Local antibiotic delivery by a bioabsorbable gel is superior to PMMA bead depot in reducing infection in an open fracture model

A controlled release antibiotic wound protectant gel formulated for use in austere environments

Battlefield wounds are at high risk of infection due to gross contamination and delays in evacuation from forward-deployed locations. The aim of this study was to formulate an antibiotic wound gel for application by a field medic in austere environments to protect traumatic wounds from infection during transport. Formulation development was conducted over multiple phases to meet temperature, handling, in vitro elution, and in vivo tissue response requirements. Thermal properties were evaluated by vial inversion, DSC, and syringe expression force in a temperature range of 4-49°C. Handling was evaluated by spreading onto blood-contaminated tissue and irrigation resistance. Controlled antibiotic release was evaluated by a modified USP immersion cell dissolution method. Local tissue effects were evaluated in vivo by subcutaneous implantation in rats for 7 and 28 days. An oleogel composition of cholesterol, hydrogenated castor oil, soybean oil, and glyceryl monocaprylocaprate met the target performance criteria. Peak expression force from a 5 mL syringe at 4°C was 48.3 N, the dropping point temperature was 68°C, and the oleogel formulation could be spread onto blood-contaminated tissue and resisted aqueous irrigation. The formulation demonstrated sustained release of tobramycin in PBS at 32°C for 5 days. Implantation in a rat dorsal pocket demonstrated a slight tissue reaction after 7 days with minimal to no reaction after 28 days, comparable to a commercial hemostat control. Material resorption was evident after 28 days. The formulation met target characteristics and is appropriate for further evaluation in a large animal contaminated blast wound model.

Effectiveness of combined local therapy with antibiotics and fibrin vs. vacuum-assisted wound therapy in soft tissue infections: a retrospective study

PURPOSE

Soft tissue infections can be severe and life-threatening. Their treatment consists currently in radical surgical wound debridement and combined systemic antimicrobial therapy. Different side effects are possible. Local antibiotic therapy represents a new approach to reduce side effects and improve healing. The aim of this study is to assess the effectiveness of the local sprayed use of antibiotics with fibrin sealing compared with negative pressure wound therapy as an established treatment of soft-tissue infections.

METHODS

In this retrospective study, patients with soft tissue infections who underwent surgical treatment were analysed. One group consists of patients, who received local fibrin-antibiotic spray (FAS) (n = 62). Patients treated by vacuum-assisted wound therapy (VAWT) as the established treatment were the control group (n = 57). Main outcomes were differences in the success of healing, the duration until healing and the number of needed operations.

RESULTS

Clinical healing could be achieved for 55 patients (98.21%) in the FAS group vs. 47 patients (92.16%) in the VAWT group (p = 0.19). Time to require this was 10.65 ± 10.38 days in the FAS group and 22.85 ± 14.02 days in the VAWT group (p < 0.001). In the FAS group, patients underwent an average of 1.44 ± 0.72 vs.3.46 ± 1.66 operations in the VAWT group (p < 0.001).

CONCLUSION

Compared to vacuum-assisted wound therapy in soft tissue infections, local fibrin-antibiotic spray shows faster clinical healing and less needed operations. Leading to shorter hospital stays and more satisfied patients. The combination of sprayed fibrin and antibiotics can be seen as a promising and effective method.

Development of novel waxy bone haemostatic agents composed of biodegradable polymers with osteogenic-enhancing peptides in rabbit models

OBJECTIVES

The use of bone wax (BW) is controversial for sternal haemostasis because it increases the risk of wound infection and inhibits bone healing. We developed new waxy bone haemostatic agents made from biodegradable polymers containing peptides and evaluated them using rabbit models.

METHODS

We designed 2 types of waxy bone haemostatic agents: peptide wax (PW) and non-peptide wax (NPW), which used poly(ε-caprolactone)-based biodegradable polymers with or without an osteogenesis-enhancing peptide, respectively. Rabbits were randomly divided into 4 groups based on treatment with BW, NPW, PW or no treatment. In a tibial defect model, the bleeding amount was measured and bone healing was evaluated by micro-computed tomography over 16 weeks. Bone healing in a median sternotomy model was assessed for 2 weeks using X-ray, micro-computed tomography, histological examination and flexural strength testing.

RESULTS

The textures of PW and NPW (n = 12 each) were similar to that of BW and achieved a comparable degree of haemostasis. The crevice area of the sternal fracture line in the BW group was significantly larger than that in other groups (n = 10 each). The PW group demonstrated the strongest sternal flexural strength (n = 10), with complete tibial healing at 16 weeks. No groups exhibited wound infection, including osteomyelitis.

CONCLUSIONS

Waxy biodegradable haemostatic agents showed satisfactory results in haemostasis and bone healing in rabbit models and may be an effective alternative to BW.

Choosing the right animal model for osteomyelitis research: Considerations and challenges

Osteomyelitis is a debilitating bone disorder characterized by an inflammatory process involving the bone marrow, bone cortex, periosteum, and surrounding soft tissue, which can ultimately result in bone destruction. The etiology of osteomyelitis can be infectious, caused by various microorganisms, or noninfectious, such as chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO). Researchers have turned to animal models to study the pathophysiology of osteomyelitis. However, selecting an appropriate animal model that accurately recapitulates the human pathology of osteomyelitis while controlling for multiple variables that influence different clinical presentations remains a significant challenge. In this review, we present an overview of various animal models used in osteomyelitis research, including rodent, rabbit, avian/chicken, porcine, minipig, canine, sheep, and goat models. We discuss the characteristics of each animal model and the corresponding clinical scenarios that can provide a basic rationale for experimental selection. This review highlights the importance of selecting an appropriate animal model for osteomyelitis research to improve the accuracy of the results and facilitate the development of novel treatment and management strategies.

