http://orcid.org/0000-0002-8779-6974
Figures
Abstract
Antibiotic-loaded bone cement (ALBC) is widely used in orthopaedic surgery for both prevention and treatment of infection. Little is known about the effect of different brand combinations of antibiotic and bone cement on the elution profile and mechanical strength of ALBC. Standardized specimens that consisted of one of the 4 brands of bone cement and one of the 3 brands of vancomycin were fashioned, producing 12 combinations of ALBC. Two dosages of vancomycin in 40g bone cement were used to represent the high (4g vancomycin) and low (1g vancomycin) dose groups. Concentrations of vancomycin elution from ALBC was measured for up to 336 hours. The ultimate compression strength was tested at axial compression using a material testing machine before and after elution. In both high-dose and low-dose groups, Lyo-Vancin in PALACOS bone cement resulted in the highest cumulative elution and Vanco in Simplex P bone cement resulted in the lowest elution (458% and 65% higher in high- and low-dose groups, respectively). The mechanical strength was not significantly compromised in all groups with low dose vancomycin (range: 70.31 ± 2.74 MPa to 87.28 ± 8.26MPa after elution). However, with the addition of high dose vancomycin, there was a mixed amount of reduction in the ultimate compression strength after cement aging, ranging from 5% (Vanco in Simplex P, 81.10 ± 0.48 MPa after elution) to 38% (Sterile vancomycin in CMW, 60.94 ± 5.74 MPa after elution). We concluded that the selection of brands of vancomycin and bone cement has a great impact on the release efficacy and mechanical strength of ALBC.
Citation: Lee S-H, Tai C-L, Chen S-Y, Chang C-H, Chang Y-H, Hsieh P-H (2016) Elution and Mechanical Strength of Vancomycin-Loaded Bone Cement: In Vitro Study of the Influence of Brand Combination. PLoS ONE 11(11): e0166545. https://doi.org/10.1371/journal.pone.0166545
Editor: Masaya Yamamoto, Kyoto Daigaku, JAPAN
Received: July 2, 2016; Accepted: October 31, 2016; Published: November 17, 2016
Copyright: © 2016 Lee et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Funding: The authors received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Deep infection in orthopaedic surgery is a devastating complication, such as chronic osteomyelitis or periprosthetic joint infection. Surgeries with open procedures always carry the risk of bacterial contamination, which would turn into true infection more easily with the presence of a prosthesis or implant. Thorough debridement, adequate drainage, obliteration of dead space, and long-term systemic antibiotic have been the rule to treat orthopaedic infections. However, toxicity of systemic antibiotic requires serial monitoring of serum antibiotic level. Occasionally, compromised local blood supply reduces antibiotic concentration in the target area [1]. In light of this, local administration of antibiotics is favored in the treatment of orthopaedic infections. Ever since the introduction and increasing popularity of antibiotic-loaded bone cement (ALBC) use in total joint replacement surgery, deep infections have reduced gradually [2]. ALBC has the ability to deliver high concentration of antibiotics over a period of time and is considered an essential part both in the prevention and treatment of periprosthetic joint infection [3]. In addition to antibiotic release, ALBC is also used to fix prosthesis or as a temporary spacer in infected arthroplasty. Hence, the mechanical property of ALBC is also pivotal to a successful orthopaedic surgery.
In order to maximize the effect of ALBC, there were several researches focusing on antibiotic elution capability and mechanical strength of ALBC. Antibiotic elution efficacy has been attributed to several factors, such as type of antibiotic, mixing method, temperature at mixing, combination of different antibiotics, and addition of fillers that would increase porosity of ALBC [3–7]. Mechanical strength of ALBC is dependent on antibiotic dose, type of antibiotic, time of elution, and incorporation of fat or blood [8–10].
To our knowledge, no report has compared the effect of different brands of bone cements and antibiotics on the elution capability and mechanical property of ALBC. Vancomycin added in ALBC is an effective regimen to treat orthopaedic infections[11, 12]. In some circumstances such as revision total joint arthroplasty after eradication of methicillin-resistant Staphylococcal infection, vancomycin-loaded bone cement is also useful for prevention of periprosthetic infection[13, 14]. We attempted to identify if the profiles of vancomycin release and ultimate compression strength are different in 12 combinations of vancomycin-loaded bone cements prepared using 4 different brands of bone cement and 3 different brands of vancomycin.
