Negative pressure wound therapy reduces the effectiveness of traditional local antibiotic depot in a large complex musculoskeletal wound animal model

Open fractures of the lower leg: Outcome and risk-factor analysis for fracture-related infection and nonunion in a single center analysis of 187 fractures

BACKGROUND

Open fractures of the lower extremity have a higher risk of fracture-related infections (FRI) or nonunion. The purpose of this study was to identify risk factors for complications and evaluate outcomes.

METHODS

In this retrospective, single center study, we identified and included 187 patients with extraarticular and intraarticular fractures of the tibia or fibula between 2010 and 2018. Patient characteristics, treatment protocols, and complications were assessed, with a focus on soft tissue management and timing of wound closure versus fracture fixation. To analyze risk factors for FRI and nonunion, a univariate logistic regression model was used.

RESULTS

The open fractures included were 52 Gustilo-Anderson type-I (28 %), 99 type-II (53 %), and 36 type-III (19 %) fractures. The mean time from admission to first surgical intervention was 3.47 h (SD 1.4), with 122 (60 %) patients treated within 3 h and 182 (97 %) patients, within 6 h. During primary surgery, definitive fracture fixation was carried out in 112 (60 %) patients and wound closure in 122 (65 %) patients. FRI was reported in 27 (14 %) patients with the highest prevalence in type-III fractures (31 %). Secondary wound closure was associated with a significantly higher risk for FRI than primary wound closure (odds ratio [OR] = 3.3; p = 0.004). Nonunion was reported in 37 (20 %) patients. Significant risk factors for nonunion were FRI (OR=11.9, p < 0.001) and definitive fracture fixation before wound closure compared to fracture fixation and wound closure at the same time (OR = 8.2, p < 0.001). Gustilo-Anderson type-IIIb and -IIIc fractures had a significant lower FRI-free survival compared to other fractures. No patient underwent amputation during the follow-up.

CONCLUSION

Open fractures of the tibia and fibula are associated with a high risk of FRI and nonunion. FRI is the strongest predictor of nonunion in open fractures of the lower extremity. Primary wound closure and simultaneous definitive fracture fixation are protective even in higher Gustilo-Anderson fracture types and prevent complications. Early antibiotic therapy and surgical treatment are crucial, as evidenced by all cases receiving treatment within 6 h post trauma.

The antibiotic bead pouch - a useful technique for temporary soft tissue coverage, infection prevention and therapy in trauma surgery

Soft tissue defects resulting from trauma and musculoskeletal infections can complicate surgical treatment. Appropriate temporary coverage of these defects is essential to achieve the best outcomes for necessary plastic soft tissue defect reconstruction. The antibiotic bead pouch technique is a reasonable surgical approach for managing temporary soft tissue defects following adequate surgical debridement. This technique involves the use of small diameter antibiotic-loaded bone cement beads to fill the dead space created by debridement. By applying antibiotics to the bone cement and covering the beads with an artificial skin graft, high local dosages of antibiotics can be achieved, resulting in the creation of a sterile wound that offers the best starting position for soft tissue and bone defect reconstruction. This narrative review describes the rationale for using this technique, including its advantages and disadvantages, as well as pearls and pitfalls associated with its use in daily practice. In addition, the article provides a comprehensive overview of the literature that has been published since the technique was introduced in surgical practice.

Antibiotic bead pouch versus negative pressure wound therapy at initial management of AO/OTA 42 type IIIB open tibia fracture may reduce fracture related infection: A retrospective analysis of 113 patients

INTRODUCTION

Fracture related infection (FRI) may be a devastating complication of open tibial shaft fractures. We sought to determine if antibiotic bead pouch, negative pressure wound therapy, or negative pressure wound therapy over antibiotic beads as the initial coverage method for type IIIB open tibial shaft fractures is associated with risk of FRI.