Local Gentamicin Fixation with Sprayed Fibrin-An In Vivo Animal Study Reveals New Options to Treat Soft Tissue Infections

For acute and chronic soft tissue infections, radical surgical debridement is required and is considered the gold standard, along with its immediate systemic antibiotic therapy. Treatment with local antibiotics and/or antibiotic-containing materials is commonly used as an additional tool in clinical practice. Spraying with fibrin and antibiotics is a newer technique that has been studied for some antibiotics. However, for gentamicin, data are not yet available on absorption, optimal application, antibiotic fate at the site and transfer of antibiotic into the blood. In an animal study involving 29 Sprague Dawley rats, 116 back wounds were sprayed with gentamicin using either gentamicin alone or one of two possible spray combinations of gentamicin and fibrin. Simultaneous application of gentamicin and fibrin via a spray system to soft tissue wounds resulted in significant antibiotic concentration over a long period of time. The technique is easy and cost-effective. The systemic crossover was significantly minimized in our study, which may have led to fewer side effects in patients. These results could lead to an improvement in local antibiotic therapy.

Microporous Implants Modified by Bifunctional Hydrogel with Antibacterial and Osteogenic Properties Promote Bone Integration in Infected Bone Defects

Prosthesis implantation and bone integration under bacterial infection are arduous challenges in clinical practice. It is well known that the reactive oxygen species (ROS) produced by bacterial infection around the bone defects will further hinder bone healing. To solve this problem, we prepared a ROS-scavenging hydrogel by cross-linking polyvinyl alcohol and a ROS-responsive linker, N¹-(4-boronobenzyl)-N³-(4-boronophenyl)-N¹, N¹, N³, N³-tetramethylpropane-1, 3-diaminium, to modify the microporous titanium alloy implant. The prepared hydrogel was used as an advanced ROS-scavenging tool to promote bone healing by inhibiting the ROS levels around the implant. Bifunctional hydrogel serving as a drug delivery system can release therapeutic molecules, including vancomycin, to kill bacteria and bone morphogenetic protein-2 to induce bone regeneration and integration. This multifunctional implant system that combines mechanical support and disease microenvironment targeting provides a novel strategy for bone regeneration and integration of implants in infected bone defects.

Allogeneic Bone Impregnated with Biodegradable Depot Delivery Systems for the Local Treatment of Joint Replacement Infections: An In Vitro Study

Although progress is evident in the effective treatment of joint replacement-related infections, it still remains a serious issue in orthopedics. As an example, the local application of antibiotics-impregnated bone grafts supplies the high drug levels without systemic side effects. However, antibiotics in the powder or solution form could be a risk for local toxicity and do not allow sustained drug release. The present study evaluated the use of an antibiotic gel, a water-in-oil emulsion, and a PLGA microparticulate solid dispersion as depot delivery systems impregnating bone grafts for the treatment of joint replacement-related infections. The results of rheological and bioadhesive tests revealed the suitability of these formulations for the impregnation of bone grafts. Moreover, no negative effect on proliferation and viability of bone marrow mesenchymal stem cells was detected. An ex vivo dissolution test of vancomycin hydrochloride and gentamicin sulphate from the impregnated bone grafts showed a reduced burst and prolonged drug release. The PLGA-based formulation proved to be particularly promising, as one-day burst release drugs was only 15% followed with sustained antibiotics release with zero-order kinetics. The results of this study will be the basis for the development of a new product in the Tissue Section of the University Hospital for the treatment of bone defects and infections of joint replacements.

FK506 increases susceptibility to musculoskeletal infection in a rodent model

Background

Delayed fracture healing caused by soft tissue loss can be resolved by the administration of a Th1 immunosuppressant, such as FK506. Additionally, open fractures are at high risk for infection. We hypothesized that the inclusion of an immunosuppressant to a subject at risk for a musculoskeletal infection will increase the likelihood of infection.

Methods

A rat model of musculoskeletal infection was used. Sprague Dawley rats received a stabilized femur defect and were inoculated with 10⁴ CFU Staphylococcus aureus via a collagen matrix. Six hours after inoculation, the wounds were debrided of collagen and devitalized tissue and irrigated with sterile saline. The animals were randomized into two groups: carrier control and FK506, which were administered daily for 14 days and were euthanized and the tissues harvested to measure local bioburden.

Results

The dosing regimen of FK506 that restored bone healing increased the bioburden in the bone and on the fixation implant compared to the carrier control animals. As expected, the administration of FK506 decreased circulating white blood cells, lymphocytes, neutrophils, and monocytes. Additionally, the red blood cell count, hematocrit, and body weight were lower in those animals that received FK506 compared to carrier control.

Conclusions

FK506 administration decreased the systemic immune cell counts and increased the bacterial bioburden within a model of musculoskeletal infection. Collectively, these outcomes could be attributed to the overall T cell suppression by FK506 and the altered antimicrobial activity of innate cells, thereby allowing S. aureus to thrive and subsequently leading to infection of severe, musculoskeletal injuries. These observations reveal the crucial continued investigation for the clinical use of FK506, and other immunosuppressant compounds, in trauma patients who are at increased risk of developing infections.

Continuous Local Antibiotics Perfusion Therapy for Acute Deep Infections after Open Fractures

Unresolved bone and soft tissue infections remain a great hindrance to fracture management worldwide, both economically and functionally for the patient. For this purpose, the benefits of local antibiotic administration besides systemic therapy have been elucidated. We present a retrospective descriptive analysis of six patients (4 males and 2 females) with acute deep infections after open fractures managed using the continuous local antibiotic perfusion (CLAP) therapy. After sufficient debridement, gentamicin solution concentrated at 1,200 μg/mL was continuously infused (2 mL/h) for 7–12 days by syringe pump through an inlet tube placed on the infected area. The antibiotics injected into the infected area were both collected and perfused by negative pressure using a negative-pressure wound therapy system. After an average of 9.5 days of CLAP therapy, symptoms of infection disappeared, and the bacterial culture was negative. There were no cases of recurrence during the follow-up period, and no complications, such as acute renal failure, ototoxicity, allergic or hypersensitivity reactions, and impaired fracture healing, were observed. All six cases were successfully managed with the CLAP therapy without any serious side effects. CLAP therapy may be a potential treatment option for acute deep infections after open fractures.