Materials and Methods
Preparation of an antibiotic-loaded cement specimen
We used 4 different types of surgical grade bone cements: Surgical Simplex P (Stryker Orthopedics, Limerick, Ireland), Osteobond (Zimmer, Warsaw, IN), PALACOS R (Heraeus Medical, Newbury, UK), and Depuy-CMW (DePuy CMW, Blackpool, UK); to which vancomycin hydrochloride powders from 3 different manufacturers were added for testing. The 3 vancomycin powders were: Vanco (Gentle Pharmaceutical Co., Yulin, Taiwan), Lyo-Vancin (China Chemical & Pharmaceutical Co., Ltd, Taichung, Taiwan), and Sterile Vancomycin (Hospira Inc., Lake Forest, Illinois, USA).
The vancomycin mixture consisted of high- (4g) or low-dose (1g) vancomycin hydrochloride powder from 4 different manufacturers that was hand-mixed thoroughly with 40 g of powdered bone cement component before the 20 mL liquid monomer component was added. Following the addition of 20 mL of liquid monomer component, the cement-antibiotic mixture was hand-mixed in a ceramic container for 2 minutes to achieve a doughy status and then manually pressed into a plastic mold to form uniform test cylindrical specimens. The cement cylinders, 20 mm in height and 15 mm in diameter, were cured at room temperature for 1 hour.
Twelve groups of vancomycin-loaded bone cement were prepared: Simplex P, Osteobond, PALACOS R, or Depuy CMW bone cement that were loaded with Vanco, Lyo-Vancin, or Sterile Vancomycin. The bone cement with no antibiotic served as a control. Ten specimens were produced in each group.
Antibiotic elution testing
Six specimens in each group were used to measure antibiotic elution. Each cement cylinder was immersed in a glass tube containing 30 ml of sterile phosphate buffer solution (PBS), kept at 37°C until the designated sampling times, and then the specimen was removed from the test tube. The eluate in each test tube was frozen at −20°C until the analysis for antibiotic concentration. All cement cylinders were washed with 10 mL of PBS and then reimmersed in test tubes containing 30 mL of fresh PBS. Samples were collected at 1, 3, 6, 10, 24, 48, 72, 168, and 336 hours. Antibiotic concentration was determined by fluorescence polarization immunoassay (FPIA) using an Abbot Laboratories TDx Analyzer (Abbot Laboratories, Abbot Park, Ill). FPIA has been used in previous studies with validated results and proved to be more accurate than other assay methods [15, 16]. The lower limit of detection was 1.0 μg/ml for vancomycin.
Ultimate compression test
Four cement specimens (both before and after 336-hour antibiotic broth elution) in each group were tested for failure in axial compression using the material testing system machine (Bionix 858; MTS Corp., Eden Prairie, MN, US). The specimen was positioned on a flat supporter clamped to the MTS lower wedge grip, and then a stiffened plate was placed on the top surface of specimen. A ball-shape plunger fixed on MTS upper wedge grip was then used to apply compressive force. The experimental setup ensures full surface contact of the specimen to achieve a uniform pressure. Each specimen was compressed at a constant displacement rate of 0.1 mm/s. During testing, parameters involving force, displacement, and time were recorded simultaneously with an increase of 0.05 mm by MTS TestStar software (MTS Corp., MN, USA). The peak force divided by the cross section area (A = π,·r2 = 177 mm2) of the specimen was defined as “the ultimate compression stress for comparison among the groups.” Bone cement specimens from one of the four brands without antibiotic were used as controls. Four trials in each group were performed, including the control group, and the mean value for the ultimate compression stress of these trials was determined.
Statistical analysis
The antimicrobial concentration of elution samples and the ultimate compressive stress of cements with different preparations were tested 6 and 4 times, respectively. The results were reported as the mean and standard error. We used an analysis of variance (ANOVA) to determine the statistical difference in the ultimate compression stress and efficiency of antibiotic release between cements with different preparation methods. Tukey’s multiple comparison test was used as a post-hoc test to determine the differences between different groups. A p-value of < 0.05 was considered statistically significant.
