Antibiotic-loaded Bone Cement as Prophylaxis in Total Joint Replacement

Gentamicin and clindamycin antibiotic-eluting depot technology eradicates S. aureus in an implant-associated osteomyelitis pig model without systemic antibiotics

The therapeutic challenges of orthopedic device-related infections and emerging antimicrobial resistance have attracted attention to drug delivery technologies. This study evaluates the preclinical efficacy of local single- and dual-antibiotic therapy against implant-associated osteomyelitis (IAO) using a drug-eluting depot technology, CarboCell, that provides sustained release of high-dose antibiotics and allows for strategic in situ placement in relation to infectious lesions. Clindamycin and gentamicin were formulated in CarboCell compositions. One-stage-revision of tibial Staphylococcus aureus IAO was conducted in 19 pigs. Pigs were treated locally with CarboCell containing either gentamicin alone for 1 week or a co-formulation of gentamicin and clindamycin for 1 or 3 weeks. Bone, soft tissue, and antibiotic depots were collected for microbiology, histology, and HPLC analyses. Supporting in vivo release studies of CarboCell formulations were performed on mice. Both single- and dual-antibiotic CarboCell formulations were developed and capable of eradicating the infectious bacteria in bone and preventing colonization of implants inserted at revision. Eradication in soft tissue was observed in all pigs after 3 weeks and in 6/9 pigs after 1 week of treatment. Neutrophil counts in bone tissue were below the infection cut-off in all pigs receiving the dual-antibiotic therapies, but above in all pigs receiving the single-antibiotic therapy. Histological signs of active bone reorganization and healing were observed at 3 weeks. In conclusion, all CarboCell formulations demonstrated strong therapeutic activity against IAO, eradicating S. aureus in bone tissue and preventing colonization of implants even without the addition of systemic antibiotic therapy.

Effect of pH and hydroxyapatite-like layer formation on the antibacterial properties of borophosphate bioactive glass incorporated poly(methyl methacrylate) bone cement

Infection is a leading cause of total joint arthroplasty failure. Current preventative measures incorporate antibiotics into the poly (methyl methacrylate) (PMMA) bone cement that anchors the implant into the natural bone. With bacterial resistance to antibiotics on the rise, the development of alternative antibacterial materials is crucial to mitigate infection. Borate bioactive glass, 13-93-B3, has been studied previously for use in orthopedic applications due to its ability to be incorporated into bone cements and other scaffolds, convert into hydroxyapatite (HA)-like layer, and enhance the osseointegration and antibacterial properties of the material. The purpose of this study is to better understand how glass composition and change in surrounding pH effects the composite's antibacterial characteristics by comparing the incorporation of 30% wt/wt 13-93-B3 glass and pH neutral borophosphate bioactive glass into PMMA bone cement. We also aim to elucidate how HA-like layer formation on the cement's surface may affect bacterial adhesion. These studies showed that 13-93-B3 incorporated cements had significant reduction of bacterial growth surrounding the composite beyond 24 h of exposure when compared to a neutral borate bioactive glass incorporated cement (p < 0.01) and cement only (p < 0.0001). Additionally, through soaking cement composites in simulated body fluid and then exposing them to a bioluminescent strand of staphylococcus aureus, we found that the presence of a HA-like layer on the 13-93-B3 or pH neutral glass incorporated cement disks resulted in an increase in bacterial attachment on the composite cement's surface, where p < 0.001, and p < 0.05 respectively. Overall, our studies demonstrated that borate bioactive glass incorporated PMMA bone cement has innate antimicrobial properties that make it a promising material to prevent infection in total joint arthroplasties.

Development of a Galleria mellonella Infection Model to Evaluate the Efficacy of Antibiotic-Loaded Polymethyl Methacrylate (PMMA) Bone Cement

Prosthetic joint infections (PJIs) can have disastrous consequences for patient health, including removal of the device, and placement of cemented implants is often required during surgery to eradicate PJIs. In translational research, in vivo models are widely used to assess the biocompatibility and antimicrobial efficacy of antimicrobial coatings and compounds. Here, we aim to utilize Galleria mellonella implant infection models to assess the antimicrobial activity of antibiotic-loaded bone cement (ALBC) implants. Therefore, we used commercially available bone cement loaded with either gentamicin alone (PALACOS R+G) or with a combination of gentamicin and vancomycin (COPAL G+V), compared to bone cement without antibiotics (PALACOS R). Firstly, the in vitro antimicrobial activity of ALBC was determined against Staphylococcus aureus. Next, the efficacy of ALBC implants was analyzed in both the G. mellonella hematogenous and early-stage biofilm implant infection model, by monitoring the survival of larvae over time. After 24 h, the number of bacteria on the implant surface and in the tissue was determined. Larvae receiving dual-loaded COPAL G+V implants showed higher survival rates compared to implants loaded with only gentamicin (PALACOS R+G) and the control implants without antibiotics (PALACOS R). In conclusion, G. mellonella larvae infection models with antibiotic-loaded bone cements are an excellent option to study (novel) antimicrobial approaches.

