Diagnosis of periprosthetic joint infection

[Pathologies of joint endoprostheses : Histopathological diagnostics for endoprosthetic centers]

Joint endoprosthetics is one of the most successful surgical-orthopedic procedures worldwide, enabling pain reduction and complete restoration of mobility. In the Federal Republic of Germany, around 400,000 joint endoprostheses, hip and knee joints are currently implanted every year ( https://www.eprd.de/de ) and around 30,000 replacement operations or revisions are carried out. Although there is constant optimization in the various technical and medical sectors of material development, construction, antibiotic therapy strategies, and surgical methodology of surgical joint replacement, factors that reduce service life and a variety of prosthesis-associated pathologies still exist. For implant revisions, the SLIM consensus classification, which is internationally accepted in the scientific literature, should be applied. The revised version of the SLIM consensus classification defines a comprehensive etiological spectrum of local joint endoprosthesis-associated pathologies histopathologically using nine types. In addition, this includes particle characterization and differentiation from endogenous particles. The analysis of the removed explant is the task of technical disciplines. Their mechanical and physical tests can provide information on the cause of the damage. For example, an examination of the fracture surface can determine whether the fracture occurred over a longer period of time (fatigue fracture, sustained fracture) or whether it occurred suddenly (forced fracture). It is therefore important to note that this diagnosis is carried out in an interdisciplinary manner, particularly in the context of peri-implant, mostly bacterial infections, and in the case of primarily functional and material-related causes. This interdisciplinary approach is particularly necessary for complex endoprosthesis pathologies, which require precise causal and technology-based damage analysis. In addition to histopathology, definitive diagnosis is only possible in a clinical-orthopedic, microbiological, laboratory medicine-related, radiological, nuclear medicine-related, material-technical and, in particular, biomechanical-technical context.

Intraoperative Direct Sonication Improves the Time to Positivity of Culture in Patients Who Have Periprosthetic Joint Infection

INTRODUCTION

Periprosthetic joint infection (PJI) is a severe complication following total joint arthroplasty (TJA). Traditional sonication protocols typically involve specimen transport and laboratory-based processing. In this study, we implemented an intraoperative sonication technique performed directly in the operating room, enabling immediate transfer of samples into culture bottles. We evaluated its effectiveness in improving culture yield and reducing time to positivity (TTP).

METHODS

This retrospective cohort study included 190 patients (93 hips, 97 knees) who underwent revision surgery for PJI at a tertiary care center in China from August 2021 to January 2024. All patients met the 2018 International Consensus Meeting criteria for PJI. Intraoperative direct sonication was performed using a handheld ultrasonic cell disruptor on retrieved implants and soft tissues. The sonicated fluid was then cultured. Culture yield and TTP were compared between sonicated and non-sonicated samples.

RESULTS

Among the 190 patients, a total of 833 culture samples were collected from synovial fluids, tissues (pre- and post-sonication), and prostheses (pre- and post-sonication). Of these, 510 samples yielded positive cultures and were included in the analysis of TTP. Culture positivity rates were calculated by dividing the number of positive samples by the total number of samples per specimen type. Sonicated tissue (T-POS) and prosthesis (P-POS) samples had higher culture positivity rates compared to pre-sonication samples. The T-POS samples had the highest culture yield (76.9%), while prosthesis pre-sonication (P-PRS) samples had the lowest (46.9%). Sonication significantly reduced TTP for both tissue and prosthesis samples (P < 0.05), with P-POS samples having the shortest median TTP (2.1 days).

CONCLUSION

To our knowledge, this study is the first to demonstrate the effectiveness of in vivo intraoperative sonication in improving culture yield and reducing TTP in PJI patients. The method may support earlier transition to targeted antibiotics, potentially improving treatment outcomes and antibiotic stewardship.

Isolation of Multiple Positive Cultures at Resection Arthroplasty is a Predictor of Failure Following Reimplantation

BACKGROUND

Although it is well established that the type of organism can be a risk factor for failure in patients with periprosthetic joint infection (PJI), no study to date has examined the impact of the number of positive cultures on treatment outcomes in patients undergoing 2-stage exchange. The purpose of this multicenter study was to determine the prognostic utility of multiple positive cultures at resection as a predictor of failure following reimplantation.

METHODS

This retrospective multicenter study identified 437 patients with chronic knee PJI who had undergone 2-stage exchange arthroplasty with a minimum of 1 year of follow-up following reimplantation. PJI was defined with use of the 2013 Musculoskeletal Infection Society (MSIS) criteria. Patients with culture-negative PJI were excluded (n = 138). Treatment failure was defined as either any reoperation for infection or PJI-related mortality. Multivariable regression controlling for risk factors for failure after a 2-stage arthroplasty was performed to determine whether ≥2 positive intraoperative cultures at resection can predict outcomes following reimplantation when compared with a single positive culture.

RESULTS

Two hundred and ninety-nine patients were included. At a mean follow-up of 6.2 ± 2.6 years, 48 patients (16.1%) experienced failure. Patients who had a failure were more likely to have had a longer interstage interval (p = 0.038) and were also more likely to have had ≥2 positive cultures at the time of resection arthroplasty (95.8% versus 75.3%; p = 0.001). On regression analysis, ≥2 positive cultures at resection was the only variable that was identified as a risk factor for failure following reimplantation in both the univariate (odds ratio [OR], 7.55 [95% CI, 2.24 to 47.0]; p = 0.006) and multivariable models (OR, 8.12 [95% CI, 2.31 to 51.9]; p = 0.005).

CONCLUSIONS

This is the first study to examine the impact of the number of positive cultures on outcomes in patients with PJI. We found that the presence of ≥2 positive cultures at resection was an indicator of a poor prognosis and resulted in a greater than eightfold increase in the risk of treatment failure in patients undergoing a 2-stage exchange.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

MIKROBE: a feasibility study for a randomised controlled trial of one-stage or two-stage surgery for prosthetic knee infection

BACKGROUND

Total knee replacement surgery is common, with over 107,000 operations performed in the UK in 2019. After surgery, about 1% of patients develop a deep infection, known as a prosthetic joint infection. Two types of operations, one- or two-stage revision surgery, are routinely performed to treat the infection. Re-infection rates are similar, but there is uncertainty regarding longer-term outcomes for patients. The aim of this study was to establish the feasibility of conducting a future randomised controlled trial that will compare clinical and cost-effectiveness of one-stage versus two-stage revision knee surgery for prosthetic joint infection.

METHODS

Following eligibility screening, consenting patients took part in an audio-recorded consultation with their surgeon and were then randomised on a 1:1 allocation to one-stage or two-stage revision surgery. Patient-reported outcome measures were administered at baseline and 3 and 6 months postoperatively. Embedded qualitative work with patient participants and nonparticipants and with surgeons to understand the acceptability of trial processes and involvement was undertaken. Patient and public involvement and engagement activities were conducted throughout the study.

RESULTS

Of 136 patients screened, only 3 were randomised and had surgery as part of the study. Qualitative data were collected from the three participants, as well as from two eligible patients who declined participation and two who withdrew from participation after the initial patient-surgeon consultation. Five surgeons took part in qualitative interviews prior to study end.

CONCLUSION

This study indicated that a larger randomised controlled trial evaluating one-stage versus two-stage revision knee surgery for prosthetic joint infection is not feasible with the current straightforward randomised controlled trial design. Future research needs to consider the most appropriate study design and methodology to address this important research question.

TRIAL REGISTRATION

No.: NCT04458961.

Consensus statement on problematic knee replacement and revision knee replacement: A collaboration between EKS and BASK

BACKGROUND

Up to 20% of primary total knee arthroplasty (TKA) patients are not satisfied with their outcome. Both the analysis of these patients and revision surgery can be complex, expensive and outcomes can vary widely.

AIM

The aim of this study was to deliver consensus recommendations regarding outpatient analysis, surgical treatment and arrangement of clinical services concerning patients with a problematic TKA or revision knee replacement (RTKA).

METHODS

Members of BASK and EKS were invited to attend a joint meeting in London, UK (December 2019). A formal consensus process was undertaken at the meeting incorporating a multiple round Delphi exercise, with group discussion of areas of agreement and disagreement between rounds. Eighty delegates attended the meeting and five consensus statements were considered, with a threshold level of 80% agreement required as the definition consensus. A further consensus meeting of EKS members in Kitzbuhl, Austria (January 2023) followed similar methodology and considered a further four statements on this topic.

RESULTS

From the first meeting, 5 consensus statements with accompanying supporting evidence and text were agreed. 1) In suspected infection, a recognised diagnostic pathway and definition should be used (e.g. MSIS, ICM, EBJIS) and documented; 2) Revision of an infected TKA should be treated in units with a multidisciplinary team; 3) Initial investigation of a problematic TKA should include a minimum of: clinical investigation, X-Rays and blood tests, with further discussion with the MDT if required; 4) Units providing RTKA should have surgeons with evidence of specific training or experience, and on-going minimum unit numbers; 5) National Orthopaedic/Knee Societies should develop a strategy on Revision TKA provision taking into account: workforce, revision burden, location, hospital infrastructure. From the second meeting a further 4 consensus statements were agreed. Two statements were agreed text content answering the questions: 1) What should be included in the basic diagnostic workup of a painful TKA? and 2) Which are the key factors for surgeons to consider before offering the patient revision surgery? The two other agreed statements are: 3) Pre-operative diagnosis is related to outcome in RTKA and 4) RTKA for pain, without a surgically treatable diagnosis, is unpredictable.

