We examined the usefulness of neutrophil CD64 expression in detecting local musculoskeletal infection and the impact of antibiotics on its expression. Of 141 patients suspected of musculoskeletal infection, 46 were confirmed by microbiological culture to be infected and 95 had infection excluded. The median CD64 count of patients with localised infection was 2230 molecules per cell (interquartile range (IQR) 918 to 4592) and that of the patients without infection was 937 molecules per cell (IQR 648 to 1309) (p < 0.001). The level of CD64 correlated with the CRP level in patients with infection, but not in those without infection (r = 0.59, p < 0.01). Receiver operator characteristic curve analysis revealed that CD64 was a good predictor of local infection. When the patients were subdivided into two groups based on the administration of antibiotics at the time of CD64 sampling, the sensitivity for detecting infection was better in those who had not received antibiotics. These results suggest that measurement of CD64 expression is a useful marker for local musculoskeletal infection

Aim. Prosthetic joint infections (PJI) and fracture related infections (FRI) are the most challenging complications in orthopaedic surgery. An interdisciplinary approach is mandatory not only to correctly diagnose and treat major musculoskeletal infections but also to address the comorbidities and impairments these patients are not rarely suffering from. Since, little data exists on cardiac complications following PJI and FRI revision surgery, this study aimed to investigate the risk of perioperative myocardial injury (PMI) and mortality. Method. We prospectively included consecutive patients at high cardiovascular risk (defined as expected postoperative hospital stay of >24 hours PLUS age >45 years with pre-existing coronary, peripheral or cerebrovascular artery disease OR age >65 years) undergoing major orthopaedic surgery between 2014 and 2016. All patients received a systematic screening to reliably detect PMI, using serial measurements of high-sensitivity cardiac troponin T (hs-cTnT). All-cause mortality was assessed at 30 days and one year. Multivariable logistic regression models were applied to compare incidence of PMI and mortality between patients undergoing septic revision surgery (for PJI/FRI) and patients receiving aseptic major bone and joint surgery. Results. In total 911 consecutive patients, with an overall PMI rate of 15.4% (n=140) were included. The PMI incidence in patients undergoing septic revision surgery was significantly higher compared to aseptic orthopaedic surgeries (29.2% vs 14.3%, p=0.001), also after multivariable adjustment (odds ratio 2.1, p=0.02). Mortality was higher at one year (16.9% vs. 8.3%, p=0.037) and numerically at 30 days (6.2% vs. 2.4%, p=0.085) in patients undergoing septic revision surgery. Virulence of the disease-causing pathogen showed no significant relationship with PMI incidence or mortality. Conclusions. Patients undergoing revision surgery for PJI or FRI were at a distinct higher risk of PMI and death compared to matched non-septic patients. In major bone and joint infections screening for PMI and treatment in specialized multidisciplinary units should be considered

Infection of the musculoskeletal (MSK) system is a dreaded complication that seems to be on the rise. Many factors, such as resistant bacteria or poor host factors, may influence such rise. This increase leads to greater resource consumption, especially due to antibiotic (ATB) prescription. Strategies must be created to detect patients at risk and prevent such infections. Hospital administrators should be made aware of the costs and impact of MSK infections in order to understand the need to prevent such complications.

Therefore, our goal is to characterize the infected orthopaedic patient and evaluate the cost associated with ATB prescription in such cases.

This is a retrospective and descriptive study, based on patient record analysis of all patients treated at our department, from January 2013 to March 2015.

We identified 177 patients with a MSK infection and an isolated infectious agent.

There was no predominance of either sex. Approximately 50% of patients were aged between 66 and 85 years old.

Most frequent agents were MSSA (30,2%) and MRSA (21,8%), followed by Streptococcus species (8,9%) and Pseudomonas aeruginosas (7,1%). Although most patients were infected by a single agent, 18,6% had two or more causative agents isolated in cultures. Of those, 69,7% had either MSSA or MRSA as one of the isolated agents.

Most commonly affected area was the hip (39,5%), followed by the knee (23,2%) and ankle (21,5%). Nearly all patients had had prior surgery, with arthroplasty and osteosynthesis as the most common procedures (52,4% and 33,3%, respectively).

Infection related admission was responsible for a total of 6.116 hospital bed-days, with the majority of patients staying in hospital for up to 30 days (77,3%).

Total cost of hospital ATB administration was 61.365,61€, with approximately 346,7€ spent in each patient. This corresponds to 42,6% of the total cost of medication during hospital stay (144.146,1€ of total cost, with 814,4€ per patient).

