椎体后凸成形术与椎体成形术生物力学比较

目的比较椎体后凸成形术（KP）与椎体成形术（VP）对骨质疏松性椎体压缩骨折（OVCF）椎体力学性能的影响。方法5具尸体取20个胸腰段骨质疏松单椎体标本,按配对设计,分配为球囊扩张椎体后凸成形术组（KP组）和椎体成形术组（VP组）。经轴向加载压缩25%,制成椎体压缩骨折,记录制成骨折时的最大载荷及刚度数据。KP组将椎体压缩骨折标本行球囊扩张椎体后凸成形术;VP组将椎体压缩骨折标本行椎体成形术。然后将骨水泥强化治疗的椎体再次经万能力学试验机轴向加载,记录治疗后最大载荷及刚度数据。结果KP组和VP组骨折治疗后椎体最大载荷均分别明显高于骨折前（P〈0.01）,而椎体刚度差异无统计学意义（P〉0.05）。KP组与VP组间比较治疗后椎体最大载荷差异无统计学意义（P〉0.05）,椎体刚度差异无统计学意义（P〉0.05）。结论KP和VP均可明显增加OVCF椎体的抗压强度和恢复刚度。     

Spinal loads after osteoporotic vertebral fractures treated by vertebroplasty or kyphoplasty

Vertebroplasty and kyphoplasty are routine treatments for compression fractures of vertebral bodies. A wedge-shaped compression fracture shifts the centre of gravity of the upper body anteriorly and generally, this shift can be compensated in the spine and in the hips. However, it is still unclear how a wedge-shaped compression fracture of a vertebra increases forces in the trunk muscle and the intradiscal pressure in the adjacent discs. A nonlinear finite element model of the lumbar spine was used to estimate the force in the trunk muscle, the intradiscal pressure and the stresses in the endplates in the intact spine, and after vertebroplasty and kyphoplasty treatment. In this study, kyphoplasty represents a treatment with nearly full fracture reduction and vertebroplasty one without restoration of kyphotic angle although in reality kyphoplasty does not guarantee fracture reduction. If no compensation of upper body shift is assumed, the force in the erector spine increases by about 200% for the vertebroplasty but by only 55% for the kyphoplasty compared to the intact spine. Intradiscal pressure increases by about 60 and 20% for the vertebroplasty and kyphoplasty, respectively. In contrast, with shift compensation of the upper body, the increase in muscle force is much lower and increase in intradiscal pressure is only about 20 and 7.5% for the vertebroplasty and kyphoplasty, respectively. Augmentation of the vertebral body with bone cement has a much smaller effect on intradiscal pressure. The increase in that case is only about 2.4% for the intact as well as for the fractured vertebra. Moreover, the effect of upper body shift after a wedge-shaped vertebral body fracture on intradiscal pressure and thus on spinal load is much more pronounced than that of stiffness increase due to cement infiltration. Maximum von Mises stress in the endplates of all lumbar vertebrae is also higher after kyphoplasty and vertebroplasty. Cement augmentation has only a minor effect on endplate stresses in the unfractured vertebrae. The advantages of kyphoplasty found in this study will be apparent only if nearly full fracture reduction is achieved. Otherwise, differences between kyphoplasty and vertebroplasty become small or vanish. Our results suggest that vertebral body fractures in the adjacent vertebrae after vertebroplasty or kyphoplasty are not induced by the elevated stiffness of the treated vertebra, but instead the anterior shift of the upper body is the dominating factor.     

