Infected Knee Research Articles

SG-APSIC1088: Two-stage primary total knee arthroplasty for evolutive infected arthritis with coexistent joint destruction

Objectives: The treatment of infected knee arthritis in patients with coexisting joint destruction, including superimposed advanced arthritis or chronic osteomyelitis, is challenging. We investigated the outcomes of 2-stage primary total knee arthroplasty (TKA) for evolutive infected arthritis with coexistent joint destruction. Methods: We retrospectively reviewed the cases of 50 patients from 5 hospitals who presented with infected arthritis of the knee and were treated with 2-stage TKA: debridement and antibiotic-loaded articulating cement spacer (ALCS) insertion as the first stage and TKA as the second stage. We recorded demographics, laboratory results, and radiographic findings including Kellgren-Lawrence classification (KL) for knee arthritis. Outcomes including infection eradication, knee range of motion (ROM), and patient-reported outcome measures were evaluated. Results: The patient cohort had a mean age of 71.8 years (range, 40–86); they were followed for an average of 4.1 years (range, 2.2–13.3). Also, 40 patients showed KL grade 4, whereas 10 patients showed grade 3. A pathogen was identified in 38 cases (73.1%); methicillin-resistant staphylococci infections (N = 16) and Candida spp infections (N = 7) were the 2 most common types. Constrained prostheses were used in 10 cases (20%). Stem augmentations were used in 15 cases (36.0%) and block augmentations were used in 8 cases (19.0%). One patient had recurrent infection after TKA, so the eradication rate was 98%. After 2-stage TKA, the mean knee ROM was 119.4° (range, 80°–140°) and the mean Knee Society (KS) knee score was 90.4, the average KS function score was 84.7, the average Hospital for Special Surgery (HSS) score was 87.2, and the average Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was 16.7. The KS function scores (P = .029) and the WOMAC scores (P = .022) were significantly better in 17 patients who underwent ALCS insertion within 30 days of infection diagnosis compared to the other 33 patients. Conclusions: The 2-stage primary TKA for patients with infected knee arthritis with coexisting joint destruction showed satisfactory outcomes with a low infection recurrence. However, constrained prostheses or augmentation use may be necessary. Notably, some functional scores were better in the group that underwent ALCS insertion relatively early after the infection diagnosis.

Complications and Outcomes Associated with Two-Stage Treatment of Periprosthetic Total Knee Infection

Background and Hypothesis: Periprosthetic joint infection (PJI) is treated with implant resection, debridement, and component reimplantation after infection eradication. Treatment consists of either a single surgery or two-stage surgery with intravenous antibiotic therapy between stages. We replicated a recent study which concluded two-stage treatment is associated with high morbidity, hypothesizing that complication rates would be similar, but that morbidity is not always conclusively a consequence of two-stage treatment for PJI
 Project Methods: Prospectively documented data on all primary and revision knees undergoing two-stage treatment for PJI by a single surgeon were retrospectively reviewed. Surgical complications were quantified for the interstage and post-reimplantation periods. Chi-squared tests were used to compare current findings to published findings.
 Results: Patient demographics and comorbidities were equivalent in the two studies (p ≥ .137). More complex infections characterized the current study as evidenced by significantly more polymicrobial infections (p < .001) and greater use of static spacers due to bone loss (p = .002). Nonetheless, only 1.5% of cases in the current study did not undergo component reimplantation compared to 7.8% in the comparison study (p = .129). There were no differences in the number of additional interstage and post-reimplantation septic surgeries (p ≥ .492). Using a proposed system which penalizes additional operations required to eradicate infection, treatment success rates at minimum one year follow-up were 64% and 71%, respectively (p = .473). Without these penalties, treatment success in the current study was 95.6% (equivalent proportion not available for comparison study). All-cause mortality was statistically equivalent in the two studies (15.6 versus 7.6%, p = .144) but no deaths from PJI were observed in the current study (unknown for comparison study).
 Potential Impact: Study findings suggest that morbidity attributed to two-stage treatment reflect the inherent complexity of this patient group, and not the two-stage treatment itself.

