Joint aspiration, including culture of reaspirated saline after a 'dry tap', is sensitive and specific for the diagnosis of hip and knee prosthetic joint infection

Imaging approach to prosthetic joint infection

The diagnosis of prosthetic joint infection (PJI) remains challenging, despite multiple available laboratory tests for both serum and synovial fluid analysis. The clinical symptoms of PJI are not always characteristic, particularly in the chronic phase, and there is often significant overlap in symptoms with non-infectious forms of arthroplasty failure. Further exacerbating this challenge is lack of a universally accepted definition for PJI, with publications from multiple professional societies citing different diagnostic criteria. While not included in many of the major societies' guidelines for diagnosis of PJI, diagnostic imaging can play an important role in the workup of suspected PJI. In this article, we will review an approach to diagnostic imaging modalities (radiography, ultrasound, CT, MRI) in the workup of suspected PJI, with special attention to the limitations and benefits of each modality. We will also discuss the role that image-guided interventions play in the workup of these patients, through ultrasound and fluoroscopically guided joint aspirations. While there is no standard imaging algorithm that can universally applied to all patients with suspected PJI, we will discuss a general approach to diagnostic imaging and image-guided intervention in this clinical scenario.

When to lavage in the absence of a sonographically visible joint effusion in painful total knee arthroplasty: a retrospective longitudinal study

OBJECTIVE

To determine if knee arthroplasty without sonographically visible effusion needs to undergo lavage to rule out infection.

METHODS

Patients were accrued by a retrospective search of a longitudinally maintained radiology database looking for patients referred for ultrasound guided aspiration of suspected TKA infection. Clinical presentations, laboratory tests, intraoperative findings, and follow-up were reviewed.

RESULTS

Four hundred sixty-nine patients were included (mean age of 67 years (range, 36-91)) including 251 females. Four hundred three patients had effusions, of which 57 were infected based on ultrasound-guided and surgical aspirates. Sixty-four patients lacked effusions, of which 47 underwent lavage at the clinicians' request, with 6/47 infected. Nineteen patients without effusion were not lavaged at the clinicians' request due to low suspicion, and none were infected. Patients with positive lavage cultures all had clinical risk factors. Infection rates were significantly higher in patients with joint effusion and clinical suspicion for infection compared to absent joint effusion and absent clinical suspicion. A significantly higher proportion of patients with hyperemia or moderate-severe synovial thickening on ultrasound were symptomatic and had joint effusion and positive joint cultures. Aspiration of native fluid had 85% sensitivity and 100% specificity while lavage had a sensitivity of 57% and specificity of 100%. Negative predictive value for native aspirates was 94% compared to 86% for lavage.

CONCLUSION

A TKA with low clinical suspicion of infection does not need to undergo lavage in the absence of a sonographically visible effusion.

A "Dry Tap" in Prosthetic Joint Infection Workup of Total Hip Arthroplasty Is Not Reassuring

BACKGROUND

Synovial fluid analysis is important in diagnosing prosthetic joint infection (PJI). The rate of culture-positive PJI in patients who have a dry tap of a total hip arthroplasty (THA) is not well described.

METHODS

We reviewed all image-guided THA aspirations, performed from 2014 to 2021 at a single academic institution. Aspirations were categorized as successful (≥ 0.5 mL) or unsuccessful (< 0.5 mL, "dry tap"). We analyzed culture data on all repeat aspirations and revision surgeries performed within 90 days of the initial dry tap.

RESULTS

We reviewed 275 consecutive attempted THA aspirations of which 100 (36.4%) resulted in a dry tap. The dry tap cohort had a significantly higher percentage of fluoroscopic-guided aspirations (64%) and fewer ultrasound-guided aspirations (36%) compared to the successful aspiration cohort (48.9% fluoroscopic, 53.1% ultrasound, P = .0061). Of the 100 patients who have dry taps, 48 underwent revision surgery within 90 days of the initial dry tap, and 15 resulted in 2 or more positive cultures. The rate of PJI defined by MusculoSkeletal Infection Society major criteria in the dry tap cohort was 16.0%.

CONCLUSIONS

Attempted aspiration of a THA resulted in a dry tap 36.4% of the time. Of those patients who had a dry tap, 16.0% were subsequently found to have PJI based on MusculoSkeletal Infection Society major criteria. Therefore, a "dry tap" does not exclude the diagnosis of infection and should not be considered reassuring for the absence of PJI.

