Effects of fat admixture on the strengths of conventional and low-viscosity bone cements

The diametral tensile and compressive strengths of both conventional doughy and low-viscosity (LVC) bone cements were tested with sequential admixtures of up to 50% (by weight) liquified fat. The addition of as little as 5% (by weight) fat caused a significant reduction (p = 0.05) in the strengths of both cements. The LVC appeared to be affected to a greater degree by fat contaminations than did the conventional cement, although the strengths of the LVC were generally equal to or higher than those of the conventional cement. The enhanced effect of fat contamination on the LVC was thought to be due to the more fluid, tacky nature of this material during administration.     

髋关节置换术用丙烯酸骨水泥性能评价的关注点

经查阅髋关节置换术用丙烯酸骨水泥的相关文献、相关技术标准、产品指导原则等,认为对骨水泥的评价主要涉及骨水泥的单体残留、凝固行为、机械性能和生物相容性等产品性能。生产企业应加强骨水泥产品的基础研究能力,制定科学的技术指标和试验方法,以确保产品的安全有效性,同时也可为注册申报提供充分的支持性数据。     

骨水泥的真空搅拌实验研究

目的 :比较骨水泥经过真空搅拌和普通搅拌的机械性能变化。方法 :将一种国产骨水泥分成普通搅拌和真空搅拌 2组分别制成标本 ,按照国际标准组织 (ISO)的标准测定抗静态压力强度 ,静态抗弯曲强度和弹性模量 ,按照德国工业标准 (DIN)检测抗疲劳强度。结果 :应用真空搅拌处理 ,抗弯曲强度和抗疲劳强度分别提高了 13 %和 15 % ,骨水泥的静态压力耐受强度稍降低 ,弹性模量稍提高 ,二者在统计学上无变化。结论 :采用真空搅拌骨水泥的方法 ,提高了国产骨水泥的抗疲劳强度及静态抗弯曲强度 ,在临床应用有较大的积极意义。     

Radiopacity and fatigue characterization of a novel acrylic bone cement with sodium fluoride

Acrylic bone cement must provide good radiographic visibility and good long-term mechanical resistance in joint replacements. A new formulation of cement with 6% barium sulfate and 6% sodium fluoride was developed (Fluoride Bone Cement). Barium sulfate is a necessary addition to allow radiographic visibility although it reduces the mechanical strength of the material. Sodium fluoride promotes bone formation. However, its effect on the mechanical behavior is currently unknown while its influence on radiopacity can only be roughly estimated. The aim of this investigation was to establish if the new formulation would be suitable for clinical trials. In this respect, a mechanical (fatigue test) and radiographic (optical density measurements on x-ray films) characterization was performed on a typical commercially available cement with barium sulfate added and on the Fluoride Bone Cement. It was demonstrated that the fluoride cement has a (marginally) superior fatigue strength and comparable radiopacity to commercial radiopaque cements.     

多孔磷酸钙人工骨与重组人骨形成蛋白2复合修复骨缺损的实验研究

目的研究多孔磷酸钙人工骨（porous calcium phosphate cement，PCPC）与重组人骨形成蛋白2（recombinant human bone morphogenetic protein2，rhBMP-2）复合后体外的缓释作用及其对兔骨缺损的修复作用。方法采用物理吸附法将rhBMP-2（0．4mg）溶液吸附至PCPC中，制备成PCPC／rhBMP-2复合材料。冻干后，扫描电镜观察复合材料内部形态。以包覆壳聚糖的PCPC／rhBMP-2为实验组，单纯PCPC／rhBMP-2为对照组，测试在模拟体液中的rhBMP-2缓释行为。取新西兰大白兔12只，股骨远端制成直径4．2mm，深5．0mm的骨缺损模型。将包覆壳聚糖的PCPC／rhBMP-2复合材料修复骨缺损作为实验组，以植入单纯PCPC作为对照组。术后观察动物一般情况，于4周和8周取材行X线片和组织学观察。结果扫描电镜显示PCPC／rhBMP-2复合材料孔隙中吸附了大量的rhBMP-2。rhBMP-2体外缓释：对照组rhBMP-2于150h基本全部释放；实验组rhBMP-2于350h缓释量约达99％，较对照组慢。动物实验：动物术后切口无感染，于4周行动自如。X线片示术后4周对照组骨缺损区材料清晰，实验组骨缺损区密度大部分接近宿主骨，材料模糊；8周对照组材料边缘较术后4周模糊，实验组骨缺损区密度已基本接近宿主骨。组织学观察，术后4周对照组可见少量成骨细胞和破骨细胞，实验组可见成熟骨组织和骨髓腔，新生骨逐渐取代材料；8周对照组可见大量成骨细胞和破骨细胞，少量新生骨并向材料内长入，实验组可见成熟骨小梁和骨髓组织。结论PCPC是rhBMP-2较理想的载体材料，复合后具有良好的诱导成骨作用，可作为一种新型复合人工骨修复骨缺损，具有良好的临床应用前景。     