High Rate of Intramedullary Canal Culture Positivity in Total Knee Arthroplasty Resection for Prosthetic Joint Infection

BackgroundPeriprosthetic infection is a devastating complication following total knee arthroplasty. A 2-stage protocol often includes an interim antibiotic spacer with intramedullary (IM) dowels. However, the necessity of IM dowels has recently been challenged. Specifically, the data supporting bacterial colonization of the IM canal are limited and controversial. The purpose of this study was to identify the rate of positive IM cultures during resection arthroplasty in periprosthetic knee infection. MethodsA total of 66 IM diaphyseal cultures were taken during resection arthroplasty from 34 patients diagnosed with periprosthetic knee infection. These IM cultures were taken from the femoral and tibial canals using separate sterile instruments. All patients had infected primary total knee arthroplasty implants at the time of resection. ResultsThirty one percent (n = 21) of IM canal cultures in this study were positive from either the tibial or the femoral diaphysis at the time of resection arthroplasty. There were 18 of 21 (86%) of the positive IM canal cultures with concordant intraoperative joint cultures where the IM cultures matched the intraarticular cultures. ConclusionWith a 31% positive IM canal culture rate, this study confirms the logic of using IM dowels with an antibiotic spacer to treat periprosthetic knee infection. Since the failure of a 2-stage reimplantation is catastrophic, any attempt to provide additional local antibiotic delivery seems warranted. Since nearly one-third of our patients had positive IM cultures, this simple addition to an antibiotic spacer has the potential to improve 2-stage results. Claims supporting the elimination of IM dowels during resection arthroplasty seem ill-advised.

A case of cat bite associated Pasteurella multocida prosthetic joint infection

Cases of Pasteurella multocida related joint infections are often late in onset, but with the increase in prosthetic joints should be considered, especially in knee infections. Often thought of in relation to animal bites, these infections are further transmitted by nasal secretions, scratches, and licking behavior. We present a case of Pasteurella multocida joint infection in a patient who presented with a classic inciting factor of a cat bite, but presented initially with Enterococcus faecalis bacteremia, which obscured the clinical picture. This patient provides a good reminder of why all patients with cat bites and prosthesis should receive antibiotic prophylaxis post bite, as well as a good reminder to clinicians to keep P. multocida on their differential.

No difference in Oxford Knee Score between medial and lateral unicompartmental knee arthroplasty after two years of follow-up: a clinical trial

PurposeIn patients with monocompartmental knee osteoarthritis, unicompartmental knee arthroplasty (UKA) can be performed. This study compared the medial versus lateral UKA in patients with monocompartimental knee arthroplasty. It was hypothesised that both implants achieve a similar outcome in OKS.MethodsThe UKAs were fixed-bearing medial PPK (Zimmer-Biomet, Warsaw, Indiana, USA) and fixed-bearing lateral Zuk (Lima Corporate, Udine, Italy). An intraarticular drain was placed and removed on the first postoperative day. Enoxaparin sodium 4000 units subcutaneously daily for 45 days was used as thromboembolic prophylaxis. The Italian version of the OKS was used for the clinical assessment. The following complications were also recorded: anterior knee pain, infection and revision surgeries.ResultsData from 203 patients were collected. The mean age of the patients was 68.9 ± 6.7 years and the mean BMI was 28.1 ± 4.1 kg/m2. The mean OKS on admission was 22.1 ± 4.5 points. On admission, women, patients older than 70 years, and those with a BMI lower than 28 kg/m2 who underwent lateral UKA evidenced lower OKS. At the last follow-up, 26.7 and 26.9 months for the lateral and medial UKA, respectively, no between groups difference in OKS was evidenced. No patients experienced complications.ConclusionMedial and lateral UKA achieve similar outcomes in OKS at a minimum of two years of follow-up.

Two-stage revision of infected knee replacement in patients with antibiotic-loaded spacer

Two-stage revision of infected knee replacement in patients with antibiotic-loaded spacer

The local application of a calcium sulfate bone graft substitute with antibiotics for the treatment of infection after anterior cruciate ligament reconstruction. The results of 3 cases and a literature review

