Effect of organism environment upon bacteriostatic and mechanical properties of palacos R cement with antibiotic--second part]

The results of bacteriological tests of Palacos R cement with antibiotic 4 days, 7 days, 2 weeks, 3 weeks and 4 weeks after implantation in rabbit organism have been presented in this work. The results of tests of mechanical characteristics of cement with and without antibiotic samples after being kept in physiological saline for 3 to 6 weeks have also been discussed. Bacteriological tests prove that antibiotic (III generation cephalosporin) added to surgical cement retain its bacteriostatic properties. When tested on rabbits cement plus antibiotic retains its bacteriostatic properties after 4 weeks period. It has state, that by reason of prolonged time of activity antibiotic into surgical cement, it is necessary to investigate the mechanical characteristics of cement conditioned in physiological saline for 3 months at least.     

The influence of antibiotic content in CMWI bone cement on its bacteriostatic and mechanical properties]

The influence of antibiotic content in CMW1 bone cement on its bacteriostatic and mechanical properties has been investigated. It was found that antibiotics (beta lactams, II and III generation cefalosporins) preserved their bacteriostatic properties within bone cement. No significant impact of antibiotic content within CMW1 on its mechanical properties has been demonstrated.     

抗生素骨水泥物理和力学性能及洗提特性的实验研究

目的探讨头孢类抗生素加入国产骨水泥后,对其物理和力学性能的影响,以及抗生素的析出情况,以期指导临床应用。方法分别在40g骨水泥中加入1g硫酸庆大霉素、2g硫酸庆大霉素、1g头孢拉啶、1.5g头孢呋辛、1g头孢三嗪。分别测定骨水泥的面团时间、挤嵌值、压缩强度、弯曲模量和弯曲强度,并进行洗提试验。结果40g骨水泥中加入1～1.5g的抗生素不会对骨水泥的物理和力学性能产生影响;当庆大霉素剂量达到2g时,其力学性能将发生改变。头孢拉啶的洗提总量明显高于其他各组(P<0.01),而且洗提时间最长。结论抗生素能有效地从骨水泥中持续释放;40g国产骨水泥中加入1～1.5g抗生素不会影响骨水泥的物理和力学性能;在抗生素种类的选择方面,可以将头孢拉啶作为首选抗生素,而且全身应用的抗生素最好与骨水泥中应用的抗生素相一致。     

Influence of vacuum mixing on mechanical properties of homemade bone cement]

Porosity, density and rotating bar bending fatigue life of homemade bone cement are analyzed with scanning electron microscopy for two different mixing techniques: manually vacuum mixing and manually non-vacuum mixing. By vacuum mixing the rotating bar bending fatigue life is increased from 0.98 x 10(4) +/- 0.31 x 10(4) to 1.33 x 10(4) +/- 0.17 x 10(4) (P < 0.05), density increased from 1.0638 +/- 0.0005g/cm3 to 1.1024 +/- 0.0068g/cm3 (P < 0.05), porosity reduced from 10.35% +/- 2.33% to 5.83% +/- 1.74% (P < 0.05), and incidence rate of big air inclusion reduced from 5.93% to 0.9%. We believe, vacuum mixing technique of bone cement should be recommended as a routine procedure to prevent aseptic loosening of prosthesis after total joint arthroplasty.     

In vitro comparison of Refobacin-Palacos R with Refobacin Bone Cement and Palacos R + G

Background?Refobacin Palacos R (RPR) is no longer produced and Palacos R + G (PRG) and Refobacin Bone Cement R (RBC) have been introduced to supersede it. We performed an in vitro study to ascertain whether the handling and mechanical properties of the more recent cement preparations are different to those of their predecessor.

Methods?The 3 cements were tested to ISO 5833 and German DIN 53435 standards. In addition, their gentamicin elution, shrinkage, viscosity, and handling characteristics were studied.

Results?All 3 cements had comparable mechanical properties exceeding the ISO 5833 and DIN 53435 standards. They eluted similar amounts of gentamicin and had comparable shrinkage. In the batches tested, RBC showed statistically significantly longer handling curves. Both PRG and RBC had statistically significantly lower viscosities as they cured compared to their predecessor.

