A clinical perspective on musculoskeletal infection treatment strategies and challenges

Osteomyelitis in complicated bones: the role of FDG PET/CT

Osteomyelitis in infections encompasses heterogeneous group of condition that frequently have high morbidity and comes at a huge cost to healthcare system. Accurate and early diagnosis is important for the proper management of the condition. FDG PET/CT has been found useful in the osteomyelitis of complicated bones, including prosthetic joint infections, fracture related infections and sternal wound infections. The altered anatomy and the replacement of marrow in some cases of metallic implant makes the use of anatomic-based methods less optimal. FDG PET/CT has been found to be useful under these circumstances, however, it also has its own limitation of lack of specificity especially due to inflammation. Recent meta-analysis of the role of FDG PET/CT in complicated osteomyelitis have result in the validation defined the indications for its use. This has led to the publication of best use criteria and recommendations of by joint committees of major nuclear medicine societies.

Multidisciplinary Teams in Musculoskeletal Infection - From a Pathologist's Perspective

Multidisciplinary team (MDT) meetings have emerged as a promising approach for the treatment of cancer patients. These meetings involve a team of healthcare professionals from different disciplines working together to develop a holistic, patient-centered treatment. Although MDT meetings are well established in oncology, they play a minor role in other diseases. Recent evidence suggests that the implementation of MDT meetings can improve patient outcomes in musculoskeletal infections. The aim of this retrospective, observational study was to present the agenda of our multidisciplinary limb board including live microscopy with a special focus on the pathologist's role. The descriptive analysis of the limb board included 66 cases receiving live microscopy at the meeting and a total of 124 histopathological findings and 181 stainings. We could elucidate that pathologists seem to play an important role especially in clarifying the correct diagnosis. In 80.3 % of the findings, the pathologist specified the clinical diagnosis of the requesting physician leading to a consensus-based treatment plan for each patient. The implementation of MDT meetings including live microscopy in patients with musculoskeletal infections holds potential benefits, such as improved communication, scientific collaboration, and raising clinicians' awareness and understanding of histopathology findings. However, potential challenges, such as organizational effort and technical prerequisites should be considered.

Transmission and microevolution of methicillin-resistant Staphylococcus aureus ST88 strain among patients, healthcare workers, and household contacts at a trauma and orthopedic ward

Background

Surgical sites infections (SSIs) caused by Methicillin-resistant Staphylococcus aureus (MRSA) constitute a major clinical problem. Understanding the transmission mode of MRSA is important for its prevention and control.

Aim

We investigated the transmission mode of a MRSA outbreak in a trauma and orthopedic hospital ward.

Methods

Clinical data were collected from patients (n = 9) with MRSA infection in a trauma and orthopedic ward from January 1, 2015 to December 31, 2019. The wards (n = 18), patients (n = 48), medical staff (n = 23), and their households (n = 5) were screened for MRSA. The transmission mode of MRSA isolates was investigated using next-generation sequencing and phylogenetic analyses. The resistance genes, plasmids, and single-nucleotide variants of the isolates were analyzed to evaluate microevolution of MRSA isolates causing SSIs. The MRSA colonization-positive doctor was asked to suspend his medical activities to stop MRSA spread.

Findings

Nine MRSA infected patients were investigated, of which three patients were diagnosed with SSI and had prolonged hospitalization due to the persistent MRSA infection. After screening, MRSA isolates were not detected in environmental samples. The surgeon in charge of the patients with SSI caused by MRSA and his son were positive for MRSA colonization. The MRSA from the son was closely related to the isolates detected in MRSA-induced SSIs patients with 8-9 single-nucleotide variants, while ST88-MRSA isolates with three different spa types were detected in the surgeon's nasal cavity. Comparative genomic analysis showed that ST88-MRSA isolates acquired mutations in genes related to cell wall synthesis, colonization, metabolism, and virulence during their transmission. Suspending the medical activity of this surgeon interrupted the spread of MRSA infection in this ward.

Conclusion

Community-associated MRSA clones can invade hospitals and cause severe postoperative nosocomial infections. Further MRSA surveillance in the households of health workers may prevent the transition of MRSA from colonization to infection.

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.

Characterization and Antibiofilm Activity of Mannitol-Chitosan-Blended Paste for Local Antibiotic Delivery System

Mannitol, a polyalcohol bacterial metabolite, has been shown to activate dormant persister cells within bacterial biofilm. This study sought to evaluate an injectable blend of mannitol, chitosan, and polyethylene glycol for delivery of antibiotics and mannitol for eradication of Staphylococcal biofilm. Mannitol blends were injectable and had decreased dissociation and degradation in the enzyme lysozyme compared to blends without mannitol. Vancomycin and amikacin eluted in a burst response, with active concentrations extended to seven days compared to five days for blends without mannitol. Mannitol eluted from the paste in a burst the first day and continued through Day 4. Eluates from the mannitol pastes with and without antibiotics decreased viability of established S. aureus biofilm by up to 95.5% compared to blends without mannitol, which only decreased biofilm when loaded with antibiotics. Cytocompatibility tests indicated no adverse effects on viability of fibroblasts. In vivo evaluation of inflammatory response revealed mannitol blends scored within the 2–4 range at Week 1 (2.6 ± 1.1) and at Week 4 (3.0 ± 0.8), indicative of moderate inflammation and comparable to non-mannitol pastes (p = 0.065). Clinically, this paste could be loaded with clinician-selected antibiotics and used as an adjunctive therapy for musculoskeletal infection prevention and treatment.

