Objectives. Preclinical data showed poly(methyl methacrylate) (PMMA) loaded with microsilver to be effective against a variety of bacteria. The purpose of this study was to assess patient safety of PMMA spacers with microsilver in prosthetic hip infections in a prospective cohort study. Methods. A total of 12 patients with prosthetic hip infections were included for a three-stage revision procedure. All patients received either a gentamicin-PMMA spacer (80 g to 160 g PMMA depending on hip joint dimension) with additional loading of 1% (w/w) of microsilver (0.8 g to 1.6 g per spacer) at surgery 1 followed by a gentamicin-PMMA spacer without microsilver at surgery 2 or vice versa. Implantation of the revision prosthesis was carried out at surgery 3. Results. In total, 11 of the 12 patients completed the study. No argyria or considerable differences in laboratory parameters were detected. Silver blood concentrations were below or around the detection limit of 1 ppb in ten of the 11 patients. A maximum of 5.6 ppb at 48 hours after implantation of the silver spacer, which is below the recommended maximum level of 10 ppb, was found in one patient. No silver was detected in the urine. Drainage fluids showed concentrations between 16.1 ppb and 23.3 ppb at 12 hours after implantation of the silver spacers, and between 16.8 ppb to 25.1 ppb at 48 hours after implantation. Pathohistological assessment of the periprosthetic membrane did not reveal any differences between the two groups. Conclusion. Microsilver-loaded gentamicin-PMMA spacers showed good biocompatibility and the broad antimicrobial activity warrants further clinical research to assess its effectivity in reducing infection rates in prosthetic joint infection. Cite this article: V. Alt, M. Rupp, K. Lemberger, T. Bechert, T. Konradt, P. Steinrücke, R. Schnettler, S. Söder, R. Ascherl. Safety assessment of microsilver-loaded poly(methyl methacrylate) (PMMA) cement spacers in patients with prosthetic hip infections: Results of a prospective cohort study. Bone Joint Res 2019;8:387–396. DOI: 10.1302/2046-3758.88.BJR-2018-0270.R1

Introduction and Aims: Official governmental data indicates that infection rates for hip and knee replacement vary between zero and eight percent between institutions with and average rate of between one and two percent. Despite an apparent increase in our understanding of infection and increased use of antibiotics, decontamination and surgical technology infection remains a major problem, accounting for up to 10% of all revision procedures. The aim of this paper is to review where infection comes from, what turns a contamination into an infection and how infection can be avoided. Method: The organisms causing contamination of 125 primary joint replacements have been studied prospectively and compared to the organisms found at 334 revisions for deep infection. The antibiotic sensitivities, virulence and genetic ability to produce biofilms have been studied. The use of pre-operative screening for MRSA in 9000 patients undergoing elective surgery is compared to 2500 microbiological specimens taken for possible infection during the same time period to assess the importance of MRSA in prosthetic infection. The genetic susceptibility to infection, relationship between post-operative pyrexia and deep prosthetic infection and the use of blood transfusion and infection is investigated. Results: At least 70% of all primary joint replacements are contaminated with bacteria. The commonest contaminant is Staph. epidermidis, which is the commonest organism causing deep infection. The Staph. epidermidis causing deep infection is genetically a much stronger producer of biofilms than other strains of Staph. epidermidis. Five percent of the contaminating Staph. epidermidis is multi-resistant to antibiotics and is not susceptible to routine antibiotic prophylaxis. In our institution all elective patients are screened for MRSA. One percent of patients are carriers. Deep infection with MRSA is uncommon, with MRSA accounting for less than 2% of cases, however infection with Staph. epidermidis is the most common accounting for 60% of all infection, but of concern is that 55% of all infecting Staph. epidermidis is methicillin-resistant. The organism of concern is therefore MRSE not MRSA. Post-operative pyrexia actually protects against infection. The temperature charts of 40 patients who subsequently developed deep infection when compared to the charts of 200 patients without deep infection indicates that a low post-operative temperature is associated with an increased risk of infection, possibly indicating depressed immunity. Post-operative blood transfusion in 100 patients is shown to decrease immunity and increase nosocomial infection and wound healing problems, indicating that the immune modulation at the time of surgery is probably a major factor in post-operative infection. Finally, comprehensive genetic studies in patients undergoing long-term follow-up at Wrightington indicate definite genetic susceptibility to deep infection in certain patient groups. Conclusion: We do not understand prosthetic infection. We screen and worry about the wrong organisms, we wrongly worry about post-operative pyrexia, we increase the susceptibility of our patients to infection by blood transfusion and give the wrong antibiotics. We may be able to completely avoid infection if we redirect our efforts and stop relying on powerful broad spectrum antibiotics alone

