至T10逐渐缩小.PRU-L与PL、PRU-W与PW间均有显著性差异(P＜0.01).PRU-W、PRU-L在男女之间差异亦有统计学意义(P＜0.01).PRU置钉的安全角度范围△A为20°～30°.结论:胸椎PRU的横径、钉道长度均较同节段的椎弓根大;经PRU可置入更粗更长的螺钉;有更大的内倾角;安全置钉角度范围也较大.     

胸椎椎弓根置钉技术研究进展

胸椎椎弓根螺钉固定系统具有良好的三柱固定效果,近年在脊柱矫形及重建方面得到广泛运用。胸椎椎弓根解剖结构特殊,且毗邻重要血管神经,其置钉安全性一直备受关注。最早由Roy-Camille提出的徒手法置钉技术及后来出现的经椎弓根-肋骨间置钉技术、漏斗置钉技术,都存在不同程度的椎弓根壁穿透率。随着近年计算机辅助导航技术的发展,提高置钉准确性显得尤为重要。该文就胸椎椎弓根解剖特点及置钉技术方法,作一综述。     

单螺纹和双螺纹椎弓根螺钉抗拔出力比较的临床研究

背景:椎弓根螺钉技术是目前脊柱固定融合最常用的方法。为减少螺钉松动和拔出等并发症,研究人员在螺钉设计等方面进行了不断探索。目的目的:比较单螺纹和双螺纹椎弓根螺钉应用于腰椎内固定术时的螺钉抗拔出力。方法方法:78例行腰椎椎弓根螺钉固定术的患者随机分为两组,所有患者术前均测量髋部骨密度和腰椎骨密度。一组在术中植入单螺纹椎弓根螺钉,另一组则植入双螺纹椎弓根螺钉,测量拧入每枚螺钉时的最大扭矩(以下简称"螺钉扭矩"),比较两组患者的骨密度和螺钉扭矩。结果结果:单螺纹螺钉组患者40例,术前髋部骨密度T值-1.82±0.57,腰椎骨密度T值-2.17±0.77,术中共植入单螺纹椎弓根螺钉150枚,螺钉扭矩(1.03±0.39)Nm。双螺纹螺钉组患者38例,术前髋部骨密度T值-1.90±0.62,腰椎骨密度T值-2.34±0.81,共植入双螺纹椎弓根螺钉150枚,螺钉扭矩(1.45±0.39)Nm。两组患者术前骨密度无明显差异(P>0.05),双螺纹螺钉组的螺钉扭矩显著高于单螺纹螺钉组(P<0.001)。结论结论:相较于单螺纹椎弓根螺钉,双螺纹椎弓根螺钉应用于腰椎内固定术可增加螺钉的抗拔出力。     

胸椎椎弓根-肋骨复合体的解剖及影像学研究

目的 探讨胸椎椎弓根-肋骨复合体的解剖结构影像学特点及其临床意义.方法 取4具成人新鲜尸体胸椎脊柱标本.主要测量参数(数据)包括:椎弓根及椎弓根-肋骨复合体的横径、螺钉最长值、矢状角,以及椎弓根、椎弓根-肋骨复合体以及椎弓根-肋骨重叠的纵径.测量中将尸体标本与CT影像测量(含二维、三维重建)相结合.结果 椎弓根-肋骨复合体是一立体结构,椎弓根与肋骨不在同一平面,且两者位置关系随不同节段而发生变化.椎弓根-肋骨复合体纵径值T1最小,为(12.6±0.8)mm,T11最大,为(16.9±1.1)mm.椎弓根-肋骨重叠纵径值T1最小,为(7.2±0.3)mm,T10最大,为(11.8±1.0)mm.椎弓根纵径与椎弓根-肋骨复合体纵径间差异无统计学意义(P＞0.05),椎弓根纵径、椎弓根-肋骨复合体纵径均与椎弓根-肋骨重叠纵径间差异有统计学意义(P＜0.05).结论 椎弓根-肋骨复合体是一较复杂的立体结构,椎弓根-肋骨重叠纵径应被视为该复合体的真实或有效纵径.     

