Preoperative Diagnosis of Periprosthetic Joint Infection: Role of Aspiration

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty: 2023 Update

Total knee arthroplasty is the most commonly performed joint replacement procedure in the United States. This manuscript will discuss the recommended imaging modalities for six clinical variants; 1. follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging, 2. Suspected infection after total knee arthroplasty. Additional imaging following radiographs, 3. Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs, 4. Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs, 5. Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs, and 6. Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy. Additional imaging following radiographs. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Molecular Imaging of Infections: Emerging Techniques for Pathogen-Specific Diagnosis and Guided Therapy

Evaluation of patients that may be infected is challenging. Imaging to identify or localize a site of infection is often limited because of the nonspecific nature of the findings on conventional imaging modalities. Available imaging methods lack the ability to determine if antibiotics are reaching the site of infection and are not optimized to follow response to therapy. Positron emission tomography (PET) is a method by which radiolabeled molecules can be used to detect metabolic perturbations or levels of expression of specific targets. The most common PET agent is the glucose analog 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG). 18F-FDG has some applicability to localizing a site of infection, but its lack of specificity limits its usefulness. There is a need for the development of pathogen-specific PET radiotracers to address the imaging shortcomings noted above. Preclinical and clinical progress has been made, but significant challenges remain.

Low Risk of Acute Iatrogenic Periprosthetic Joint Infection After Prosthetic Joint Aspiration

BACKGROUND

Synovial fluid analysis is an essential tool in diagnosing periprosthetic joint infection (PJI) after total knee arthroplasty (TKA). However, concern exists that aspiration may introduce infection into a noninfected joint. Therefore, the purpose of this study was to evaluate the incidence of iatrogenic PJI following diagnostic knee aspiration done within 6 months of the primary TKA.

METHODS

Between 2017 and 2021, the senior surgeon performed over 4,000 primary TKAs and aspirated 155 knees in 137 patients for whom there was a suspicion for PJI within 6 months of their primary TKA. There were 22 knees diagnosed as infected from the initial aspiration and therefore were excluded from the study. The remaining 133 aspirates in 115 patients who were negative for infection were followed for 6 months for signs and symptoms of PJI to elucidate whether aspiration introduced infection into an initially noninfected joint.

RESULTS

There were 70 of 133 knees (52.6%) aspirated between 0 and 6 weeks after index TKA, 40 of 133 (30.1%) between 6 weeks and 3 months, and 23 of 133 (17.3%) between 3 and 6 months. At final follow-up, none of the 133 initially noninfected knees exhibited evidence of subsequent iatrogenic PJI or had subsequent surgery for infection.

CONCLUSION

While joint aspiration is a procedure with inherent risks, this study shows that the rate of iatrogenic PJI is extremely low (0%). Therefore, if infection is suspected, the surgeon should consider joint aspiration, even in the initial postoperative period, as the risk for introducing infection is far outweighed by the risk of missing an infection.

HGT: A Hierarchical GCN-Based Transformer for Multimodal Periprosthetic Joint Infection Diagnosis Using Computed Tomography Images and Text

Prosthetic joint infection (PJI) is a prevalent and severe complication characterized by high diagnostic challenges. Currently, a unified diagnostic standard incorporating both computed tomography (CT) images and numerical text data for PJI remains unestablished, owing to the substantial noise in CT images and the disparity in data volume between CT images and text data. This study introduces a diagnostic method, HGT, based on deep learning and multimodal techniques. It effectively merges features from CT scan images and patients' numerical text data via a Unidirectional Selective Attention (USA) mechanism and a graph convolutional network (GCN)-based Feature Fusion network. We evaluated the proposed method on a custom-built multimodal PJI dataset, assessing its performance through ablation experiments and interpretability evaluations. Our method achieved an accuracy (ACC) of 91.4% and an area under the curve (AUC) of 95.9%, outperforming recent multimodal approaches by 2.9% in ACC and 2.2% in AUC, with a parameter count of only 68 M. Notably, the interpretability results highlighted our model's strong focus and localization capabilities at lesion sites. This proposed method could provide clinicians with additional diagnostic tools to enhance accuracy and efficiency in clinical practice.

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.

Likelihood of hip infection with image-guided hip aspiration dry tap: a 10-year retrospective study

OBJECTIVE

To determine the rate of infection in patients with suspected hip septic arthritis who underwent image-guided aspiration (IHA) resulting in dry-tap, diagnostic value of subsequent lavage and re-aspiration, and if pre-aspiration MRI can help prevent a dry tap.

MATERIALS AND METHODS

Retrospective review between 2010 to 2020 identified native hip (NH) and total hip arthroplasty (THA) patients who had a dry-tap following aspiration for suspected infection or periprosthetic joint infection (PJI). Serology tests, lavage/re-aspiration volumes, and aspirate cell-count/culture were assessed. On pre-aspiration MRI, presence/grade of joint effusion (JE), pseudocapsule dehiscence (PD), extraarticular fluid and sinus-tract were recorded.

RESULTS

Out of 215 included dry-taps, 185 (86.0%) were non-infected and 30 (13.9%) infected. In subgroup analysis, 64/71(90.1%) NH and 121/144(84.0%) THA dry-taps were non-infected. Pre-aspiration MRI of THA group with dry-tap showed significant findings; PD with extraarticular fluid (8/12, 66.7%) and sinus tract (7/12, 58.3%) were higher in the infected compared to non-infected group (5/42, 11.9% and 0/42, 0.0%) (both p < 0.001). Among THA group, polymorphonuclear-leukocytes > 80% was present in 8/9 (88.9%) of infected versus 4/28 (14.3%) non-infected group (p < 0.001). Multivariable regression showed PD (p = 0.005) and JE (p = 0.042) being significant independent predictors of PJI, similarly the elevated CRP (p = 0.044) and JE (p = 0.017).

CONCLUSION

Majority of patients suspected of hip joint infection with dry-tap were non-infected. Synovial PMN% following lavage maintains high sensitivity for detection of PJI. In patients with THA, PD and subsequent extraarticular collection can be associated with dry-tap therefore, pre-aspiration MRI can help determine their presence and plan the aspiration.

The alpha defensin lateral flow test is effective in predicting eradication of periprosthetic joint infection after surgical debridement

The primary aim of this study was to assess the utility of the alpha defensin lateral flow (ADLF) test for predicting the eradication of PJI after surgical debridement. The secondary aim was to describe the reliability of ADLF test in diagnosis of PJI intra- operatively. A prospective observational study was conducted in three independent orthopaedic centres. Twenty-two patients undergoing revision surgery (debridement, antibiotics and implant retention (DAIR), single or two-stage revision) for PJI were recruited, 13 female and 9 male with an average age of 64 years. Samples were collected intra-operatively at the start of the first surgical procedure and then at the completion of debridement or prior to reimplantation depending on the operation performed. These samples were tested using ADLF and then sent for microbiological analysis. The ADLF result was then compared to the corresponding culture result in order to determine the diagnostic predictive accuracy. The reliability of ADLF test to predict eradication of infection after debridement of PJI was excellent for specificity and positive predictive value (PPV) of which both where 100%, but had a poor sensitivity (14.3%) and negative predictive value (NPV) (62.5%). The reliability of ADLF test to predict PJI was poor with only a 50% sensitivity and specificity. The ADLF test has a high specificity and PPV for diagnosing eradication of infection after debridement. In contrast the ADLF testing appears to have poor diagnostic accuracy for PJI when used on intra-operative samples, prior to surgical intervention. No benefits or funds were received in suppo

Diagnostic value of fluoroscopy-guided hip aspiration for periprosthetic joint infection

PURPOSE

To assess the value of preoperative joint aspiration in detecting periprosthetic joint infection (PJI) in patients undergoing revision hip arthroplasty and to compare these with the clinical findings, serum markers, and intraoperative findings.