PATIENTS AND METHODS

Retrospective cohort study with radiograph and chart review of patients aged ≥16 years with isolated, displaced, extra-articular, Gustilo-Anderson type IIIB open diaphyseal AO/OTA 42 tibial fractures requiring rotational or free tissue transfer for soft tissue coverage at one Level 1 trauma center between 2007 and 2020. An association of dressing applied at the first surgical debridement (application of antibiotic bead pouch, negative pressure wound therapy, or combined therapy) with a primary outcome of FRI requiring debridement or amputation was analyzed by multivariable logistic regression considering demographic, injury, and treatment characteristics.

RESULTS

113 patients met eligibility criteria. Median follow-up was 33 months (interquartile range 5-88). 41 patients were initially treated with NPWT, 59 with ABP, and 13 with ABP+NPWT at the initial surgical debridement. 39 (35%) underwent subsequent debridement or amputation for FRI. One amputation occurred in the ABP group for refractory deep surgical site infection (p = 0.630). Initial wound management with an antibiotic bead pouch versus either negative pressure wound therapy alone or negative pressure wound therapy combined with an antibiotic bead pouch was associated with lower odds of debridement or amputation for FRI (β = -1.08, 95% CI -2.00 to -0.17, p = 0.02).

CONCLUSIONS

In our retrospective analysis, antibiotic bead pouch for initial coverage of type IIIB open tibial shaft fractures requiring flap coverage was associated with a lower risk of FRI requiring debridement or amputation than negative pressure wound therapy applied with or without antibiotic beads. A prospective clinical trial is warranted.

Negative Pressure Wound Therapy for Extremity Open Wound Management: A Review of the Literature

Negative pressure wound therapy (NPWT) with reticulated open cell foam is used commonly in orthopaedic trauma, particularly in the management of complex open fracture wounds. This article reviews the literature to date regarding this adjunctive treatment, particularly in regard to removal of infectious material, temporary management of wounds pending soft tissue reconstruction, combat wounds, and over split-thickness skin grafts. Mechanism of action is also reviewed, including stabilization of the wound environment, edema control, macrodeformation, and microdeformation effects. Use of NPWT as an adjunct in management of open fractures along with operative debridement, systemic antibiotics, and early soft tissue reconstruction are the highest yield interventions for managing open fracture wounds with infection. NPWT as an adjunct therapy in the protocol for open fractures seems to add additional clinical benefit for patients with severe open fracture wounds not amenable to primary, immediate closure.

Open tibial fractures: An overview

Open tibial fractures are complex injuries with multifactorial outcomes and variable prognosis. The close proximity of the tibia to the skin makes it prone to extensive soft tissue damage and subsequent detrimental complications, such as infection and non-union. Thus, they were historically associated with high rates of amputation, sepsis, or even death. The advancement of surgical instruments and techniques, along the emergence of evidence-based guidance, have resulted in a significant reduction in complications. Peculiarly though, modern management strategies have a strong foundation in practices described in the ancient times. Nevertheless, post-operative complications are still a challenge in the management of open tibial fractures. Efforts are actively being made to refine the surgical approaches used, while noteworthy is the emergence of the Orthoplastic approach. The aim of this review is to summarise and discuss the historical perspective of the management of open tibial fractures, their epidemiology and classification, up-to-date principles of surgical management and outcomes following injury.

Modern Principles in the Acute Surgical Management of Open Distal Tibial Fractures

Over the past two decades, management of open distal tibial fractures has evolved such that a staged approach, with external fixation and débridement during the index procedure, followed by definitive fixation and wound closure at a later date, is often considered the standard of care. Although definitive treatment of these complex injuries is often done by a multidisciplinary team of surgeons well versed in periarticular fracture repair and soft-tissue coverage in the distal extremity, the on-call orthopaedic surgeon doing the index procedure must understand the principles and rationale of the staged treatment algorithm to avoid compromising definitive treatment options and ensure the best possible patient outcome. The mechanism of injury, neurovascular status, size and location of soft-tissue injury, fracture pattern, and concomitant injuries in the polytraumatized patient should direct the treatment plan and anticipated outcomes. This review focuses on evaluation and management of these complex injuries with an emphasis on early aggressive débridement, principles of initial fracture fixation, and modern options for soft-tissue coverage, including local and free tissue transfer.