Pre-aspiration outpatient ultrasound can accurately predict dry taps in prosthetic hips suspected of infection; a prospective study

Introduction

Aspiration represents the most potent method for exploring the potential occurrence of Periprosthetic Joint Infection (PJI). However, dry taps are common. While aspiration under ultrasound (US) guidance in the radiology department has become increasingly popular, hip aspiration is still routinely conducted in the operating room (OR) under x-ray guidance in numerous medical centers. When conducted within the confines of the OR, a dry tap aspiration not only subjects the patient to an unnecessary invasive procedure but also constitutes a substantial strain on OR time and resources. Our objective was to assess whether an outpatient US conducted before aspiration could reliably predict the likelihood of encountering a dry hip aspiration.

Methods

In a prospective study, we enrolled 50 hips who were suspected of PJI and slated for revision total hip arthroplasty and required hip aspiration. Before the aspiration procedure, we conducted an outpatient hip ultrasound (US) to assess the presence of fluid collection. Subsequently, all patients underwent aspiration under fluoroscopy in the OR, irrespective of the ultrasound findings We then assessed the level of agreement between the ultrasound results and the outcomes of hip aspiration.

Results

The US exhibited a sensitivity of 95.7% (95% CI 69.8-91.8), a specificity of 74.1% (95% CI 52.8-91.8), a positive predictive value of 75.9% (95% CI 50.9-91.3), and a negative predictive value of 95.2% (95% CI 71.3-99.8) in predicting the success of aspiration.

Discussion

Pre-aspiration outpatient US demonstrates a high degree of accuracy in predicting dry taps in these patients. We recommend its incorporation into the hip aspiration procedure in medical centers where aspiration is performed in the operating room. In the broader context, these findings reinforce the preference for US-guided aspiration within the radiology department over x-ray-guided aspiration in the operating room since about ¼ of the positive USs for hip collection will lead to a dry tap if the aspiration is performed in the OR under fluoroscopy guidance.

Differences in Diagnostic Sensitivity of Cultures Between Sample Types in Periprosthetic Joint Infections: A Systematic Review and Meta-Analysis

BACKGROUND

Differences between the bacterial culture results of the preoperative fluid, intraoperative tissue, and sonication fluid of implants in the diagnosis of periprosthetic joint infection (PJI) are important issues in clinical practice. This study aimed to identify the differences in pooled diagnostic accuracy between culture sample types for diagnosing PJI by performing a systematic review and meta-analysis.

METHODS

This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement. A comprehensive literature search of PubMed, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Library databases was performed. Data extraction and study assessment using the quality assessment of diagnostic accuracy studies were performed independently by two reviewers. The pooled sensitivity, specificity, summary receiver operating characteristic curve, and area under the summary receiver operating characteristic curve were estimated for each sample type.

RESULTS

There were thirty-two studies that were included in the analysis after screening and eligibility assessment. The pooled sensitivities of preoperative fluid, intraoperative tissue, and sonication fluid for the diagnosis of PJI were 0.63 (95% confidence interval [CI] 0.56 to 0.70), 0.71 (95% CI 0.63 to 0.79), and 0.78 (95% CI 0.68 to 0.85), while the specificities were 0.96 (95% CI 0.93 to 0.98), 0.92 (95% CI 0.86 to 0.96), and 0.91 (95% CI 0.83 to 0.95), respectively. The area under the curves for preoperative fluid, intraoperative tissue, and sonication fluid were 0.86, 0.88, and 0.90, respectively.

CONCLUSIONS

Sonication fluid culture demonstrated better sensitivity compared with the conventional culture method, and preoperative fluid culture provided lower sensitivity in diagnosing PJI.

US-Guided Interventional Procedures for Total Hip Arthroplasty

In patients with total hip arthroplasty (THA) with recurrent pain, symptoms may be caused by several conditions involving not just the joint, but also the surrounding soft tissues including tendons, muscles, bursae, and peripheral nerves. US and US-guided interventional procedures are important tools in the diagnostic work-up of patients with painful THA given that it is possible to reach a prompt diagnosis both directly identifying the pathological changes of periprosthetic structures and indirectly evaluating the response and pain relief to local injection of anesthetics under US monitoring. Then, US guidance can be used for the aspiration of fluid from the joint or periarticular collections, or alternatively to follow the biopsy needle to collect samples for culture analysis in the suspicion of prosthetic joint infection. Furthermore, US-guided percutaneous interventions may be used to treat several conditions with well-established minimally invasive procedures that involve injections of corticosteroid, local anesthetics, and platelet-rich plasma or other autologous products. In this review, we will discuss the clinical and technical applications of US-guided percutaneous interventional procedures in painful THA that can be used in routine daily practice for diagnostic and therapeutic purposes.

