Diagnosis of periprosthetic joint infection

An overview of the current diagnostic approach to Periprosthetic Joint Infections

The diagnosis of periprosthetic joint infections (PJI) presents a formidable challenge to orthopaedic surgeons due to its complex and diverse manifestations. Accurate diagnosis is of utmost importance, as even mild pain following joint replacement surgery may indicate PJI in the absence of a definitive gold standard diagnostic test. Numerous diagnostic modalities have been suggested in the literature, and international societies have continually updated diagnostic criteria for this debilitating complication. This review article aims to comprehensively examine the latest evidence-based approaches for diagnosing PJI. Through a thorough analysis of current literature, we explore promising diagnostic strategies that have demonstrated effectiveness in identifying PJI. These strategies encompass the utilization of laboratory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), alongside imaging techniques such as magnetic resonance imaging (MRI) and leukocyte scintigraphy. Additionally, we highlight the importance of synovial fluid analysis, including the potential role of alpha-defensin as a biomarker, and examine evolving international diagnostic criteria to standardize and improve diagnostic accuracy.

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.

Clinical Outcomes After Revision Hip Arthroplasty due to Prosthetic Joint Infection-A Single-Center Study of 369 Hips at a High-Volume Center With a Minimum of One Year Follow-Up

BACKGROUND

Prosthetic joint infection (PJI) treatment decisions are traditionally based on treatment algorithms. There is, however, a lack of evidence to support the choice of these treatment algorithms. Therefore, we aimed to assess the one-year survival after PJI revision and compared different surgical strategies in a single-center setting.

METHODS

Revisions of the hip due to PJI performed at our institution between January 2008 and September 2021 with at least one-year of follow-up were identified. In total, 134 debridement, antibiotics, and implant retentions (DAIRs), 114 one-stage revisions, and 121 two-stage revisions were performed. Infections were classified as early, acute hematogenous, and chronic. Survival was calculated using the Kaplan-Meier method and cumulative incidence function. Predictors of outcomes were examined with Fine-Gray regressions and Cox proportional hazards regressions. Subdistribution hazard ratios and hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated.

RESULTS

At one-year follow-up, 26.6% (CI 22.2 to 31.2%) of the patients had undergone reoperation and 7.9% (CI 5.4 to 10.9%) had died. The risk for reoperation was highest after DAIR (36.6%, CI 28.5 to 44.7%) and lowest after one-stage revision (20.2%, CI 13.4 to 28%). Within the early infections, the one-stage revision almost halved the risk of reoperation (HR 0.51, CI 0.31 to 0.84) with no added mortality risk (HR 1.05, CI 0.5 to 2.2), when compared to DAIR.

CONCLUSION

By utilizing 1-stage revision over DAIR in early infections, it might be possible to improve the prognosis by decreasing the risk of reoperation without increasing mortality. However, as the patient selection is undeniably difficult, more research is warranted.

Trends in Revision Knee Arthroplasty for Prosthetic Joint Infection: A Single-Center Study of 384 Knees at a High-Volume Center Between 2008 and 2021

BACKGROUND

Prosthetic joint infection (PJI) is one of the most devastating complications after total knee arthroplasty (TKA), and comorbidities increase the risk. We examined whether a temporal change has occurred in the demographics, especially regarding comorbidities, of patients who have PJI and were treated at our institution over a 13-year study period. In addition, we assessed the surgical methods used and the microbiology of the PJIs.

METHODS

Revisions (n = 384, 377 patients) due to PJI of the knee performed at our institution between 2008 and September 2021 were identified. All included PJIs fulfilled the 2013 International Consensus Meeting diagnostic criteria. The surgeries were categorized into one of the following categories: debridement, antibiotics, and retention (DAIR), 1-stage revision, and 2-stage revision. Infections were classified as early, acute hematogenous, and chronic.

RESULTS

No changes in the median age of the patients nor comorbidity burden were observed during the study period. However, the proportion of 2-stage revisions decreased remarkably from 57.6% in 2008 to 2009 to 6.3% in 2020 to 2021. A DAIR was the most used treatment strategy, but the proportion of 1-stage revisions increased the most. In 2008 to 2009, 12.1% of the revisions were 1-stage, but in 2020 to 2021, the proportion was 43.8%. The most common pathogen was Staphylococcus aureus (27.8%).

CONCLUSION

The comorbidity burden remained at the same level with no trends. A DAIR was the most used strategy, but the proportion of 1-stage revisions rose to almost the same level. The incidence of PJI varied between the years, but remained relatively low.

Diagnosis of Periprosthetic Joint Infection: The Utility of Biomarkers in 2023

Periprosthetic joint infection (PJI) is a rare yet devastating complication following total joint arthroplasty (TJA). Early and accurate diagnosis of PJI is paramount in order to maximize the chances of successful treatment. However, we are yet to identify a single "gold standard" test for the diagnosis of PJI. As a result, the diagnosis of PJI is often challenging. Currently, the 2018 ICM definition of PJI is the only validated diagnostic criteria available. This article will review the importance of serum and synovial biomarkers in the diagnosis of PJI. In addition, it will provide a brief overview of the emerging modalities for the identification of infections in this setting.

Trends in Revision Hip Arthroplasty for Prosthetic Joint Infection: A Single-Center Study of 423 Hips at a High-Volume Center Between 2008 and 2021

BACKGROUND

Prosthetic joint infection (PJI) is one of the most devastating complications after total hip arthroplasty (THA), and comorbidities increase the risk. We examined whether there was a temporal change in the demographics, especially regarding comorbidities, of patients who have PJIs and were treated over a 13-year study period at a high-volume academic joint arthroplasty center. In addition, the surgical methods used and the microbiology of the PJIs were assessed.

METHODS

Revisions (n = 423, 418 patients) due to PJI of the hip performed at our institution between 2008 and September 2021 were identified. All included PJIs fulfilled the 2013 International Consensus Meeting diagnostic criteria. The surgeries were categorized into one of the following categories: debridement, antibiotics, and implant retention, 1-stage revision, and 2-stage revision. Infections were classified as early, acute hematogenous, and chronic infections.

RESULTS

There was no change in the median age of the patients, but the proportion of ASA-class 4 patients increased from 10.5% to 20%. The incidence of early infections increased from 0.11 per 100 primary THAs in 2008 to 1.09 in 2021. The incidence of 1-stage revisions increased the most, rising from 0.10 per 100 primary THAs in 2010 to 0.91 per 100 primary THAs in 2021. Furthermore, the proportion of infections caused by Staphylococcus aureus increased from 26.3% in 2008 to 2009 to 40% in 2020 to 2021.

CONCLUSION

The comorbidity burden of PJI patients increased during the study period. This increase may present a treatment challenge, as comorbidities are known to have a negative effect on PJI treatment outcomes.

The Challenge of Periprosthetic Joint Infection Diagnosis: From Current Methods to Emerging Biomarkers

Due to the increase in the life span and mobility at older ages, the number of implanted prosthetic joints is constantly increasing. However, the number of periprosthetic joint infections (PJIs), one of the most severe complications after total joint arthroplasty, also shows an increasing trend. PJI has an incidence of 1-2% in the case of primary arthroplasties and up to 4% in the case of revision operations. The development of efficient protocols for managing periprosthetic infections can lead to the establishment of preventive measures and effective diagnostic methods based on the results obtained after the laboratory tests. In this review, we will briefly present the current methods used in PJI diagnosis and the current and emerging synovial biomarkers used for the prognosis, prophylaxis, and early diagnosis of periprosthetic infections. We will discuss treatment failure that may result from patient factors, microbiological factors, or factors related to errors during diagnosis.

A high prevalence of Cutibacterium acnes infections in scoliosis revision surgery, a diagnostic and therapeutic dilemma

PURPOSE

To investigate if serum inflammatory markers or nuclear imaging can accurately diagnose a chronic spinal instrumentation infection (SII) prior to surgery.

