Sterilization of bone allografts by microwave and gamma radiation

Abstract

Purpose: Bone allografts are used to enhance healing in osteotomies, arthrodesis, fractures and to replace bone loss resulting from tumour or trauma. However, a major concern associated with the bone allografts is the potential for disease transmission. Various sterilization techniques have been developed to prevent infection through allografts. This study was undertaken with the aim of exploring the use of microwave radiation for sterilization of bone allografts and to compare with gamma radiation sterilization.

Materials and methods: Bone allografts were processed from femoral heads obtained from living donors. The effect of microwave and gamma radiation on the bacteria isolated from bone allograft was evaluated. The microwave radiation treatment was performed at 2450 MHz (frequency) for varying lengths of time at maximum power 900 Watts (W). Viability of three Gram-positive bacteria – Bacillus subtilis, Corynebacterium, Staphylococcus aureus and three Gram-negative bacteria – Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa was examined after irradiation of bacterial suspensions and contaminated processed bone allografts. The sterility test of microwave and gamma irradiated bone allograft was carried out in accordance with ISO (International Organization for Standardization) 11737-2.

Results: Microwave irradiation (2450 MHz and 900 W) of bacterial isolates resulted in complete inactivation within 60 seconds. The contaminated bone samples showed no growth of organisms after 2 minutes of exposure to microwave irradiation. No viable counts were detected in bone grafts inoculated with Gram-negative bacterial species on gamma irradiation to a dose of 15 kGy. Bones contaminated with Gram-positive bacteria required a higher dose of 20 kGy for complete inactivation.

Conclusions: The study shows that sterilization of contaminated femoral head bone allografts can be achieved by short exposure of 2 min to 2450 MHz and 900 W microwave radiation.     

Fractionation of high-dose electron beam irradiation of BPTB grafts provides significantly improved viscoelastic and structural properties compared to standard gamma irradiation

Purpose

Irradiation >30 kGy is required to achieve sterility against bacterial and viral pathogens in ACL allograft sterilization. However, doses >20 kGy substantially reduce the structural properties of soft-tissue grafts. Fractionation of irradiation doses is a standard procedure in oncology to reduce tissue damage but has not been applied in tissue graft sterilization.

Methods

Forty-four human 10-mm wide bone-patellar-tendon-bone grafts were randomized into four groups of sterilization with (1) 34 kGy of ebeam (2) 34 kGy gamma (3) 34 kGy fractionated ebeam, and (4) non sterilized controls. Graft´s biomechanical properties were evaluated at time zero. Biomechanical properties were analyzed during cyclic and load-to-failure testing.

Results

Fractionation of ebeam irradiation resulted in significantly higher failure loads (1,327 ± 305) than with one-time ebeam irradiation (1,024 ± 204; P = 0.008). Compared to gamma irradiation, significantly lower strain (2.9 ± 1.5 vs. 4.6 ± 2.0; P = 0.008) and smaller cyclic elongation response (0.3 ± 0.2 vs. 0.6 ± 0.4; P = 0.05), as well as higher failure loads (1,327 ± 305 vs. 827 ± 209; P = 0.001), were found. Compared to non-irradiated BPTB grafts, no significant differences were found for any of the biomechanical parameters. Non-irradiated controls had significantly lower cyclic elongation response and higher failure loads than ebeam and gamma irradiation.

Conclusions

In this study, it was found that fractionation of high-dose electron beam irradiation facilitated a significant improvement of viscoelastic and structural properties of BPTB grafts compared to ebeam and gamma irradiation alone, while maintaining levels of non-irradiated controls. Therefore, this technique might pose an important alternative to common methods for sterilization of soft-tissue allografts.     

Radiation sterilization of tissue allografts:A review

Tissue substitutes are required in a number of clinical conditions for treatment of injured and diseased tissues.Tissues like bone,skin,amniotic membrane and soft tissues obtained from human donor can be used for repair or reconstruction of the injured part of the body.Allograft tissues from human donor provide an excellent alternative to autografts.However,major concern with the use of allografts is the risk of infectious disease transmission.Therefore,tissue allografts should be sterilized to make them safe for clinical use.Gamma radiation has several advantages and is the most suitable method for sterilization of biological tissues.This review summarizes the use of gamma irradiation technology as an effective method for sterilization of biological tissues and ensuring safety of tissue allografts.     