Introduction. We report the results of revision surgery in recurrent infection after anterior cruciate ligament reconstruction (ACLR) consisting of graft canal debridement and the local application of a calcium sulfate bone substitute (CSBS) with the addition of gentamicin and vancomycin in graft canal and infected foci. Materials and methods. Three patients (3 knees) were operated due to a chronic and unsuccessfully treated knee infection after ACLR. Two patients underwent multiple previous revisions (4 and 9, respectively). In all cases, the tibial ACL graft canal and adjacent bone foci were debrided. Post debridement defects in the femur and tibia and the graft tunnel in the tibia were filled with CSBS with an addition of gentamicin and vancomycin. If the absence of the ACL graft was stated, the tibial canal was closed from the joint side with a collagen sponge with gentamicin. Results. After a follow-up of 20 to 26 months, all patients obtained a complete resolution of inflammation and CRP normalization. No side effects related to CSBS were observed. There was no deterioration in the knee function and stability compared to the pre-revision status. Conclusions. CSBS with the addition of gentamicin and vancomycin applied in the graft canal and inflammatory foci in the surrounding cancellous bone proved to be effective and unrelated to complications in chronic infection after ACLR. Level of Evidence: IV (case series).

982. Microbiologic Composition and Failure Rates of Prosthetic Hip and Knee Infections Managed with Debridement, Antibiotics and Implant Retention.

Abstract Background Success rates of prosthetic joint infections (PJI) managed by debridement, antibiotics, and implant retention (DAIR) vary according to recent literature. Our aim is to evaluate the success/failure rate of PJI managed by DAIR with respect to the microbiologic composition, antimicrobial selection, and treatment duration. Methods A single-center retrospective cross-sectional study was conducted from January 2017 to December 2021. All patients ≥ 18 years of age who underwent DAIR were identified from an existing internal database. Patients were included if they received at least 3 weeks but no more than 8 weeks of parenteral therapy with or without consolidative or chronic therapy. Data collection was completed via chart review including demographics, microbiologic data, antimicrobial therapy and outcomes. Failure was defined as any subsequent need for surgical intervention, infection related mortality, persistent infection, new infection, or probable treatment failure measured at a minimum of two year follow up from index DAIR. Results A total of 49 patients were included (15 hip, 34 knee) with 21 failures (43%) and 28 in remission (57%). Table 1 shows the breakdown of cases including time to PJI from index procedure, duration of symptoms prior to DAIR procedure, chronic antibiotics, and microbiologic composition. DAIR procedure occurred < 3 weeks from onset of symptoms in 43 patients (88%) but no observed difference in outcomes was seen based on patient’s time to PJI or symptoms duration. Staphylococcus aureus was the most common pathogen identified, n=14 (29%) and encompassed 43% of the total failures. Mean antimicrobial therapy was 42 and 180 days for parenteral and oral respectively with 17 (35%) patients on chronic/indefinite therapy. Of the failures, 48% occurred while on parenteral therapy. Need for further surgical intervention was the leading cause of failure at 37%. Conclusion Despite early intervention, our study found a failure rate of 43% in patients with knee and hip PJI managed with DAIR. We observed similar success rates across multiple organisms and antimicrobial treatments. Further evaluation of failure cases would help to inform which patients are the best candidates for DAIR procedures. Disclosures All Authors: No reported disclosures.

The concordance between preoperative synovial fluid culture and intraoperative tissue cultures in periprosthetic joint infection: a systematic review.

Background: this systematic review aims to evaluate the concordance between preoperative synovial fluid culture and intraoperative tissue cultures in patients with periprosthetic joint infection (PJI) undergoing total hip (THA) or knee arthroplasty (TKA) revision surgery. Methods: this review was conducted in accordance with the preferred reporting items for a systematic review and meta-analysis of diagnostic test accuracy studies (PRISMA-DTA) statement. Cochrane, Embase, PubMed, and Web of Science databases were searched to identify studies involving patients who had THA or TKA revision surgery for PJI and for whom preoperative synovial fluid culture and intraoperative tissue cultures were performed. Studies were only included if the diagnosis of PJI was based on the EBJIS (the European Bone and Joint Infection Society) or MSIS (Musculoskeletal Infection Society) criteria. Risk of bias was assessed using an amended version of Joanna Briggs Institute's (JBI) critical appraisal checklist for case series. Results: seven studies were included in this review comprising 1677 patients. All studies had a retrospective study design and five studies explored patients undergoing revision surgery of THA or TKA. Concordance rates varied between 52 % and 79 %, but different authors defined and calculated concordance differently. Six studies were judged as having an unclear to high risk of bias and one study as having a low risk of bias. Conclusions: the included studies showed a wide range of concordance rates between preoperative synovial fluid culture and intraoperative tissue cultures and the majority of studies had a high risk of bias. Higher-quality studies are warranted to obtain a more accurate estimate of this concordance rate. We recommend continuing the use of a system such as the EBJIS definition or MSIS criteria when diagnosing PJI.

