Orthopaedic Infection: Prevention and Diagnosis

Role of Dithiothreitol in Detection of Orthopaedic Implant-Associated Infections

Orthopaedic implant-associated infections (OIAIs) represent a notable complication of contemporary surgical procedures, exerting a considerable impact on patient outcomes and escalating healthcare expenditures. Prompt diagnosis holds paramount importance in managing OIAIs, with sonication widely acknowledged as the preferred method for detecting biofilm-associated infections. Recently, dithiothreitol (DTT) has emerged as a potential substitute for sonication, owing to its demonstrated ability to impede biofilm formation. This study aimed to compare the efficacy of DTT with sonication in identifying microorganisms within implants. Conducted as a prospective cohort investigation, the study encompassed two distinct groups: patients with suspected infections undergoing implant removal (Group A) and those slated for hardware explantation (Group B). Hardware segments were assessed for biofilm-related microorganisms using both sonication and DTT, with a comparative analysis of the two methods. A total of 115 patients were enrolled. In Group A, no statistically significant disparity was observed between DTT and sonication. DTT exhibited a sensitivity of 89.47% and specificity of 96.3%. Conversely, in Group B, both DTT and sonication fluid cultures yielded negative results in all patients. Consequently, this investigation suggests that DTT holds comparable efficacy to sonication in detecting OIAIs, offering a novel, cost-effective, and readily accessible diagnostic modality for identifying implant-associated infections.

Value of ultrasound-guided aspiration of hip arthroplasties performed in an orthopedic clinic by orthopedic surgeons

Background: Total joint arthroplasties continue to increase as do periprosthetic joint infections (PJIs). Ultrasound-guided aspiration can yield useful synovial fluid for analysis while avoiding radiation exposure. This study presents a high-yield, ultrasound-guided technique with analysis of aspiration results. Methods: All consecutive ultrasound-guided aspirations of hip arthroplasties performed from May 2016 through to April 2019 were retrospectively reviewed. Patient demographic information, component specifics, presence of draining sinus, and inflammatory markers were recorded. Results of aspiration including volume, appearance, lavage use, synovial fluid differential leukocyte count, synovial neutrophil percent, and culture results were recorded. Surgical results, specimen cultures, and surgeon description of purulence were recorded. Aspiration results were compared to the surgical specimen results in all patients who underwent reoperations. Results: Review of 349 hip aspirations demonstrated accuracy of 87 %, sensitivity of 83 %, specificity of 89 %, positive predictive value of 79 %, and negative predictive value 91 %. Surgical and aspiration cultures matched in 81 % of cases. Bloody aspirates and aspirates obtained after lavage had less accuracy at 69 % and 60 %, respectively. Specificity was 100 % for cultures obtained with lavage and 91 % for bloody aspirates. Synovial leukocyte count and neutrophil percentage was obtained in 85 % of aspirations, and cultures were obtained in 98 % of aspirates. Contamination rate was 2 %. Conclusion: Ultrasound-guided aspirations aid in the diagnosis of PJI. The use of lavage to obtain fluid is helpful when aspiration cultures are positive. Bloody aspirates are less accurate but have high specificity. A low contamination rate and 88 % accuracy results with this meticulous technique.

Periprosthetic joint infection after primary TKA in the medicare population: How frequently are patients revised at a different hospital?

BACKGROUND

Periprosthetic infection (PJI) after total knee arthroplasty (TKA) places a significant burden on hospitals. We sought to describe the proportion of patients undergoing revision for PJI at a different hospital within one year of primary TKA and whether patient characteristics or hospital volume were associated with this change.

METHODS

Medicare data from 2005 to 2014 was retrospectively reviewed using PearlDiver. All patients over 64 years undergoing revision for PJI within one year of primary TKA were stratified by the revision occurring within 90 days. Hospitals were grouped by annual TKA volume as Low (<50), Medium (51-100), High (101-200), and Very High (>200). Associations of patient characteristics and hospital volume with revision at a different hospital were assessed using Chi-squared tests and Somers' D.