CONCLUSIONS

The agreed joint BASK-EKS consensus statements and the EKS consensus statements on the assessment of problematic RTKA are recommended as the contemporary basis of optimal care for these patients and should inform future training and service developments.

Time to surgery and other risk factors for mortality and complication rates in patients with periprosthetic femoral fractures at the knee

BACKGROUND

There is a high level of evidence that a short time to surgery (TTS) improves the outcome for patients with hip fractures. Accordingly, recommendations for timely treatment have been included in national guidelines. As patient characteristics appear to be similar, it seems reasonable that these guidelines are applicable to other fracture entities, such as knee periprosthetic femoral fracture (PPF). This monocentric retrospective study aimed to investigate outcome-related risk factors, particularly TTS, for knee PPF.

METHODS

In total, 141 consecutive patients with knee PPF in a maximum-care arthroplasty and trauma centre, treated between 2006 and 2020, were retrospectively evaluated. Primary outcome variables were operative and general complications as well as mortalities within 1 year. Outcome-related risk factors were identified based on regression analysis using SPSS. For analysis of TTS, the cases were divided into two groups using a TTS of 24 h as the cutoff value.

RESULTS

The 1-year mortality was 8.3 %. Associated risk factors were age (HR 1.2; p = 0.010) and Charlson score (HR 2.1; p = 0.001). Both, surgical and general complications occurred in 20.6 % of the cases. Age (OR 1.07, p = 0.025) and a TTS > 24 h (OR 3.06, p = 0.020) were identified as risk factors for general complications. The TTS ≤ 24 h (n = 75) and TTS > 24 h (n = 66) groups were comparable in terms of baseline characteristics. Revision arthroplasty was performed more frequently in the TTS > 24 h group (p < 0.001).

CONCLUSION

1-year mortality after knee PPF was 8.3 %. With a high complication rate in the treatment of knee PPF, TTS was identified as a risk factor for general complications. Early treatment appears to be beneficial for patients with knee PPF.

Effectiveness of rifampicin combination therapy for orthopaedic implant-related infections: A systematic review and meta-analysis

BACKGROUND

In vitro, animal, and clinical comparative studies have revealed that combinations of rifampicin with antibacterial agents are effective in the treatment of biofilm-associated infections. This study aimed to assess the effectiveness of rifampicin combination therapies compared with monotherapies without rifampicin in patients with orthopaedic implant-related infections.

MATERIALS AND METHODS

The clinical literature was comprehensively searched for studies assessing the effectiveness of rifampicin combination therapy in patients with orthopaedic implant-related infection. Identified studies were screened based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses flow diagram. The primary outcome was the cure rate and the secondary outcome was the incidence of adverse events. Subgroup analyses were performed based on causative organisms, antibacterial agents, and types of surgical intervention.

RESULTS

Twenty-seven studies were identified, including two randomized controlled trials (RCTs) and 25 cohort studies. Rifampicin combinations were associated with significantly higher cure rates than monotherapies in cohort studies, but not in RCTs. Subgroup analyses showed that rifampicin combinations were effective in patients infected with Cutibacterium and Staphylococcus spp.; in patients who underwent debridement, antibiotics, implant retention procedures; and in patients with one-stage revision. Moreover, combinations of rifampicin and fluoroquinolones were more effective than fluoroquinolones alone, while combinating rifampicin with other antibacterial agents showed no significant benefit. Combination treatment did not significantly affect adverse events in either RCTs or observational studies. Risk of bias assessment and summary of findings showed that the certainty of evidence for both RCTs and observational studies was very low.

CONCLUSIONS

This systematic review and meta-analysis confirmed the potential effectiveness of rifampicin combination therapy for the cure of orthopaedic implant-related infection in some circumstances, although the certainty and quality of evidence were very low.

Surgery Within 24 Hours Reduces Mortality and General Complication Rates in Patients Who Have Periprosthetic Femoral Fractures at the Hip

BACKGROUND

In patients who have hip fractures, treatment within 24 hours reduces mortality and complication rates. A similar relationship can be assumed for patients who have hip periprosthetic femoral fractures (PPFs) owing to the similar baseline characteristics of the patient populations. This monocentric retrospective study aimed to compare the complication and mortality rates in patients who had hip PPF treated within and after 24 hours.

METHODS

In total, 350 consecutive patients who had hip PPF in a maximum-care arthroplasty and trauma center between 2006 and 2020 were retrospectively evaluated. The cases were divided into 2 groups using a time to surgery (TTS) of 24 hours as the cutoff value. The primary outcome variables were operative and general complications as well as mortalities within 1 year.

RESULTS

Overall, the mean TTS was 1.4 days, and the 1-year mortality was 14.6%. The TTS ≤ 24 hours (n = 166) and TTS > 24 hours (n = 184) groups were comparable in terms of baseline characteristics and comorbidities. Surgical complications were equally frequent in the 2 groups (16.3 versus 15.2%, P = .883). General complications occurred significantly more often in the late patient care group (11.4 versus 28.3%, P < .001). In addition, the 30-day mortality (0.6 versus 5.5%, P = .012), and 1-year mortality (8.3 versus 20.5%, P = .003) rates significantly increased in patients who had TTS > 24 hours. Cox regression analysis yielded a hazard ratio of 4.385 (P < .001) for the TTS > 24 hours group.

CONCLUSIONS

Prompt treatment is required for patients who have hip PPF to reduce mortality and overall complications.

Periprosthetic hip infection: Current concepts and the Wrightington experience

Total hip arthroplasty (THA) is a highly successful operation performed worldwide in increasing numbers for a wide range of indications. There has been a corresponding rise in the incidence of periprosthetic joint infection of the hip (PJIH), which is a devastating complication. There is a significant variation in the definition, diagnosis and management of PJIH largely due to a lack of high-level evidence. The current standard of practice is largely based on cohort studies from high-volume centres, consensus publications amongst subject experts, and national guidance. This review describes our philosophy and practical approach of managing PJIH at a regional tertiary high-volume joint replacement centre.

The Impact of Culture Negativity on the Outcomes of Revision Total Knee Arthroplasty for Chronic PJI

Culture-positive (CP) and culture-negative (CN) periprosthetic joint infections (PJI) remain a crucial area of research; however, current studies comparing these infections rely on unstandardized outcome reporting tools. Our study aimed to compare the outcomes of two-stage revision of CP and CN PJI using the standardized Musculoskeletal Infection Society (MSIS) outcome reporting tool. We retrospectively reviewed 138 patients who were diagnosed with PJI and indicated for two-stage revision total knee arthroplasty (rTKA). The majority of patients in both CP and CN cohorts achieved infection control without the need for reoperation (54.1% and 62.5%, respectively). There was a significant difference in the overall distribution of MSIS outcomes (p = 0.043), with a significantly greater rate of CN patients falling into Tier 1 (infection control without the use of suppressive antibiotics) (52.5% versus 29.6%, p = 0.011). There was also a significant difference in the distribution of septic versus aseptic reoperations after 2nd stage (p = 0.013), with more CP reoperations being septic and more CN reoperations being aseptic. The duration from first to second stage was significantly shorter in the CN cohort (p = 0.002). While overall infection control was similar between cohorts, these data suggest that the outcomes of two-stage rTKA are favorable in cases of CN PJI.

Serum and Synovial Markers in the Diagnosis of Periprosthetic Joint Infection of the Hip, Knee, and Shoulder: An Algorithmic Approach

➤ No single test has demonstrated absolute accuracy for the diagnosis of periprosthetic joint infection (PJI).➤ Physicians rely on a combination of serological tests, synovial markers, and clinical findings plus clinical judgment to help to guide preoperative decision-making.➤ Several organizations have proposed criteria for the diagnosis of hip or knee PJI on which we now rely.➤ Given that shoulder arthroplasty has only recently become popular, it is possible that a shoulder-specific definition of PJI will be introduced in the coming years.➤ Although a number of serum and synovial markers have demonstrated high accuracy for the diagnosis of PJI of the hip and knee, further research is needed in order to identify markers that may be more suitable for the diagnosis of shoulder PJI and for the potential development and identification of specific serological tests as screening tools for PJI.