Results
Antibiotic elution
All samples showed burst release during the first time point of the broth elution assay, then reached a plateau after 72 hours (Fig 1 and Fig 2). Elution profiles of cumulative antibiotic released from the different brands of bone cement and different brands of vancomycin with high (4g) and low (1g) dose preparations are shown in Fig 1 and Fig 2, respectively.
Graphs showing cumulative antibiotic released from cement specimens of (A) Simplex P; (B) Osteobond; (C) PALACOS R; and (D) CMW loaded with high (4g vancomycin) dose preparations of Sterile Vancomycin, Lyo-Vancin or Vanco in broth elution assay for 336 hours. Values are shown as the mean and standard error of the mean for eight specimens in each group.
Graphs showing cumulative antibiotic released from cement specimens of (A) Simplex P; (B) Osteobond; (C) PALACOS R; and (D) CMW loaded with low (1g vancomycin) dose preparations of Sterile Vancomycin, Lyo-Vancin, or Vanco in broth elution assay for 336 hours. Values are shown as the mean and standard error of the mean for eight specimens in each group.
High dose groups.
Osteobond bone cement loaded with Lyo-Vancin had a significantly higher efficiency of antibiotic release than Sterile Vancomycin group and Vanco group (p < 0.05). The same results were observed in PALACOS and CMW bone cements, in which Lyo-Vancin added groups showed higher antibiotic elution ability. However, in Simplex P bone cement, the Sterile Vancomycin group had slightly higher release efficacy. When brands of vancomycin were controlled, the release amount was the largest when PALACOS bone cement was used.
Ultimate compression strength
Mean ultimate compression strength of the 4 brands of bone cements loaded with 3 antibiotics before and after 336-hour broth elution assay relative to the cements without antibiotics are shown in Fig 3 and Fig 4. In the control groups as well as in the other combinations, all brands of bone cement show a significant reduction in ultimate compression strength.
Mean ultimate compressive strength of (A) Simplex P; (B) Osteobond; (C) PALACOS R; and (D) CMW cement samples loaded with high (4g vancomycin) dose preparations of the 3 brands of antibiotics before and after 336-hour broth elution assay relative to cement without antibiotics (control). Values are shown as the mean and standard error for each group.
Mean ultimate compressive strength of (A) Simplex P; (B) Osteobond; (C) PALACOS R; and (D) CMW cement samples loaded with low (1g vancomycin) dose preparations of 3 brands of antibiotics before and after 336-hour broth elution assay relative to cement without antibiotics (control). Values are shown as the mean and standard error for each group.
High dose groups.
The combination with the highest ultimate compression strength after elution was Vanco in Stryker Simplex P bone cement (81.10 ± 0.48 MPa), while that with the lowest was Sterile Vancomycin in Zimmer Osteobond bone cement (56.68 ± 3.74 MPa). Particularly, the mechanical property after elution was better when the antibiotic used was Vanco.
Low dose groups.
The combination with the highest ultimate compression strength after elution was Vanco in DePuy CMW bone cement (87.28 ± 8.26MPa), while that with the the lowest was sterile Vancomycin in Zimmer Osteobond bone cement (70.31 ± 2.74 MPa). As in the high dose groups, Vanco was a better choice of antibiotic in terms of the mechanical property after elution.
Discussion
Antibiotic-loaded bone cement (ALBC) has the advantage in the treatment of bone and joint infections because it can deliver high concentrations of local antibiotics, while minimizing systemic toxicity. High dose antibiotic-loaded bone cement (>3.6g per 40g bone cement) is used for beads and spacers to treat existing infection, while low dose ALBC (1 to 2g per 40g bone cement) is used for prosthesis fixation and prophylaxis of infection [17, 18]. Staphylococcus species are the most common pathogens in musculoskeletal infections, comprising 50% to 60% [19, 20]. Vancomycin, a glycopeptide, is one of the most commonly used antibiotics in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection. The use of vancomycin in bone cement, including its stability, elution efficacy, and anti-Staphylococcal ability has been confirmed in previous studies [18].
The dose of antibiotic in ALBC varies depending on the usage. For prophylactic use, antibiotic concentration should not exceed 2g in 40g of polymer. For therapeutic use, many authors recommended 3.6 to 8g in 40g of polymer [17, 21–23]. As a result, in the current study, we used 1g of vancomycin in 40g of bone cement in the low dose groups and 4g of vancomycin in 40g of bone cement in the high dose groups, which represented the prophylactic and therapeutic purpose in clinical use, respectively.
