Elution characteristics of vancomycin and tobramycin combined in acrylic bone—cement

Combining two antibiotics in antibiotic-loaded bone-cement is common in clinical practice. As the effect this has on elution characteristics is unknown, an in vivo quantitative elution study was carried out. Three groups of five antibiotic-loaded cement disks were prepared and placed in individual saline baths for 5 weeks. The elution of tobramycin from the disks in the study group (containing 2.4 g tobramycin and 1.0 g vancomycin per 40-g packet of Palacos-R cement powder [Smith & Nephew Orthopaedics, Memphis, TN]) was increased by 68% over that of the tobramycin control disks (2.4 g tobramycin only) (P = .024). The release of vancomycin from the study group disks was increased by 103% over the vancomycin control disks (1.0 g vancomycin only) (P = .007). Combining two antibiotics in bone—cement improves elution of both antibiotics in vitro and may translate into enhanced elution in vivo.     

In vitro elution of vancomycin from calcium phosphate cement

Antibiotic-impregnated bone cement beads have become popular for the treatment of osteomyelitis and/or prosthesis infection. However, bone cement has the disadvantage of heating up during polymerization of cement. Recently, calcium phosphate cement (CPC) has been used as a bone replacement and augmentation, and it does not heat up during polymerization. First, we measured the release rate of vancomycin (VCM) from bone cement and CPC impregnated with VCM for 2 weeks in vitro. The mean concentration of VCM for CPC was 62.6 times at 7 days (258 ± 29 vs 4.12 ± 1.0) and 6.7 times at 13 days (15.5 ± 5.5 vs 2.3 ± 0.7). Second, we were successful in treating 2 cases of osteomyelitis and prosthesis infection with VCM-impregnated CPC. From this study, we concluded that VCM-impregnated CPC might be an effective material for the treatment of osteomyelitis and/or prosthesis infection.     

In vitro elution of tobramycin from bioabsorbable polycaprolactone beads

OBJECTIVES: To compare the in vitro elution characteristics of tobramycin impregnated beads made of polycaprolactone (PCL) and polymethylmethacrylate (PMMA). DESIGN: Six-millimeter PCL and PMMA beads with 6% tobramycin were formed and placed in phosphate-buffered saline or newborn calf serum and incubated at room temperature or 37 degrees C. Aliquots were taken at intervals for eight weeks. Tobramycin levels were determined by fluorescent assay and antibacterial efficacy was assessed by measuring the zones of inhibition against Staphylococcus aureus and Pseudomonas aeruginosa on agar diffusion plates. RESULTS: Tobramycin elution rates at room temperature were similar up to three weeks. At three weeks, elution rates from PCL beads were twice those from PMMA beads, and at eight weeks, elution from PCL was quadruple that from PMMA. At 37 degrees C, tobramycin elution rates from PCL were eight times greater than those from PMMA by eight weeks. Total tobramycin eluted from PCL beads was 38.9% and 20% in PMMA beads. All samples showed bacteriostatic activity against S. aureus and P. aeruginosa at eight weeks. CONCLUSIONS: These in vitro results show that PCL has superior antibiotic elution characteristics compared with PMMA, and this may translate into a more effective antibiotic delivery vehicle. In addition, PCL is a bioabsorbable polymer, which may decrease the need for a second surgical procedure to remove retained beads.     

The in vitro elution characteristics of vancomycin from tendons

Background  

Infection after ACL reconstruction is uncommon but catastrophic. Prophylactic graft saturation in vancomycin reportedly reduces infection rates.     