Deep prosthetic infections are a significant cause of failure after arthroplastic surgery. Superficial wound infections are a risk factor for deep infections. We aimed to quantify the risk of deep infection after superficial wound infections, and analyse the microbiology of organisms grown. We defused Superficial Infection according to the definition used by the Centre for Disease Control, and Deep Infection according to the Swedish Hip Register. We retrospectively analysed the results of 6782 THR and TKRs performed consecutively from 1988–1998. We analysed patient records, radiology and microbiological data. The latter collected prospectively by our infection control team. We identified 81 (1. 2%) superficial wound infections, however we had to exclude 3 due to poor follow-up. Of the 78 patients studied, mean age was 71 (23–89), 50 were female, 28 male, 41 THR, 37 TKR and follow-up was a mean 49 months (12–130). The majority (81%) of organisms grown in the superficial wound infections were gram positive Staphylococci. These organisms were most frequently sensitive to Erythromycin or Flucloxacillin. All the superficial infections were treated with antibiotics, 66% settled with less than 6 weeks therapy. Deep prosthetic infections occurred in 10% of superficial infections in both THR and TKR. In 80% of cases the organism in the superficial infection caused the deep infection. Wound dehiscence, haematoma, post-op pyrexia and patient risk factors had no affect on onset of deep infection. However patients who had a wound discharge with positive microbiology and those patients in whom there was clinical doubt about the diagnosis of deep infection and thus had antibiotic therapy for more than six weeks had increased risk of deep sepsis

Aim. To review the outcome of deep prosthetic infection in patients following hip hemiarthroplasty surgery. Method. A retrospective case-note analysis was performed of deep infection coded hip hemiarthroplasty patients between 2004–2009. Patients were selected when there was proven microbiology from deep wound swabs or tissue specimens. Results. Deep infection developed in 14 of 1428 hemiarthroplasties. The mean age at time of fracture was 83 (71–93). There was a 12:2 female to male ratio. Eleven of the 14 cases had an American Society of Anaesthesiologists (ASA) score of three or four. Eight infections were due to Staphylococcus aureus, of which 6 were due to MRSA, which accounted for 43% of infections overall. There was no significant correlation between pathogen and success of treatment. Eight of the 14 hips were treated with open debridement and washout with implant retention. This was successful in 4 hips (50%). Infection recurred in 4 hips, one of which was revised to total hip replacement. The remaining 3 hips with recurrent infection were treated with excision arthroplasty. Three of the 14 hips were treated initially with excision arthroplasty. One required a further debridement and another required 3 debridements to control infection following implant removal. In 2 hips, a single stage revision to total hip replacement was performed. One of these developed recurrent infection, which was treated successfully with open debridement and washout. In one hip, no further surgery was performed. The 90-day mortality for patients with infected hemiarthroplasty was 36%. Conclusion. Deep infection following hemiarthroplasty of the hip has serious consequences and high mortality at 90 days. In our study sample, recurrence of infection was common and at least half required multiple operations. This study highlights the importance of infection prevention to reduce the morbidity and mortality following hip fracture surgery

