经皮穿刺脊椎成形术中聚甲基丙烯酸甲酯对心血管系统的影响

目的:评估经皮穿刺脊椎成形术(PVP)中注射聚甲基丙烯酸甲酯(PMMA)对患者心血管系统的影响。方法:对48例实施PVP患者分别于术前、PMMA注射过程中、注射后监测平均动脉压(MAP)、心率、脉搏及脉搏氧饱和度(SpO2),并应用多元回归模型分析心血管系统变化及与并发症的关联性。结果:MAP在PMMA注射中、注射后5 min、10 min分别为94.0 mmHg、97.3 mmHg和97.5 mmHg,与注射前(92.2 mmHg)比较差异无统计学意义(P=0.19,0.23,0.24);心率在注射中、注射后5 min、10 min平均分别为80.5/min、80.4/min和80.0/min,与注射前(80.5/min)比较差异无统计学意义(P=0.71,0.92,0.65);SpO2在注射中、注射后5 min、10 min分别为98.0%、98.0%和97.4%,与注射前(98.0%)比较差异无统计学意义(P=0.80,0.89);SpO2的4个最低值出现在注射后10 min,与注射前比较,差异具有统计学意义(P=0.007),但SpO2平均值与注射前比较差异无统计学意义(P>0.05)。PVP中PMMA的注射与机体心血管变化无显著性关联。结论:PVP中注射PMMA安全,对心血管无明显影响。     

Long-term follow-up of vertebral osteoporotic fractures treated by percutaneous vertebroplasty

The aim of this study was:to assess the long-term efficacy and safety of percutaneous vertebroplasty (PVP) for treating painful vertebral osteoporotic fractures, and to estimate the risk of vertebral fracture in the vicinity of a cemented vertebra. A prospective open study was conducted. PVP were carried out between July 1995 and September 2000 for 16 patients with symptomatic osteoporotic vertebral fracture that had not responded to extensive conservative medical therapy. All the patients were followed-up for more than 1 year. The efficacy of the PVP was assessed by the changes over time in pain on Huskissons visual analog scale (VAS) and on the McGill-Melzack scoring system (MGM). The efficacy of the procedure was also assessed by measuring the changes over time in quality of life assessed by the Nottingham Health Profile (NHP instrument): twenty-one vertebrae treated by PVP in 16 patients were evaluated. The mean duration of follow-up was 35 months. Pain assessed by the VAS significantly decreased from a mean of 71.4 mm±13 before PVP to 36 mm±30 after 6 months, and to 39 mm±33 at the time of maximal follow-up (p<0.05 for both comparisons). The results were also significant for the MGM: 3.00±0.57 before PVP to 1.6±1.4 at the long-term follow-up (p<0.05). The solely statistically significant decrease for quality of life was noted for pain. A slight but not significant improvement was noted for 3/6 dimensions of the NHP scores. A slight but significant increase in social isolation was also found. No severe complication occurred immediately after PVP. At the long term follow-up (35 months) there was a slight but not significantly increased risk of vertebral fracture in the vicinity of a cemented vertebra: odds ratio 3.18 (95% confidence interval (CI) 0.51–19.64). The odds ratio of a vertebral fracture in the vicinity of an uncemented fractured vertebra was 2.14 (95% CI: 0.17–26.31). In conclusion, PVP appears to be safe and effective for treating persistent painful osteoporotic fractures. Controlled studies with long-term follow-up are needed to evaluate the risk of vertebral fractures in the vicinity of a cemented vertebra. Abbreviations MGM McGill-Melzack scoring system - PVP Percutaneous vertebroplasty - VAS Visual analog scale     

Biomechanical behavior of MRI-signal-inducing bone cements after vertebroplasty in osteoporotic vertebral bodies: An experimental cadaver study

Background

Conventional water-free polymethylmethacrylate cements are not MRI visible due to the lack of free protons. A new MRI-visible bone cement was developed through the addition of a contrast agent and either a saline solution or a hydroxyapatite (Wichlas et al., 2010). The purposes of the study were to examine the influence of the two MRI-signal-inducing cements on the biomechanical behavior of cadaveric osteoporotic vertebral bodies after vertebroplasty and to compare the performance of the cements with conventional polymethylmethacrylate cement.

Methods

Three different cements were used: standard polymethylmethacrylate cement and two modified MRI-signal-inducing cements that were mixed with either a 0.9% saline solution or a hydroxyapatite. The modulus of elasticity for the standard polymethylmethacrylate cement was 2040 MPa, and the moduli for the MRI-signal-inducing cements that were mixed with a 0.9% saline solution and a hydroxyapatite were 1477 and 1225 MPa, respectively. The lumbar vertebral bodies from nine osteoporotic spines (mean age = 87 years, range = 78–99 years) of female cadavers were examined. Three groups were formed: polymethylmethacrylate cement with saline solution (n = 14), polymethylmethacrylate cement with hydroxyapatite (n = 12) and polymethylmethacrylate cement (n = 13). The vertebral bodies were biomechanically tested before and after vertebroplasty. Stiffness was chosen as the primary biomechanical parameter.

