Effect of vertebral body stiffness before and after vertebroplasty on intradiscal pressure]

Fractures of osteoporotic vertebral bodies are increasingly stabilized with bone cement. The effects of vertebral-body stiffness before and after augmentation with bone cement and of wedge-shaped vertebral body fractures on intradiscal pressure are insufficiently known. In a finite element model of the lumbar spine the elastic modulus of cancellous bone as well as the amount and the elastic modulus of bone cement were varied and the dependency of intradiscal pressure on these parameters was calculated. In addition, a wedge-shaped vertebral-body fracture was simulated. The bulge of the vertebral-body endplate and thus the intradiscal pressure depends strongly on the grade of osteoporosis in the vertebral body. The influence of amount and elastic modulus of bone cement on intradiscal pressure is small. A wedge-shaped vertebral-body fracture causes an anterior shift of upper-body centre of gravity. If this shift is not compensated, it leads to an increased flexion moment that has to be balanced by muscle forces. In addition, this shift leads to a stronger increase of intradiscal pressure than the augmentation of the vertebral body with bone cement.     

Biomechanical assessment of stability in the metastatic spine following percutaneous vertebroplasty: effects of cement distribution patterns and volume

Percutaneous vertebroplasty is a minimally invasive, radiologically guided procedure whereby bone cement is injected into structurally weakened vertebrae to provide added biomechanical stability. In addition to treating osteoporotic vertebral fractures, this technique is also used to relieve pain by stabilizing metastatically compromised vertebrae that are at risk of pathologic burst fracture. Optimal cement distribution patterns to improve biomechanical stability to metastatically involved vertebral bodies remain unknown. This study aimed to determine the effect of cement location and volume of cement injected during percutaneous vertebroplasty on improving vertebral stability in a metastatically-compromised spinal motion segment using a parametric poroelastic finite element model. A three-dimensional parametric finite element model of a thoracic spinal motion segment was developed and analyzed using commercially available software. A total of 16 metastatic pre and post vertebroplasty scenarios were investigated using a serrated spherical representation of tumor tissue and various geometric representations of polymethylmethacrylate (PMMA). The effect of vertebroplasty on vertebral bulge, a measure of posterior vertebral body wall motion as an indicator of burst fracture initiation, was assessed. In all cases, vertebroplasty reduced vertebral bulge, but the risk of the initiation of burst fracture was minimized with cement located posterior to the tumor, near the posterior vertebral body wall. Vertebral bulge decreased by up to 62% with 20% cement injection. These findings demonstrate that location and distribution of cement within the vertebral body has a noticeable effect on the restoration of biomechanical stability following percutaneous vertebroplasty.     

骨质疏松椎体压缩性骨折患者经皮椎体成形术后再次骨折的危险因素分析

目的:探讨骨质疏松椎体压缩骨折患者接受椎体成形术后再次新发骨折的危险因素。方法:选取2009年1月到2015年1月就诊于我院诊断为骨质疏松椎体压缩性骨折且行经皮椎体成形术的患者,收集患者的诊疗信息及影像学资料。收集患者的年龄、性别等基本资料及基于定量CT测量的骨矿物含量、骨水泥注射占椎体体积的比、骨水泥的分布及骨水泥的渗漏情况。将单椎体骨折且在随访时间内再次新发椎体骨折的患者分为A组,未骨折的患者分为B组,对比分析两组之间的参数的差异,并利用二项Logistic回归分析分析再次骨折的危险因素。结果:共有287例患者纳入研究,平均随访时间为34.7±17.8个月,压缩性骨折最常见的椎体依次为L1(29.1%)、T12(20.8%)及L2(13.5%)。在随访时间内共有32例患者再次发生椎体骨折。252例单椎体骨折患者中,26例(A组)再次发生骨折,226例(B组)未发生骨折。A组骨矿物含量低于B组(P0.001),骨水泥分布较B组差(P0.001),年龄高于B组(P0.001)且骨水泥渗漏发生率(34.6%)高于B组(13.7%)(P=0.006),两组在骨水泥占椎体的比、后凸程度、性别比例没有统计学差异。回归分析显示骨矿物含量(OR=1.092,P0.001)、年龄(OR=1.091,P0.001)及骨水泥渗漏(OR=1.200,P=0.002)均是再次骨折的危险因素,骨水泥的均匀分布是保护因素(OR=0.922,P0.001)。结论:年龄较大且骨质较差的患者容易再次发生椎体骨折,在行椎体成形术过程中应尽量使骨水泥均匀分布并避免骨水泥的渗漏。     