MATERIALS AND METHODS

Fluoroscopically guided hip aspirations in patients with pain after hip arthroplasty were retrospectively reviewed from January 2014 to December 2018. All hips underwent subsequent revision hip arthroplasty. Antibiotics were discontinued at least 2 weeks before the aspiration. The 2018 Musculoskeletal Infection Society (MSIS) criteria served as a standard of reference for PJI. Clinical, serum, synovial, and intraoperative parameters were recorded in all patients. Correlations between all parameters with PJI diagnosis were analyzed using linear and logistic regression models with ROC analysis.

RESULTS

In 202 hips that included 91 septic hips, hip aspiration (AUC = 0.78) and intraoperative (0.80) parameters performed better than serum-based tests (0.64) and clinical parameters (0.68) in detecting PJI. Using MSIS criteria as a standard of reference, hip aspiration had a sensitivity of 64.0% and an accuracy of 78.5% for cultures and a sensitivity of 74.2% and an accuracy of 82.1% for synovial polymorphonuclear neutrophils% (PMN%). Results substantially improved sensitivity after excluding patients that were treated with antibiotics, particularly culture results.

CONCLUSIONS

Preoperative hip aspiration showed good diagnostic performance in diagnosing PJI compared with MSIS criteria as a standard of reference. But a negative result from aspirate could not rule out PJI. Based on our findings, hip aspiration is an essential test for treatment planning in patients with pain after hip arthroplasty.

Diagnostic value of routine pre-operative investigations used in combination in the diagnosis of periprosthetic joint infection

The primary aim of this study was to assess the diagnostic accuracy of joint aspiration culture, serum C-reactive protein (CRP) and serum erythrocyte sedimentation rate (ESR), individually, and in combination for the diagnosis of periprosthetic joint infection (PJI). A consecutive patient series with pre-operative inflammatory marker levels, an aspiration culture of either hip or knee arthroplasty and intra-operative culture samples from subsequent revision surgery was compiled. This retrospective patient cohort analysis included 128 aspiration. The data were analysed to compare pre-operative aspiration cultures, serum ESR and CRP levels to the chosen gold standard for PJI diagnosis of intra-operative culture samples. A diagnostic algorithm was created using the above tests combined with clinical suspicion index. The values that had the highest sensitivity and specificity of predicting PJI were >5 for CRP and >16 for ESR. CRP used individually had the highest sensitivity and negative predictive value (NPV) of any test (75.0% and 75.9%, respectively). ESR + aspirate had the highest specificity and positive predictive value (PPV), of 100% for both. Using all three tests together the specificity and PPV were higher than the test individual values (95.3% and 85.0% respectively). Based on subgroup analyses the combination of ESR or CRP plus joint aspiration has superior PPV compared to individual tests. ESR and CRP had the highest NPV when used in isolation. An algorithm has been developed to guide clinical diagnosis.

Novel Biomarkers for Diagnosing Periprosthetic Joint Infection from Synovial Fluid and Serum

Background:

Synovial fluid bacterial culture is the cornerstone of confirmation or exclusion of periprosthetic joint infection (PJI). The aim of this study was to assess synovial fluid and serum biomarker patterns of patients with total joint arthroplasty (TJA), and the association of these patterns with PJI.

Methods:

Synovial fluid and serum samples were collected from 35 patients who were admitted to the Arthroplasty Unit of the Department of Orthopaedics and Traumatology at Turku University Hospital. Of the 25 patients who were included in the study, 10 healthy patients with an elective TJA for osteoarthritis served as the control group, and 15 patients who were admitted due to clinical suspicion of PJI with local redness, swelling, wound drainage, pain, and/or fever and who had a positive synovial fluid bacterial culture served as the study group. Logistic regression was used to assess the ability of 37 biomarkers (including cytokines, chemokines, and growth factors) with commercially available tests to detect PJIs.

Results:

In synovial fluid, the concentrations of sTNF-R1 and sTNF-R2 (soluble tumor necrosis factor receptors 1 and 2) and BAFF (B-cell activating factor, also known as TNFSF13B) were significantly higher in the PJI group (p < 0.002). In serum, the sTNF-R1 concentration was significantly higher in the PJI group, whereas the TWEAK (tumor necrosis factor-like weak inducer of apoptosis) and osteocalcin concentrations were significantly lower (p < 0.002). The sensitivity for detecting PJI using synovial fluid was 1.00 for sTNF-R2, 0.93 for sTNF-R1, and 0.87 for BAFF/TNFSF13B. The specificity of all 3 synovial markers was 1.00. The sensitivity using serum was 0.80 for TWEAK, 0.73 for sTNF-R1, and 0.80 for osteocalcin. The specificity of all 3 serum markers was 1.00.

Conclusions:

Synovial sTNF-R2 is a promising new biomarker for detecting PJI. We are not aware of any previous reports of the use of sTNF-R2 in PJI diagnosis. More research is needed to assess the clinical importance of our findings.

Level of Evidence:

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

A rare case of inflammation after total hip arthroplasty due to a malpositioned prosthesis: A case report

RATIONALE

Although prosthetic loosening caused by poor prosthesis positioning is common after total hip arthroplasty (THA), an inflammation caused by poor prosthesis positioning is rare. We report a case in which a THA-related inflammation was indeed caused by poor prosthesis positioning.

PATIENT CONCERNS

A 64-year-old woman was admitted to our hospital with a history of persistent hip pain that had started after she had undergone THA 4 years previously. In addition, she complained of swelling of the hip that had begun 2 months ago.

DIAGNOSIS

Her pain and swelling was initially thought to be caused by an infection, but was eventually diagnosed as inflammation caused by prosthesis loosening, that was in line with finding that her preoperative and intraoperative cultures showed no bacterial or fungal growth. This case posed many questions and difficulties during the diagnostic and treatment stages.

INTERVENTIONS

Routine diagnosis of periprosthetic suspected infection includes blood test, erythrocyte sedimentation rate, C-reactive protein level, bacterial and fungal cultures, and pathology examinations, which were performed. Finally, this case was eventually diagnosed as inflammation, the prosthesis was removed and antibiotics administered. It was replaced 6 months later.

OUTCOMES

Except for the erythrocyte sedimentation rate and C-reactive protein levels, X rays, routine blood tests, bacterial and fungal cultures (3 times), and other tests were within the normal range. Positive pathological examinations of synovium during and after the operation indicated chronic inflammation and eliminated inflammation in other areas. Postoperative effect of the second-stage THA was good, with the patient highly satisfied after 6 months.