利奈唑胺骨水泥在关节置换术后感染治疗中应用的系列探索研究之一——利奈唑胺骨水泥的物理、力学性能研究

目的：探讨利奈唑胺骨水泥物理和力学性能改变,以指导利奈唑胺骨水泥在治疗人工关节置换术后感染中的临床应用。方法根据在40 g骨水泥中加入不同剂量的利奈唑胺,将样本共分成8个组,每组测定5个样本,8组分别是：Ⅰ组为对照组,不加抗生素,第Ⅱ到第Ⅷ组加入抗生素的量分别为1.2、2.4、3.6、4.8、6.0、7.2及8.4g。分别测定各组面团期时间、压缩强度、弯曲模量和弯曲强度。结果各组面团时间在2′50″～3′40″之间。随着抗生素剂量的增加,面团时间也随之增加。各组的压缩强度、弯曲模量和弯曲强度均优于ISO 5833标准,且有统计学差异（ P＜0.05）,Ⅱ组的压缩强度、弯曲模量和弯曲强度与对照组没有统计学差异,但高于其他各组,与其他各组间有统计学差异。而第Ⅷ组的压缩强度、弯曲模量和弯曲强度均低于其他各组,且有统计学差异。结论面团时间随着利奈唑胺剂量的增加而增加。如果利奈唑胺骨水泥用于预防性使用,则每40 g骨水泥中最多可以加入1.2g利奈唑胺,否则会影响骨水泥的强度。如果利奈唑胺骨水泥用于制作占位器,在每40 g骨水泥中最多不要加入超过7.2 g的利奈唑胺,不至于太影响骨水泥占位器的强度,但是加入的最佳剂量是多少,本系列实验的另一部分会有详细交代。     

Bioactivity of Ceftazidime and Fluconazole Included in Polymethyl Methacrylate Bone Cement for Use in Arthroplasty

Background

The microorganisms that most frequently cause prosthetic joint infection are methicillin-resistant Staphylococcus aureus and gram-negative aerobic bacillus. Studies have documented the efficacy of mixing antibiotics with polymethyl methacrylate, but that of antifungal drugs has not received much attention. The objective of this in vitro study was to characterize the elution profile and bioactivity of ceftazidime and fluconazole when incorporated into bone cement in proportions intended for prophylaxis and treatment of bone infections.

Cortical bone mass,composition, and mechanical properties in female rats in relation to age,long-term ovariectomy,and estrogen substitution

Summary The study comprised 12 groups of female rats: 6 groups of intact rats killed at 2, 6, 9, 12, 15, and 24 months of age, 4 groups of rats ovariectomized at 6 months and killed together with the intact rats at 9, 12, 15, and 24 months of age, and 2 groups of rats (one intact and one ovariectomized) treated with estrogen (2 g estradiol valerate/rat/week s.c.) for 8 months before they were killed at 24 months of age. The composition, dimensions, and mechanical strength of intact bone and bone collagen from femoral diaphyses were investigated in relation to age, ovariectomy, and estrogen administration. Up to 6–9 months of age, the axial length, percentage ash, density, and compressive mechanical stress increased, whereas percentage collagen decreased. An age-related increase in bone mass, crosssectional area, and wall thickness and a decrease in mechanical quality of bone collagen were apparent from 2 to 24 months of age. An age-related periosteal bone formation and the absence of endosteal bone resorption were demonstrated in intact rats. Compared with intact rats, ovariectomy was followed by an increase in body weight, a tendency to reduced percentage ash and a depressed bone mass, crosssectional area, and wall thickness of femoral diaphyses. The compressive mechanical stress of intact bone and the mechanical quality of bone collagen were unaffected by ovariectomy. Ovariectomy did not influence the periosteal bone formation but induced an endosteal bone resorption not present in the intact rats. The estrogen treatment of the ovariectomized rats normalized the body weight of the rats and brought to an end the endosteal bone resorption induced by ovariectomy. Estrogen treatment of both ovariectomized and intact rats tended to reduced the rate of periosteal bone formation.     