The typical infected orthopaedic patient is aged 66 to 85 years old, was operated to his hip or knee, and either an arthroplasty or osteosynthesis was performed. Staphylococcus aureus remains the most common agent.

MSK infections have significant costs associated with their treatment, and clinical departments should periodically re-evaluate discharged patients in order to understand what groups are at risk of developing such a complication.

Only a correct identification of all these factors makes it possible to create a targeted preventive strategy, in order to reduce costs to the institution.

Introduction

Accurate diagnosis of peri-prosthetic joint infection is critical to allow adequate treatment. Currently, the criteria of the Musculo-Skeletal Infection Society (MSIS) serve as a validated reference tool. More recently, these criteria have been modified for better accuracy. The goal of this study was to compare retrospectively the diagnostic accuracy of these two different tools in cases of known peri-prosthetic hip or knee infection or in aseptic cases and to analyze one additional criterion: presence of an early loosening (prior to 2 years after implantation).

We compared the use of broth culture medium for samples taken in theatre with the standard practice of placing tissue samples in universal containers. A total of 67 consecutive patients had standard multiple samples of deep tissue harvested at surgery and distributed equally in theatre either to standard universal containers or to broth culture medium. These samples were cultured by direct and enrichment methods. The addition of broth in theatre to standard practice led to an increase in sensitivity from 83% to 95% and an increase in negative predictive value from 77% to 91%. Placing tissue samples directly into broth in the operating theatre is a simple, inexpensive way to increase the sensitivity of cultures from infected patients, and does not appear to compromise the specificity of these cultures.

Cite this article: Bone Joint J 2014;96-B:1566–70.

Aim. Musculoskeletal infection is a serious complication, however literature is lacking prospective data on its impact on mental health. The study aimed to assess mental health in patients with musculoskeletal infections and how they experience the possible mental and physical impairment. Method. All patients treated in our unit for musculoskeletal infections between July 2020 and March 2022 were prospectively included. To assess specific patient reported outcomes the following questionnaires were used: World-Health-Organization Quality-Of-Life (WHOQOL)-BREF and the Veterans-RAND-12Item Health Survey (VR-12) for mental & physical health; Patient-Health-Questionnaire (PHQ-8) for depression symptoms; Generalized-Anxiety-Disorder-Scale-7 (GAD-7) for anxiety symptoms and Somatic-Symptom-Disorder-B Criteria Scale (SSD-12) for experience of mental & physical impairment. The surveys were conducted at baseline, 6 and 12-weeks and 1-year. Results. In total 199 patients were included (31 fracture-related infections, 80 prosthetic joint infections, 40 diabetic foot syndromes and 48 other musculoskeletal infections). Physical health was significantly worse 6 weeks after treatment compared to baseline (WHOQOL p=.002; VR-12 p<.001), but significantly better at 3-months (p<.001; p=.006) and 12-months (p=.003; p<.001). Mental health was significantly worse at 3-months (WHOQOL p=.002), but at final follow-up significantly better (VR-12 p=.046). Social relationships (domain of WHOQOL) were perceived significantly worse 6 weeks and 12 months after treatment initiation (p=.003; p=.007), as were environmental factors. At baseline moderate to severe depression symptoms (PHQ-8≥10) and moderate to severe anxiety symptoms (GAD-7≥10) were observed in 14.6%, respectively 10.6% of all patients. At 12-months these were 7.4% and 3%. Over the course of treatment, only patients with DFS showed a significant change in experienced psychological or physical impairment, which was perceived significantly less compared 6 weeks to 12 months (p=.042). Conclusions. Patients with musculoskeletal infections suffer from a considerable impact on their mental health. The greatest impairment in physical health was seen 6 weeks after beginning of treatment. The psychological well-being was worse at 3-months. Environmental factors, such as mobility, activities of daily living and dependence on medication or medical treatment were worst at 3-months. Also increasingly worse social relationships over the course of treatment was observed. Further studies are needed to identify psychological impairment and related factors, as well as to determine how patients cope with their disease and treatment. This could serve as a foundation to implement treatment algorithms in order to improve patient related outcome and quality of life