LESSONS

The operative method and position of a joint prosthesis are extremely important. A poorly positioned prosthesis worsens with wear. Wear particles then lead to long-term localized aseptic inflammation with swelling and fever and eventually to low-virulence infection. Prosthetic loosening may be found even at long-term follow-up evaluations after THA in patients with a poorly positioned prosthesis, eventually leading to the need for revision. We had 2 questions: should early revision be considered when a prosthesis had not been properly positioned? In the absence of any confirmation of infection, should a patient suspected of having a periprosthetic infection be treated as early as possible?

The Importance Of Multi-site Intra-operative Tissue Sampling In The Diagnosis Of Hip And Knee Periprosthetic Joint Infection - Results From A Single Centre Study

Introduction: The primary aim of this study was to determine whether the tissue type and anatomical location of intra-operative samples influences the accuracy of culture in the diagnosis of periprosthetic joint infection (PJI). The secondary aim was to create a predictive model of PJI using other known patient variables.

Methods: A retrospective cohort of 3460 intra-operative samples from 887 patients was identified. The data was then analysed to compare intra-operative culture results (positive or negative) to the chosen gold standard of clinical diagnosis made by the treating team (infected or non-infected prosthetic joint). The intra-operative samples were grouped according to their labelling at the time of collection.

Results: No single tissue type or anatomical location had both high sensitivity and specificity. The highest specificity for an anatomical location was hip bursa with 100%, for tissue type it was synovium with 93%. Sensitivity was highest in the anatomical locations for hip capsule (68%) and in the tissue types for pus (83%). Data analysis was performed to create a model for PJI and identified pre-operative predictors of PJI (increased white cell count, knee joint and non-revision surgery) which when used in combination with intra-operative culture results increased the sensitivity.

Conclusion: Sample type and anatomical location influenced the reliability of the diagnosis of PJI however, no single sample type had higher diagnostic accuracy than samples combined thereby highlighting the necessity of obtaining multiple intra-operative samples in the diagnosis of PJI. The variation in predictive values of tissue types as well as improvement in sensitivity when combined with patient factors indicates that types of intra-operative sampling and the overall diagnostic pathway should vary depending on the individual case.

PROTOCOL FOR TREATING ACUTE INFECTIONS IN CASES OF TOTAL KNEE ARTHROPLASTY

Objective:

To retrospectively evaluate the results after applying a protocol for treating acute infections in cases of total knee arthroplasty and to establish factors predictive of success or failure.

Methods:

Thirty-two patients who were diagnosed with acute infection of the knee following total arthroplasty between 2004 and 2009 were retrospectively evaluated. Infections following arthroplasty were treated in accordance with the protocol for acute infections following arthroscopy recommended at our institution.

Results:

With application of a treatment protocol for acute infections following total knee arthroplasty, 26 patients (81.2%) had good results and 6 (18.8%) had unsatisfactory results. Statistical analysis showed that the variables correlated with a worse prognosis were age (p = 0.038) and number of surgical debridement procedures performed (p = 0.038).

Conclusion:

Our treatment routine was effective for infection. Prosthesis revision was performed in 2 cases when the initial surgical debridement failed to control the infection. Nível de Evidência IV, Série de casos.

Usefulness of Culturing the Periprosthetic Membrane or Neosynovium for the Diagnosis of Infection During Hip and Knee Revision Arthroplasty

INTRODUCTION

Identification of microorganisms is critical for correct management of an infected arthroplasty. Our hypothesis is that the culture yield depends on the location around the prosthesis from which samples are obtained.

METHODS

This prospective study included 298 revisions of the hip (123) and knee (175). We compared the yield of the intraoperative samples obtained, which included synovial fluid (two), neosynovium (two), and periprosthetic membrane (two).

RESULTS

Cultures were positive in 28 cases, in which 15 had the same diagnosis considering either the neosynovium or the membrane, and there were 3 cases in which the infection could have been diagnosed only by considering the combination of both. In all, there were 8 cases in which the infection might have been misdiagnosed unless considering a combination of both solid tissue samples (P = 0.004).

CONCLUSIONS

The yields of the periprosthetic membrane and neosynovium do not differ significantly, and we recommend considering a combination of both.

LEVEL OF EVIDENCE

Diagnostic Level II.

Diagnosing periprosthetic hip joint low-grade infection via arthroscopic neo synovium biopsies

BACKGROUND

There is currently a lack of consensus regarding the most effective diagnostic algorithm for cases of supposed low-grade infection after total hip arthoplasty (THA).

OBJECTIVE

The aim of this study was to assess reliability in the use of biopsies, obtained by hip arthroscopy, to detect a periprosthetic hip joint infection (PJI).

METHODS

From 2012 to 2016, diagnostic arthroscopy of the hip joint was performed in 20 patients with a supposed PJI following THA. In 10 of these patients, the THA was revised for various reasons after diagnostic arthroscopy. The microbiological and histological findings of the biopsies obtained by arthroscopy were compared to findings from intraoperative samples of the revision arthroplasty.

RESULTS

For arthroscopic biopsies, we detected a sensitivity of 1.00 (95% confidence interval [CI] 0.40-1.00), a specificity of 0.83 (95% CI 0.36-1.00), a positive predictive value of 0.80 (95% CI 0.28-1.00), and a negative predictive value of 1.00 (95% CI 0.48-1.00). The accuracy was 0.90.

CONCLUSIONS

The analysis of arthroscopic biopsies represents a helpful tool to verify or rule out a PJI in selected patients. Nevertheless, minimally invasive diagnostic tools (e.g., laboratory analysis and aspiration) should be utilized beforehand.

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.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty

Total knee arthroplasty (TKA) is the most commonly performed joint replacement procedure in the United States and annual demand for primary TKA is expected to grow by 673% by 2030. The first part provides an overview of imaging modalities (radiographs, CT, MRI, ultrasound, and various nuclear medicine studies) and discusses their usefulness in the imaging evaluation of TKA. The second part focuses on evidence-based imaging and imaging-guided intervention algorithms for the workup of TKA and its complications, including routine follow-up, component wear, periprosthetic infection, aseptic loosening, granulomas/osteolysis, conventional and rotational instability, periprosthetic fracture, patellar complications, and a variety of periprosthetic soft tissue abnormalities. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Proinflammatory biomarkers' level and functional genetic polymorphisms in periprosthetic joint infection

OBJECTIVE

The aims of this study were 1) to identify the level of inflammatory biomarkers interleukin (IL)-1α, IL-1β, IL-6, IL-8, IL-17, C-reactive protein (CRP), granulocyte colony-stimulating factor (GCSF), ferritin, and tumor necrosis factor (TNF)-α in serum and synovial fluid samples of patients who underwent revision arthroplasty surgery; 2) to establish the relationship between serum and synovial fluid levels; 3) to determine if any of the 11 genetic polymorphisms of TNFα, IL-1, IL-6, IL-8, IL-17, and GCSF on the encoding genes was associated with periprosthetic joint infection (PJI).

METHODS

Synovial fluid and serum was collected from 88 patients who underwent revision arthroplasty surgery. The Musculoskeletal Infection Society definition was used to classify these patients into 2 groups: 36 PJIs and 52 aseptic failures. Synovial fluid and serum samples were tested for 9 biomarkers using a micro enzyme-linked immunosorbent assay. Genetic polymorphisms were evaluated with polymerase chain reaction and restriction endonuclease analysis.