椎体后凸成形术中不同骨水泥注入量的生物力学及临床疗效的相关性研究

目的：回顾分析经皮椎体成形术治疗胸腰段骨质疏松性椎体压缩骨折中不同骨水泥注射量与临床疗效的关系。同时采用三维有限元方法分析生理载荷作用下不同骨水泥量对伤椎段生物力学影响的差异。方法：选择本科2010年6月-2011年6月采用经皮椎体成形术治疗骨质疏松性椎体压缩骨折患者36例,共36个椎体。将其按注入的骨水泥量分为三组。所有患者均行椎体后凸成形术,比较术前及术后的VAS评分,ODI指数。同时利用MIMICS软件对36例骨质疏松性椎体压缩骨折椎体后凸成形术前后的CT数据进行预处理,后导入ABAQUS软件中建立三维有限元模型,设置O．3MPa轴向载荷进行生物力学分析,观察生理载荷下不同骨水泥量伤椎增强模型整体及各部分的Von Mises应力。结果：36例患者手术均获得成功,无原有症状加重或神经症状出现,5ml组2例,7ml中4例出现骨水泥渗漏。所有患者均获得随访,平均8．9月。三组术后VAS评分和ODI和术前相比均有统计学意义（P〈0．05）,但组间相比无统计学意义（P〉0．05）。不同骨水泥注入量与疼痛缓解程度无相关性。成功建立了不同骨水泥量伤椎增强椎体后凸成形术前后的三维有限元模型,当轴向压力以生理载荷0．3MPa时,骨水泥量的注入量和伤椎的刚度呈正相关。结论：椎体后凸成形术能有效缓解疼痛,和骨水泥的的注入量无明显相关性。伤椎的刚度和强度恢复和骨水泥注入量呈正相关,随着骨水泥注入量的增加,相关并发症发牛率增大。     

Comparison of vertebroplasty and kyphoplasty for complications

Vertebroplasty (VP) and kyphoplasty (KP) have been proven equally effective in providing pain relief in patients with vertebral compression fractures (VCF). Both have been reported to have multiple complications which, though rare, are potentially devastating. This literature review focuses on comparing the incidence of various types of complication of VP and KP. Local cement leakage and pulmonary cement embolism have been reported more commonly after VP than KP. It is questionable whether the relative risk of developing an adjacent level new fracture after VP is greater than after KP The relationship between a new VCF and each of these procedures has also not been clearly established. Although the majority of complications are clinically silent, their potential risks, which include a fatal outcome, should always be kept in mind by the practitioner.     

3D打印多孔钛钢板一体化植入体修复髋臼后壁粉碎性骨折合并骨缺损的初步研究

目的 :探讨应用计算机辅助设计(computer aided design,CAD)结合3D打印技术对髋臼后壁粉碎性骨折合并骨软骨缺损进行修复重建的可行性,评估多孔钛合金支架钢板一体化植入体复合氮化钛生物陶瓷涂层的生物力学性能。方法:基于连续断层CT图像,利用CAD软件来构建具有特定三维内部结构的多孔钛钢板一体化植入体数字模型,以Ti6Al4V粉末为原材料打印出实体并于其关节面复合氮化钛涂层,观察植入体与髋臼匹配和贴附情况;利用Ansys软件进行有限元建模,分析正常组、传统组及植入体组髋臼在相同载荷状态下的应力分布、应力传导及形变位移等情况,验证植入体的生物力学性能。结果:植入体的多孔钛合金支架与髋臼匹配程度良好,钢板形态基本与骨表面贴附,根据Matta复位标准评定为优。有限元分析结果显示:植入体重建后髋臼在Von Mises应力峰值13.38 MPa接近正常组13.11 MPa,小于传统组15.66 MPa;植入体重建后的髋臼在应力分布和传导与正常组基本一致,稍优于传统组;植入体的最大相对位移为0.166 mm,处于可以接受的范围。结论:3D技术制备的多孔钛合金支架钢板一体化植入体复合氮化钛涂层具备优良的匹配度和生物力学性能;解剖重建使后壁头臼应力分布及传导恢复比较理想,接近正常的髋关节,其为临床治疗髋臼后壁粉碎性骨折合并严重骨缺损的病例提供新选择。     

Peri‐implant stress correlates with bone and cement morphology: Micro‐FE modeling of implanted cadaveric glenoids