The influence of gut microbiome on periprosthetic joint infections: State-of-the art

Early periprosthetic joint infection constitutes one of the most frightening complications of joint replacement. Recently, some evidence has highlighted the potential link between dysregulation of the gut microbiota and degenerative diseases of joints. It has been hypothesized that microbiome dysbiosis may increase the risk of periprosthetic joint infection by facilitating bacterial translocation from these sites to the bloodstream or by impairing local or systemic immune responses. Although the processes tying the gut microbiome to infection susceptibility are still unknown, new research suggests that the presurgical gut microbiota-a previously unconsidered component-may influence the patient's ability to resist infection. Exploring the potential impact of the microbiome on periprosthetic joint infections may therefore bring new insights into the pathogenesis and therapy of these disorders. For a successful therapy, a proper surgical procedure in conjunction with an antibacterial concept is essential. As per the surgical approach, different treatment strategies include surgical irrigation, debridement, antibiotic therapy, and implant retention with or without polyethylene exchange. Other alternatives could be one-stage or two-stage revisions surgery. Interventions that either directly target gut microbes as well as interventions that modify the composition and/or function of the commensal microbes represent an innovative and potentially successful field to be explored. In recent times, innovative therapeutic methods have arisen in the realm of microbiome restoration and the management of gut-related ailments. These progressive approaches offer fresh perspectives on tackling intricate microbial imbalances in the gastrointestinal tract. These emerging therapies signify a shift towards more precise and individualized approaches to microbiome restoration and the management of gut-related disorders. Once a more advanced knowledge of the pathways linking the gut microbiota to musculoskeletal tissues is gained, relevant microbiome-based therapies can be developed. If dysbiosis is proven to be a significant contributor, developing treatments for dysbiosis may represent a new frontier in the prevention of periprosthetic joint infections.

Update on the role of pathology and laboratory medicine in diagnosing periprosthetic infection

Technological and implant design advances have helped reduce the frequency of aseptic total joint arthroplasty failure, but periprosthetic joint infections (PJI) remain a clinical important problem with high patient morbidity. Misinterpreting PJI as aseptic mechanical loosening commonly leads to unsatisfactory revision arthroplasty, persistent infection, and poor long-term results. While there is no single "gold standard" diagnostic test for PJI, recent collaborative efforts by Orthopaedic and Infectious Disease Societies have developed algorithms for diagnosing PJI. However, the efficacy of individual tests as well as diagnostic thresholds are controversial. We review the recommended thresholds for commonly used screening tests as well as tissue histopathology and confirmatory tests to diagnose periprosthetic infection. We also update lesser-known laboratory tests, and we briefly summarize rapidly evolving molecular tests to diagnose periprosthetic infection. Pathologists hold a critical role in assisting with PJI diagnosis, maintaining laboratory test quality and interpreting test results. Collaboration between clinicians and pathologists is essential to provide optimal patient care and reduce the burden of PJI.

Changing the definition of treatment success alters treatment outcomes in periprosthetic joint infection: a systematic review and meta-analysis

Background: Variability in the definition of treatment success poses difficulty when assessing the reported efficacy of treatments for hip and knee periprosthetic joint infection (PJI). To address this problem, we determined how definitions of PJI treatment success have changed over time and how this has affected published rates of success after one-stage and two-stage treatments for hip and knee PJI. Methods: A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted to identify one-stage and two-stage revision hip and knee PJI publications in major databases (2006-2021). Definition of treatment success, based on Musculoskeletal Infection Society tier criteria, was identified for each study. Publication year, number of patients, minimum follow-up, and study quality were also recorded. The association of success definitions and treatment success rate was measured using multi-variable meta-regression. Results: Study quality remained unchanged in the 245 publications included. Over time, no antibiotics (tier 1) and no further surgery (tier 3) (40.7 % and 54.5 %, respectively) became the two dominant criteria. After controlling for type of surgery, study quality, study design, follow-up, and year of publication, studies with less strict success definitions (tier 3) reported slightly higher odds ratios of 1.05 [1.01, 1.10] ( p = 0.009 ) in terms of treatment success rates compared to tier 1. Conclusions: PJI researchers have gravitated towards tier-1 and tier-3 definitions of treatment success. While studies with stricter definitions had lower PJI treatment success, the clinical significance of this is unclear. Study quality, reflected in the methodological index for non-randomized studies (MINORS) score, did not improve. We advocate for improving PJI study quality, including clarification of the definition of treatment success.

Risk factors for early septic failure after two-stage exchange total knee arthroplasty for treatment of periprosthetic joint infection

BACKGROUND

The cause of early septic failure after two-stage exchange revision total knee arthroplasty (TKA) for chronic periprosthetic joint infection (PJI) and the factors affecting it are not well known. The purpose of this study was to determine the surgical outcomes and the risk factors for early septic failure after two-stage revision TKA for chronic PJI.

METHODS

We identified a total of 246 adult patients who met the Musculoskeletal Infection Society (MSIS) diagnostic criteria for chronic PJI at two academic tertiary hospitals from March 2012 to December 2018. Finally, 151 patients who consecutively received two-stage exchange revision TKA for chronic PJI and who had a minimum 3-year follow-up were enrolled and retrospectively reviewed. Successful surgical treatment was evaluated for two-stage revision TKA and risk factors for early septic failure were identified.

RESULTS

Early septic failures occurred within 3 years after reimplantation in 48 patients (31.8%). After accounting for potentially confounding variables, we found that male patient [odds ratio (OR): 2.753, 95% confidence interval (CI) 1.099-6.893, p = 0.031], fungus or mycobacterial infection (OR: 5.224, 95% CI 1.481-18.433, p = 0.01), and positive culture at reimplantation (OR: 4.407, 95% CI 1.255-15.480, p = 0.021) were independently associated with early septic failure after two-stage exchange revision TKA.

CONCLUSION

Male patients, fungus or mycobacterial infection, and positive culture at reimplantation were independently associated with an increased risk of early septic failure after two-stage exchange revision TKA despite normal C-reactive protein values prior to reimplantation. Further prospective and high-quality studies are needed to determine the risk factors of two-stage exchange revision TKA for chronic PJI.

LEVEL OF EVIDENCE

level IV; retrospective comparison; treatment study.

Management of septic arthritis and prosthetic joint infection

Management of joint infection is an evolving topic. This article reviews the literature on the management of native and prosthetic joint infection and suggests some areas of improvement in short- and long-term management which could lead to better patient outcomes. Surgical management is the mainstay of treatment for native or prosthetic knee infection and aspiration should only be used for diagnostic purposes. A multidisciplinary team approach and compliance with national guidelines, alongside referral networks and pooling of expertise, should be mandatory to improve patient outcomes.

[Structured approach for infected prosthesis]

BACKGROUND

Endoprosthesis infections represent a major challenge for doctors and patients. Due to the increase in endoprosthesis implantation because of the increasing life expectancy, an increase in endoprosthesis infections is to be expected. In addition to infection prophylaxis, methods of infection control become highly relevant, especially in the group of geriatric and multimorbid patients. The aim is to reduce the high 1‑year mortality from prosthesis infections through a structured algorithm.

ALGORITHM FOR PROSTHESIS INFECTIONS

Prosthesis infections can basically be divided into early and late infections. According to the criteria of the International Consensus Meeting, a late infection is defined as the occurrence more than 30 days after implantation. With respect to the planned approach, the (p)TNM classification offers an orientation. In the early postoperative interval the clinical appearance is crucial as in this phase neither laboratory parameters nor an analysis of synovial fluid show a high sensitivity. It is fundamental that, apart from patients with sepsis, environment diagnostics should be initiated. If a late infection is suspected, in addition to radiological diagnostics (X-ray, skeletal scintigraphy and if necessary, computed tomography, CT), laboratory (C-reactive protein, CRP, leukocytes, blood sedimentation, and if necessary, interleukin‑6, procalcitonin) and microbiological diagnostics (arthrocentesis with synovial analysis and microbiology) are indicated; however, in addition to the arthrocentesis result, the clinical appearance is crucial in cases where an exclusion cannot be confirmed by laboratory parameters. If an infection is confirmed, the treatment depends on the spectrum of pathogens, the soft tissue situation and the comorbidities, including a multistage procedure with temporary explantation and, if necessary, implantation of an antibiotic-containing spacer is necessary. A prosthesis preservation using the debridement, antibiotics and implant retention (DAIR) regimen is only appropriate in an acute infection situation. Basically, radical surgical debridement should be carried out to reduce the pathogen load and treatment of a possible biofilm formation for both early and late infections. The subsequent antibiotic treatment (short or long interval) should be coordinated with the infectious disease specialists.

CONCLUSION

A structured approach for prosthesis infections oriented to an evidence-based algorithm provides a sufficient possibility of healing. An interdisciplinary approach involving cooperation between orthopedic and infectious disease specialists has proven to be beneficial. Surgical treatment with the aim of reducing the bacterial load by removing the biofilm with subsequent antibiotic treatment is of intrinsic importance.

2022 SPILF - Clinical Practice guidelines for the diagnosis and treatment of disco-vertebral infection in adults

These guidelines are an update of those made in 2007 at the request of the French Society of Infectious Diseases (SPILF, Société de Pathologie Infectieuse de Langue Française). They are intended for use by all healthcare professionals caring for patients with disco-vertebral infection (DVI) on spine, whether native or instrumented. They include evidence and opinion-based recommendations for the diagnosis and management of patients with DVI. ESR, PCT and scintigraphy, antibiotic therapy without microorganism identification (except for emergency situations), therapy longer than 6 weeks if the DVI is not complicated, contraindication for spinal osteosynthesis in a septic context, and prolonged dorsal decubitus are no longer to be done in DVI management. MRI study must include exploration of the entire spine with at least 2 orthogonal planes for the affected level(s). Several disco-vertebral samples must be performed if blood cultures are negative. Short, adapted treatment and directly oral antibiotherapy or early switch from intravenous to oral antibiotherapy are recommended. Consultation of a spine specialist should be requested to evaluate spinal stability. Early lifting of patients is recommended.