Internal Brace Ligament Augmentation versus Anatomical Repair with Hamstrings of the ACL – A Clinical Data Comparison Study

AIM: Investigation into the clinical results of internal brace ligament augmentation technique compared to the simple anatomical repair of the anterior cruciate ligament (ACL). METHODS: From May 2016 to November 2019, 128 patients underwent an operation using the internal brace technique. During the same time, 104 patients were operated on using the simple anatomical ACL repair. The mean age was 22.5-year-old for the first group and 26.8-year- old for the second one. The minimum follow-up was 24 months. All the patients performed an X-ray and magnetic resonance imaging. Two hypotheses were raised to assess the superiority of the internal brace technique versus the anatomical one in the early post-operative phase and the rehabilitation one. RESULTS: The mean operation time was 71 (65–75) min for the internal brace (IB) and 62 (55–65) for the anatomical. We had two post-operative infected knees in the first group (IB) and no infection in the second one. The clinical stability test results were much better in the IB group using the KT 1000. The rehabilitation phase showed a superior IB technique. The return to sport-time of the sportsmen was 6 months for the first group and 7–8 months for the anatomical. All the IB-operated patients found physiotherapy significantly easier than the anatomical ones. CONCLUSIONS: IB-technique performs better clinical outcomes than the anatomical repair. The presence of a foreign body (Ultrabraid) inside the knee may be a risk factor contributing toward the elevated infection rate. The IB technique costs are significantly more expensive compared to the anatomical but the low physiotherapy costs compensate for the final result.

The Diagnostic Accuracy of Neutrophils to Lymphocytes Ratio, Platelets to Lymphocytes Ratio, Monocytes to Lymphocytes Ratio, and Platelets to Mean Platelet Volume Ratio in Diagnosing Periprosthetic Knee Infections. Are Gender-Specific Cutoff Values Needed?

BackgroundThis study aimed to assess the most appropriate thresholds for neutrophils to lymphocytes ratio (NLR), platelets to lymphocytes ratio, monocytes to lymphocytes ratio (MLR), and platelets to mean platelet volume ratio in patients who had a suspected prosthetic knee infection. Furthermore, we evaluated the diagnostic accuracy of our proposed thresholds by men and women. MethodsA total of 261 consecutive patients affected by painful total knee arthroplasty were included. International Consensus Meeting diagnostic criteria were used to identify periprosthetic infections. Sensitivity, specificity, positive, and negative predictive values were calculated for each cutoff value obtained. The area under the receiver operating characteristic curve was evaluated. ResultsNLR reported the best diagnostic accuracy. MLR and NLR reported higher area under the curves in men and women. We obtained an MLR value ≥0.30 (optimal cutoff value for men) and ≥0.17 (optimal cutoff value for women). In men, the sensitivity and the specificity were 0.71 and 0.77, respectively, versus 0.82 and 0.29, in women. For NLR, we obtained a value ≥2.52 (best cutoff value for men) and ≥2.46 (best cutoff value for women). These cutoffs reported a sensitivity and specificity of 0.71 and 0.88 versus 0.54 and 0.76 in men and women, respectively. ConclusionThese biomarkers present a low diagnostic accuracy in periprosthetic joint infection detection. Men whose MLR and NLR were above cutoff values had a 77 and 88% probability of presenting a septic prosthetic failure. NLR of at least 2.46 was reasonably sensitive for women who have a periprosthetic knee infection. Level of EvidenceDiagnostic study, Level II.