METHODS

All patients who underwent revision of spinal instrumentation after a scoliosis correction between 2017 and 2019, were retrospectively evaluated. The diagnostic accuracy of serum C-reactive protein (CRP) and Erythrocyte Sedimentation Rate (ESR), ¹⁸F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) and Technetium-99m-methylene diphosphonate (99mTc-MDP) 3-phase bone scintigraphy (TPBS) to diagnose infection were studied. Patients with an acute infection or inadequate culture sampling were excluded. SII was diagnosed if ≥ 2 of the same microorganism(s) were isolated from intra-operative tissue cultures.

RESULTS

30 patients were included. The indication for revision surgery was pseudoarthrosis in the majority of patients (n = 15). 22 patients (73%) were diagnosed with SII. In all infected cases, Cutibacterium acnes was isolated, including 5 cases with a polymicrobial infection. The majority of patients had low inflammatory parameters preoperatively. For CRP > 10.0 mg/L, the sensitivity was 9.1% and specificity 100%; for ESR > 30 mm/h, the sensitivity was 9.1% and specificity 100%. The diagnostic accuracy for nuclear imaging was 64% for the FDG-PET/CT and 67% for the TPBS to diagnose infection.

CONCLUSIONS

The prevalence of SII in patients undergoing revision spinal surgery is high, with Cutibacterium acnes as the main pathogen. No diagnostic tests could be identified that could accurately diagnose or exclude SII prior to surgery. Future studies should aim to find more sensitive diagnostic modalities to detect low-grade inflammation.

Periprosthetic joint infections of the shoulder: A 10-year retrospective analysis outlining the heterogeneity among these patients

Background

Diagnosis and treatment of shoulder periprosthetic joint infection is a difficult problem. The purpose of this study was to utilize the 2018 International Consensus Meeting definition of shoulder periprosthetic joint infection to categorize revision shoulder arthroplasty cases and determine variations in clinical presentation by presumed infection classification.

Methods

Retrospective review of patients undergoing revision shoulder arthroplasty at a single institution. Likelihood of periprosthetic joint infection was determined based on International Consensus Meeting scoring. All patients classified as definitive or probable periprosthetic joint infection were classified as periprosthetic joint infection. All patients classified as possible or unlikely periprosthetic joint infection were classified as aseptic. The periprosthetic joint infection cohort was subsequently divided into culture-negative, non-virulent microorganism, and virulent microorganism cohorts based on culture results.

Results

Four hundred and sixty cases of revision shoulder arthroplasty were reviewed. Eighty (17.4%) patients were diagnosed as definite or probable periprosthetic joint infection, of which 29 (36.3%), 39 (48.8%), and 12 (15.0%) were classified as virulent, non-virulent, or culture-negative periprosthetic joint infection, respectively. There were significant differences among periprosthetic joint infection subgroups with regard to preoperative C-reactive protein (p = 0.020), erythrocyte sedimentation rate (p = 0.051), sinus tract presence (p = 0.008), and intraoperative purulence (p < 0.001). The total International Consensus Meeting criteria scores were also significantly different between the periprosthetic joint infection cohorts (p < 0.001).

Discussion

While the diagnosis of shoulder periprosthetic joint infection has improved with the advent of International Consensus Meeting criteria, there remain distinct differences between periprosthetic joint infection classifications that warrant further investigation to determine the accurate diagnosis and optimal treatment.

Comparative diagnostic accuracy of respective nuclear imaging for suspected fracture-related infection: a systematic review and Bayesian network meta-analysis

BACKGROUND

The aim of this study was to compare the accuracy of available nuclear imaging modalities in the diagnosis of suspected fracture-related infection (FRI).

METHODS

We conducted a comprehensive literature search of PubMed, EMBASE and the Cochrane Library to retrieve diagnostic accuracy studies in which FRI was investigated using different nuclear imaging modalities. The pooled sensitivity, specificity, likelihood ratios and diagnostic odds ratios were constructed using the bivariate meta-analysis framework, while the superior index was pooled using Bayesian network meta-analysis.

RESULTS

22 eligible studies (1,565 patients) were included in the quantitative analysis. A broad overlapping confidence interval (CI) of pooled sensitivity was observed among bone scintigraphy (0.94; 95% CI 0.85-0.98), ¹⁸F-FDG PET and PET/CT (0.91; 95% CI 0.85-0.94) and leukocyte scintigraphy (0.86; 95% CI 0.53-0.97). Bone scintigraphy (0.34; 95% CI 0.08-0.75) seemed to be less specific than all the other modalities, while leukocyte scintigraphy (0.96, 95% CI 0.92-0.98) was notably more specific than ¹⁸F-FDG PET and PET/CT (0.78; 95% CI 0.69-0.85). Based on the superiority index, ¹⁸F-FDG PET/CT (3.78; 95% CI 0.14-11.00), ¹⁸F-FDG PET (2.98; 95% CI 0.14-9.00) and leukocyte scintigraphy (1.51; 95% CI 0.11-7.00) all achieved high accuracy in detecting FRI.

CONCLUSION

Bone scintigraphy is a highly sensitive nuclear imaging technique but lacks the specificity needed to unequivocally differentiate among various conditions suspected to be FRI. Leukocyte scintigraphy, ¹⁸F-FDG PET/CT and PET all present good satisfactory accuracy for the diagnosis of FRI, but their costs should be further reduced to promote their wide application.

Diagnostic algorithm in septic total knee arthroplasty failure - What is evidence-based?

Prosthetic joint infection (PJI) is among the most common differential diagnoses of total knee arthroplasty failure. It is a challenging complication, not least because of the difficulty of establishing the correct diagnosis. The fact that no single diagnostic parameter or test has been identified that can accurately rule in or out PJI has led to an evolution of similar but competing definitions of PJI on the grounds of an array of criteria. This development has had very positive effects on the scientific evaluation of various methods of PJI diagnostics and treatment because of an increased comparability. However, it can be challenging to stay abreast of the evidence these definitions are based on. Also, the definitions alone do not necessarily entail an algorithm to aid in evaluating the right criteria in a sound order to be able to use the definitions as a sensible tool. The aim of this overview is to state the most recent evidence on the diagnostic parameters included in the most established PJI definitions and to exhibit and compare the few algorithmic approaches published. Clinical symptoms of PJI are very rarely reported on in the literature, hence the evidence on their diagnostic value is poor. The only symptom that is part of the established PJI definitions is the presence of a fistula. Concerning serological markers, CRP and ESR are still the common denominator in the literature, most recently accompanied by D-Dimer as a potentially suitable marker that has been included in the most recent update of the International Consensus Meeting (ICM) criteria. Imaging plays a minor role in the diagnostic cascade because of inconsistent evidence, and no role whatsoever in the established definitions. The most important preoperative diagnostic measure is arthrocentesis and cultural and cytological analysis of the synovial fluid. The much acclaimed α-Defensin test has so far not been included in the established criteria due to inconsistent reports on its diagnostic accuracy, it is, however, in wide use and considered an optional diagnostic tool for inconclusive cases. The most diagnostic accuracy lies in the cultural and histological analysis of periprosthetic tissue biopsies, whether they are gathered in a small procedure or during arthroplasty revision. Published algorithmic approaches to PJI diagnosis are much rarer than the well-established definitions by various associations. With their PJI definition, the American Academy of Orthopedic Surgeons (AAOS) published a consensus based flowchart for PJI diagnosis. Another algorithm was proposed as part of the endeavor of the MSIS and the first consensus meeting, also based on a consensus among experts. There have been two more recent publications of flowcharts based on the current evidence, one introduced at our institution in 2013, one established in 2020 by the German Society for Arthroplasty (AE).

Diagnostic value of the CD 15 focus score in two-stage revision arthroplasty of periprosthetic joint infections : High specificity in diagnosing infect eradication

INTRODUCTION

The purpose of this study is to use the CD15 focus score (FS) to determine the sensitivity and specificity of bacterial infection persistence in spacer-based two-stage revision arthroplasty.

METHODS

The analysis comprises 112 cases that were subjected to revision due to the presence of infection upon replacement of a joint endoprosthesis. The histopathological data were collected in accordance with the synovial-like interface membrane (SLIM) classification and the CD15-FS and correlated with the microbiological data (MD). The quantifying evaluation of the CD15-FS was performed without knowledge regarding the microbiological data (MD). Correlation with the MD was performed after a 14-day cultivation period.