The Value of Preoperative Ultrasound-Determined Fluid Film and Joint Aspiration in Revision Hip Arthroplasty

BACKGROUND

Data regarding the diagnostic value of ultrasound (US)-determined fluid film and joint aspiration prior to revision total hip arthroplasty for suspected periprosthetic joint infections (PJIs) are limited. This study aimed to analyze the value of US-determined fluid film, characterized the preoperative and intraoperative microbiological spectrum and resistance patterns, and compared the concordance between preoperative synovial fluid and intraoperative culture results.

METHODS

We analyzed 366 US examinations from 324 patients prior to revision total hip arthroplasty. Selected cases were grouped into clearly infected, noninfected, and inconclusive cohorts, according to the International Consensus Meeting 2018 Criteria. For US-determined fluid film <1 mm, no aspiration was performed based on our institutional protocol. Patients were grouped into no aspiration (144 of 366; [39.3%]), dry tap (21 of 366; [5.7%]), and a successful tap (201 of 366; [54.9%]). The microbiological spectrum and antibiograms were compared between preoperative and intraoperative results.

RESULTS

The absence of US-determined fluid film showed no correlation with the presence of a hip PJI. Overall, 31.9% cases of the no-aspiration group had a PJI. In total, 13.5% discrepancies were found between successful taps and intraoperative cultures. The most prevalent microorganisms in preoperative synovial fluid were Staphylococcus epidermidis and Staphylococcus aureus (20.8%), while intraoperatively S. epidermidis (26.3%) and Cutibacterium acnes (14.5%) were leading. Additional microorganisms were identified in 32.5% of intraoperative cultures. There were no differences between resistance patterns of preoperative and intraoperative concordant microorganisms.

CONCLUSIONS

Absence of US-determined fluid film cannot rule out the presence of a hip PJI. Combined microbiological results from hip US aspirations and subsequent surgical procedures are crucial to design an effective treatment for suspected hip PJI.

Identification of immune infiltration and immune-related biomarkers of periprosthetic joint infection

Background

The immune response associated with periprosthetic joint infection (PJI) is an emerging but relatively unexplored topic. The aim of this study was to investigate immune cell infiltration in periprosthetic tissues and identify potential immune-related biomarkers.

Methods

The GSE7103 dataset from the GEO database was selected as the data source. Differentially expressed genes (DEGs) and significant modular genes in weighted correlation network analysis (WGCNA) were identified. Functional enrichment analysis and transcription factor prediction were performed on the overlapping genes. Next, immune-related genes from the ImmPort database were matched. The protein-protein interaction (PPI) analysis was performed to identify hub genes. CIBERSORTx was used to evaluate the immune cell infiltration pattern. Spearman correlation analysis was used to evaluate the relationship between hub genes and immune cells.

Results

A total of 667 DEGs were identified between PJI and control samples, and 1847 PJI-related module genes were obtained in WGCNA. Enrichment analysis revealed that the common genes were mainly enriched in immune and host defense-related terms. TFEC, SPI1, and TWIST2 were the top three transcription factors. Three hub genes, SDC1, MMP9, and IGF1, were identified in the immune-related PPI network. Higher levels of plasma cells, CD4+ memory resting T cells, follicular helper T cells, resting mast cells, and neutrophils were found in the PJI group, while levels of M0 macrophages were lower. Notably, the expression of all three hub genes correlated with the infiltration levels of seven types of immune cells.

Conclusion

The present study revealed immune infiltration signatures in the periprosthetic tissues of PJI patients. SDC1, MMP9, and IGF1 were potential immune-related biomarkers for PJI.

Assessing the Diagnostic Accuracy of Next-Generation Sequencing in Patients With Antibiotic Spacers Before Reimplantation

Use of molecular sequencing modalities in periprosthetic joint infection diagnosis and organism identification has gained popularity recently. To date, there is no diagnostic test that reliably predicts infection eradication in patients with antibiotic spacers. The purpose of this study was to compare the diagnostic accuracy of next-generation sequencing (NGS), culture, the Musculoskeletal Infection Society (MSIS) criteria, and the criteria by Parvizi et al in patients with antibiotic spacers. In this retrospective study, aspirate or tissue samples were collected from 38 knee and 19 hip antibiotic spacers for routine diagnostic workup for the presence of persistent infection and sent to the laboratory for NGS. The kappa statistic along with statistical differences between diagnostic studies were calculated using the chi-square test for categorical data. The kappa coefficient for agreement between NGS and culture was 0.27 (fair agreement). The percentages of positive and negative agreement were 22.8% and 42.1%, respectively, with a total concordance of 64.9%. There were 12 samples that were culture positive and NGS negative. Eight samples were NGS positive but culture negative. The kappa coefficient was 0.42 (moderate agreement) when comparing NGS with MSIS criteria. In our series, NGS did not provide sufficient agreement compared with culture or MSIS criteria in the setting of an antibiotic spacer. A reliable diagnostic indicator for reimplantation has yet to be identified. [Orthopedics. 2024;47(1);46-51.].