网袋强化椎体成形术在骨质疏松椎体骨折治疗中的经验教训

摘要 目的：探讨和总结使用网袋强化椎体成形术在骨质疏松椎体骨折围手术期的注意事项及相关对策。方法：回顾性分析2017年6月到2020年6月3年时间内,使用网袋强化椎体成形术治疗骨质疏松性椎体骨折患者共计112例。统计和比较患者在围手术期的各项指标,分析穿刺失败的原因及相关危险因素。结果：112例患者共涉及138个椎体。其中一期穿刺失败率（骨水泥分布不佳）为47个,占34.0%。骨水泥注入3 mL以下者为19个,占13.8%。骨水泥渗漏为36个,占26.1%。所有患者在术后3天及3月复查, VAS评分和ODI评分较前均有显著改善(P<0.05)。所有患者均未出现严重并发症(P>0.05)。结论：网袋强化椎体成形术在骨质疏松性椎体骨折的治疗中是一种理想的治疗方式,但在具体过程中仍有相关的经验和教训需要整理和总结。     

Mechanics of bone/PMMA composite structures: an in vitro study of human vertebrae

The goal of this study was to provide material property data for the cement/bone composite resulting from the introduction of PMMA bone cement into human vertebral bodies. A series of quasistatic tensile and compressive mechanical tests were conducted using cement/bone composite structures machined from cement-infiltrated vertebral bodies. Experiments were performed both at room temperature and at body temperature. We found that the modulus of the composite structures was lower than bulk cement (p<0.0001). For compression at 37( composite function)C: composite =2.3+/-0.5GPa, cement =3.1+/-0.2GPa; at 23( composite function)C: composite =3.0+/-0.3GPa, cement =3.4+/-0.2GPa. Specimens tested at room temperature were stiffer than those tested at body temperature (p=0.0004). Yield and ultimate strength factors for the composite were all diminished (55-87%) when compared to cement properties. In general, computational models have assumed that cement/bone composite had the same modulus as cement. The results of this study suggest that computational models of cement infiltrated vertebrae and cemented arthroplasties could be improved by specifying different material properties for cement and cement/bone composite.     

椎体静脉稀疏区注入骨水泥对PVP术中骨水泥渗漏的影响

目的:探讨椎体静脉稀疏区注入骨水泥对骨质疏松椎体压缩性骨折患者行经皮穿刺椎体成形术(percutaneous vertebroplasty,PVP)术中骨水泥渗漏的影响。方法:选择西安交通大学第二附属医院2014年1月至2018年6月收治的61例骨质疏松椎体压缩性骨折患者,根据骨水泥注入区域的不同,将所有患者分为A组(30例)及B组(31例),A组骨水泥注入区域为椎体静脉密集区(椎体中1/3平面处),B组骨水泥注入区域为椎体静脉稀疏区(椎体上1/3及下1/3平面处),对比两组的骨水泥渗漏率,术前、术后6个月时的视觉模拟评分(Visual analogue scale,VAS),治疗中的骨水泥用量、椎体高度恢复率及cobb角恢复度数。结果:B组的骨水泥渗漏率及骨水泥用量均明显低于A组(P0.05)。两组的VAS评分、椎体高度恢复率、cobb角恢复情况对比差异无统计学意义(P0.05)。结论:与椎体静脉密集区相比,在椎体静脉稀疏区注入骨水泥可显著降低骨质疏松椎体压缩性骨折患者PVP术中骨水泥渗漏率,椎体静脉稀疏区可作为PVP术中骨水泥注射的一个相对安全区域。     

