Pullout Strength after Expandable Polymethylmethacrylate Transpedicular Screw Augmentation for Pedicle Screw Loosening

Objective

Pedicle screw fixation for spine arthrodesis is a useful procedure for the treatment of spinal disorders. However, instrument failure often occurs, and pedicle screw loosening is the initial step of a range of complications. The authors recently used a modified transpedicular polymethylmethacrylate (PMMA) screw augmentation technique to overcome pedicle screw loosening. Here, they report on the laboratory testing of pedicle screws inserted using this modified technique.

Methods

To evaluate pullout strengths three cadaveric spinal columns were used. Three pedicle screw insertion methods were utilized to compare pullout strength; the three methods used were; control (C), traditional transpedicular PMMA augmentation technique (T), and the modified transpedicular augmentation technique (M). After control screws had been pulled out, loosening with instrument was made. Screw augmentations were executed and screw pullout strength was rechecked.

Results

Pedicle screws augmented using the modified technique for pedicle screw loosening had higher pullout strengths than the control (1106.2±458.0 N vs. 741.2±269.5 N; p=0.001). Traditional transpedicular augmentation achieved a mean pullout strength similar to that of the control group (657.5±172.3 N vs. 724.5±234.4 N; p=0.537). The modified technique had higher strength than the traditional PMMA augmentation technique (1070.8±358.6 N vs. 652.2±185.5 N; p=0.023).

Conclusion

The modified PMMA transpedicular screw augmentation technique is a straightforward, effective surgical procedure for treating pedicle screw loosening, and exhibits greater pullout strength than traditional PMMA transpedicular augmentation. However, long-term clinical evaluation is required.     

In vitro simulation of intraoperative vertebroplasty applied for pedicle screw augmentation. A biomechanical evaluation

Background and purpose

The purpose of this study was to evaluate the effect of an in vitro simulation of intraoperative vertebroplasty on embedded pedicle screws resistance to pullout. This method involved an application of acrylic cement into the vertebral bodies only after pedicle screws implementation.

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.     

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。     

骨水泥强化椎体提高椎弓根螺钉置入后的稳定性

摘要 背景：胸腰椎退变性疾病合并骨质疏松症时,临床治疗棘手。采用椎体骨水泥灌注可增强椎弓根螺钉及脊柱稳定性。 目的：观察椎体骨水泥灌注提高椎弓根螺钉置入后稳定性在治疗骨质疏松症合并腰椎疾病的临床疗效,并分析骨水泥灌注技术参数及固定节段选择对结果的影响。 方法：39例骨质疏松症合并腰椎疾病患者采用骨水泥灌注强化椎体加椎弓根螺钉固定、椎板减压神经根松解及后外侧植骨融合治疗。术前及术后6,12,24,36个月随访进行JOA评分,计算手术改善率;行X射线片及MRI检查,并观察有无并发症发生。 结果与结论：置入螺钉过程中未发生因骨水泥渗漏、放热效应及毒性反应引起并发症;手术时间90~180 min,置入失血量600~1 000 mL,单椎体操作时间8~12 min;单椎体骨水泥用量3.5~5.0 mL。置入前JOA评分平均11分,置入后1年随访平均为23分,改善率66.7%;末次随访平均25分,改善率77.8%。1例置入后2年发生固定节段上方椎体压缩性骨折。随访期间未出现螺钉松动、断裂和脱出;无断棒现象发生。结果提示,椎体骨水泥灌注提高椎弓根螺钉置入后的稳定性,是治疗骨质疏松症合并腰椎疾病是一种可靠的方法。 关键词：骨质疏松症;腰椎;骨水泥;椎体成形;椎弓根螺钉 doi:10.3969/j.issn.1673-8225.2010.42.039     

单、双侧后外侧椎弓根钉置入并植骨融合治疗退变性腰椎滑脱的随机对照

背景：节段融合辅以椎弓根钉置入内固定治疗退变性腰椎疾病可提高融合率。 目的：比较单、双侧椎弓根钉置入内固定并植骨融合治疗退变性腰椎滑脱的临床疗效和融合率。 方法：将退变性腰椎滑脱患者随机分为2组,分别行双侧与单侧椎弓根钉置入内固定并植骨后外侧融合。 结果与结论：两组患者失血量、输血量、住院时间、手术并发症、临床疗效、融合率和对临近间盘的影响方面差异无显著性意义。单侧内固定组手术操作时间较双侧内固定组明显缩短(P < 0.001)。双侧内固定组置入186枚椎弓根螺钉中有3枚穿透皮质刺激神经根而行二次手术;单侧内固定组置入90枚螺钉未发生与螺钉置入相关的并发症。表明退变性腰椎滑脱患者行单侧和双侧椎弓根钉置入并植骨内固定后外侧融合效果相同,但单侧内固定成本费用低、节省手术时间,置钉时穿破椎弓根皮质刺激神经根的风险小。     