Introduction and Objectives: Culture of periprosthetic tissue is the diagnostic treatment of reference in prosthetic infection (sensitivity 65–94%). The use of ultrasound to detach microorganisms attached to the implant may increase sensitivity. Materials and Methods: We prospectively cultured in different media the ultrasound product of the implants (knee prosthesis, hip, osteosynthesis material (OM) and spine plates and screws) extracted in our center and we obtained 3–5 samples of periimplant tissue to cultivate in each case. The gold standard was the presence of pus, fistulas, acute inflammatory tissue in the histological study or presence of positive cultures with clinical concordance. We also assessed the use of antibiotics prior to surgery. Results: We assessed 153 cases. Infections: 11 hip, 16 knee, 16 OM and 7 spine plates and screws. Conventional technique: there was a sensitivity of: 63% in hip prosthesis, 56% in knee, 81% OM and 71% in spinal plates and screws with a specificity of 94%, 100%, 98% and 100% respectively. With the use of ultrasound: there was a sensitivity of: 90% hip, 87% knee, 93% OM and 100% spine plates and screws. Specificity: 94%, 100%, 92% and 80% respectively. 13 patients received preoperative antibiotic treatment. With the use of ultrasound 10 were detected, with cultures 7. Both techniques were compared using the Fisher test. Ultrasound was more sensitive when a global prosthetic culture was done (p< 0.001) and in knee prosthesis (p< 0.04). No differences were seen with other implants. Discussion and Conclusions: Culture after ultrasound had been applied was seen to be more sensitive than culture of conventional tissue. The use of ultrasound was more effective in patients that received prior treatment with antibiotics

Introduction: etiology of late infection after arthroplasty can be difficult to establish. Histology is the gold standard for infection in patients without inflammatory arthritis but diagnosis in inflammatory arthritis depends on culture (Atkins et al). Real-time PCR offers a rapid and direct assessment for staphylococci and enterococci infection but has not been widely assessed. The aims of this study were. to develop the Roche lightcycler Staphylococcal and Enterococcal PCR kits to facilitate diagnosis of hip and knee prosthetic infections. To analyse results together with bacteriological and histological findings. Methods: uplicate, multiple tissue samples were taken (with separate sterile instruments) at the 1. st. stage of revision after informed consent. One set were cultured and results interpreted by the Oxford criteria. The second set were extracted using the Qiagen DNA kit, purified (in-house method) and tested using the Roche lightcycler kits. Results:53 patients undergoing 2 stage revision for suspected infection were recruited.15 (28.3%) had negative histology and no inflammatory arthritis; 3 with single positive cultures and negative PCR – considered contaminants. 29 patients had non-inflammatory arthritis. 14/18 (77.8%) with positive cultures had staphylococci +/or enterococci isolated and 10 PCR results correlated. The other 11 patients had negative cultures. 9 patients had inflammatory arthritis. Six were culture negative and of the other three, 2 were positive for staphylococci on culture with 1 positive by PCR. Discussion: Negative staphylococcal PCR correlates with the isolation of staphylococci from only one sample. This agrees with the Oxford criteria that such samples may be considered contaminants. Additional positives detected by staphylococcal PCR alone are rare. Enterococcal PCR confirmed culture positivity in 2/3 patients. An additional 5 positive PCR’s were obtained from patients’ culture negative for enterococci. It is not clear if these are false positives or more sensitive detection of enterococcal isolation

Aims. Periprosthetic hip-joint infection is a multifaceted and highly detrimental outcome for patients and clinicians. The incidence of prosthetic joint infection reported within two years of primary hip arthroplasty ranges from 0.8% to 2.1%. Costs of treatment are over five-times greater in people with periprosthetic hip joint infection than in those with no infection. Currently, there are no national evidence-based guidelines for treatment and management of this condition to guide clinical practice or to inform clinical study design. The aim of this study is to develop guidelines based on evidence from the six-year INFection and ORthopaedic Management (INFORM) research programme. Methods. We used a consensus process consisting of an evidence review to generate items for the guidelines and online consensus questionnaire and virtual face-to-face consensus meeting to draft the guidelines. Results. The consensus panel comprised 21 clinical experts in orthopaedics, primary care, rehabilitation, and healthcare commissioning. The final output from the consensus process was a 14-item guideline. The guidelines make recommendations regarding increased vigilance and monitoring of those at increased risk of infection; diagnosis including strategies to ensure the early recognition of prosthetic infection and referral to orthopaedic teams; treatment, including early use of DAIR and revision strategies; and postoperative management including appropriate physical and psychological support and antibiotic strategies. Conclusion. We believe the implementation of the INFORM guidelines will inform treatment protocols and clinical pathways to improve the treatment and management of periprosthetic hip infection. Cite this article: Bone Jt Open 2023;4(4):226–233

Aims

Methicillin-resistant Staphylococcus aureus (MRSA) can cause wound infections via a ‘Trojan Horse’ mechanism, in which neutrophils engulf intestinal MRSA and travel to the wound, releasing MRSA after apoptosis. The possible role of intestinal MRSA in prosthetic joint infection (PJI) is unknown.