The release of antibiotic from ALBC can range from one to several days [24–26]. It can be influenced by the category and dose of the antibiotic, molecular weight, stability of the antibiotic in the presence of body fluid, bone cement property, mixing method, and curing [7, 27–29]. The antibiotic is released from the surface or cracks and voids of the cement. Due to the hydrophobicity of the polymer, the total amount of antibiotic released is less than 10% of its content, which is released mostly within the first few hours to days [30]. In our study, regardless of the combinations of bone cements and vancomycin, the trends were similar, such that vancomycin elution was high in the first 3 days and reached a plateau thereafter.
There were studies addressing the antibiotic release efficacy based on different brands of bone cement. Many authors found that different brands of bone cement would affect antibiotic elution [24, 25, 31–34], although Marks et al. found no relationship between them.[35] Cerretani et al. studied the efficacy of vancomycin elution in 3 different types of bone cement (CMW1, PALACOS R, and Simplex P). [34] They found that the release is better in the CMW1 group than in the other two. Van de Belt et al. found that the release of antibiotic from Palamed was greater than from PALACOS and CMW. [31] The authors thought that the combination of porosity and roughness of ALBC would influence gentamicin release. Other authors further proved that the initial release is affected by the roughness of the ALBC (the higher the roughness, the greater the release), and the continuous release ability is affected by the porosity of ALBC [16, 22]. Miola et al. conducted an in vitro study, which showed that the bone cement powders were similar in size and shape under scanning electron micrograph among the different brands of PMMA and that the compositional analyses did not evidence any significant difference [36]. Commercial bone cements have additional minor contents that serve different purposes, such as benzoyl peroxide as an initiator and zirconium dioxide (ZrO) or barium sulfate as radio-opacifier. ZrO, for example, is also found under scanning electron microscopy in cured bone cements [36]. Whether the amount of ZrO or other minor contents in bone cement would affect the porosity and hence the elution efficacy of ALBC necessitates further investigation.
There are some reports regarding the antimicrobial efficacy of branded and generic vancomycin products when used parentally. Vesga et al. reported inferior therapeutic effect of generic vancomycin despite being the pharmaceutical equivalent to the branded drug [37]. Others found comparative potencies between generic and branded vancomycin, but with some subtle differences [38–40]. They found some impurities existing in generic vancomycin, such as crystalline degradation product-1 (CDP-1) and CDP intermediate. Such byproducts are produced during vancomycin metabolism after deamidation of an asparagine [41]. Accumulation of CDP has been reported to have toxicity or lead to treatment failure [42]. However, to the best of our knowledge, the current literature does not report the effect of different brands of generic vancomycin on the release efficacy in ALBC. In the current study, we found varied differences in the elution capability of vancomycin when the types of bone cements were controlled. The possible explanation for this is that the byproducts of generic vancomycin aggregate in the ALBC, forming a different structure, pore size, and pore number within the PMMA. Another evidence suggests that an “impurity”, such as the like the byproducts of vancomycin, in the ALBC may influence antibiotic elution. When hand mixed, the release of vancomycin is greater in ALBC prepared using vancomycin and another antibiotic than using vancomycin alone. The effect is reduced when ALBC is mixed under vacuum condition [23, 34]. The phenomenon is explained by the fact that both antibiotics act as soluble additives that create cracks and voids in the ALBC, which increase the diffusion surface. When mixed in vacuum condition, the cracks and voids are minimized, so the effect is reduced.
During the setting of bone cement, pores are formed as a result of the chemical reaction and volume reduction, which are the starting points of cement breakage [5]. There are some significant differences in the mechanical strength of different brands of bone cement, but these differences are small compared with other factors, such as temperature, fat, or blood in the cement [10]. In general, the mechanical strength used for definite fixation of prosthesis must have ultimate compression strength of more than 70MPa as described by international industrial standard [9, 43]. In our study, the compression strength of high dose ALBCs after elution does not exceed 70MPa in Lyo-Vancin and Strerile Vancomycin groups, regardless of the brands of PMMA used. In contrast, the Vanco group exhibits enough mechanical strength before and after elution. In the low dose groups, which mimic the clinical scenario for ALBCs that are mainly for definite fixation, all combinations of different brands of PMMA and vancomycin show compression strength of more than 70MPa.