Aseptic loosening of cemented joint replacements is a complex biological and mechanical process, and remains a clinical concern especially in patients with poor bone quality. Utilizing high resolution finite element analysis of a series of implanted cadaver glenoids, the objective of this study was to quantify relationships between construct morphology and resulting mechanical stresses in cement and trabeculae. Eight glenoid cadavers were implanted with a cemented central peg implant. Specimens were imaged by micro‐CT, and subject‐specific finite element models were developed. Bone volume fraction, glenoid width, implant‐cortex distance, cement volume, cement–cortex contact, and cement–bone interface area were measured. Axial loading was applied to the implant of each model and stress distributions were characterized. Correlation analysis was completed across all specimens for pairs of morphological and mechanical variables. The amount of trabecular bone with high stress was strongly negatively correlated with both cement volume and contact between the cement and cortex (r = ?0.85 and ?0.84, p < 0.05). Bone with high stress was also correlated with both glenoid width and implant‐cortex distance. Contact between the cement and underlying cortex may dramatically reduce trabecular bone stresses surrounding the cement, and this contact depends on bone shape, cement amount, and implant positioning. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1671–1679, 2015.

     

Balloon kyphoplasty versus percutaneous vertebroplasty in treating osteoporotic vertebral compression fracture: grading the evidence through a systematic review and meta-analysis

Objective

To assess the safety and efficacy of balloon kyphoplasty (KP) compared with percutaneous vertebroplasty (VP) and provide recommendations for using these procedures to treat osteoporotic vertebral compression fractures (OVCF).

Methods

A systematic search of all studies published through March 2012 was conducted using the MEDLINE, EMBASE, OVID, ScienceDirect and Cochrane CENTRAL databases. The randomized controlled trials (RCTs) and non-randomized controlled trials that compared KP to VP and provided data on safety and clinical effects were identified. Demographic characteristics, adverse events and clinical outcomes were manually extracted from all of the selected studies. The evidence quality levels and recommendations were assessed using the GRADE system.

Results

Twelve studies encompassing 1,081 patients met the inclusion criteria. Subgroup meta-analyses were performed according to the study design. In the RCT subgroup, there were significant differences between the two procedures in short-term visual analog scale (VAS), long-term kyphosis angles, operative times and anterior vertebrae heights. In the cohort study subgroup, there were significant differences between the two procedures in short- and long-term VAS, short- and long-term Oswestry Disability Index (ODI), cement leakage rates, short- and long-term kyphosis angles, operative times and anterior vertebrae heights. However, there were no significant differences in long-term VAS or adjacent vertebral fracture rates in the RCT subgroup. There were no significant differences in short- or long-term VAS, short- or long-term ODI, cement leakage rates, adjacent vertebral fracture rates, short- or long-term kyphosis angles or anterior vertebrae heights in the CCT subgroup, and the adjacent vertebral fracture rates did not differ significantly in the cohort study subgroup. The overall GRADE system evidence quality was very low, which lowers our confidence in their recommendations.

Conclusions

KP and VP are both safe and effective surgical procedures for treating OVCF. KP may be superior to VP in patients with large kyphosis angles, vertebral fissures, fractures in the posterior edge of the vertebral body or significant height loss in the fractured vertebrae. Due to the poor quality of the evidence currently available, high-quality RCTs are required.     

椎体后凸成形术治疗骨质疏松性脊柱压缩骨折

[目的]分析椎体后凸成形术治疗骨质疏松性椎体压缩骨折的临床和影像学结果,评价其临床效果。[方法]本组43例骨质疏松性椎体压缩骨折均接受经皮椎体球囊扩张后凸成形术。其中男19例,女24例;年龄56~85岁,平均68·2岁。本组共61个椎体骨折,其中单椎体26例,两椎体骨折11例,三椎体骨折4例,四椎体骨折2例。椎体骨折部位T7~L5。术后对患者的疼痛、日常功能以及影像学结果进行了分析。[结果]所有患者随访1a以上,平均18·8个月(12~36个月)。平均VAS评分由术前8·6到术后2·3和最终随访2·7(P<0·001),Oswestry评分由术前55到术后30和最终随访35(P<0·01)。手术椎体前、中柱平均高度由术前的12·20mm到术后的25·38mm和最终随访26·36mm。脊柱矢状位后凸畸形改善平均9·9°(4·3~22°),随访丢失平均1·6°(0·8~1·7°)。4例发生骨水泥渗漏,但无严重并发症发生。最终随访时有3例患者发生3个临近节段椎体压缩骨折。[结论]球囊扩张椎体后凸成形术可有效恢复骨质疏松性骨折椎体的高度、迅速缓解疼痛、改善病人的功能,明显减少骨水泥的渗漏率,是一种安全、有效的治疗方法。     