Introduction: Infection is a challenging problem in orthopaedic surgery. In oncologic and revision surgery large prosthesis are placed during long procedures, even in patients with immunocompromised status. Infection rates here are reported up to 10%. Infections may necessitate large segmental resections thereby creating large defects. This defect can be filled with antibiotics loaded beads that release the substances locally to sterilise the defect. In recent years solid antibiotic loaded bone cement spacers have been applied. These spacers fill the defect, stabilize the extremity, release antibiotics and keep the soft tissues on their original length. Additionally, the patients will be able to preserve mobile function as well. In small defects prefabricated bone cement spacers temporarily replace the infected hip or knee prosthesis. For larger segmental of terminal defects there are no readily available constructs. Purpose: To report short term outcome of a newly developed customized spacer concept for treatment of large segmental resections after prosthetic infection or osteomyelitis. Material and Methods: We have treated 13 patients with large segmental defects after infection treatment with customized antibiotic bone cement spacers reinforced with strong intra-medullar implants like the Gammanail, the DFN and the UHN. Results: These customized spacers are easy to make, fill the defect, stabilize the extremity, release antibiotics, keep the length of the soft tissues and allow patients to practice and preserve joint function as well. In 11 of 13 patients operated with an interim construct like this, a successful reimplantation of a tumor prosthesis was performed. Conclusion: With customized antibiotic bone cement spacers augmented with a solid implant one can fill the defect, stabilize the extremity, release antibiotics and keep the soft tissues on their original length and keep function as well in infected tumorprosthesis. Successful reimplantation could be performed in 11 of 13 cases

Introduction. Debridement, antibiotics, and implant retention (DAIR) for acute prosthetic hip infection is a popular low morbidity option despite less than optimal success rates. We theorized that the delay between DAIR and explantation in failed cases may complicate eradication due to biofilm maturation and entrenchment of bacteria in periprosthetic bone. We ask, what are the results of two-stage reimplantation after a failed DAIR versus an initial two-stage procedure?. Methods. 114 patients were treated with 2-stage exchange for periprosthetic hip infection. 65 were treated initially with a 2-stage exchange, while 49 underwent an antecedent DAIR prior to a 2-stage exchange. Patients were classified according to MSIS host criteria. Failure was defined as return to the OR for infection, a draining sinus, or systemic infection. Results. Treatment failure occurred in 42.9% (21 of 49) of patients treated with an antecedent DAIR. In contrast, treatment failure occurred in only 12.3% (8 of 65) of initial 2-stage procedures (p< 0.001). Relative Risk of return to the OR after a 2-stage reimplantation with an antecedent DAIR compared to initial resection was 4.52 (95% CI 1.71, 11.9). MSIS host grading was similar between groups and did not influence the rate of failure. The DAIR cohort had increased hospitalization length and greater number of operative procedures (p< 0.001). Conclusion. We have shown that if irrigation and debridement fails to treat acute prosthetic hip infection, subsequent attempts at two-stage reimplantation may be compromised. Additionally, in the antecedent DAIR group, the average number of infection-related procedures (5) was nearly twice that of those initially resected (2.7). This by nature implies a significantly greater burden to the patient and cost to the healthcare system

Hip prosthetic joint infection (PJI) is a debilitating complication following joint replacement surgery, with significant impact on patients and healthcare systems. The INFection ORthopaedic Management: Evidence into Practice (INFORM:EP) study, builds upon the 6-year INFORM programme by developing evidence-based guidelines for the identification and management of hip PJI.