Findings

The vertebral body stiffness was nearly two-fold greater after vertebroplasty, and this increase was statistically significant for every group. All the groups had similar vertebral body stiffness value before and after the vertebroplasty. The UNIANOVA test for multivariate analysis of variance showed no influence of lumbar level, injected cement volume and initial vertebral body stiffness.

Interpretation

The elastic moduli of the cements appear to exert little influence on the biomechanical values when the cement is in the vertebral body. Based on the direct comparison with the classic polymethylmethacrylate cement, we believe that the implementation of such cements for MRI-guided vertebroplasties is feasible.     

椎体成形术的实验研究

目的　通过对骨质疏松的山羊椎体成形探讨椎体成形术的安全性和临床应用依据。材料与方法　将 5只复制成功的骨质疏松的山羊每只取 3个椎体 (L1～L5)共 15个椎体作为手术组 ,2个椎体 (L1～L5)共 10个椎体作对照组。手术解剖出椎弓根直视下椎体穿刺 ,注入聚甲基丙烯酸甲酯 (PMMA ,骨水泥 )。测量椎体中心、椎体前缘和椎体后缘的温度变化。CT检查椎体骨水泥充填情况。 3天后处死动物每只取 1个注射椎体共 5个椎体行病理检查。将另 10个注射椎体和 10个未手术对照组椎体游离成单个椎体 ,去掉椎间盘和椎体附件 ,双盲法测量其纵向最大负载、极限强度、弹性模量。结果　注射后椎体的最大负载、极限强度、弹性模量比对照组明显提高 (P <0 .0 5 )。注射骨水泥后椎体内中心温度为 5 1.12℃ ,椎体前缘 37.31℃ ,后缘 37.6 1℃。大体病理和显微病理显示骨水泥弥散在椎体内骨小梁间呈不均匀分布 ,同CT检查结果一致。结论　掌握适宜的粉液比例和注射时机是椎体成形术的关键因素 ,椎体内注入骨水泥可显著增强其纵向最大负载、极限强度、弹性模量     

Comparative evaluation of the diffusion of tobramycin and cefotaxime out of antibiotic-impregnated polymethylmethacrylate beads

Both tobramycin and cefotaxime diffuse from antibiotic-impregnated polymethylmethacrylate (PMMA) beads in quantities sufficient to inhibit the growth of bacteria on agar lawns or in broth cultures over a 28-day period. Extraction of antibiotic from tobramycin or cefotaxime-impregnated PMMA beads revealed that substantial amounts of both antibiotics remained within the beads despite 28 days of diffusion. Diffusion of antibiotic from the PMMA beads during the initial 3-5 days is much greater than occurs for the remainder of the 4-week period. The results of the study suggest that perhaps tobramycin of cefotaxime-impregnated PMMA beads would produce local levels of antibiotic high enough to sterilize a given dead space for a period of 28 days.     

Toxicity of polymethylmethacrylate thermodegradation products

Polymethylmethacrylate was thermally degraded in air at 300° C and the volatile decomposition products studied with gas chromatography-mass spectrometry. The main product was monomeric methacrylate, although many other compounds existed among the products. Electron spin resonance spectroscopy revealed the presence of free radicals. Wistar rats were exposed to the fumes of the plastic (300° C) and their lungs and brain studied for biochemical effects. In the lung, the activity of 7-ethoxycoumarin O-deethylase decreased and an initial inhibition of glutathione peroxidase and superoxide dismutase was observed. The contents of reduced nonprotein sulfhydryl groups were decreased in the lung and brain. The exposures enhanced the activities of acetylcholine esterase, creatine kinase and NADPH-diaphorase in the brain. Scanning electron microscopy of the exposed lungs showed disorganization of ciliated cells, and the epithelial serous cells (Clara cells) were damaged.     

两种不同方法提高椎弓根螺钉稳定性的体外生物力学研究

目的 比较膨胀式椎弓根螺钉(EPS)与骨水泥(PMMA)强化方法在体外提高螺钉稳定性的效果.方法 将60个新鲜成年绵羊腰椎随机分为三组.普通椎弓根螺钉组(CPS组):直接拧入普通椎弓根螺钉;PMMA-PS组:向钉道内注入PMMA(1.0 ml)后拧入CPS;EPS组:直接拧入EPS.24 h后对所有标本进行X线检查,随...     