RESULTS

Of 8,337 patients undergoing revision within 90 days of TKA, 1,370 (16%) were revised at a different hospital. Changing hospitals was associated with having primary TKA at a lower volume hospital (24% for low, 15% medium, 12% high, and 12% very high; P < 0.001). Of 7,608 patients undergoing revision between 91 and 365 days, 1,110 (15%) were revised at a different hospital. Changing hospitals was associated with having primary TKA at a lower volume hospital (26% for low, 14% medium, 10% high, and 9% very high; P < 0.001). Changing hospitals was not associated with sex or age.

CONCLUSION

Patients frequently undergo revision for PJI at a different hospital, even within 90 days of TKA. Further research is needed to understand these implications of this care pathway shift.

Accuracy of Predictive Algorithms in Total Hip and Knee Arthroplasty Acute Periprosthetic Joint Infections Treated With Debridement, Antibiotics, and Implant Retention (DAIR)

BACKGROUND

Debridement, antibiotics, and implant retention (DAIR) failure remains high for total hip and knee arthroplasty periprosthetic joint infection (PJI). We sought to determine the predictive value of the CRIME80 and KLIC for failure of DAIR in acute hematogenous (AH) and acute postoperative (AP) PJIs, respectively.

METHODS

We identified 134 patients who underwent DAIR for AH PJI with <4 weeks of symptoms after index arthroplasty and 122 patients who underwent DAIR for AP PJI <90 days from index. In the AH group, 15 patients (11%) failed at 90 days and overall, 33 (25%) had failed by 2 years. In the AP group, 39 (32%) failed at 90 days and overall, 52 (43%) failed by 2 years. Logistic regression models were used to determine the area under the curve (AUC) to establish thresholds using the Youden index.

RESULTS

For the AP cohort, AUCs were below 0.66 for KLIC, Charlson comorbidity index, Elixhauser comorbidity index, and McPherson host grade. For the AH cohort, 90-day AUCs were 0.70 for CRIME80 and below 0.66 for Charlson comorbidity index, Elixhauser comorbidity index, and McPherson host grade. In multivariate analysis controlling for age, sex, and body mass index, the CRIME80 AUC improved to 0.77 at 90 days.

CONCLUSION

To the authors' knowledge, this study represents the first external validation of the KLIC and CRIME80 for predicting DAIR failure in a North American population. The results indicate that alternative methods for predicting DAIR failure at 90 days and 2 years for acute PJI are needed.

LEVEL OF EVIDENCE

Prognostic III.

Mg(OH)2 nanoparticles enhance the antibacterial activities of macrophages by activating the reactive oxygen species

Infection often causes disastrous consequences in all fields of clinical medicine, especially orthopedics. Hence, critical efforts are being made to engineer novel nanomaterials for the treatment of orthopedic infections due to the high biocompatibility and antibacterial properties they possess. The purpose of this study was to investigate the antibacterial effects of magnesium hydroxide (Mg(OH)₂ ) nanoparticles (NPs) in vitro and determine their possible mechanisms of action. In this study, Escherichia coli was selected as the pathogenic bacteria and it was found that Mg(OH)₂ NPs significantly inhibited the growth of E. coli by promoting nucleic acid leakage, inhibiting protein synthesis, and suppressing the metabolic activity. The minimum inhibitory concentration for these bacteria was determined to be 4.4 μg/ml. In vitro flow cytometry and immunofluorescence tests indicated that Mg(OH)₂ NPs induced the macrophages to generate reactive oxygen species to kill the bacteria. To understand the mechanisms involved in this process, western blotting was performed and it was found that Mg(OH)₂ NPs activated the phosphatidylinositol-3-kinase/serine-threonine kinase (PI3K/Akt) signaling pathway of macrophages to enhance their phagocytosis with no obvious cytotoxicity. Thus, Mg(OH)₂ NPs are a suitable choice to develop promising agents or coating materials for the treatment of clinically widespread infections in view of their safety, biocompatibility, and powerful antibacterial properties.