RESULTS

Synovial fluid-derived IL-1α, IL-1β, IL-8, IL-17, CRP, GCSF, TNFα, and serum-derived IL-6, IL-17, ferritin, CRP were found suitable to classify PJI and aseptic failure. In addition, IL-17 and CRP levels demonstrated a positive correlation between synovial fluid and serum. TNFα-238, IL6-174, GCSF3R, and IL1 RN-VNTR genetic polymorphisms occurred more frequently in individuals with septic failure.

CONCLUSION

Significant differences between the two groups were observed in the functional polymorphisms of the genes encoding the cytokines investigated. These differences could be interpreted as indicating that there is an association between PJI and genetic polymorphisms.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Tertiary care centre adherence to unified guidelines for management of periprosthetic joint infections: a gap analysis

BACKGROUND

The success rate of surgical treatment for periprosthetic joint infection (PJI) remains inconsistent in the literature. Variability in PJI clinical guidelines and surgeon adherence to guidelines could affect treatment success. The objectives of this study were to appraise current recommendations for PJI management and develop a unified clinical standard of care, to perform a gap analysis of PJI cases in a tertiary institution to determine the rate of guideline adherence, and to determine if adherence to unified PJI guidelines affected 2-year treatment outcomes.

METHODS

We appraised the PJI guidelines from 3 academic medical societies, and consistent statements were aggregated. We retrospectively reviewed all PJI cases in a tertiary care institution. We defined PJI based on Musculoskeletal Infection Society PJI criteria. Surgeon adherence to preoperative, intraoperative, surgical and medical management guidelines was calculated, and we evaluated the association between guideline adherence and 2-year treatment outcomes.

RESULTS

The institutional rate of PJI was 1.13% (38 of 3368). Treatment success was 57.8% at 2 years. Unified guideline adherence percentages varied substantially: 92% of patients had preoperative erythrocyte sedimentation rate and C-reactive protein, 97% had intraoperative tissue cultures, 42% had appropriate preoperative arthrocentesis, and 74% underwent guideline-appropriate surgery. Performing appropriate preoperative arthrocentesis significantly correlated with positive treatment outcomes at 2 years (p = 0.028).

CONCLUSION

Adherence to PJI guidelines varies considerably, indicating that clinicians are either unaware of them or do not recognize their value for PJI treatment. This study shows the need for institution-based PJI treatment pathways that are consistent with published guidelines and the need to monitor adherence.

Synovial Fluid Biomarkers for the Diagnosis of Periprosthetic Joint Infection: A Systematic Review and Meta-Analysis

BACKGROUND

The search for a single standard reference test for determining periprosthetic joint infection (PJI) through analysis of synovial fluid has yielded numerous biomarkers as potential candidates. The purpose of the present systematic review and meta-analysis was to evaluate the diagnostic accuracy of synovial fluid biomarkers and to determine which test has the highest diagnostic odds ratio (DOR) for the diagnosis of PJI.

METHODS

An online literature search of the MEDLINE, Embase, and Cochrane databases identified 33 articles reporting a total of 13 major parameters for diagnosing PJI through analysis of synovial fluid. Each of the included articles was independently analyzed for risk of bias and for concerns regarding applicability utilizing the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool. The mada (meta-analysis of diagnostic accuracy) tool was used to generate forest plots for sensitivity, specificity, and the log of the DOR, as well as summary statistics.

RESULTS

In this analysis, 13 index tests (leukocyte count; measurement of the percentage of polymorphonucleocytes [PMN%] and the levels of C-reactive protein [CRP], α-defensin, leukocyte esterase [LE], interleukin [IL]-6, IL-8, IL-10, IL-1β, vascular endothelial growth factor [VEGF], and granulocyte-colony stimulating factor [G-CSF]; culture; and polymerase chain reaction [PCR] analysis) were evaluated on the basis of ≥2 articles. Of these tests, 8 (leukocyte count, PMN%, CRP, α-defensin, LE, IL-6, IL-8, and culture) were appropriate for pooled analysis. The overall sensitivity of these 8 markers was 0.85, and all but culture showed a sensitivity of ≥0.8. All markers showed a specificity of ≥0.9. Of the 8 tests, measurement of the α-defensin level showed the highest log DOR.

CONCLUSIONS

Synovial fluid leukocyte count, PMN%, CRP, α-defensin, LE, IL-6, and IL-8 all demonstrated high sensitivity for diagnosing PJI, with α-defensin being the best synovial marker based on the highest log DOR. However, other synovial fluid tests that demonstrate good diagnostic performance can also be used in combination for the diagnosis of PJI.

LEVEL OF EVIDENCE

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

Spectrum of Benign Articular and Periarticular Findings at FDG PET/CT

Whole-body fluorine 18 fluorodeoxyglucose (FDG) positron-emission tomography (PET)/computed tomography (CT) is performed primarily for oncologic indications; however, FDG uptake is not specific for malignancy. Herein we focus on causes of increased FDG uptake in and around joints, as lesions in these locations are commonly benign. A combination of primary intra-articular processes and osseous processes that may occur near the joint space will be discussed. Causes of intra-articular and periarticular increased FDG activity can be broadly divided into infectious, inflammatory, degenerative, and benign neoplastic categories. A familiarity with the full range of these processes is important to avoid misinterpretation, in turn decreasing unnecessary follow-up studies, procedures, and treatments. Differentiation from malignancy is often possible on the basis of a different level of FDG activity, divergent response to therapy, or differing changes over time, in comparison with a patient's known primary cancer. Recognizing an intra-articular lesion location can also be critical, as intra-articular metastases are rare. In some cases, benign FDG-avid articular and periarticular entities have a specific appearance at FDG PET/CT and a correct diagnosis may be made without any additional workup. In most other cases, comparison with prior studies and/or additional imaging can afford an accurate diagnosis. This review is meant to introduce the reader to a spectrum of benign FDG-avid articular and periarticular processes that may be encountered at oncologic FDG PET/CT to increase confidence and diagnostic accuracy. (©)RSNA, 2016.

What is the Diagnostic Accuracy of Aspirations Performed on Hips With Antibiotic Cement Spacers?

BACKGROUND

Periprosthetic joint infection is a serious complication after THA and commonly is treated with a two-stage revision. Antibiotic-eluting cement spacers are placed for local delivery of antibiotics. Aspirations may be performed before the second-stage reimplantation for identification of persistent infection. However, limited data exist regarding the diagnostic parameters of synovial fluid aspiration with or without saline lavage from a hip with an antibiotic-loaded cement spacer.

QUESTIONS/PURPOSES

We asked: (1) For hips with antibiotic cement spacers, does saline lavage influence the diagnostic validity of aspirations? (2) What is the diagnostic accuracy of preoperative aspirations performed on hips with antibiotic cement spacers using the Musculoskeletal Infection Society (MSIS) criteria, stratified by saline and nonlavage? (3) For hips with antibiotic spacers, what are the optimal thresholds for synovial fluid white blood cell (WBC) count and polymorphonuclear neutrophil (PMN) percentage for diagnosing infections?