Polymethylmethacrylate augmentation of the pedicle screw: the cement distribution in the vertebral body

Many studies have proven that the polymethylmethacrylate (PMMA) augmentation of the pedicle screw can significantly increase stiffness and strength of spinal fixation. Some major complications have also been reported. However, there are no reports discussing cement distribution and its morphology in the osteoporotic vertebral body, which is critical in the analysis of the biomechanical strength of the pedicle screw and the risk of cement leakage after pedicle screw augmentation. In this study, we used computed tomography (CT) to evaluate the cement distribution in the osteoporotic vertebral body after PMMA augmentation of a pedicle screw and to analyze the factors leading to cement leakage. Two groups of patients were studied. Group A consisted 25 osteoporotic patients (mean age of 73 years) with spinal instrumentation who had a total of 145 pedicle screws and cement augmentation with biopsy needles. Group B consisted of 23 osteoporotic patients (mean age of 74.6 years) with spinal instrumentation who had a total of 125 cannulated pedicle screws with cement augmentation. All patients had CT evaluation of the cement distribution in the vertebral body after the surgery. The cement distribution in the vertebrae was divided into four zones in the axial CT view: anterior one-third, middle third, and posterior third of vertebral body, and the pedicle. The morphology of the cement distribution around the pedicle screw was defined as scattered type or concentrate type. The leakage pattern was divided to anterior–lateral, posterior–lateral, and canal leakage. The correlations among bone mineral density (BMD), the cement leakage rate, and cement distribution morphology were also analyzed. The results showed that most augmented pedicle screws had cement extension into three of the four zones of the vertebral body (66.3%), followed by two zones (20%), all four zones (11.5%), and only one zone (2.2%). Overall, 123 screws (84.8%) in Group A and 108 screws (86.4%) in Group B had cement concentrate type distribution. The cement leakage rate in Group A is 18.3% and 13.6% in Group B. Patients with a BMD <0.6 g/cm² had significantly higher rates of cement leakage and tended toward a scattered cement distribution. There was only one patient who had a symptomatic leakage (sciatica) in Group B. We concluded that the cement distribution after pedicle screw augmentation with biopsy needle or cannulated screw technique was mostly localized in three zones of the vertebral body, and patients with lower BMD had a higher risk of cement leakage and scattered cement distribution.     

Suppression of puerarin on polymethylmethacrylate-induced lesion of peri-implant by inhibiting NF-κB activation in vitro and in vivo

Puerarin (PR), a natural isoflavone isolated from Chinese traditional plant pueraria lobata, has attracted considerable attention due to its important biological and pharmacological activities. However, its effects on lesion of peri-implant and related mechanism of action are still not clear, which require further investigation. In this study, we evaluated the effects of PR on polymethylmethacrylate (PMMA)-induced lesion of peri-implant in vitro and in vivo, and explored its possible mechanism of action. Our results indicated that PR could inhibit PMMA-induced osteoclastogenesis in RAW264.7 cells with a dose-dependent manner in vitro and effectively down-regulate mRNA and protein expressions of matrix metalloprotein 9 (MMP-9), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and receptor activator of nuclear factor (NF)-κB (RANK), primarily via the suppression of NF-κB signaling. Furthermore, we found that PMMA induction could directly cause the phosphorylation of IκB and significantly promote the nuclear translocation of p65 in RAW264.7 cells. In other words, PR was able to dose-dependently attenuate the PMMA-induced nuclear translocation of p65 in RAW264.7 cells. In vivo, PR was observed to attenuate PMMA-induced osteoclastogenesis, osteolysis, mRNA expressions of receptor activator of nuclear factor (NF)-κB ligand (RANKL) and RANK, as well as protein levels of MMP-9, TNF-α, IL-6, and p65 in a murine calvarial osteolysis model. These findings suggested that PR might be a potential therapeutic drug to lesion of peri-implant, and provided new insights for understanding its possible mechanism.     

两种不同复合唑来膦酸骨水泥的体外浸提对比实验研究

目的对比观察不同唑来膦酸含量的两种骨水泥在体外的药物释放情况,为临床应用其治疗骨巨细胞瘤奠定体外药物释放动力学基础。方法将唑来膦酸分别与聚甲基丙烯酸甲酯骨水泥及磷酸钙骨水泥以0.2%、0.4%、0.6%的质量比混合制备复合唑来膦酸骨水泥的测试标本,并同时设立空白对照,所制两种不同骨水泥标本均分成a(空白对照)、b(含0.2%的唑来膦酸)、c(含0.4%的唑来膦酸)、d(含0.6%的唑来膦酸)4组,每组1个标本。将4组标本分别放于5m L生理盐水中,并最终置于智能溶出仪中持续浸提42天,于特定时间点取样待测,用高效液相色谱仪测定浸提液中唑来膦酸的浓度,计算各时点的药物释放浓度和释放总量百分比,并绘制相应曲线。结果复合唑来膦酸聚甲基丙烯酸甲酯骨水泥的各实验组浸提液色谱图中未发现唑来膦酸吸收峰的出现,而复合唑来膦酸磷酸钙骨水泥的各实验组浸提液色谱图中均可见唑来膦酸吸收峰的出现且各实验组在第42天实验结束时的唑来膦酸累计溶出量百分比:b组d组c组。结论唑来膦酸不能从聚甲基丙烯酸甲酯骨水泥中释放,但可以从磷酸钙骨水泥中释放并最终可以以一稳定药物浓度缓慢、持久释放。