Assessing the Bioactive Profile of Antifungal-Loaded Calcium Sulfate against Fungal Biofilms

Calcium sulfate (CS) has been used clinically as a bone- or void-filling biomaterial, and its resorptive properties have provided the prospect for its use as a release mechanism for local antibiotics to control biofilms. Here, we aimed to test CS beads loaded with three antifungal drugs against planktonic and sessile fungal species to assess whether these antifungal beads could be harnessed to provide consistent release of antifungals at biofilm-inhibitory doses. A panel of different fungal species (n = 15) were selected for planktonic broth microdilution testing with fluconazole (FLZ), amphotericin B (AMB), and caspofungin (CSP). After establishing planktonic inhibition, antifungal CS beads were introduced to fungal biofilms (n = 5) to assess biofilm formation and cell viability through a combination of standard quantitative and qualitative biofilm assays. Inoculation of a hydrogel substrate, packed with antifungal CS beads, was also used to assess diffusion through a semidry material, to mimic active infection in vivo In general, antifungals released from loaded CS beads were all effective at inhibiting the pathogenic fungi over 7 days within standard MIC ranges for these fungi. We observed a significant reduction of pregrown fungal biofilms across key fungal pathogens following treatment, with visually observable changes in cell morphology and biofilm coverage provided by scanning electron microscopy. Assessment of biofilm inhibition also revealed reductions in total and viable cells across all organisms tested. These data show that antifungal-loaded CS beads produce a sustained antimicrobial effect that inhibits and kills clinically relevant fungal species in vitro as planktonic and biofilm cells.

Modified Cyclodextrin Microparticles to Improve PMMA Drug Delivery Without Mechanical Loss

Antibiotic-loaded poly(methyl methacrylate) (PMMA) cement is commonly used as a local delivery system to treat and prevent orthopedic infections associated with arthroplasties in load-bearing applications. However, these delivery systems are inefficient as release rate sharply declines to subinhibitory levels. Prior studies have shown that by adding in drug-filled cyclodextrin (CD) microparticles into PMMA cement, a more consistent release is observed, and antibiotic refilling through simulated implantation can be achieved. However, the mechanical strengths of PMMA is reduced. In order to decrease the mechanical loss, modified CD microparticles (PMMA-CD) are synthesized that contain covalently appended PMMA chains. The compressive strengths, handling characteristics, and refilling ability of PMMA cement with PMMA-CD are evaluated. Specifically, up to a 13.7% increase in compressive strength is observed when unmodified CD is substituted with PMMA-CD in PMMA samples with 10 wt% CD microparticles. Additionally, a 13.3% increase in working time, a 7.5% decrease in maximum polymerization temperature, and up to a 32.1% increase in amount of drug refilled are observed with the addition of 10 wt% CD PMMA-CD into PMMA in comparison to plain PMMA without CD microparticles.

Fatores de risco para infecção de sítio cirúrgico em cirurgias traumato-ortopédicas

Introdução: A Infecção do Sítio Cirúrgico ocupa a terceira posição entre as infecções adquiridas em serviços de saúde, configurando-se como um importante problema de saúde pública, presente em cerca de 15% daquelas encontradas em pacientes hospitalizados, e um dos tipos de cirurgias de maior probabilidade para esse evento são as traumato-ortopédicas. Objetivo: Verificar a associação entre os fatores de risco e a presença de Infecção de Sítio Cirúrgico em cirurgias traumato-ortopédicas. Materiais e métodos: Estudo prospectivo descritivo, quantitativo, realizado entre agosto a outubro de 2017 com 84 pacientes. Os dados referentes ao paciente, ao procedimento e os sinais de Infecções de Sítio Cirúrgico, encontrados no terceiro e décimo dia de pós-operatório, foram coletados por meio de um formulário. Resultados: Das variáveis estudadas, comportaram-se como fatores de risco de Infecção de Sítio Cirúrgico: tabagismo, diabetes e idade acima de 50 anos. A idade foi o principal fator de risco relacionado ao paciente, presente em 31, 36,9% dos casos. Dor, edema e hiperemia foram os sinais de infecção mais prevalentes. Discussão e conclusões: Os fatores de risco relacionados ao paciente possuem maior relevância na associação com infecção do sítio cirúrgico em comparação com os relacionados ao procedimento.