Comparison of the biomechanical effects of posterior and anterior spine-stabilizing implants

Posteriorly and anteriorly fixed implants for stabilizing unstable spines are available on the market. Differences in the biomechanical behavior of these implant types are not yet fully clear. They were investigated using three-dimensional nonlinear finite element models of the lumbar spine in an intact state, with an anteriorly fixed MACS-TL implant and with posteriorly fixed internal fixators. The bisegmental implants spanned the L3 vertebra, and bone grafts were used with both implant types to replace parts of the two bridged discs. The computer models were loaded with partial body weight and muscle forces simulating standing, flexion, extension and axial rotation. Both implant types have reduced intersegmental rotation for flexion, extension, and axial rotation in the bridged region. The reduction is more pronounced for the MACS-TL implant. The implant type has only a minor effect on intradiscal pressure. Maximum von Mises stresses in the vertebrae are lower for flexion and extension with the MACS-TL implant than with the internal fixator. Very high stresses are predicted for flexion after insertion of internal fixators. For standing and torsion, maximum stresses differ only negligibly between the two implant types. In the period immediately after surgery, patients with osteoporotic vertebrae and who are treated with an internal spinal fixation device should therefore avoid excessive flexion. This study adds new information about the mechanical behavior of the lumbar spine after insertion of posterior and anterior spine-stabilizing implants. This information improves our biomechanical understanding of the spine.     

Three-dimensional morphometry of the L6 vertebra in the ovariectomized rat model of osteoporosis: biomechanical implications.

This article summarizes the results of a three-dimensional study of changes in the morphology of the L6 rat vertebra at 120 days after ovariectomy (OVX), with estrogen replacement therapy used as a positive control. Synchrotron radiation microtomography was used to quantify the structural parameters defining trabecular bone architecture, while finite-element methods were used to explore the relationships between these parameters and the compressive elastic behavior of the vertebrae. There was a 22% decrease in trabecular bone volume (TBV) and a 19% decline in mean trabecular thickness (Tb.Th) with OVX. This was accompanied by a 150% increase in trabecular connectivity, a result of the perforation of trabecular plates. Finite-element analysis of the trabecular bone removed from the cortical shell showed a 37% decline in the Young's modulus in compression after OVX with no appreciable change in the estrogen-treated group. The intact vertebrae (containing its trabecular bone) exhibited a 15% decrease in modulus with OVX, but this decline lacked statistical significance. OVX-induced changes in the trabecular architecture were different from those that have been observed in the proximal tibia. This difference was a consequence of the much more platelike structure of the trabecular bone in the vertebra.     

椎体成形术与后凸成形术治疗老年陈旧性骨质疏松椎体压缩性骨折的相关问题探讨

目的:探讨椎体成形术(PVP)与后凸成形术(PKP)治疗老年陈旧性骨质疏松椎体压缩性骨折的疗效和安全性。方法:自2004年12月至2008年6月,采用PVP治疗28例(40椎)骨质疏松性椎体压缩性骨折,其中男11例(14椎),女17例(26椎);年龄70～91岁,平均72岁。骨折部位T5-L5。采用PKP治疗31例(43椎),男13例(18椎),女18例(25椎);年龄70～92岁,平均74岁;骨折部位T4-L5。术后采用疼痛视觉模拟评分(visualanaloguescale,VAS)、Oswestry功能评分、后凸Cobb角、椎体前中柱的平均高度及骨水泥的渗漏率等指标来评估两组疗效。结果:两组术后VAS评分和Oswestry功能评分都有明显下降,与术前相比有统计学差异(P0.01);两组间VAS评分和Oswestry功能评分降低值无统计学意义(P0.05)。两组后凸Cobb角及椎体前中柱的平均高度与术前比较差异无统计学意义(P0.05)。骨水泥渗漏率,PVP组3个椎体(7.5%),PKP组2个椎体(4.7%),但均无神经症状。两组比较差异无统计学意义(P0.05)。结论:PVP和PKP均能有效缓解老年陈旧性骨质疏松性椎体压缩性骨折所引起的疼痛,改善患者的脊柱功能,并且是一种安全有效的治疗方法。     