Evolution in the Acute Management of Open Fracture Treatment? Part 2

INTRODUCTION

In the first installment of this two-part series, we explored the history of open fracture treatment focusing primarily on bacteriology and antibiotic selection/stewardship. In this follow-up segment, we will analyze and summarize the other aspects of open fracture care such as time to debridement, pulsatile lavage, and open wound management (including time to closure)-finishing with summative statements and recommendations based on the current most up-to-date literature.

LEVEL OF EVIDENCE

Therapeutic Level V. See Instructions for Authors for a complete description of levels of evidence.

Clinical outcome of staged surgery after primary amputation for mangled extremity

INTRODUCTION

Amputation for a mangled extremity is an effective and reliable life-saving treatment method, which requires a relatively shorter duration for treatment than limb salvage. However, only a few studies have focused on treatment with amputation. Herein, we report good clinical outcomes achieved through staged surgery performed after amputation.

MATERIALS AND METHODS

This study included 47 patients (38 men, 9 women; average age, 52.4 years) diagnosed with mangled extremity, who underwent primary amputation between March 2014 and January 2019. The patients were divided into the initial closure (IC) groups (including 26 patients who underwent IC after amputation) and staged surgery (SS) (including 21 patients who underwent SS after amputation) groups. The presence of complications including necrosis and infection, consequent additional surgery, duration of hospitalization and expense for treatment, and functional scores of upper and lower extremities were assessed.

RESULTS

No specific postoperative complication was found in the SS group. However, additional surgeries were performed in the IC group because of complications including three cases of infection and two cases of necrosis. The differences between the hospitalization period, treatment cost, and functional examination conducted 1 year after surgery of the two groups were not statistically significant. The patients in the IC group who underwent additional surgery were hospitalized for a longer period and presented with lower functional scores due to delayed rehabilitation.

CONCLUSION

Staged surgery is a definitive and safe treatment option that can effectively reduce complications including infection and necrosis in patients with mangled extremity.

Negative pressure wound therapy does not diminish efficacy of topical antibiotic powder in a preclinical contaminated wound model

AIMS

High-energy injuries can result in multiple complications, the most prevalent being infection. Vancomycin powder has been used with increasing frequency in orthopaedic trauma given its success in reducing infection following spine surgery. Additionally, large, traumatic injuries require wound coverage and management by dressings such as negative pressure wound therapy (NPWT). NPWT has been shown to decrease the ability of antibiotic cement beads to reduce infection, but its effect on antibiotic powder is not known. The goal of this study was to determine if NPWT reduces the efficacy of topically applied antibiotic powder.

METHODS

Complex musculoskeletal wounds were created in goats and inoculated with a strain of Staphylococcus aureus modified to emit light. Six hours after contaminating the wounds, imaging, irrigation, and debridement and treatment application were performed. Animals received either vancomycin powder with a wound pouch dressing or vancomycin powder with NPWT.

RESULTS

There were no differences in eradication of bacteria when vancomycin powder was used in combination with NPWT (4.5% of baseline) compared to vancomycin powder with a wound pouch dressing (1.7% of baseline) (p = 0.986), even though approximately 50% of the vancomycin was recovered in the NPWT exudate canister.

CONCLUSION

The antimicrobial efficacy of the vancomycin powder was not diminished by the application of NPWT. These topical and locally applied therapies are potentially effective tools that can provide quick, simple treatments to prevent infection while providing coverage. By reducing the occurrence of infection, the recovery is shortened, leading to an overall improvement in quality of life. Cite this article: Bone Joint Res 2021;10(2):149-155.

Temperature-responsive PNDJ hydrogels provide high and sustained antimicrobial concentrations in surgical sites

Local antimicrobial delivery is a promising strategy for improving treatment of deep surgical site infections (SSIs) by eradicating bacteria that remain in the wound or around its margins after surgical debridement. Eradication of biofilm bacteria can require sustained exposure to high antimicrobial concentrations (we estimate 100-1000 μg/mL sustained for 24 h) which are far in excess of what can be provided by systemic administration. We have previously reported the development of temperature-responsive hydrogels based on poly(N-isopropylacrylamide-co-dimethylbutyrolactone acrylate-co-Jeffamine M-1000 acrylamide) (PNDJ) that provide sustained antimicrobial release in vitro and are effective in treating a rabbit model of osteomyelitis when instilled after surgical debridement. In this work, we sought to measure in vivo antimicrobial release from PNDJ hydrogels and the antimicrobial concentrations provided in adjacent tissues. PNDJ hydrogels containing tobramycin and vancomycin were administered in four dosing sites in rabbits (intramedullary in the femoral canal, soft tissue defect in the quadriceps, intramuscular injection in the hamstrings, and intra-articular injection in the knee). Gel and tissue were collected up to 72 h after dosing and drug levels were analyzed. In vivo antimicrobial release (43-95% after 72 h) was markedly faster than in vitro release. Drug levels varied significantly depending on the dosing site but not between polymer formulations tested. Notably, total antimicrobial concentrations in adjacent tissue in all dosing sites were sustained at estimated biofilm-eradicating levels for at least 24 h (461-3161 μg/mL at 24 h). These results suggest that antimicrobial-loaded PNDJ hydrogels are promising for improving the treatment of biofilm-based SSIs.