Proliferation and cytogenetic studies in human blood lymphocytes exposed in vitro to 2450 MHz radiofrequency radiation

Abstract. Aliquots of human peripheral blood collected from two healthy human volunteers were exposed in vitro to continuous wave 2450 MHz radiofrequency radiation (RFR), either continuously for a period of 90 min or intermittently for a total exposure period of 90 min (30 min on and 30 min off, repeated three times). Blood aliquots which were sham-exposed or exposed in vitro to 150 cGy gamma radiation served as controls. The continuous wave 2450 MHz RFR was generated with a net forward power of 34.5 W and transmitted from a standard gain rectangular antenna horn in a vertically downward direction. The mean power density at the position of the cells was 5.0 mW/cm 2. The mean specific absorption rate calculated by Finite Difference Time Domain analysis was 12.46 W/kg. Immediately after exposure, lymphocytes were cultured for 48 and 72 h to determine the incidence of chromosomal aberrations and micronuclei, respectively. Proliferation indices were also recorded. There were no significant differences between RFR-exposed and shamexposed lymphocytes with respect to; (a) mitotic indices; (b) incidence of cells showing chromosome damage; (c) exchange aberrations; (d) acentric fragments; (e) binucleate lymphocytes, and (f) micronuclei, for either the continuous or intermittent RFR exposures. In contrast, the response of positive control cells exposed to 150 cGy gamma radiation was significantly different from RFR-exposed and sham-exposed lymphocytes. Thus, there is no evidence for an effect on mitogen-stimulated proliferation kinetics or for excess genotoxicity within 72 h in human blood lymphocytes exposed in vitro to 2450 MHz RFR.     

Allograft transplantation in the knee: tissue regulation,procurement, processing,and sterilization

Use of musculoskeletal allografts has become increasingly popular, with widespread use among knee surgeons. The advantages and disadvantages of their use have been documented. In the knee, allografts are used for ligament reconstruction, meniscal transplantation, and articular surface reconstruction. The purpose of this review is to present issues surrounding the allograft industry, including regulation of tissues and tissue banks and procurement, processing, sterilization, and storage of allograft tissue. Tissue bank regulation is ultimately under the jurisdiction and authority of the Food and Drug Administration; some individual states regulate tissue banks. The American Association of Tissue Banks is a scientific organization that encourages education, research, and voluntary accreditation of tissue banks. It promotes safety and standards for retrieval, processing, storage, and distribution of transplantable human tissue. Allograft tissues are generally harvested and processed aseptically, which may not prevent contamination. Tissue sterilization is difficult and controversial. Tissue banks historically have used one of two methods of sterilization, ethylene oxide or gamma radiation. Both methods have risks and benefits. Newer methods of sterilization are being developed. Allograft tissue that is not transplanted fresh can be freeze-dried or deep frozen for storage. Ultimately, allograft transplantation in the knee facilitates knee form and function and enhances the patient's quality of life. Orthopaedic surgeons who use allograft tissue must understand the tissue banking process to provide safe and effective tissues to their patients.     

Anterior cruciate ligament reconstruction using cryopreserved irradiated bone-ACL-bone-allograft transplants