与脊柱导航联合应用于椎弓根钉置入过程中的肌电图监测：敏感和有效吗？☆

背景：脊柱外科手术中已广泛应用术中肌电图监测,但肌电图监测标准仍有待深入研究,而术中肌电图监测在国内的应用报道十分有限。 目的：分析电诱发肌电图监测在椎弓根螺钉置入内固定过程中的敏感程度以及可靠性。 设计、时间、地点：回顾性病例分析,于2008-07/2009-05在北京中医药大学东直门医院骨科完成。 对象：选择北京中医药大学东直门医院骨科收治的腰椎间盘突出症及腰椎管狭窄症患者74例,男31例,女43例;年龄22~83岁,平均58岁。 方法：于椎弓根螺钉内固定和椎管内手术操作中全程使用电诱发肌电图监测,刺激电流为2 Hz、时程0.2 ms的方波脉冲电刺激,打入椎弓根螺钉时刺激强度限制为0~60 mA,电刺激强度为逐级递增。腰椎板切除减压、髓核摘除、神经根探查松解等椎管内手术操作时刺激强度限制为2~4 mA。于双侧长收肌、股直肌、股二头肌、胫骨前肌和腓肠肌内侧头的肌腹中部及肛门括约肌记录分析肌电反应。 主要观察指标：实时监测和记录自由肌电反应及触发肌电反应中动作电位出现的时间、频率、振幅、肌群,以及术后神经根功能损伤及恢复情况。 结果：74例患者在术中肌电图监测和3-D脊柱导航系统帮助下共置入378只椎弓根螺钉内固定,仅有3只椎弓根螺钉(L4 2只,L5 1只)置入过程中,当电流强度小于10 mA时即出现肌电反应,及时提醒术者,经术中C臂X射线透视证实椎弓根骨皮质穿透,而予以重新置入,置入准确率达99.2%。电诱发肌电图监测下进行椎管内手术操作,仅2例患者术中进行L5,S1节段减压、松解时反复出现下肢明显肌电反应, 术后出现下肢神经症状较术前加重,经2~4周保守治疗后恢复,神经根误损伤率为2.7%。所有患者术后未出现不可逆的相关神经根损伤症状。 结论：椎弓根螺钉置入腰椎椎管内手术过程中电诱发肌电监测可最大限度地保证安全操作、预防神经根损伤。与术中脊柱导航系统的联合应用可增加监测的敏感性,在复杂腰骶椎术中是目前最为有效的监测方法。     

胸椎椎弓根-肋骨复合体螺钉置入内固定的应用解剖学特征

背景：上、中胸椎周围结构复杂,椎弓根的横径相对窄小,如再合并发育畸形,导致螺钉不能置入,或者置入后造成副损伤,置钉安全性和有效性得不到保证。 目的：提出“椎弓根-肋骨复合体”的概念,观察其形态结构,分析其在解剖学上置入螺钉的可行性。 方法：观察6具成人尸体胸椎标本(T1~12)椎弓根及椎弓根-肋骨复合体的形态结构,测量下列参数：横径、纵径、椎弓根-肋骨复合体轴线螺钉置入最长值、椎弓根-肋骨复合体轴线螺钉横断面角及椎弓根-肋骨复合体轴线螺钉与椎弓板的夹角。 结果与结论：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。横径为13.0~17.3 mm,纵径为5.8~8.0 mm,椎弓根-肋骨复合体轴线螺钉置入最长值为43.4~60.5 mm,椎弓根-肋骨复合体轴线螺钉横断面角为15.4°~36.7°,椎弓根-肋骨复合体轴线螺钉与椎弓板的夹角为76.2°~85.4°。提示沿胸椎经椎弓根-肋骨复合体轴线置入螺钉内固定时,安全范围较大。应用于临床时,可作为椎弓根螺钉内固定的一种补充,特别是在无法完成椎弓根螺钉置入的胸椎平面。     

The Use of Pedicle Screw-Rod System for the Posterior Fixation in Cervico-Thoracic Junction

Objective

In cervico-thoracic junction (CTJ), the use of strong fixation device such as pedicle screw-rod system is often required. Purpose of this study is to analyze the anatomical features of C7 and T1 pedicles related to screw insertion and to evaluate the safety of pedicle screw insertion at these levels.