不同黏度骨水泥治疗骨质疏松性椎体压缩性骨折疗效比较

目的:探讨不同黏度骨水泥治疗骨质疏松性椎体压缩性骨折的临床疗效。方法:选择2016年1月～2018年6月滁州市第一人民医院收治的骨质疏松性椎体压缩性骨折患者90例,按照随机数字表法分为高黏度组42例和低黏度组48例,分别采用高黏度骨水泥经皮椎体后凸成形术和低黏度骨水泥经皮椎体后凸成形术治疗。比较两组单个椎体手术时间、骨水泥注入量、骨水泥渗漏发生情况。所有患者术后随访3个月,比较两组术前、术后3个月疼痛数字评分量表(NRS)评分、Oswestry功能(ODI)评分、椎体中间高度和Cobb角变化。结果:高黏度组单个椎体手术时间少于低黏度组(P0.05),两组骨水泥注入量、骨水泥弥散体积比较无统计学差异(P0.05)。高黏度组骨水泥总渗漏率低于低黏度组(P0.05)。两组患者术前NRS评分、ODI评分、椎体中间高度和Cobb角比较差异无统计学意义(P0.05);术后3个月两组NRS评分、ODI评分和Cobb角较术前降低,椎体中间高度较术前升高,且高黏度组NRS评分、ODI评分和Cobb角低于低黏度组,椎体中间高度高于低黏度组(P0.05)。结论:高黏度骨水泥经皮椎体后凸成形术治疗骨质疏松性椎体压缩性骨折的疗效较低黏度骨水泥更佳,术后总渗漏率更低,脊柱畸形矫正、脊柱功能恢复更佳,同时疼痛也明显降低,适于临床推广。     

经皮椎体后凸成形术对骨质疏松性椎体压缩骨折的相关并发症的预后评价

目的：评价经皮椎体后凸成形术（Percutaneous kyphoplasty,PKP）对骨质疏松性椎体压缩骨折（Osteoporotic vertebral body compression的ctures,OVCFs）的相关并发症的预后。方法：回顾性分析我院2009年5月-2011年4月收治的行PKP治疗的172例OVCFs患者,按照其并发症情况分为发生组（n=22）及未发生组（n=150）,分析并发症发生的原因及对预后的影响。结果：术后共有22例患者出现并发症,发生率12_8％。其中骨水泥渗漏15例（68．2％）,骨水泥椎弓根拖尾7例（31．8％）,未见切口感染、肺栓塞等其他并发症。两组患者麻醉情况、手术时间、术中出血量和骨水泥注入量无明显统计学差异;两组患者治疗后VAS评分、后凸Cobb角显著降低,椎体前缘高度及椎体中部高度显著增加（P〈0．05）,但组间对比均无明显统计学差异,其改善率亦未见明显统计学差异（P〉0．05）。结论：PKP治疗OVCFs可取得良好的疗效,但也会带来骨水泥渗漏、骨水泥椎弓根拖尾等并发症,虽对患者的疼痛及躯体功能等预后无明显不良影响,但部分患者可出现神经受损、肺栓塞等继发疾病,严重影响其生存质量,因此,在今后的治疗中,应严格规范各项诊疗操作,有效控制PKP并发症的发生,从而改善其生存质量。     

PKP治疗骨质疏松性椎体压缩骨折的预后评价及继发危险因素分析

目的:分析椎弓根入路行椎体后凸成形术(PKP)治疗骨质疏松性椎体压缩骨折的预后评价及继发危险因素分析。方法:选择2016年2月-2018年2月我院收治的骨质疏松性椎体压缩骨折患者85例纳入本次研究,采用随机数表法分为观察组(n=43)和对照组(n=42)。对照组使用经皮椎体成形术进行治疗,观察组采用PKP进行治疗。比较两组患者手术情况、术后情况、椎体前缘高度丢失率、Cobb角、继发性骨折发生情况及分析骨质疏松性椎体压缩骨折患者术后继发骨折的危险因素。结果:观察组手术时间、透视次数、骨水泥注入量、术中出血量均显著低于对照组,差异显著(P0.05);观察组疼痛缓解时间、下地时间及住院时间均显著低于对照组,差异显著(P0.05);治疗前,两组椎体前缘高度丢失率、Cobb角比较,无显著差异;治疗后,两组患者的椎体高度丢失率明显下降,但两组术后7 d、术后6月两组椎体前缘高度丢失率、Cobb角比较无显著差异;观察组术后12月椎体前缘高度丢失率、Cobb角低于对照组,差异显著(P0.05);所有患者均随访12月,其中22例(25.88%)发生继发性椎体骨折,进行单因素分析,结果发现,两组患者性别、骨折部位、局部矢状面后凸角度、骨水泥量、椎体高度恢复、术后抗骨质疏松治疗差异无统计学意义(P0.05);骨质疏松原因、骨水泥椎间隙渗漏、术后支具佩戴、原发骨折类型与骨质疏松性椎体压缩骨折患者术后发生继发骨折相关(P0.05)。多因素Logistic分析显示,骨质疏松原因、骨水泥椎间隙渗漏、术后支具佩戴、原发骨折类型均是骨质疏松性椎体压缩骨折患者术后发生继发骨折的独立危险因素(P0.05)。结论:在骨质疏松性椎体压缩骨折患者中应用PKP可有效改善手术情况,随着时间的延长,PKP更有利于维持患者椎体高度;骨质疏松原因、骨水泥椎间隙渗漏、术后支具佩戴、原发骨折类型是骨质疏松性椎体压缩骨折患者术后发生继发骨折的危险因素,临床上对于具有危险因素的患者引起重视,并采取干预措施。     