Bone-ACL-bone allograft transplantation has been investigated as a potential solution to reconstruction of the anterior cruciate ligament (ACL). To minimize disease transmission (e.g. the acquired immuno deficiency syndrome), bony and collagenous tissues should be sterilized. Recent animal studies indicate that gamma irradiation and ethylene oxide sterilization result in diminished histological and biomechanical properties. The purpose of the present study was biomechanical and histological determination of the fate of deep-frozen gamma-irradiated (2.5 Mrad) canine bone-ACL-bone allografts witb argon gas protection. Particular attention was paid to collagenous and neuroanatomical morphology 3,6 and 12 months after implantation, by comparison to a non-irradiated control group. Sixty skeletally mature foxhounds were operated on in this study, divided up in two groups of 30 dogs each. In group A animals the ACL was replaced by a deep-frozen (–80°C) bone-ACL-bone LAD-augmented allograft subjected to 2.5 Mrad gamma irradiation with argon gas protection. The animals in group B received an LAD-augmented ACL-allograft transplant without gamma irradiation. All knees from both groups were evaluated 3, 6 and 12 months after implantation in regard to biomechanical properties, collagen morphology and routine histology (haematoxylin and eosin stain, polarization microscopy), neuroanatomical morphology (silver and gold chloride stain) and microvasculature (modified Spalteholz technique). The irradiated ACL allografts withstood a maximum load that was 63.8% (718.3N) of the maximum load of normal ACLs after 12 months. By contrast, the non-irradiated allografts failed at 69.1% (780.1 N) of the maximum load of normal control ACLs. The allografts appeared to be developing well-orientated collagen fibres as demonstrated by polarized light microscopy and haematoxylin-eosin staining. Silver stain technique was additionally employed to demonstrate the presence of Golgilike mechanoreceptors and free nerve endings within the allografts. As in the normal ACL, these neurogenic structures were most commonly found near the surface of the allografts and at the two bony attachments. Modified Spalteholtz microangiographic technique demonstrated similar vascularity to normal ACL in the non-irradiated allograft group after 12 months, compared to slight hypervascularization in the irradiated groups. This study showed that irradiated ACL allografts have the potential to attain the main biomechanical and histological properties of the normal ACL.     

Micronuclei in the peripheral blood and bone marrow cells of rats exposed to 2450 MHz radiofrequency radiation.

PURPOSE: To determine the incidence of micronuclei in peripheral blood and bone marrow cells of rats exposed continuously for 24h to 2450 MHz continuous wave radiofrequency radiation (RFR) at an average whole-body specific absorption rate (SAR) of 12W/kg. MATERIALS AND METHODS: Eight adult male Sprague-Dawley rats were exposed to 2450 MHz RFR in circularly polarized waveguides. Eight sham-exposed rats were kept in similar waveguides without the transmission of RFR. Four rats were treated with mitomycin-C (MMC) and used as positive controls. All rats were necropsied 24h after the end of RFR and sham exposures, and after the 24h treatment with MMC. Peripheral blood and bone marrow smears were examined to determine the frequency of micronuclei (MN) in polychromatic erythrocytes (PCE). RESULTS: The results indicated that the incidence of MN/2000 PCE were not significantly different between RFR- and sham-exposed rats. The group mean frequencies of MN in the peripheral blood were 2.3+/-0.7 in RFR-exposed rats and 2.1+/-0.6 in sham-exposed rats. In bone marrow cells, the average MN incidence was 3.8+/-1.0 in RFR-exposed rats and 3.4+/-0.7 in sham-exposed rats. The corresponding values in positive control rats treated with MMC were 23.5+/-4.7 in the peripheral blood and 33.8+/-7.4 in bone marrow cells. CONCLUSION: There was no evidence for the induction of MN in peripheral blood and bone marrow cells of rats exposed for 24h to 2450 MHz continuous wave RFR at a whole body average SAR of 12 W/kg.     

Micronuclei in the peripheral blood and bone marrow cells of rats exposed to 2450 MHz radiofrequency radiation