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...     

经椎间孔椎间融合椎弓根螺钉内固定治疗腰椎不稳

目的探讨经椎间孔椎间融合椎弓根螺钉内固定治疗在腰椎不稳的疗效和影响因素。方法经后外侧小切口单侧椎弓根固定加经椎间孔椎间融合治疗73例腰椎不稳患者。采用JOA评分、观测影像学改变及植骨融合率评价疗效,并对影响疗效的相关因素进行分析。结果 73例均获得随访,时间16～38个月。JOA评分:术前为(10.24±3.68)分,术后3个月为(20.18±3.89)分、术后2年为(20.83±4.01)分,与术前比较差异均有统计学意义(P<0.05)。其中优29例,良22例,中17例,差5例,优良率为69.9%。椎间隙高度:术前为(5.83±1.71)mm,术后3个月为(9.45±1.36)mm、术后2年为(8.96±1.28)mm,与术前比较差异均有统计学意义(P<0.05)。患者术后3个月、2年的节段活动度、矢状滑移距离均低于术前,差异均有统计学意义(P<0.05)。植骨融合率为87%。结论单侧椎弓根固定加经椎间孔椎间融合术能够恢复脊柱的稳定性,重建腰椎生理前凸,并能改善腰椎生物力学环境及恢复椎间隙高度。年龄<60岁、病程<24个月的患者手术治疗效果较好。     

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。     

不同骨密度下椎弓根螺钉拔出力的有限元分析

目的:运用有限元法分析评价不同骨密度条件下椎弓根螺钉拔出过程中的应力分布和最大拔出力,探讨安全植入椎弓根螺钉内固定的最低骨密度。方法:基于河北医科大学第三医院2021年1月就诊的1例健康男性志愿者的腰椎CT平扫数据和标准椎弓根螺钉参数,建立腰1椎体和椎弓根螺钉的三维模型,将椎体按骨密度值(QCT法)分为A组(BMD＝1...     

经胸椎椎弓根-肋骨途径置入螺钉安全角度的CT测量

目的：探讨胸椎T1～T10经椎弓根-肋骨途径置入螺钉的安全角度及变化规律。方法：选取156例正常成人的胸椎CT薄层扫描资料，其中男96例，女60例；年龄18～54岁，平均39岁。在胸椎CT片上测量T1～T10椎弓根-肋骨的横径、经椎弓根-肋骨途径置入的螺钉与矢状面的最小与最大安全成角及安全角度范围。结果：从T1～T4椎弓根-肋骨的横径逐渐减小．T5～T10逐渐增大：置钉安全角度范围T1与T2比较及T5～T10无显著性差异（P〉0．05），而T2与，T3及T4与T5比较均有显著性差异（P〈0．05），T1、T2置钉安全角度范围最大，T5～T10次之，T3、T4最小；男性与女性比较无显著性差异（P〉0．05）。结论：T1～T10胸椎的椎弓根-肋骨横径大小不同。经此途径置钉安全角度的大小亦不完全相同。     

Pullout strength of pedicle screws versus pedicle and laminar hooks in the thoracic spine

While the biomechanical properties of pedicle screws have proven to be superior in the lumbar spine, little is known concerning pullout strength of pedicle screws in comparison to hooks in the thoracic spine. In vitro biomechanical pullout testing was performed to evaluate the axial pullout strength of pedicle screws versus pedicle and laminar hooks in the thoracic spine with regard to surgical correction techniques in scoliosis. Nine human cadaveric thoracic spines were harvested and disarticulated. To simulate a typical posterior segmental scoliosis instrumentation, standard pedicle hooks were used between T4 and T8 and supralaminar hooks between T9 and T12 and tested against pedicle screws. The pedicle screws were loaded strictly longitudinal to their axis; the hooks were loaded perpendicular to the intended rod direction. In total, 90 pullout tests were performed. Average pullout strength of the pedicle screws was significantly higher than in the hook group (T4-T8: 531 N versus 321 N, T9-T12: 807 N versus 600 N, p < 0.05). Both screw diameter and the bone mineral density (BMD) had significant influence on the pullout strength in the screw group. For scoliosis correction, pedicle screws might be beneficial, especially for rigid thoracic curves, since they are significantly more resistant to axial pullout than both pedicle and laminar hooks.     