A panel of 21 expert stakeholders collaborated to develop best practice guidelines based on evidence from INFORM \[1\]. An expert consensus process was used to refine guidelines using RAND/UCLA criteria. The guidelines were then implemented over a 12-month period through a Learning Collaborative of 24 healthcare professionals from 12 orthopaedic centres in England. Qualitative interviews were conducted with 17 members of the collaborative and findings used to inform the development of an implementation support toolkit. Patient and public involvement contextualised the implementation of the guidelines. The study is registered with the ISCRTN (34710385).

The INFORM guidelines, structured around the stages of PJI management, were largely supported by surgeons, although barriers included limited awareness among non-surgical team members, lack of job planning for multidisciplinary teams, and challenges in ensuring timely referrals from primary care. Psychological support for patients was identified as a critical gap. Advanced Nurse Practitioners and multidisciplinary team (MDT) coordinators were seen as potential bridges to address these knowledge gaps. The guidelines were also viewed as a useful tool for service development.

This study presents the first evidence-based guidelines for hip PJI management, offering a comprehensive approach to prevention, treatment, and postoperative care. Effective implementation is crucial, involving wider dissemination amongst primary and community care, as well as non-specialist treatment centres. Further resources are needed to ensure job planning for MDTs and psychological support for patients. Overall, this study lays the foundation for improved PJI management, benefiting patients and healthcare systems.

Prosthetic joint infection (PJI) is an uncommon but serious complication of hip replacement. Over 1,000 operations are performed annually in the United Kingdom for PJI following hip replacement, using either one- or two-stage revision arthroplasty. It is unclear which is preferred by patients and which has the best long-term outcome. This qualitative study aims to describe patient experiences of treatment and recovery following one- and two-stage revision arthroplasty for PJI within the context of a pragmatic randomised controlled trial comparing these two approaches. Semi-structured interviews were conducted with 32 patients undergoing one- or two-stage revision treatment for PJI as part of a UK multi-centre randomised controlled trial. Patients were recruited from 12 participating National Health Service (NHS) Orthopaedic Departments and were interviewed 2–4 months after their first revision surgery and again approximately 18 months later. Final sample size was justified on the basis of thematic saturation. All patients consented to the interview being audio-recorded, transcribed, anonymised and analysed using an inductive thematic approach. Ethical approval was provided by NRES Committee South-West Frenchay, 14/SW/116. Patients in both the one- and two-stage treatment groups described prolonged hospital stays, with burdensome antibiotics and brief physiotherapy treatment. However, following discharge home and during recovery, participants undergoing two-stage revision with an ‘empty hip' or with a spacer reported being physically restricted in almost every aspect of their daily life, resulting in inactivity and confinement to home. Mobility aids were not sufficiently available through the health service for these patients. A key difference is that those with a spacer reported more pain than those without. Approximately one year following their second-stage revision, participants described being more independent and active, but two directly attributed muscle weakness to the lengthy period without a hip and described resulting falls or dislocations that had complicated their recovery. In contrast, those undergoing one-stage revision and CUMARS appeared to be more alike, reporting better mobility, functionality and independence, although still limited. Participants in these groups also reported minimal or no pain following their revision. A key difference between CUMARS and one-stage revision was the uncertainty of whether a second operation was necessary, which participants described as “hanging over them”, while those in the two-stage empty hip or spacer group described a more positive anticipation of a second definitive operation as it marked an end to what was described as a detachment from life. Our findings highlight the differences between patient experiences of recovery following revision arthroplasty, and how this is influenced by the surgical approach and presence or lack of spacers. An understanding of lived experiences following one- and two-stage surgical interventions will complement knowledge about the clinical effectiveness of these different types of revision surgery.

Introduction

Two-stage reimplantation for prosthetic joint infection (PJI) of the hip is the standard of care with a 5–10% recurrence at a minimum two-year follow-up. Compiling outcomes data for this standard of care is necessary in order to characterize long-term reinfection risk and the culpable microbiology. The purpose of this study was to determine the long-term success of two-stage reimplantation and identify the factors that affected the success.