Purpose : To determine the incidence of micronuclei in peripheral blood and bone marrow cells of rats exposed continuously for 24h to 2450 MHz continuous wave radiofrequency radiation (RFR) at an average whole-body specific absorption rate (SAR) of 12W/kg. Materials and methods : Eight adult male Sprague-Dawley rats were exposed to 2450 MHz RFR in circularly polarized waveguides. Eight sham-exposed rats were kept in similar waveguides without the transmission of RFR. Four rats were treated with mitomycin-C (MMC) and used as positive controls. All rats were necropsied 24h after the end of RFR and sham exposures, and after the 24h treatment with MMC. Peripheral blood and bone marrow smears were examined to determine the frequency of micronuclei (MN) in polychromatic erythrocytes (PCE). Results : The results indicated that the incidence of MN/2000 PCE were not significantly different between RFR- and sham-exposed rats. The group mean frequencies of MN in the peripheral blood were 2.3 ±0.7 in RFR-exposed rats and 2.1 ±0.6 in sham-exposed rats. In bone marrow cells, the average MN incidence was 3.8 ±1.0 in RFR-exposed rats and 3.4 ±0.7 in sham-exposed rats. The corresponding values in positive control rats treated with MMC were 23.5 ±4.7 in the peripheral blood and 33.8 ±7.4 in bone marrow cells. Conclusion : There was no evidence for the induction of MN in peripheral blood and bone marrow cells of rats exposed for 24h to 2450 MHz continuous wave RFR at a whole body average SAR of 12 W/kg.     

The effect of gamma irradiation on anterior cruciate ligament allograft biomechanical and biochemical properties in the caprine model at time zero and at 6 months after surgery

BACKGROUND: High levels of gamma irradiation are required to eliminate the risk of bacterial and viral transmission during implantation of musculoskeletal allografts. The effects of high levels of gamma irradiation on anterior cruciate ligament allograft biomechanics are still not known. HYPOTHESIS: High-dose gamma irradiation (4 Mrad) adversely affects anterior cruciate ligament allograft biomechanics at surgery and at 6 months after surgery and affects biochemistry at 6 months. STUDY DESIGN: Controlled laboratory study. METHODS: Bilateral anterior cruciate ligament reconstructions were performed in 18 adult goats, with one knee receiving an irradiated patellar tendon allograft (4 Mrad) and the other receiving a frozen control allograft (0 Mrad). In 6 recipients (time zero group), graft pairs were tested immediately after sacrifice, and load relaxation of the femur-allograft-tibia preparation was measured during cyclic anterior displacement. Twelve recipients received bilateral anterior cruciate ligament reconstructions, staged 2 months apart, and were sacrificed a mean of 6 months postoperatively. Load relaxation and tensile failure testing were performed, followed by allograft biochemistry assessment. RESULTS: At time zero, irradiated grafts showed less load relaxation than did contralateral controls, but by 6 months, the trend had reversed because of decreases in control graft relaxation, with no changes in irradiated graft relaxation. By 6 months, irradiated grafts showed lower stiffness and maximum force compared to controls but no differences in modulus, maximum stress, or biochemistry. CONCLUSION: High levels of gamma irradiation affect anterior cruciate ligament allograft subfailure viscoelastic and structural properties but not material or biochemical properties over time. CLINICAL RELEVANCE: Although high levels of gamma irradiation may inactivate infectious agents, this treatment is not a feasible clinical option because of altered allograft biomechanics.     

Measurement of DNA damage after acute exposure to pulsed-wave 2450 MHz microwaves in rat brain cells by two alkaline comet assay methods

PURPOSE: To investigate the effect of 2450 MHz pulsed-wave microwaves on the induction of DNA damage in brain cells of exposed rats and to discover whether proteinase K is needed to detect DNA damage in the brain cells of rats exposed to 2450 MHz microwaves. MATERIALS AND METHODS: Sprague-Dawley rats were exposed to 2450 MHz pulsed-wave microwaves and sacrificed 4 h after a 2-h exposure. Rats irradiated whole-body with 1 Gy (137)Cs were included as positive controls. DNA damage was assayed by two variants of the alkaline comet assay on separate aliquots of the same cell preparation. RESULTS: Significant DNA damage was observed in the rat brain cells of rats exposed to gamma-rays using both versions of the alkaline comet assay independent of the presence or absence of proteinase K. However, neither version of the assay could detect any difference in comet length and/or normalized comet moment between sham- and 2450 MHz pulsed-wave microwave-exposed rats, regardless of the inclusion or omission of proteinase K in the comet assay. CONCLUSIONS: No DNA damage in brain cells was detected following exposure of rats to 2450 MHz microwaves pulsed-wave at a specific absorption rate of 1.2 W kg(-1) regardless of whether or not proteinase K was included in the assay. Thus, the results support the conclusion that low-level 2450 MHz pulsed-wave microwave exposures do not induce DNA damage detectable by the alkaline comet assay.     