The effect of sampling method on the elution of tobramycin from calcium sulfate

Release rate is a critical property of all drug delivery vehicles, including antibiotic-laden bioerodibles. In vitro elution studies, used to evaluate release rates, use different sampling methods, including changing the entire amount of buffer and partial exchanges each day. Two groups of 10% calcium sulfate-tobramycin pellets were eluted in 20 mL of buffer for 30 days. Group I had 5 mL of buffer withdrawn and replaced daily whereas Group II had the entire 20 mL of buffer changed daily. The results show that the complete exchange method caused a significantly faster release of antibiotic than the partial exchange method. In the complete exchange group, greater than 50% of the tobramycin was released by 24 hours, whereas in the partial exchange group, 50% of the antibiotic was not released until Day 6. The two methods of sampling used to evaluate this bioerodible material provide data that allow the user to anticipate how the material will function in relatively inert and volatile environments. The method used to sample the elution of antibiotics from bioerodible materials affects the amount of antibiotic eluted. It therefore is important to know the method of sampling when making a decision to use a bioerodible material to deliver antibiotics locally.     

In vitro comparison of elution characteristics of vancomycin from calcium phosphate cement and polymethylmethacrylate

Background

Calcium phosphate cement [CPC (Biopex®)] has been used as the drug delivery system of choice for treatment of infected joint replacement because of its good elution efficiency. The influence of CPC polymerization on the bactericidal activity of vancomycin (VCM) impregnated into CPC has not been investigated. We compared VCM concentration, bactericidal activity, and profile of eluates between CPC and polymethylmethacrylate (PMMA; Cemex RX®).

Methods

Test specimens consisted of a powder composite of CPC or PMMA, VCM and solvent (10:0.25:3.3 g). Each test specimen was immersed in sterile phosphate-buffered saline. Eluates obtained on days 1, 3, 7, and 14 and weeks 4, 8, and 12 were evaluated by high performance liquid chromatography (HPLC) and by microbiological assay (MBA).

Results

The elution level of VCM from CPC/VCM on day 1 was 8.1 fold greater than that from PMMA/VCM. The detection periods of VCM from CPC/VCM and PMMA/VCM were 8 weeks and 14 days, respectively. The values of eluates from CPC/VCM and PMMA/VCM obtained by HPLC were comparable to those obtained by MBA. HPLC chromatogram showed that the elution profiles of VCM from CPC/VCM and PMMA/VCM on day 1 were very close to those of standard solutions.

Conclusions

CPC could release more VCM over a longer period than PMMA. The polymerization of CPC and PMMA did not alter the inhibitory activity of VCM and did not denature VCM.     

Antibiotic loaded calcium sulfate bead and pulse lavage eradicates biofilms on metal implant materials in vitro

Pulse lavage (PL) debridement and antibiotic loaded calcium sulfate beads (CS‐B) are both used for the treatment of biofilm related periprosthetic joint infection (PJI). However, the efficacy of these alone and in combination for eradicating biofilm from orthopaedic metal implant surfaces is unclear. The purpose of the study was to understand the efficacy of PL and antibiotic loaded CS‐B in eradicating bacterial biofilms on 316L stainless steel (SS) alone and in combination in vitro. Biofilms of bioluminescent strains of Pseudomonas aeruginosa Xen41 and a USA300 MRSA Staphylococcus aureus SAP231 were grown on SS coupons for 3 days. The coupons were either, (i) debrided for 3 s with PL, (ii) exposed to tobramycin (TOB) and vancomycin (VAN) loaded CS‐B for 24 h, or (iii) exposed to both. An untreated biofilm served as a control. The amount of biofilm was measured by bioluminescence, viable plate count and confocal microscopy using live/dead staining. PL alone reduced the CFU count of both strains of biofilms by approximately 2 orders of magnitude, from an initial cell count on metal surface of approximately 10⁹ CFU/cm². The antibiotic loaded CS‐B caused an approximate six log reduction and the combination completely eradicated viable biofilm bacteria. Bioluminescence and confocal imaging corroborated the CFU data. While PL and antibiotic loaded CS‐B both significantly reduced biofilm, the combination of two was more effective than alone in removing biofilms from SS implant surfaces. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2349–2354, 2018.