单侧与双侧PVP治疗骨质疏松性椎体压缩骨折临床疗效比较及骨水泥渗漏的危险因素分析

摘要 目的：比较单侧与双侧经皮椎体成形术（PVP）治疗骨质疏松性椎体压缩骨折（OVCF）的临床疗效,并分析骨水泥渗漏的危险因素。方法：回顾性分析2019年5月~2020年12月期间本院收治的205例OVCF患者的临床资料,根据入路方式的不同分为单侧组和双侧组,例数分别为104例和101例。对比两组围术期指标、视觉模拟评分（VAS）、Oswestry功能障碍指数（ODI）、Cobb''s角和椎体前缘高度,记录两组骨水泥渗漏及其他并发症发生情况,采用单因素及多因素Logistic回归分析骨水泥渗漏的影响因素。结果：与双侧组相比,单侧组手术时间缩短,骨水泥注入量、术中透视次数减少（P<0.05）。两组术前、术后3个月、末次随访时VAS、ODI评分均呈下降趋势（P<0.05）。与术前相比,两组术后3个月及末次随访时的椎体前缘高度均升高,Cobb''s角均缩小（P<0.05）。两组并发症发生率组间对比无统计学差异（P>0.05）。PVP患者骨水泥渗漏与骨水泥黏度、皮质断裂、骨折严重程度、骨折位置、年龄、CT值、骨水泥注入量有关（P<0.05）。骨水泥渗漏的危险因素主要有骨水泥注入量>6 mL、骨折严重程度为重度、CT值>63HU、骨水泥黏度为低、皮质断裂（P<0.05）。结论：单侧与双侧PVP治疗OVCF效果相当。其中单侧可减少骨水泥注入量,缩短手术时间,减轻术后疼痛,促进术后功能恢复。而PVP手术最常见的并发症为骨水泥渗漏,受到骨折严重程度、皮质断裂、骨水泥黏度等因素的影响。     

Exercise-induced lordosis in zebrafish Danio rerio (Hamilton, 1822)

The anabolic effect of exercise on muscles and bones is well documented. In teleost fish, exercise has been shown to accelerate skeletogenesis, to increase bone volume, and to change the shape of vertebral bodies. Still, increased swimming has also been reported to induce malformations of the teleost vertebral column, particularly lordosis. This study examines whether zebrafish (Danio rerio) develops lordosis as a result of continuous physical exercise. Zebrafish were subjected, for 1 week, to an increased swimming exercise of 5.0, 6.5 or 8.0 total body lengths (TL) per second. Control and exercise group zebrafish were examined for the presence of vertebral abnormalities, by in vivo examination, whole mount staining for bone and cartilage and histology and micro-computed tomography (CT) scanning. Exercise zebrafish developed a significantly higher rate of lordosis in the haemal part of the vertebral column. At the end of the experiment, the frequency of lordosis in the control groups was 0.5 ± 1.3% and that in the exercise groups was 7.5 ± 10.6%, 47.5 ± 10.6% and 92.5 ± 6.0% of 5.0, 6.5 and 8.0 TL∙s⁻¹, respectively. Histological analysis and CT scanning revealed abnormal vertebrae with dorsal folding of the vertebral body end plates. Possible mechanisms that trigger lordotic spine malformations are discussed. This is the first study to report a quick, reliable and welfare-compatible method of inducing skeletal abnormalities in a vertebrate model during the post-embryonic period.     