Methods

Nineteen patients underwent posterior CTJ fixation with C7 and/or T1 included in fixation levels. Seventeen patients had tumorous conditions and two with post-laminectomy kyphosis. The anatomical features were analyzed for C7 and T1 pedicles in 19 patients using computerized tomography (CT). Pedicle screw and rod fixation system was used in 16 patients. Pedicle violation by screws was evaluated with postoperative CT scan.

Results

The mean values of the width, height, stable depth, safety angle, transverse angle, and sagittal angle of C7 pedicles were 6.9 ± 1.34 mm, 8.23 ± 1.18 mm, 30.93 ± 4.65 mm, 26.42 ± 7.91 degrees, 25.9 ± 4.83 degrees, and 10.6 ± 3.39 degrees. At T1 pedicles, anatomic parameters were similar to those of C7. The pedicle violation revealed that 64.1% showed grade I violation and 35.9% showed grade II violation, overall. As for C7 pedicle screw insertion, grade I was 61.5% and grade II 38.5%. At T1 level, grade I was 65.0% and grade II 35.0%. There was no significant difference in violation rate between the whole group, C7, and T1 group.

Conclusion

C7 pedicles can withstand pedicle screw insertion. C7 pedicle and T1 pedicle are anatomically very similar. With the use of adequate fluoroscopic oblique view, pedicle screw can be safely inserted at C7 and T1 levels.     

胸椎椎弓根外固定技术的临床应用☆

应用椎弓根外内固定技术2004/2007年在中山大学附属第三医院骨科治疗34例患者，固定前采用CT加密扫描测量进钉点、进钉点至椎体前缘的深度、进钉角度和直径，固定中椎弓根钉入点为横突尖，进钉方向为平均向头侧倾斜10°~ 20°、与中线成角30°~40°，顺椎弓根外侧皮质进入椎体，固定后CT加密扫描观察螺钉周围的皮质骨是否完整、是否靠近节段血管、是否穿透皮质骨，评价置入钉的准确性和安全性。34例患者共置入160枚胸椎椎弓根螺钉,固定后CT加密扫描和X射线片观察到148枚(92.5% )螺钉置入准确，12枚(7.5%)螺钉发生错置。实验结果表明，胸椎椎弓根根外内固定与椎弓根内固定相比，具有更宽的置入宽度，更长的螺钉长度，以及更大的内聚角度，具有安全可靠、简单实用等优点，并具有生物力学优越性，是胸椎后路内固定的一种良好选择。     

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。     

Cervical Pedicle Screw Insertion Using the Technique with Direct Exposure of the Pedicle by Laminoforaminotomy

Objective

To present the accuracy and safety of cervical pedicle screw insertion using the technique with direct exposure of the pedicle by laminoforaminotomy.

Methods

We retrospectively reviewed 12 consecutive patients. A total of 104 subaxial cervical pedicle screws in 12 patients had been inserted. We also assessed the clinical and radiological outcomes and analyzed the direction and grade of pedicle perforation (grade 0: no perforation, 1: <25%, 2: 20% to 50%, 3: >50% of screw diameter) on the postoperative vascular-enhanced computed tomography scans. Grade 2 and 3 were considered as incorrect position.

Results

The correct position was found in 95 screws (91.3%); grade 0-75 screws, grade 1-20 screws and the incorrect position in 9 screws (8.7%); grade 2-6 screws, grade 3-3 screws. There was no neurovascular complication related with cervical pedicle screw insertion.

Conclusion

This technique (technique with direct exposure of the pedicle by laminoforaminotomy) could be considered relatively safe and easy method to insert cervical pedicle screw.     

Virtual reality spine surgery simulation: an empirical study of its usefulness

Abstract

Objective:

This study explores the usefulness of virtual simulation training for learning to place pedicle screws in the lumbar spine.

Methods:

Twenty-six senior medical students anonymously participated and were randomized into two groups (A?=?no simulation; B?=?simulation). Both groups were given 15 minutes to place two pedicle screws in a sawbones model. Students in Group A underwent traditional visual/verbal instruction whereas students in Group B underwent training on pedicle screw placement in the ImmersiveTouch^® simulator. The students in both groups then placed two pedicle screws each in a lumbar sawbones models that underwent triplanar thin slice computerized tomography and subsequent analysis based on coronal entry point, axial and sagittal deviations, length error, and pedicle breach. The average number of errors per screw was calculated for each group. Semi-parametric regression analysis for clustered data was used with generalized estimating equations accommodating a negative binomial distribution to determine any statistical difference of significance.