Utility of D-dimer in total joint arthroplasty

As the number of patients receiving total joint replacements continues to rise, considerable attention has been directed towards the early detection and prevention of postoperative complications. While D-dimer has long been studied as a diagnostic tool in venous thromboembolism (VTE), this assay has recently received considerable attention in the diagnosis of periprosthetic joint infection (PJI). D-dimer values are substantially elevated in the acute postoperative period after total joint arthroplasty, with levels often exceeding the standard institutional cutoff for VTE (500 µg/L). The utility of D-dimer in detecting VTE after total joint replacement is currently limited, and more research to assess its value in the setting of contemporary prophylaxis protocols is warranted. Recent literature supports D-dimer as a good to excellent biomarker for the diagnosis of chronic PJI, especially when using serum sample technique. Providers should exercise caution when interpreting D-dimer levels in patients with inflammatory and hypercoagulability disorders, as the diagnostic value is decreased. The updated 2018 Musculoskeletal Infection Society criteria, which includes D-dimer levels > 860 µg/L as a minor criterion, may be the most accurate for diagnosing chronic PJI to date. Larger prospective trials with transparent lab testing protocols are needed to establish best assay practices and optimal cutoff values for D-dimer in the diagnosis of PJI. This review summarizes the most current literature on the value of D-dimer in total joint arthroplasty and elucidates areas for future progress.

Spacer exchange in persistent periprosthetic joint infection: microbiological evaluation and survivorship analysis

PURPOSE

The purposes of this study were to determine demographics and characteristics of patients who underwent spacer exchange for persistent infection in the setting of two-stage arthroplasty for periprosthetic joint infection, to describe the microbiology of pathogens involved, to analyze survivorship free from infection in these patients.

METHODS

The institutional prospectively collected database was reviewed to enroll patients with minimum 2 years follow-up. Patients who underwent two-stage procedure for septic arthritis were excluded, as were patients who had spacer fracture or dislocation.

RESULTS

A total of 34 patients (41 procedures) were included. Mean age was 65.0 ± 12.8 years. Mean follow-up was 53.4 ± 24.8 months. Mean number of previous procedures was 3.6 ± 1.2. A total of 27 (79.4%) patients underwent final reimplantation. The most frequently isolated pathogen in spacer exchange was Staphylococcus epidermidis (10 cases, 28.6%). Polymicrobial cultures were obtained from 9 (25.71%) patients, 10 (28.6%) presented culture-negative infections. A total of 11 (32.4%) resistant pathogens were isolated, and 16 (47.0%) difficult to treat pathogens were detected. Eradication rate was 78.8%. Overall survivorship of implants after final reimplantation was 72.8% at 51.8 months.

CONCLUSION

Surgeons should be aware that subjects necessitating spacer exchange often present multiple comorbidities, previous staged revision failures, soft-tissue impairment and difficult to treat infection. In these patients, spacer exchange provides good clinical results and infection eradication, preventing arthrodesis or amputation.

2022 American Association of Hip and Knee Surgeons Symposium: Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is the leading cause of failure in patients undergoing total joint arthroplasty. This article is a brief summary of a symposium on PJI that was presented at the annual AAHKS meeting. It will provide an overview of current technqiues in the prevention, diagnosis, and management of PJI. It will also highlight emerging technologies in this setting.

Diagnostic Utility and Thresholds for Commonly Obtained Serum and Synovial Markers Prior to Reimplantation in Periprosthetic Joint Infection

BACKGROUND

Accurate diagnosis of persistent periprosthetic joint infection (PJI) during 2-stage exchange remains a challenge. This study evaluated the diagnostic performance and thresholds of several commonly obtained serum and synovial markers to better guide reimplantation timing.

METHODS

This was a retrospective review of 249 patients who underwent 2-stage exchange with antibiotic spacers for PJI. Serum and synovial markers analyzed included white blood cell (WBC) count, polymorphonuclear percentage (PMN%), neutrophil-to-lymphocyte ratio (NLR), and absolute neutrophil count (ANC). Serum markers analyzed were erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), as well as percentage change in ESR and CRP from initial diagnosis to reimplantation. Area under the curve (AUC) analyses were performed to determine diagnostic accuracy of detecting PJI.

RESULTS

In TKAs, synovial ANC and WBC had the highest AUCs (0.76), with thresholds of 2,952 and 3,800 cells/μL, respectively. The next best marker was serum CRP (0.73) with a threshold of 5.2 mg/dL. In THAs, serum CRP had the highest AUC (0.84) with a threshold of 4.3 mg/dL, followed by synovial PMN% (0.80) with a threshold of 77%. Percentage change in serum ESR or CRP provided low diagnostic value overall.

CONCLUSION

Regarding serum markers, CRP consistently performed well in detecting persistent PJI in patients with antibiotic spacers. Absolute values of serum CRP and ESR had better diagnostic value than trends for guiding reimplantation timing. Diagnostic performance differed with joint type; however, synovial markers outperformed serum counterparts. No marker alone can be utilized to diagnose residual PJI in these patients, and further work is needed in this domain.

Time to Positivity of Cultures Obtained for Periprosthetic Joint Infection

BACKGROUND

Despite its well-established limitations, culture remains the gold standard for microbial identification in periprosthetic joint infection (PJI). However, there are no benchmarks for the time to positivity (TTP) on culture for specific microorganisms. This study aimed to determine the TTP for pathogens commonly encountered in PJI.

METHODS

This retrospective, multicenter study reviewed prospectively maintained institutional PJI databases to identify patients who underwent hip or knee revision arthroplasty from 2017 to 2021 at 2 tertiary centers in the United States and Germany. Only patients who met the 2018 International Consensus Meeting (ICM) criteria for PJI and had a positive intraoperative culture were included. TTP on culture media was recorded for each sample taken intraoperatively. The median TTP was compared among different microbial species and different specimen types. Data are presented either as the mean and the standard deviation or as the median and the interquartile range (IQR).

RESULTS

A total of 536 ICM-positive patients with positive cultures were included. The mean number of positive cultures per patient was 3.9 ± 2.6. The median TTP, in days, for all positive cultures was 3.3 (IQR, 1.9 to 5.4). Overall, gram-negative organisms (TTP, 1.99 [1.1 to 4.1]; n = 225) grew significantly faster on culture compared with gram-positive organisms (TTP, 3.33 [1.9 to 5.8]; n = 1,774). Methicillin-resistant Staphylococcus aureus (TTP, 1.42 [1.0 to 2.8]; n = 85) had the fastest TTP, followed by gram-negative rods (TTP, 1.92 [1.0 to 3.9]; n = 163), methicillin-sensitive Staphylococcus aureus (TTP, 1.95 [1.1 to 3.3] n = 393), Streptococcus species (TTP, 2.92 [1.2 to 4.3]; n = 230), Staphylococcus epidermidis (TTP, 4.20 [2.4 to 5.5]; n = 555), Candida species (TTP, 5.30 [3.1 to 10]; n = 63), and Cutibacterium acnes (TTP, 6.97 [5.9 to 8.2]; n = 197). When evaluating the median TTP according to specimen type, synovial fluid (TTP, 1.97 [1.1 to 3.1]; n = 112) exhibited the shortest TTP, followed by soft tissue (TTP, 3.17 [1.4 to 5.3]; n = 1,199) and bone (TTP, 4.16 [2.3 to 5.9]; n = 782).

CONCLUSIONS

To our knowledge, this is the first study to examine the TTP of common microorganisms that are known to cause PJI. Increased awareness of these data may help to guide the selection of appropriate antimicrobial therapy and to predict treatment outcomes in the future. Nonetheless, additional studies with larger cohorts are needed to validate these benchmarks.

LEVEL OF EVIDENCE

Diagnostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Diagnosing Periprosthetic Joint Infection: a Scoping Review

PURPOSE OF REVIEW

The goal of this review is to provide an up to date understanding of the utility and limitations of the current tests utilized in the diagnosis of periprosthetic joint infection (PJI) in total knee and hip arthroplasty.

RECENT FINDINGS

Despite the growth in literature surrounding PJI diagnosis, there remains challenges in establishing a diagnosis of PJI. A combination of clinical, serum, and synovial tests and microbiologic and histologic examinations can yield a diagnosis in the majority of cases. Novel molecular and imaging studies may be beneficial for indeterminant cases. A number of emerging diagnostic tests have been proposed and may be incorporated into diagnostic algorithms in the future. Recently proposed stepwise diagnostic algorithms have shown high sensitivity and specificity. The diagnosis of PJI remains challenging due to a lack of tests that can definitively rule out infection. Diagnosis and investigations should occur in a stepwise fashion. There has been a plethora of new diagnostic tests introduced in attempts to improve the accuracy of diagnostic algorithms. The definition and algorithms for the diagnoses of PJI will continue to evolve as new techniques and tests are introduced.

How Does a "Dry Tap" Impact the Accuracy of Preoperative Aspiration Results in Predicting Chronic Periprosthetic Joint Infection?