Decontamination of gum arabic with gamma-rays or electron beams and effects of these treatments on the material.

Samples of gum arabic were irradiated to 2.5, 5.0 and 10.0 kGy with gamma-rays and electrons for a comparison of the relative effectiveness of these two treatments and for investigation of the effects of these doses of radiation on the material. The initial raw samples were contaminated with various strains of bacteria, including fungi and spore-forming bacteria (such as Enteroccus faecalis, Bacillus cereus and Closstridum perfringens). The samples were completely decontaminated by irradiation to 10.0 kGy with either gamma-rays or electrons. Slight changes in the physical properties of the material, such as darkening and viscosity decrease, were noticeable after irradiation to the highest dose, but not to the lower doses. A linear relationship between the absorbed dose and the material degradation was observed. gamma-rays were found to be more destructive than electrons. An optimal decontamination regimen for the material to be used in food industry and medicine would be irradiation to 5 kGy with electrons. It would be a safe alternative to the methods using hazardous chemicals, such as pesticides and fungicides. It would provide sufficient decontamination without adverse effects on the physical properties of the final products.     

A biomechanical analysis of solvent-dehydrated and freeze-dried human fascia lata allografts. A preliminary report.

This study compares the basic mechanical properties of two groups of commercially available fascia lata allografts processed by different means (solvent-dehydrated and sterilized via gamma radiation, and freeze-dried without secondary sterilization). The results reveal significantly (P less than 0.05) higher stiffness, higher maximum load to failure, and higher maximum load per unit width of graft with the solvent-dried as opposed to the freeze-dried fascia lata. Subsections of individual solvent-dried specimens were also more uniform in their mechanical properties than those of the freeze-dried allografts. Clinical relevance: Fascia lata is used as a graft material in a variety of orthopaedic procedures. Allograft fascia lata offers an increased cross-sectional area of material and eliminates the morbidity associated with the harvesting of autologous tissues. However, the structural uniformity of such large grafts has been questioned. Processing techniques used in the sterilization and storage of such grafts is varied and represents a potential source of variation in the mechanical properties of allograft specimens. The results of this study suggest that a commercially available solvent-dehydrated form of fascia lata provides a more suitable grafting material than freeze-dried specimens obtained from tissue banks.     

Influence of gamma radiation on productivity parameters of chicken fed mycotoxin-contaminated corn

The aim of this study was to evaluate productivity parameters and carcass yield of broiler chickens fed irradiated corn contaminated with mycotoxins. For this purpose, 180 one-day-old male chicks were divided into nine treatments and fed for 42 days. The results indicated that irradiation of corn with 5 kGy improved the productivity parameters studied. Therefore, gamma radiation may become an alternative for the control of the deleterious effects of mycotoxins on broiler chickens, which cause marked economic losses for rural producers.     

异体皮质骨板在股骨假体周围骨折中的应用

目的研究异体皮质骨板在股骨假体周围骨折中的作用。方法回顾性分析2002年10月-2006年7月使用异体皮质骨板治疗的股骨假体周围骨折患者22例,其中术中骨折18例,术后骨折4例。采用Vancouver分型方法对骨折进行分类,其中A型4例,B型13例,C型5例。所有骨折均采用非骨水泥柄加异体皮质骨板支撑固定,异体皮质骨板以钢丝和(或)捆绑带与股骨固定。采用Harris评分对术后效果进行评价。结果所有患者均获随访,随访时间8~45个月,平均27.5个月,术后平均Harris评分89分。术后12~24周22例患者中21例愈合,平均愈合时间16.5周。1例患者于术后17周发生移植骨板骨折。最后一次随访时X线片均证实移植物与宿主骨整合。1例患者术后患肢疼痛,3例同侧膝关节僵直。结论异体皮质骨板是治疗股骨假体周围骨折的有效手段,能够作为生物接骨板提供机械稳定性和生物稳定性。短期随访发现使用皮质骨板有较高的骨折愈合率并能增加骨量。异体皮质骨板应在股骨假体周围骨折中常规应用。     

Comparison of temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna: results in ex vivo porcine livers

Objective

To compare temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna in ex vivo porcine livers.