Aim. Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is commonly associated with serious cases of community-onset skin and musculoskeletal infections (Co-SMSI). Molecular epidemiology analysis of CA-MRSA recovered from skin and soft tissues specimens is lacking in Latin America. This study aimed to identify phenotypic and genotypic features of MRSA isolates recovered from patients presenting Co-SMSI. Methods. Consecutive MRSA isolates recovered from Co-SMSI of patients admitted from March 2022 to January 2023 in a Brazilian teaching hospital were tested for antimicrobial resistance and characterized by their genotypic features. Identification was carried out by automated method and through MALDI-TOF MS. Antimicrobial susceptibility was tested by disk diffusion, broth microdilution and E-test strips for determination of the minimal inhibitory concentration (MIC) according to recommendations from the Brazilian Committee on Antimicrobial Susceptibility Testing (BrCAST) and European Committee on Antimicrobial Susceptibility Testing (EUCAST). Gene mecA characterization and Sccmec typing were performed by multiplex polymerase chain reaction (PCR) assay, and gene lukF detection by single PCR. Patients were prospectively followed up for two months, in order to determine their clinical characteristics and outcomes. Results. Overall, 48 Staphylococcus aureus isolates were obtained from 68 samples recovered from patients with Co-SMSI. Twenty two (42%) were phenotypically characterized as MRSA, although mecA gene was only identified in 20 of those samples. Sccmec was untypable in 12 isolates, Sccmec was type II in 4 isolates and 2 were classified as type IVa. LukF gene was identified in 5 isolates. Antimicrobial resistance profile showed that all isolates were susceptible to linezolid and vancomycin with MIC = 1 and MIC = 2 in 66,7% and 33.3%, respectively. Susceptibility to quinolones was worryingly low and none of the isolates were sensitive to usual doses of ciprofloxacin and levofloxacin, and showed increased rates of resistance to increased exposure to these drugs, as well. Isolates were both susceptible to gentamicin and tetracycline in 85% and resistance to also Sulfamethoxazole/Trimethoprim occurred in only 2 isolates. Mortality rate evaluated within 1 month of the initial evaluation was 10% among MRSA isolates. Conclusions. Our results showed that CA-MRSA isolates causing Co-SMSI demonstrated an alarming pattern of multidrug resistance, including to β-lactam and quinolones, which have been commonly prescribed as empirical therapy for patients with skin, soft tissue and musculoskeletal infections

Acute Haematogenous Osteomyelitis (AHO) remains a cause of severe illness among children with the possibility of long-term consequences for growth and development. Previous research on sequelae from AHO rarely considers outcomes more than two years following treatment. This study aims to establish the quality of life of patients diagnosed with AHO in childhood up to 13 years after diagnosis, evaluating the impact on social, emotional, physical, and school function. Children treated for AHO between 2008–2018 at a tertiary referral centre in New Zealand were identified. PedsQL™ questionnaires were conducted via phone with either the child or primary caregiver and responses analysed. 40 patients met inclusion criteria, were contactable by phone, and consented to participate. The mean age was 7 years (range 0–15) and most were female (60%). Health related quality of life (HRQOL) was scored as a percentage with most participants scoring >80% (n=27). Those who do experience reduced quality of life following treatment for AHO were likely to complain of pain, stiffness, or anxiety. The impact of significant childhood illness on mental health was not adequately captured by the PedsQL™ but was highlighted in qualitative feedback. We conclude that the majority of children treated for AHO reported excellent health-related quality of life up to 13 years following treatment although an negative impact on mental health was reported using qualitative analysis. A refined scoring system is needed to assess the long-term impact of musculoskeletal infection

Prosthetic joint infection (PJI) remains one of the most challenging complications to manage following total joint arthroplasty (TJA). There is a paucity of published data on the management of PJI in smaller, rural hospital settings. In this study, we investigate [1] the success rate of surgical management for PJI following TJA and [2] the microbiology of infecting organisms in this unique geographical environment. We performed a retrospective single-centre study at a rural hospital (Southland Hospital, Invercargill, New Zealand) over a 3-year period (2019 to 2022). All patients presenting with a first episode of PJI fulfilling Musculoskeletal Infection Society criteria after hip or knee arthroplasty were included. All patients had a minimum follow up of 6 months. Treatment success was defined eradication of infection. Twenty-one cases (14 hips and 7 knees) were identified. These were managed with Debridement, antibiotics, and implant retention (DAIR) procedure (n=14, 67%), single-stage revision (n=6, 29%), or long-term suppressive antibiotics (n=1, 4%). Of the DAIR patients, infection recurred in 50% and underwent subsequent revision. Of the single-stage revision patients, 17% failed and underwent subsequent revision. The overall success rate was 90%. Methicillin-sensitive Staphylococcus aureus (MSSA) was the most isolated pathogen (57%,) with no methicillin-resistance Staphylococcus aureus (MRSA) identified. Overall, 90% of infecting organisms were cefazolin sensitive. These results suggest that management of PJI is a safe and viable treatment option when performed in a rural hospital setting, with comparable treatment success rates to urban centres. The incidence of MRSA is low in this setting. Rates of antibiotic resistance were relatively low and most organisms were sensitive to cefazolin, the routine antibiotic used in prophylaxis