BACKGROUND

Periprosthetic joint infection (PJI) after total hip arthroplasty (THA) is challenging to diagnose. We aimed to evaluate the impact of dry taps requiring saline lavage during preoperative intra-articular hip aspiration on the accuracy of diagnosing PJI before revision surgery.

METHODS

A retrospective review was conducted for THA patients with suspected PJI who received an image-guided hip aspiration from May 2016 to February 2020. Musculoskeletal Infection Society (MSIS) diagnostic criteria for PJI were compared between patients who had dry tap (DT) vs successful tap (ST). Sensitivity and specificity of synovial markers were compared between the DT and ST groups. Concordance between preoperative and intraoperative cultures was determined for the 2 groups.

RESULTS

In total, 335 THA patients met inclusion criteria. A greater proportion of patients in the ST group met MSIS criteria preoperatively (30.2% vs 8.3%, P < .001). Patients in the ST group had higher rates of revision for PJI (28.4% vs 17.5%, P = .026) and for any indication (48.4% vs 36.7%, P = .039). MSIS synovial white blood cell count thresholds were more sensitive in the ST group (90.0% vs 66.7%). There was no difference in culture concordance (67.9% vs 65.9%, P = .709), though the DT group had a higher rate of negative preoperative cultures followed by positive intraoperative cultures (85.7% vs 41.1%, P = .047).

CONCLUSION

Our results indicate that approximately one third of patients have dry hip aspiration, and in these patients cultures are less predictive of intraoperative findings. This suggests that surgeons considering potential PJI after THA should apply extra scrutiny when interpreting negative results in patients who require saline lavage for hip joint aspiration.

Factors predicting hip joint aspiration yield or “dry taps” in patients with total hip arthroplasty

Background

Image-guided joint aspirations used to assist the diagnosis of periprosthetic joint infection (PJI) may commonly result in a dry tap–or insufficient fluid for culture and cell count analysis. Dry tap aspirations are painful and invasive for patients and often utilize a subsequent saline lavage to obtain a microbiology sample. Currently, there is a paucity of the literature addressing predictors that could suggest whether a dry tap will occur. The purpose of this study was to examine the effects of various factors on “dry tap” occurrence in patients with suspected PJI following total hip arthroplasty (THA).

Methods

A retrospective review was performed among THA patients suspected for PJI who received image-guided joint aspiration procedures at our institution from May 2016 to February 2020. The procedural factors included the imaging modality used for aspiration, anatomic approach, needle gauge size used, and the presence of a trainee. The patient-specific factors included number of prior ipsilateral hip surgeries, femoral head size, ESR/CRP values, and BMI.

Results

In total, 336 patients met our inclusion criteria. One hundred and twenty hip aspirations resulted in a dry tap (35.7%) where the patients underwent a saline lavage. Among the procedural and patient-specific factors, none of the factors were found to be statistically different between the two cohorts nor conferred any greater odds of a dry tap occurring.

Conclusion

No associations with dry tap occurrence were found among the procedural and patient-specific factors studied. Further research is needed to identify additional factors that may be more predictive of dry taps.

The role of serum C-reactive protein in the diagnosis of periprosthetic shoulder infection

INTRODUCTION

There is a paucity of literature regarding serum C-reactive protein (CRP) in the evaluation of a shoulder periprosthetic joint infection (PJI). The purpose of the current study was to establish cutoff values for diagnosing shoulder PJI and evaluate the influence of the type of infecting microorganism and the classification subgroups according to last proposed International Consensus Meeting (ICM) criteria on the CRP level.

MATERIALS AND METHODS

A retrospective analysis of all 136 patients, who underwent septic or aseptic revision shoulder arthroplasty in our institution between January 2010 and December 2019, was performed. Shoulder PJI was defined according to the last proposed definition criteria of the ICM. Serum CRP levels were compared between infected and non-infected cases, between infection subgroups, as well as between different species of infecting microorganisms. A receiver-operating characteristic (ROC) analysis was performed to display sensitivity and specificity of serum CRP level for shoulder PJI.

RESULTS

A total of 52 patients (38%) were classified as infected, 18 meeting the criteria for definitive infection, 26 for probable infection and 8 for possible infection. According to the ROC curve, an optimized serum CRP threshold of 7.2 mg/l had a sensitivity of 69% and specificity of 74% (area under curve = 0.72). Patients with definitive infection group demonstrated significantly higher median serum CRP levels (24.3 mg/l), when compared to probable, possible infection groups and PJI unlikely group (8 mg/l, 8.3 mg/l, 3.6 mg/l, respectively, p < 0.05). The most common isolated microorganism was Cutibacterium acnes in 25 patients (48%) followed by coagulase-negative staphylococci (CNS) in 20 patients (39%). Patients with a PJI caused by high-virulent microorganisms had a significantly higher median serum CRP level compared to patients with PJI caused by low-virulent microorganisms (48 mg/l vs. 11.3 mg/l, p = 0.04).

CONCLUSIONS

Serum CRP showed a low sensitivity and specificity for the diagnosis of shoulder PJI, even applying cutoffs optimized by receiver-operating curve analysis. Low-virulent microorganisms and patients with probable and possible infections are associated with lower CRP levels compared to patients with definitive infection and infections caused by high-virulent microorganisms.

LEVEL OF EVIDENCE

Diagnostic Level III.

Outcomes of patients with unexpected diagnosis of infection at total hip or total knee arthroplasty revisions

PURPOSE

The pre-operative differential diagnosis between periprosthetic joint infections (PJIs) and aseptic failure is challenging particularly in low virulence and biofilm-related infections. This study aimed to assess the incidence and survival of patients with unexpected PJIs in a presumed aseptic revision of total hip (THA) and knee (TKA) arthroplasties.

METHODS

A retrospective analysis of a prospective cohort of patients was performed with 295 patients undergoing THA (n = 241) or TKA (n = 54) revision for presumed aseptic causes. Patients were diagnosed with unexpected PJI taking into account leukocyte count in the synovial fluid, sonicate, synovial culture, and tissue cultures of samples collected during surgery. The primary endpoint was the infection-free implant survival rate at theone year follow-up.

RESULTS

The unexpected PJIs were 60 out of 295 (20.3%), whereas 235 (79.7%) were aseptic revisions. In the unexpected PJI group, 6 (11.1%) patients underwent knee revision and 54 (22.4%) hip revision. At the one year follow-up, one patient (1.6%) in the unexpected PJI group and 3 (1.3%) in the aseptic group (p = 1.0) failed for infection. The infection-free implant survival rate at the one year follow-up was 98.3% (C.I. 95%, 94.9-99.9%) for the unexpected PJI group and 98.7% (C.I. 95%, 97.3-99.9%) (p = 0.82) for the aseptic group.

CONCLUSION

The incidence of unexpected PJIs in a presumed aseptic revision of THAs and TKAs has been previously underestimated. The infection-free implant survival rate at the one year follow-up in patients with unexpected PJIs was not significantly lower compared with patients undergoing aseptic revision.

Is D-dimer a Reliable Serum Marker for Shoulder Periprosthetic Joint Infection?

BACKGROUND

The diagnosis of periprosthetic shoulder infection continues to be difficult to make with confidence. Serum D-dimer has proven to be effective as a screening tool for periprosthetic joint infection in other major joints; however, it has yet to be evaluated for use in periprosthetic shoulder infection.

QUESTIONS/PURPOSES

(1) Is D-dimer elevated in patients with probable or definite periprosthetic shoulder infections? (2) What is the diagnostic accuracy of D-dimer for periprosthetic shoulder infections? (3) What are the diagnostic accuracies of serum tests (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], and D-dimer), singly and in combination?

METHODS

Between March 2016 and March 2020, 94 patients undergoing revision total shoulder arthroplasty (anatomic or reverse) at a single institution had preoperative serum testing with CRP, ESR, and D-dimer. These 94 patients were a subset of 189 revision shoulder arthroplasties performed at this institution during the study period who met inclusion criteria and consented to participate. Included patients had a mean ± SD age of 69 ± 8 years, and 56% (53 of 94) were men. Patient records were reviewed to classify patients as definitely having infection, probably having infection, possibly having infection, or unlikely to have an infection, according to the International Consensus Meeting (ICM) definition of periprosthetic shoulder infection. Statistical analyses, including a receiver operating characteristic curve analysis, were performed to quantify the diagnostic value of D-dimer for periprosthetic shoulder infection. Based on the ICM definition, 4% (4 of 94), 15% (14 of 94), 14% (13 of 94), and 67% (63 of 94) of patients had definite, probable, possible, or unlikely periprosthetic shoulder infections.

RESULTS

D-dimer was elevated in patients with definite or probable infections (median [range] 661 ng/mL [150 to 8205]) compared with those with possible infections or those who were unlikely to have an infection (263 ng/mL [150 to 3060]; median difference 143 ng/mL [95% CI 40 to 503]; p = 0.01). In the receiver operating characteristic curve analysis, D-dimer had an area under the curve of 0.71 (0.50-0.92), demonstrating weak diagnostic value. A D-dimer level of 598 ng/mL provided a sensitivity and specificity of 61% (95% CI 36% to 82%) and 74% (95% CI 62% to 83%), respectively, for diagnosing a definite or probable infection according to the ICM definitions. The specificity of detecting periprosthetic joint infection (88% [95% CI 79% to 94%]) was high when three positive serum markers (ESR, CRP, and D-dimer) were required, at the expense of sensitivity (28% [95% CI 10% to 53%]).