RESULTS

With a single evaluation (1 focus, field area: 1.2 mm2) with a score value of 42, the CD15-FS showed a sensitivity for the eradication of infections of 0.64 and a specificity of 0.79 (PPV = 0.5; NPV = 0.87). With tenfold evaluation (10 foci, field area: 12 mm2) with a score value of 220, the sensitivity for the eradication was 0.68, the specificity 0.91 (PPV = 0.7; NPV = 0.89). No statistically significant correlation between the score values and the different infectious species could be detected. Based on the MD in 112 cases the rate of infection eradication was 75%. Polymethylmethacrylate-particles (PMMA) were detected in the perispacertissue in 64 cases (58%). No significant correlation could be established between microbiological pathogen detection and the presence of PMMA.

CONCLUSION

In all cases (n = 112), periimplant synovial tissue (SLIM) with variable fibroblastic cellularity, capillary proliferation, leukocytic infiltration, fibrin deposition, new formation of woven bone and detection of PMMA particles was observed. These cases were classified as type IX perispacer synovialis/SLIM: type IX‑A with histopathological infection eradication and type IX‑B with histopathological infection persistence.

The management of infected shoulder arthroplasty by two-stage revision

BACKGROUND

There remains no gold standard management for deep shoulder periprosthetic joint infection (PJI). This case series aims to present our experience of two-stage revision arthroplasty, including eradication of infection and reoperation rates.

METHODS

We retrospectively reviewed patients undergoing revision arthroplasty for shoulder PJI between 2006 and 2015. Cases were confirmed using Musculoskeletal Infection Society (MSIS) and American Academy of Orthopaedic Surgeons (AAOS) guidelines. TSA removal, debridement and irrigation preceded antibiotic-loaded cement spacer insertion and a minimum of six weeks intravenous antibiotics. Reimplantation was performed as a second stage following a negative aspirate.

RESULTS

Twenty-eight patients underwent a first stage procedure (mean age 69 years; 16 male, 12 female). Propionibacterium acnes, Methicillin-sensitive Staphylococcus aureus, Coagulase-negative Staphylococcus and Staphylococcus epidermidis were the commonest microorganisms cultured. Five cases had mixed growths and six cases provided no growth. Three patients did not proceed to a second stage. Twenty-five patients underwent reimplantation (mean interval 6.7 months), with 80% remaining infection-free (mean follow-up 38.3 months).

DISCUSSION

Managing complex and late presentation shoulder PJI with two-stage revision is associated with high rates of infection eradication (80%). In the absence of a management consensus, our experience supports two-stage revision arthroplasty for eradicating infection in this complex patient group.

A decision analysis of treatment strategies for acute periprosthetic joint infection: Early irrigation and debridement versus delayed treatment based on organism

OBJECTIVE

The purpose of this study was to investigate whether immediate or delayed tailored DAIR treatment based on microbial species is the optimal treatment for acute post-operative periprosthetic joint infection (PJI).

METHODS

A multicenter retrospective study was conducted to identify patients who underwent debridement, antibiotics, and implant retention (DAIR) for PJI. Decision analysis modeling was employed to determine the treatment strategy that yielded the greatest patient outcome.

RESULTS

316 patients who underwent DAIR for PJI were identified.

CONCLUSION

The decision analysis model determined that the optimal treatment strategy is to perform an immediate DAIR to achieve the greatest QALY outcomes in TKA and THA patients with acute PJI.

Trends in the treatment of infected knee arthroplasty

Essential treatment methods for infected knee arthroplasty involve DAIR (debridement, antibiotics, and implant retention), and one and two-stage exchange arthroplasty.Aggressive debridement with the removal of all avascular tissues and foreign materials that contain biofilm is mandatory for all surgical treatment modalities.DAIR is a viable option with an acceptable success rate and can be used as a first surgical procedure for patients who have a well-fixed, functioning prosthesis without a sinus tract for acute-early or late-hematogenous acute infections with no more than four weeks (most favourable being < seven days) of symptoms. Surgeons must focus on the isolation of the causative organism with sensitivities to bactericidal treatment as using one-stage exchange.One-stage exchange is indicated when the patients have:minimal bone loss/soft tissue defect allowing primary wound closure,easy to treat micro-organisms,absence of systemic sepsis andabsence of extensive comorbidities.There are no validated serum or synovial biomarkers to determine optimal timing of re-implantation for two-stage exchange.Antibiotic-free waiting intervals and joint aspiration before the second stage are no longer recommended. The decision to perform aspiration should be made based on the index of suspicion for persistent infection.Re-implantation can be performed when the treating medical team feels that the clinical signs of infection are under control and serological tests are trending downwards. Cite this article: EFORT Open Rev 2020;5:672-683. DOI: 10.1302/2058-5241.5.190069.

D-dimer in the diagnosis of periprosthetic joint infection: a systematic review and meta-analysis

BACKGROUND

D-dimer, a coagulation-related indicator, has recently been used as a tool for the diagnosis of periprosthetic joint infection (PJI), but its reliability is uncertain. The purpose of this systematic review and meta-analysis was to explore the accuracy of D-dimer in the diagnosis of PJI after joint arthroplasty.

METHODS

We systematically searched the MEDLINE, EMBASE, and Cochrane databases for relevant literature about D-dimer in the diagnosis of PJI. QUADAS-2 was used to assess the risk of bias and clinical applicability of each included study. We used the bivariate meta-analysis framework to pool the sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under the SROC curve (AUC). Univariate meta-regression and subgroup analyses were performed to explore the sources of heterogeneity.

RESULTS

We included 8 eligible studies. The pooled diagnostic sensitivity and specificity were 0.82 (95% CI, 0.70-0.89) and 0.70 (95% CI, 0.55-0.82), respectively. The pooled PLR, NLR, and DOR were 2.7 (95% CI, 1.7-4.4), 0.26 (95% CI, 0.15-0.46), and 10 (95% CI, 4-25), respectively. The AUC was 0.83 (95% CI, 0.8-0.86). Serum D-dimer might have higher diagnostic accuracy than plasma D-dimer for PJI (pooled sensitivity: 0.88 vs 0.67; pooled specificity: 0.76 vs 0.61).

CONCLUSIONS

D-dimer has limited performance for the diagnosis of PJI.

Loosening of total knee arthroplasty - always aseptic?

PURPOSE

When revision surgery is needed in total knee arthroplasty (TKA) the most frequent reasons are aseptic loosening (AL) and periprosthetic joint infection (PJI). However preoperative distinction between AL and PJI remains challenging. Aim of this study is to determine the incidence of PJI in patients with suspected AL after TKA and to evaluate a diagnostic algorithm for reliable differential diagnosis.

METHODS

In this study a total of 149 symptomatic patients with radiographic signs of prosthetic loosening and suspected AL were included. Preoperatively all patients underwent a standardized diagnostic algorithm. For each patient demographics, as well as the results of laboratory and microbiological testing were collected from the medical records.

RESULTS

Of the included patients 117 (78.5%) were diagnosed with AL and 32 (21.5%) with PJI. The latency period from primary arthroplasty to the presentation with symptomatic implant loosening was significantly shorter for PJI compared to AL (p < 0.05). The initial CRP values were significantly higher in patients with PJI compared to patients with AL (p < 0.05). Elevated count of white blood cells or percentage of neutrophils within the synovial fluid support the diagnosis of PJI. The sensitivity of synovial cell count (CC) count for PJI in patients with radiographic signs of loosening was 0.84 (CI 0.81-0.87) with a specificity of 0.96 (CI 0.92-0.98). The single best measure for the diagnosis of PJI was synovial fluid cultures with a specificity of 1, however this measure provides poor sensitivity.

CONCLUSION

Patients with radiographic signs of loosening in TKA need thorough diagnostics. Information about primary TKA, serological testing, and results of joint aspiration can rule out a PJI in most cases.