The combination of multi-functional ingredients-loaded hydrogels and three-dimensional printed porous titanium alloys for infective bone defect treatment

Biomaterial with the dual-functions of bone regeneration and antibacterial is a novel therapy for infective bone defects. Three-dimensional (3D)-printed porous titanium (pTi) benefits bone ingrowth, but its microporous structure conducive to bacteria reproduction. Herein, a multifunctional hydrogel was prepared from dynamic supramolecular assembly of sodium tetraborate (Na2B4O7), polyvinyl alcohol (PVA), silver nanoparticles (AgNPs) and tetraethyl orthosilicate (TEOS), and composited with pTi as an implant system. The pTi scaffolds have ideal pore size and porosity matching with bone, while the supramolecular hydrogel endows pTi scaffolds with antibacterial and biological activity. In vitro assessments indicated the 3D composite implant was biocompatible, promoted bone marrow mesenchymal stem cells (BMSCs) proliferation and osteogenic differentiation, and inhibited bacteria, simultaneously. In vivo experiments further demonstrated that the implant showed effective antibacterial ability while promoting bone regeneration. Besides distal femur defect, the innovative scaffolds may also serve as an ideal biomaterial (e.g. dental implants) for other contaminated defects.

Clinical practice in prevention of fracture-related infection: An international survey among 1197 orthopaedic trauma surgeons

INTRODUCTION

Open fractures are still a challenge in orthopaedic trauma surgery, and compared to closed fractures, the rate of complications including fracture-related infection (FRI) remains significantly higher. Although different guidelines on prevention of FRI have been published in past decades, the current recommendations vary significantly. The objectives of this international questionnaire were to evaluate clinical practice procedures for the prevention of FRI in open fractures and to evaluate adherence to available guidelines.

METHODS

A 17-item questionnaire regarding prophylaxis against infection in fracture care was administered by SurveyMonkey® and was sent via blast e-mail to all users of AOTrauma (Davos, Switzerland).

RESULTS

Overall, 1197 orthopaedic trauma surgeons answered the survey. Although cephalosporins were the most commonly prescribed agents for perioperative antibiotic prophylaxis (PAP) in open fractures, a total of 13 different antibiotics were mentioned in the survey. Furthermore, the duration of PAP was extremely variable with a tendency towards longer treatment periods with increasing open fracture severity. The majority of surgeons (71%) agreed that the optimal duration of PAP was not well defined in the literature. The use of local anti-infective agents varied significantly, although all options received additional votes with increasing injury severity. Some of the other surgical aspects addressed in this review were associated with debridement and irrigation. A delay of six hours from injury to the first debridement was acceptable to 47% of surgeons, but delays were tolerable. Normal saline was the solution used most often for wound irrigation in open fractures (89%), with low-pressure irrigation being applied most commonly (55%).

CONCLUSIONS

This international survey provided an overview of clinical practice in FRI prevention, particularly in open fracture cases. The treatment of these serious injuries remains heterogeneous. A major issue is the lack of consensus concerning type and duration of PAP. Furthermore, there seems to be no agreement on the indication for the use of local anti-infective agents. Overall, it is unknown what the repercussions are of this lack of internationally accepted guidelines on daily clinical practice, but it is clear that standardised treatment protocols are preferable in the current medical landscape.

Ciprofloxacin and Rifampin Dual Antibiotic-Loaded Biopolymer Chitosan Sponge for Bacterial Inhibition

Complex extremity wounds in Wounded Warriors can become contaminated with microbes, which may cause clinical outcomes resulting in amputation, morbidity, or even fatality. Local delivery of multiple or broad-spectrum antibiotics allows practicing clinicians treatment solutions that may inhibit biofilm formation. Propagation of vancomycin-resistant Staphylococcus aureus is also a growing concern. The development of vancomycin-resistant S. aureus has become a critical challenge in nosocomial infection prevention in the USA, but to date has seen little occurrence in osteomyelitis. As an alternative, locally delivered ciprofloxacin and rifampin were investigated in a preclinical model for the prevention of biofilm in complex extremity wounds with implanted fixation device. In vitro assays demonstrated ciprofloxacin and rifampin possess an additive effect against Gram-negative Pseudomonas aeruginosa and were actively eluted from a chitosan sponge based local delivery system. In an in vivo orthopedic hardware-associated polymicrobial model (S. aureus and Escherichia coli) the combination was able to achieve complete clearance of both bacterial strains. E. coli was detected in bone of untreated animals, but did not form biofilm on wires. Results reveal the clinical potential of antibiotic-loaded chitosan sponges to inhibit infection through tailored antibiotic selection at desired concentrations with efficacy towards biofilm inhibition.

In vitro evaluation of local antibiotic delivery via fibrin hydrogel

BACKGROUND/PURPOSE

Fibrin hydrogel is commonly used as hemostatic agent and scaffold but it is questionable for carrying antibiotics. Thus, this study aimed to investigate whether the fibrin hydrogel can be used to deliver the optimal concentration of ciprofloxacin against oral pathogen.

MATERIALS AND METHODS

The optimal concentration of ciprofloxacin was investigated from broth microdilution technique against three common oral bacteria. Ten times the bactericidal concentration of ciprofloxacin loaded to 0.4% fibrin hydrogel was observed by using a confocal laser scanning microscope and then was left in tris-buffer saline solution (TBS) for 0, 1, 12, 24, 72 and 168 h in parallel with the control group of ciprofloxacin loaded to 0.5% alginate hydrogel and ciprofloxacin solution. Spectrophotometer was used to analyze the accumulated drug release from the collected TBS, of which the measurement method was calibrated. The efficacy of the released ciprofloxacin was tested using an agar well diffusion assay. The inhibition zone of the released ciprofloxacin from fibrin hydrogel was statistically compared with 150 and 1500 μg/ml ciprofloxacin solution, while non-loaded fibrin hydrogel served as the control.

RESULTS

The results revealed that minimum inhibitory concentration was 1-2 μg/ml and minimum bactericidal concentration was 4-15 μg/ml. The fibrin hydrogel gradually released ciprofloxacin until 168 h while the alginate hydrogel immediately liberated all the loaded ciprofloxacin within an hour. The agar well diffusion significantly showed greater clear zone in fibrin hydrogel loaded ciprofloxacin compared to non-loaded fibrin hydrogel but not with ciprofloxacin in TBS.

CONCLUSION

The results suggested that fibrin hydrogel can be used for local ciprofloxacin delivery without interfering the efficacy of ciprofloxacin.