Reverse shoulder arthroplasty has a higher risk of revision due to infection than anatomical shoulder arthroplasty

Aims

The aim of this study was to use national registry database information to estimate cumulative rates and relative risk of revision due to infection after reverse shoulder arthroplasty.

Patients and Methods

We included 17 730 primary shoulder arthroplasties recorded between 2004 and 2013 in The Nordic Arthroplasty Register Association (NARA) data set. With the Kaplan–Meier method, we illustrated the ten-year cumulative rates of revision due to infection and with the Cox regression model, we reported the hazard ratios as a measure of the relative risk of revision due to infection.

Results

In all, 188 revisions were reported due to infection during a mean follow-up of three years and nine months. The ten-year cumulative rate of revision due to infection was 1.4% overall, but 3.1% for reverse shoulder arthroplasties and 8.0% for reverse shoulder arthroplasties in men. Reverse shoulder arthroplasties were associated with an increased risk of revision due to infection also when adjusted for sex, age, primary diagnosis, and year of surgery (relative risk 2.41 (95% confidence interval 1.26 to 5.59); p = 0.001).

Conclusion

The overall incidence of revision due to infection was low. The increased risk in reverse shoulder arthroplasty must be borne in mind, especially when offering it to men. Cite this article: Bone Joint J 2019;101-B:702–707.

Proceedings from the 2018 International Consensus Meeting on Orthopedic Infections: prevention of periprosthetic shoulder infection

The Second International Consensus Meeting on Orthopedic Infections was held in Philadelphia, Pennsylvania, in July 2018. Over 800 international experts from all 9 subspecialties of orthopedic surgery and allied fields of infectious disease, microbiology, and epidemiology were assembled to form a consensus workgroup. The following proceedings on the prevention of periprosthetic shoulder infection come from 16 questions evaluated by delegates from the shoulder section.

Assessment and management of infected total knee replacements

Infection following total knee replacement surgery is a challenging and devastating complication. Clinical assessment including history, examination, radiographs, blood tests and knee aspirations helps to establish the diagnosis. Revision surgery is typically required to eradicate infection and restore function. This has traditionally been performed through two-stage revision surgery, although single-stage revision surgery is gaining popularity with comparable results in carefully selected patients. This article reviews the clinical assessment and principles of surgical management of infected total knee replacements.

Infected total hip replacements: assessment and management

Infected total hip replacements pose a diagnostic and management challenge. Careful history, clinical examination, blood tests, plain radiographs and hip aspiration are all part of the clinical assessment. International consensus on establishing the diagnosis helps surgeons to formulate management plans. Management strategies include debridement and prosthesis retention, single-stage revision, two-stage revision, suppressive antibiotic treatment and excision arthroplasty. This article reviews the clinical assessment, diagnosis, principles of surgical management and outcomes of revision surgery of infected total hip replacements.

Positive Blood Cultures in Periprosthetic Joint Infection Decrease Rate of Treatment Success

BACKGROUND

Blood cultures are often obtained at the time of periprosthetic joint infection (PJI) diagnosis yet they are not considered part of the diagnostic criteria and the effects of a positive result on surgical outcome are unknown. The purposes of this study are to characterize the use of blood cultures when diagnosing PJI and to determine the association of positive blood cultures with PJI treatment success.

METHODS

A retrospective chart review on 320 patients surgically treated for primary hip and knee PJIs was performed from 2006-2013 at 2 academic medical centers with minimum 12-month follow-up. Treatment success was defined by the Delphi criteria. Multiple logistic regression analysis was performed to identify variables associated with treatment success.

RESULTS

Blood cultures were obtained from 53.1% of PJI patients (170/320) at the time of diagnosis. The same organism was identified 86.0% of the time in blood culture and operative culture. Patients with positive blood cultures at the time of PJI diagnosis had elevated synovial white blood cell count (98,979, P = .012), elevated serum C-reactive protein (24.2 mg/L, P < .001), and decreased treatment success (65.1%) compared with those with a negative blood culture (85.0%) and those without a blood culture (82.7%, P = .013). A positive blood culture remained associated with decreased PJI treatment success using multiple logistic regression analysis.

CONCLUSION

The presence of positive blood cultures at the time of PJI diagnosis decreased PJI treatment success. Further prospective studies are needed to help identify the role of blood cultures in the work up of PJI and treatment optimization in these patients.

Periprosthetic shoulder infection: an overview

Periprosthetic shoulder infection (PSI) is rare but potentially devastating. The rate of PSI is increased in cases of revision procedures, reverse shoulder implants and co-morbidities. One specific type of PSI is the occurrence of low-grade infections caused by non-suppurative bacteria such as Propionibacterium acnes or Staphylococcus epidemermidis.