CONCLUSION

In periprosthetic shoulder infection, D-dimer is elevated. However, similar to other serum tests, it has limited diagnostic utility in identifying patients with periprosthetic shoulder infection. Further work is needed to understand the process by which D-dimer is associated with active infection.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Results of debridement, antibiotics, and implant retention for periprosthetic knee joint infection supplemented with the use of intraosseous antibiotics

AIMS

Debridement, antibiotics, and implant retention (DAIR) remains one option for the treatment of acute periprosthetic joint infection (PJI) despite imperfect success rates. Intraosseous (IO) administration of vancomycin results in significantly increased local bone and tissue concentrations compared to systemic antibiotics alone. The purpose of this study was to evaluate if the addition of a single dose of IO regional antibiotics to our protocol at the time of DAIR would improve outcomes.

METHODS

A retrospective case series of 35 PJI TKA patients, with a median age of 67 years (interquartile range (IQR) 61 to 75), who underwent DAIR combined with IO vancomycin (500 mg), was performed with minimum 12 months' follow-up. A total of 26 patients with primary implants were treated for acute perioperative or acute haematogenous infections. Additionally, nine patients were treated for chronic infections with components that were considered unresectable. Primary outcome was defined by no reoperations for infection, nor clinical signs or symptoms of PJI.

RESULTS

Mean follow-up for acute infection was 16.5 months (12.1 to 24.2) and 15.8 months (12 to 24.8) for chronic infections with unresectable components. Overall non-recurrence rates for acute infection was 92.3% (24/26) but only 44.4% (4/9) for chronic infections with unresectable components. The majority of patients remained on suppressive oral antibiotics. Musculoskeletal Infection Society (MSIS) host grade was a significant indicator of failure (p < 0.001).

CONCLUSION

The addition of IO vancomycin at the time of DAIR was shown to be safe with improved results compared to current literature using standard DAIR without IO antibiotic administration. Use of this technique in chronic infections should be applied with caution. While these results are encouraging, this technique requires longer follow-up before widespread adoption. Cite this article: Bone Joint J 2021;103-B(6 Supple A):185-190.

Clinical characteristics and risk factors for culture-negative periprosthetic joint infections

BACKGROUND

Culture-negative periprosthetic joint infections (PJIs) can complicate diagnosis and management of PJI. This study aimed to identify risk factors for culture-negative PJI and differences in clinical characteristics between culture-positive and culture-negative PJI group.

METHODS

This retrospective, cross-sectional study evaluated PJI cases obtained between January 2013 and October 2019 at our institution. These PJI cases were divided into culture-positive and culture-negative groups and then compared. The demographics, laboratory findings, and details of patient's clinical characteristics were investigated. Univariate and multivariate logistic regression analysis were performed to investigate risk factors for culture-negative PJI.

RESULTS

A total of 109 PJI cases were included in the analysis: 82 (75%) culture-positive and 27 (25%) culture-negative. The mean serum white blood cell (WBC) count, C-reactive protein level, and erythrocyte sedimentation rate in the culture-negative group were significantly lower than those in the culture-positive group (p < 0.05). There were no significant differences between the two groups regarding history of prior antibacterial administration or treatment success rates. Multivariate analysis identified a low serum WBC count as a risk factor for culture-negative PJI (odds ratio = 0.78; 95% confidence interval [CI] = 0.63-0.97; p = 0.027).

CONCLUSIONS

A low serum WBC count is a risk factor for culture-negative PJI, but prior antimicrobial therapy is not. The results suggest that PJI cases with lower levels of systemic inflammation are likely to be culture-negative; therefore, the possibility of a culture-negative result should be considered in suspected cases of PJI with low inflammatory markers, regardless of prior antibiotic exposure.

Next generation sequencing for pathogen detection in periprosthetic joint infections

Periprosthetic joint infections (PJI) represent one of the most catastrophic complications following total joint arthroplasty (TJA). The lack of standardized diagnostic tests and protocols for PJI is a challenge for arthroplasty surgeons.Next generation sequencing (NGS) is an innovative diagnostic tool that can sequence microbial deoxyribonucleic acids (DNA) from a synovial fluid sample: all DNA present in a specimen is sequenced in parallel, generating millions of reads. It has been shown to be extremely useful in a culture-negative PJI setting.Metagenomic NGS (mNGS) allows for universal pathogen detection, regardless of microbe type, in a 24-48-hour timeframe: in its nanopore-base variation, mNGS also allows for antimicrobial resistance characterization.Cell-free DNA (cfDNA) NGS, characterized by lack of the cell lysis step, has a fast run-time (hours) and, together with a high sensitivity and specificity in microorganism isolation, may provide information on the presence of antimicrobial resistance genes.Metagenomics and cfDNA testing have reduced the time needed to detect infecting bacteria and represent very promising technologies for fast PJI diagnosis.NGS technologies are revolutionary methods that could disrupt the diagnostic paradigm of PJI, but a comprehensive collection of clinical evidence is still needed before they become widely used diagnostic tools. Cite this article: EFORT Open Rev 2021;6:236-244. DOI: 10.1302/2058-5241.6.200099.

Trends in microbiological profiles and antibiotic resistance in periprosthetic joint infections

OBJECTIVE

This study examined the trends in demographics, the distribution of microorganisms, and antibiotic resistance in patients with periprosthetic joint infection (PJI).

METHODS

We conducted a retrospective study of 231 consecutive patients diagnosed with PJI in our hospital from January 2006 to December 2015 (93 and 138 patients diagnosed in 2006-2010 and 2011-2015, respectively). The linear-by-linear chi-squared test was used to assess the trends in demographics, the distribution of microorganisms, and antibiotic resistance.

RESULTS

Gram-positive cocci accounted for 63.9% of all pathogens, and coagulase-negative Staphylococcus (CoNS) accounted for 38.1% of all isolates. The proportion of isolates identified as methicillin-resistant CoNS significantly increased over the study period (39.0% vs. 61.8%). In addition, the proportions of levofloxacin-resistant CoNS (4.9% vs. 21.8%) and Staphylococcus aureus (6.3% vs. 45.0%) isolates significantly increased over the study period. By contrast, the proportions of penicillin-resistant CoNS (82.9% vs. 40.0%) and S. aureus (75.0% vs. 30.0%) isolates decreased over the study period.

CONCLUSION

Our research revealed changes in the distribution of microorganisms and antibiotic resistance profile of the pathogens responsible for PJI over time, which could complicate treatment. These findings may serve as a reference for strategies to prevent and empirically treat PJI in China.

Evaluation and interpretation of prosthetic joint infection diagnostic investigations

BACKGROUND

Total joint arthroplasty (TJA) is considered one of the most successful surgical procedures ever developed. It can successfully provide pain relief, restore joint function, and improve mobility and quality of life. Prosthetic joint infection (PJI) presents with a wide variety and severity of signs and symptoms. It remains a major threat to the outcome of TJA procedures and usually necessitates surgical intervention and prolonged courses of antibiotics. Inappropriate treatment of an unrecognized PJI usually ends with unacceptable and sometimes catastrophic results.

THE AIM

The understanding and evaluation of diagnostic investigations are extremely important to properly diagnose PJI, including frequently unrecognized low-grade infections, and to provide healthcare professionals with needed information for the care of patients affected by this condition. This article aims to review most of the methods available in PJI diagnostics, to emphasize the strengths and the weaknesses of each of them, and to provide a guideline on how to select the surgical treatment strategy based on the level of diagnostic certainty during the evaluation period. To safely accomplish this, it is crucial to be aware of the limitations of each diagnostic modality.

THE FOCUS

The emphasis will be on the use and interpretation of the core criteria for PJI diagnosis, including the pathognomonic sinus tract communicating with the implant, purulent synovial fluid, inflammation in the periprosthetic tissue, cell count with differential, microbial growth in the synovial fluid culture, tissue sample cultures, and sonication samples.

Pathogenesis, Evaluation, and Management of Osteolysis Following Total Ankle Arthroplasty

Periprosthetic osteolysis is a common occurrence after total ankle arthroplasty (TAA) and poses many challenges for the foot and ankle surgeon. Osteolysis may be asymptomatic and remain benign, or it may lead to component instability and require revision or arthrodesis. In this article, we present a current and comprehensive review of osteolysis in TAA with illustrative cases. We examine the basic science principles behind the etiology of osteolysis, discuss the workup of a patient with suspected osteolysis, and present a review of the evidence of various management strategies, including grafting of cysts, revision TAA, and arthrodesis.Level of Evidence: Level V, expert opinion.

When can total knee arthroplasty be safely performed following prior arthroscopy?

Background

The optimal timing to perform a total knee arthroplasty (TKA) after knee arthroscopy (KA) was controversial in the literature. We aimed to 1) explore the effect of prior KA on the subsequent TKA; 2) identify who were not suitable for TKA in patients with prior KA, and 3) determine the timing of TKA following prior KA.