Materials and methods

The 915- and 2450-MHz microwave ablation and thermal monitor system were used in this study. A total of 56 ablation zones and 280 temperature data were obtained in ex vivo porcine livers. The output powers were 50, 60, 70, and 80 W and the setting time was 600 s. The temperature curve of every temperature spot, the short- and long-axis diameters of the coagulation zones were recorded and measured.

Results

At all four power output settings, the peak temperatures of every temperature spot had a tendency to increase accordingly as the MW output power was increased, and except for 5 mm away from the antenna, the peak temperatures for the 915 MHz cooled-shaft antenna were significantly higher than those for the 2450 MHz cooled-shaft antenna (p < 0.05). Meanwhile, the short- and long-axis diameters for the 915 MHz cooled-shaft antenna were significantly larger than those for the 2450 MHz cooled-shaft antenna (p < 0.05).

Conclusion

The 915 MHz cooled-shaft antenna can yield a significantly larger ablation zone and achieve higher temperature in ablation zone than a 2450 MHz cooled-shaft antenna in ex vivo porcine livers.     

2450 MHz与915 MHz微波消融离体牛肝：消融范围、能量输出与转化的差异

目的探讨2450 MHz水冷循环与915 MHz无水冷循环微波消融离体牛肝在毁损范围、能量输出以及能量转化方面的差异。 方法新鲜离体牛肝10副,重量为5.2～6.5 kg。实验分为A组和B组,A组为2450 MHz水冷循环微波消融组,B组为915 MHz无水冷循环微波消融组。每组分别对离体牛肝进行10、20、30、40 min的消融实验。统计两种消融系统在毁损范围（平均径、体积、类圆率）、能量输出以及能量转化方面的数据,并比较其差异。 结果A组和B组的消融平均径随着消融时间延长逐渐增大。B组的消融平均径显著大于A组（P均<0.001）。消融体积在10和20 min时两组间无明显差异（P=0.44、0.65）,消融30 min以后,B组消融体积显著大于A组（P<0.001）。B组消融灶的平均径最大可达6.5 cm,消融体积最大为112.20 cm³（消融40 min）。A组的消融灶类圆率较B组更接近于1（P均<0.001）,A组消融灶的类圆性更好。在能量输出方面,A组显著高于B组（P均<0.001）,相同消融时间A组能量输出为B组的2倍以上。但能量转化效率方面,B组显著高于A组（P均<0.001）。 结论2450 MHz水冷循环微波具有更高的能量输出和类圆性更好的消融范围,但915 MHz无水冷循环微波的能量转化效率更高,所获得的消融范围更大。     

900MHz电磁辐射对体外培养大鼠海马神经干细胞超微结构的影响

目的观察900MHz电磁辐射对体外培养大鼠海马神经干细胞超微结构的影响。方法体外培养新生大鼠海马神经干细胞,分为假辐照组(0mw/cm2)、辐照1组(1mW/cm2)和辐照2组(3mW/cm2)。假辐照组在辐照1组和2组进行辐照时置于常规条件下培养。辐照1组和辐照2组又根据辐照方式不同分为2个亚组:连续辐照亚组,于细胞接种后第2天起每天辐照2h,连续6d;一次性辐照亚组,于接种后第6天一次性辐照12h。采用原子力显微镜(AFM)观察细胞表面超微结构的变化,测定细胞膜表面的平均粗糙度,以轮廓算术平均偏差(Ra)表示。采用透射电镜(TEM)观察胞内超微结构的变化。结果 900MHz电磁辐射后,与假辐照组相比,辐照1组和2组神经干细胞表面粗糙,有"孔洞"、"裂隙"样改变,细胞质均匀化改变,细胞器结构明显改变,细胞核形态结构破坏,核膜消失,染色质固缩、边集,这些改变在辐照2组更为明显。与假辐照组相比,辐照1组和2组细胞表面粗糙度(Ra)明显增加(P<0.05),其中辐照2组较辐照1组更为显著(P<0.05)。前述变化在连续辐照和一次性辐照的细胞中均存在且相似。结论 900MHz电磁辐射可致体外培养的神经干细胞胞膜和胞内超微结构出现明显的损伤样改变,且与微波辐照剂量可能有一定关系。     