对徒手置入胸椎椎弓根螺钉的安全性评价

目的：评价徒手置入胸椎椎弓根螺钉的安全性并探讨其置钉方法.方法：372例患者采用徒手方法置入胸椎椎弓根螺钉,记录置入操作中和术后并发症,其中37例患者术后行CT断层扫描检查判断螺钉的位置,记录所有穿透骨皮质螺钉的数目和距离.结果：共徒手置入胸椎椎弓根螺钉2261枚,平均每例患者置入螺钉6.08枚,术中6例次置钉过程中出现脑脊液从钉道中流出,术中和术后未出现神经、血管和内脏损伤等并发症.37例患者术后行CT扫描判断螺钉位置,405枚螺钉中124枚（30.62%）穿透骨皮质,1枚（0.02%）穿透椎弓根内侧壁超过4mm.结论：徒手置入胸椎椎弓根螺钉穿透骨皮质的发生率较高,应该根据每个椎体旋转、倾斜等差异个体化确定置钉位置和方向,操作仔细认真,保证准确、安全、可靠地置入胸椎椎弓根螺钉.     

Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study

Background:

The objective of this cadaveric study was to analyze the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of lower thoracic and lumbar pedicle screws. We also investigated the effect of bone mineral density (BMD), diameter of pedicle screws, and the region of spine on the pullout strength of pedicle screws.

Materials and Methods:

Sixty fresh human cadaveric vertebrae (D10–L2) were harvested. Dual-energy X-ray absorptiometry (DEXA) scan of vertebrae was done for BMD. Titanium pedicle screws of different diameters (5.2 and 6.2 mm) were inserted in the thoracic and lumbar segments after dividing the specimens into three groups: a) standard pedicle screw (no cortical perforation); b) screw with medial cortical perforation; and c) screw with lateral cortical perforation. Finally, pullout load of pedicle screws was recorded using INSTRON Universal Testing Machine.

Results:

Compared with standard placement, medially misplaced screws had 9.4% greater mean pullout strength and laterally misplaced screws had 47.3% lesser mean pullout strength. The pullout strength of the 6.2 mm pedicle screws was 33% greater than that of the 5.2 mm pedicle screws. The pullout load of pedicle screws in lumbar vertebra was 13.9% greater than that in the thoracic vertebra (P = 0.105), but it was not statistically significant. There was no significant difference between pullout loads of vertebra with different BMD (P = 0.901).

Conclusion:

The mean pullout strength was less with lateral misplaced pedicle screws while medial misplaced pedicle screw had more pullout strength. The pullout load of 6.2 mm screws was greater than that of 5.2 mm pedicle screws. No significant correlation was found between bone mineral densities and the pullout strength of vertebra. Similarly, the pullout load of screw placed in thoracic and lumbar vertebrae was not significantly different.     

Hydroxyapatite coating enhances fixation of loaded pedicle screws: a mechanical in vivo study in sheep