Management of Wounds With Orthopedic Fixation Hardware Using Negative-Pressure Wound Therapy With Instillation and Dwell

SUMMARY

Negative-pressure wound therapy with instillation and dwell (NPWTi-d) is an option for management of wounds with exposed orthopedic fixation hardware. The mechanical effect of the negative-pressure therapy works to contract the wound edges, and the instillation of solution and its subsequent removal help remove infectious material. NPWTi-d also promotes robust granulation tissue formation. In this article, we discuss the science behind NPWTi-d and its role in the treatment of wounds with indwelling orthopedic fixation hardware.

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.

Open fractures with soft-tissue loss: Coverage options and timing of surgery

Open fractures with soft-tissue loss remain challenging injuries to treat. These often high-energy fractures are at a higher risk of delayed healing and at much higher risk of infection than open fractures with less significant soft-tissue injury. The initial management of the open wound, flap coverage options, and the timing of definitive coverage all remain areas of controversy, which will be discussed in this article.

Wartime Soft Tissue Coverage Techniques for the Deployed Surgeon

BACKGROUND

Since the start of the conflict in the Middle East in 2001, military orthopedic surgeons have faced complex orthopedic injuries including high-energy soft tissue wounds, traumatic amputations, and open fractures. Although orthopedic surgeons are well trained in the management of osseous injuries, the treatment of soft tissue injuries can be technically challenging and unfamiliar. Early washout, debridement of devitalized tissue, external fixation of bony injuries, and antibiotic therapy remain the foundation of early wound management. However, these unique extremity injuries have no standard plan of care, and definitive treatment options continue to evolve. The following report highlights the typical cases seen in the wartime setting and offers possible solutions for the associated soft tissue injuries.

METHODS

A single orthopedic surgeon at a Role 3 combat support hospital performed all cases in this series. This study is a report of the cases that the orthopedic surgeon encountered while deployed and the various techniques that can be used to manage the complex wounds seen in a deployed setting.

FINDINGS

Twelve patients were included in this report and the data are shown. Of the 12 patients, 6 were injured by an improvised explosive device (IED), 4 were injured by a high-velocity gunshot wound (HVGSW), 1 was injured by a gunshot wound (GSW), and 1 was injured in an auto versus pedestrian motor vehicle crash. The wound sizes ranged from 10 to 300 cm2. All patients required more than one irrigation and debridement before wound closure. There was a successful outcome in 11 of the 12 patients. The only patient without a known successful outcome was lost to follow up. Six patients were treated with split thickness skin graft (STSG) alone. Four patients were treated with STSG plus an additional means of coverage. One patient was treated with a random flap and one patient was treated with a full thickness skin graft. Integra was used in two of the patients. Each of the patients in whom integra was used had exposed bone and had a successful outcome with respect to tissue coverage.

DISCUSSION

This study details different soft tissue coverage techniques that must be learned and possibly employed by the deployed surgeon. Limitations of this study include its retrospective nature and the selected sampling of cases. At initial presentation, the management of war wounds secondary to high-velocity gunshot wounds and improvised explosive devices can be quite daunting. Adhering to firm surgical principles of thorough and meticulous debridement is the foundation of later soft tissue reconstructive options. Once the tissue is deemed clear of infection and contamination, there are myriad treatment options utilizing flaps, synthetic materials, and skin grafting. These are relatively straightforward techniques that the general orthopedic surgeon can utilize while deployed in a combat setting. In the end, it is critical for deployed surgeons to learn multiple techniques to provide definitive soft tissue coverage in a wartime theater.