Early stage disc degeneration does not have an appreciable affect on stiffness and load transfer following vertebroplasty and kyphoplasty

Vertebroplasty and kyphoplasty have been reported to alter the mechanical behavior of the treated and adjacent-level segments, and have been suggested to increase the risk for adjacent-level fractures. The intervertebral disc (IVD) plays an important role in the mechanical behavior of vertebral motion segments. Comparisons between normal and degenerative IVD motion segments following cement augmentation have yet to be reported. A microstructural finite element model of a degenerative IVD motion segment was constructed from micro-CT images. Microdamage within the vertebral body trabecular structure was used to simulate a slightly (I = 83.5% of intact stiffness), moderately (II = 57.8% of intact stiffness), and severely (III = 16.0% of intact stiffness) damaged motion segment. Six variable geometry single-segment cement repair strategies (models A–F) were studied at each damage level (I–III). IVD and bone stresses, and motion segment stiffness, were compared with the intact and baseline damage models (untreated), as well as, previous findings using normal IVD models with the same repair strategies. Overall, small differences were observed in motion segment stiffness and average stresses between the degenerative and normal disc repair models. We did however observe a reduction in endplate bulge and a redistribution in the microstructural tissue level stresses across both endplates and in the treated segment following early stage IVD degeneration. The cement augmentation strategy placing bone cement along the periphery of the vertebra (model E) proved to be the most advantageous in treating the degenerative IVD models by showing larger reductions in the average bone stresses (vertebral and endplate) as compared to the normal IVD models. Furthermore, only this repair strategy, and the complete cement fill strategy (model F), were able to restore the slightly damaged (I) motion segment stiffness above pre-damaged (intact) levels. Early stage IVD degeneration does not have an appreciable effect in motion segment stiffness and average stresses in the treated and adjacent-level segments following vertebroplasty and kyphoplasty. Placing bone cement in the periphery of the damaged vertebra in a degenerative IVD motion segment, minimizes load transfer, and may reduce the likelihood of adjacent-level fractures. Dr. Tony S. Keller’s life was tragically taken on the 6th of December 2006. Tony was a bright and energetic researcher, an outstanding teacher and mentor, and a beloved friend. He is greatly missed.     

Risks and benefits of percutaneous vertebroplasty or kyphoplasty in the management of osteoporotic vertebral fractures

Vertebral fracture (VF) is the most common osteoporotic fracture and is associated with high morbidity and mortality. Conservative treatment combining antalgic agents and rest is usually recommended for symptomatic VFs. The aim of this paper is to review the randomized controlled trials comparing the efficacy and safety of percutaneous vertebroplasty (VP) and percutaneous balloon kyphoplasty (KP) versus conservative treatment. VP and KP procedures are associated with an acceptable general safety. Although the case series investigating VP/KP have all shown an outstanding analgesic benefit, randomized controlled studies are rare and have yielded contradictory results. In several of these studies, a short-term analgesic benefit was observed, except in the prospective randomized sham-controlled studies. A long-term analgesic and functional benefit has rarely been noted. Several recent studies have shown that both VP and KP are associated with an increased risk of new VFs. These fractures are mostly VFs adjacent to the procedure, and they occur within a shorter time period than VFs in other locations. The main risk factors include the number of preexisting VFs, the number of VPs/KPs performed, age, decreased bone mineral density, and intradiscal cement leakage. It is therefore important to involve the patients to whom VP/KP is being proposed in the decision-making process. It is also essential to rapidly initiate a specific osteoporosis therapy when a VF occurs (ideally a bone anabolic treatment) so as to reduce the risk of fracture. Randomized controlled studies are necessary in order to better define the profile of patients who likely benefit the most from VP/KP.     