METHODS

One hundred seventy-four hips (155 patients) with antibiotic-eluting cement spacers inserted between October 2012 and July 2015 were reviewed. Of these, 98 hips (80 patients) met the inclusion criteria and were included in the analysis (77 nonlavage, 21 saline lavage aspirations). Laboratory data from the aspiration and preoperative workup and intraoperative details were collected. Infection status of each hip procedure was determined based on a modified MSIS criteria using serologic, histologic, and intraoperative findings (sinus tract communicating with the joint at surgery or two positive intraoperative periprosthetic cultures with the same organism or two of the three following criteria: elevated erythrocyte sedimentation rate [ESR] [> 30 mm/hour] and C-reactive protein [CRP] [> 10 mg/L], a single positive intraoperative periprosthetic tissue culture, or a positive histologic analysis of periprosthetic tissue [> 5 neutrophils per high power field]). The diagnostic parameters were calculated for the MSIS criteria thresholds for synovial fluid (ie, WBC count > 3000 cells/µL and PMN percentage > 80%). Optimal thresholds were calculated for the corrected synovial WBC count and PMN percentage with a receiver operating characteristic curve. Separate analyses were performed for the hips with successful aspirations (nonlavage group) and those with saline lavage aspirations.

RESULTS

The WBC count and PMN percentage were higher in hips with infection than in hips without infection when nonlavage aspirations were done (WBC count, 6680 cells/µL ± 6980 cells/µL vs 2001 ± 4825; mean difference, 4679; 95% CI, 923-8436; p = 0.015; PMN percentage, 83% ± 13% vs 44% ± 30%; mean difference, 39%; 95% CI, 39%-49%; p < 0.001) and the findings between infected and noninfected aspirations were not different when saline lavage aspirations were done (WBC count, 782 cells/µL ± 696 vs 307 cells/µL ± 343; mean difference, 475; 95% CI, -253 to 1203; p = 0.161; PMN percentage, 67% ± 15% vs 58% ± 28%; mean difference, 10%; 95% CI, -11% to 30%; p = 0.331). Aspirations performed without lavage yielded good diagnostic accuracy in all parameters (WBC count, 78% [95% CI, 70%-86%]; PMN percentage. 79% [95% CI, 70%-88%]; positive culture: 84% [95% CI, 81%-90%]; at least one of the above: 79% [95% CI, 70%-88%]); but in the saline lavage group, none had WBC counts above the threshold (diagnostic accuracies for WBC count, 0%; PMN percentage, 71% [95% CI, 62%-86%]; positive culture, 76% [95% CI, 76%-86%]; at least one: 71% [95% CI, 57%-91%]). Because saline lavage did not result in differences between aspirations from infected and noninfected hips, we calculated the optimal thresholds in the nonlavage group only; the optimal threshold for synovial WBC count was 1166 cells/µL and for synovial PMN the percentage was 68%, which corresponds to WBC count diagnostic accuracy of 78% (95% CI, 69%-87%) and PMN percentage accuracy of 78% (95% CI, 69%-87%).

CONCLUSIONS

Because the MSIS criteria thresholds resulted in suboptimal sensitivities owing to a higher number of false negatives, we recommend considering lower WBC count and PMN percentage thresholds for hip-spacer aspirations. Furthermore, the WBC count and PMN percentage results from aspirations performed with saline lavage are not reliable for treatment decisions.

LEVEL OF EVIDENCE

Level III, diagnostic study.

The value of arthroscopic neosynovium biopsies to diagnose periprosthetic knee joint low-grade infection

INTRODUCTION

The diagnostic algorithm in cases of assumed low-grade infection after total knee arthroplasty is discussed controversial. The aim of this study was to evaluate the reliability of neosynovium biopsies via knee arthroscopies in predicting a periprosthetic knee joint infection (PJI).

METHODS

From 2010 to 2015, 56 consecutive patients received a diagnostic arthroscopy of the knee joint by reason of an assumed PJI. In 34 cases, a revision arthroplasty was performed after the diagnostic arthroscopy. The microbiologic and histologic results from neosynovium biopsies were compared to intraoperative findings of the consecutively performed revision arthroplasty.

RESULTS

The arthroscopic neosynovium biopsies had a sensitivity of 0.88 (0.47-1.0 95 % confidence interval), a specificity of 0.88 (0.7-0.98), a positive predictive value of 0.7 (0.35-0.93), and a negative predictive value of 0.96 (0.79-1.0). The accuracy was 0.88. We determined a higher sensitivity of neosynovium biopsies compared to C-reactive protein (p = 0.038) and white blood cell count (p < 0.001) in serum. The itemized evaluation of histologic results showed a significant higher sensitivity compared to microbiologic results (p = 0.045) and a higher accuracy.

CONCLUSIONS

The analysis of arthroscopic neosynovium biopsies can be helpful to verify or exclude a PJI in selected patients. Especially, histologic assessment showed a high accordance with final results. Level of evidence IV, retrospective study.

Does pre-operative sampling predict intra-operative cultures and antibiotic sensitivities in knee replacements revised for infection?: a study using the NJR dataset

PURPOSE

This study examined a cohort of primary knee arthroplasties revised for peri-prosthetic infection to (1) determine whether the microorganisms isolated by sampling (up to 6 months pre-operatively) are representative of the microorganisms encountered at the time of knee revision, (2) determine whether the antibiotic sensitivity profiles of matching organisms correlate and (3) determine whether the proportion of organism and antibiotic sensitivity matches is influenced by the type of infection, timing of sample collection and the type of microorganism isolated.

METHODS

From the National Joint Registry database for England and Wales, a consecutive series of primary knee arthroplasties performed between 2003 and 2014 that went on to have a revision for peri-prosthetic infection were identified. Each case was then linked to a national microbiology database held by Public Health England. Following data linkage, intra-operative and pre-operative cultures were identified and compared in a group of 75 patients.

RESULTS

Pre-operative genus matched intra-operative genus in 56 of 75 cases (75 %). Of those 56, the corresponding antimicrobial sensitivities matched in 37 (66 % of cases). Overall, 37 of 75 cases (49 %) matched for both microorganism and antimicrobial sensitivity. The proportion of matches was highest in the pure Staphylococcal genus infections (genus match 88 %, sensitivity match 62 %, genus and sensitivity match 55 %) and lowest in those patients with mixed organism infections (genus match 29 %, sensitivity match 14 %).

CONCLUSION

Pre-operative joint sampling obtained by either aspiration or tissue biopsy is advocated in cases where peri-prosthetic infection is suspected and provides the only means of determining infecting organism prior to revision. Overall, only half of all pre-operative cultures matched completely the findings of intra-operative samples in terms of both the microorganism(s) encountered and their corresponding antimicrobial sensitivity profile. Clinicians should be vigilant regarding the possibility of the patient acquiring further microorganisms or the development of new antibiotic resistance by the time of revision, especially in historic pre-operative cultures. Broad spectrum antibiotic therapies should therefore be employed until final microorganisms and antimicrobial sensitivities are confirmed from intra-operative samples.

LEVEL OF EVIDENCE

IV.

Diagnosis of Periprosthetic Joint Infection Following Hip and Knee Arthroplasty

The diagnosis of periprosthetic joint infection (PJI) following total hip arthroplasty and total knee arthroplasty has been one of the major challenges in orthopedic surgery. As there is no single absolute test for diagnosis of PJI, diagnostic criteria for PJI have been proposed that include using several diagnostic modalities. Focused history, physical examination, plain radiographs, and initial serologic tests should be followed by joint aspiration and synovial analysis. Newer diagnostic techniques, such as alpha-defensin and interleukin-6, hold great promise in the future diagnosis of equivocal infections.