An Effective Negative Pressure Wound Therapy-Compatible Local Antibiotic Delivery Device

OBJECTIVES

The current clinical standard for local antibiotic depot is polymethylmethacrylate (PMMA) beads. Unfortunately, these are not ideal and negative pressure wound therapy (NPWT) reduces their limited effectiveness. Recently, a chitosan sponge has been shown to be an effective carrier of antibiotics. Because it acts as a delivery vehicle with increased wound contact area instead of an antibiotic depot, it may be more effective. The objectives of this study were to determine if (1) a chitosan sponge would be more effective than PMMA beads as a local antibiotic delivery device and (2) the chitosan sponge remains an effective method of delivery when used in conjunction with NPWT.

METHODS

Contaminated musculoskeletal wounds were created on the proximal tibia of goats; the animals were assigned to 1 of 4 groups (bead pouch, beads with NPWT, sponge pouch, and sponge with NPWT). The animals were survived for 48 hours, and the bacteria in the wound were quantified. The antibiotic levels in the blood and within the NPWT canisters were measured throughout the study period.

RESULTS

After treatment, there were significantly fewer bacteria in wounds treated with antibiotic chitosan sponge delivery than antibiotic PMMA bead depot (P < 0.05), and NPWT did not reduce the effectiveness of the chitosan sponge even though large amounts of vancomycin was found in the canisters. The peak serum levels of vancomycin were well below what is considered safe levels.

CONCLUSIONS

Antibiotic delivery to the wound using a chitosan sponge is compatible with NPWT and is more effective than PMMA antibiotic depot. The chitosan sponge works in conjunction with NPWT and may improve the outcomes of open fracture wounds.

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.

Local Antibiotic Therapy to Reduce Infection After Operative Treatment of Fractures at High Risk of Infection: A Multicenter, Randomized, Controlled Trial (VANCO Study)

A number of clinical studies in the spine literature suggest that the use of local vancomycin powder may substantially reduce surgical site infections (SSIs). These studies are primarily retrospective and observational and few focus on orthopaedic trauma patients. This study is a phase III, prospective, randomized, clinical trial to assess the efficacy of locally administered vancomycin powder in the prevention of SSI after fracture surgery. The primary goal of the VANCO Study is to compare the proportion of deep SSI 6 months after fracture fixation surgery. A secondary objective is to compare species and antibacterial susceptibilities among study patients who develop SSI. An additional objective is to build and validate a risk prediction model for the development of SSI. The study population consists of patients aged 18-80 years with tibial plateau or pilon (tibial plafond) fractures, at higher risk of infection, and definitively treated with plate and screw fixation. Participants are block randomized (within center) in a 1:1 ratio to either treatment group (local vancomycin powder up to a maximum dose of 1000 mg, placed immediately before wound closure) or control group (standard of care) for each study injury location, and return to the clinic for evaluations at 2 weeks, 3 months, and 6 months after fixation. The targeted sample size for the study is 500 fractures per study arm. This study should provide important information regarding the use of local vancomycin powder during the definitive treatment of lower extremity fractures and has the potential to significantly reduce the incidence of infection after orthopaedic trauma.

Complex Foot Injury: Early and Definite Management

Complex foot injuries occur infrequently, but are life-changing events. They often present with other injuries as the result of a high-energy trauma. After initial stabilization, early assessment should be regarding salvagability. All treatment strategies are intensive. The initial treatment includes prevention of progression ischemia/necrosis, prevention of infection, and considering salvage or amputation. Definitive treatment for salvage includes anatomic reconstruction with stable internal fixation and early soft tissue coverage followed by aggressive rehabilitation. Prognosis after complex injuries is hard to predict. The various stages of the treatment are reviewed and recommendations are made.

A comparative study of negative pressure wound therapy with and without instillation of saline on wound healing

OBJECTIVE

Negative pressure wound therapy (NPWT) has become an established treatment of traumatic and infected wounds. Negative pressure wound therapy with instillation (NPWTi) is a further development that combines the conventional NPWT with instillation of different fluids which continuously administer therapeutic reagents to the wound. The aim of this study was to compare the impact of additional saline instillation in NPWTi to NPWT alone.