Loosening of the pedicle screws with subsequent non-union or loss of correction is a frequent problem in spinal instrumentation. In a clinical pilot study, coating of pedicle screws with plasma-sprayed hydroxyapatite (HA) resulted in a significant increase of removal torque. An experimental study was performed to investigate the effects of HA coating on the pull-out resistance. Thirteen sheep were operated on with destabilising laminectomies at two levels, L2-L3 and L4-L5. Two instrumentations with four pedicle screws in each were used for stabilisation. Uncoated screws (stainless steel) or the same type of screws coated with plasma-sprayed HA were used in either the upper or the lower instrumentation in a randomised fashion. Four sheep were examined immediately after the application of the screws, three sheep at 6 weeks and four sheep at 12 weeks. Two sheep were euthanised early due to complications. The pull-out resistance was recorded in two HA-coated and two standard screws in each animal. The maximum pull-out resistance was higher for the HA-coated screws at 0 weeks (P< 0.02) and at 12 weeks (P<0.01) when compared to the uncoated screws, while there was no significant difference between the groups at 6 weeks. We believe that the higher pull-out resistance for HA-coated screws at 0 weeks was mainly caused by differences in surface roughness, while the difference at 12 weeks was due to a favourable bone reaction around the HA-coated screws. At 12 weeks, the average stiffness was significantly higher for the HA-coated screws, while there was no significant differences in stiffness between the two screw types at 0 and 6 weeks. Energy to failure was significantly higher for coated screws when compared to the uncoated screws at all three time points. HA coating improves fixation of loaded pedicle screws, with increased pull-out resistance and reduced risk of loosening.     

非影像监视下行脊柱侧凸胸椎椎弓根螺钉置入的临床应用

目的:探讨脊柱侧凸胸椎椎弓根螺钉非影像监视下徒手置入的方法及可行性。方法:57例脊柱侧凸患者行后路椎弓根螺钉系统矫形手术,徒手法置入胸椎椎弓根螺钉。术后常规拍摄脊柱全长X线片,随机选取10例患者行CT扫描观察,了解螺钉置入的准确性。结果:共置入胸椎椎弓根螺钉362枚。术后X线片观察到10枚螺钉偏外,4枚螺钉偏下,其中2枚螺钉引起轻微肋间神经痛,3周后完全缓解。CT观察47枚螺钉有2枚螺钉导致椎弓根内壁膨胀内移,没有相应神经症状。主弯Cobb角术前平均60.4°(32°～121°),术后平均18.3°(1°～70°),平均矫正率71.9%(38.1%～98.0%)。结论:徒手法置入脊柱侧凸胸椎椎弓根螺钉是可行的。     

Pull-out strength of pedicle hooks with fixation screws: influence of screw length and angulation

The pull-out force of thoracic spinal pedicle hooks secured by long fixation screws engaging the posterior portion of the vertebral endplate was measured. The perfomance of these hooks was compared with that of hooks using a shorter screw and different screw orientation such that the vertebral endplates were not perforated. The longer and differently angulated screws, engaging the endplate, significantly enhanced the fixation potential of the hooks.     

CT-navigation versus fluoroscopy-guided placement of pedicle screws at the thoracolumbar spine: single center experience of 4,500 screws

Purpose

Single center evaluation of the placement accuracy of thoracolumbar pedicle screws implanted either with fluoroscopy or under CT-navigation using 3D-reconstruction and intraoperative computed tomography control of the screw position. There is in fact a huge variation in the reported placement accuracy of pedicle screws, especially concerning the screw placement under conventional fluoroscopy most notably due to the lack of the definition of screw misplacement, combined with a potpourri of postinstrumentation evaluation methods.

Methods

The operation data of 1,006 patients operated on in our clinic between 1995 and 2005 is analyzed retrospectively. There were 2,422 screws placed with the help of CT-navigation compared to 2,002 screws placed under fluoroscopy. The postoperative computed tomography images were reviewed by a radiologist and an independent spine surgeon.

Results

In the lumbar spine, the placement accuracy was 96.4 % for CT-navigated screws and 93.9 % for pedicle screws placed under fluoroscopy, respectively. This difference in accuracy was statistically significant (Fishers Exact Test, p = 0.001). The difference in accuracy became more impressing in the thoracic spine, with a placement accuracy of 95.5 % in the CT-navigation group, compared to 79.0 % accuracy in the fluoroscopy group (p < 0.001).

Conclusion

This study underlines the relevance of CT-navigation-guided pedicle screw placement, especially when instrumentation of the middle and upper thoracic spine is carried out.