Preparation and characterizations of antibacterial poly(methyl methacrylate) bone cement via copolymerization with a quaternary ammonium monomer of dimethylaminotriclosan methacrylate

Poly (methyl methacrylate) (PMMA) bone cement relies on the loaded antibiotic to realize the antibacterial purpose. But the exothermic behavior during setting often makes temperature-sensitive antibiotics inactivated. It is necessary to develop new material candidates to replace antibiotics. In this study, a new quaternary ammonium methacrylate (QAM) monomer called dimethylaminetriclosan methacrylate (DMATCM) was designed by the quaternization between 2-(Dimethylamino)ethyl methacrylate and triclosan, then employed as the modifier to explore the feasibility of equipping bone cement with antibacterial activity, and to investigate the variations on the physical and biological performances brought by the substitution ratio of DMATCM to MMA. Results showed that DMATCM opened its C=C bonding to participate in the MMA polymerization, and the quaternary ammonium group helped it to perform broad-spectrum antibacterial property against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. With an increased substitution ratio of DMATCM to MMA, the glass transition temperatures, the maximum exothermic temperatures, and the contact angles of bone cements declined, but the residual monomer contents, the fluid uptakes, and the setting times under Vical indentation increased. Long-term soaking made almost no changes to the weight loss and the mechanical properties of DMATCM-modified cements with lower substitution ratios of 0∼20%, and the activation rather enhanced the strengths of uncured AMBC-4 and AMBC-5 samples. Owing to more DMATCM exposed on the cement surface, the inhibition ring diameter produced by modified cement was improved to a maximum of 28.09 mm, and MC3T3-E1 cells performed the cell viabilities all beyond 70% and healthy adhesion after 72 h co-culturing. Taking all measured properties and ISO standards into account, the antibacterial bone cement under the ratio of 10% performed better, besides its good bactericidal effect, the other properties satisfied the requirements for clinical application.

Impact of Antibiotic-Loaded PMMA Spacers on the Osteogenic Potential of hMSCs

Antibiotic-loaded PMMA bone cement is frequently used in modern trauma and orthopedic surgery. Although many of the antibiotics routinely applied are described to have cytotoxic effects in the literature, clinical experience shows no adverse effects for bone healing. To determine the effects of antibiotic-loaded PMMA spacers on osteogenesis in vitro, we cultivated human bone marrow mesenchymal stem cells (BM-hMSCs) in the presence of PMMA spacers containing Gentamicin, Vancomycin, Gentamicin + Clindamycin as well as Gentamicin + Vancomycin in addition to a blank control (agarose) and PMMA containing no antibiotics. The cell number was assessed with DAPI staining, and the osteogenic potential was evaluated by directly measuring the amount of hydroxyapatite synthesized using radioactive 99mTc-HDP labelling as well as measuring the concentration of calcium and phosphate in the cell culture medium supernatant. The results showed that Gentamicin and Vancomycin as well as their combination show a certain amount of cytotoxicity but no negative effect on osteogenic potential. The combination of Gentamicin and Clindamycin, on the other hand, led to a drastic reduction in both the cell count and the osteogenic potential.

Does antibiotic bone cement reduce infection rates in primary total knee arthroplasty?

INTRODUCTION

Infection after total knee arthroplasty (TKA) impacts the patient, surgeon, and healthcare system significantly. Surgeons routinely use antibiotic-loaded bone cement (ALBC) in attempts to mitigate infection; however, little evidence supports the efficacy of ALBC in reducing infection rates compared to non-antibiotic-loaded bone cement (non-ALBC) in primary TKA. Our study compares infection rates of patients undergoing TKA with ALBC to those with non-ALBC to assess its efficacy in primary TKA.

METHODS

A retrospective review of all primary, elective, cemented TKA patients over the age of 18 between 2011 and 2020 was conducted at an orthopedic specialty hospital. Patients were stratified into two cohorts based on cement type: ALBC (loaded with gentamicin or tobramycin) or non-ALBC. Baseline characteristics and infection rates determined by MSIS criteria were collected. Multilinear and multivariate logistic regressions were performed to limit significant differences in demographics. Independent samples t test and chi-squared test were used to compare means and proportions, respectively, between the two cohorts.