Mechanical variables affecting balloon kyphoplasty outcome--a finite element study

It is still unclear how a vertebral fracture should be stabilised and strengthened without endangering the remaining intact bone of the augmented vertebra or the adjacent vertebrae. Numerical modelling may provide insight. To date, however, few finite element (FE) spine models have been developed which are both multi-segmental and capture a more complete anatomy of the vertebrae. A 3-D, two-functional unit, CT-based, lumbar spine, FE model was developed and used to predict load transfer and likelihood of fracture following balloon kyphoplasty. The fractured anterior wall and injected cement were modelled in a two-functional spinal unit model with osteoporotic bone properties. Parameters investigated included: cement stiffness, cement volume and height restoration. Models were assessed based on stresses and a user-defined fracture-predicting field. Augmentation altered the stress distribution; shielding was dependent on positioning of the cement; and fracture algorithm found incomplete height restoration to increase the likelihood of fracture, particularly in adjacent vertebrae.     

Theoretical analysis of alendronate and risedronate effects on canine vertebral remodeling and microdamage

Bisphosphonates suppress bone remodeling activity, increase bone volume, and significantly reduce fracture risk in individuals with osteoporosis and other metabolic bone diseases. The objectives of the current study were to develop a mathematical model that simulates control and 1 year experimental results following bisphosphonate treatment (alendronate or risedronate) in the canine fourth lumbar vertebral body, validate the model by comparing simulation predictions to 3 year experimental results, and then use the model to predict potential long term effects of bisphosphonates on remodeling and microdamage accumulation. To investigate the effects of bisphosphonates on bone volume and microdamage, a mechanistic biological model was modified from previous versions to simulate remodeling in a representative volume of vertebral trabecular bone in dogs treated with various doses of alendronate or risedronate, including doses equivalent to those used for treatment of post-menopausal osteoporosis in humans. Bisphosphonates were assumed to affect remodeling by suppressing basic multicellular unit activation and reducing resorption area. Model simulation results for trabecular bone volume fraction, microdamage, and activation frequency following 1 year of bisphosphonate treatment are consistent with experimental measurements. The model predicts that trabecular bone volume initially increases rapidly with 1 year of bisphosphonate treatment, and continues to slowly rise between 1 and 3 years of treatment. The model also predicts that microdamage initially increases rapidly, 0.5–1.5-fold for alendronate or risedronate during the first year of treatment, and reaches its maximum value by 2.5 years before trending downward for all dosages. The model developed in this study suggests that increasing bone volume fraction with long term bisphosphonate treatment may sufficiently reduce strain and damage formation rate so that microdamage does not accumulate above that which is initiated in the first two years of treatment.     

Modeling the mechanical consequences of vibratory loading in the vertebral body: microscale effects

Osteoporosis affects nearly 10 million individuals in the United States. Conventional treatments include anti-resorptive drug therapies, but recently, it has been demonstrated that delivering a low magnitude, dynamic stimulus via whole body vibration can have an osteogenic effect without the need for large magnitude strain stimulus. Vibration of the vertebral body induces a range of stimuli that may account for the anabolic response including low magnitude strains, interfacial shear stress due to marrow movement, and blood transport. In order to evaluate the relative importance of these stimuli, we integrated a microstructural model of vertebral cancellous bone with a mixture theory model of the vertebral body. The predicted shear stresses on the surfaces of the trabeculae during vibratory loading are in the range of values considered to be stimulatory and increase with increasing solid volume fraction. Peak volumetric blood flow rates also varied with strain amplitude and frequency, but exhibited little dependence on solid volume fraction. These results suggest that fluid shear stress governs the response of the vertebrae to whole body vibration and that the marrow viscosity is a critical parameter which modulates the shear stress.     