Good accuracy of the alpha-defensin lateral flow test for hip periprosthetic joint infection: A pilot study in a retrospective cohort of 52 patients

BACKGROUND

The alpha-defensin lateral flow (ADLF) test is a new diagnostic tool for periprosthetic joint infection (PJI). Test accuracy for combined cohorts of hip and knee PJI has been reported to be good.

AIM

To assess the accuracy of the ADLF test for hip PJI, and to compare three different diagnostic criteria for PJI.

METHODS

A cohort of 52 patients was identified, with a painful or poorly functioning total hip- or hemi-arthroplasty, that underwent aspiration and a subsequent ADLF test. PJI was diagnosed with Musculoskeletal Infection Society (MSIS) criteria, and sensitivity, specificity, overall accuracy, positive predictive value and negative predictive value were calculated. Furthermore, test specifics were compared with the European Bone and Joint Infection Society (EBJIS) and 2018 International Consensus Meeting (ICM) criteria for PJI.

RESULTS

Using MSIS criteria, sensitivity was 100% (CI: 54%-100%) and specificity was 89% (CI: 76%-96%). Six true positives and 5 false positives were found, including one case of metallosis. Using EBJIS criteria, more PJIs were found (11 vs 6), sensitivity was lower (71%, CI: 42%-92%) and specificity was higher (97%, CI: 86%-100%), with 4 false negatives and one false positive result. Using 2018 ICM criteria, sensitivity was 91% (62%-100%) and specificity 100% (91%-100%). The results in this cohort are comparable to previous studies.

CONCLUSION

Overall test accuracy of the ADLF test was good in this cohort, with a sensitivity of 100% and specificity of 89%. Using different PJI definition criteria, sensitivity and specificity changed slightly but overall accuracy remained around 90%. Using the ADLF test in metallosis cases can result in false positive results and should be performed with caution.

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.

72 revision surgeries for aseptic failure after hip or knee arthroplasty: a prospective study with an extended diagnostic algorithm

BACKGROUND

Unrecognized periprosthetic joint infections are a concern in revision surgery for aseptic failure (AF) after total hip (THA) or knee (TKA) arthroplasties. A gold diagnostic standard does not exist. The aim of the current study was to determine the prevalence of unrecognized periprosthetic joint infection (PJI) in a cohort of revision for AF, using an experimental diagnostic algorithm.

METHODS

The surgeons' suspicion of AF was based primarily on patient history and clinical evaluation. X-ray imaging was used to reveal mechanical problems. To rule out an infectious aetiology standard blood biochemical tests were ordered in most patients. Evaluation followed the existing practice in the institute. Cases were included if revision surgery was planned for suspected AF. Intraoperatively, five synovial tissue biopsies were obtained routinely. PJI was defined as ≥3 positive cultures with the same microorganism(s). Patients were followed for 1 year postoperatively. Protocol samples included joint fluid, additional synovial tissue biopsies, bone biopsy, swabs from the implant surface, and sonication of retrieved components. Routine and protocol samples were cultured with extended incubation (14 days) and preserved for batchwise 16S rRNA gene amplification. Patients were stratified based on culture results and a clinical status was obtained at study end.

RESULTS

A total of 72 revisions were performed on 71 patients (35 THA and 37 TKA). We found five of 72 cases of unrecognized PJI. Extended culture and protocol samples accounted for two of these. One patient diagnosed with AF was treated for a PJI during follow-up. The remaining patients did not change status from AF during follow-up.

CONCLUSIONS

We found a low prevalence of unrecognized periprosthetic joint infections in patients with an AF diagnosis. The algorithm strengthens the surgeons' preoperative diagnosis of a non-infective condition. Evaluation for a failing TKA or THA is complex. Distinguishing between AF and PJI pre-operatively was a clinical decision. Our data did not support additional testing in routine revision surgery for AF.

Predictors of Treatment Failure for Hip and Knee Prosthetic Joint Infections in the Setting of 1- and 2-Stage Exchange Arthroplasty: A Multicenter Retrospective Cohort

Background

Prosthetic hip and knee joint infections (PJIs) are challenging to eradicate despite prosthesis removal and antibiotic therapy. There is a need to understand risk factors for PJI treatment failure in the setting of prosthesis removal.

Methods

A retrospective cohort of individuals who underwent prosthesis removal for a PJI at 5 hospitals in Toronto, Canada, from 2010 to 2014 was created. Treatment failure was defined as recurrent PJI, amputation, death, or chronic antibiotic suppression. Potential risk factors for treatment failure were abstracted by chart review and assessed using a Cox proportional hazards model.

Results

A total of 533 individuals with prosthesis removal were followed for a median (interquartile range) of 814 (235–1530) days. A 1-stage exchange was performed in 19% (103/533), whereas a 2-stage procedure was completed in 88% (377/430). Treatment failure occurred in 24.8% (132/533) at 2 years; 53% (56/105) of recurrent PJIs were caused by a different bacterial species. At 4 years, treatment failure occurred in 36% of 1-stage and 32% of 2-stage procedures (P = .06). Characteristics associated with treatment failure included liver disease (adjusted hazard ratio [aHR], 3.12; 95% confidence interval [CI], 2.09–4.66), the presence of a sinus tract (aHR, 1.53; 95% CI, 1.12–2.10), preceding debridement with prosthesis retention (aHR, 1.68; 95% CI, 1.13–2.51), a 1-stage procedure (aHR, 1.72; 95% CI, 1.28–2.32), and infection due to Gram-negative bacilli (aHR, 1.35; 95% CI, 1.04–1.76).

Conclusions

Failure of PJI therapy is common, and risk factors are not easily modified. Improvements in treatment paradigms are needed, along with efforts to reduce orthopedic surgical site infections.

Integrated IT Platform for Coordination of Diagnosis, Treatment, and Aftercare of Prosthetic Joint Infections

BACKGROUND/AIM

Prosthetic joint infections (PJI) are difficult to diagnose and treat. For a correct diagnosis, an array of information has to be processed and weighted. Successful treatment depends on the diagnosis, timing, and surgical strategy paired with treatment of the infectious agent. The complexity and interdisciplinarity needed cause difficulties concerning decision-making, the communication between disciplines, and the execution of a treatment strategy. The aim of this study was to develop a software platform to enhance the collection of information for the diagnosis of PJI, the interdisciplinary decision-making process, the communication between team members, and continuous evaluation of treatment.

PATIENTS AND METHODS

In regular planning sessions with an information technology (IT) specialist, a concept for an IT solution was chosen and the tool was designed in an interdisciplinary approach.

RESULTS

The tool has been used as a trial version since June 2017. It consists of 14 user interfaces with 431 items. A total of 117 patients with 118 infections have been entered and the strategy decided upon and communicated using 298 infection board documents outlining the treatment. The tool is now being used to organize the infections board agenda, schedule patient case discussions, document the relevant data and treatment plan, as well as communicate with the other teams involved in the treatment.

CONCLUSION

Using the developed tool enables the infections team to work collaboratively and under division of labor on each case, rendering the work flow more efficient for each team member.

Periprosthetic joint infection: current concepts and outlook

Periprosthetic joint infection (PJI) is a serious complication occurring in 1% to 2% of primary arthroplasties, which is associated with high morbidity and need for complex interdisciplinary treatment strategies.

The challenge in the management of PJI is the persistence of micro-organisms on the implant surface in the form of biofilm. Understanding this ability, the phases of biofilm formation, antimicrobial susceptibility and the limitations of host local immune response allows an individual choice of the most suitable treatment.

By using diagnostic methods for biofilm detection such as sonication, the sensitivity for diagnosing PJI is increasing, especially in chronic infections caused by low-virulence pathogens.

The use of biofilm-active antibiotics enables eradication of micro-organisms in the presence of a foreign body. The total duration of antibiotic treatment following revision surgery should not exceed 12 weeks.