Methods

We retrospectively reviewed 87 TKAs with prior KA and 174 controls using propensity score matching in our institution. The minimum follow-up was 2 years. Postoperative clinical outcomes were compared between groups. Kaplan-Meier curves were created with reoperation as an endpoint. Multivariate Cox proportional hazards regressions were performed to identify risk factors of severe complications in the KA group. The two-piecewise linear regression analysis was performed to examine the optimal timing of TKA following prior KA.

Results

The all-cause reoperation, revision, and complication rates of the KA group were significantly higher than those of the control group (p < 0.05). The survivorship of the KA group and control group was 92.0 and 99.4% at the 2-year follow-up (p = 0.002), respectively. Male (Hazards ratio [HR] = 3.2) and prior KA for anterior cruciate ligament (ACL) injury (HR = 4.4) were associated with postoperative complications in the KA group. There was a non-linear relationship between time from prior KA to TKA and postoperative complications with the turning point at 9.4 months.

Conclusion

Prior KA is associated with worse outcomes following subsequent TKA, especially male patients and those with prior KA for ACL injury. There is an increased risk of postoperative complications when TKA is performed within nine months of KA. Surgeons should keep these findings in mind when treating patients who are scheduled to undergo TKA with prior KA.

Investigation and management of prosthetic joint infection in knee replacement: A BASK Surgical Practice Guideline

BACKGROUND

The burden of knee replacement prosthetic joint infection (KR PJI) is increasing. KR PJI is difficult to treat, outcomes can be poor and it is financially expensive and limited evidence is available to guide treatment decisions.

AIM

To provide guidelines for surgeons and units treating KR PJI.

METHODS

Guideline formation by consensus process undertaken by BASK's Revision Knee Working Group, supported by outputs from UK-PJI meetings.

RESULTS

Improved outcomes should be achieved through provision of care by revision centres in a network model. Treatment of KR PJI should only be undertaken at specialist units with the required infrastructure and a regular infection MDT. This document outlines practice guidelines for units providing a KR PJI service and sets out: CONCLUSIONS: KR PJI patients treated within the NHS should be provided the best care possible. This report sets out guidance and support for surgeons and units to achieve this.

Reporting Outcomes of Treatment for Periprosthetic Joint Infection of the Knee and Hip Together With a Minimum 1-Year Follow-Up is Reliable

BACKGROUND

Although there is an increasing trend toward reporting the outcome of hip and knee arthroplasty separately, it remains unknown whether joint-specific reporting is necessary for periprosthetic joint infection (PJI) as sample sizes are already low, given its relatively rare occurrence. The aim of this study is to compare treatment outcomes of PJI occurring after knee and hip arthroplasty. Furthermore, we aim to establish the necessary follow-up time for an accurate reporting of PJI treatment outcomes.

METHODS

A retrospective study of 792 cases of hip and knee PJI treated with irrigation and debridement or two-stage exchange arthroplasty from 2000 to 2017 was performed. Treatment failure was defined based on the Delphi method-based criteria. The Kaplan-Meier survivorship curves were generated, and a log-rank test was used to evaluate differences in survivorship. A multivariate Cox proportional hazards regression and a sensitivity analysis using propensity matching were performed. A two-piecewise linear regression model was used to examine the threshold effect of time after treatment on survival rates.

RESULTS

There were no significant differences between hip and knee PJIs in overall survivorship (P = .71), or when stratified by irrigation and debridement (P = .39), or two-stage exchange arthroplasty (P = .59). There was also no difference by joint in the multivariate or sensitivity analysis. Survival rates had the most dramatic rates of decrease in the initial months after treatment of PJI but began to plateau after 1.09 years.

CONCLUSION

This study reveals no difference in treatment outcomes between knee and hip PJIs. In addition, given the difficulty with obtaining follow-up, we suggest that one-year follow-up is sufficient for an accurate reporting of treatment failure.

Culture-negative periprosthetic joint infection: prevalence, aetiology, evaluation, recommendations, and treatment

PURPOSE

Periprosthetic joint infection (PJI) is a catastrophic complication after total joint arthroplasty (TJA). Treatment of PJI is challenging, especially when causative microorganism is not identified. The purpose of this systematic review was to guide diagnostic approach and treatment of culture-negative (CN) PJI.

METHODS

A systematic review was undertaken on clinical studies from MEDLINE, EMBASE, Cochrane Library, and Scopus databases. Basic science studies, letters, studies written in languages other than English, case reports, and review articles were excluded.

RESULTS

Proportion of CN PJI ranged from 5 to 42% of PJIs. Risk factors for culture negativity included prior use of antibiotic before culture test, inappropriate culture tools, insufficient culture period, and post-operative wound drainage. Specific diagnostic protocols including repeating sampling, longer incubation period, culture in blood culture bottles, sonication of implants, polymerase chain reaction in synovial fluid, and next-generation sequencing are recommended to identify undetected microorganisms. Vancomycin and cephalosporins are the most commonly used antibiotics. Two-stage revision arthroplasty showed success rate of 70-100%.

CONCLUSIONS

A comprehensive review was performed to provide an up-to-date, evidence-based guide to the management of CN PJI.

C-reactive protein may rise after closed-suction drainage removal in patients undergoing revision arthroplasty: a retrospective study

BACKGROUND

Serum C-reactive protein (CRP) has been one of the most commonly used markers to rule out early post-operative infection following total joint arthroplasty. The phenomenon that CRP values rise after prolonged drainage removal may occur in clinical settings. The purpose of this study is to investigate (i) the prevalence and risk factors of such a phenomenon and (ii) whether the raised CRP is associated with post-operative infection.

METHODS

A retrospective review of 72 revision arthroplasties of the knee and hip with prolonged drainage from 2011 to 2016 was conducted. Perioperative CRP levels were obtained, and patients were divided into two groups according to whether CRP levels were elevated after drainage removal (raised CRP group and control group). Multivariate logistic regression analyses were performed to identify risk factors of raised CRP after drainage removal. The incidence of post-operative wound complications and infection was compared between groups.

RESULTS

Overall, the prevalence of raised CRP after drainage removal was 29.17% (21/72). CRP level before drainage removal was associated with the occurrence of such a phenomenon (adjusted odds ratio per 10-mg/L increase 0.92, 95% confidence interval 0.87-0.97). The raised CRP levels decrease again within 3 days after drainage removal. There was no significant difference in the incidence of wound complications and infection between the raised CRP group and control group.

CONCLUSION

Almost one in three patients have raised CRP values after prolonged drainage removal following revision arthroplasty. However, CRP values can decrease again within 3 days after drainage removal without specific management. Almost one in three patients have raised C-reactive protein values after prolonged drainage removal following revision arthroplasty. However, C-reactive protein values can decrease again within 3 days after drainage removal without specific management. Surgeons should remember that such a phenomenon may be not be a proxy for post-operative infection following revision arthroplasty.

The difference between native septic arthritis and prosthetic joint infections: A review of literature

Current literature occasionally considers septic arthritis in native joints and prosthetic joint infections as equal pathologies. However, significant differences can be identified. The aim of this review of literature is to describe these differences in definitions, pathology, diagnostic workups, treatment strategies, and prognosis.

Applicability of histopathological osteomyelitis evaluation score (HOES) in chronic osteomyelitis of the foot - A feasibility study

BACKGROUND

Diagnosis and classification of chronic osteomyelitis is not based on any objective criteria. None of the available methods for this is completely reliable. Tienmann et al. (2014) has described the so called histopathological osteomyelitis evaluation score (HOES) to overcome this limitation. But this has not been externally validated or tested in cases with foot osteomyelitis.

METHODS

We prospectively reviewed the histopathological samples of 30 consecutive patients (30 feet) with foot osteomyelitis managed operatively. There were 19 males and 11 females with an average age of 41.6 (range, 27-63) years. The underlying pathology was spina bifida in 12, Charcot's arthropathy in eleven and post-traumatic in seven patients. The bones involved were calcaneum, talus and fifth metatarsal. Pathological diagnosis was made based on HOES by a single pathologist blinded to the clinical diagnosis and both were compared. Intra- and inter-observer reliability of HOES was assessed by analysing the scores of each patient assigned independently by four different pathologists (blinded to the clinical diagnoses and to each other) at two different occasions one week apart.

RESULTS

All samples showed features of long-standing osteomyelitis. When attempting to classify to "acute on chronic", "chronic" and "quiescent" forms, the pathological diagnosis correlatead with the clinical diagnosis only in 16 cases (53.3 percent). Histological classification to Tienmann's types as per the scoring system yielded three distinct pathological entities that had common histological features with regard to bone, soft tissue and inflammatory infiltration. HOES exhibited excellent intra- and inter-observer reliability.

CONCLUSIONS

HOES is well applicable in foot osteomyelitis both for diagnosis and classification by unambiguous and precise scoring system. This makes diagnostic labelling more accurate and repeatable. The clinical relevance of these histopathological types in guiding management and determining prognosis needs to be investigated further.