Elastin-like polypeptide incorporated thermally sensitive liposome improve antibiotic therapy against musculoskeletal bacterial pathogens

Musculoskeletal infections caused by bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa in children and adults can lead to adverse outcomes including a need for extensive surgical debridement and limb amputation. To enable targeted antimicrobial release in infected tissues, the objective of this study was to design and investigate novel elastin-like polypeptide (ELP)-based thermally sensitive liposomes in vitro. ELP biopolymers can change their phase behaviour at higher temperatures. We hypothesised that ELP-TSL will improve therapeutic efficacy by releasing antimicrobial payloads locally at higher temperatures (≥39 °C). ELP-TSL library were formulated by varying cholesterol and phospholipid composition by the thin film and extrusion method. A broad-spectrum antimicrobial (Ciprofloxacin or Cipro) was encapsulated inside the liposomes by the ammonium sulphate gradient method. Cipro release from ELP-TSLs was assessed in physiological buffers containing ∼25% serum by fluorescence spectroscopy, and efficacy against Staphylococcus aureus and Pseudomonas aeruginosa was assessed by disc diffusion and planktonic assay. Active loading of Cipro achieved an encapsulation efficiency of 40-70% in the ELP-TSL depending upon composition. ELP-TSL Cipro release was near complete at ≥39 °C; however, the release rates could be delayed by cholesterol. Triggered release of Cipro from ELP-TSL at ∼42 °C induced significant killing of S. aureus and P. aeruginosa compared to 37 °C. Our in vitro data suggest that ELP-TSL may potentially improve bacterial wound therapy in patients.

Local fixation of antibiotics with fibrin spray on soft tissues: experimental study on the relevance of the application techniques

OBJECTIVE

In acute and chronic infections of soft tissue, a radical surgical debridement is necessary, and is regarded as the 'Gold Standard, as well as an immediately systemic antibiotic therapy. Additional treatment with local antibiotics and/or antibiotic-containing materials is commonly used in clinical settings, but the efficient concentration of the antibiotic is not well-known.

METHODS

Aside from the typical procedures which are provided and supported by the industry, we have conducted an animal study including 39 Sprague Dawley rats. We have treated the back sores with local antibiotics (vancomycin) alone or in two combinations with a fibrin-glue spray technique.

RESULTS

It could be demonstrated that, in particular, the simultaneous application of vancomycin and fibrin leads to a stable antibiotic concentration and a long period of time wherein the antibiotic substance remains in the tissue.

CONCLUSIONS

This easy and inexpensive method of application can be a promising factor for the clinical improvement of local antibiotic therapy.

Intrawound Vancomycin Powder Reduces Bacterial Load in Contaminated Open Fracture Model

OBJECTIVES

To compare the effectiveness of both vancomycin powder and antibiotic bead placement to irrigation and debridement alone in prevention of infection in a contaminated open fracture model in rats.

METHODS

In a previously described model of contaminated open fractures, 45 rats had simulated open fractures created, stabilized, and contaminated with Staphylococcus aureus. They were then treated 6 hours later with 3 interventions: irrigation and debridement alone (control group) or in combination with placement of polymethyl methacrylate beads containing vancomycin and tobramycin powders (antibiotic bead group) or placement of 10 mg of intrawound vancomycin powder (powder group). Rats were allowed to recover and then killed 14 days later for harvest of femurs and plates. Femurs and plates were both incubated overnight, and bacterial colonies were counted in each group for comparison.

RESULTS

Quantitative counts of bacteria in bone showed significantly reduced growth in both bead and powder groups when compared with control group (P < 0.0001). Quantitative counts of bacteria in plates showed significantly reduced growth in both bead and powder groups when compared with control group (P < 0.0003; 0.029). No significant differences were seen in bacterial growth between bead and powder groups for either bones (P = 0.13) or plates (P = 0.065).

CONCLUSIONS

When compared with irrigation and debridement alone, placement of intrawound vancomycin powder significantly decreased bacterial load in a contaminated open fracture model in rats similar to placing antibiotic beads. This may provide an additional adjuvant treatment that does not require a secondary surgery for bead removal.

The effect of local antibiotic prophylaxis when treating open limb fractures: A systematic review and meta-analysis

Objectives

As well as debridement and irrigation, soft-tissue coverage, and osseous stabilization, systemic antibiotic prophylaxis is considered the benchmark in the management of open fractures and considerably reduces the risk of subsequent fracture-related infections (FRI). The direct application of antibiotics in the surgical field (local antibiotics) has been used for decades as additional prophylaxis in open fractures, although definitive evidence confirming a beneficial effect is scarce. The purpose of the present study was to review the clinical evidence regarding the effect of prophylactic application of local antibiotics in open limb fractures.

Methods

A comprehensive literature search was performed in PubMed, Web of Science, and Embase. Cohort studies investigating the effect of additional local antibiotic prophylaxis compared with systemic prophylaxis alone in the management of open fractures were included and the data were pooled in a meta-analysis.

Results

In total, eight studies which included 2738 patients were eligible for quantitative synthesis. The effect of antibiotic-loaded poly(methyl methacrylate) beads was investigated by six of these studies, and two studies evaluated the effect of local antibiotics applied without a carrier. Meta-analysis showed a significantly lower infection rate when local antibiotics were applied (4.6%; 91/1986) than in the control group receiving standard systemic prophylaxis alone (16.5%; 124/752) (p < 0.001) (odds ratio 0.30; 95% confidence interval 0.22 to 0.40).

Conclusion

This meta-analysis suggests a risk reduction in FRI of 11.9% if additional local antibiotics are given prophylactically for open limb fractures. However, due to limited quality, heterogeneity, and considerable risk of bias, the pooling of data from primary studies has to be interpreted with caution.