Is ultrasound-guided hip aspiration more successful than fluoroscopic-guided aspiration in diagnosing prosthetic joint infection?

Introduction: aspiration of total hip arthroplasty (THA) is commonly performed to assist in the diagnosis of prosthetic joint infection (PJI). This study aimed to determine whether fluoroscopic- or ultrasound- guided hip aspiration differs in the ability to acquire synovial fluid and in the accuracy of diagnosing infection. Methods: all THA aspirations performed between 2014 and 2021 at our institution were retrospectively identified. Aspirations were classified as successful or dry. If successful, the volume of fluid obtained was recorded. The sensitivity and specificity of hip aspiration in identifying PJI were calculated with four methods: (1) culture results excluding saline lavage, (2) culture results including saline lavage, (3) 2018 Musculoskeletal Infection Society (MSIS) International Consensus Meeting (ICM) criteria, and (4) 2021 European Bone and Joint Infection Society (EBJIS) criteria. Analyses were performed using Student's t test or Wilcoxon rank sum for continuous variables and chi-squared or Fisher's exact test for categorical variables. Results: 290 aspirations were included (155 fluoroscopic-guided and 135 ultrasound-guided). Success of aspiration (> 0.5  mL) was more common in the ultrasound cohort (69 %) than fluoroscopy (53 %) (p < 0.0055 ). When successful, more volume was obtained in the ultrasound cohort (mean 13.1 mL vs. 10.0 mL; p = 0.0002 ). Ultrasound-guided aspiration was more sensitive than fluoroscopy in diagnosing PJI using culture results excluding saline lavage (85 % vs. 73 %; p = 0.03 ), culture results including saline lavage (85 % vs. 69 %; p = 0.001 ), 2018 MSIS-ICM criteria (77 % vs. 52 %; p = 0.02 ), and 2021 EBJIS criteria (87 % vs. 65 %; p = 0.02 ). Ultrasound-guided aspiration was more specific than fluoroscopy in diagnosing PJI using 2021 EBJIS criteria (100 % vs. 96 %; p = 0.001 ). Conclusions: ultrasound-guided aspiration is more frequently successful and yields more fluid than fluoroscopic-guided aspiration of THA. Ultrasound-guided aspiration is more sensitive in diagnosing PJI than fluoroscopy using culture data, 2018 MSIS-ICM criteria, and 2021 EBJIS criteria.

The Role of Single Positive Cultures in Presumed Aseptic Total Hip and Knee Revision Surgery-A Systematic Review of the Literature

(1) Background: Prior to revision hip (THA) or knee arthroplasty (TKA), periprosthetic low-grade infection (PJI) should be ruled out. Despite advances in preoperative diagnosis, unsuspected positive cultures (UPCs) may occur in initially planned aseptic revisions. Particularly, single UPCs pose a diagnostic and therapeutic dilemma, as their impact on outcome is unclear and recommendations are heterogeneous. This review investigates the frequency of single UPCs and their impact on implant survivorship. (2) Methods: In July 2022, a comprehensive literature search was performed using PubMed and Cochrane Library search. In total, 197 articles were screened. Seven retrospective studies with a total of 5821 cases were able to be included in this review. (3) Results: Based on the cases included, UPCs were found in 794/5821 cases (14%). In 530/794 cases (67%), the majority of the UPCs were single positive. The most commonly isolated pathogens were coagulase negative Staphylococci and Cutibacterium acnes. Five of seven studies reported no influence on revision- or infection-free survival following a single positive culture. In two studies, single UPCs following THA revision were correlated with subsequent re-revision for PJI. (4) Conclusions: Single UPCs of a non-virulent pathogen following presumed aseptic TKA revision may be interpreted as contaminants. A single UPC following THA revision may be a risk factor for subsequent PJI. The role of systemic antibiotic treatment remains unclear, but it should be considered if other risk factors for PJI are present.