Infection after total hip arthroplasty is a rare but potentially devastating complication. The most common pathogens responsible for these infections are gram positive bacteria. Infection caused by fungi is uncommon. There are few reports of prosthetic joint infection caused by Candida species, and there has no report of implant preservation.

We experienced the case of a patient with Candida arthritis who underwent total hip arthroplasty for hip arthrosis, and successfully could preserved prosthetic joint.

A 60 year-old woman underwent total hip arthroplasty in September 2014. She had had the past of sepsis by the Candida after surgery of the duodenal cancer. After four weeks in total hip arthroplasty, she made clinic visits. Her chief complaints were low-grade fever of 1 week's duration and discharge from operative scar for THA. The patient underwent arthrocentesis of the left hip. The culture was positive for Candida tropicalis.

Operation of surgical debridement and liner change was performed as soon as possible. After operation, the patient was treated with fluconazole intravenously for 28 days.

She has continued to taken fluconazole by mouth. Reactivation of infection have not been in her left hip.

We reported the case of a patient with Candida arthritis who underwent total hip arthroplasty. Prosthetic joint could have preserved because of early detection for infection. This is the first report of preservating implant after Candida infection in total hip arthroplasty.

Introduction: The incidence of tuberculosis has increased by almost 30% annually in the UK. Orthopaedic surgeons are more likely to encounter patients affected with Mycobacterium tuberculosis [MTB]. We have reviewed the surgical and medical management of cases of MTB infecting prosthetic hip joints in patients without previous tuberculosis.

Report: A 59 year old Caucasian woman presented to us with apparent osteoarthritis hip. X-rays confirmed osteoarthritis but also revealed a lytic lesion in the greater trochanter and erosion of the superior cortex of the femoral neck. The patient had no prior history of exposure to tuberculosis and no evidence of pulmonary or osteoarticular tuberculosis. The patient was investigated preoperatively with blood tests, bone scan, CT scan, CT guided FNAC, and core biopsy. None of these showed any specific diagnostic features. She underwent a total hip replacement and was asymptomatic up to 15 months post-op when she presented with pain in the joint with an abscess over the gluteal region. The abscess was drained and special media culture grew MTB. We used 4-drug therapy for 12 months with retention of the prosthesis and a good functional result.

Discussion: Infected total hip replacement presents a management challenge and surgeons should have a high index of suspicion for Tuberculosis in recalcitrant infections where smears from infected joints are negative. The infection of a total hip replacement with MTB in patients without previous tuberculosis is very uncommon. Only 12 cases have been reported in a search of English language literature from 1966–2005.

We have analysed the wide variation in the management of these cases. The majority of authors in our review resected or revised the infected prosthesis. We are of the opinion that if the infection is clinically under control and the prosthesis is stable, medical treatment alone should suffice.

Aim. Despite the availability of numerous tests, the diagnosis of periprosthetic infection (PJI) continues to be complex. Although several studies have suggested that coagulation-related markers, such as D-dimer and fibrinogen, may be promising tools in the diagnosis of prosthetic infections, their role is still controversial. The aim of this study is to evaluate the diagnostic accuracy of serum D-dimer and fibrinogen in patients with painful total knee replacement. Method. 83 patients with painful total knee replacement and suspected peri-prosthetic infection were included. All patients underwent pre-operative blood tests to evaluate inflammation indices (ESR and CRP) and serum D-Dimer and Fibrinogen levels. The diagnostic performance of the tests was assessed using the ICM definition as the gold standard. The diagnostic accuracy of the D-dimer and fibrinogen was measured by assessing sensitivity, specificity and by calculating the area under the ROC curve. Results. The definition of prosthetic infection based on the ICM criteria has made it possible to classify 40 peri-prosthetic infections and 43 aseptic failures. The mean value of fibrinogen, D-Dimer, VES and PCR observed in patients with prosthetic infection was significantly higher than in patients with aseptic failure [fibrinogen 468 mg / dl vs 331 mg / dl, p <0.001; D-Dimero 2177 ng/mL vs. 875 ng / mL, p <0.005], ESR 49 mm / hr vs 24 mm/h, p <0.001; PCR 25.5 mg /L vs 8.9 mg/L, p <0.001]. The optimal threshold value of the fibrinogen indicative of the presence of infection was 418 mg/dl, with a sensitivity of 72% and a specificity of 88%. The serum concentration of d-dimer greater than 945 ng / ml showed a sensitivity of 72.5% and a specificity of 76.7%. Conclusions. Although in this multicenter prospective study we found that serum D-dimer may have significantly higher statistical values in PJI than aseptic failures, its diagnostic power appears however limited when compared with other markers including plasma fibrinogen. Fibrinogen is regularly analyzed before surgery, the evaluation of this marker does not involve additional costs. The diagnostic accuracy appears to be similar to that of classic markers such as the level of PCR and VES. Plasma D-dimer may have a limited value in the diagnosis of PJI unlike plasma fibrinogen which has shown moderate sensitivity and excellent specificity. However, in our limited series of cases, both tests cannot be used alone in the diagnosis of infection but could contribute to the diagnosis if contextualized to ves and pcr