Surgical site infection in hip arthroplasty in a 10-year follow-up prospective study: Risk and factors associated

BACKGROUND

The increased demand for hip arthroplasty means a growing number of postsurgical complications. This study aims to assess the risk of surgical site infection (SSI) in a teaching hospital; develop regional, national and international external comparisons; and evaluate SSI-related risk factors, particularly according to the timing of surgery (urgent/unplanned or elective).

METHODS

Prospective cohort study from January 2008 to December 2018. Patients were followed up to 90 days after surgery. Primary endpoint was SSI incidence according to the Centers for Disease Control and Prevention criteria. Multivariate analysis was conducted to find independently associated SSI risk factors. The association between risk factors and SSI incidence was assessed by reference to odds ratio (OR). Analyses were also performed among urgent/unplanned and elective patients to identify whether SSI risk factors differed between groups.

RESULTS

The study population (n = 1,808) has an overall SSI rate of 3.0% (95% confidence interval [CI]: 2.4-3.9). Timing of surgery caused an effect modification, so surgery duration> 75th percentile (OR: 3.8; 95% CI: 1.5-9.8) and inadequate preparation (OR: 3.3; 95% CI: 1.1-10.0) were independent risk factors in the urgent/unplanned group; National Healthcare Safety Network risk index≥ 2 (OR: 6.3; 95% CI: 0.1-19.2) and transfusion (OR: 3.6; 95% CI: 1.1-11.9) in the elective group.

CONCLUSIONS

Hospital infection surveillance systems allow identifying risk factors susceptible to change. Characterization of factors that caused an effect modification is key to identify areas of quality improvement, including reducing operating times, preventing perioperative blood transfusion, or improving patient preparation before surgery.

Two-stage arthrodesis for complex, failed, infected total knee arthroplasty

AIMS

Arthrodesis is rarely used as a salvage procedure for patients with a chronically infected total knee arthroplasty (TKA), and little information is available about the outcome. The aim of this study was to assess the reliability, durability, and safety of this procedure as the definitive treatment for complex, chronically infected TKA, in a current series of patients.

METHODS

We retrospectively identified 41 patients (41 TKAs) with a complex infected TKA, who were treated between 2002 and 2016 using a deliberate, two-stage knee arthrodesis. Their mean age was 64 years (34 to 88) and their mean body mass index (BMI) was 39 kg/m² (25 to 79). The mean follow-up was four years (2 to 9). The extensor mechanism (EM) was deficient in 27 patients (66%) and flap cover was required in 14 (34%). Most patients were host grade B (56%) or C (29%), and limb grade 3 (71%), according to the classification of McPherson et al. A total of 12 patients (29%) had polymicrobial infections and 20 (49%) had multi-drug resistant organisms; fixation involved an intramedullary nail in 25 (61%), an external fixator in ten (24%), and dual plates in six (15%).

RESULTS

Survivorship free from amputation, persistent infection, and reoperation, other than removal of an external fixator, at five years was 95% (95% confidence interval (CI) 89% to 100%), 85% (95% CI 75% to 95%), and 64% (95% CI 46% to 82%), respectively. Reoperation, other than removal of an external fixator, occurred in 13 patients (32%). After the initial treatment, radiological nonunion developed in ten knees (24%). Nonunion was significantly correlated with persistent infection (p = 0.006) and external fixation (p = 0.005). Of those patients who achieved limb salvage, 34 (87%) remained mobile and 31 (79%) had 'absent' or 'minimal' pain ratings.

CONCLUSION

Knee arthrodesis using a two-stage protocol achieved a survivorship free from amputation for persistent infection of 95% at five years with 87% of patients were mobile at final follow-up. However, early reoperation was common (32%). This is not surprising as this series included worst-case infected TKAs in which two-thirds of the patients had a disrupted EM, one-third required flap cover, and most had polymicrobial or multi-drug resistant organisms. Cite this article: Bone Joint J 2020;102-B(6 Supple A):170-175.