Interpretation?Surgeons must be aware that both successor cements do not appear to have handling curves and viscoelastic properties identical to those of RPR.     

In vitro comparison of Refobacin-Palacos R with Refobacin Bone Cement and Palacos R + G

Background Refobacin Palacos R (RPR) is no longer produced and Palacos R + G (PRG) and Refobacin Bone Cement R (RBC) have been introduced to supersede it. We performed an in vitro study to ascertain whether the handling and mechanical properties of the more recent cement preparations are different to those of their predecessor.

Methods The 3 cements were tested to ISO 5833 and German DIN 53435 standards. In addition, their gentamicin elution, shrinkage, viscosity, and handling characteristics were studied.

Results All 3 cements had comparable mechanical properties exceeding the ISO 5833 and DIN 53435 standards. They eluted similar amounts of gentamicin and had comparable shrinkage. In the batches tested, RBC showed statistically significantly longer handling curves. Both PRG and RBC had statistically significantly lower viscosities as they cured compared to their predecessor.

Interpretation Surgeons must be aware that both successor cements do not appear to have handling curves and viscoelastic properties identical to those of RPR.     

In vitro study of the efficacy of acrylic bone cement loaded with supplementary amounts of gentamicin: effect on mechanical properties, antibiotic release, and biofilm formation

Background Infection remains a severe complication following a total hip replacement. If infection is suspected when revision surgery is being performed, additional gentamicin is often added to the cement on an ad hoc basis in an attempt to reduce the risk of recurrent infection.

Methods and results In this in vitro study, we determined the effect of incorporating additional gentamicin on the mechanical properties of cement. We also determined the degree of gentamicin release from cement, and also the extent to which biofilms of clinical Staphylococcus spp. isolates form on cement in vitro. When gentamicin was added to unloaded cement (1-4 g), there was a significant reduction in the mechanical performance of the loaded cements compared to unloaded cement. A significant increase in gentamicin release from the cement over 72 h was apparent, with the amount of gentamicin released increasing significantly with each additional 1 g of gentamicin added. When overt infection was modeled, the incorporation of additional gentamicin did result in an initial reduction in bacterial colonization, but this beneficial effect was no longer apparent by 72 h, with the clinical strains forming biofilms on the cements despite the release of high levels of gentamicin.

Interpretation Our findings indicate that the addition of large amounts of gentamicin to cement is unlikely to eradicate bacteria present as a result of an overt infection of an existing implant, and could result in failure of the prosthetic joint because of a reduction in mechanical performance of the bone cement.     

The effect of centrifugation on the mechanical properties of cement. An in vitro total hip-arthroplasty model

An in vitro total hip-arthroplasty model was evaluated to determine if centrifugation of bone cement results in greater static strength and low-cycle fatigue strength than hand-mixing. The static-failure test of the stem, cement, and simulated bone composite demonstrated that the centrifuged cement had significantly greater static strength than the hand-mixed cement. However, under low-cycle fatigue tests on the same composite models, the centrifuged and hand-mixed specimens were not significantly different.     

三种抗生素骨水泥抗菌作用和机械强度的研究

目的探讨常用抗生素在国产骨水泥中的抗菌作用及对其机械性能的影响. 方法在不同细菌培养皿内放置含不同比例的硫酸妥布霉素粉剂、硫酸庆大霉素粉剂和西力欣三种抗生素的骨水泥,培养并观察抑菌环的大小和抑菌时间;同时测试含各种浓度抗生素骨水泥的抗拉强度和弹性模量. 结果 0.5～2.0 g抗生素(40 g骨水泥)对细菌有明显抑制作用,0.5～1.5 g组骨水泥抗拉强度和弹性模量较空白对照略有增加,2.0 g组开始下降.加水剂抗生素抗拉强度较粉剂和空白对照明显降低. 结论加入适量和适当剂型抗生素既可以发挥抗菌作用,同时也不降低骨水泥的机械性能.     