Fluoroscopic-guided procedures of the lower extremity

This article reviews the literature and the authors' experiences regarding the performance of lower extremity fluoroscopically guided procedures from the hip to the toes. An overview of injections and aspirations, their indications, risks, and complications are provided, focusing on anesthetics, corticosteroids, and contrast agents. A variety of approaches to each joint and the associated pearls and pitfalls of each approach will be discussed.

Image-guided synovial biopsy with a focus on infection

Image-guided biopsy of the synovium is a relatively uncommon but safe procedure with a high-diagnostic yield in the correct clinical scenario. Whilst surgical and arthroscopic techniques are still commonly performed and remain the gold standard, they are more invasive, expensive and not widely available. Ultrasound and X-ray-guided synovial biopsy are being increasingly performed by radiologists to diagnose both native and periprosthetic joint infection (PJI) to guide surgical and microbiological management. The purpose of this review article is to present the historical background to synovial biopsy particularly related to potential joint infection, including common and uncommon pathogens encountered, sampling techniques and pitfalls, focusing mainly on its role in PJI and its role in patient pathways and decision-making within a joint infection multi-disciplinary framework.

Elevated ESR and CRP Prior to Second-Stage Reimplantation Knee Revision Surgery for Periprosthetic Joint Infection Are Associated with Increased Reinfection Rates

Although two-stage revision surgery is considered as the most effective treatment for managing chronic periprosthetic joint infection (PJI), there is no current consensus on the predictors of optimal timing to second-stage reimplantation. This study aimed to compare clinical outcomes between patients with elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) prior to second-stage reimplantation and those with normalized ESR and CRP prior to second-stage reimplantation. We retrospectively reviewed 198 patients treated with two-stage revision total knee arthroplasty for chronic PJI. Cohorts included patients with: (1) normal level of serum ESR and CRP (n = 96) and (2) elevated level of serum ESR and CRP prior to second-stage reimplantation (n = 102). Outcomes including reinfection rates and readmission rates were compared between both cohorts. At a mean follow-up of 4.4 years (2.8-6.5 years), the elevated ESR and CRP cohort demonstrated significantly higher reinfection rates compared with patients with normalized ESR and CRP prior to second-stage reimplantation (33.3% vs. 14.5%, p < 0.01). Patients with both elevated ESR and CRP demonstrated significantly higher reinfection rates, when compared with patients with elevated ESR and normalized CRP (33.3% vs. 27.6%, p = 0.02) as well as normalized ESR and elevated CRP (33.3% vs. 26.3%, p < 0.01). This study demonstrates that elevated serum ESR and/or CRP levels prior to reimplantation in two-stage knee revision surgery for chronic PJI are associated with increased reinfection rate after surgery. Elevation of both ESR and CRP were associated with a higher risk of reinfection compared with elevation of either ESR or CRP, suggesting the potential benefits of normalizing ESR and CRP prior to reimplantation in treatment of chronic PJI.

Simple and inexpensive synovial fluid biomarkers for the diagnosis of prosthetic joint infection according to the new EBJIS definition

Introduction: diagnosis of periprosthetic joint infection (PJI) is challenging, as no single test has absolute accuracy. The purpose of this study was to assess the utility of different simple synovial biomarkers in the diagnosis of PJI as defined by the European Bone and Joint Infection Society (EBJIS). Methods: we retrospectively identified all patients undergoing revision hip or knee arthroplasty from 2013 to 2019 on our prospectively maintained database. Only patients with minimum required infection diagnostic workup were included in the study. Patients with comorbidities that may influence the accuracy of synovial biomarkers were excluded. Receiver operator characteristic (ROC) curves were utilised to assess the diagnostic utility of synovial fluid white blood cell (WBC) count, polymorphonuclear leukocyte percentage (PMN %), C-reactive protein (CRP), adenosine deaminase (ADA), and alpha-2-microglobulin (A2M). Results: in total, 102 patients met the inclusion criteria. Of these, 58 were classified as infection unlikely, 8 as infection likely, and 36 as infection confirmed. Synovial WBC count (area under the curve (AUC) 0.94) demonstrated the best utility for the diagnosis of PJI, followed by PMN % (AUC 0.91), synovial CRP (AUC 0.90), ADA (AUC 0.82), and A2M (AUC 0.76). We found added value in the combined interpretation of different biomarkers. We calculated high sensitivity and negative predictive value if at least two of them are negative and high specificity and positive predictive value if at least two are elevated. Conclusion: current results show that synovial fluid investigation is a useful tool for the diagnosis of PJI, and the combined interpretation of simple and inexpensive biomarkers demonstrated improved diagnostic accuracy.