Results:

A total of 52 pedicle screws were analyzed. The reduction in the average number of errors per screw after a single session of simulation training was 53·7% (P = 0·0067). The average number of errors per screw in the simulation group was 0·96 versus 2·08 in the non-simulation group. The simulation group outperformed the non-simulation group in all variables measured. The three most benefited measured variables were length error (86·7%), coronal error (71·4%), and pedicle breach (66·7%).

Conclusions:

Computer-based simulation appears to be a valuable teaching tool for non-experts in a highly technical procedural task such as pedicle screw placement that involves sequential learning, depth perception, and understanding triplanar anatomy.     

短节段椎弓根螺钉置入内固定椎体成形治疗胸腰椎骨折的生物力学检测☆

背景：为避免单纯椎弓根螺钉置入内固定治疗胸腰段骨折出现的内固定物松动、断裂,及合并植骨时出现的骨折不愈合、后凸畸形丢失,而发展的短节段椎弓根螺钉合并椎体成形技术治疗胸腰段骨折,临床已有应用,但其生物力学方面鲜有研究。 目的：观察应用椎弓根螺钉置入内固定椎体成形治疗胸腰椎骨折的生物力学变化。 方法：12个冻存的新鲜胸腰段脊椎(T12~L2)标本,用于制备胸腰椎骨折模型,备测试。分为3组,经皮椎体成形术组：给予经单侧椎弓根注入低黏度的含对比剂骨水泥5~7 mL;椎弓根螺钉内固定组：于T12、L2椎弓根置入螺钉;强化组：行椎弓根螺钉内固定的同时行伤椎骨水泥椎体成形术,测试各组静态最大抗压强度及刚度。 结果与结论：骨水泥分布面积皆大于50%,经皮椎体成形术组和椎弓根螺钉内固定组最大静态抗压强度与刚度均小于强化组最大强度和刚度(P < 0.05)。椎弓根螺钉内固定组椎弓根螺钉较小强度下出现弯曲,而强化组在达到极性轴向压缩强度时才出现弯曲。提示应用短节段椎弓根钉置入内固定椎体成形治疗胸腰椎骨折提高了固定的强度及刚度,并且维持了复位伤椎高度,提高了稳定性,减少了椎弓根螺钉的并发症。     

First clinical experiences with a new cervical fixation device - technical report

In a first clinical series of ten patients the new cervical fixation device StarLock trade mark (Synthes, Umkirch, Germany) was implanted.[nl]Characteristics of the device are deep threaded screws with higher pullout resistance and a high angular tolerance while inserting the rods thus simplifying the implantation.[nl]62 lateral mass screws in ten patients were inserted. In 2 cases placement of screws was insufficient (3.2 %) because of surgical difficulties not attributable to the system technique.[nl]In all other cases a radiologically proven stabilization was created. [nl]Due to the high angular tolerance of the screw clamps bending of rods is simplified, especially in cases of longer constructs, and shortens the operation time.[nl]The design of the StarLock trade mark system allows an easy application of computer-navigated placing of transpedicular screws.[nl]This new cervical fixation device is easy to handle and simplifies rod application especially in longer constructs.     

三种置钉方法在下颈椎经椎弓根螺钉置入过程中的比较

背景：目前各种下颈椎椎弓根置钉方法的准确率报道不一,特别是国内常用的椎板部分切除置钉法、Abumi法、管道疏通法缺乏比较。 目的：探讨下颈椎(C3~7)经椎弓根螺钉内固定的可行性,比较椎板部分切除置钉法、Abumi法、管道疏通法在置钉满意率、出血量、置钉时间、并发症等方面的差异。 方法：选择60例需颈后路经椎弓根螺钉内固定治疗的下颈椎疾患病例,随机分成3组,各置入椎弓根螺钉80枚,分别采用椎板部分切除置钉法、Abumi法及管道疏通法。术中计算各方法置钉时间、出血量;出院前观察置钉满意率及在颈椎椎弓根四壁损伤例数的构成比;比较C3~7每一节段的椎弓根外侧壁损伤发生率。 结果与结论：椎板部分切除组、Abumi组及管道疏通组置钉时间依次递减(P < 0.05),置钉满意率依次递增(P < 0.05)。3组间置钉出血量及颈椎椎弓根四壁损伤例数的构成比差异无显著性意义(P > 0.05),椎弓根损伤好发生于外壁。C4、C5节段外壁损伤发生率明显高于C3、C6、C7。提示管道疏通法在经颈后路椎弓根螺钉内固定常规置钉法中优势明显。     