     

In vitro release of antibiotics from commercial PMMA beads and articulating hip spacers

The efficacy and benefits of high-dose antibiotic cement spacers compared with beads in the treatment of an infected prosthesis have been shown. However, in clinical practice, commercial, low-dose antibiotic bone cement is often used. This study investigated the in vitro antibiotic release of hip spacers made from Refobacin-Palacos-R or Antibiotic-Simplex-P cement compared with Septopal beads. Antibiotic concentrations were measured during 6 weeks. All carriers showed a burst release, but spacers showed little additional release after the first week. Cumulative release was 27.5 +/- 2.3 mg for Palacos, 23.8 +/- 0.2 mg for Simplex, and 188.3 +/- 9.3 mg for Septopal (P < .001). Despite the efficacy of high-dose antibiotic bone cement spacers, we believe one should be cautious toward using low-dose antibiotic bone cement for spacers because this could result in an unsuccessful eradication of infection.     

The in vitro elution characteristics of antifungal-loaded PMMA bone cement and calcium sulfate bone substitute

The use of antimicrobial-loaded delivery vehicles, most often as antibiotic beads, is common practice for the treatment of deep musculoskeletal infections. The elution of antibacterial drugs from various bone cements has been extensively studied. However, much less is known about the elution of other antimicrobials from these materials. In particular, the use of this approach for fungal infections has not been well studied despite growing concern about these difficult-to-treat organisms. Voriconazole is a broad-spectrum and highly effective antifungal that has been used in the treatment of resistant fungal pathogens. We examined the in vitro elution characteristics of voriconazole from nonabsorbable polymethylmethacrylate (PMMA) beads and from absorbable calcium sulfate beads. Voricanazole-containing beads were immersed in a 5-mL bath of phosphate-buffered saline at room temperature and placed on an orbital shaker. Eluent samples were collected over the course of 2 weeks. Concentrations of the antifungal drug in solution were measured using high-performance liquid chromatography. To verify biologic activity of the eluted antifungal, collected samples were also tested against control yeasts. We found that samples collected out to 2 weeks contained relatively high voriconazole concentrations and enough active antifungal activity to inhibit growth of the control yeasts. These data demonstrate that voriconazole retains its antifungal activity when mixed into either PMMA or calcium sulfate beads, and elutes out of beads at biologically effective concentrations over a time period of at least 2 weeks. Therefore, incorporation of voriconazole into either absorbable or nonabsorbable beads appears to be a reasonable strategy for the local delivery of a potent, broad-spectrum antifungal agent to an infected wound bed.     

重组人骨形态发生蛋白-2/万古霉素/硫酸钙药物缓释系统体外释放的实验研究

目的 研究生物可降解材料硫酸钙对万古霉素和重组人骨形态发生蛋白-2( rhBMP-2)体外缓释特性. 方法 利用高效液相色谱分析和抑菌实验检测缓释材料中万古霉素的浓度及活性,利用ELISA试验和ALP实验检测缓释材料中rhBMP-2的浓度及生物活性. 结果 rhBMP-2/万古霉素/硫酸钙药物缓解系统可释放高于55.8 μg/mL万古霉素长达144h,活性达70％以上;可释放活性rhBMP-2长达30d,对骨髓基质干细胞无抑制增殖作用,具有较高的生物安全性. 结论 rhBMP-2/万古霉素／硫酸钙药物缓解系统能缓慢释放活性万古霉素与rhBMP-2,且不会抑制骨髓基质干细胞的增殖,具有较高的临床应用前景.     

The elution of colistimethate sodium from polymethylmethacrylate and calcium phosphate cement beads

Gram-negative bacilli resistance to all antibiotics, except for colistimethate sodium (CMS), is an emerging healthcare concern. Incorporating CMS into orthopedic cement to treat bone and soft-tissue infections due to these bacteria is attractive, but the data regarding the elution of CMS from cement are conflicting. The in vitro analysis of the elution of CMS from polymethylmethacrylate (PMMA) and calcium phosphate (CP) cement beads is reported. PMMA and CP beads containing CMS were incubated in phosphate-buffered saline and the eluate sampled at sequential time points. The inhibition of the growth of a strain of Acinetobacter baumannii complex by the eluate was measured by disk diffusion and microbroth dilution assays, and the presence of CMS in the eluate was measured by mass spectroscopy. Bacterial growth was inhibited by the eluate from both PMMA and CP beads. Mass spectroscopy demonstrated greater elution of CMS from CP beads than PMMA beads. The dose of CMS in PMMA beads was limited by failure of bead integrity. CMS elutes from both CP and PMMA beads in amounts sufficient to inhibit bacterial growth in vitro. The clinical implications of these findings require further study.     