Aim. Predicting success of a Debridement, Antibiotics and Implant Retention (DAIR) procedure for Periprosthetic Joint Infection (PJI) remains a challenge. A failed DAIR might adversely affect the outcome of any future revision surgery for PJI. Hence, the ability to identify and optimise factors predictive of DAIR success would help target the procedure to the appropriate patient cohort and avoid unnecessary surgery for patients where a DAIR is unlikely to eradicate infection. Method. A retrospective review of our prospective Bone Infection Group database was performed to identify all patients who underwent a DAIR of their hip or knee arthroplasty. Diagnosis of PJI was confirmed using the Musculoskeletal Infection Society (MSIS) 2013 and the European Bone and Joint Infection Society (EBJIS) 2021 classification systems. DAIR surgery was grouped into “successful” or “unsuccessful” outcomes as per the MSIS working group outcome-reporting tool. Results. Sixty-Four consecutive patients with an acute PJI underwent a DAIR procedure between 2009 and 2020. Treatment was successful in 44 (69%). The chance of a successful DAIR was significantly greater if performed within one week of symptom onset compared to greater than one week duration (adjusted odds ratio (OR 0.11; p=0.027; 95% CI [0.02- 0.78]). The chances of a successful DAIR was not influenced by whether the surgeon was an arthroplasty or non-arthroplasty surgeon (OR 0.28; p=0.13; 95% CI [0.05- 1.48]). Isolated Streptococcus infection had a success rate of 100%; followed by Coagulasenegative Staphylococci 71% and Methicillin-susceptible Staphylococcus Aureus 65%. Polymicrobial infection had the worst outcome with a success rate of 47%. Conclusions. In our experience DAIR surgery performed within one week of symptom onset, significantly increased chances of successful infection eradication. Collaborative work is required to ensure arthroplasty patients access prompt appropriate surgical decision-making, remove barriers to early assessment and minimise delays to surgery

Aim. Evaluate if Neutrophil Extracellular Traps related biomarkers (citrullinated histone H3 [H3Cit], cellfree DNA [cfDNA], and myeloperoxidase) are increased in synovial fluid of patients with PJI and investigate the diagnostic accuracy of NET formation biomarkers for PJI. Method. Patients who underwent hip or knee revision total joint arthroplasty were categorised into two groups according to the Second International Consensus Meeting on Musculoskeletal Infection (2018) criteria. Sixteen patients were classified as infected and 16 as non-infected. cf-DNA, myeloperoxidase and H3Cit were measured in synovial fluid collected during surgery. Sensitivity, specificity, and receiver operating characteristic (ROC) curve were calculated. Results. Patients with PJI presented significantly higher levels of synovial fluid cf-DNA (105.5 ng/ml ± 58.3 vs 1.9 ± 1.2, p>0.0001), myeloperoxidase (1575 pg/ml ± 826 vs 50.16 ± 100, p<0.0001) and citrullinated histone H3 (1.688 ± 1.214 vs 13.88 ± 24.4, p < 0.0001). In the ROC curve analyses, the area under the curve for cf-DNA, myeloperoxidase and H3cit were 1 [0.89 – 1], 0.98 [0.86 – 1], and 0.94 [0.8 – 0.99], respectively. The sensitivity for detecting PJI using synovial fluid was 100% for cf-DNA, 93,7% for myeloperoxidase, and 87,5% for H3cit. The sensitivity for cf-DNA and myeloperoxidase was 100%, and 87,5 % for H3cit. Conclusions. Our results show that neutrophils within periprosthetic microenvironment release NETs as part of the bactericidal arsenal to fight infection. These results allow a better understanding of the cellular and molecular processes that occur in this microenvironment, enabling the design of more assertive strategies for the identification of new biomarkers and for a better use of the available ones. Furthermore, novel studies are needed to define whether and how NET-related biomarkers can be useful for the diagnosis of PJI