Single vs 2-Stage Revision for the Treatment of Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is one of the most devastating complications following total joint arthroplasty, accounting for a projected 10,000 revision surgeries per year by 2030. Chronic PJI is complicated by the presence of bacterial biofilm, requiring removal of components, thorough debridement, and administration of antibiotics for effective eradication. Chronic PJI is currently managed with single-stage or 2-stage revision surgery. To date, there are no randomized, prospective studies available evaluating eradication rates and functional outcomes between the 2 techniques. In this review, both treatment options are described with the most current literature to guide effective surgical decision-making that is cost-effective while decreasing patient morbidity.

High-Performance Liquid Chromatography as a Novel Method for the Determination of α-Defensins in Synovial Fluid for Diagnosis of Orthopedic Infections

The α-defensins (AD) present in synovial fluid have been regarded as constituting the most accurate periprosthetic joint infection (PJI) biomarker. The methods most commonly used for estimating AD as a biomarker are the qualitative Synovasure^® PJI tests, based on the technique of lateral flow, and quantitative enzyme-linked immunosorbent assay (ELISA). Here, we propose a novel test based on detecting α-defensins in synovial fluid by high-performance liquid chromatography (HPLC). Synovial fluid was collected from 157 patients diagnosed with PJI, infectious arthritis (IA), arthrosis, reactive arthritis, and rheumatoid arthritis. AD concentrations in the fluid were determined by HPLC, and these same samples were used for additional diagnostic analyses. The results were statistically processed to calculate cutoff concentrations for PJI and IA. HPLC testing showed a sensitivity of 94% and a specificity of 92% for diagnosis of PJI, and a sensitivity of 97% and a specificity of 87% for diagnosis of IA. Using HPLC, we detected in synovial fluid a combination of three α-defensins: human neutrophil peptides HNP1, HNP2, and HNP3. All measured AD concentration values shown in this work refer to the sum of these three individual concentrations. Our study shows that the HPLC method meets the conditions for measuring precise concentrations of the sum of AD and can be recommended as part of a diagnostic array for PJI and IA diagnostics. By this method, we have verified that higher levels of AD in synovial fluid can also be seen in rheumatoid illnesses, crystal arthropathies, and reactive arthritis.

Differences in Diagnostic Properties Between Standard and Enrichment Culture Techniques Used in Periprosthetic Joint Infections

BACKGROUND

Culture-negative infections can complicate the diagnosis and management of orthopedic infections, particularly periprosthetic joint infections (PJIs). This study aimed to identify differences in rate of detection of infection and organisms between cultured using standard and enriched methods.

METHODS

This retrospective, cross-sectional study evaluated PJI samples obtained between January 2013 and December 2017 at Yokohama City University Hospital. Samples were assessed using standard and enrichment culture techniques. White blood cell counts, C-reactive protein levels, type of microorganism (coagulase-positive or coagulase-negative), and methicillin-resistant Staphylococcus were investigated.

RESULTS

A total of 151 PJI samples were included in the analysis; of these, 68 (45.0%) were positive after standard culture while 83 (55.0%) were positive only after enrichment culture. The mean white blood cell counts and C-reactive protein levels were significantly lower in the enrichment culture group than in the standard culture group (P < .01). The rate of methicillin-resistant Staphylococcus and coagulase-negative Staphylococci was significantly higher in the enrichment culture group than in the standard culture group (P < .01).

CONCLUSION

The enrichment culture method has a higher rate of detection of infection than standard culture techniques and should, therefore, be considered when diagnosing orthopedic infections, particularly PJI.

Reliability of synovial fluid alpha-defensin and leukocyte esterase in diagnosing periprosthetic joint infection (PJI): a systematic review and meta-analysis

BACKGROUND

Synovial fluid proteins had been applied as diagnostic biomarkers for periprosthetic joint infection (PJI) in recent research papers. Thus, this meta-analysis aimed to estimate the diagnostic efficiency of synovial fluid α-defensin and leukocyte esterase (LE) for PJI.

METHODS

We conducted our systematic review by searching the keywords in online databases such as PubMed, Embase, Cochrane, Elsevier, Springer, and Web of Science from the time of database inception to October 2018. Inclusion criteria were as follows: patients who have undergone knee, hip, or shoulder joint replacements; α-defensin or leukocyte esterase (LE strip) of synovial fluid was detected as the biomarker for PJI diagnosis; and Musculoskeletal Infection Society (MSIS) or utilizing a combination of clinical data was considered as the gold standard. Diagnostic parameters including sensitivity, specificity, diagnostic odds ratio (DOR), and area under the summary of receiver operating characteristics curve (AUSROC) were calculated for the included studies to evaluate the synovial fluid α-defensin and LE for PJI diagnosis.

RESULTS

After full-text review, 28 studies were qualified for this systematic review, 16 studies used α-defensin and the other 12 were conducted using LE strip. The pooled sensitivity, specificity, and DOR of LE strip were 87% (95% CI 84-90%), 96% (95% CI 95-97%), and 170.09 (95% CI 97.63-296.32), respectively, while the pooled sensitivity, specificity, and DOR of α-defensin were 87% (95% CI 83-90%), 97% (95% CI 96-98%), and 158.18 (95% CI 74.26-336.91), respectively. The AUSROC for LE strip and α-defensin were 0.9818 and 0.9685, respectively.

CONCLUSION

Both LE strip and α-defensin of synovial fluid provide rapid and convenient diagnosis for PJI. Sensitivity of α-defensin and LE strip are the same, while both these two methods have high specificity in clinical practice.

Does serum interleukin-6 guide the diagnosis of persistent infection in two-stage hip revision for periprosthetic joint infection?

PURPOSE

The diagnosis of persistent infection at reimplantation of two-stage revision arthroplasty for periprosthetic joint infection (PJI) remains challenging. Several studies have shown the benefit of serum interleukin-6 (IL-6) in diagnosing periprosthetic joint infection (PJI). Recent data indicated serum IL-6 could be promising in differentiating persistent infection. The purpose of this study was to validate the efficacy of serum IL-6 in diagnosing persistent infection at reimplantation.

METHODS

A retrospective review of 86 PJI patients with a two-stage exchanged hip arthroplasty from 2013 to 2017 was conducted. Persistent infection was defined using the modified Musculoskeletal Infection Society (MSIS) criteria combined with follow-up results. Serum IL-6 at reimplantation were collected and compared among patients with or without persistent infection. Receiver operating characteristic (ROC) curves were generated to evaluate the diagnostic performance and optimal cut-off value of serum IL-6 at reimplantation.

RESULTS

Sixteen cases were diagnosed as persistent infection at reimplantation. There was no significant difference in serum IL-6 levels between cases with persistent infection and controls (7.89 pg/ml vs. 5.56 pg/ml; P = 0.179). The area under the ROC curve (AUC) for serum IL-6 in diagnosing persistent infection at reimplantation was 0.59 (95% confidential interval [CI] 0.40-0.77). With the calculated threshold set at 8.12 pg/ml, the corresponding sensitivity, specificity, positive predictive value, and negative predictive values were 38%, 88%, 38%, and 87%, respectively.

CONCLUSION

Serum IL-6 is inadequate in diagnosing persistent infection at reimplantation for two-stage revision arthroplasty. With the serum IL-6 threshold set at 8.12 pg/ml, the specificity to rule out persistent infection is high, but the sensitivity to predict persistent infection is not satisfactory.

Reevaluating Current Cutoffs for Acute Periprosthetic Joint Infection: Current Thresholds Are Insensitive

BACKGROUND

Diagnosing acute periprosthetic joint infection remains a challenge. Several studies have proposed different acute cutoffs resulting in the International Consensus Meeting recommending a cutoff of 100 mg/L, 10,000 cell/μL and 90% for serum C-reactive protein (CRP), synovial white blood cell count (WBC), and polymorphonuclear percentage (PMN%), respectively. However, establishing cutoffs are difficult as the control group is limited to rare early aseptic revisions, and performing aspiration in asymptomatic patients is difficult because of a fear of seeding a well-functioning joint arthroplasty. This study (1) assessed the sensitivity of current thresholds for acute periprosthetic joint infection (PJI) and (2) identified associated factors for false negatives.

METHODS

We retrospectively reviewed patients with acute PJIs (n = 218), defined as less than 6 weeks from index arthroplasty, treated between 2000 and 2017. Diagnosis of PJI was based on 2 positive cultures of the same pathogen from the periprosthetic tissue or synovial fluid samples. Sensitivities of International Consensus Meeting cutoff values of CRP, synovial WBC, and PMN% were evaluated according to organism type. Multiple logistic regression analysis was performed to determine associated factors for false negatives.

RESULTS

Overall, the sensitivity of CRP, synovial WBC, and PMN% for acute PJI was 55.3%, 59.6%, and 50.5%, respectively. Coagulase-negative Staphylococcus (CNS) demonstrated the lowest sensitivity for both CRP (37.5%) and WBC (55.6%). CNS infection was identified as an independent risk factor for false-negative CRP.

CONCLUSIONS

Current thresholds for acute PJI may be missing approximately half of PJIs. Low virulent organisms, such as CNS, may be responsible for these false negatives. Current thresholds for acute PJI must be reexamined.