Elution and mechanical properties of antifungal bone cement

The effect of the incorporation of amphotericin B into bone cement was examined; as literature suggests, this may be a feasible method for the treatment of periprosthetic fungal infections. Addition of antifungal increased the compressive strength of the bone cement--a statistically significant amount from 107 +/- 2.3 to 121 +/- 1.5 MPa. Elution of tobramycin and amphotericin B was quantified using ultraviolet-visible spectroscopy. Spectroscopy showed that 18% of the antibiotic was released during the first week, with most released in the first 24 hours. The elution of antifungal, however, was unable to be detected after 1 week, with less than 0.03% released. Amphotericin B does not weaken bone cement. Its inability to be delivered at a clinically significant dose gives no clear indication for its incorporation into cement.     

The effect of endoskeleton on antibiotic impregnated cement spacer for treating deep hip infection

Backgrounds  

A two-stage revision arthroplasty was suggested optimal treatment for deep infections in hip joint. The effect of endoskeleton of cement spacers on the interim function and infection control remains unclear.     

The biomechanics of vertebroplasty. The effect of cement volume on mechanical behavior.

STUDY DESIGN: Ex vivo biomechanical study using osteoporotic cadaveric vertebral bodies. OBJECTIVE: To determine the association between the volume of cement injected during percutaneous vertebroplasty and the restoration of strength and stiffness in osteoporotic vertebral bodies, two investigational cements were studied: Orthocomp (Orthovita, Malvern, PA) and Simplex 20 (Simplex P with 20% by weight barium sulfate content; Stryker-Howmedica-Osteonics, Rutherford, NJ). SUMMARY OF BACKGROUND DATA: Previous biomechanical studies have shown that injections of 8-10 mL of cement during vertebroplasty restore or increase vertebral body strength and stiffness; however, the dose-response association between cement volume and restoration of strength and stiffness is unknown. METHODS: Compression fractures were experimentally created in 144 vertebral bodies (T6-L5) obtained from 12 osteoporotic spines harvested from female cadavers. After initial strength and stiffness were determined, the vertebral bodies were stabilized using bipedicular injections of cement totaling 2, 4, 6, or 8 mL and recompressed, after which post-treatment strength and stiffness were measured. Strength and stiffness were considered restored when post-treatment values were not significantly different from initial values. RESULTS: Strength was restored for all regions when 2 mL of either cement was injected. To restore stiffness with Orthocomp, the thoracic and thoracolumbar regions required 4 mL, but the lumbar region required 6 mL. To restore stiffness with Simplex 20, the thoracic and lumbar regions required 4 mL, but the thoracolumbar region required 8 mL. CONCLUSION: These data provide guidance on the cement volumes needed to restore biomechanical integrity to compressed osteoporotic vertebral bodies.     

The effect of antibiotic additions on the fracture properties of bone cements

Two commercially developed cements (Palacos and Zimmer) were tested for fracture toughness with and without gentamicin additions. Compact tension specimens were molded under standardized conditions and divided into four groups. Each group contained specimens of both plain and both antibiotic cements. One group was tested as zero-time controls. The remaining three groups were radiation sterilized. One group was tested as zero-time sterilization controls. Another group was tested after 2 months immersion in Ringer's lactate to elute gentamicin. The last group was tested after being implanted for 2 months subcutaneously in dogs. Comparison of the fracture toughness of the two zero-time groups showed no effect of radiation sterilization on any of the four types of cement. The results from both the group immersed in Ringer's solution and the group implanted in dogs showed no significant effect on fracture toughness with gentamicin additions. Both these groups, however, did have greater toughness values than the zero-time groups, probably caused by the more complete polymerization with time. Furthermore, the Palacos cement exhibited a greater toughness than the Zimmer cement. The results of this study demonstrate that the addition of gentamicin to bone cement is not deleterious to the fracture properties.     