Survival of sepsis has been documented worldwide, but little is documented about the long-term health outcomes of multifocal sepsis from acute musculoskeletal infection - the first study of its kind in New Zealand. Children admitted to the Paediatric Intensive Care Unit (PICU) from 1. st. January 2002 to 31. st. December 2017 with a musculoskeletal focus of infection were identified from hospital coding data. Notes review from discharge to present day determined survival and morbidity. Present-day clinical assessment of the musculoskeletal and respiratory systems along with questionnaires on health-related quality of life, mental health and sleep were performed. Seventy patients were studied. Seven children died acutely (five Pasifika and two Māori children) indicating 10% mortality. Long-term survival was favourable with no recorded deaths after discharge. Recurrence/chronic infection occurred in 23%, a mean of 1.1 year after discharge. Growth disturbance occurred in 18%, a mean of 3 years after discharge. The hip joint and proximal femur have the worst complications. Children under 2 years are most at risk of long-term disability. No patients had chronic respiratory illness beyond 90 days. Fifteen children had symptoms of acute neurological impairment, three of whom had permanent brain injury. Twenty-six survivors (41%) were assessed a mean of 8.2 years after discharge. Health-related quality of life scores were on par with normative data. Six patients and eight parents screened positive for moderate to severe post-traumatic stress disorder. Paediatric multifocal musculoskeletal sepsis can result in complex illness with long hospital stay and multi-organ complications. Māori and Pasifika children, those under two and those involving the proximal femur/or hip are most at risk. Other outcomes are favourable with no evidence of chronic lung disease or poor quality of life. A period of rehabilitation for children with identified acquired brain injury should be part of discharge planning

Aim. Magnetic resonance imaging (MRI) and 2-[. 18. F]-fluoro-2-deoxy-D-glucose (. 18. F-FDG) Positron Emission Tomography, paired with Computed Tomography (PET/CT) are two indicated advanced imaging modalities in the complicated diagnostic work-up of osteomyelitis. PET/MRI is a relatively novel hybrid modality with suggested applications in musculoskeletal infection imaging. The goal of this study was to assess the value of hybrid . 18. F-FDG PET/MRI for chronic osteomyelitis diagnosis and surgical planning. Method. Five suspected chronic osteomyelitis patients underwent a prospective . 18. F-FDG single-injection/dual-imaging protocol with hybrid PET/CT and hybrid PET/MR. Diagnosis and relevant clinical features for the surgeon planning treatment were compared. Subsequently, 36 patients with . 18. F-FDG PET/MRI scans for suspected osteomyelitis were analysed retrospectively. Sensitivity, specificity, and accuracy were determined with the clinical assessment as the ground truth. Standardized uptake values (SUV) were measured and analysed by means of receiver operating characteristics (ROC). Results. The consensus diagnosis was identical for PET/CT and PET/MRI in the prospective cases, with PET/CT missing one clinical feature. The retrospective analysis yielded a sensitivity, specificity, and accuracy of 78%, 100%, and 86% respectively. Area under the ROC curve was .736, .755, and.769 for the SUVmax, target to background ratio, and SUVmax_ratio respectively. These results are in the same range and not statistically different compared to diagnostic value for . 18. F-FDG PET/CT imaging of osteomyelitis in literature. Conclusions. Based on our qualitative comparison, reduced radiation dose, and the diagnostic value that was found, the authors propose . 18. F-FDG PET/MRI as an alternative to . 18. F-FDG PET/CT in osteomyelitis diagnosis, if available

Aim. Antimicrobial peptides occur naturally in our intrinsic immune system. PLG0206 is a novel, engineered, 24-amino acid peptide which has broad-spectrum antimicrobial activity, including in biofilm and against multi-drug resistant pathogens (1,2). This is the first clinical study to evaluate the safety and tolerability of PLG0206 when administered via an irrigation solution in patients with periprosthetic joint infections (PJI) following total knee arthroplasty (TKA) during debridement, antibiotics, and implant retention (DAIR). Secondary objectives were to evaluate pharmacokinetics (PK), biomarkers and initial clinical efficacy at one year post-DAIR procedure. Method. This prospective, multicenter, open-label, interventional study assessed two dose levels of PLG0206. Fourteen patients underwent revision for PJI after TKA. At the end of debridement, they received a single intra-articular irrigation of PLG0206 into the wound cavity lasting 15 minutes at concentrations of 3 mg/mL (n=7) or 10 mg/mL (n=7). Patients received post-operative care and intravenous/oral antimicrobial therapy as per their institutional guidelines. Patients were monitored for safety and signs of relapse or persistent infection for 12 months post study drug administration and PK and blood biomarkers were assessed. Results. All patients completed their final study assessment at Day 365. Over the 1-year follow-up, only one recurrence (7%) was noted at Day 169 in the low-dose cohort. Following dosing, nine patients (64.3%) had limited systemic exposure; maximum plasma concentration occurred 1-hour post-administration and declined rapidly to undetectable levels by 24 hours following treatment in all patients. The incidence of drug related treatment-emergent adverse events (TEAEs) was low. Two patients, both in the higher dose cohort, experienced a transient drug related TEAE; one of hypertransaminasaemia and one of neuralgia. Both events were moderate in severity and resolved within two weeks of onset. Conclusions. A single 15-minute irrigation of PLG0206 into the wound cavity of patients undergoing a DAIR procedure for PJI following TKA, is safe and well tolerated by patients. This new antimicrobial peptide offers a promising therapeutic option in musculoskeletal infection. The initial clinical efficacy is encouraging but now needs to be investigated in a much larger clinical trial