椎基静脉孔与椎体内裂隙相通可能是后凸成形术骨水泥渗漏的危险因素

 目的 通过对伴与不伴椎内裂隙征的椎体行经皮椎体后凸成形术（percutaneous kyphoplasty,PKP）后不同类型骨水泥渗漏的发生率的评估,探讨椎基静脉孔和椎内裂隙相通是否为骨水泥渗漏的危险因素。方法 回顾性分析2009年1月至2013年1月我科行PKP手术的224例患者的270个手术椎体术前与术后X线片、CT及MRI。所有病例依据是否存在椎体内裂隙分为裂隙组和骨小梁组。将骨水泥渗漏分为五型：通过骨皮质缺损进入椎旁软组织（A型）,通过椎基静脉孔（B型）,通过进针管道（C型）,通过骨皮质缺损进入椎间盘区域（D型）,以及通过椎旁静脉（E型）。分别统计两组各类型的骨水泥渗漏的发生率并分析差异是否有统计学意义。结果 裂隙组72例,骨小梁组198例。B型骨水泥渗漏最为常见,占总手术椎体的15.5%（42例）,其次为D型骨水泥渗漏（7.8%,21例）。裂隙组B型骨水泥渗漏发生率为23.6%,高于骨小梁组的12.6%,且两者之间差异有统计学意义（P=0.028）。其余各型骨水泥渗漏之间差异无统计学意义。结论 B型骨水泥渗漏在伴椎内裂隙征的椎体中更为常见,说明椎内裂隙征和椎基静脉孔之间存在通道。因此,在伴椎内裂隙征的椎体行PKP手术时,需特别小心避免骨水泥通过椎基静脉孔漏入椎管。     

骨填充网袋椎体成形术与经皮球囊后凸成形术治疗骨质疏松性椎体压缩性骨折

目的:探讨骨填充网袋椎体成形术治疗骨质疏松性椎体骨折的临床疗效。方法:对2015年12月至2017年6月符合纳入与排除标准的127例(145椎)骨质疏松性胸腰椎体骨折患者的临床资料进行回顾性分析,通过临床表现、X线、CT、MRI明确责任椎体,其中95例(110椎)采用经皮椎体后凸成形术治疗(PKP组),男34例(42椎),女61例(68椎),年龄(73.92±7.14)岁,胸椎47节(T_8-T_(12)),腰椎63节(L_1-L_5);另外的32例(35椎)采用骨填充网袋椎体成形术治疗(网袋组),男11例(12椎),女21例(23椎),年龄(71.56±7.89)岁,胸椎16节(T_9-T_(12)),腰椎19节(L_1-L_5)。观察患者术后3 d疼痛改善、椎体高度恢复、功能改善情况,并通过X线片观察骨水泥弥散及渗漏情况。结果:所有患者顺利完成手术,术中未出现并发症。骨填充网袋椎体成形术治疗的32例患者手术时间为(31.75±4.99)min,术后3 d的VAS评分,椎体前缘、中部高度,腰部ODI评分分别为(2.38±0.94)分、(19.54±2.36)mm、(18.16±2.65)mm和(25.19±5.49)分,各项目与术前比较明显改善(P0.01),与PKP组比较差异无统计学意义(P0.05)。术后3 d的X线片显示两组患者的骨水泥均呈斑片状、团块状或少量弥散状分布,网袋组的渗漏率为2.86%(1/35),PKP组的渗漏率为16.36%(18/110),多为"拖尾征",两组比较差异有统计学意义(P0.05)。结论:骨填充网袋椎体成形术治疗骨质疏松性椎体骨折具有类似经皮椎体后凸成形术的疗效,能够缓解疼痛,恢复部分椎体高度,并且明显减少渗漏率,是一种简单、快速、有效的治疗方法。     