Abstract. Introduction. The rate of day-case total knee replacement (TKR) in the UK is currently ~0.5%. Reducing length of stay improves efficiency, increases operative throughput and tackles the rising demand for joint replacement surgery and the COVID-19 related backlog. We report safe delivery of day-case TKR in an NHS Trust via inpatient wards, with no additional resources. Methodology. Day-case TKRs, defined as patients discharged on the same calendar day as surgery, were retrospectively reviewed with a minimum follow-up of six-months. Analysis of hospital and primary care records was performed to determine readmission and reattendance rates. Telephone interviews were conducted to determine patient satisfaction. Results. Between 2016 and 2021, 301/7350 (4.1%) TKRs were discharged on the day of surgery. Mean follow-up was 31.4 (6.2–70.0) months. 28 (9.3%) patients attended Accident and Emergency or other acute care settings within 90-days of surgery; six (2.0%) patients were readmitted. No patients underwent a subsequent revision procedure. There were no prosthetic infections. Two patients underwent secondary patella resurfacing, and one patient underwent arthroscopic arthrolysis after previous manipulation under anaesthetic (MUA). Three patients underwent MUA alone. Primary care consultation records, available for 206 patients, showed 16 (7.8%) patients contacted their General Practitioner within two-weeks post-operatively; two (1.0%) were referred to secondary care. 115/121 (95%) patients telephoned stated they would have day-case TKR again. Conclusion. Day-case TKR can be safely delivered in the NHS with no additional resources. We found low incidence of contact with primary and secondary care in the post-operative period, and high patient satisfaction

Aim. Prosthetic joint replacement is more commonly done in the elderly group of patients due to an increase pathology related to joint degeneration that comes with age. In this age group is also more frequent having underling condition that may predispose to a prosthetic joint infection. Also, the pharmacological intervention in those patients may play an important role as a risk factor for infection after joint replacement surgery. The use of oral anticoagulants seems to be particularly increased in elderly patients but there aren't enough data published to support an association between prosthetic joint infection and the use of oral anticoagulants. Identifying risk factors in elderly patients age >75 years old with a special focus on the oral anticoagulation therapy is the aim of the study. Methods. In a retrospective study from 2011 till 2018 all the patients >75 years old with knee and hip replacement surgery have been review looking for acute prosthetic infection and risk factors that may be predispose to it. Patients with previous surgery or any other mechanical complication that needed intervention on the same area have been excluded. Results. A total of 1220 patients have been included (801 knee replacement surgery and 419 hip replacement surgery). The mean age was 79.5 ± 3.44 years and most of the patients were women (72,6%). The infection rate was 2,5%. Several factors have been identified to be associated with acute infection. (Table.1.). The patients receiving oral anticoagulants had an increased risk of infection (OR 3.63 (1.60–7.74), p=0.002). Conclusions. Even all the risk factors associated with risk infection have been described previously, the relevant aspect is the increased risk of prosthetic joint infection in patients receiving oral anticoagulants