Trends and Outcomes in the Treatment of Failed Septic Total Knee Arthroplasty: Comparing Arthrodesis and Above-Knee Amputation

BACKGROUND

Options for treatment of a failed septic total knee arthroplasty (TKA) include arthrodesis and above-knee amputation (AKA). Little comparative data exist to help clinicians when considering these alternatives.

METHODS

A national database was queried for patients who underwent either knee arthrodesis or AKA for an infected TKA between 2005 and 2012. Procedure volumes, postoperative complications, hospital charges, length of stay, and 90-day readmission rates were evaluated.

RESULTS

A total of 2634 patients underwent arthrodesis and 5001 patients underwent AKA for septic TKA. The percentage of total patients who underwent AKA increased significantly throughout the study period compared to knee arthrodesis. Patients who underwent AKA tended to be older and have more medical comorbidities. Arthrodesis patients had a significantly higher rate of postoperative infection (14.5% vs 8.3%, P < .0001) and transfusion (55.1% vs 46.8%, P < .0001), whereas AKA patients had a higher rate of systemic complications (31.5% vs 25.9%, P < .0001) and in-hospital mortality (3.7% vs 2.1%, P < .0001). The AKA cohort had lower hospital charges ($79,686 vs $84,747, P = .004), longer length of stay (11 vs 7 days, P < .0001), and higher 90-day readmission rate (19.4% vs 16.9%).

CONCLUSION

Our data suggest that there is an increasing trend toward AKA for the treatment of a failed infected TKA when compared to arthrodesis. Comparative analysis of the outcomes of these procedures should help the clinician when weighing these alternatives.

Outcome of total knee replacement following explantation and cemented spacer therapy

Background: Infection after total knee replacement (TKR) is one of the serious complications which must be pursued with a very effective therapeutic concept. In most cases this means revision arthroplasty, in which one-setting and two-setting procedures are distinguished. Healing of infection is the conditio sine qua non for re-implantation.

This retrospective work presents an assessment of the success rate after a two-setting revision arthroplasty of the knee following periprosthetic infection. It further considers drawing conclusions concerning the optimal timing of re-implantation.

Patients and methods: A total of 34 patients have been enclosed in this study from September 2005 to December 2013. 35 re-implantations were carried out following explantation of total knee and implantation of cemented spacer. The patient’s group comprised of 53% (18) males and 47% (16) females. The average age at re-implantation time was 72.2 years (ranging from 54 to 85 years). We particularly evaluated the microbial spectrum, the interval between explantation and re-implantation, the number of surgeries that were necessary prior to re-implantation as well as the postoperative course.

Results: We reported 31.4% (11) reinfections following re-implantation surgeries. The number of the reinfections declined with increasing time interval between explantation and re-implantation. Patients who developed reinfections were operated on (re-implantation) after an average of 4.47 months. Those patients with uncomplicated course were operated on (re-implantation) after an average of 6.79 months. Nevertheless, we noticed no essential differences in outcome with regard to the number of surgeries carried out prior to re-implantation. Mobile spacers proved better outcome than temporary arthrodesis with intramedullary fixation.

Conclusion: No uniform strategy of treatment exists after peri-prosthetic infections. In particular, no optimal timing can be stated concerning re-implantation. Our data point out to the fact that a longer time interval between explantation and re-implantation reduces the rate of reinfection. From our point of view, the optimal timing for re-implantation depends on various specific factors and therefore it should be defined individually.

Evaluation of the Role for Synovial Aspiration in the Diagnosis of Aseptic Loosening After Total Knee Arthroplasty

BACKGROUND

Aseptic prosthetic loosening is known to be an inflammatory, cellular process. We hypothesized that the synovial cell count would significantly differ among normal controls, patients with aseptic loosening, and patients with other etiologies of aseptic failure after total knee arthroplasty and thus that the cell count would be useful in the diagnosis of aseptic loosening.

METHODS

Over a six-year time period, all patients undergoing revision total knee arthroplasties at our institution underwent prospective intraoperative aspiration by the two senior authors. Each patient was assigned to a failure category on the basis of a priori criteria: aseptic loosening, periprosthetic infection, component wear, periprosthetic fracture, component malposition, instability, stiffness, and extensor mechanism failure. Simultaneously, patients with well-functioning total knee replacements underwent aspiration as normal controls. Aspirate characteristics were then compared between groups. Receiver-operating characteristic curves were created to determine optimal white blood-cell cutoffs when periprosthetic infection was compared with each individual failure category.

RESULTS

Thirty normal control patients and 433 patients who underwent revision total knee arthroplasties were included in this study. The synovial white blood-cell count in the normal control group was 558 ± 522 cells/μL, which did not significantly differ (p = 0.091) from that taken from patients with aseptic loosening (947 ± 1027 cells/μL). However, normal controls had significantly higher white blood-cell counts than subjects with stiffness (367 ± 392 cells/μL; p = 0.002) and significantly lower white blood-cell counts than subjects with periprosthetic fractures (1687 ± 1613 cells/μL; p = 0.002). Subjects with aseptic loosening had significantly higher white blood-cell counts than subjects with component malpositioning (p = 0.002) or stiffness (p = 0.001). When individual aseptic failure categories were compared with periprosthetic infection, the optimal white blood-cell cutoff varied widely, including 2104 cells/μL for component malposition and 4697 cells/μL for periprosthetic fracture, and the optimal differential segmented cell count percentages varied from 47% to 83%.

CONCLUSIONS

Although synovial fluid aspirates in patients with aseptic loosening and those with normal total knee arthroplasties did not differ, synovial fluid aspirate characteristics differed among categories of aseptic failure. As a result, the optimal diagnosis of periprosthetic infection on the basis of synovial aspiration results may need to utilize different cutoff values depending on the alternative mode of failure being considered. Large prospective studies will be necessary to validate these threshold values.

Two-stage revision total knee arthroplasty in cases of periprosthetic joint infection: an analysis of 50 cases

OBJECTIVES

A periprosthetic joint infection (PJI) is a significant complication after total knee arthroplasty (TKA). Still there is no agreement on a perfect diagnosis and treatment algorithm. The aim of this study was to evaluate the success and revision rates after two-stage revision total knee arthroplasty (TKA) and factors that affect the success rate.

MATERIAL AND METHODS

50 consecutive two-stage revision TKAs were performed between January 2011 and December 2012. We retrospectively reviewed study patient's charts including demographics, prior surgeries, comorbidities, incidence of persistent infection and revisions. At the final follow-up examination the patient's satisfaction, pain level and disorders were evaluated. A successful clinical outcome was defined as a functioning prosthesis without wound healing disorders, no sinuses tracts or other clinical evidence of a persistent infection. Results : Re-implantation of prosthesis was performed in 47 cases; three patients received a septic arthrodesis. Twelve patients had a persistent infection despite two-stage re-implantation resulting in a success rate of 76.0%. In eight of these twelve patients an infecting germ was isolated during second-stage procedure. Three patients received another two-stage revision arthroplasty and one patient an above knee amputation. A revision was performed in 23 of 50 patients (46.0%). Factors that diminish the success rate were further operations after primary TKA (p = 0.048), prior revision arthroplasties after TKA (p = 0.045), nicotine abuse (p = 0.048), Charlson comorbidity index above a score of 2 (p = 0.031) and a mixed flora during first-stage procedure (p < 0.001). Age, sex, immune status, chronic anticoagulant use, rheumatoid arthritis, body mass index and the presence of multidrug resistant germs showed no significant effect on success rate (p > 0.05). Conclusion : We found that patients who required surgery after the primary TKA, had a higher Charlson comorbidity index or were found to have mixed flora during explantation. The treatment of PJI remains difficult, both for the patient and for the treating surgeons.