Aim. Pelvic osteomyelitis following pressure ulceration results in substantial patient morbidity. Previous studies have reported a heterogenous approach to diagnosis and medical management by physicians, suggesting equipoise on key clinical questions. This study hypothesised that the same equipoise exists amongst Orthopaedic surgeons. Method. An 18-question multiple-choice questionnaire was designed through an iterative feedback process until the final version was agreed by all authors. Likert-type scale responses were used with graded responses (e.g., never/fewer than half of patients/around half of patients/more than half of patients/every patient). The online survey was sent to members of the Musculoskeletal Infection Society (MSIS), the European Bone and Joint Infection Society (EBJIS), and the ESCMID Study Group for Implant-Associated Infections (ESGIAI). No incentive for participation was provided. Results. Amongst respondents, 22/41 were based in Europe and 10/41 from the USA. The majority (29/41) had been in clinical practice between 5—24 years. There was a high priority placed on bone biopsy histology, culture-positive bone sampling, and palpable bone without periosteal covering for diagnosis. Multidisciplinary team approach with plastic surgery involvement at the index procedure was advocated. The strongest indications for surgical intervention were source control for sepsis, presence of an abscess/collection, and prevention of local osteomyelitis progression. Physiological/psychological optimisation and control of acute infection were the primary determinants of surgical timing. There was low utilisation of adjunctive surgical therapies. Local/regional primary tissue transfer or secondary healing with/without VAC were the preferred techniques for wound closure. Recurrent osteomyelitis was the most common reason for prolonged antimicrobial therapy. The majority received bedside advice from an infectious disease-specialist but a quarter of respondents preferred telephone advice. Conclusions. Amongst an international cohort of Orthopaedic Surgeons there was a heterogenous diagnostic and therapeutic approach to pressure-related pelvic osteomyelitis

Aim. A septic revision of an artificial joint is routinely split up in a so-called dirty phase and a clean phase. The measures taken to initiate the start of the clean phase vary significantly between musculoskeletal infection centers. We performed simulations of one-step exchanges of infected THAs and sought to 1) determine the effect of different clean phase protocols on the sterile field, and 2) determine whether or not it is possible to re-implant the new prosthesis completely clean. Method. Nine fresh frozen cadaveric hips were used and primary THA was undertaken via a direct anterior approach. Before implantation of the components varying amounts of fluorescent powder (GloGerm) were deposited, simulating bacterial infection. Second, a one-step exchange was performed via a posterolateral approach. After implant removal, debridement, and lavage, randomization determined which clean phase protocol was followed, i.e. no, some or full additional measures. Finally, the new prosthesis was re-implanted (fig. 1). In order to determine the effect of different clean phase protocols on contamination of the sterile field standardized UV light-enhanced photographs were obtained of 1) the gloves, 2) the instrument table, 3) the drapes, and 4) the wound and these were ranked on cleanliness by a blind panel of hip surgeons. In order to determine whether or not it is possible to re-implant the prosthesis completely clean, the implant was taken out again at the end of the one-step exchange and inspected for contamination under UV light. Results. The gloves, the instrument table, the drapes (fig. 2) and the wound were significantly cleaner after a clean phase using full additional measures compared to partial or no additional measures (p < 0.000). Partial measures were able to reduce some of the contamination of the gloves and the wound, but had no effect on the drapes and the instrument table. All re-implanted implants were contaminated with some amount of fluorescent powder at the end of the one-step exchange. Conclusions. We advise to incorporate a clean phase with full additional measures into the surgical treatment of prosthetic joint infections, as the effect of partial measures seems to be a poor compromise. The results of this study have now been published: Vles G, Bossen J, Kloos J, Debeer P, Ghijselings S. On the value and limitations of incorporating a “clean phase” into the surgical treatment of prosthetic joint infections - an illustrative cadaveric study using fluorescent powder. J Exp Orthop. 2022 Mar 21;9(1):28. doi: 10.1186/s40634-022-00467-x