METHOD

Between January and July 2014, consecutive patients with acute wounds of the lower limb were treated with NPWTi with saline instillation. The number of revision surgeries, length of hospital stay, and duration of treatment until final healing were recorded and compared with matched patients undergoing NPWT without instillation.

RESULTS

There were 10 patients recruited with 10 matched controls examined restrospectivley. Patients who received NPWTi were found to have decreased time of hospitalisation (21.5 versus 26.5 days, p=0.43), and accelerated wound healing (9.0 versus 12.5 days, p=0.36) than patients who received NPWT. However, the difference in the outcomes of the patients who received NPWTi and patients who received NPWT was not found to be statisticallly significant.

CONCLUSION

NPWTi with instillation of saline is a promising method and its effectiveness needs to be tested in a randomised controlled trial compared with NPWT alone.

DECLARATION OF INTEREST

This study obtained support by KCI (Wiebsaden, Germany) for the surgical material.

Lower Extremity Limb Salvage: Lessons Learned From 14 Years at War

American survivability during the current conflicts in Iraq and Afghanistan continues to improve, though the rate of extremity injury remains quite high. The decision to proceed with amputation versus limb salvage remains controversial. Exposure to combat wound with severe high-energy lower extremity trauma during the previous 14 years at war has incited important advances in limb salvage technique and rehabilitation.

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.

Infected hardware after surgical stabilization of rib fractures: Outcomes and management experience

BACKGROUND

Surgical stabilization of rib fracture (SSRF) is increasingly used for treatment of rib fractures. There are few data on the incidence, risk factors, outcomes, and optimal management strategy for hardware infection in these patients. We aimed to develop and propose a management algorithm to help others treat this potentially morbid complication.

METHODS

We retrospectively searched a prospectively collected rib fracture database for the records of all patients who underwent SSRF from August 2009 through March 2014 at our institution. We then analyzed for the subsequent development of hardware infection among these patients. Standard descriptive analyses were performed.

RESULTS

Among 122 patients who underwent SSRF, most (73%) were men; the mean (SD) age was 59.5 (16.4) years, and median (interquartile range [IQR]) Injury Severity Score was 17 (13-22). The median number of rib fractures was 7 (5-9) and 48% of the patients had flail chest. Mortality at 30 days was 0.8%. Five patients (4.1%) had a hardware infection on mean (SD) postoperative day 12.0 (6.6). Median Injury Severity Score (17 [range, 13-42]) and hospital length of stay (9 days [6-37 days]) in these patients were similar to the values for those without infection (17 days [range, 13-22 days] and 9 days [6-12 days], respectively). Patients with infection underwent a median (IQR) of 2 (range, 2-3) additional operations, which included wound debridement (n = 5), negative-pressure wound therapy (n = 3), and antibiotic beads (n = 4). Hardware was removed in 3 patients at 140, 190, and 192 days after index operation. Cultures grew only gram-positive organisms. No patients required reintervention after hardware removal, and all achieved bony union and were taking no narcotics or antibiotics at the latest follow-up.

CONCLUSIONS

Although uncommon, hardware infection after SSRF carries considerable morbidity. With the use of an aggressive multimodal management strategy, however, bony union and favorable long-term outcomes can be achieved.

LEVEL OF EVIDENCE

Therapeutic study, level V.

New Is Old, and Old Is New: Recent Advances in Antibiotic-Based, Antibiotic-Free and Ethnomedical Treatments against Methicillin-Resistant Staphylococcus aureus Wound Infections