RESULTS

In total, 9366 patients were included in this study, 7980 (85.2%) of whom received non-ALBC and 1386 (14.8%) of whom received ALBC. There were significant differences in five of the six demographic variables analyzed; patients with higher Body Mass Index (33.40 ± 6.27 vs. 32.09 ± 6.21; kg/m2) and Charlson Comorbidity Index values (4.51 ± 2.15 vs. 4.04 ± 1.92) were more likely to receive ALBC. The infection rate in the non-ALBC was 0.8% (63/7,980), while the rate in the ALBC was 0.5% (7/1,386). After adjusting for confounders, the difference in rates was not significant between the two groups (OR [95% CI]: 1.53 [0.69-3.38], p = 0.298). Furthermore, a sub-analysis comparing the infection rates within various demographic categories also showed no significant differences between the two groups.

CONCLUSION

Compared to non-ALBC, the overall infection rate in primary TKA was slightly lower when using ALBC; however, the difference was not statistically significant. When stratifying by comorbidity, use of ALBC still showed no statistical significance in reducing the risk of periprosthetic joint infection. Therefore, the advantage of antibiotics in bone cement to prevent infection in primary TKA is not yet elucidated. Further prospective, multicenter studies regarding the clinical benefits of antibiotic use in bone cement for primary TKA are warranted.

Effectiveness of antibiotic-loaded bone cement in total joint arthroplasty at a tertiary medical center: A retrospective cohort study

Background

Data regarding the effectiveness of antibiotic-loaded bone cement (ALBC) in preventing prosthetic joint infections (PJI) after total joint arthroplasty (TJA) is inconsistent. The objective of this study was to evaluate if the routine use of ALBC influenced the risk of revision surgery due to PJI.

Methods

This is a retrospective cohort study performed between January 2018 and September 2020. Adult patients aged ≥ 18 years who underwent TJA (knee or hip) and received either ALBC or plain cement (PC) were included. The outcome of this study was the rate of revision due to PJI. Multivariate analysis using logistic regression was used to identify factors that may be associated with increased risk of PJI, using STATA 15.1 (StataCorp LP, College Station, Texas, USA).

Results

A total of 844 patients were screened and 319 patients were included. There were 247 patients in ALBC group and 72 patients in the PC group. Only vancomycin powder was used in all ALBC cases, with a 2 g dose in 50% of the cases (dose ranged between 1 g and 8 g). The status of the prosthetic joint was assessed and recorded up to 2 years of the TJA. Overall, the difference in the rates of PJI between the two groups after primary arthroplasty was not statistically significant (5.6% vs 1.4%; p = 0.173; OR, 4.2; 95% CI, 0.5-33).

Conclusion

ALBC was not associated with a reduction in PJI rates after primary TJA. More research is needed to further evaluate the effectiveness of ALBC in preventing PJI.

Efficacy of Antibiotic Cement in Preserving Endoplants After Infection With Plate Exposure

Background: To study the feasibility and efficacy of antibiotic cement in preserving endoplants after infection in patients with early tibial plateau fracture on plate exposure. Patients and Methods: A retrospective analysis of 23 patients treated for post-operative infection with plate exposure after tibial plateau fracture between 2017 and 2021. They were divided into the observation group (10 patients) and the control group (13 patients). Total operation time, length of hospitalization, hospitalization cost, the number of surgeries, white blood cell (WBC) count, neutrophil (NEUT) count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), the post-operative evaluation index, and complications were observed during the follow-up period. Results: All patients were followed up for 6 to 12 months; wound healing was observed in both groups. The total operation time for patients in the control group was longer compared with the observation group. However, the length of hospitalization, hospitalization cost, and number of surgeries in the observation group were less compared with the control group. No difference in WBC, NEUT, ESR, and CRP levels was observed one day after surgery. Furthermore, WBC, NEUT, ESR, and CRP levels were higher in patients in the control group compared with the observation group 72 hours after surgery. There were no differences in the post-operative evaluation index and complications in both groups. Conclusions: The antibiotic cement coating used for treating early post-operative infection in patients with tibial plateau fracture could effectively control infection while retaining endoplant, thereby promoting wound healing. It could also reduce pain and the medical burden on patients.

A simple method to improve the antibiotic elution profiles from polymethylmethacrylate bone cement spacers by using rapid absorbable sutures

OBJECTIVE

Antibiotic-loaded bone cement beads and spacers have been widely used for orthopaedic infection. Poor antibiotic elution is not capable of eradicating microbial pathogens and could lead to treatment failure. The elution profiles differ among different cement formulations. Although Simplex P cement has the least release amount, it is widely used due to its ready availability. Previous methods aiming to improve the elution profiles were not translated well to clinical practice. We sought to address this by using easily available materials to improve the elution profile of antibiotics from PMMA, which allows clinicians to implement the method intraoperatively.