Gram-negative prosthetic joint infections (GN-PJI) present unique challenges in management due to their distinct pathogenesis of biofilm formation on implant surfaces. To date, there are no animal models that can fully recapitulate how a biofilm is challenged in vivo in the setting of GN-PJI. The purpose of this study is to establish a clinically representative GN-PJI in vivo model that can reliably depict biofilm formation on titanium implant surface. We hypothesized that the biofilm formation on the implant surface would affect the ability of the implant to be osseointegrated. The model was developed using a 3D-printed, medical-grade titanium (Ti-6Al-4V), monoblock, cementless hemiarthroplasty hip implant. This implant was used to replace the femoral head of a Sprague-Dawley rat using a posterior surgical approach. To induce PJI, two bioluminescent Pseudomonas aeruginosa (PA) strains were utilized: a reference strain (PA14-lux) and a mutant strain that is defective in biofilm formation (DflgK-lux). PJI development and biofilm formation was quantitatively assessed in vivo using the in vivo imaging system (IVIS), and in vitro using the viable colony count of the bacterial load on implant surface. Magnetic Resonance Imaging (MRI) was acquired to assess the involvement of periprosthetic tissue in vivo, and the field emission scanning electron microscopy (FE-SEM) of the explanted implants was used to visualize the biofilm formation at the bone-implant interface. The implant stability, as an outcome, was directly assessed by quantifying the osseointegration using microCT scans of the extracted femurs with retained implants in vitro, and indirectly assessed by identifying the gait pattern changes using DigiGaitTM system in vivo. A localized prosthetic infection was reliably established within the hip joint and was followed by IVIS in real-time. There was a quantitative and qualitative difference in the bacterial load and biofilm formation between PA14 and DflgK. This difference in the ability to persist in the model between the two strains was reflected on the gait pattern and implant osseointegration. We developed a novel uncemented hip hemiarthroplasty GN-PJI rat model. This model is clinically representative since animals can bear weight on the implant. PJI was detected by various modalities. In addition, biofilm formation correlated with implant function and stability. In conclusion, the proposed in vivo GN-PJI model will allow for more reliable testing of novel biofilm-targeting therapetics

Abstract Background. The treatment of bone and joint infections (BJI) involving multi-drug resistant bacteria remains a challenge. MDR Staphylococcus epidermidis (MDRSE) clones, resistant to methicillin, clindamycin, levofloxacin, rifampicin and even linezolid, have been reported worldwide. The interest of delafloxacin (DFX), theoretically active on MRSA, remains to be evaluated with respect to MDRSE. Purpose. Our objective was to evaluate during a retrospective multicenter study the DFX minimal inhibitory concentrations (MICs) and compare its efficacy between ofloxacin-susceptible and ofloxacin-resistant S. epidermidis clinical strains involved in BJI. Methods. In this multicenter retrospective study (Reference centers from the West part of France, CRIOGO), 529 strains were collected mostly from BJI. DFX MICs were determined by using a 0.5 Mc Farland bacterial inoculum on Mueller-Hinton agar plates with gradient strips incubated for 24h at 35°C. For S. aureus, breakpoints differentiate skin and soft tissue infections from other infections. Breakpoints followed 2022 EUCAST criteria, with S. aureus values adopted for S. epidermidis. Results. Of the 529 strains collected, 355 were from prosthetic infections, 159 from synthetic infections and 15 from non-device infections. 152 strains were susceptible to ofloxacin (110 males vs 42 females) and 377 resistant (210 vs 167). As presented in Figure 1, all the ofloxacin-susceptible strains presented a DFX MIC ≤0.006mg/L. Resistant strains presented a double population distribution, with 3.7% categorized susceptible according to skin and soft tissues infections breakpoint, against 88.9% according to other breakpoint infections (0.016 or 0.25mg/L respectively). Conclusion. DFX shows excellent activity against ofloxacine-susceptible strains. Concerning the ofloxacin-resistant strains, more than 80% strains or less than 10% can be considered as DFX-susceptible depending on the breakpoints used. Further clinical studies are needed to validate the real breakpoints that must be used in MDRSE BJI, allowing a microbiological cure and a favourable clinical outcome. For any tables or figures, please contact the authors directly