Cite this article: M. Morgenstern, A. Vallejo, M. A. McNally, T. F. Moriarty, J. Y. Ferguson, S. Nijs, WJ. Metsemakers. Bone Joint Res 2018;7:447–456. The effect of local antibiotic prophylaxis when treating open limb fractures: A systematic review and meta-analysis. DOI: 10.1302/2046-3758.77.BJR-2018-0043.R1

[Local fixation of antibiotics by fibrin spray : In bone defects with soft tissue involvement]

In acute and chronic bone infections with concomitant soft tissue involvement the current gold standard is radical surgical debridement including explantation of the infected prosthetic devices. This is followed by initiation of systemic antibiotic therapy appropriate for the antibiogram. Several revision operations are often necessary to achieve complete healing. Additional treatment with local antibiotics or antibiotic-containing substances is routinely used in bone surgery. Apart from the typical procedures with commercially available products, we have conducted a study with 21 patients by application of local antibiotic treatment in combination with the fibrin glue spray technique and evaluated the results. Out of nine wounds of the lower extremities with bone involvement, total healing could be achieved in eight cases. We were also successful in two out of three very complex pelvic wounds; however, as expected the implant infections were complicated. Out of the seven desolate cases we were only able to achieve complete long-term healing in two cases. In the meantime we routinely use the described method in such special disastrous infection situations; however, this is carried out only in combination with established surgical procedures in sepsis surgery and anti-infection management.

Inhibition of fracture healing in the presence of contamination by Staphylococcus aureus: Effects of growth state and immune response

Extremity injuries comprise a significant portion of trauma, affecting quality of life, financial burden, and return to duty. Bacterial contamination is commonly associated with failure to heal, despite antibiotic treatment, suggesting that additional therapies must be developed to combat these complications. Treatment failure is likely due to the presence of resistant microbial communities known as biofilms. Biofilm bacteria are able to elicit a direct inhibition of healing through a multitude of known factors. However, they likely also inhibit healing through alteration of the inflammatory response. As inflammation is a critical step in fracture healing, how the presence of biofilm bacteria shifts this response to one that is suboptimal for healing is an important consideration that is currently understudied. The profile of inflammatory factors in response to biofilm bacteria is unique and distinct from those induced during normal healing or by planktonic bacteria alone. This review will examine the presence of inflammatory factors during normal healing and those induced by contaminating bacteria, and will discuss how these differences may ultimately lead to nonunion. Specifically, this review will focus on the Th1/Th2/Th17 type inflammatory responses and how shifts in the balance of these responses during infection can lead to both ineffective clearance and disruption of fracture healing. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1845-1854, 2017.

Phosphatidylcholine Coatings Deliver Local Antimicrobials and Reduce Infection in a Murine Model: A Preliminary Study

BACKGROUND

Phosphatidylcholine coatings have been shown to elute antibiotics for several days. A recently developed biofilm inhibitor, cis-2-decenoic acid (C2DA), has been shown to exhibit synergistic activity with several common antibiotics. This study aims to evaluate the effectiveness of C2DA and amikacin dual drug delivery from a phosphatidylcholine coating.

QUESTIONS/PURPOSES

(1) What are the in vitro elution profiles of amikacin and C2DA from phosphatidylcholine-coated coupons in incubated phosphate-buffered saline? (2) Does the presence of C2DA in eluate samples lower the amount of amikacin needed for bacterial inhibition in overnight bacterial turbidity assays? (3) Does addition of amikacin and C2DA result in decreased colony-forming units (CFUs) on wire implants and bone when compared with phosphatidylcholine coatings alone in a mouse model of periprosthetic joint infection?

METHODS

Effects of loading concentrations were assessed during 7-day in vitro elution studies for coatings containing all mixtures of 0%, 5%, 15%, and 25% wt of amikacin and C2DA (n = 4) through quantitative high-performance liquid chromatography concentration determination and plotting concentration eluted over time. Antimicrobial activity was assessed by overnight turbidity testing of elution study samples against Staphylococcus aureus or Pseudomonas aeruginosa. In vivo efficacy was assessed using phosphatidylcholine-coated wire implants in a murine (mouse) model of infection (n = 3). Wire implants were coated with phosphatidylcholine containing no antimicrobials, amikacin alone, C2DA alone, or amikacin and C2DA and then inserted into the intramedullary femur of each mouse and inoculated with S aureus. The number of viable bacterial colonies on the implant surface and in the surrounding bone was determined after 1 week with the goal of achieving complete bacterial clearance. Total viable CFU count and proportion of samples achieving complete clearance were compared between groups.

RESULTS

Elution samples showed a burst response of amikacin and C2DA for 1 to 2 days with C2DA release continuing at low levels through Day 4. All tested eluate samples inhibited P aeruginosa. Samples from coatings containing 25% amikacin or 15% amikacin and any amount of C2DA were able to inhibit S aureus formation, but all coatings with 5% amikacin or 15% amikacin but no C2DA were not inhibitory. All in vivo treatment groups achieved complete bacterial clearance on the wire implant, and the C2DA alone and amikacin alone coatings cleared all CFUs in bone (pin: phosphatidylcholine only one of three; amikacin three of three, C2DA three of three, amikacin + C2DA three of three, p = 0.04 [Fisher's exact test]; bone: coating only: zero of three; amikacin: three of three; C2DA; three of three; C2DA + amikacin: one of three; p = 0.03 [Fisher's exact test]).

CONCLUSIONS

Phosphatidylcholine coatings elute antimicrobials in vitro under infinite sink conditions for up to 4 days in phosphate-buffered saline and were able to reduce bacterial colonies in a preliminary in vivo model. Turbidity testing with eluate samples containing varying amounts of C2DA and amikacin agrees with previous studies showing synergy between them.

CLINICAL RELEVANCE

Used as an adjunctive to systemic therapy, C2DA-loaded phosphatidylcholine coatings have potential value as a prophylactic infection prevention measure. Future studies may include different antibiotics, animal studies with larger sample sizes and more controls, and advanced coating delivery methods.