Identification of periprosthetic joint infection after total hip arthroplasty

Although total hip arthroplasty (THA) is accepted as one of the most successful surgical procedures in orthopaedic surgery, periprosthetic joint infection after THA continues to be one of the most devastating complications. However, accurate preoperative identification of periprosthetic joint infection in patients presenting with joint pain or radiographic periprosthetic lucencies is often difficult, even after a comprehensive work-up. The purpose of this article is to review the diagnostic options available to improve the management and results of this potentially catastrophic complication.

Preoperative diagnostic for periprosthetic joint infection prior to total knee revision arthroplasty

Periprosthetic joint infection (PJI) after total knee arthroplasty remains a challenging problem. The aim of this study was to evaluate the accuracy of diagnostic knee aspiration and serum inflammatory markers in diagnostic of a PJI after total knee arthroplasty. Within 2011 and 2012, 46 patients received a one- or two-stage revision arthroplasty of the knee joint. These patients received a total number of 77 operations. A preoperative aspiration was performed in each case. We analyzed the microbiological and histological examinations of the samples from the aspiration and from the revision operation and additionally estimated serum inflammatory markers. The diagnostic aspiration had a specificity of 0.87, a sensitivity of 0.39, a positive predictive value of 0.67 and a negative predictive value of 0.68. For C-reactive protein the specificity was 0.61 and the sensitivity was 0.48, the serum white blood cell count had a specificity of 0.98 and a sensitivity of 0.23. Our data queries whether diagnostic joint aspiration or serum inflammatory markers are sufficient to verify or exclude a PJI.

Current concepts in knee replacement: complications

OBJECTIVE

The purposes of this article are to review current concepts of knee replacement, including features of traditional and newer prosthetic designs, materials, and surgical techniques; illustrate normal and abnormal postoperative imaging findings; and to relate the complications to current understanding of how and why these failures occur.

CONCLUSION

Complications after knee replacement may be asymptomatic. For this reason, assessment with postoperative imaging is important. The foundation of radiologic interpretation of knee replacement is knowledge of the physiologic purpose, orthopedic trends, imaging findings, and complications.

Evaluation and Management of Periprosthetic Joint Infection-an International, Multicenter Study

BACKGROUND

Controversies still exist regarding the optimal diagnostic and therapeutic strategies in patients with prosthetic joint infections (PJI).

QUESTIONS/PURPOSES

How effective are preoperative and intraoperative cultures in isolating organisms and how do these culture results compare to one another? What are the results of surgical treatment of PJI in the hip and knee in an international, tertiary referral center cohort?

PATIENTS AND METHODS

One hundred sixteen patients (N = 59 hip PJI, N = 57 knee PJI) were recruited prospectively to registries at three international, tertiary referral centers between December 2008 to November 2011. Retrospective review of prospective registry data including demographics, microbiology results, and operative reports was performed.

RESULTS

Preoperative synovial fluid aspiration yielded an organism in only 45.2% and 44.4% of cases, respectively, for knee and hip PJI. False-negative rates of preoperative aspiration relative to intraoperative culture were 56% and 46% in hip and knee PJI, respectively, with discordance rates of 25% and 21.4%, respectively. Rates of negative intraoperative cultures were 15% in hip PJI and 20.7% in knee PJI. Open debridement with prosthetic retention was the most common initial revision procedure performed (48.3% of hip PJI and 63.8% of knee PJI). This method of revision was successful in 41.3% of hip PJI and 59.4% of knee PJI. Initial failure rates for prosthetic revision was lower than debridement with prosthetic retention but remained substantial in both hip PJI (initial success of one-stage exchange 60% and two-stage exchange 70%) and knee PJI (initial success of one-stage exchange 80% and two-stage exchange 75%).

CONCLUSION

Diagnosis and treatment of PJI remains challenging with difficulty in isolating the offending organism and with high rates of prosthetic revision and initial treatment failures. Future advances in organism isolation and international standardization of treatment protocols may improve patient outcomes.

Indicators for detection of septic arthritis in the acutely swollen joint cohort of those without joint prostheses

Differentiating septic arthritis from culture-negative, acute atraumatic joint effusion is difficult. Studies have attempted to elucidate factors that herald infection, but, due to overlap, most conclude that the diagnosis ultimately relies on clinical judgment. Furthermore, studies are limited by broad inclusion criteria. The current retrospective case study sought to examine (1) which markers differentiate a culture-positive septic joint from culture-negative effusion in patients suspicious for infection despite no growth on Gram stain and without previous surgery in the affected joint and (2) whether threshold values of these markers exist that predict septic arthritis. The study was performed by reviewing records of those who underwent operative irrigation and debridement involving the shoulder, elbow, wrist, hip, knee, and ankle. Patients were included if they were older than 18 years and had an acutely swollen/painful joint and no organisms on initial Gram stain. Exclusion criteria were lack of serum markers or synovial fluid aspirate, antibiotics within 1 week, adjacent wound or skin infection, recent trauma to the joint, and previous joint infection or surgery to the joint. Several clinical, serological, and synovial parameters were collected and analyzed using paired t test with Bonferonni correction. Serum C-reactive protein was the only significantly different variable between groups. Serum C-reactive protein greater than 10.5 mg/dL was predictive of infection. In those suspicious for infection despite no growth on Gram stain and without previous surgery in the affected joint, C-reactive protein greater than 10.5 mg/dL is suspicious for joint sepsis and should warrant consideration for urgent irrigation and debridement.

Effectiveness of aspiration in knee joint effusion management: a prospective randomized controlled study

PURPOSE

Knee effusion is a common symptom in various knee disorders of both traumatic and non-traumatic aetiology. Although intra-articular aspiration is a widespread treatment approach, its beneficial effect has not been confirmed by a randomized controlled study. The purpose was to evaluate the effectiveness and safety of joint aspiration in acute knee effusion, in relation to traumatic or non-traumatic aetiology.

METHODS

One hundred and sixty-seven consecutive patients with acute knee joint effusion were allocated in a randomized controlled fashion into two groups. In the first group, joint aspiration was performed, while in the second group, no aspiration was performed. Range of motion, pain relief, use of analgesics and oedema were evaluated post management. The Knee Society Score and the International Knee Documentation Committee Subjective Evaluation Form were also obtained. In addition, a subgroup analysis of our results in relation to the presence of trauma or not was performed.

RESULTS

Aspiration exhibited a temporary improvement in all clinical parameters evaluated, especially in the post-traumatic effusion. However, this improvement lasted only for the first week, due to the early re-accumulation of the effusion. There was no difference between the different groups regarding the clinical outcome in neither trauma or non-trauma patients at the end of the follow-up period. Aspiration aided in earlier establishment of the diagnosis in the non-trauma cases of effusion.