Compressive fatigue properties of a commercially available acrylic bone cement for vertebroplasty

Acrylic bone cements are widely used for fixation of joint prostheses as well as for vertebral body augmentation procedures of vertebroplasty and balloon kyphoplasty, with the cement zone(s) being subjected to repeated mechanical loading in each of these applications. Although, in vertebroplasty and balloon kyphoplasty, the cement zone is exposed to mainly cyclical compressive load, the compressive fatigue properties of acrylic bone cements used in these procedures are yet to be determined. The purposes of the present study were to determine the compressive fatigue properties of a commercially available cement brand used in vertebroplasty, including the effect of frequency on these properties; to identify the cement failure modes under compressive cyclical load; and to introduce a screening method that may be used to shorten the lengthy character of the standardized fatigue tests. Osteopal \({^\circledR } \mathrm{V}\) was used as the model cement in this study. The combinations of maximum stress and frequency used were 50.0, 55.0, 60.0, 62.5 and 75.5 MPa at 2 Hz; and of 40.0, 55.0, 60.0, 62.5 or 75.5 MPa at 10 Hz. Through analysis of nominal strain-number of loading cycles results, three cement failure modes were identified. The estimated mean fatigue limit at 2 Hz (55.4 MPa) was significantly higher than that at 10 Hz (41.1 MPa). The estimated fatigue limit at 2 Hz is much higher than stresses commonly found in the spine and also higher than that for other acrylic bone cements tested in a full tension–compression fatigue test, which indicates that tension–compression fatigue testing may substantially underestimate the performance of cements intended for vertebroplasty. A screening method was introduced which may be used to shorten the time spent in performing compressive fatigue tests on specimens of acrylic bone cement for use in vertebral body augmentation procedures.     

Parametric finite element analysis of vertebral bodies affected by tumors

The vertebral column is the most frequent site of metastatic involvement of the skeleton. Due to the proximity to the spinal cord, from 5% to 10% of all cancer patients develop neurologic manifestations. As a consequence, fracture risk prediction has significant clinical importance. In this study, we model the metastatically involved vertebra so as to parametrically investigate the effects of tumor size, material properties and compressive loading rate on vertebral strength. A two-dimensional axisymmetric finite element model of a spinal motion segment consisting of the first lumbar vertebral body (no posterior elements) and adjacent intervertebral disc was developed to allow the inclusion of a centrally located tumor in the vertebral body. After evaluating elastic, mixed, and poroelastic formulations, we concluded that the poroelastic representation was most suitable for modeling the metastatically involved vertebra's response to compressive load. Maximum principal strains were used to localize regions of potential vertebral trabecular bone failure. Radial and axial vertebral body displacements were used as relative indicators of spinal canal encroachment and endplate failure. Increased tumor size and loading rate, and reduced trabecular bone density all elevated axial and radial displacements and maximum tensile strains. The results of this parametric study suggest that vertebral tumor size and bone density contribute significantly to a patients risk for vertebral fracture and should be incorporated in clinical assessment paradigms.     

Biomechanical allometry in hominoid thoracic vertebrae

Considerable differences in spinal morphology have been noted between humans and other hominoids. Although comparative analyses of the external morphology of vertebrae have been performed, much less is known regarding variations in internal morphology (density) and biomechanical performance among humans and closely related non-human primates. In the current study we utilize density calibrated computed tomography images of thoracic vertebral bodies from hominoids (n = 8-15 per species, human specimens 20-40 years of age) to obtain estimates of vertebral bone strength in axial compression and anteroposterior bending and to determine how estimates of strength scale with animal body mass. Our biomechanical analysis suggests that the strength of thoracic vertebral bodies is related to body mass (M) through power law relationships (y ∝ M^b) in which the exponent b is 0.89 (reduced major axis) for prediction of axial compressive strength and is equal to 1.89 (reduced major axis) for prediction of bending strength. No differences in the relationship between body mass and strength were observed among hominoids. However, thoracic vertebrae from humans were found to be disproportionately larger in terms of vertebral length (distance between cranial and caudal endplates) and overall vertebral body volume (p < 0.05). Additionally, vertebral bodies from humans were significantly less dense than in other hominoids (p < 0.05). We suggest that reduced density in human vertebral bodies is a result of a systemic increase in porosity of cancellous bone in humans, while increased vertebral body volume and length are a result of functional adaptation during growth resulting in a vertebral bone structure that is just as strong, relative to body mass, as in other hominoids.     