Aim. Culture negative (CN) prosthetic joint infections (PJI) account for approximately 10% of all PJIs and present significant challenges for clinicians. We aimed to explore the significance of CN PJI within a large prospective cohort study, and to compare their characteristics and outcomes with culture positive cases. Methods. The Prosthetic joint Infection in Australia and New Zealand Observational (PIANO) study is a prospective, binational, multicentre observational cohort study conducted at 27 hospitals between July 2014 and December 2017. We compared baseline characteristics and outcomes of all patients with culture negative (CN) prosthetic joint infection (PJI) from the PIANO cohort with culture positive (CP) cases. “Treatment success” was defined as absence of clinical or microbiological signs of infection, no need for ongoing antibiotics, and no need for revision or resection arthroplasty since the end of the initial treatment. We also describe PJI diagnostic criteria in the CN cohort and apply internationally recognised PJI diagnostic guidelines. Results. Of the 650 patients eligible for inclusion, 55 (8.5%) were CN and 595 were CP. Compared with the CP cohort, CN patients were more likely to be female [32 (58.2%) vs 245 (41.2%); p=0.02], involve the shoulder joint [5 (9.1%) vs. 16 (2.7%); p=0.03] and have a lower mean C-reactive protein (142 mg/L vs. 187 mg/L; p=0.02). Overall, outcomes were superior in CN patients, with culture negativity an independent predictor of treatment success at 24 months (aOR 3.78; 95%CI 1.65 – 8.67). Of the 55 CN cases meeting Infectious Diseases Society of America (IDSA) diagnostic criteria, 45 (82%) met European Bone and Joint Infection Society (EBJIS) criteria (probable or definite) and 39 (71%) met the 2013 Musculoskeletal Infection Society (MSIS) criteria. Conclusions. Culture negativity is an independent predictor of treatment success in PJI. It is unclear whether this is because some of them are not actually infections, or for other reasons such as lower bacterial load or earlier effective antibiotic treatment. Diagnostic criteria for PJI vary substantially in their sensitivity, with MSIS criteria being the least sensitive. Acknowledgements. This work is being presented on behalf of the broader PIANO investigators and the Australasian Society for Infectious Diseases Clinical Research Network. The PIANO study received seed funding from Heraeus Medical and the John Hunter Hospital Charitable Trust Fund

Aim. Whether laminar airflow (LAF) in the operating room (OR) is effective for decreasing periprosthetic joint infection (PJI) following total joint arthroplasty (TJA) remains a clinically significant yet controversial issue. This study investigated the association between operating room ventilation systems and the risk of PJI in TJA patients. Method. We performed a retrospective observational study on consecutive patients undergoing primary total knee arthroplasty (TKA) and total hip arthroplasty (THA) from January 2013-September 2017 in two surgical facilities within a single institution, with a minimum 1-year follow-up. All procedures were performed by five board-certified arthroplasty surgeons. The operating rooms at the facilities were equipped with LAF and turbulent ventilation systems, respectively. Patient characteristics were extracted from clinical records. PJI was defined according to Musculoskeletal Infection Society criteria within 1-year of the index arthroplasty. A multivariate logistic regression model was performed to explore the association between LAF and risk of 1-year PJI, and then a sensitivity analysis using propensity score matching (PSM) was performed to further validate the findings. Results. A total of 6,972 patients (2,797 TKA, 4,175 THA) were included. The incidence of PJI within 1 year for patients from the facility without laminar flow was similar at 0·4% to that of patients from the facility with laminar flow at 0·5%. In the multivariate logistic regression analysis, after all confounding factors were taken into account, the use of LAF was not significantly associated with reduction of the risk of PJI. After propensity score matching, there was no significant difference in the incidence of PJI within 1 year for patients between the two sites. Conclusions. The use of LAF in the operating room was not associated with a reduced incidence of PJI following primary TJA. With an appropriate perioperative protocol for infection prevention, LAF does not seem to play a protective role in PJI prevention