Some clinical studies compared the mechanical strength of high and low dose ALBC [8, 9, 44–46]. Some authors found that the addition of antibiotic to bone cement had no effect on the mechanical strength, while others reported a significant reduction. However, several factors would contribute to different results, such as brands of bone cement used, categories and amount of antibiotic, methods of antibiotic mixing and bone cement preparation, and methods of mechanical test [44]. Vancomycin in bone cement was studied less than gentamicin or tobramycin in the literature. Vancomycin is different in that it is an amphoteric substance with higher molecular weight. This could result in an interaction between the monomer and vancomycin, and subsequently lower molecular weight of final polymeric chains and weaker molecular strength [8]. Moreover, Topoleski et al. found that failure of ALBC usually begins with antibiotic agglomerations, which acts as stress risers [47]. Vancomycin, a much larger molecule than other antibiotics, might enhance the effect [8]. As a result, the findings in the current study that high dose ALBC has lower mechanical stress might be justified.
The literature reported contradictory results on the mechanical strength of bone cement after aging. Looney et al. reported that the strength increased in the first 1–2 weeks after the setting of bone cement [48]. Miola et al. found that the compression strength of ALBC after 14 days of elution was greater than that before elution [36]. The authors explained this phenomenon by the possible late-polymerization, post-hardening, and post-curing processes [9]. However, Ayre et al. reported reduced mechanical and fatigue properties of bone cement over time [49]. They proposed that with aging of bone cement, three processes occur simultaneously: cement has ongoing polymerization after setting and thus increases the strength; unreacted monomer and other substances diffuse out; water or body fluid penetrates in. In terms of bone cement loaded with antibiotics, the fourth process, antibiotics eluting from the antibiotic-bone cement construct, may decrease the mechanical strength. Accordingly, different bench-top settings would affect one or more of the three processes, thus changing the mechanical strength of bone cement after elution.
There are a number of limitations to this study. We did not perform a comprehensive test on the mechanical properties, such as fatigue strength and tensile strength. In addition, in the in vivo condition, continuous loading and unloading cycles may further increase the rate of degradation and weaken the mechanical strength. In addition, we used PBS as an elution solution in this in vitro study, which does not account for the in vivo conditions such as body fluid, antibiotic stability, and host response. Moreover, the mixing technique of bone cement is another issue, since PMMA mixed in vacuum condition would reduce porosity and stress risers. However, in the practical viewpoint, a proportion of surgeons continue using hand-mixing technique for ALBC preparation.
Conclusions
Different brands of PMMA bone cements loaded with different brands of vancomycin can have different elution ability and mechanical strength. In terms of vancomycin release ability, PALACOS bone cement seems to have higher elution ability in high or low dose ALBC, while Lyo-Vancin and Sterile Vancomycin have higher elution ability in high and low dose ALBC, respectively. In terms of ultimate compressive strength, no single brand of bone cement exhibit superior results. In high dose groups, several combinations fail to achieve 70MPa as recommended for definite fixation after elution, while in low dose groups all combinations pass the threshold. Our study sheds light not only of the influence of different brands of bone cement, but also of the different brands of vancomycin on the ultimate compressive strength and antibiotic elution ability, which can be more than 5 fold. Future studies on the best combination of bone cements and antibiotics can be performed to achieve the highest infection control or prevention rate, while not compromising mechanical strength.
Supporting Information
S1 Table. Vancomycin elution in high dose group when brand of vancomycin is controlled.
https://doi.org/10.1371/journal.pone.0166545.s001
(XLS)
S2 Table. Vancomycin elution in low dose group when brand of vancomycin is controlled.
https://doi.org/10.1371/journal.pone.0166545.s002
(XLSX)
S3 Table. Vancomycin elution in high dose group when brand of bone cement is controlled.
https://doi.org/10.1371/journal.pone.0166545.s003
(XLSX)
S4 Table. Vancomycin elution in low dose group when brand of bone cement is controlled.
https://doi.org/10.1371/journal.pone.0166545.s004
(XLSX)
S5 Table. Compression strength.
The tables show compression strength before and after elution in high and low dose group.
https://doi.org/10.1371/journal.pone.0166545.s005
(XLSX)
Author Contributions
- Conceptualization: PH.
- Data curation: CT.
- Formal analysis: SC CC.