Characterization of Bone Cements

Thirty-seven patients with fractures of the thoracic and lumbar spine treated with Harrington instrumentation were reviewed. Twenty-seven patients with a follow-up time of more than 2 years were summoned for a clinical and radiographic examination. This report presents the results related to reduction, stabilization, return of neural function, spinal posture and mobility, and residual disability. It is concluded that Harrington instrumentation can be performed without a substantial number of complications. Its major advantages are early mobilization and ambulation. The operative technique is discussed with special reference to the preservation of the normal configuration of the back. The value of computerized tomography in the preoperative assessment is stressed.     

Long-term effect of orchidectomy on cortical bone from rat femur: Bone mass and mechanical properties

Summary The study comprised seven groups of intact rats killed at 9, 12, 15, and 24 months of age, and three groups of rats castrated at the age of 9 months and killed together with the intact rats 3, 6, and 15 months after castration. The composition, dimension, and mechanical properties of intact bone as well as the constituent bone collagen from femoral diaphyses were investigated in relation to both age (9–24 months) and castration. Castration had no effect on density and only minor effect on ash and collagen contents. An age-related increase in bone mass, cross-sectional area, and wall thickness of the diaphyses was arrested (bone mass, area) or even reversed (to a decrease in wall thickness) after castration. Therefore, a growing difference, pronounced from 6 months after castration, between intact and castrated rats was observed in bone mass, cross-sectional area, and wall thickness. The compressive mechanical strength of intact bone normalized with regard to cross-sectional area was unaffected by castration, whereas castration tended to increase the stiffness of the bone collagen. When observed in a polarization microscope, two different zones in cross sections of the diaphyses were apparent. The average diameter of the border line separating the two zones was independent of age and castration. By measuring the average thickness of each of the two zones, age-related periosteal bone formation and endosteal bone resorption were demonstrated. After castration, the rate of bone formation was reduced and the rate of bone resorption was accelerated. Castration was thus found to affect the composition and the quality of the cortical bone to a minor extent only. On the other hand, the quantity of cortical bone was markedly reduced from 6 months after castration due to both an inhibited rate of bone formation and an accelerated rate of bone resorption.     

携载rhBMP-2微球的新型复合人工骨的释药及成骨活性研究

目的 制备一种具有良好降解性和成骨活性，可注射的自凝固新型骨修复材料。方法制备携载rhBMP-2的聚乳酸与聚乙醇酸共聚物（PLGA）微球，并将其与rhBMP-2／磷酸钙骨水泥（CPC）复合。制备出rhBMP-2／PLGA微球／CPC复合人工骨。测定了复合材料释药速度，将复合材料及rhBMP-2-CPC分别植入兔双侧股骨髁骨缺损区域，通过X线、组织学观察比较不同时期材料的降解及成骨情况。结果 复合材料各时间点的体外释药量均大于单纯rhBMP-2／CPC组．与单纯rhBMP-2／CPC材料相比较，复合材料植入体内后不同时间点材料的降解和新骨生成均高于单纯rhBMP-2／CPC植入组。结论 rhBMP-2／PLGA微球的掺入可明显加快rhBMP-2的释放。提高材料的降解速度和成骨活性。     

Estimation of mechanical properties of cortical bone by computed tomography

It is difficult to assess from conventional x-rays the amount of loading that a bone can tolerate. The question therefore was asked whether the mechanical properties of cortical bone could be estimated by using a computed tomography (CT) system typically employed in the clinical setting. In vitro cross sectional diaphyseal scans of adult human tibiae were made using a GE 9800 scanner and linear attenuation coefficients determined in several regions of the central cross sections. Samples from the mid-diaphyses of these tibiae were harvested, tested in three-point bending to failure, and mechanical properties as well as density and ash fraction determined. The respective relationships between CT measurements, mechanical properties, and physical properties were calculated using regression analysis. In addition, a solid calibration phantom (tricalciumphosphate) was scanned to evaluate the variability of CT measurements. The physical parameters measured in this study were found to be comparable with data from other authors but correlations were moderate to weak. Linear regression revealed the following correlation coefficients with CT data: r = 0.55 (Young's modulus), r = 0.50 (strength), r = 0.65 (apparent density) and r = 0.46 (ash fraction). The correlation coefficients of these regressions for both linear and power fits were not significantly different. A high linear correlation (r = 0.99) was found between the chamber densities and the measured attenuation coefficients, but accuracy varied between 2 and 6%. The small range of specimen mechanical properties as well as the limitations inherent with the methods employed may explain these results. We conclude that clinical equipment as used in this study is not sufficient to accurately estimate the mechanical properties of cortical bone.     