METHODS

Vancomycin was mixed with Simplex P cement. We used Vicryl Rapide sutures to fabricate sustained-release cement beads by repetitively passing the sutures through the beads and/or mixing suture segments into the cement formulation. Vancomycin elution was measured for 49 days. The mechanism of antibiotic release was observed with gross appearance and scanning electron microscopic images. The antimicrobial activities against MRSA were tested using an agar disk diffusion bioassay.

RESULTS

Passing Vicryl Rapide sutures through cement beads significantly improved the elution profiles in the 7-week period. The increased ratios were 9.0% on the first day and 118.0% from the 2nd day to the 49th day. Addition of suture segments did not increase release amount. The Vicryl Rapide sutures completely degraded at the periphery and partially degraded at the center. The antibiotic particles were released around the suture, while antibiotic particles kept densely entrapped in the control group. The antimicrobial activities were stronger in passing suture groups.

CONCLUSION

Passing fast absorbable sutures through PMMA cement is a feasible method to fabricate sustained-release antibiotic bone cement. Intra-cement tunnels can be formed, and the effect can last for at least 7 weeks. It is suitable for a temporary spacer between two stages of a revision surgery.

Femoral Stem Cementation in Primary Total Hip Arthroplasty

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Femoral stem cementation has undergone considerable investigation since bone cement was first used in arthroplasty, leading to the evolution of modern femoral stem cementation techniques.

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Although there is a worldwide trend toward the use of cementless components, cemented femoral stems have shown superiority in some studies and have clear indications in specific populations.

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There is a large evidence base regarding cement properties, preparation, and application techniques that underlie current beliefs and practice, but considerable controversy still exists.

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Although the cementing process adds technical complexity to total hip arthroplasty, growing evidence supports its use in certain cohorts. As such, it is critical that orthopaedic surgeons and investigators have a thorough understanding of the fundamentals and evidence underlying modern cementation techniques.

Bone healing study of alendronate combined with enoxaparin sodium bone cement in rabbits with bone defects

BACKGROUND

To observe the effect of enoxaparin sodium-polymethyl methacrylate (ES-PMMA) bone cement supplemented with alendronate (AN) on bone repair of bone defects in New Zealand rabbits.

METHODS

Twenty-seven New Zealand rabbits were randomly divided into ES/AN, ES-PMMA and PMMA groups, with a total of 27 New Zealand rabbits. The drugs loaded in 40 g bone cement powder were as follows: ES/AN group 8000 AxaIU enoxaparin (ES) and 200 mg alendronate (AN), ES-PMMA group 8000 AxaIU enoxaparin (ES), PMMA group without drugs. A bone defect model with a length of 10 mm and a diameter of 5 mm was made from the left tibia of rabbits, and the prepared bone cement was placed in the tibia defect. At 4 weeks, 8 weeks and 12 weeks after the operation, 3 rabbits in each group were sacrificed, and left tibia samples were collected for histological scoring, HE staining and Masson staining. Bone mineral density and new bone volume were measured by imaging, and the related data were processed by one-way ANOVA and least significance difference (LSD) post hoc test.

RESULTS

(1) Bone mineral density (BMD, mg/mm3) around the bone defect: at the 4th week, BMD in the ES/AN group was higher than that in the PMMA group; at the 8th week, the BMD in the ES/AN group was significantly higher than that in the other two groups; and at the 12th week, the BMD in the ES/AN group was significantly higher than that in the other two groups. (2) New bone volume (BV, mm3): at the 4th week, BV in the ES/AN group was significantly higher than that in the other two groups, BV in the ES/AN group was significantly higher than that in the other two groups at the 8th and 12th weeks, and BV in the ES-PMMA group was higher than that in the PMMA group. (3) Histological score: at the 4th and 8th weeks, the histological score of the ES/AN group was higher than that of the PMMA group, and at the 12th week, the histological score of the ES/AN group was higher than that of the other two groups. (4) Cortical bone thickness (μm): at the 4th, 8th and 12th weeks, the cortical bone thickness in the ES/AN group was higher than that in the other two groups, and the cortical bone thickness in the ES-PMMA group was higher than that in the PMMA group. (5) The percentage of mature area of new bone in the ES/AN group was higher than that in the other two groups at the 4th week, and at the 8th and 12th weeks, the percentage of mature area of new bone in the ES/AN group and ES-PMMA group was significantly higher than that in the PMMA group.

CONCLUSION

(1) Enoxaparin sodium bone cement supplemented with alendronate was superior to enoxaparin sodium bone cement and PMMA bone cement in promoting bone repair of tibial bone defects in New Zealand rabbits. (2) Enoxaparin sodium bone cement is superior to PMMA bone cement in promoting bone repair, showing a certain osteogenic potential.