Role of Systemic and Local Antibiotics in the Treatment of Open Fractures

The orthopedic community has learned much about the treatment of open fractures from the tremendous work of Ramon Gustilo, Michael Patzakis, and others; however, open fractures continue to be very difficult challenges. Type III open fractures continue to be associated with high infection rates. Some combination of systemic and local antibiotics may be most appropriate in these high-grade open fractures. Further research is still necessary in determining optimal systemic antibiotic regimens as well as the role of local antibiotics. Any new discoveries related to novel systemic antibiotics or local antibiotic carriers will need to be evaluated related to cost.

Infection after fracture osteosynthesis - Part II

In the first part of this article, we have discussed the pathogenesis, clinical presentation, diagnosis and classification of infection after fracture osteosynthesis with implants, termed here as osteosynthesis-associated infection (OAI). Prolonged antibiotic treatment is usually necessary. Implant retention and maintenance of fracture stability to allow for fracture healing in spite of infection are allowed for OAI. Depending on the severity of infection, status of fracture healing and host status, the treatment follows five common pathways. These are non-operative treatment, debridement with implant retention, conversion of fixation, implant removal and suppression therapy. The decision-making process leading to each treatment pathway and challenging scenarios is discussed in detail.

Time-Dependent Effectiveness of Locally Applied Vancomycin Powder in a Contaminated Traumatic Orthopaedic Wound Model

OBJECTIVES

To evaluate the effectiveness of locally applied vancomycin powder at different times postinfection in a contaminated traumatic animal model.

METHODS

This study used an established segmental defect rat femur model contaminated with Staphylococcus aureus UAMS-1 followed by treatment at 6 or 24 hours postinfection. Three treatments were evaluated: debridement and irrigation alone (control group) or in combination with either vancomycin powder or vancomycin-impregnated poly(methyl methacrylate) beads. Serum vancomycin levels were determined at scheduled time points over 14 days; bone, surrounding muscle, and implants were harvested for bacterial and inflammatory analyses.

RESULTS

Locally applied vancomycin powder and impregnated beads significantly reduced bacteria both within the bone and implant when treatment was performed at 6 hours. Delaying treatment to 24 hours significantly reduced the therapeutic efficacy of locally applied vancomycin of both groups. Serum vancomycin levels were detectable in all animals treated with vancomycin powder at 24 hours, but absorption was negligible from beads. At 14 days, vancomycin was detectable in the surrounding musculature of all animals and in serum of 20% of animals treated with vancomycin powder.

CONCLUSIONS

This study suggests that vancomycin powder is a promising adjunctive therapy for preventing infection in traumatic wounds when treatment is performed early. This time-dependent effectiveness of vancomycin powder is similar to that observed with systemic and other local delivery adjuncts, which is likely attributable to biofilm formation after contamination, conferring intrinsic recalcitrance to antimicrobials.

Antibiotic-loaded phosphatidylcholine inhibits staphylococcal bone infection

AIM: To test antibiotic-loaded coating for efficacy in reducing bacterial biofilm and development of osteomyelitis in an orthopaedic model of implant infection.

METHODS: Phosphatidylcholine coatings loaded with 25% vancomycin were applied to washed and sterilized titanium wires 20 mm in length. A 10 mm segment was removed from rabbit radius (total = 9; 5 coated, 4 uncoated), and the segment was injected with 1 × 10⁶ colony forming units (CFUs) of Staphylococcus aureus (UAMS-1 strain). Titanium wires were inserted through the intramedullary canal of the removed segment and into the proximal radial segment and the segment was placed back into the defect. After 7 d, limbs were removed, X-rayed, swabbed for tissue contamination. Wires were removed and processed to determine attached CFUs. Tissue was swabbed and streaked on agar plates to determine bacteriological score.

RESULTS: Antibiotic-loaded coatings resulted in significantly reduced biofilm formation (4.7 fold reduction in CFUs; P < 0.001) on titanium wires and reduced bacteriological score in surrounding tissue (4.0 ± 0 for uncoated, 1.25 ± 0.5 for coated; P = 0.01). Swelling and pus formation was evident in uncoated controls at the 7 d time point both visually and radiographically, but not in antibiotic-loaded coatings.

CONCLUSION: Active antibiotic was released from coated implants and significantly reduced signs of osteomyelitic symptoms. Implant coatings were well tolerated in bone. Further studies with additional control groups and longer time periods are warranted. Antibiotic-loaded phosphatidylcholine coatings applied at the point of care could prevent implant-associated infection in orthopaedic defects.

Combined local and systemic antibiotic delivery improves eradication of wound contamination: An animal experimental model of contaminated fracture

Systemic antibiotics reduce infection in open fractures. Local delivery of antibiotics can provide higher doses to wounds without toxic systemic effects. This study investigated the effect on infection of combining systemic with local antibiotics via polymethylmethacrylate (PMMA) beads or gel delivery. An established Staphylococcus aureus contaminated fracture model in rats was used. Wounds were debrided and irrigated six hours after contamination and animals assigned to one of three groups, all of which received systemic antibiotics. One group had local delivery via antibiotic gel, another PMMA beads and the control group received no local antibiotics. After two weeks, bacterial levels were quantified. Combined local and systemic antibiotics were superior to systemic antibiotics alone at reducing the quantity of bacteria recoverable from each group (p = 0.002 for gel; p = 0.032 for beads). There was no difference in the bacterial counts between bead and gel delivery (p = 0.62). These results suggest that local antibiotics augment the antimicrobial effect of systemic antibiotics. Although no significant difference was found between vehicles, gel delivery offers technical advantages with its biodegradable nature, ability to conform to wound shape and to deliver increased doses. Further study is required to see if the gel delivery system has a clinical role.

Are the leading drugs against Staphylococcus aureus really toxic to cartilage?