Development and challenges in setting up an international bone infection registry

INTRODUCTION

Osteomyelitis is an increasing burden on the society especially due to the emergence of multiple drug-resistant organisms. The lack of a central registry that prospectively collects data on patient risk factors, laboratory test results, treatment modalities, serological analysis results, and outcomes has hampered the research effort that could have improved and provided guidelines for treatments of bone infections. The current manuscript describes the lessons learned in setting up a multi-continent registry.

MATERIALS AND METHODS

This multicenter, international registry was conducted to prospectively collect essential patient, clinical, and surgical data with a 1-year follow-up period. Patients 18 years or older with confirmed S. aureus long bone infection through fracture fixation or arthroplasty who consented to participate in the study were included. The outcomes using the Short Form 36 Health Survey Questionnaire (version 2), Parker Mobility Score, and Katz Index of Independence in Activities of Daily Living were assessed at baseline and at 1 month, 6 months, and 12 months. Serological samples were collected at follow-ups.

RESULTS

Contract negotiation with a large number of study sites was difficult; obtaining ethics approvals were time-consuming but straightforward. The initial patient recruitment was slow, leading to a reduction of target patient number from 400 to 300 and extension of enrollment period. Finally, 292 eligible patients were recruited by 18 study sites (in 10 countries of 4 continents, Asia, North and South America, and Central Europe). Logistical and language barriers were overcome by employing courier service and local monitoring personnel.

CONCLUSIONS

Multicenter registry is useful for collecting a large number of cases for analysis. A well-defined data collection practice is important for data quality but challenging to coordinate with the large number of study sites.

Does the induced membrane have antibacterial properties? An experimental rat model of a chronic infected nonunion

INTRODUCTION

The Masquelet procedure proved its efficiency in treating infected nonunion filling bony gaps up to 25 cm. Yet the use of local antibiotics is still questionable in the daily practice with lack of evidence regarding its usefulness in controlling infection. An experimental rat model is put in place to study the antibacterial properties of the induced membrane produced during the first stage of Masquelet.

METHOD

Twenty-three-month-old wistar male rats are inoculated with a 0.5 mL solution of 10^8 CFU/mL MRSA over a critical fracture done on the right femur. Six weeks later, remaining 11 rats exhibiting signs of a chronic infection with a sinus tract and oozing pus along with radiological nonunion are used for a first stage Masquelet procedure. They are randomly divided into two groups with six rats having no local antibiotic in the cement mixture and five rats having 3 g of vancomycin mixed with gentamycin loaded cement. Six weeks later (twelve weeks from baseline), all eleven rats are euthanized and blood samples for C-reactive protein are withdrawn. The induced membrane is identified and resected along with bone fragments and sent for cultures and pathology.

RESULTS

MRSA is isolated in the cultures of all six rats in the first group where no local antibiotic was added. Altered polymorphonuclears with abscess and pus are noted on four of six pathology samples. However in the second group where local antibiotics were added, three out of five rats exhibited eradication of MRSA (p = 0.034) and all samples did not exhibit clear infection signs on pathology. A pyo-epithelioid over a foreign body reaction is seen predominantly in this group demonstrating a regenerative process.

DISCUSSION

The induced membrane does not have antimicrobial properties capable of overcoming an infected nonunion on its own. When local antibiotics were added during the first stage of the Masquelet procedure, new bone formation occurred indicating the need to control an infection in order for bone union to occur.

CONCLUSION

Local antibiotics use in adjunction to extensive debridement is advisable during the first stage of a Masquelet procedure for an infected nonunion.

Surgical site infection incidence and risk factors in knee arthroplasty: A 9-year prospective cohort study at a university teaching hospital in Spain

BACKGROUND

Surgical site infection (SSI) is one of the complications posed by knee replacement surgery. Hospital-based infection surveillance systems may provide indicators of improvement and allow the characterization of risk factors critical to reduce infection. The aims of this study were to compare the incidence of SSI in our center with rates in the Madrid Region, Spain, and the United States, and to evaluate any possible SSI-related risk factor in knee replacement surgery.