Cite this article: EFORT Open Rev 2019;4:482-494. DOI: 10.1302/2058-5241.4.180092

Therapeutic effect of ethylenediaminetetraacetic acid irrigation solution against wound infection with drug-resistant bacteria in a rat model: an animal study

Objectives

Irrigation is the cornerstone of treating skeletal infection by eliminating pathogens in wounds. A previous study shows that irrigation with normal saline (0.9%) and ethylenediaminetetraacetic acid (EDTA) could improve the removal of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) compared with normal saline (NS) alone. However, it is still unclear whether EDTA solution is effective against infection with drug-resistant bacteria.

Methods

We established three wound infection models (skin defect, bone-exposed, implant-exposed) by inoculating the wounds with a variety of representative drug-resistant bacteria including methicillin-resistant S. aureus (MRSA), extended spectrum beta-lactamase-producing E. coli (ESBL-EC), multidrug-resistant Pseudomonas aeruginosa (MRPA), vancomycin-resistant Enterococcus (VRE), multidrug-resistant Acinetobacter baumannii (MRAB), multidrug-resistant Enterobacter (MRE), and multidrug-resistant Proteus mirabilis (MRPM). Irrigation and debridement were repeated until the wound culture became negative. The operating times required to eliminate pathogens in wounds were compared through survival analysis.

Results

Compared with other groups (NS, castile soap, benzalkonium chloride, and bacitracin), the EDTA group required fewer debridement and irrigation operations to achieve pathogen eradication in all three models of wound infection.

Conclusion

Irrigation with EDTA solution was more effective than the other irrigation fluids used in the treatment of wound infections caused by drug-resistant pathogens.

Cite this article: Z. Deng, F. Liu, C. Li. Therapeutic effect of ethylenediaminetetraacetic acid irrigation solution against wound infection with drug-resistant bacteria in a rat model: an animal study. Bone Joint Res 2019;8:189–198. DOI: 10.1302/2046-3758.85.BJR-2018-0280.R3.

Low-grade infections as a possible cause of arthrofibrosis after total knee arthroplasty

Purpose

Arthrofibrosis after total knee arthroplasty represents a considerable burden for the patient and a therapeutic challenge for the practitioner. One possible cause discussed in the literature is a low-grade infection. This hypothesis should be examined within the scope of this retrospective study.

Patients and methods

Nineteen patients with clinical symptoms of arthrofibrosis after primary total knee arthroplasty were examined between January, 1999 and January, 2012. Incorrect positioning was radiologically ruled out. All patients were examined clinically (score of Freeman as well as Blauth and Jäger), radiologically (component and leg alignment, patella height according to Insall and Salvati), microbiologically (culture-based procedures), molecular biologically (PCR) and histologically in the course of an open revision of the prosthesis.

Results

According to the score of Freeman et al. (1977), a highly significant improvement in pain (p = 0.007) and in the overall score (p = 0.003) was shown. The knee joint mobility did not change significantly (p = 0.795). PCR was negative in 17 patients. One patient showed a PCR-positive result of the synovial membrane for Corynebacterium spp., while Staphylococcus warneri was detected in the culture. Another patient had a positive result of synovia PCR for Enterococcus cecorum as well as Corynebacterium spp. However, this culture was sterile. In 16 patient samples, no bacterial growth was detectable. Two samples were not evaluable. The main histopathological findings were synovialitis and fibrosis.

Conclusion

The hypothesis of low-grade-infection-induced arthrofibrosis after total knee arthroplasty could not be confirmed in this study. However, based on this small study population the conclusion needs to be confirmed by new and larger studies, ideally prospectively designed including a control group.

Normal CRP and WBC values in total hip arthroplasty (THA) with signs of loosening. Do we need a joint aspiration?

PURPOSE

Overall Total hip arthroplasty (THA) is a very successful procedure. However, in case of complication dedicated management is required. Two major complications of THA failures are aseptic loosening (AL) and periprosthetic joint infection (PJI). The primary hypothesis of this study was that joint aspirations in patients with signs of loosening after THA are capable to detect PJI in suspected AL with negative serologic testing.

METHODS

In this study a total of 108 symptomatic patients with radiographic signs of prosthetic loosening and hip pain in THA were included. Based on a standardized algorithm all patients underwent serological testing followed by joint aspiration preoperatively. Intraoperatively harvested samples were subjected to microbiological testing and served as the gold standard in differential diagnosis. Demographics, as well as the results of serologic and microbiological testing were collected from the medical records.

RESULTS

Of the included patients 85 were finally diagnosed with an AL and 23 with PJI. Within the patients with PJI 13 (56%) patients demonstrated elevated CRP and WBC counts, as well as positive synovial cultures after joint aspiration. In ten patients (44%) diagnosed with PJI neither CRP nor WBC were abnormal.

CONCLUSION

The diagnosis of PJI can be difficult in THA with radiographic signs of loosening. Clinical features including pain, fever, and local sings of infection are uncommon especially a long period after index operation. First-line screening testing relies on serological evaluation of CRP and WBC. However, normal CRP and WBC values cannot rule out a PJI. These cases can be detected by joint aspiration and synovial cultures reliably.

Evaluation and Management of Septic Arthritis and its Mimics in the Emergency Department

Septic arthritis is a dangerous medical condition associated with significant morbidity and mortality. However, the differential diagnosis can be broad with conditions that mimic this disease and require different evaluation and treatment. This narrative review presents the emergency medicine evaluation and management, as well as important medical conditions that may mimic this disease. Septic arthritis commonly presents with monoarticular joint pain with erythema, warmth, swelling, and pain on palpation and movement. Fever is present in many patients, though most are low grade. Blood testing and imaging may assist with the diagnosis, but the gold standard is joint aspiration. Management includes intravenous antibiotics and orthopedic surgery consult for operative management vs. serial aspirations. Clinicians should consider mimics, such as abscess, avascular necrosis, cellulitis, crystal-induced arthropathies, Lyme disease, malignancy, osteomyelitis, reactive arthritis, rheumatoid arthritis, and transient synovitis. While monoarticular arthritis can be due to septic arthritis, other medical and surgical conditions present similarly and require different management. It is essential for the emergency clinician to be aware how to diagnose and treat these mimics.

The serum level of C-reactive protein alone cannot be used for the diagnosis of prosthetic joint infections, especially in those caused by organisms of low virulence

AIMS

The aim of this study was to determine the prevalence and characteristics of C-reactive protein (CRP)-negative prosthetic joint infection (PJI) and evaluate the influence of the type of infecting organism on the CRP level.

PATIENTS AND METHODS

A retrospective analysis of all PJIs affecting the hip or knee that were diagnosed in our institution between March 2013 and December 2016 was performed. A total of 215 patients were included. Their mean age was 71 years (sd 11) and there were 118 women (55%). The median serum CRP levels were calculated for various species of organism and for patients with acute postoperative, acute haematogenous, and chronic infections. These were compared using the Kruskal-Wallis test, adjusting for multiple comparisons with Dunn's test. The correlation between the number of positive cultures and serum CRP levels was estimated using Spearman correlation coefficient.

RESULTS

Preoperative CRP levels were normal (< 10 mg/l) in 77 patients (35.8%) with positive cultures. Low-virulent organisms were isolated in 66 PJIs (85.7%) with normal CRP levels. When grouping organisms by species, patients with an infection caused by Propionibacterium spp., coagulase-negative staphylococci (CNS), and Enterococcus faecalis had significantly lower median serum CRP levels (5.4 mg/l, 12.2 mg/l, and 23.7 mg/l, respectively), compared with those with infections caused by Staphylococcus aureus and Streptococcus spp. (194 mg/l and 89.3 mg/l, respectively; p < 0.001). Those with a chronic PJI had statistically lower median serum CRP levels (10.6 mg/l) than those with acute postoperative and acute haematogenous infections (83.7 mg/l and 149.4 mg/l, respectively; p < 0.001). There was a significant correlation between the number of positive cultures and serum CRP levels (Spearman correlation coefficient, 0.456; p < 0.001).

CONCLUSION

The CRP level alone is not accurate as a screening tool for PJI and may yield high false-negative rates, especially if the causative organism has low virulence. Aspiration of the joint should be used for the diagnosis of PJI in patients with a chronic painful arthroplasty, irrespective of CRP level. Cite this article: Bone Joint J 2018;100-B:1482-86.