Success of treatment depends on micro-organism identification, appropriate surgical procedures and antibiotic administration efficiency. Post-operative early PSI can be treated with simple debridement, while chronic PSI requires a one- or two-stage revision procedure. Indication for one-time exchange is based on pre-operative identification of a causative agent. Resection arthroplasty remains an option for low-demand patients or recalcitrant infection.

Cite this article: EFORT Open Rev 2017;2:104-109. DOI: 10.1302/2058-5241.2.160023

Osteomyelitis: Recent advances in pathophysiology and therapeutic strategies

This review article summarizes the recent advances in pathogenic mechanisms and novel therapeutic strategies for osteomyelitis, covering both periprosthetic joint infections and fracture-associated bone infections. A better understanding of the pathophysiology including the mechanisms for biofilm formation has led to new therapeutic strategies for this devastating disease. Research on novel local delivery materials with appropriate mechanical properties, lower exothermicity, controlled release of antibiotics, and absorbable scaffolding for bone regeneration is progressing rapidly. Emerging strategies for prevention, early diagnosis of low-grade infections, and innovative treatments of osteomyelitis such as biofilm disruptors and immunotherapy are highlighted in this review.

Nano-layered magnesium fluoride reservoirs on biomaterial surfaces strengthen polymorphonuclear leukocyte resistance to bacterial pathogens

Biomaterial-related bacterial infections cause patient suffering, mortality and extended periods of hospitalization, imposing a substantial burden on medical systems. In this context, understanding of nanomaterials-bacteria-cells interactions is of both fundamental and clinical significance. Herein, nano-MgF₂ films were deposited on titanium substrate via magnetron sputtering. Using this platform, the antibacterial behavior and mechanism of the nano-MgF₂ films were investigated in vitro and in vivo. It was found that, for S. aureus (CA-MRSA, USA300) and S. epidermidis (RP62A), the nano-MgF₂ films possessed excellent anti-biofilm activity, but poor anti-planktonic bacteria activity in vitro. Nevertheless, both the traditional SD rat osteomyelitis model and the novel stably luminescent mouse infection model demonstrated that nano-MgF₂ films exerted superior anti-infection effect in vivo, which cannot be completely explained by the antibacterial activity of the nanomaterial itself. Further, using polymorphonuclear leukocytes (PMNs), the critical immune cells of innate immunity, a complementary investigation of MgF₂-bacteria-PMNs co-culturing revealed that the nano-MgF₂ films improved the antibacterial effect of PMNs through enhancing their phagocytosis and stability. To our knowledge, this is the first time of exploring the antimicrobial mechanism of nano-MgF₂ from the perspective of innate immunity both in vitro and in vivo. Based on the research results, a plausible mechanism is put forward for the predominant antibacterial effect of nano-MgF₂in vivo, which may originate from the indirect immune enhancement effect of nano-MgF₂ films. In summary, this study of surface antibacterial design using MgF₂ nanolayer is a meaningful attempt, which can promote the host innate immune response to bacterial pathogens. This may give us a new understanding towards the antibacterial behavior and mechanism of nano-MgF₂ films and pave the way towards their clinical applications.

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.

Antibacterial Surface Design of Titanium-Based Biomaterials for Enhanced Bacteria-Killing and Cell-Assisting Functions Against Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is one of the formidable and recalcitrant complications after orthopedic surgery, and inhibiting biofilm formation on the implant surface is considered crucial to prophylaxis of PJI. However, it has recently been demonstrated that free-floating biofilm-like aggregates in the local body fluid and bacterial colonization on the implant and peri-implant tissues can coexist and are involved in the pathogenesis of PJI. An effective surface with both contact-killing and release-killing antimicrobial capabilities can potentially abate these concerns and minimize PJI caused by adherent/planktonic bacteria. Herein, Ag nanoparticles (NPs) are embedded in titania (TiO2) nanotubes by anodic oxidation and plasma immersion ion implantation (PIII) to form a contact-killing surface. Vancomycin is then incorporated into the nanotubes by vacuum extraction and lyophilization to produce the release-killing effect. A novel clinical PJI model system involving both in vitro and in vivo use of methicillin-resistant Staphylococcus aureus (MRSA) ST239 is established to systematically evaluate the antibacterial properties of the hybrid surface against planktonic and sessile bacteria. The vancomycin-loaded and Ag-implanted TiO2 nanotubular surface exhibits excellent antimicrobial and antibiofilm effects against planktonic/adherent bacteria without appreciable silver ion release. The fibroblasts/bacteria cocultures reveal that the surface can help fibroblasts to combat bacteria. We first utilize the nanoarchitecture of implant surface as a bridge between the inorganic bactericide (Ag NPs) and organic antibacterial agent (vancomycin) to achieve total victory in the battle of PJI. The combination of contact-killing and release-killing together with cell-assisting function also provides a novel and effective strategy to mitigate bacterial infection and biofilm formation on biomaterials and has large potential in orthopedic applications.