Low dose vancomycin-loaded spacers for two-stage revision knee arthroplasty: High success, low toxicity

BackgroundTwo-stage revision arthroplasty is a widely used treatment method for infected knee arthroplasty. Loading high doses of antibiotics to spacer during the first stage is standard practice. However, there are reported systemic side effects attributed to antibiotic-loaded spacers. The aim of our study is to investigate the success rate and systemic toxicity following the first stage revision knee arthroplasty with low-dose vancomycin-loaded spacers. MethodWe included patients with infected knee arthroplasty eligible for two-stage revision arthroplasty from 2001 to 2020. One gram of vancomycin is added per pack of bone cement. Spacers were handmade in the operating theatre. Following the first stage, pre-operative and postoperative culture results, infection parameters, kidney and liver function tests, and functional scores were analyzed. Kaplan-Meier survival analysis was done to determine the success rate. ResultsFifty patients with a mean follow-up of 48 months (24–108) were included in the study. A five-year survival analysis showed an 88.5% success rate. Fourteen percent of the patients had acute kidney injury with creatinine levels between 1.12–2.80 mg/dl, and 8% had a mild drug-induced liver injury with elevated serum ALT levels between 223–540 U/L and total bilirubin levels between 0.59–1.23 mg/dl. None of the patients required dialysis. All of the systemic side effects were reversible. ConclusionOur results have suggested that low dose antibiotic-loaded spacers are comparable to the studies with high dose antibiotic loaded spacers regarding infection eradication and survival rates. They are less likely to cause severe systemic side effects. Therefore we suggest low dose antibiotic-loaded spacers should be considered when treating patients with vancomycin sensitive Staphylococcal species and culture negative infected knee arthroplasty.

Management of periprosthetic knee joint infections: focus on the role of Nuclear Medicine (v2)

When faced with a painful knee replacement, ruling out infection is mandatory to set the correct therapeutic approach. However, it is not always easy, especially in subclinical/chronic infections. A multidisciplinary approach is necessary to assess in the most correct way each case of suspected periprosthetic knee joint infection. This review explores the role of nuclear medicine investigations in the management of periprosthetic knee infections and their proper use within a multidisciplinary pathway. A PubMed search was conducted selecting studies from the past 10 years. Triphasic bone scintigraphy has high sensitivity (93%) but poor specificity (56%) for periprosthetic joint infections of the knee, with a high negative predictive value (NPV), ranging from 96% to 100%. Consequently, a negative bone scan is useful in ruling out infection. In contrast, radiolabeled leukocyte scintigraphy is characterized by a sensitivity of 85.7-93%, specificity of 93.6-100%, diagnostic accuracy of 92.6-98%, NPV of 93-97.8%, and positive predictive value (PPV) of 66.7-100%. By adding a tomographic acquisition with hybrid single-photon emission computed tomography combined with computed tomography technique (SPECT/CT), the diagnostic accuracy increases. Because 18F-fluorodeoxyglucose (FDG) accumulates at both sites of inflammation and infection, FDG positron emission tomography (PET/CT) shows low specificity. A common decision-making process in the diagnosis of periprosthetic joint infection is not yet validated and multidisciplinary integration is mandatory. In this context, nuclear medicine can contribute decisively.

Periprosthetic knee infection: treatment options.

Infection is one of the most catastrophic complication following total knee arthroplasty (TKA) and represents the second most common cause of TKA failure. Treatment of a patient with periprosthetic joint infection (PJI) could require often costly and prolonged hospital stays, weeks or months of antibiotic therapy, and multiple surgical procedures. The best management is still highly debating, whereas many treatment options are available. These include suppressive antibiotics, arthroscopic irrigation and debridement, open debridement with insert exchange, single-stage reimplantation and two-stage reimplantation. The choice of the treatment depends on many variables, including integrity of implant, timing of the infection, host factors (age, health, immunologic status), virulence of the infecting organism and wishes of the patient. The aim of this review is to provide a comprehensive understaning of the different options for knee PJIs.

Medial gastrocnemius flap for the treatment of infected knee prostheses.

Muscular flaps may represent a valid treatment option for prosthetic infection after knee arthroplasty. We present the results of 20 consecutive patients treated with the use of medial gastrocnemius flap for the management of different types of injuries or integumentary defects after total knee arthroplasty. Tissue necrosis or dehiscence occurred within 1 and 2 months after arthroplasty. The mean follow-up was 23.4 (12-60) months. Clinical outcome was evaluated according to the infection control rate and post-operative Knee Society Score (KSS). Prosthesis salvage and complete restoration of skin coverage were achieved in all patients. Functional assessment was performed using the KSS score. The final knee KSS score was classified as excellent (score: 80-100) in 0 patients, good (score: 70-79) in 17 patients, fair (score: 60-69) in 2 patients, and poor (score: 60) in 1 patient. Residual Extension Deficit: 0-20°; Very Satisfactory in 17 patients. 30-70° Satisfactory in 2 patients, 80-90° Unsatisfactory in 1 patient. Patients who successfully underwent flap treatment experienced a much greater increase in both components of the KSS score. The results highlight the effectiveness of medial gastrocnemius muscular flap for the treatment of prosthetic knee infection, in terms of function, limb salvage, cost-effectiveness and post-surgery quality of life. Further larger studies may consolidate these findings.