Antibiotic elution from acrylic bone cement loaded with high doses of tobramycin and vancomycin

Two‐stage revision treatment of prosthetic joint infection (PJI) frequently employs the use of a temporary bone cement spacer loaded with multiple antibiotic types. Tobramycin and vancomycin are commonly used antibiotics in cement spacers, however, there is no consensus on the relative concentrations and combinations that should be used. Therefore, the purpose of this study was to investigate the influence of dual antibiotic loading on the total antibiotic elution and compressive mechanical properties of acrylic bone cement. Varying concentrations of tobramycin (0–3 g) and vancomycin (0–3 g) were added either alone or in combination to acrylic cement (Palacos R), resulting in 12 experimental groups. Samples were submerged in 37°C saline for 28 d and sampled at specific time points. The collected eluent was analyzed to determine the cumulative antibiotic release. In addition, the cement's compressive mechanical properties and porosity were characterized. Interestingly, the cement with the highest concentration of antibiotics did not possess the best elution properties. Cement samples containing both 3 g of tobramycin and 2 g vancomycin demonstrated the highest cumulative antibiotic release after 28 d, which was coupled with a significant decrease in the mechanical properties and an increased porosity. The collected data also suggests that tobramycin elutes more effectively than vancomycin from cement. In conclusion, this study demonstrates that high antibiotic loading in cement does not necessarily lead to enhanced antibiotic elution. Clinically this information may be used to optimize cement spacer antibiotic loading so that both duration and amount of antibiotics eluted are optimized. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1078–1085, 2018.

     

硫酸钙颗粒在良性骨病损治疗中的应用

目的 探讨硫酸钙颗粒修复良性骨病损的方法及疗效.方法 对27例良性骨病损患者行囊内刮除 硫酸钙颗粒植入术,其中2例行内固定,5例病理性骨折患者(4例肱骨近端、1例股骨近端)经牵引或石膏固定骨折愈合后再行病灶刮除 硫酸钙颗粒植入术.结果 X线片显示术后6个月硫酸钙颗粒完全吸收,并发症2例,术后肢体功能:优23例,良4例.结论 硫酸钙颗粒作为新型的植骨材料,其安全、便捷、可靠,疗效确切,值得推广.     

Liquid gentamicin and vancomycin in bone cement: a potentially more cost-effective regimen

This study investigated the use of liquid gentamicin, a much less costly antibiotic (<1/20 the price of tobramycin) with a broad antimicrobial spectrum, alone and in combination with vancomycin in bone cement. Standardized cement specimens loaded with 480 mg of liquid gentamicin, 4 g of powdered vancomycin, or both antibiotics were tested for elution characteristics, bioactivity, compressive strength, and porosity. Vancomycin elution was enhanced by 146% with the addition of gentamicin liquid, and gentamicin elution was enhanced by 45% when combined with vancomycin. Bioassay confirmed the bactericidal activity of the released antibiotics. Adding liquid gentamicin increased porosity, whereas adding vancomycin did not. Compressive strength decreased by 13%, 37%, and 45% in specimens containing vancomycin, liquid gentamicin, and both antibiotics, respectively. Despite inferior mechanical properties, the temporary nature of cement beads and spacers makes the liquid gentamicin-vancomycin mixture a potentially more cost-effective regimen in bone cement to treat musculoskeletal infections.     