METHODS

All patients who underwent knee replacement surgery at a tertiary hospital in 2008-2016 were included. SSI was defined according to Centers for Disease Control and Prevention criteria. Infection rate was calculated. The association between risk factors and SSI incidence was assessed by reference to odds ratio (OR) with multivariate analysis.

RESULTS

The study population (n = 1969) had a global SSI risk of 1.0%. We found a declining trend in the follow-up period, from an SSI risk of 1.8% in 2009 to 0.4% in 2016. Independent risk factors included hair removal (OR: 3.09, 95% confidence interval [CI]: 1.27-7.50) and National Healthcare Safety Network risk index ≥ 2 (OR: 9.37, 95% CI: 2.90-30.26).

CONCLUSION

This study identified risk factors that showed the necessity to strictly comply with wound decontamination and patient preparation protocols, reduce surgery duration, and identify patients who require comprehensive monitoring.

Prevention and detection of prosthetic temporomandibular joint infections-update

Prosthetic joint infections are not only distressing complications for patients and surgeons, but also have an enormous financial impact on healthcare systems. The reported incidence of prosthetic joint infection is likely underestimated due to difficulties in their diagnosis. This unfortunate complication has challenged joint replacement surgeons for years, despite all the advances made in this surgical discipline. Since eradication of these infections can be very difficult, prevention remains the primary objective. Identifying recipient risk factors, adopting a proper surgical technique, appropriate wound care, optimizing the operating room environment, and appropriate postoperative care have become some of the core elements that can help to minimize the overall incidence of this complication. The purpose of this article is to provide the temporomandibular joint replacement surgeon with an update on the prevention and detection of prosthetic joint infections based on a review of the most recent information published in the orthopedic and surgical literature.

Antibiotic Prophylaxis and Prevention of Surgical Site Infection in Shoulder and Elbow Surgery

Infection after orthopedic procedures is a devastating and serious complication associated with significant clinical and financial challenges to the health care system and unfortunate patient. The time and resource-intensive nature of treating infection after orthopedic procedures has turned attention toward enhancing prevention and establishing quality improvement measures. Prevention strategies throughout the perioperative period include host optimization, risk mitigation, reducing bacterial burden and proper wound management. Understanding the most common offending organisms of the shoulder, Propionibacterium acnes and coagulase negative Staphylococcus species, and their hypothesized mechanism of infection is crucial to selecting appropriate preventative measures.

Infection burden in total hip and knee arthroplasties: an international registry-based perspective

Background

Infection remains a leading cause of failure of hip and knee replacements. Infection burden is the ratio of implants revised for infection to the total number of arthroplasties in a specific period, measuring the steady state of infection in a registry. We hypothesized infection burden would be similar among arthroplasty registries.

Methods

We evaluated publicly reported data from 6 arthroplasty registries (Australian Orthopaedic Association National Joint Replacement Registry [AOANJRR], New Zealand Joint Registry, Swedish Hip Arthroplasty Register, Swedish Knee Arthroplasty Register, National Joint Registry of England, Wales, Northern Ireland, and the Isle of Man, and the American Joint Replacement Registry) for revisions performed with an infection diagnosis over the last 6 years.

Results

The 2015 hip infection burden varied between registries from 0.76% (AOANJRR) to 1.24% (Swedish Hip Arthroplasty Register), and the unweighted overall average for hip infection burden was 0.97%. In 2012, 2013, and 2014, average hip infection burden held steady at 0.87%, 0.93%, and 0.94%, respectively, higher than the preceding 2 years. The 2015 knee infection burden varied from 0.88% (AOANJRR) to 1.28% (Swedish Knee Arthroplasty Register), and the unweighted average was 1.03%. In 2012, 2013, and 2014, knee infection burden was 1.04%, 1.11%, and 1.02%, respectively. These numbers were also higher than the preceding 2 years.

Conclusions

Infection burden may be one measure of the overall success in registry populations as well as monitoring the steady state of infection worldwide. Despite global efforts to reduce postoperative infection, infection burden has actually increased in the selected registries over time.