The Ratio of IL-6 to IL-4 in Synovial Fluid of Knee or Hip Performances a Noteworthy Diagnostic Value in Prosthetic Joint Infection

The diagnosis of prosthetic joint infection (PJI) is still a challenge, the ratio of interleukin-6 (IL-6) to IL-4 in the joint fluid of knee or hip was used to analyze whether the diagnostic accuracy of PJI can be improved. Between January 2017 and May 2022, 180 patients who developed pain after revision total hip or knee arthroplasty were enrolled retrospectively. 92 patients of PJI and 88 of aseptic failure were included. PJI was as defined by the Musculoskeletal Infection Society (MSIS). The content of IL-6 and IL-4 in synovial fluid of knee or hip were measured, and the areas under the receiver operating characteristic curve (ROC) and IL-6/IL-4 curve were analyzed to obtain a better diagnostic effect. The area under the curve of IL-6/IL-4 in synovial fluid of knee or hip was 0.9623, which was more accurate than ESR 0.5994 and C-reactive protein 0.6720. The optimal threshold of IL-6/IL-4 ratio was 382.10. Its sensitivity and specificity were 81.32% and 98.86%, respectively. The positive predictive value for the diagnosis of PJI was 98.91%. This study showed that the level of IL-6/IL-4 in synovial fluid of knee or hip could further improve the diagnostic accuracy for PJI.

Ultrasound evaluations and guided procedures of the painful joint arthroplasty

The purpose of this article is to describe the use of ultrasound for the diagnosis and treatment of painful joint arthroplasty. Ultrasound plays a crucial role in the diagnosis of the painful joint arthroplasty, especially given its unique dynamic capabilities, convenience, and high resolution. Ultrasound guidance is also instrumental for procedures in both diagnosing and in select cases, treating the painful joint arthroplasty. Topics to be discussed in this article include trends in arthroplasty placement, benefits of the use of ultrasound overall, and ultrasound evaluation of periprosthetic joint infections. We will also review the sonographic findings with dissociated/displaced components and adverse reaction to metallic debris including metallosis, trunnionosis, and metal-on-metal pseudotumors. Additionally, we will discuss ultrasound evaluation of tendon pathologies with arthroplasties, including dynamic maneuvers to evaluate for tendon impingement/snapping. Finally, we will cover ultrasound-guided joint arthroplasty injection indications and precautions. KEY POINTS: • Ultrasound is preferred over MRI in patients with joint arthroplasty and plays a crucial role in diagnosis, especially given its unique dynamic capabilities, convenience and high resolution. • It is especially beneficial for US-guided aspiration in periprosthetic joint infections; effectively used to evaluate periprosthetic fluid collections, facilitating differentiation between abscesses and aseptic collections, and tracking sinus tracts. • Recently, the diagnosis of periprosthetic joint infections has shifted focus to biomarkers in the periprosthetic fluid, specifically α-defensin, which has a high sensitivity and specificity for diagnosing infection. • Cutibacterium acnes is a major pathogen responsible for shoulder arthroplasty infections, often presenting with normal laboratory values and since slow growing, must be kept for a minimum of 14 days.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

Background

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

Methods

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

Results

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

Conclusion

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

The Development of Multiple Periprosthetic Joint Infections in Conjunction With Ibrutinib Therapy

Periprosthetic joint infections (PJI) can be subcategorized into acute postoperative infections, occurring within three months of implantation, and delayed onset infections, occurring after three months of implantation. PJIs can be caused by numerous infectious etiologies. Here, we describe a unique case of a patient with a history of bilateral shoulder and knee replacements over five years. The patient received a diagnosis of Waldenströms macroglobulinemia five years before her admission but deferred ibrutinib treatment until one year before her admission. We believe that the timeline coincides with the development of multiple PJIs secondary to ibrutinib therapy. The patient presented with bilateral shoulder and knee pain and swelling, following a flu-like illness that had resolved one year before the admission. Her joint symptoms did not subside along with the remaining flu-like symptoms. Initially, her symptoms served as clues to the diagnosis; however, the diagnosis was finally made and supported by joint aspiration. The patient was treated with vancomycin 1.25 g in sodium chloride 0.9% 250 mL intravenous piggyback every 24 hours for the treatment of PJI and oral daptomycin 500 mg daily for six weeks as prophylaxis for PJI. In conclusion, physicians need to consider the development of PJIs when prescribing immunosuppressive therapy, as well as an early diagnosis to prevent further complications.