Local vanadium release from a calcium sulfate carrier accelerates fracture healing

This study evaluated the efficacy of using calcium sulfate (CaSO₄) as a carrier for intramedullary delivery of an organic vanadium salt, vanadyl acetylacetonate (VAC) after femoral fracture. VAC can act as an insulin‐mimetic and can be used to accelerate fracture healing in rats. A heterogenous mixture of VAC and CaSO₄ was delivered to the fracture site of BB Wistar rats, and mechanical testing, histomorphometry, micro‐computed tomography (micro‐CT) were performed to measure healing. At 4 weeks after fracture, maximum torque to failure, effective shear modulus, and effective shear stress were all significantly higher (p < 0.05) in rats treated with 0.25 mg/kg VAC–CaSO₄ as compared to carrier control rats. Histomorphometry found a 71% increase in percent cartilage matrix (p < 0.05) and a 64% decrease in percent mineralized tissue (p < 0.05) at 2 weeks after fracture in rats treated with 0.25 mg/kg of VAC–CaSO₄. Micro‐CT analyses at 4 weeks found a more organized callus structure and higher trending maximum connected z‐ray. fraction for VAC–CaSO₄ groups. Evaluation of radiographs and serial histological sections at 12 weeks did not show any evidence of ectopic bone formation. As compared to previous studies, CaSO₄ was an effective carrier for reducing the dose of VAC required to accelerate femoral fracture healing in rats. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:727–734, 2014.     

In vitro elution characteristics of commercially and noncommercially prepared antibiotic PMMA beads.

The successful treatment of osteomyelitis with commercially prepared gentamicin-polymethylmethacrylate (PMMA) (Septopal) beads and surgical debridement has led to the use of this technique in the United States. However, commercially prepared gentamicin-PMMA beads are not currently available to orthopedic surgeons in the United States. Therefore, these surgeons commonly manufacture their own antibiotic-containing cement beads in the operating room at the time of surgery. There is little data that compare the antibiotic elution characteristics of such preparations to commercially prepared gentamicin-PMMA beads. This study compares the measured amount of antibiotic elution of either gentamicin or tobramycin from laboratory manufactured Zimmer, Simplex, or Palacos beads to commercially prepared gentamicin-PMMA (Septopal) beads. During a 30-day study period, commercially prepared gentamicin-PMMA beads eluted more total antibiotic and maintain higher concentrations than did antibiotic acrylic composites manufactured in the authors' laboratory.     

医用硫酸钙在家兔腰椎融合模型中的成骨能力

[目的]通过与自体髂骨进行比较,评价医用硫酸钙单独应用的成骨能力,并探讨其可能的成骨机理。[方法]建立家兔腰椎后外侧融合模型,以自身作为对照,双侧横突间植骨,左侧植入硫酸钙颗粒,右侧植入自体髂骨。于术后3、6、12周行X线、CT及组织学检查。[结果]术后3周,硫酸钙尚可见残留颗粒,自体骨完全降解;植骨区域内均可见到大量的破骨细胞,并有血管纤维组织长入。术后6周,硫酸钙完全降解,影像学检查两者之间没有明显的差异,表现为局部骨密度增高,新骨成形;组织学检查两侧植骨区内均为大量的透明软骨形成,自体髂骨植骨区内可见散在的骨小梁结构。术后12周,组织学及影像学上二者没有任何的差别,两侧形成的骨组织与家兔的椎体骨组织结构相同。[结论]医用硫酸钙作为骨移植替代材料,除了具有良好的骨传导性外,硫酸钙可能还具有骨诱导性,其成骨能力与自体髂骨相当,医用硫酸钙单独应用可以取得良好的融合效果。     

The in vitro elution characteristics of vancomycin combined with imipenem-cilastatin in acrylic bone-cements: a pharmacokinetic study