Aim. There have been many attempts to define the criteria by which prosthetic joint infection (PJI) is diagnosed. Our aim is to validate the 2021 European Bone and Joint Infection Society (EBJIS) definition of PJI. Method. This is a multicenter retrospective study of patients who have undergone total hip or knee revision surgery in four different European institutions between 2013–2018. Cases with less than four intraoperative microbiology samples; no preoperative/intraoperative synovial fluid differential leukocyte count or intraoperative histology were excluded. Minimum follow-up of at least two years after revision surgery if no subsequent infection and/or the need for implant removal was also required. All cases were classified using the 2021 EBJIS, the 2018 International Consensus Meeting (ICM) and the 2013 Musculoskeletal Infection Society (MSIS) PJI definitions. Results. Definitive PJI classification according to the different definitions of the 507 patients included are presented in table 1. The EBJIS definition classifies 40.4%(205/507) of the cases as confirmed infections compared to 33.9%(p=0.038) and 29.4%(p<0.001) in 2018 ICM and 2013 MSIS classifications respectively. Compared to 2018 ICM classification it also offers significantly less undetermined cases – 5.0% vs. 11.4%(p<0.001). Free from infection Kaplan-Meyer survival curve shows significantly better outcome for EBJIS unlikely compared to confirmed subgroup(p=0.031). EBJIS likely subgroup survival is not significantly different from unlikely(p=0.529) or confirmed(p=0.717) cohorts. Among the MSIS not infected cohort the newly classified EBJIS confirmed/likely cases present higher subsequent infection rate (albeit not statistically significant) when compared to EBJIS infection unlikely cases − 16.0%(13/81) vs. 10.1%(28/277). This subsequent PJI rate is similar to the MSIS infected cohort. A similar trend is not obvious within ICM 2018 not infected subgroup. Conclusions. The EBJIS 2021 definition is shown to be the most sensitive definition while also offering a smaller number of undetermined cases. Newly diagnosed infections seem to have a similar prognosis as “classically” infected cases. For any tables or figures, please contact the authors directly

Aims. The International Consensus Meeting on Musculoskeletal Infection (ICM, Philadelphia 2018) recommended histology as one of the diagnostic tests although this is not routinely used in a number of UK hospitals. This study aims to explore the role of histology in the diagnosis of infection and whether it is of practical use in those cases where the microbiology samples are either diagnostically unclear or do not correspond to the pre-operative diagnosis or the clinical picture. Patients and Methods. We identified 85 patients who underwent revision knee arthroplasty for either septic or aseptic loosening and for whom both microbiology and histology samples were taken. The procedures were performed by the senior experienced surgeons specialised in revision knee arthroplasty in two centres from Liverpool. Each patient had a minimum of five tissue samples taken, using separate knife and forceps and each sample was divided in half and sent for microbiology and histology in different containers. Fifty-four patients (63.5%) underwent a single-staged revision; ten patients (11.8%) underwent the 1. st. stage of a two staged revision; eleven patients (12.9%) underwent the 2. nd. stage of a two staged revision; one patient (1.2%) underwent an additional revision stage; three patients (3.5%) were treated with a DAIR; three patients (3.5%) had a 2-in-1 revision; two patients (2.4%) had a debridement and polyethylene exchange; and one patient (1.2%) had an arthroscopy biopsy of knee replacement. The cost to process five microbiology samples for each patient was £122.45 on average and for the five histology samples was £130. Results. In 63.5% (n=54) the histology and microbiology confirmed an aseptic joint as suspected beforehand. In 8.2% (n=7) the histology result was the same as the microbiology result confirming infection as suspected beforehand. In 15.3% (n=13) where asepsis was suspected beforehand, one of the five microbiology samples unexpectedly grew an organism but all the histological samples showed no evidence of infection. In these cases, the histology result supported the diagnosis of the likelihood of a contaminant. In 5.9% (n=5) we found differences in the microbiology and histology in one sample and in 7.1% (n=6) the histology was different to the microbiology in more than one sample. Conclusions. In cases where the diagnosis of sepsis within a knee replacement is not in doubt due to pre-operative microbiology, we found no benefit in additional histology sampling. In 28.3% of the cases, the histology was of use in the diagnosis of infection in complex cases and a useful tool in the decision process for further management. In over half of the cases where the revision was for aseptic loosening, the histology result did not alter the management but 28.3% of cases that were thought to be aseptic, microbiology revealed at least one positive sample hence the histology was of use in making a final diagnosis, be that of infection, contamination or to rule out infection. Whilst histology is of use in the latter groups but not the aseptic group, these outcomes are not predictable until after the post-operative period hence histology is required in all these cases. Overall, the histology is a cheap test which is of benefit in the diagnosis of complex peri-prosthetic joint infection in one–third of cases and we support the ICM recommendation