椎体后凸成形术治疗多节段脊柱骨折中责任椎体的选择

目的 前瞻性研究球囊扩张椎体后凸成形术治疗多节段脊柱压缩骨折中责任椎体的选择及其疗效.方法 2002年10月至2005年6月对35例多节段骨质疏松性脊柱骨折患者,根据MRI各序列上信号的改变确定责任椎体,选择性对责任椎体进行球囊扩张椎体后凸成形术治疗.术前骨折椎体MRI有T1WI低信号改变、T2WI及STIR序列高信号改变者,即确定为责任椎体,可参考X线片表现及局部叩击痛.共计120个椎体有压缩骨折,其中确定为责任椎体并接受手术的有51个椎体.观察术后症状改善及骨折复位情况来评估其疗效.结果 35例患者均顺利完成手术,术后1～3 d完全独立或经搀扶行走.3个椎体出现无症状性骨水泥渗漏,占5.9%(3/51).31例患者获得随访,平均随访时间16.2个月.术后疼痛明显减轻或消失,视觉模拟评分(VAS)由术前8.7降至随访时的2.1(P＜0.01).随访时椎体高度平均恢复率59.17%,后凸畸形Cobb角平均矫正10.1°,术前与末次随访时比较,差异有统计学意义(P＜0.01).结论 对于多节段脊柱压缩骨折,可根据MRI不同序列上信号的改变来确定责任椎,选择性对责任椎进行球囊扩张后凸成形术治疗可获得较好疗效.     

Vertebroplastie: ein Update

Percutaneous cement augmentation (kyphoplasty and vertebroplasty) has become established as a procedure for treatment of painful osteoporotic vertebral fractures and certain neoplastic changes. The injection of cement ensures rapid stabilization of the vertebra and prevents further sintering. This also results in pain improvement. Nonetheless, based on two placebo-controlled trials, this treatment approach has been called into question. However, these studies did not take the technical aspects of the treatment into consideration, and it appears probable that the amount of filler material chosen was too small so that the treatment group also received placebo. Furthermore, it is likely that mostly older fractures were treated so that the effect can no longer be expected to be as pronounced. A randomized, controlled trial comparing kyphoplasty to conservative management provided good evidence that cement augmentation is of benefit within the first year. Newer procedures for kyphoplasty are very promising, but their clinical significance still needs verification.     

Human cancellous bone from T12-L1 vertebrae has unique microstructural and trabecular shear stress properties

Increase of trabecular stress variability with loss of bone mass has been implicated as a mechanism for increased cancellous bone fragility with age and disease. In the current study, a previous observation that trabecular shear stress estimates vary along the human spine such that the cancellous tissue from the thoracic 12 (T12)-lumbar 1 (L1) junction experiences the highest trabecular stresses for a given load was tested as a formal hypothesis using multiple human spines. Thoracic 4, T5, T7, T9, T10, T12, L1, L2, L4 and L5 vertebrae from 10 human cadaver spines were examined. One specimen in the central anterior region was cored in the supero-inferior (SI) direction and another in the postero-lateral region was cored in the transverse (TR) direction from each vertebra. Micro-CT-based large-scale finite element models were constructed for each specimen and compression in the long axis of the cylindrical specimens was simulated. Cancellous bone modulus and the mean, the standard deviation, variability and amplification of trabecular von Mises stresses were computed. Bone volume fraction, trabecular number, trabecular thickness, trabecular separation, connectivity density and degree of anisotropy were calculated using 3D stereology. The results were analyzed using a mixed model in which spine level was modeled using a quadratic polynomial. The maximum of trabecular shear stress amplification and minimum of bone volume fraction were found in the cancellous tissue from the T12-L1 location when results from the samples of the same vertebra were averaged. When groups were separated, microstructure and trabecular stresses varied with spine level, extrema being at the T12-L1 levels, for the TR specimens only. SI/TR ratio of measured parameters also had quadratic relationships with spine level, the extrema being located at T12-L1 levels for most parameters. For microstructural parameters, these ratios approached to a value of one at the T12-L1 level, suggesting that T12-L1 vertebrae have more uniform cancellous tissue properties than other levels. The mean intercept length in the secondary principal direction of trabecular orientation could account for the variation of all mechanical parameters with spine level. Our results support that cancellous tissue from T12-L1 levels is unique and may explain, in part, the higher incidence of vertebral fractures at these levels.     