The aim of this in vitro study was to compare the elution characteristics of vancomycin alone and in combination with imipenem-cilastatin from 3 acrylic bone-cements (CMW1 [DePuy International, Blackpool, UK], Palacos R [Schering-Plough, Wehrheim, Germany], and Simplex P [Howmedica International, London, UK]). Six groups of 3 antibiotic-loaded cement disks were prepared, incorporating 2 g of vancomycin (3 groups) and 2 g of vancomycin plus 2 g of imipenem-cilastatin (3 groups). The disks were placed in saline baths for 5 weeks, with the baths being sampled periodically and the elution rates calculated. The total amount of vancomycin released by the cements treated with vancomycin alone was 7.98 mg for CMW1, 7.74 mg for Palacos R, and 6.76 mg for Simplex P; with the addition of imipenem-cilastatin, the total amount of vancomycin released by the 3 cements increased by 30.58%, 50.52%, and 50.15%. CMW1 had better elution characteristics than the other cements when treated with vancomycin alone; the elution of Palacos R and Simplex P was better than that of CMW1 when vancomycin was combined with imipenem-cilastatin.     

The prophylactic efficacy of rifampicin-soaked graft in combination with systemic vancomycin in the prevention of prosthetic vascular graft infection: an experimental study

OBJECTIVE: To investigate the prophylactic efficacy of systemic, topical, or combined antibiotic usage in the prevention of late prosthetic vascular graft infection caused by methicillin-resistant Staphylococcus epidermidis (MRSE) and the differential adherence of S. epidermidis to Dacron and ePTFE grafts in a rat model. MATERIALS AND METHODS: Graft infections were established in the back subcutaneous tissue of 120 adult male Wistar rats by implantation of 1-cm(2) Dacron/ePTFE prosthesis followed by topical inoculation with 2 x 10(7) CFU of clinical isolate of MRSE. Each of the series included one group with no graft contamination and no antibiotic prophylaxis (uncontaminated control), one contaminated group that did not receive any antibiotic prophylaxis (untreated control), one contaminated group in which perioperative intraperitoneal prophylaxis with vancomycin (10 mg/kg) was administered, two contaminated groups that received rifampicin-soaked (5 mg/1 ml) or vancomycin-soaked (1 mg/1 ml) grafts, and one contaminated group that received a combination of rifampicin-soaked (5 mg/1 ml) graft with perioperative intraperitoneal vancomycin prophylaxis (10 mg/kg). The grafts were removed sterilely 7 days after implantation and evaluated by using sonication and quantitative blood agar culture. RESULTS: MRSE had significantly greater adherence to Dacron than ePTFE grafts in the untreated contaminated groups (P < 0.001). Rifampicin had better efficacy than vancomycin in topical application, but the difference was not statistically significant (P > 0.05). Intraperitoneal vancomycin showed a significantly higher efficacy than topical vancomycin or rifampicin (P < 0.001). The best results were provided by a combination of intraperitoneal vancomycin in rifampicin-soaked graft groups (P < 0.001). CONCLUSIONS: The combination of rifampicin and intraperitoneal vancomycin seems to be the best choice for the prophylaxis of late prosthetic vascular graft infections caused by MRSE.     

真空搅拌可注射硫酸钙在填补骨缺损手术中的应用

[目的]分析和总结可注射硫酸钙在填补骨缺损手术中的操作性和应用效果。[方法]自2004年6月～2005年8月应用真空搅拌可注射硫酸钙MIIGX3（minimally invasive injectable graft X3）填补22例骨的良性病变切除后遗留的骨缺损。男13例，女9例，年龄4—55岁，平均34．6岁。所有患者随访23～37个月，平均31．6个月。通过术后x线片评价MIIGX3吸收及自身骨长入替代的过程。[结果]应用可注射硫酸钙经真空搅拌填补骨缺损，手术操作简单、方便；术中即刻可获局部骨样强度，骨缺损充盈满意；X线片观察MIIGX3完全吸收并被自体骨替代需8～24周，吸收速度略快于骨长入，但相差不多。[结论]应用真空搅拌可注射硫酸钙MIIGX3填补骨缺损，简单易行、并发症少；材料可吸收并被自身骨替代，两者速度相差不大，是目前填充良性骨缺损的最佳人工材料之一。