Staphylococcus aureus is the most common pathogen of wound infections. Thus far, methicillin-resistant S. aureus (MRSA) has become the major causative agent in wound infections, especially for nosocomial infections. MRSA infections are seldom eradicated by routine antimicrobial therapies. More concerning, some strains have become resistant to the newest antibiotics of last resort. Furthermore, horizontal transfer of a polymyxin resistance gene, mcr-1, has been identified in Enterobacteriaceae, by which resistance to the last group of antibiotics will likely spread rapidly. The worst-case scenario, "a return to the pre-antibiotic era", is likely in sight. A perpetual goal for antibiotic research is the discovery of an antibiotic that lacks resistance potential, such as the recent discovery of teixobactin. However, when considering the issue from an ecological and evolutionary standpoint, it is evident that it is insufficient to solve the antibiotic dilemma through the use of antibiotics themselves. In this review, we summarized recent advances in antibiotic-based, antibiotic-free and ethnomedical treatments against MRSA wound infections to identify new clues to solve the antibiotic dilemma. One potential solution is to use ethnomedical drugs topically. Some ethnomedical drugs have been demonstrated to be effective antimicrobials against MRSA. A decline in antibiotic resistance can therefore be expected, as has been demonstrated when antibiotic-free treatments were used to limit the use of antibiotics. It is also anticipated that these drugs will have low resistance potential, although there is only minimal evidence to support this claim to date. More clinical trials and animal tests should be conducted on this topic.

Applications of Local Antibiotics in Orthopedic Trauma

Local antibiotics have a role in orthopedic trauma for both infection prophylaxis and treatment. They provide the advantage of high local antibiotic concentration without excessive systemic levels. Nonabsorbable polymethylmethacrylate (PMMA) is a popular antibiotic carrier, but absorbable options including bone graft, bone graft substitutes, and polymers have gained acceptance. Simple aqueous antibiotic solutions continue to be investigated and appear to be clinically effective. For established infections, such as osteomyelitis, a combination of surgical debridement with local and systemic antibiotics seems to represent the most effective treatment at this time. Further investigation of more effective local antibiotic utilization is ongoing.

Soft tissue and wound management of blast injuries

The management of blast-related soft tissue wounds requires a comprehensive surgical approach that acknowledges extensive zones of injury and the likelihood of massive contamination. The experiences of military surgeons during the last decade of war have significantly enhanced current understandings of the optimal means of mitigating infectious complications, the timing of soft tissue coverage attempts, and the reconstructive options available for definitive wound management. Early administration of antibiotics in the setting of soft tissue wounds and associated open fractures is the single most important aspect of open fracture care. Both civilian and military reports have elucidated the incidence of invasive fungal infection in the setting of high-energy injuries with significant wound burdens, and novel treatment protocols have emerged. The type of reconstruction is predicated upon the zone of injury and location of the soft tissue defect. Multiple reports of military cohorts have suggested the equivalency of various techniques and types of soft tissue coverage. Longer-term follow-up will inform future perspectives on the durability of these surgical approaches.

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.

A pre-clinical evaluation of silver, iodine and Manuka honey based dressings in a model of traumatic extremity wounds contaminated with Staphylococcus aureus

Prevention of extremity war wound infection remains a clinical challenge. Staphylococcus aureus is the most common pathogen in delayed infection. We hypothesised that choice of wound dressings may affect bacterial burden over 7 days reflecting the current practice of delayed primary closure of wounds within this timeframe. A randomised controlled trial of 3 commercially available dressings (Inadine(®) (Johnson & Johnson, NJ, USA), Acticoat(®) (Smith & Nephew, Hull, UK), Activon Tulle (Advancis Medical, Nottingham, UK)) was conducted in a rabbit model of contaminated forelimb muscle injury. A positive control group treated with antibiotics was included. Groups were compared to a saline soaked gauze control. The primary outcome was a statistically significant reduction (p < 0.05) in tissue S. aureus at 7 days post-injury. Secondary outcome measurements included bacteraemias, observational data, whole blood determination, ELISA for plasma biomarkers, PCR array analysis of wound healing gene expression and muscle/lymph node histopathology. Antibiotic, Inadine and Acticoat groups had statistically significant lower bacterial counts (mean 7.13 [95% CI 0.00-96.31]×10(2); 1.66 [0.94-2.58]×10(5); 8.86 [0.00-53.35]×10(4)cfu/g, respectively) and Activon Tulle group had significantly higher counts (2.82 [0.98-5.61]×10(6)cfu/g) than saline soaked gauze control (7.58 [1.65-17.83]×10(5)cfu/g). There were no bacteraemias or significant differences in observational data or whole blood determination. There were no significant differences in muscle/loss or pathology and lymph node cross-sectional area or morphology. There were some significant differences between treatment groups in the plasma cytokines IL-4, TNFα and MCP-1 in comparison to the control. PCR array data demonstrated more general changes in gene expression in the muscle tissue from the Activon Tulle group than the Inadine or Acticoat dressings with a limited number of genes showing significantly altered expression compared to control. This study has demonstrated that both Acticoat(®) and Inadine(®) dressings can reduce the bacteria burden in a heavily contaminated soft tissue wound and so they may offer utility in the clinical setting particularly where surgical treatment is delayed.