Outcome of Irrigation and Debridement after Failed Two-Stage Reimplantation for Periprosthetic Joint Infection

Introduction

Two-stage revision is the gold standard for the treatment of deep implant infection after knee or hip arthroplasty. Irrigation and debridement may be a treatment option for failed 2-stage revisions in cases where a reinfection occurs within 30 days or the symptoms exist not longer than 3 weeks and is appealing because of its low morbidity. We determined the incidence of recurrent infections following irrigation and debridement for failed two-stage revision hip and knee arthroplasty.

Methods

We performed a single center retrospective review of periprosthetic hip and knee infections treated with a two-stage procedure from 2002 to 2010. All patients that subsequently underwent irrigation and debridement for a subsequent infection were selected for the current study.

Results

440 two-stage revisions were performed between 2002 and 2010. Fifty-one two-stage revisions failed (11.6%). Nineteen failed two-stage revisions were treated with irrigation and debridement; 12 (63.2%) patients remained free of infection at follow-up (mean follow-up: 39 months; range, 24-90 months), infection persisted in 6 patients (31.6%), and 1 patient died (5.3%).

Conclusions

Success rates of irrigation and debridement for failed two-stage procedures are similar to the success rates of irrigation and debridement in primary implant infections. According to the current paper, irrigation and debridement are an acceptable treatment for acute reinfections after failed two-stage revision if performed within the first 30 postoperative days after failed two-stage procedure or if symptoms are present for less than 3 weeks in the presence of a susceptible organism.

Infection safety of dexamethasone in total hip and total knee arthroplasty: a study of eighteen thousand, eight hundred and seventy two operations

PURPOSE

Dexamethasone has been shown to prevent post-operative nausea and vomiting (PONV) and seems to reduce post-operative pain. Both factors, which can extend the hospital stay, delay rehabilitation, and impact patient satisfaction. Because of the immunosuppressive and glucose-rising effects of dexamethasone, there has been concern of its safety in arthroplasty surgery. The purpose of our study was to examine infection safety of dexamethasone in arthroplasty surgery with enough large study material to reliably detect a possible, even small, difference in infection incidence.

METHODS

A total of 18,872 consecutive primary and revision hip and knee arthroplasties were analyzed with data gathered from clinical information databases and a surgical site infection surveillance database with prospective data collection. Also, emergency operations due to fractures were included except for hip hemiarthroplasties.

RESULTS

During the follow-up, 189 (1.0%) prosthetic joint infections (PJIs) occurred: 0.8% after primary arthroplasty and 1.9% after revision arthroplasty. Dexamethasone was used in 2922 (15.5%) operations. The PJI rate in the dexamethasone group was 1.1% (31/2922) and in the non-dexamethasone group 1.0% (161/15950), with no significant difference in the risk of PJI between the two groups (OR 1.052, 95% CI 0.715-1.548, P = 0.773).

CONCLUSIONS

In our study material, the use of a single 5-10 mg dose of dexamethasone did not increase the incidence of post-operative PJI. A low dose of dexamethasone may be safely used to prevent PONV and as part of multimodal analgesia on patients undergoing arthroplasty operation.

Results and Patient Reported Outcome Measures (PROMs) after One-Stage Revision for Periprosthetic Joint Infection of the Hip: A Single-centre Retrospective Study

Background: Little is known about functional outcome and quality of life (QoL) after one-stage revision for periprosthetic joint infection (PJI) of the hip. Methods: a cohort of 30 subjects treated with one-stage revision between 2011 and 2015 was identified, and questionnaires on functional outcome and QoL were distributed. Results: 28 subjects were successfully treated (93%). Most subjects were referred from other hospitals. Coagulase-negative Staphylococcus was found in 50% of the cases, and 40% of all cultured bacteria were multidrug-resistant. 25% had subsequent revision surgery, unrelated to PJI. Functional outcome was good and QoL scores were high, comparable to prosthetic joint revision surgery in general. Conclusion: Although the cohort was small and statistical analysis was not performed, this study showed that excellent results can be obtained with one-stage revision for hip PJI. Functional outcome and QoL was comparable to prosthetic joint revision surgery in general.

What Is the Optimal Criteria to Use for Detecting Periprosthetic Joint Infections Before Total Joint Arthroplasty?

BACKGROUND

The purposes of this study were to (1) test the accuracy of α-defensin and combined α-defensin-aspiration cultures in diagnosing periprosthetic joint infection (PJI) before revision total knee and hip arthroplasty and (2) evaluate Musculoskeletal Infection Society (MSIS) criteria and α-defensin as predictors of successful reimplantation (second-stage) at 1 year after surgery.

METHODS

We retrospectively evaluated a total of 97 synovial fluid aspirations performed between August 2014 and September 2016 before revision due to septic or aseptic failures (n = 70) or before second-stage (n = 27) joint arthroplasty. Revisions were categorized as either septic or aseptic according to the MSIS criteria. Synovial fluid was tested for α-defensin, cell count with differential, and cultures. Reimplantations were assessed for success or failure (defined as the need for reoperation due to infection) within 1 year after surgery.

RESULTS

For septic and aseptic revision arthroplasty, the sensitivity, specificity, positive predictive value, and negative predicted value of α-defensin was 97% while for the combined α-defensin and aspiration culture, it was 96%, 100%, 100%, and 97%. Despite being performed with negative MSIS criteria and α-defensin test results, 11% (3/27) of reimplantations (second-stage) failed within 1 year postoperatively because of infection.

CONCLUSION

Alpha-defensin is an accurate diagnostic test for the diagnosis of PJI before revision arthroplasty. The combination of α-defensin and aspiration cultures has higher specificity and positive predictive value. MSIS criteria and α-defensin may help predict the success of reimplantations within 1 year after surgery.

Diagnostic parameters in periprosthetic infections: the current state of the literature

Despite progress in recent years, a definitive diagnosis of PPI is not yet possible. Due to new diagnostic possibilities and the further development of already existing diagnostic tools, a more accurate diagnostic clarification of uncertain cases should be possible. The following article includes an overview of common existing diagnostic tools and instruments, which will likely gain importance in the future.

Successful treatment for acute prosthetic joint infection due to MRSA and Candida albicans: a case report and literature review

Methicillin-resistant Staphylococcus aureus (MRSA) and Candidal prosthetic joint infections (PJIs) are very rare, and the optimal management for these patients is still unknown. A 54-year-old man with traumatic arthritis due to previous electric injury successfully retained the implant despite the successive infection with MRSA and Candida albicans after total knee arthroplasty (TKA). Continuous lavage with vancomycin was used to control MRSA infection and repeated local washout plus oral swallow with voriconazole tablet were administered to eradicate C. albicans. Additional three reported cases were identified by the criteria of selecting patients with concomitant and/or successive MRSA and Candidal PJIs. Different methods were applied with variable outcomes. Therefore, several risk factors such as intra-articular corticosteroid injection, high frequency of door openings in the operating room, excessive blood loss and allogeneic red blood cell transfusions should be avoided. Debridement, antibiotics and implant retention (DAIR) can be an alternative in dedicated patients to control acute MRSA and Candidal PJIs. Particularly, repeated intra-articular washout with susceptible drugs and a prolonged duration of oral antibiotics was essential for microbial control.

Antibiotic sensitivities of coagulase-negative staphylococci and Staphylococcus aureus in hip and knee periprosthetic joint infections: does this differ if patients meet the International Consensus Meeting Criteria?

Introduction

Coagulase-negative staphylococci (CoNS) are the main pathogens responsible for prosthetic joint infections (PJIs). As normal inhabitants of human skin, it is often difficult to define if they are contaminants, or if they have an active role in initiating infection. This study aims to evaluate differences in CoNS organisms (Staphylococcus hominis, Staphylococcus capitis, Staphylococcus haemolyticus, Staphylococcus warneri) and Staphylococcus aureus in terms of isolation rate and antimicrobial susceptibility from patients who met the International Consensus Meeting (ICM) criteria for PJIs and those who did not.