When and How Should I Use Antibiotic Cement in Primary and Revision Joint Arthroplasty?

Periprosthetic joint infections (PJIs) remain one of the most challenging and devastating complications associated with total joint arthroplasty. Therefore, prevention and the ability to effectively treat PJIs are critical. One such tool for both the prevention and treatment of PJIs is the use of antibiotic-loaded bone cement (ALBC). ALBC provides an effective local delivery method of antibiotics. Low dose (<2 g per 40-g batch) is commonly used for prophylaxis, while high dose (>3.6 g per 40-g batch) is used for the treatment of PJIs. This review focuses on the efficacy, safety, and cost-effectiveness of ALBC for both the prevention as well as the treatment of PJIs.

Antibiotic Cement Utilization for the Prophylaxis and Treatment of Infections in Spine Surgery: Basic Science Principles and Rationale for Clinical Use

Antibiotic bone cement (ABC) is an effective tool for the prophylaxis and treatment of osteomyelitis due to the controlled, sustained release of local antibiotics. ABC has been proven to be effective in the orthopedic fields of arthroplasty and extremity trauma, but the adoption of ABC in spine surgery is limited. The characteristics of ABC make it an optimal solution for treating vertebral osteomyelitis (VO), a serious complication following spine surgery, typically caused by bacterial and sometimes fungal and parasitic pathogens. VO can be devastating, as infection can result in pathogenic biofilms on instrumentation that is dangerous to remove. New techniques, such as kyphoplasty and novel vertebroplasty methods, could amplify the potential of ABC in spine surgery. However, caution should be exercised when using ABC as there is some evidence of toxicity to patients and surgeons, antibiotic allergies, bone cement structural impairment, and possible development of antibiotic resistance. The purpose of this article is to describe the basic science of antibiotic cement utilization and review its usage in spine surgery.

Role of Implantable Drug Delivery Devices with Dual Platform Capabilities in the Prevention and Treatment of Bacterial Osteomyelitis

As medicine advances and physicians are able to provide patients with innovative solutions, including placement of temporary or permanent medical devices that drastically improve quality of life of the patient, there is the persistent, recurring problem of chronic bacterial infection, including osteomyelitis. Osteomyelitis can manifest as a result of traumatic or contaminated wounds or implant-associated infections. This bacterial infection can persist as a result of inadequate treatment regimens or the presence of biofilm on implanted medical devices. One strategy to mitigate these concerns is the use of implantable medical devices that simultaneously act as local drug delivery devices (DDDs). This classification of device has the potential to prevent or aid in clearing chronic bacterial infection by delivering effective doses of antibiotics to the area of interest and can be engineered to simultaneously aid in tissue regeneration. This review will provide a background on bacterial infection and current therapies as well as current and prospective implantable DDDs, with a particular emphasis on local DDDs to combat bacterial osteomyelitis.

Intra-articular administration of vancomycin and tobramycin during primary cementless total knee arthroplasty : determination of intra-articular and serum elution profiles

AIMS

Intra-articular administration of antibiotics during primary total knee arthroplasty (TKA) may represent a safe, cost-effective strategy to reduce the risk of acute periprosthetic joint infection (PJI). Vancomycin with an aminoglycoside provides antimicrobial cover for most organisms isolated from acute PJI after TKA. However, the intra-articular doses required to achieve sustained therapeutic intra-articular levels while remaining below toxic serum levels is unknown. The purpose of this study is to determine the intra-articular and serum levels of vancomycin and tobramycin over the first 24 hours postoperatively after intra-articular administration in primary cementless TKA.

METHODS

A prospective cohort study was performed. Patients were excluded if they had poor renal function, known allergic reaction to vancomycin or tobramycin, received intravenous vancomycin, or were scheduled for same-day discharge. All patients received 600 mg tobramycin and 1 g of vancomycin powder suspended in 25 cc of normal saline and injected into the joint after closure of the arthrotomy. Serum from peripheral venous blood and drain fluid samples were collected at one, four, and 24 hours postoperatively. All concentrations are reported in µg per ml.

RESULTS

A total of 22 patients were included in final analysis. At one, four, and 24 hours postoperatively, mean (95% confidence interval (CI)) serum concentrations were 2.4 (0.7 to 4.1), 5.0 (3.1 to 6.9), and 4.8 (2.8 to 6.9) for vancomycin and 4.9 (3.4 to 6.3), 7.0 (5.8 to 8.2), and 1.3 (0.8 to 1.8) for tobramycin; intra-articular concentrations were 1,900.6 (1,492.5 to 2,308.8), 717.9 (485.5 to 950.3), and 162.2 (20.5 to 304.0) for vancomycin and 2,105.3 (1,389.9 to 2,820.6), 403.2 (266.6 to 539.7), and 98.8 (0 to 206.5) for tobramycin.