Current and novel diagnostics for orthopedic implant biofilm infections: a review

Biofilm infections involving orthopedic implants are a global problem. They contribute to severe complications and mortality, as well as increased use of antibiotic treatments and development of antibiotic-resistant microorganisms. More than 1 million hip and knee arthroplasties are performed each year in the United States. These hard-to-treat infections lead to patient distress, increased morbidity, and high financial costs to both patients and healthcare systems. There is a need to improve the diagnosis of such biofilm infections to allow for earlier detection and treatment. Current diagnostics rely on clinical signs for infections such as loss of function, fever, rubor, patient history of the predisposing condition, persisting infection, failure of antibiotic treatment, and documentation of antibiotic failure. Below, we present a framework which outlines the data gaps in the conventional laboratory techniques used in clinical diagnostics; we also discuss promising novel diagnostic methods which are currently used solely in research. It is critical to assess these novel infection diagnostic techniques and address the data gaps and clinical hesitance preventing application in a clinical setting. Additionally, the combination of conventional and novel diagnostic technologies would streamline the diagnostic process of biofilm infections associated with orthopedic implants.

Perforated flexible catheters improve joint fluid aspiration in shoulder cadavers

A fluoroscopically controlled anterior approach in supine position is often used for arthrocentesis of the shoulder, but can lead to a high rate of dry aspirations. The aim of this study was to compare the aspiration performance of rigid needles and flexible catheters used with this approach. We hypothesized that a flexible catheter can significantly improve the amount of the obtained fluid. The glenohumeral joint of ten human cadaveric shoulder specimens were sequentially filled with 5, 10, 20 and 30 mL of contrast agent. For each volume the maximum aspirated amount of contrast agent with 4 different aspiration devices (20 gauge needle, 16 gauge needle, 16 gauge flexible catheter and 16 gauge perforated flexible catheter) were compared. All aspirations were done in supine cadaver position from anterior under fluoroscopic control. The aspirated amount of fluid was significantly higher using the 16 gauge perforated flexible catheter (p = 0.002–0.028) compared with all other devices when 5, 10 and 20 mL of contrast agent were in the joint. This perforated flexible catheter aspirated 80–96% of the available fluid while the standard 20 gauge needle aspirated 40–60%. Using a 16 gauge perforated flexible catheter in a supine anterior arthrocentesis technique results in aspiration of most of the fluid in human cadaveric shoulder specimens, while standard needles aspirate only about 50% of it. This can be clinically relevant when there is very little synovial fluid available and might reduce the number of insufficient aspirations.

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.

Ultrasound-Guided Periprosthetic Biopsy in Failed Total Hip Arthroplasty: A Novel Approach to Test Infection in Patients With Dry Joints

BACKGROUND

To diagnose periprosthetic joint infection (PJI) preoperatively, ultrasound-guided joint aspiration (US-JA) may not be performed when effusion is minimal or absent. We aimed to report and investigate the diagnostic performance of ultrasound-guided periprosthetic biopsy (US-PB) of synovial tissue to obtain joint samples in patients without fluid around the implants.

METHODS

One-hundred nine patients (55 men; mean age: 68 ± 13 years) with failed total hip arthroplasty (THA) who underwent revision surgery performed preoperative US-JA or US-PB to rule out PJI.

RESULTS

Sixty-nine of 109 patients had joint effusion and underwent US-JA, while the remaining 40 with dry joint required US-PB. Thirty-five of 109 patients (32.1%) had PJI, while 74/109 (67.9%) had aseptic THA failure. No immediate complications were observed in both groups. Technical success of US-PB was 100%, as the procedure was carried on as planned in all cases. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of US-JA were 52.2%, 97.8%, 92.3%, 80.3%, and 82.6%, while for US-PB, they were 41.7%, 100%, 100%, 80%, and 82.5%, respectively, with no significant difference (P = .779). Using the final diagnosis as reference standard, we observed a moderate agreement with both US-JA (k = 0.56) and US-PB (k = 0.50).

CONCLUSION

We present a novel US-guided technique to biopsy periprosthetic synovial tissue of failed THA to rule out PJI. We found similar diagnostic performance as compared with traditional US-JA. This supports future larger studies on this procedure that might be applied in patients without joint effusion.