- Investigation: SL CT.
- Methodology: SL CT YC PH.
- Project administration: CT PH.
- Resources: CT.
- Supervision: PH.
- Visualization: YC.
- Writing – original draft: SL.
- Writing – review & editing: CT PH.
References
- 1. Zalavras CG, Patzakis MJ, Holtom P. Local antibiotic therapy in the treatment of open fractures and osteomyelitis. Clin Orthop Relat Res. 2004(427):86–93. pmid:15552142
- 2. Malchau H, Herberts P, Ahnfelt L. Prognosis of total hip replacement in Sweden. Follow-up of 92,675 operations performed 1978–1990. Acta orthopaedica Scandinavica. 1993;64(5):497–506. pmid:8237312
- 3. Hanssen AD. Local antibiotic delivery vehicles in the treatment of musculoskeletal infection. Clin Orthop Relat Res. 2005(437):91–6. pmid:16056032
- 4. Bourne RB. Prophylactic use of antibiotic bone cement: an emerging standard—in the affirmative. J Arthroplasty. 2004;19(4 Suppl 1):69–72.
- 5. Bistolfi A, Massazza G, Verne E, Masse A, Deledda D, Ferraris S, et al. Antibiotic-loaded cement in orthopedic surgery: a review. ISRN orthopedics. 2011;2011:290851. pmid:24977058
- 6. Chang Y, Tai CL, Hsieh PH, Ueng SW. Gentamicin in bone cement: A potentially more effective prophylactic measure of infectionin joint arthroplasty. Bone & joint research. 2013;2(10):220–6.
- 7. Chen DW, Chang Y, Hsieh PH, Ueng SW, Lee MS. The influence of storage temperature on the antibiotic release of vancomycin-loaded polymethylmethacrylate. TheScientificWorldJournal. 2013;2013:573526. pmid:24027445
- 8. Persson C, Baleani M, Guandalini L, Tigani D, Viceconti M. Mechanical effects of the use of vancomycin and meropenem in acrylic bone cement. Acta orthopaedica. 2006;77(4):617–21. pmid:16929439
- 9. Pelletier MH, Malisano L, Smitham PJ, Okamoto K, Walsh WR. The compressive properties of bone cements containing large doses of antibiotics. J Arthroplasty. 2009;24(3):454–60. pmid:18534462
- 10. Lee AJ, Ling RS, Gheduzzi S, Simon JP, Renfro RJ. Factors affecting the mechanical and viscoelastic properties of acrylic bone cement. Journal of materials science Materials in medicine. 2002;13(8):723–33. pmid:15348558
- 11. Drexler M, Dwyer T, Kuzyk PR, Kosashvilli Y, Abolghasemian M, Regev GJ, et al. The results of two-stage revision TKA using Ceftazidime-Vancomycin-impregnated cement articulating spacers in Tsukayama Type II periprosthetic joint infections. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA. 2015.
- 12. Chen AF, Parvizi J. Antibiotic-loaded bone cement and periprosthetic joint infection. Journal of long-term effects of medical implants. 2014;24(2–3):89–97. pmid:25272207
- 13. Kanj WW, Flynn JM, Spiegel DA, Dormans JP, Baldwin KD. Vancomycin prophylaxis of surgical site infection in clean orthopedic surgery. Orthopedics. 2013;36(2):138–46. pmid:23379827
- 14. Chiu FY, Lin CF. Antibiotic-impregnated cement in revision total knee arthroplasty. A prospective cohort study of one hundred and eighty-three knees. J Bone Joint Surg Am. 2009;91(3):628–33. pmid:19255223
- 15. Pfaller MA, Krogstad DJ, Granich GG, Murray PR. Laboratory evaluation of five assay methods for vancomycin: bioassay, high-pressure liquid chromatography, fluorescence polarization immunoassay, radioimmunoassay, and fluorescence immunoassay. Journal of clinical microbiology. 1984;20(3):311–6. pmid:6386852
- 16. Bertazzoni Minelli E, Benini A, Magnan B, Bartolozzi P. Release of gentamicin and vancomycin from temporary human hip spacers in two-stage revision of infected arthroplasty. The Journal of antimicrobial chemotherapy. 2004;53(2):329–34. pmid:14688051
- 17. Hendriks JG, van Horn JR, van der Mei HC, Busscher HJ. Backgrounds of antibiotic-loaded bone cement and prosthesis-related infection. Biomaterials. 2004;25(3):545–56. pmid:14585704