Stability of pedicle screws after kyphoplasty augmentation: an experimental study to compare transpedicular screw fixation in soft and cured kyphoplasty cement

OBJECTIVE: The goal of this cadaver study was to compare the stability of pedicle screws after implantation in soft or cured kyphoplasty cement. METHODS: Pedicle screws were inserted in a total of 30 thoracolumbar vertebrae of 10 different human specimens: 10 screws were implanted in nonaugmented vertebrae (group 1), each 10 screws were placed in soft (group 2) and cured (group 3) cement. Pedicle screws were than evaluated for biomechanical axial pullout resistance. RESULTS: Mean axial pullout strength was 232 N (range 60-600 N) in group 1, 452 N (range 60-1125 N) in group 2 and 367 N (range 112-840 N) in group 3. The paired Student t-test demonstrated a significant difference between pullout strength of groups 1 and 2 (P = 0.0300). Between pullout strength of groups 1 and 3 and between groups 2 and 3 no significant difference was seen. CONCLUSION: We achieved a 1.9 times higher pullout strength with kyphoplasty augmentation of osteoporotic vertebrae compared with the pullout strength of nonaugmented vertebrae. Implantation of pedicle screws in cured cement is a sufficient method. With this method we found a 1.6 times higher pullout strength then in nonaugmented vertebrae.     

Indications and contraindications for vertebroplasty and kyphoplasty

Introduction

Vertebral fractures (VF) are a leading cause of morbidity in the elderly. In the past decade, minimally invasive bone augmentation techniques for VF, such as percutaneous vertebroplasty (VP) and kyphoplasty (KP) have become more widespread. According to the literature, both techniques provide significant pain relief. However, KP is more expensive and technically more demanding than VP. The current study surveyed German surgeons who practice percutaneous augmentation to evaluate and compare decisions regarding the implementation of these techniques. Is there a difference in the indications and contraindications of VP and KP compared with the interdisciplinary consensus paper on VP and KP of the German medical association in the treatment of VF?

Methods

A multiple choice questionnaire was designed with questions regarding diagnostic procedures, clinical and radiologic (AO classification) indications, as well as contraindications for both VP and KP. A panel of five experts refined the initial questionnaire. The final version was then sent to 580 clinics registered to practice KP in Germany. The statistical analysis was done by two authors, who collected the questionnaire data and Wilcoxon’s signed ranks test was performed for non-parametric variables with SPSS.

Results

327 of 580 questionnaires (56.4%) were completed and returned. 151 (46.2%) of participants were performing both procedures, and 176 (53.8%) performed KP only. Median duration from onset of acute pain to intervention was 3 weeks. For most participants (95.4%), consistent back pain at the fracture level with a visual analog scale score over 5 was the main clinical indication for VP and KP. A1 and A3.1 fractures from osteoporosis and metastasis were considered indications for KP. Osteoporotic A1.1 fractures were an indication for VP. Traumatic A3.2 fractures were not an indication for either procedure. Major contraindications to both procedures were active infection (94.7%), cement allergy (86.8%), and coagulation disorders (80.3%).

Conclusion

Vertebroplasty and kyphoplasty both have roles in the treatment of vertebral fractures. However, we could see differences in the indications for the two percutaneous techniques. Participants of this study found more indications for KP versus VP in cases of painful A1.2 and A3.1 fractures due to osteoporosis, metastasis, and trauma. About half of the respondents reported that VP is indicated for osteoporotic and pathologic A1.1 fractures. This study offers only limited conclusions. Open questionnaires and prospective data from all clinicians performing these procedures should be analyzed to offer more specific information.