Methods

Staphylococci isolates from January 2014 to December 2015 retrieved from patients undergoing revision joint arthroplasty were classified in accordance with criteria established by the ICM of Philadelphia.

Results

As per the consensus classification, 50 CoNS and 39 S. aureus infections were recognized as pathogens, while 16 CoNS and four S. aureus were considered as contaminants. Frequency of isolation of S. aureus was significantly higher in infected patients than in those without infection, while no significant differences were observed among CoNS. Resistance to levofloxacin, erythromycin, gentamicin trimethoprim/sulfamethoxazole, and rifampicin was significantly more frequent in S. haemolyticus than in the other species, as well as resistance to erythromycin and gentamicin in S. hominis. In comparison to S. aureus, CoNS were significantly more resistant to daptomycin and gentamicin and more susceptible to rifampicin.

Conclusion

CoNS, other than Staphylococcus epidermidis, are frequently isolated from PJIs, and their infective role and antimicrobial susceptibility need to be assessed on an individual patient basis. S. haemolyticus seems to emerge as responsible for PJI in a large volume of patients, and its role needs to be further investigated, also considering its pattern of resistance.

The unsuspected prosthetic joint infection

Aims

Positive cultures are not uncommon in cases of revision total knee and hip arthroplasty (TKA and THA) for presumed aseptic causes. The purpose of this study was to assess the incidence of positive intra-operative cultures in presumed aseptic revision of TKA and THA, and to determine whether the presence of intra-operative positive cultures results in inferior survival in such cases.

Patients and Methods

A retrospective cohort study was assembled with 679 patients undergoing revision knee (340 cases) or hip arthroplasty (339 cases) for presumed aseptic causes. For all patients three or more separate intra-operative cultures were obtained. Patients were diagnosed with a previously unsuspected prosthetic joint infection (PJI) if two or more cultures were positive with the same organism. Records were reviewed for demographic details, pre-operative laboratory results and culture results. The primary outcome measure was infection-free implant survival at two years.

Results

The incidence of unsuspected PJI was 27 out of 340 (7.9%) in TKA and 41 out of 339 (12.1%) in THA. Following revision TKA, the rate of infection-free implant survival in patients with an unsuspected PJI was 88% (95% confidence intervals (CI) 60 to 97) at two years compared with 98% (95% CI 94 to 99) in patients without PJI (p = 0.001). After THA, the rate of survival was similar in those with unsuspected PJI (92% (95% CI 73 to 98) at two years) and those without (94% (95% CI 89 to 97), p = 0.31).

Conclusion

Following revision of TKA and THA for aseptic diagnoses, around 10% of cases were found to have positive cultures. In the knee, such cases had inferior infection-free survival at two years compared with those with negative cultures; there was no difference between the groups following THA. Cite this article: Bone Joint J 2017;99-B:1482–9.

α-Defensin point-of-care test for diagnosis of prosthetic joint infections: neglected role of laboratory and clinical pathologists

Periprosthetic joint infection (PJI) is a serious complication that may occur after native joint replacement leading to a severe health and economic burden. Currently, due to several confounding factors, PJI is difficult to diagnose. Today, a multidisciplinary approach is indispensable to correctly define a periprosthetic joint infection; indeed, tissue histology, microbiology cultures and clinical findings are used together to achieve this goal. Analysis of α-defensin is commonly used for PJI diagnosis, as it allows the rapid detection of α-defensin present in the synovial fluid following a microbial infection. Currently, a point-of-care testing (POCT) assay able to detect the presence of human α-defensins 1–3 in synovial fluid of patients is aimed directly at orthopedic surgeons. However, many orthopedic surgeons lack experience and training in quality laboratory practices, often failing to appreciate the significance of quality control and proper documentation when using POCT assays. To guarantee the highest quality diagnostic services, the α-defensin test should be used together with other biochemical and microbiological criteria commonly used for PJI diagnosis. Additionally, the close cooperation and communication between laboratory, pathologists and physicians is of fundamental importance in the correct diagnosis of PJI.

Concordance between the old and new diagnostic criteria for periprosthetic joint infection

PURPOSE

There is no uniform definition for periprosthetic joint infection (PJI). New diagnostic criteria were formulated in an international consensus meeting in 2013 and adopted by Centers for Disease Control (CDC) in 2016. The purpose of this study is to compare the new diagnostic criteria with the old CDC criteria from the year 1992.

METHODS

Patients, who had been treated for PJI of hip or knee from 2002 to 2014, in a tertiary care hospital, were identified. Patient records were reviewed by a physician to identify PJI cases fulfilling the old or new CDC criteria and to record data concerning the diagnostic criteria. PJI frequencies were calculated for the two diagnostic criteria sets. Cross tables were formed to compare the concordance between the two sets of criteria in the whole material and in different clinical subgroups.

RESULTS

Overall 405 cases fulfilling either or both sets of criteria for PJI were identified. 73 (18%) of the patients fulfilled only the old criteria, whereas only one (0.2%) fulfilled only the new criteria. Of the patients who did not fulfil the new criteria, in 39 (53%) the diagnosis was based solely on the clinician's opinion.

CONCLUSIONS

The number of PJIs is notably lower when using the new, more objective, diagnostic criteria. A large portion of the cases diagnosed as infection by the treating clinician, did not fulfil the new diagnostic criteria.

Management of periprosthetic infections

Periprosthetic joint infection (PJI) is considered one of the most challenging complications compromising patient health and is considered an economic burden. Despite all strategies PJI prevalence is between 1%-2%. Considerable efforts have been investigated in the past decade to diminish or erradicate PJI prevalence. This article manages the definition of PJI and the new major and minor criteria from Parvizi et al Then a scientific analysis of every minor and major criteria. Multidisciplinary management is reccommended according to guidelines. A numerous of surgical options exist each and everyone with its indications, contraindications and specific antibiotic therapy regimen. Surgical options are: (1) irrigation and cleaning with retention of the prosthesis with a success rate 0%-89%; (2) single-stage revision surgery with a succes rate of > 80%; and (3) two-stage revision surgery (authors preferred method) with a succes rate of 87%. Radical treatment options like arthrodesis and amputation are reserved for specific group of patients, with a succes rate varying from 60%-100%. The future of PJI is focused on improving the diagnostic tools and to combat biofilm. The cornerstone of management consists in a rapid diagnosis and specific therapy. This article presents the most current diagnostic and treatment criteria as well as the different surgical treatment options depending on the type of infection, bacterial virulence and patient comorbidities.

[Periprosthetic infections in patients with rheumatism : A challenge]

The increasing number of implantations will lead to more periprosthetic infections. Periprosthetic infections in patients with rheumatism, who are often undergoing immunosuppressive treatment, represent a challenge for the treating physicians. The optimal care and treatment therefore necessitate an interdisciplinary agreement between orthopedic surgeons, specialists for infections and rheumatologists.

Prevention of periprosthetic joint infection: new guidelines

The World Health Organization (WHO) and the Centre for Disease Control and Prevention (CDC) recently published guidelines for the prevention of surgical site infection. The WHO guidelines, if implemented worldwide, could have an immense impact on our practices and those of the CDC have implications for healthcare policy in the United States. Our aim was to review the strategies for prevention of periprosthetic joint infection in light of these and other recent guidelines. Cite this article: Bone Joint J 2017;99-B(4 Supple B):3-10.

CD15 focus score: Infection diagnosis and stratification into low-virulence and high-virulence microbial pathogens in periprosthetic joint infection

INTRODUCTION

The aim of the work was to validate the CD15 focus score for the infection pathology of periprosthetic joint infection in a large group and to clarify whether a stratification into low-virulence and high-virulence microbial pathogens is possible by means of the CD15 focus score (quantification of CD15 positive granulocytes).

METHODS

The histopathology of 275 synovial tissue samples taken intraoperatively during revision operations (n=127 hip, n=141 knee, n=2 shoulder, n=5 ankle) was evaluated according to the SLIM consensus classification (SLIM=synovial-like interface membrane). Neutrophilic granulocytes (NG) were quantified by the CD15 focus score on the basis of the principle of focal maximum infiltration (focus) with evaluation of one field of vision (about 0.3mm²). The quantification values were compared with the microbiological diagnoses taking into consideration the virulence groups of low-virulence and high-virulence microbial pathogens and mixed infection.