利用图像存储传输系统数据库构建下颈椎椎弓根模型及其临床意义

背景：下颈椎椎弓根钉内固定技术具有良好的生物力学强度、三维稳定性和植骨融合率。然而,由于下颈椎解剖结构复杂且个体差异性大,常导致螺钉置入困难,复位风险高。 目的：利用图像存储传输系统结合64排CT片及X射线片于内固定前精确测量下颈椎后方解剖学结构,指导下颈椎内固定过程中椎弓根置钉。 方法：51例下颈椎疾患病例利用图像存储传输系统测量定位法行颈椎椎弓根内固定。同时对比同期开展治疗的两种不同方案的颈椎内固定患者：解剖置钉法26例,管道疏通法17例。以Andrew椎弓根螺钉CT位置分级标准评价3组患者的置钉准确率。 结果与结论：图像存储传输系统测量定位组置钉准确率显著高于其他两组(P < 0.05),图像存储传输系统测量定位组病例均未发现脊髓、椎动脉、神经等组织损伤。提示应用图像存储传输系统结合64排CT及X射线片内固定前测量,能够指导内固定过程中安全置入颈椎椎弓根螺钉,置钉效果明显强于传统的解剖置钉法及管道疏通法。     

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。     

A Case of Pedicle Screw Loosening Treated by Modified Transpedicular Screw Augmentation with Polymethylmethacrylate

We report a case of pedicle screw loosening treated by modified transpedicular screw augmentation technique using polymethylmethacrylate (PMMA), which used the anchoring effect of hardened PMMA. A 56-year-old man who had an L3/4/5 fusion operation 3 years ago complained of continuous low back pain after this operation. The computerized tomography showed a radiolucent halo around the pedicle screw at L5. We augmented the L5 pedicle screw with modified pedicle screw augmentation technique using PMMA and performed an L3/4/5 pedicle screw fixation without hook or operation field extension. This modified technique is a kind of transpedicular stiffness augmentation using PMMA for the dead space around the loosed screw. After filling the dead space with 1-2 cc of PMMA, we inserted a small screw. Once the PMMA hardened, we removed the small screw and inserted a thicker screw along the existing screw threading to improve the pedicle screws'' pullout strength. At 10 months'' follow-up, x-ray showed strong fusion of L3/4/5. The visual analogue scale (VAS) of his back pain was improved from 9 to 5. This modified transpedicular screw augmentation with PMMA using anchoring effect is a simple and effective surgical technique for pedicle screw loosening. However, clinical analyses of long-term follow-up and biomechanical studies are needed.     

骨水泥椎体强化椎弓根钉置入对骨质疏松脊柱生物力学稳定性的影响

背景：伴有骨质疏松患者的脊柱内固定松动、脱落是脊柱外科一个复杂而棘手的问题。用聚甲基丙烯酸甲酯骨水泥强化椎弓根螺钉可增加伴有骨质疏松患者的椎弓根螺钉防止椎弓根钉的松动及脱落。 目的：评价聚甲基丙烯酸甲酯骨水泥椎体强化后椎弓根钉固定对不稳定骨质疏松脊柱的生物力学稳定性影响。 设计、时间及地点：体外生物力学实验,于2008-03在上海大学生物力学实验室完成生物力学实验。 材料：12具新鲜老年女性尸体T10~L3椎体标本,制成T12、L1间的不稳定模型,采用椎弓根螺钉系统固定。 方法：将标本按照不同的处理方式分为4组。①对照组：为完整标本,只进行生物力学性能的测试。②一次固定组：对照组测试后随机选取6具不稳定模型,行T11~L2椎弓根钉固定。③二次固定组：一次固定组标本完成稳定性测试后,取出所有椎弓根螺钉,分别用注射器向T11~L2椎弓根钉道注入配制好的聚甲基丙烯酸甲酯骨水泥骨水泥2.0 mL后再次拧入螺钉固定。④强化固定组：将余下的6具标本于T11~L2双侧椎弓根分别以直径3.5 mm的钻头导孔,沿孔道插入直径3.5 mm的穿刺导管,插入深度为40 mm,用加压注射器经导管缓慢向椎体内加压注射配制好的聚甲基丙烯酸甲酯骨水泥3.5 mL后拧入螺钉固定。 主要观察指标：进行轴向压缩、前屈/后伸、左/右侧弯、左/右旋转7项非损伤性加载,比较上述4组不同状态下脊柱的相对运动范围变化。 结果：与一次固定组比较,二次固定组及强化固定组脊柱的相对运动范围增加(P < 0.05),强化固定组与二次固定组组间比较,差异无统计学意义(P > 0.05)。 结论：椎体成形强化椎弓根钉固定及钉道强化固定均可明显增强不稳定骨质疏松脊柱的稳定性。