Physical, mechanical and pharmacological properties of coloured bone cement with and without antibiotics

Coloured bone cements have been introduced to make the removal of cement debris easier at the time of primary and revision joint replacement. We evaluated the physical, mechanical and pharmacological effects of adding methylene blue to bone cement with or without antibiotics (gentamicin, vancomycin or both). The addition of methylene blue to plain cement significantly decreased its mean setting time (570 seconds (SD 4) vs 775 seconds (SD 11), p = 0.01), mean compression strength (95.4 MPa (SD 3) vs 100.1 MPa (SD 6), p = 0.03), and mean bending strength (65.2 MPa (SD 5) vs 76.6 MPa (SD 4), p < 0.001) as well as its mean elastic modulus (2744 MPa (SD 97) vs 3281 MPa (SD 110), p < 0.001). The supplementation of the coloured cement with vancomycin and gentamicin decreased its mean bending resistance (55.7 MPa (SD 4) vs 65.2 MPa (SD 5), p < 0.001).The methylene blue significantly decreased the mean release of gentamicin alone (228.2 μg (SD 24) vs 385.5 μg (SD 26), p < 0.001) or in combination with vancomycin (498.5 μg (SD 70) vs 613 μg (SD 25), p = 0.018) from the bone cement. This study demonstrates several theoretical disadvantages of the antibiotic-loaded bone cement coloured with methylene blue.     

The mechanical properties of cement and loosening of the femoral component of hip replacements

Mechanical and biomechanical testing of a new bone cement suggests that improved load transfer to the proximal femur could be achieved with the combination of a cement having a lower modulus, a greater ductility and a lower creep resistance than polymethylmethacrylate and a suitably shaped femoral component.     

In vitro study of the efficacy of acrylic bone cement loaded with supplementary amounts of gentamicin: Effect on mechanical properties,antibiotic release,and biofilm formation

Background?Infection remains a severe complication following a total hip replacement. If infection is suspected when revision surgery is being performed, additional gentamicin is often added to the cement on an ad hoc basis in an attempt to reduce the risk of recurrent infection.

Methods and results?In this in vitro study, we determined the effect of incorporating additional gentamicin on the mechanical properties of cement. We also determined the degree of gentamicin release from cement, and also the extent to which biofilms of clinical Staphylococcus spp. isolates form on cement in vitro. When gentamicin was added to unloaded cement (1–4 g), there was a significant reduction in the mechanical performance of the loaded cements compared to unloaded cement. A significant increase in gentamicin release from the cement over 72 h was apparent, with the amount of gentamicin released increasing significantly with each additional 1 g of gentamicin added. When overt infection was modeled, the incorporation of additional gentamicin did result in an initial reduction in bacterial colonization, but this beneficial effect was no longer apparent by 72 h, with the clinical strains forming biofilms on the cements despite the release of high levels of gentamicin.

Interpretation?Our findings indicate that the addition of large amounts of gentamicin to cement is unlikely to eradicate bacteria present as a result of an overt infection of an existing implant, and could result in failure of the prosthetic joint because of a reduction in mechanical performance of the bone cement.     

聚甲基丙烯酸甲酯骨水泥混合唑来膦酸对乳腺癌细胞的细胞毒性研究

目的观察唑来膦酸混入聚甲基丙烯酸甲酯（PMMA）骨水泥中的释放效果,并观察缓释液对乳腺癌细胞的抑制效果。方法制作骨水泥混合唑来膦酸的试件,提取骨水泥试件的缓释液,用高效液相色谱仪检测药物释放,用MTT分析法观察缓释液对乳腺癌细胞的抑制作用。结果唑来膦酸均在前24 h释放剂量最大,之后释放量明显递减,2周后释放处于极其微量状态。MTT实验显示,唑来膦酸缓释液对乳腺癌细胞抑制效果明显,抑制率和唑来膦酸浓度总体呈正相关。结论唑来膦酸可从PMMA骨水泥中有效释放,其缓释液对乳腺癌细胞抑制效果明显。     

The effect of wall mechanical properties on patency of arterial grafts

Normal arteries have properties which match the low output impedance of the heart to the high peripheral impedance. These properties can be assessed in terms of compliance (% diameter change per unit pressure change) as well as by other haemodynamic parameters. Experiments were designed using vein, Dacron and expanded polytetrafluoroethylene (PTFE) in a low flow canine femoral artery bypass model. No graft group achieved perfect patency. At twelve weeks 80% of vein grafts, 30% of Dacron grafts, and 15% of PTFE grafts remained patent. The compliance of vein grafts was maintained despite marked thickening of the wall. Patency was correlated at a highly significant level with compliance. The studies demonstrate that the matching of the mechanical properties of grafts to host arteries is important in the design of successful synthetic arterial grafts.