CONCLUSION

Intra-articular administration of 1 g of vancomycin and 600 mg of tobramycin as a solution after closure of the arthrotomy in primary cementless TKA achieves therapeutic intra-articular concentrations over the first 24 hours postoperatively and does not reach sustained toxic levels in peripheral blood. Cite this article: Bone Joint J 2021;103-B(11):1702-1708.

Impact of High-Dose Anti-Infective Agents on the Osteogenic Response of Mesenchymal Stem Cells

Treatment of infected nonunions and severe bone infections is a huge challenge in modern orthopedics. Their treatment routinely includes the use of anti-infective agents. Although frequently used, little is known about their impact on the osteogenesis of mesenchymal stem cells. In a high- and low-dose set-up, this study evaluates the effects of the antibiotics Gentamicin and Vancomycin as well as the antifungal agent Voriconazole on the ability of mesenchymal stem cells to differentiate into osteoblast-like cells and synthesize hydroxyapatite in a monolayer cell culture. The osteogenic activity was assessed by measuring calcium and phosphate concentrations as well as alkaline phosphatase activity and osteocalcin concentration in the cell culture medium supernatant. The amount of hydroxyapatite was measured directly by radioactive ^99mTechnetium-HDP labeling. Regarding the osteogenic markers, it could be concluded that the osteogenesis was successful within the groups treated with osteogenic cell culture media. The results revealed that all anti-infective agents have a cytotoxic effect on mesenchymal stem cells, especially in higher concentrations, whereas the measured absolute amount of hydroxyapatite was independent of the anti-infective agent used. Normed to the number of cells it can therefore be concluded that the above-mentioned anti-infective agents actually have a positive effect on osteogenesis while high-dose Gentamycin, in particular, is apparently capable of boosting the deposition of minerals.

A call for action to the biomaterial community to tackle antimicrobial resistance

The global surge of antimicrobial resistance (AMR) is a major concern for public health and proving to be a key challenge in modern disease treatment, requiring action plans at all levels. Microorganisms regularly and rapidly acquire resistance to antibiotic treatments and new drugs are continuously required. However, the inherent cost and risk to develop such molecules has resulted in a drying of the pipeline with very few compounds currently in development. Over the last two decades, efforts have been made to tackle the main sources of AMR. Nevertheless, these require the involvement of large governmental bodies, further increasing the complexity of the problem. As a group with a long innovation history, the biomaterials community is perfectly situated to push forward novel antimicrobial technologies to combat AMR. Although this involvement has been felt, it is necessary to ensure that the field offers a united front with special focus in areas that will facilitate the development and implementation of such systems. This paper reviews state of the art biomaterials strategies striving to limit AMR. Promising broad-spectrum antimicrobials and device modifications are showcased through two case studies for different applications, namely topical and implantables, demonstrating the potential for a highly efficacious physical and chemical approach. Finally, a critical review on barriers and limitations of these methods has been developed to provide a list of short and long-term focus areas in order to ensure the full potential of the biomaterials community is directed to helping tackle the AMR pandemic.

In vitro elution characteristics of gentamicin- and teicoplanin-loaded CMW1 and Palacos R bone cement

PURPOSE

To compare the in vitro elution characteristics of CMW1 and Palacos R bone cement loaded with gentamicin, teicoplanin, or in combination.

METHODS

Four bone cement discs were prepared for each cement type. Disc 1 contained no antibiotics; disc 2 contained 0.5 g gentamicin; disc 3 contained 2 g teicoplanin; disc 4 contained 0.5 g gentamicin and 2 g teicoplanin. Elution studies were conducted using a fluorescence polarisation immunoassay technique and performed at intervals of 6 weeks.

RESULTS

For CMW1, gentamicin and teicoplanin elution levels in combination discs were higher than those in the single antibiotic discs (p < 0.001 & p < 0.06). For Palacos R, gentamicin elution levels in combination discs were higher than those in the single antibiotic discs (p < 0.001), but teicoplanin elution levels in combination discs were lesser than that from the single antibiotic discs (p < 0.02). In single and combination discs, gentamicin elution levels in Palacos R were higher than those in CMW1 (p < 0.001 & p < 0.001). Palacos R eluted more teicoplanin than CMW1, except in combined disc with gentamicin, when less teicoplanin was eluted.

CONCLUSION

Antibiotic elution is higher in Palacos R than CMW1. Antibiotic combination in both cement types has the synergistic effect of increasing antibiotic elution, except for teicoplanin from Palacos R. When high elution of gentamicin is required, Palacos R is preferable. When high elution of teicoplanin is required, Palacos R with only teicoplanin is superior to CMW1.