Articulating spacers in elderly patients affected by periprosthetic knee infection: clinical findings and outcome.

Although the two-stage technique is a validated strategy in periprosthetic joint infections, there is a lack of data on the patients' clinical outcomes after the spacer placement. This study aims at evaluating the quality of life, joint function, and pain in patients over 70 years affected by periprosthetic joint infection treated with a two-stage exchange using metal on polyethylene spacers. We conducted a follow-up study to evaluate the quality of life and functionality of consecutive patients over 70 years treated for PJI at our institution using a validated assessment set including the Western Ontario and Mac Master University (WOMAC) score, Knee Society Score (KSS), numerical rating scale (NRS). Knee Range of Movement (ROM) before and after the surgery was also analyzed. Forty-five patients with a mean age of 76 ± 5.3 years were included. Coagulase-negative staphylococci were the most isolated microorganisms. In the preoperative study group, the WOMAC score was 48.4 ± 18.9, and the KSS objective and functional scores were 37.6 ± 17.3 and 27.6 ± 22.3, respectively. NRS was 7.3 ± 1.8. After three months of follow-up, we found better results than preoperative clinical evaluation. We retrieved similar results comparing our post-operative PROMS (WOMAC and KSS scores) with published thresholds for treatment success two months after primary total knee arthroplasty. The infection eradication rate was 87%. The two-stage technique confirmed its efficacy in the treatment of PJI. Patients over 70 years who had undergone the first stage of the two-stage technique for PJI showed a good quality of life and knee function.

A case of treatment of a fungal periprosthetic infection with a carbon-coated implant

Background. Arthroplasty is the most common surgical treatment for patients with end-stage knee arthrosis. From 2 to 7% of those operated on are patients with rheumatoid arthritis. The inflammatory process in the joint, low rehabilitation potential, long-term therapy with hormonal and genetically engineered biological agents, poor bone quality form a high risk of periprosthetic infection. In this group of patients, the saprophytic microorganism Candida albicans more often forms biofilms on endoprosthesis components, which presents difficulties in the treatment of periprosthetic infection.Aims: demonstration of a clinical case and rationale for the treatment of periprosthetic knee infection caused by Candida albicans using a revision implant with an anti-biofilm coating.Materials and methods. A clinical case presents the results of examination and treatment of a 46-year-old patient with secondary gonarthrosis on the background of rheumatoid arthritis with developed periprosthetic infection are evaluated. Surgical treatment was carried out by two-stage sanitation, using as part of the spacer an implant coated with silver-doped two-dimensionally ordered linear-chain carbon, against the background of etiotropic intravenous treatment with fluconazole.Results. The likely cause of the development of a fungal periprosthetic infection is a decrease in the activity of the immune system against the background of taking cytostatics and hormonal drugs in combination with the frequent uncontrolled use of antibacterial drugs. The choice of surgical tactics in favor of a two-stage revision is justified by the isolation of a «difficult to treat» Candida albicans. Timely diagnosis and the chosen method of treatment in combination allowed to no recurrence during the observation period of 12 months after the 2nd stage of revision.Conclusions. The results demonstrate the effectiveness of a spacer coated with silver-doped two-dimensionally ordered linear-chain carbon at the stage of sanitation for the treatment of periprosthetic infection caused by the «difficult to treat» Candida albicans.

Development of an innovative in vivo model of PJI treated with DAIR.