Negative pressure wound therapy - a review of its uses in orthopaedic trauma

The use of Negative Pressure Wound Therapy (NPWT) for complex and large wounds has increased in popularity over the past decade. Modern NPWT systems consisting of an open pore foam sponge, adhesive dressing and a vacuum pump producing negative pressure have been used as an adjunct to surgical debridement to treat tissue defects around open fractures and chronic, contaminated wounds. Other uses include supporting skin grafts and protecting wounds at risk of breaking down. This review outlines the current and emerging indications for negative pressure wound therapy in Orthopaedic trauma and the existing preclinical and clinical evidence base for its use.

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

OBJECTIVES

Local delivery allows a high concentration of antibiotics to be achieved in the wound while avoiding the side effects and cost of systemic administration. Beads molded from polymethylmethacrylate cement are commonly used for local antibiotic delivery but are not ideal. The purpose of this study was to determine whether a bioabsorbable gel delivering vancomycin and gentamicin is more effective in reducing infection than beads delivering vancomycin and tobramycin.

METHODS

This study used a segmental defect rat model contaminated with Staphylococcus aureus and treated with clinically relevant local antibiotic doses, delivered by gel or beads. In the gel group, 1 mL of gel containing gentamicin and vancomycin was spread throughout the wound. In the bead group, four 3-mm beads containing tobramycin and vancomycin were placed in the wound, 2 in the defect and 2 in the adjacent tissue envelope, there was also a control group that received no antibiotic treatment. After 14 days, bone and hardware was harvested for separate microbiological analysis.

RESULTS

There was a significantly lower infection rate in groups treated with antibiotics delivered by gel compared with those treated with either antibiotic beads or no antibiotics at all (P < 0.001). Quantitative cultures also demonstrate significantly less bacteria in the wounds treated with the gel than in the control or bead groups (P ≤ 0.004).

CONCLUSIONS

These results suggest that antibiotic delivery by a gel is superior to beads. The authors propose that antibiotic depot by polymethylmethacrylate antibiotic beads is less effective because this method has to rely on diffusion of the antibiotic from the high concentration close to the beads to all regions of the wound.

Infection and combat injuries

Blast and ballistic weapons used on the battlefield cause devastating injuries rarely seen outside armed conflict. These extremely high-energy injuries predominantly affect the limbs and are usually heavily contaminated with soil, foliage, clothing and even tissue from other casualties. Once life-threatening haemorrhage has been addressed, the military surgeon’s priority is to control infection.

Combining historical knowledge from previous conflicts with more recent experience has resulted in a systematic approach to these injuries. Urgent debridement of necrotic and severely contaminated tissue, irrigation and local and systemic antibiotics are the basis of management. These principles have resulted in successful healing of previously unsurvivable wounds. Healthy tissue must be retained for future reconstruction, vulnerable but viable tissue protected to allow survival and avascular tissue removed with all contamination.

While recent technological and scientific advances have offered some advantages, they must be judged in the context of a hard-won historical knowledge of these wounds. This approach is applicable to comparable civilian injury patterns. One of the few potential benefits of war is the associated improvement in our understanding of treating the severely injured; for this positive effect to be realised these experiences must be shared.