Release characteristics of enoxaparin sodium-loaded polymethylmethacrylate bone cement

BACKGROUND

This study aimed to prepare the polymethylmethacrylate (PMMA) bone cement release system with different concentrations of enoxaparin sodium (ES) and to investigate the release characteristics of ES after loading into the PMMA bone cement.

METHODS

In the experimental group, 40 g Palacos®R PMMA bone cement was loaded with various amount of ES 4000, 8000, 12,000, 16,000, 20,000, and 24,000 AXaIU, respectively. The control group was not loaded with ES. Scanning electron microscopy (SEM) was used to observe the surface microstructure of the bone cement in the two groups. In the experiment group, the mold was extracted continuously with pH7.4 Tris-HCL buffer for 10 days. The extract solution was collected every day and the anti-FXa potency was measured. The experiment design and statistical analysis were conducted using a quantitative response parallel line method.

RESULTS

Under the SEM, it was observed that ES was filled in the pores of PMMA bone cement polymer structure and released from the pores after extraction. There was a burst effect of the release. The release amount of ES on the first day was 0.415, 0.858, 1.110, 1.564, 1.952, and 2.513, respectively, from the six groups with various ES loading amount of 4000, 8000, 12,000, 16,000, 20,000, and 24,000 AXaIU, all reaching the peak of release on the first day. The release decreased rapidly on the next day and entered the plateau phase on the fourth day.

CONCLUSION

The prepared ES-PMMA bone cement has high application potential in orthopedic surgery. ES-PMMA bone cement shows good drug release characteristics. The released enoxaparin sodium has a local anti-coagulant effect within 24 h after application, but it will not be released for a long time, which is complementary to postoperative anti-coagulation therapy.

Poly(methyl methacrylate) Bone Cement Composite Can Be Refilled with Antibiotics after Implantation in Femur or Soft Tissue

While periprosthetic joint infections (PJIs) result in a small percentage of patients following arthroplasties, they are challenging to treat if they spread into bone and soft tissue. Treatment involves delivering antibiotics using poly(methyl methacrylate) (PMMA) bone cement. However, antibiotic release is insufficient for prolonged infections. Previous work demonstrated efficacy of incorporating insoluble cyclodextrin (CD) microparticles into PMMA to improve antibiotic release and allow for post-implantation drug refilling to occur in a tissue-mimicking model. To simulate how antibiotic refilling may be possible in more physiologically relevant models, this work investigated development of bone and muscle refilling models. The bone refilling model involved embedding PMMA-CD into rabbit femur and administering antibiotic via intraosseous infusion. Muscle tissue refilling model involved implanting PMMA-CD beads in bovine muscle tissue and administering antibiotic via tissue injection. Duration of antimicrobial activity of refilled PMMA-CD was evaluated. PMMA-CD composite in bone and muscle tissue models was capable of being refilled with antibiotics and resulted in prolonged antimicrobial activity. PMMA-CD provided sustained and on-demand antimicrobial activity without removal of implant if infection develops. Intraosseous infusion appeared to be a viable technique to enable refilling of PMMA-CD after implantation in bone, reporting for the first time the ability to refill PMMA in bone.

Antibacterial, proangiogenic, and osteopromotive nanoglass paste coordinates regenerative process following bacterial infection in hard tissue

Bacterial infection raises serious concerns in tissue repair settings involved with implantable biomaterials, devastating the regenerative process and even life-threatening. When hard tissues are infected with bacteria (called 'osteomyelitis'), often the cases in open fracture or chronic inflammation, a complete restoration of regenerative capacity is significantly challenging even with highly-dosed antibiotics or surgical intervention. The implantable biomaterials are thus needed to be armored to fight bacteria then to relay regenerative events. To this end, here we propose a nanoglass paste made of ~200-nm-sized silicate-glass (with Ca, Cu) particles that are hardened in contact with aqueous medium and multiple-therapeutic, i.e., anti-bacterial, pro-angiogenic and osteopromotive. The nanoglass paste self-hardened via networks of precipitated nano-islands from leached ions to exhibit ultrahigh surface area (~300 m²/g), amenable to fill tunable defects with active biomolecular interactions. Also, the nanoglass paste could release multiple ions (silicate, calcium, and copper) at therapeutically relevant doses and sustainably (for days to weeks), implying possible roles in surrounding cells/tissues as a therapeutic-ions reservoir. The osteopromotive effects of nanoglass paste were evidenced by the stimulated osteogenic differentiation of MSCs. Also, the nanoglass paste promoted angiogenesis of endothelial cells in vitro and vasculature formation in vivo. Furthermore, the significant bactericidal effect of nanoglass paste, as assessed with E. coli and S. aureus, highlighted the role of copper played in elevating ROS level and destroying homeostasis, which salvaged tissue cells from co-cultivated bacteria contamination. When administered topically to rat tibia osteomyelitis defects, the nanoglass paste enhanced in vivo bone healing and fracture resistance. The developed nanoglass paste, given its self-setting property and the coordinated therapeutic actions, is considered to be a promising drug-free inorganic biomaterial platform for the regenerative therapy of bacteria-infected hard tissues.