Imaging of vascularized fibula autograft placed inside a massive allograft in reconstruction of lower limb bone tumors

OBJECTIVE: Bone allografts and vascularized fibula autografts were combined (the fibula inside the massive allograft) for skeletal reconstruction in a homogeneous group of patients. To verify the biologic behavior of the grafts, we followed the series using conventional radiography and CT analysis. MATERIALS AND METHODS: Twenty-four patients with bone tumors had intercalary segments of tibia or femur reconstructed and were followed up for 36-120 months. Sequential radiographs and CT scans were analyzed. RESULTS: Three types of behavior were observed. In 13 patients, the allograft maintained its architecture without fracture, although a regular enlargement of the inlaid fibula led to progressive integration with the allograft. A dense line on allograft endosteum was the first sign of bone bridges heralding fusion of the two grafts. In eight patients, fracture or nonunion of the allograft occurred, and the autograft reacted with rapid appearance of dense hypertrophy that again induced bridges to the allograft. In three patients, no changes in autograft size and density were followed by fracture with no callus formation. This behavior was interpreted as unsuccessful vascularization of the autograft. CONCLUSION: Sequential radiography and CT analysis enabled us to understand the changes in a combined graft offering an original way to revascularize bone allografts.     

血液感染的病原菌分布及耐药性分析

目的：对南充市中心医院2006年血培养中病原菌的分布及药物敏感情况进行分析,为临床治疗提供用药依据。方法：血培养用BacT/ALERT120全自动血培养仪,用VITEK-32全自动微生物分析系统和API/ATB进行细菌鉴定及药敏分析。结果：1803份血液标本中分离出病原菌242株,总阳性率为13.4%;革兰阳性菌检出率为8.7%,主要为凝固酶阴性葡萄球菌,占病原菌的38.4%,其次是金黄色葡萄球菌,占病原菌的14.9%;革兰阴性杆菌检出率为4.3%,其中以大肠埃希菌检出率较高,占病原菌的14.5%。血培养中葡萄球菌对万古霉素较为敏感,革兰阴性杆菌对阿米卡星、亚胺培南较敏感。结论：应加强血培养中病原菌及其对抗菌药物的耐药性监测。     

A genotoxic analysis of the hematopoietic system after mobile phone type radiation exposure in rats

Abstract

Purpose: In our earlier study we reported that 900 MHz continuous wave (CW) radiofrequency radiation (RFR) exposure (2 W/kg specific absorption rate [SAR]) had no significant effect on the hematopoietic system of rats. In this paper we extend the scope of the previous study by testing for possible effects at: (i) different SAR levels; (ii) both 900 and 1800 MHz, and; (iii) both CW and pulse modulated (PM) RFR.

Materials and methods: Excised long bones from rats were placed in medium and RFR exposed in (i) a Transverse Electromagnetic (TEM) cell or (ii) a waveguide. Finite-difference time-domain (FDTD) numerical analyses were used to estimate forward power needed to produce nominal SAR levels of 2/10 and 2.5/12.4 W/kg in the bone marrow. After exposure, the lymphoblasts were extracted and assayed for proliferation rate, and genotoxicity.

Results: Our data did not indicate any significant change in these end points for any combination of CW/PM exposure at 900/1800 MHz at SAR levels of nominally 2/10 W/kg or 2.5/12.4 W/kg.

Conclusions: No significant changes were observed in the hematopoietic system of rats after the exposure of CW/PM wave 900 MHz/1800 MHz RF radiations at different SAR values.