CONCLUSIONS

Aspiration resulted in only temporary improvement of the outcome in the treatment of traumatic or not traumatic knee effusion. Aspiration is suggested in effusions of unknown origin in order to establish the diagnosis and for immediate clinical relief. However, aspiration should be performed with consideration in the presence of trauma.

The routine use of atypical cultures in presumed aseptic revisions is unnecessary

BACKGROUND

In presumed aseptic hip and knee revisions, it is common practice to send intraoperative cultures to screen for occult infection. Currently no guidelines exist for the routine use of acid-fast bacillus (AFB) and fungal cultures in this setting.

QUESTIONS/PURPOSES

We established (1) the rate of positive fungal and AFB cultures in aseptic hip and knee revision arthroplasties, (2) factors associated with positive fungal and AFB cultures, (3) the likelihood that positive cultures represent true-positive results, and (4) the hospital charges of sending fungal and AFB cultures routinely.

METHODS

We retrospectively evaluated all 1717 presumed aseptic hip and knee revisions performed from January 2006 to November 2011: 1139 patients had at least one intraoperative fungal culture and 1133 patients had at least one intraoperative AFB culture, with 923 and 920, respectively, achieving 1-year followup. The Musculoskeletal Infection Society criteria were used to classify subsequent infections. We attempted to identify risk factors for positive cultures.

RESULTS

We observed six (0.5%) patients with positive AFB cultures and 19 (1.7%) with positive fungal cultures. Patients undergoing reimplantation procedures were more likely to have a positive fungal culture. The true-positive rate was 0% and 0.1% for AFB and fungal cultures, respectively. The total hospital charges for these cultures over the time frame of our study were USD 1,315,533.

CONCLUSIONS

Given the extremely low rate of true-positive AFB and fungal cultures in presumed aseptic revision joint arthroplasty and the charges associated with maintaining these cultures, we believe their routine use is unwarranted.

LEVEL OF EVIDENCE

Level III, prognostic study. See the Instructions for Authors for a complete description of evidence.

Correlation of aspiration results with aseptic loosening in total hip arthroplasty

In the evaluation of patients with a persistently painful total hip arthroplasty establishing an accurate diagnosis is paramount in the selection of a successful treatment regimen. It is unknown whether synovial analysis might differentiate aseptic loosening from other causes of failure. A physiological basis exists to suggest that aseptic loosening might be a process of non-segmented leukocytes. The objective of this study was to determine if the synovial fluid differential cell count might aid in the diagnosis of aseptic loosening. A retrospective chart review of all patients who had undergone revision hip arthroplasty with pre-operative or intra-operative aspiration results was performed. Aseptic loosening was defined as gross intraoperative movement in the absence of infection. From these results Relative-Operating Characteristic (ROC) curves were created, and sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. A diagnosis of aseptic loosening was established in 76 of the 253 hips. The ROC curves indicated that lymphocyte count does have utility in the diagnosis of aseptic loosening. If an aspirate has a combination of fewer than 2500 WBCs (sensitivity 93%, specificity 42%, NPV 94%, accuracy 57%) or more than 10% lymphocytes (sensitivity 86%, specificity 42%, NPV 87%, accuracy 55%) then the sensitivity for aseptic loosening is 96%, the specificity is 33%, the NPV is 95% and the accuracy is 52%. In patients with painful total hip arthroplasties in whom infection has been excluded, aspiration data can be a useful adjunct in the diagnosis of aseptic loosening. In aspirates with neither a WBC cell count of less than 2500 nor a lymphocyte cell count of greater than 10% aseptic loosening can be effectively "ruled out" as fewer than 5% of these patients will have aseptic loosening. While non-specific, aspirate differential can be useful to "rule-out" aseptic loosening with a sensitivity and negative predictive value well exceeding that of standard radiographs.

Usefulness of histology for predicting infection at the time of hip revision for the treatment of Vancouver B2 periprosthetic fractures

When facing a Vancouver B2 periprosthetic fracture, the most recommended treatment is the prosthesis replacement. Current tests do not provide enough reliability to identify whether the fracture has been produced on a septic or an aseptic loosened prosthesis. Our aim was to evaluate the usefulness of the histology for the diagnosis of infection in these cases. A total of 11 hip revision procedures were performed (mean age: 78.1 years, 8 women and 3 men). Sensitivity, specificity, positive predictive value and negative predictive value of the histology were 100%, 55.5%, 33.3% and 100% respectively. Of the six patients presenting with a positive histology, four of them had negative cultures (66.6% of false positives). Our results suggest that periprosthetic fractures are a cause of false-positive histology results for the diagnosis of infection during revision of a hip prosthesis for the treatment of Vancouver B2 periprosthetic fractures.

Utility of synovial fluid aspirations in failed metal-on-metal total hip arthroplasty

White blood cell (WBC) count and neutrophil percentage from preoperative synovial fluid aspirations are used to help determine the presence or absence of periprosthetic joint infection (PJI) in failed total hip arthroplasty (THA). The clinical levels indicative of infection have not been delineated in metal-on-metal (MoM) bearings. We identified 39 patients who received a preoperative synovial fluid aspiration prior to MoM revision. Thirty-five of 39 cases were culture negative and 4 of 39 were culture positive. WBC count >3000 cells/μL was 100% sensitive and 57.1% specific. Neutrophil percentage >80% was 100% sensitive and 97.1% specific. Both CRP and ESR >8.0mg/L and >22 mm/h, respectively were 75.0% sensitive and 67.6% specific. Our data suggest that synovial WBC count and serum ESR and CRP have poor predictive value in diagnosing PJI for failed MoM THA, whereas synovial neutrophil percentage is a highly accurate marker for diagnosing infection in this patient population.

Wound closure

In this paper, we consider wound healing after total knee arthroplasty.

Percutaneous interface biopsy in dry-aspiration cases of chronic periprosthetic joint infections: a technique for preoperative isolation of the infecting organism

PURPOSE

Preoperative identification of the infecting micro-organism is of paramount importance in the treatment protocol for chronic periprosthetic joint infections, as it enables selection of the most appropriate antibiotic treatment. Preoperative joint aspiration, the most commonly used sampling technique, has proven to have a broad range of sensitivity values and the frequency of dry aspirations has not been well assessed. In such dry-tap cases a biopsy sample could be an option. The purpose of this study was to assess the diagnostic accuracy of percutaneous interface biopsy (PIB) in isolating the infecting organism in cases of chronic Periprosthetic Joint Infection (PJI) and dry-tap event. The basic technique is to harvest and culture a sample from the periprosthetic interface membrane by a percutaneous technique in the preoperative period.

METHODS

A retrospective study was done involving 24 consecutive patients suspected of PJI and where no fluid was obtained from the joint. Culture results from a percutaneous interface biopsy (PIB) were compared with intraoperative tissue cultures at the time of revision surgery. In all cases, a two-stage replacement was done.

RESULTS

The sensitivity was 88.2%; specificity was 100%. Positive predictive value was 100%, while negative predictive value was 77.9%. Accuracy was 91.6%. No technique-related complication was observed.

CONCLUSION

We conclude that PIB is a useful test for preoperative isolation of the infecting organism and could play a role in cases with dry-tap joint aspirations.