Antibiotic Refilling, Antimicrobial Activity, and Mechanical Strength of PMMA Bone Cement Composites Critically Depend on the Processing Technique

Antibiotic-laden poly(methyl methacrylate) (PMMA) bone cement is used in a variety of applications including temporary spacers for load-bearing arthroplasties and non-load bearing orthopedic revision procedures and antibiotic beads to treat infections. Depending upon the surgical preparation technique, properties of PMMA can widely vary. The primary objective of this work was to perform an in-depth structure-function analysis regarding how processing of PMMA impacted material and structural properties (i.e., porosity) and downstream functional properties (i.e., drug refilling and strength). PMMA with cyclodextrin (CD) microparticles was generated via hand- or vacuum-mixing and characterized for material and structural properties including porosity and internal morphology and functional properties of drug refilling, compressive strength, and antimicrobial activity. CD microparticles were incorporated into PMMA to enable functional refilling properties and to determine new information on drug distribution and distance or depth of PMMA which the refilled drug was able to penetrate. Vacuum-mixing of PMMA resulted in improved mechanical strength and allowed for incorporation of greater amounts of CD microparticles but less homogeneity relative to hand-mixing. Refilling studies showed shallow penetration of the drug into PMMA samples without CD. However, PMMA with CD microparticles showed increased depth of drug penetration, indicating that the drug could be delivered deeper within the device, resulting in more drug being available for delivery and more opportunity for later antibiotic refilling on a patient-specific basis. Knowledge of structure-function relationships can assist and provide valuable information in design and optimization of PMMA-CD for specific load-bearing or non-load-bearing applications.

Toxic Effect of Vancomycin on Viability and Functionality of Different Cells Involved in Tissue Regeneration

To prevent infections local delivery of antibiotics is a useful tool. Especially in bone fractures, vancomycin impregnated bone cements are often used allowing high concentrations of antibiotics at the infection side without high serum concentrations. However, besides potential pathogens, cells involved in tissue regeneration may also be affected by the drug. We investigated the effect of vancomycin on the viability and functionality on osteoblasts, endothelial cells, fibroblasts and skeletal muscle cells. Our results show that the viability of all cells analyzed was reduced by vancomycin and that the observed effects were time and concentration dependent. The most pronounced toxic effect was detected on day three when even the lowest concentration of 0.01 mg/ml led to a significant decrease in proliferation compared to control. Functionality assays of osteoblasts and skeletal muscle cells revealed a sensitive reaction of the cells to the drug, indicating that vancomycin is toxic to these cells during the process of differentiation. These data suggest that the vancomycin administration is critical for cell survival and function. Therefore, the concentration of administered antibiotics needs to be carefully evaluated to find a balance between defense against pathogens and functionality of host cells and tissues.

Role of Brd4 in the production of inflammatory cytokines in mouse macrophages treated with titanium particles

Brd4 protein is an important epigenetic regulator involved in the process of inflammatory cytokine production in many diseases. However, whether and how Brd4 participates in the process of wear-particle-induced inflammation remain unclear. This study aimed to investigate the potential role of Brd4 in titanium (Ti) particle-induced inflammatory cytokine production in mouse macrophage RAW264.7 cells. Our experiment detected Brd4 expressed in both normal synovium and periprosthetic osteolysis interface membrane, but the expression increased in the interface membrane as compared with that in normal synovium. Treatment with Ti particles significantly increased TNF-α, IL-6, and IL-1β production in RAW264.7 cells, which was inhibited by JQ1 or Brd4-siRNA. Ti particles enhanced the expression of Brd4, which was abrogated by JQ1. Ti particles enhanced NF-κB p65 and IKK phosphorylation and attenuated IκBα protein expression, which were abrogated by JQ1. Co-immunoprecipitation analysis indicated that Ti particles promoted the binding of Brd4 to acetylated NF-κB p65 (lysine-310), which was also abrogated in JQ1-treated RAW264.7 cells. In conclusion, Brd4 expression increases in interface membrane and Brd4 participates in the production of pro-inflammatory cytokines induced by Ti particles via promoting the activation of NF-κB signaling and binding to acetylated NF-κB p65 (lysine-310) in mouse macrophages.