经皮椎体成形术治疗骨质疏松性椎体压缩骨折的临床疗效及术后邻近椎体骨折的危险因素分析

摘要 目的：观察骨质疏松性椎体压缩骨折（OVCFs）患者以经皮椎体成形术（PVP）治疗后的临床疗效,并分析术后邻近椎体骨折的危险因素。方法：选取我院2018年6月~2020年9月期间收治的OVCFs患者180例,给予PVP治疗,观察其治疗效果、骨水泥渗漏情况、术后邻近椎体骨折发生情况,采用单因素及多因素Logistic回归分析术后邻近椎体骨折的危险因素。结果：OVCFs患者术前~术后6个月功能障碍指数（ODI）、疼痛视觉模拟评分（VAS）、活动能力评分（LAS）均呈降低趋势（P＜0.05）。随访期间,180例患者中,15例（8.33%）出现了骨水泥渗漏,但均不需要进一步处理。32例（17.78%）出现了术后邻近椎体骨折,148例未出现术后邻近椎体骨折,并以此进行分组。再骨折组、未再骨折组在年龄、骨折病史、骨密度、Cobb角、椎体高度恢复、骨水泥渗漏情况、使用抗骨质疏松药物方面对比有明显差异（P<0.05）。年龄>70岁、骨水泥渗漏、骨密度<-2.5SD、未使用抗骨质疏松药物、Cobb角<15°、椎体高度恢复率>87%均是PVP术后邻近椎体骨折的危险因素（P<0.05）。结论：PVP治疗OVCFs疗效较好,可缓解患者疼痛、减轻功能障碍、改善活动能力,术后邻近椎体骨折的发生受年龄、骨密度、Cobb角等多种因素影响,临床可针对这些因素给予对应的干预措施。     

The effects of bone and pore volume fraction on the mechanical properties of PMMA/bone biopsies extracted from augmented vertebrae

Vertebroplasty forms a porous PMMA/bone composite which was shown to be weaker and less stiff than pure PMMA. It is not known what determines the mechanical properties of such composites in detail. This study investigated the effects of bone volume fraction (BV/TV), cement porosity (PV/(TV-BV), PV…pore volume) and cement stiffness. Nine human vertebral bodies were augmented with either standard or low-modulus PMMA cement and scanned with a HR-pQCT system before and after augmentation. Fourteen cylindrical PMMA/bone biopsies were extracted from the augmented region, scanned with a micro-CT system and tested in compression until failure. Micro-finite element (FE) models of the complete biopsies, of the trabecular bone alone as well as of the porous cement alone were generated from CT images to gain more insight into the role of bone and pores. PV/(TV-BV) and experimental moduli of standard/low-modulus cement (R(2)=0.91/0.98) as well as PV/(TV-BV) and yield stresses (R(2)=0.92/0.83) were highly correlated. No correlation between BV/TV (ranging from 0.057 to 0.138) and elastic moduli was observed (R(2)< 0.05). Interestingly, the micro-FE models of the porous cement alone reproduced the experimental elastic moduli of the standard/low-modulus cement biopsies (R(2)=0.75/0.76) more accurately than the models with bone (R(2)=0.58/0.31). In conclusion, the mechanical properties of the biopsies were mainly determined by the cement porosity and the cement material properties. The study showed that bone tissue inside the biopsies was mechanically "switched off" such that load was carried essentially by the porous PMMA.     

Apparent Young's modulus of vertebral cortico-cancellous bone specimens

Up to now, due to cortical thickness and imaging resolution, it is not possible to derive subject-specific mechanical properties on the 'vertebral shell' from imaging modalities applicable in vivo. As a first step, the goal of this study was to assess the apparent Young's modulus of vertebral cortico-cancellous bone specimens using an inverse method. A total of 22 cortico-cancellous specimens were harvested from 22 vertebral bodies. All specimens were tested in compression until failure. To compute the apparent Young's modulus of the specimen from the inverse method, the boundary conditions of the biomechanical experiments were faithfully reproduced in a finite element model (FEM), and an optimisation routine was used. The results showed a mean of the apparent Young's modulus of 374?±?208?MPa, ranging from 87 to 791?MPa. By computing an apparent Young's modulus of a cortico-cancellous medium, this study gives mechanical data for an FEM of an entire vertebra including an external shell combining both bone tissues.