- 18. Chang Y, Chen WC, Hsieh PH, Chen DW, Lee MS, Shih HN, et al. In vitro activities of daptomycin-, vancomycin-, and teicoplanin-loaded polymethylmethacrylate against methicillin-susceptible, methicillin-resistant, and vancomycin-intermediate strains of Staphylococcus aureus. Antimicrobial agents and chemotherapy. 2011;55(12):5480–4. pmid:21930872
- 19. Pulido L, Ghanem E, Joshi A, Purtill JJ, Parvizi J. Periprosthetic joint infection: the incidence, timing, and predisposing factors. Clin Orthop Relat Res. 2008;466(7):1710–5. pmid:18421542
- 20. Tsukayama DT, Estrada R, Gustilo RB. Infection after total hip arthroplasty. A study of the treatment of one hundred and six infections. J Bone Joint Surg Am. 1996;78(4):512–23. pmid:8609130
- 21. van de Belt H, Neut D, Schenk W, van Horn JR, van der Mei HC, Busscher HJ. Infection of orthopedic implants and the use of antibiotic-loaded bone cements. A review. Acta orthopaedica Scandinavica. 2001;72(6):557–71. pmid:11817870
- 22. Moojen DJ, Hentenaar B, Charles Vogely H, Verbout AJ, Castelein RM, Dhert WJ. In vitro release of antibiotics from commercial PMMA beads and articulating hip spacers. J Arthroplasty. 2008;23(8):1152–6. pmid:18534493
- 23. Penner MJ, Masri BA, Duncan CP. Elution characteristics of vancomycin and tobramycin combined in acrylic bone-cement. J Arthroplasty. 1996;11(8):939–44. pmid:8986572
- 24. Elson RA, Jephcott AE, McGechie DB, Verettas D. Antibiotic-loaded acrylic cement. J Bone Joint Surg Br. 1977;59(2):200–5. pmid:873980
- 25. Stevens CM, Tetsworth KD, Calhoun JH, Mader JT. An articulated antibiotic spacer used for infected total knee arthroplasty: a comparative in vitro elution study of Simplex and Palacos bone cements. Journal of orthopaedic research: official publication of the Orthopaedic Research Society. 2005;23(1):27–33.
- 26. Hendriks JG, Neut D, van Horn JR, van der Mei HC, Busscher HJ. Bacterial survival in the interfacial gap in gentamicin-loaded acrylic bone cements. J Bone Joint Surg Br. 2005;87(2):272–6. pmid:15736756
- 27. Torrado S, Frutos P, Frutos G. Gentamicin bone cements: characterisation and release (in vitro and in vivo assays). International journal of pharmaceutics. 2001;217(1–2):57–69. pmid:11292542
- 28. Tai CL, Tsai SL, Chang YH, Hsieh PH. Study the effect of polymerization temperature in the release of antibiotic from bone cement. Bio-medical materials and engineering. 2011;21(5–6):341–6. pmid:22561253
- 29. Bertazzoni Minelli E, Caveiari C, Benini A. Release of antibiotics from polymethylmethacrylate cement. Journal of chemotherapy (Florence, Italy). 2002;14(5):492–500.
- 30. Powles JW, Spencer RF, Lovering AM. Gentamicin release from old cement during revision hip arthroplasty. J Bone Joint Surg Br. 1998;80(4):607–10. pmid:9699820
- 31. van de Belt H, Neut D, Uges DR, Schenk W, van Horn JR, van der Mei HC, et al. Surface roughness, porosity and wettability of gentamicin-loaded bone cements and their antibiotic release. Biomaterials. 2000;21(19):1981–7. pmid:10941919
- 32. Chapman MW, Hadley WK. The effect of polymethylmethacrylate and antibiotic combinations on bacterial viability. An in vitro and preliminary in vivo study. J Bone Joint Surg Am. 1976;58(1):76–81. pmid:765348
- 33. Picknell B, Mizen L, Sutherland R. Antibacterial activity of antibiotics in acrylic bone cement. J Bone Joint Surg Br. 1977;59(3):302–7. pmid:408356
- 34. Cerretani D, Giorgi G, Fornara P, Bocchi L, Neri L, Ceffa R, et al. The in vitro elution characteristics of vancomycin combined with imipenem-cilastatin in acrylic bone-cements: a pharmacokinetic study. J Arthroplasty. 2002;17(5):619–26. pmid:12168180
- 35. Marks KE, Nelson CL, Lautenschlager EP. Antibiotic-impregnated acrylic bone cement. J Bone Joint Surg Am. 1976;58(3):358–64. pmid:770477
- 36. Miola M, Bistolfi A, Valsania MC, Bianco C, Fucale G, Verne E. Antibiotic-loaded acrylic bone cements: an in vitro study on the release mechanism and its efficacy. Materials science & engineering C, Materials for biological applications. 2013;33(5):3025–32.