IntroductionProsthetic Joint Infection (PJI) are catastrophic complications of joint replacement. Debridement, implant retention, and antibiotic therapy (DAIR) is the usual strategy in acute infections but fails in 45% of MRSA infections. We describe the development of a model of infected arthroplasty in rabbits, treated with debridement and a course of vancomycin with clinically relevant dosage.Materials and methodsA total of 15 rabbits were assigned to three groups: vancomycin pharmacokinetics (A), infection (B), and DAIR (C). All groups received a tibial arthroplasty using a Ti-6Al-4V implant. Groups B and C were infected per-operatively with a 5.5 log10 MRSA inoculum. After 1 week, groups C infected knees were surgically debrided. Groups A and C received 1 week of vancomycin. Pharmacokinetic profiles were obtained in group A following 1st and 5th injections. Animals were euthanized 2 weeks after the arthroplasty. Implants and tissue samples were processed for bacterial counts and histology.ResultsAverage vancomycin AUC0–12 h were 213.0 mg*h/L (1st injection) and 207.8 mg*h/L (5th injection), reaching clinical targets. All inoculated animals were infected. CFUs were reproducible in groups B. A sharp decrease in CFU was observed in groups C. Serum markers and leukocytes counts increased significantly in infected groups.ConclusionWe developed a reproducible rabbit model of PJI treated with DAIR, using vancomycin at clinically relevant concentrations.

Phenotypic and functional characterisation of synovial fluid-derived neutrophils in knee osteoarthritis and knee infection

An increase in the number of neutrophils (NEUs) has long been associated with infections in the knee joints; however, their impact on knee osteoarthritis (KOA) pathophysiology remains largely unexplored. This study compared the phenotypic and functional characteristics of synovial fluid (SF)-derived NEUs in KOA and knee infection (INF). KOA NEUs were characterised by a lower expression of CD11b, CD54, and CD64 and higher expression of CD62L, TLR2, and TLR4 compared with INF NEUs. Except for CCL2, lower levels of inflammatory mediators and proteases were detected in KOA SF than in INF SF. Functionally, KOA NEUs displayed increased reactive oxygen species production and phagocytic activity compared with INF NEUs. Moreover, KOA and INF NEUs differed in cell sizes, histological characteristics of the surrounding synovial tissues, and their effects on the endothelial cells assessed by human umbilical vein endothelial cells. When KOA patients were subdivided based on the SF NEU abundance, patients with high NEUs (10%-60%) were characterised by i) elevated SF protein levels of TNF-α, IL-1RA, MMP-9, sTREM-1, VILIP-1 and ii) lower CD54, CD64, TLR2 and TLR4 expression compared to patients with low NEUs (<10%). Analysis of paired SF samples suggests that low or high NEU percentages, respectively, persist throughout the course of disease. Our findings suggest that NEU may play a significant role in KOA pathophysiology. Further studies should explore the mechanisms that contribute to the increased number of NEUs in SF and the clinical consequences of neutrophilic phenotype in KOA.

Mortality and re-revision following single-stage and two-stage revision surgery for the management of infected primary knee arthroplasty in England and Wales : evidence from the National Joint Registry.

We compared the risks of re-revision and mortality between two-stage revision surgery and single-stage revision surgery among patients with infected primary knee arthroplasty. Patients with a periprosthetic joint infection (PJI) of their primary knee arthroplasty, initially revised with a single-stage or a two-stage procedure in England and Wales between 2003 and 2014, were identified from the National Joint Registry. We used Poisson regression with restricted cubic splines to compute hazard ratios (HR) at different postoperative periods. The total number of revisions and re-revisions undergone by patients was compared between the two strategies. A total of 489 primary knee arthroplasties were revised with single-stage procedure (1,390 person-years) and 2,377 with two-stage procedure (8,349 person-years). The adjusted incidence rates of all-cause re-revision and for infection were comparable between these strategies (HR overall five years, 1.15 (95% confidence interval (CI) 0.87 to 1.52), p = 0.308; HR overall five years, 0.99 (95% CI 0.70 to 1.39), p = 0.949, respectively). Patients initially managed with single-stage revision received fewer revision procedures overall than after two-stage revision (1.2 vs 2.2, p < 0.001). Mortality was lower for single-stage revision between six and 18 months postoperative (HR at six months, 0.51 (95% CI 0.25 to 1.00), p = 0.049 HR at 18 months, 0.33 (95% CI 0.12 to 0.99), p = 0.048) and comparable at other timepoints. The risk of re-revision was similar between single- and two-stage revision for infected primary knee arthroplasty. Single-stage group required fewer revisions overall, with lower or comparable mortality at specific postoperative periods. The single-stage revision is a safe and effective strategy to treat infected knee arthroplasties. There is potential for increased use to reduce the burden of knee PJI for patients, and for the healthcare system.Cite this article: Bone Joint Res2022;11(10):690-699.