RESULTS

The patients with positive microbiological findings (n=160) had significantly (p<0.001, Mann-Whitney U test) higher CD15 focus score values than patients with negative microbiological findings (n=115), the cut-off value being 39 cells per high power field (HPF). The CD15 focus score values of low-virulence microbial pathogens (n=94) were significantly lower (p<0.001, Mann-Whitney U test) than the values of high-virulence microbial pathogens (n=55), the cut-off value being 106 cells per HPF. Based on the microbiological diagnosis the sensitivity with respect to a microbial infection is 0.91, the specificity 0.92 (PPV=0.94; NPV=0.88; accuracy: 0.92; AUC=0.95). Based on the differentiation of the CD15 focus score values between low-virulence and high-virulence microbes the sensitivity is 0.70 and the specificity 0.77 (PPV=0.63; NPV=0.81; accuracy=0.74; AUC=0.74).

CONCLUSION

As a result of the high sensitivity and specificity, the easy to use CD15 focus score is a diagnostically valid score for microbial periprosthetic infection. A differentiation between low-virulence and high-virulence microorganism of sufficiently high diagnostic quality is additionally possible as a result of the defined quantification of CD15 positive granulocytes (the CD15 focus score) histopathological diagnosis of microbial infections is possible, which on the one hand supports the microbiological diagnosis and on the other hand by the stratification into low-virulence and high-virulence microbial pathogens could represent an additional basis for a pathogen-specific antibiotic treatment in the event of unclear constellations of findings.

Higher reliability of triple-phase bone scintigraphy in cementless total hip arthroplasty compared to cementless bipolar hemiarthroplasty

Purpose

Periprosthetic infection is one of the main reasons for revision surgery after hip arthroplasty. The purpose of the present study is to compare the reliability of triple-phase bone scintigraphy (TPBS) in the diagnosis of periprosthetic infection between cementless total hip arthroplasty (THA) and bipolar hemiarthroplasty (BHA).

Methods

In this retrospective study, 52 patients were analyzed; 33 of them were performed with THA and 19 of them were performed with BHA. The exclusion criteria were cementation in previous surgery, romatological joint disorders, periprosthetic fracture and malignancy history. C reactive protein (CRP) and erythrocyte sedimentation (ESR) rate results were recorded preoperatively. Tissue samples from the different areas periprosthetic tissue were obtained for histopathological examination and sample tissue culture.

Results

In the present study, the sensitivity, specificity and accuracy were 90.9%, 77.3% and 81.8%, respectively, for THA and 77.8%, 60.0% and 68.4%, respectively, for BHA. Positive predictive values for THA and BHA were 66.7% and 63.6%, and negative predictive values were 94.4% and 75.0%, respectively.

Conclusions

Due to the higher sensitivity, specificity and accuracy, TPBS has a more reliable diagnostic value for cementless THA in the diagnosis of periprosthetic infection compared to cementless BHA.

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Triple-phase bone scintigraphy is effective in ruling out infection with its higher sensitivity.

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Triple-phase bone scintigraphy has relatively low specificity compared to its high sensitivity.

Periprosthetic Joint Infection After Hip and Knee Arthroplasty: A Review for Emergency Care Providers

Periprosthetic joint infection is among the most common modes of failure of a total hip or knee arthroplasty and can be a common concern when patients present to the emergency department for care. The initial evaluation for periprosthetic joint infection includes a history and physical examination, followed by radiographs (to rule out other causes of pain or failure) and then serum erythrocyte sedimentation rate and C-reactive protein testing. If the erythrocyte sedimentation rate and C-reactive protein level are elevated or if the clinical suspicion for infection is high, the joint should be aspirated and the fluid sent for culture, as well as for a synovial WBC count and differential, with optimal threshold values of 3,000 WBC/μL and 80% polymorphonuclear cells, respectively. Recent work has shown that optimal cutoff values for patients presenting in the early postoperative period (within the first 6 weeks postoperatively) are different, with a C-reactive protein level greater than or near 100 mg/L (normal <10 mg/L), indicating the need for aspiration, with synovial fluid WBC thresholds of 10,000 WBC/μL and 90% polymorphonuclear cells. Antibiotics should not be administered before joint aspiration unless the patient has systemic signs of sepsis because even a single dose may cloud the interpretation of subsequent tests, including cultures taken from the joint. Furthermore, superficial cultures taken from wound drainage are discouraged because they can similarly cloud diagnosis and treatment. The rising prevalence of total joint arthroplasty makes proficiency in the assessment and early management of periprosthetic joint infection important for the emergency physician to optimize clinical outcomes.

[Histopathological diagnostic work-up of joint endoprosthesis-associated pathologies]

Increasing classes of joint implants and the combination of materials results in increased and wear-associated pathologies. According to the revised consensus classification, the following types can be recognized at conventional histological examination: Type I, particle-induced type; Type II, infection type; Type III, combination type; Type IV, indifferent type; Type V arthrofibrotic type; Type VI, allergic/immunological/toxic adverse reactions and Type VII, bone pathologies. Wear particles are histopathologically characterized according to the Krenn particle algorithm which focuses on a descriptive identification of wear particles and the differentiation of other nonwear-related particles. Type VII is considered histologically when there is evidence of a perivascular/interstitial lymphocytic CD20- and CD3-positive infiltrate, presence of mast cells and eosinophils, and tissue necrosis/infarction associated with implant wear material. Since wear particle-induced toxicity cannot be differentiated with certainty from hypersensitivity/allergic reaction on histological examination, immunological-allergological and clinical data should be used as supplementary criteria for the differential diagnosis. Tissue sampling should be performed from periprosthetic soft tissue with location mapping and when feasible also from bone tissue. Additional information regarding the type of implant and clinical, radiological, immunological, and microbiology data should be available to the pathologist. Further immunohistochemical studies are recommended in the following settings: infection (CD15, CD20, CD68); prosthesis-associated arthrofibrosis (β‑catenin); allergic/immunologic/toxic adverse reactions (CD20, CD3, CD4, CD8, CD117 and for T‑cell characterization T‑bet, GATA-3, and FOXP3).

The management of an infected total knee arthroplasty

Periprosthetic joint infection (PJI) is one of the most feared and challenging complications following total knee arthroplasty. We provide a detailed description of our current understanding regarding the management of PJI of the knee, including diagnostic aids, pre-operative planning, surgical treatment, and outcome.

May osteoarticular infections be influenced by vitamin D status? An observational study on selected patients

Background

Vitamin D deficiency has been associated with a high number of health outcomes, and its role on the immune system has been deeply investigated in recent years, although poor data are still available on vitamin D status in orthopedic infections including those of prosthetic implants.

Methods

We focused on preoperative values of 25(OH)D in selected groups of patients with septic (Group A) or aseptic (Group B) prosthetic loosening, infective bone disease such as septic arthritis and osteomyelitis (Group C) and other orthopedic pathologies (Group D) to evaluate differences in the vitamin D status.

Results

A high prevalence of vitamin D deficiency was recorded among the study population (16.5 ± 5.4 ng/mL, mean ± SD). Interestingly, all patients with an infection presented a higher 25(OH)D concentration (17.7 ± 5.3 ng/mL) in respect to uninfected ones (15.1 ± 5.6 ng/mL). Significantly higher levels of 25(OH)D were observed in patients with prosthetic joint infection (18.5 ± 6.5 ng/mL), when compared with those presenting an aseptic loosening (13.6 ± 9.4 ng/mL).

Conclusions

Deficiency in vitamin D levels have been found in orthopaedic patients. Prosthetic joint infections seems to be associated to higher values of vitamin D in respect to other bone infections or to other orthopaedic conditions requiring surgery.

More studies are needed to improve the knowledge on vitamin D status in these patients and to better clarify the role of vitamin D in relation to osteoarticular infections.