Many studies have shown that the toxic effects of local antibiotics on bone and cartilage limit orthopedic surgeons. In this study, we evaluated three antibacterial agents used locally to treat highly mortal and morbid diseases in the field of orthopedics, such as septic arthritis. Are vancomycin, teicoplanin, and linezolid, which are archenemies of Staphylococcus aureus, really toxic to chondrocytes? The purpose of the study was to investigate the effects of antibiotics, which are used against S. aureus, on human chondrocytes in vitro. Primary cell cultures obtained from gonarthrosis patients were divided into two main groups. One of these groups was designated as the control chondrocyte culture. The other group was divided into three subgroups, and each group was exposed to vancomycin, teicoplanin, or linezolid. Cell culture samples were characterized by immunophenotyping following incubation with the three different antibiotics. Before and after the agents were administered, the cultures were subjected to inverted and environmental scanning electron microscopy. The number of live cells and the proliferation rate were monitored with the MTT-assay. We found that vancomycin, teicoplanin, and linezolid do not have chondrotoxic effects. Vancomycin, teicoplanin, and linezolid had no chondrotoxic activity during in vitro culture, which supports the argument that these agents can safely be used in orthopedic surgery, especially against methicillin-resistant S. aureus agents.

Infected animal models for tissue engineering

Infection is one of the most common complications associated with medical interventions and implants. As tissue engineering strategies to replace missing or damaged tissue advance, the focus on prevention and treatment of concomitant infection has also begun to emerge as an important area of research. Because the in vivo environment is a complex interaction between host tissue, implanted materials, and native immune system that cannot be replicated in vitro, animal models of infection are integral in evaluating the safety and efficacy of experimental treatments for infection. In this review, considerations for selecting an animal model, established models of infection, and areas that require further model development are discussed with regard to cutaneous, fascial, and orthopedic infections.

Local antibiotic therapy strategies in orthopaedic trauma: Practical tips and tricks and review of the literature

The use of local antibiotics for the prevention of infection in the setting of open fractures and as part of the treatment of osteomyelitis is well established. Antibiotics are most commonly incorporated into polymethylmethacrylate (PMMA) cement, which can then be formed into beads, moulded to fit a bone defect or used to coat a guide wire or IM nail. Newer delivery vehicles and techniques are being evaluated to improve upon these methods. Many factors influence how local antibiotics are applied. Treatment strategies are challenging to standardise due to the variability of clinical presentations. The presence of hardware, upper versus lower extremity, healed versus non-healed fracture and quality of soft tissues overlying the affected bone, as well as patients' comorbidities all need to be considered. Despite the accepted use of local antibiotic therapy in orthopaedic trauma, high-quality evidence regarding the use of local antibiotics is lacking. Indications, techniques, dosages, types of antibiotics, elution properties and pharmacokinetics are poorly defined in the clinical setting. The purpose of our manuscript is to review current strategies and provide practical tips for local application of antibiotics in orthopaedic trauma. We focus on delivery vehicles, types of antibiotics, dosage recommendations when mixed with PMMA and indications.

Chitosan coatings to control release and target tissues for therapeutic delivery

The natural biopolymer chitosan has versatile applications in therapeutic delivery. Coating drug delivery matrices or biomaterials with chitosan offers several advantages in drug delivery, including control of drug release, slowing degradation rate and improving biocompatibility. Advanced uses of chitosan in coating form include targeting drug delivery vehicles to specific tissue as well as providing a stimulus-controlled release response. The present review summarizes the current applications of chitosan coatings in the context of different biomaterial delivery technologies, as well as future directions of chitosan coatings for drug delivery technologies under development.

Local bismuth thiols potentiate antibiotics and reduce infection in a contaminated open fracture model

OBJECTIVE

This proof-of-concept study tested the hypothesis that combining bismuth thiols (BTs) with systemic antibiotics will more effectively reduce infection in an animal model of contaminated open fracture than systemic antibiotics alone.

METHODS

An implant-stabilized segmental defect rat model was contaminated with Staphylococcus aureus and then treated with surgical debridement 6 hours after injury and 3 days of systemic cefazolin. A single dose of BTs suspended in a hydrogel was administered to the wound immediately after debridement. After 14 days, the bone and implant were harvested for microbiological analysis.

RESULTS

A single local dose of 0.05 mg of BT (MB-8-2), when combined with systemically administered cefazolin, decreased infection, without any noticeable local or systemic toxicity, from 60% to 10% (P = 0.002), with only 0.02% of the recovered bacteria quantity of the cefazolin-only group (P < 0.001). Higher doses were less effective and caused side-effects.

CONCLUSIONS

BTs administered locally to infected open fracture wounds at an appropriate dose potentiate the effect of systemically administered antibiotics and reduce infection rate and bacteria quantity associated with bone and orthopaedic implants. Local delivery of BTs is a promising strategy for increasing the efficacy of systemically administered antibiotics in preventing and treating infections of open fractures.

A versatile model of open-fracture infection : a contaminated segmental rat femur defect

Objectives

The purpose of this study was to refine an accepted contaminated rat femur defect model to result in an infection rate of approximately 50%. This threshold will allow examination of treatments aimed at reducing infection in open fractures with less risk of type II error.

Methods

Defects were created in the stablised femurs of anaethetised rats, contaminated with Staphylococcus aureus and then debrided and irrigated six hours later. After 14 days, the bone and implants were harvested for separate microbiological analysis. This basic model was developed in several studies by varying the quantity of bacterial inoculation, introducing various doses of systemic antibiotics with and without local antibiotics.

Results

The bacterial inoculation associated with a 50% infection rate was established as 1 × 10² colony forming units (CFU). With an initial bacterial inoculum of 1 × 10⁵ CFU, the dose of systemic antibiotics associated with 50% infection was 5 mg/Kg of cafazolin injected sub-cutaneously every 12 hours, starting at the time of the first debridment and continuing for 72 hours (seven doses). The systemic dose of cafazolin was lowered to 2 mg/Kg when antibiotic polymethyl methacrylate beads were used concurrently with the same amount of bacterial inoculation.

Conclusion

This model of open fracture infection has been further refined with potential for local and systemic antibiotics. This is a versatile model and with the concepts presented herein, it can be modified to evaluate various emerging therapies and concepts for open fractures.

Cite this article: Bone Joint Res 2014;3:187–92.