Biological and biomechanical effects of vancomycin and meropenem in acrylic bone cement

Antibiotic-loaded bone cement is extensively used in joint arthroplasty, but increasing bacteria resistance against common antibiotics has lead to a demand for alternative drugs. However, bone cement containing new additives must be characterized both biologically and mechanically. This study evaluated elution kinetics, antibacterial activity, and mechanical properties for cement loaded with vancomycin and/or meropenem. The presence of meropenem broadened the antibacterial spectrum and enhanced the elution of vancomycin. The mechanical properties were negatively affected by 1.0 g of vancomycin, but these detrimental effects were acceptable when only 0.5 g of vancomycin were added to a cement containing 0.5 g of meropenem. Further investigations on this formulation with adjusted antibiotic amounts are, however, necessary to reach the optimal compromise between the antibacterial and the mechanical properties of the bone cement.     

Improved quality of life after intramedullary nailing in femoral metastases

Bone metastases are one of the most frequent problems in orthopaedic oncology. Impending fractures require surgical treatment in order to control pain and mechanical disrupture of the bone involved. The femur is the long bone most commonly involved by metastatic carcinoma. Preventive osteosynthesis is considered a good solution in the treatment of femoral metastases, reducing local pain and improving the quality of life. We analyzed clinical and radiographical outcomes of 21 patients with femoral metastases treated with intramedullar nailing at the Orthopaedics Department of Catholic University of Rome from 1997 to 2000. Bone metastases were located in the diaphysis or in the metadiaphysis. The primary tumors were lung in 10 cases, breast in 8 cases and kidney in 3 cases. Proximal or distal localizations constituted the indication for locked nailing. The implants used were: Küntscher nail in 8 cases, Russel-Taylor nail in 8, Recon nail in 2 cases and proximal femoral nailing in 3 cases when osteolysis involved also the femoral neck. Partial weight-bearing with external support was allowed 3 days postoperatively; full-weight bearing was allowed 20 days after operation except in the cases in which a progression of the primary tumor was observed. No infection or pulmonary embolism was observed. Adjuvant chemotherapy or local radiotherapy was used in all cases. Survival rate was related to the type of primary tumor, and varied from 3 months to 2 years. Received: 18 September 2001/Accepted: 3 November 2001     

全髋置换术扩髓及骨水泥灌注对血液动力学的影响及其机制

目的：观察全髋置换术中扩髓及骨水泥灌注对血液动力学的影响并探讨其机制。方法：选择在硬膜外联合全身麻醉下行全髋置换术成年患进18例,记录扩髓前,扩髓即刻,髓腔冲洗,骨水泥灌注即刻,灌注后3、5、10分钟时动脉压（SBP、DBP）、中心静脉压（CVP）;用食道超声多普勒监测以上时点心排血量（CO）、每搏量（SV）、血流加速度（ACC）、峰流速（PV）、体循环阻力（TSVR）、左心室射血时间指数（LVETI）以及各时血血气参数。结果：（1）骨水泥灌注即刻,灌注后3、5分钟SBP、DBP显著下降（P＜0．01）;扩髓即刻,髓腔冲洗,骨水泥灌注后3、5、10分钟时CVP均显著增加（P＜0．01）,骨水泥灌注即刻CVP明显下降（P＜0．01）;（2）骨水泥灌注即刻,灌注后3、5分钟、CO、SV、ACC、PV显著下降（P＜0．01）,LVETI明显延长,TSVR在骨水泥灌注即刻,灌注后3分钟也明显下降（P＜0．01）;（3）髓腔冲洗、骨水泥灌注即刻PaO2显著下降（P值分别小于0．1和0．05）;PaCO2均在正常生理范围内,但在髓腔冲洗时有明显增加（P＜0．01）。结论：全髋置换术扩髓可引起不程度的脂肪栓塞,骨水泥灌注时骨水泥具有短暂直接扩张血管和较持久的抑制心肌收缩功能作用。