- 37. Vesga O, Agudelo M, Salazar BE, Rodriguez CA, Zuluaga AF. Generic vancomycin products fail in vivo despite being pharmaceutical equivalents of the innovator. Antimicrobial agents and chemotherapy. 2010;54(8):3271–9. pmid:20547818
- 38. Fujimura S, Watanabe A, Fuse K, Kikuchi T, Gomi K, Tokue Y. In vitro susceptibility of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) to manufactured generic drugs compared with the brand vancomycin. International journal of antimicrobial agents. 2008;31(4):391–2. pmid:18308516
- 39. Jones RN, Watters AA, Flamm RK, Sader HS. Comparative potencies of contemporary generic vancomycin lot: in vitro assay results from nine products and a reference reagent-grade sample. Diagnostic microbiology and infectious disease. 2013;76(2):237–8. pmid:23434498
- 40. Lewis PO, Kirk LM, Brown SD. Comparison of three generic vancomycin products using liquid chromatography-mass spectrometry and an online tool. American journal of health-system pharmacy: AJHP: official journal of the American Society of Health-System Pharmacists. 2014;71(12):1029–38.
- 41. Hadwiger ME, Sommers CD, Mans DJ, Patel V, Boyne MT 2nd. Quality assessment of U.S. marketplace vancomycin for injection products using high-resolution liquid chromatography-mass spectrometry and potency assays. Antimicrobial agents and chemotherapy. 2012;56(6):2824–30. pmid:22371900
- 42. Somerville AL, Wright DH, Rotschafer JC. Implications of vancomycin degradation products on therapeutic drug monitoring in patients with end-stage renal disease. Pharmacotherapy. 1999;19(6):702–7. pmid:10391415
- 43. Bridgens J, Davies S, Tilley L, Norman P, Stockley I. Orthopaedic bone cement: do we know what we are using? J Bone Joint Surg Br. 2008;90(5):643–7. pmid:18450633
- 44. Dunne NJ, Hill J, McAfee P, Kirkpatrick R, Patrick S, Tunney M. Incorporation of large amounts of gentamicin sulphate into acrylic bone cement: effect on handling and mechanical properties, antibiotic release, and biofilm formation. Proceedings of the Institution of Mechanical Engineers Part H, Journal of engineering in medicine. 2008;222(3):355–65. pmid:18491704
- 45. Klekamp J, Dawson JM, Haas DW, DeBoer D, Christie M. The use of vancomycin and tobramycin in acrylic bone cement: biomechanical effects and elution kinetics for use in joint arthroplasty. J Arthroplasty. 1999;14(3):339–46. pmid:10220189
- 46. He Y, Trotignon JP, Loty B, Tcharkhtchi A, Verdu J. Effect of antibiotics on the properties of poly(methylmethacrylate)-based bone cement. Journal of biomedical materials research. 2002;63(6):800–6. pmid:12418027
- 47. Topoleski LD, Ducheyne P, Cuckler JM. A fractographic analysis of in vivo poly(methyl methacrylate) bone cement failure mechanisms. Journal of biomedical materials research. 1990;24(2):135–54. pmid:2329111
- 48. Looney MA, Park JB. Molecular and mechanical property changes during aging of bone cement in vitro and in vivo. Journal of biomedical materials research. 1986;20(5):555–63. pmid:3011807
- 49. Ayre WN, Denyer SP, Evans SL. Ageing and moisture uptake in polymethyl methacrylate (PMMA) bone cements. Journal of the mechanical behavior of biomedical materials. 2014;32:76–88. pmid:24445003