Optimal microbiological sampling for the diagnosis of osteoarticular infection

Infection is a dire complication afflicting every field of orthopaedics and traumatology. If specific clinical, laboratory and imaging parameters are present, infection is often assumed even in the absence of microbiological confirmation. However, apart from confirming infection, knowing the exact infecting pathogen(s) and their antimicrobial susceptibility patterns is paramount to help guide treatment. Every effort should therefore be undertaken with that goal in mind.Not all microbiological findings carry the same relevance, and knowing exactly how and where a sample was collected is key. Several different sampling techniques are available, and one must be aware of both advantages and limitations. Microbiological sampling alternatives in some of the most common clinical scenarios such as native and prosthetic joint infections, osteomyelitis and fracture-related infections, spinal and diabetic foot infections will be discussed.Orthopaedic surgeons should also be aware of basic laboratory sample processing techniques as they have a direct impact on the way specimens should be dealt with and transported to the laboratory. Only by knowing these basic principles will surgeons be able to participate in the multidisciplinary discussion and decision making around how to interpret microbiological findings in each specific patient. Cite this article: EFORT Open Rev 2021;6:390-398. DOI: 10.1302/2058-5241.6.210011.

Diagnosis of knee prosthetic joint infection; aspiration and biopsy

BACKGROUND

Prosthetic joint infection (PJI) is a significant cause of morbidity and mortality following knee replacement surgery. The diagnosis can be challenging and is based on a combination of clinical suspicion, radiographic findings and also biochemical/ microbiological investigations. Our Aim was to review the role of aspiration and biopsy in the diagnosis of PJI in Total Knee Arthroplasty (TKA).

METHOD/RESULTS

Aspirated synovial fluid should be analysed by direct culture, via blood culture bottles, EDTA bottles for cell count and 'point of care' testing such as leucocyte esterase or alpha defensin. Synovial WCC and PMN cell percentage are important steps in diagnosis of both acute and chronic PJI. A minimum of 5 deep samples using a 5 clean instrument technique should be obtained and sent for tissue culture done either blind or arthroscopic. Formal fluoroscopic guided interface biopsy has also been described with excellent results. In a recent series of 86 TKRs preoperative arthroscopic biopsy group had a sensitivity of 100%, specificity of 94.7%, positive predictive value of 87.4% and a negative predictive value of 100%.

CONCLUSION

In the presence of clinical suspicion with raised biomarkers, it is recommended that aspiration +/- biopsy with synovial fluid testing is performed. Direct culture and cell count are recommended. 'Point of care tests' such as Leucocyte Esterase testing should be considered. Duration of culture, including pathogen and host factors, should be discussed with a local microbiology/ID department in the context of a formal multi-disciplinary team.

Poor performance of open incisional biopsy for the microbiological diagnosis of periprosthetic knee joint infection

The accurate preoperative diagnosis of periprosthetic joint infection (PJI) of total knee arthroplasty (TKA) can be difficult despite the use of a combination of serum and synovial markers. In such inconclusive cases, incisional open biopsy might be considered. This study investigates the usefulness of biopsies in patients with inconclusive diagnostic findings. We retrospectively identified 63 patients who underwent incisional biopsy for chronic PJI in the operation theatre following TKA revision between 2010 and 2018 after inconclusive preoperative diagnostics for PJI. In all cases, 5 independent biopsies were taken. Results from open biopsy for PJI were analyzed for diagnostic accuracy using the intraoperative results from following revision surgery as gold standard. 27 patients (43%) had a positive culture taken during biopsy. 15 cases (24%) met the diagnostic criteria for a chronic PJI. Most common organisms were Coagulase-negative staphylococci (67%) and Cutibacterium acnes (30%). Compared to the findings during revision surgery, biopsies showed a sensitivity of 47% and a specificity of 77% for PJI. Open incisional biopsy following inconclusive serum- and synovial diagnostics for low grade PJI may be considered for identification of microorganisms. Due to its low sensitivity and moderate specificity found in the present cohort, microbiological analysis should be combined with additional diagnostic markers and histological investigation.Level of Evidence. Retrospective cohort study (Level III).

Hip aspiration culture: analysing data from a single operator series investigating periprosthetic joint infection

Introduction: We undertook this study to know the sensitivity, specificity and post-test probabilities of hip aspiration when diagnosing periprosthetic hip infections. We also examined “dry tap” (injection with saline and aspiration) results and aspiration volumes. Methods: This is a retrospective cohort study of patients aspirated for suspected periprosthetic joint infection between July 2012 and October 2016. All aspirations were carried out by one trained surgical care practitioner (SCP). All aspirations followed an aseptic technique and fluoroscopic guidance. Aspiration was compared to tissue biopsy taken at revision. Aspiration volumes were analysed for comparison. Results: Between January 2012 and September 2016, 461 hip aspirations were performed by our SCP. Of these 125 progressed to revision. We calculated sensitivity 59 % (confidence interval (CI) 35 %–82 %) and specificity 94 % (CI 89 %–98 %). Pre-test probability for our cohort was 0.14. Positive post-test probability was 0.59 and negative post-test probability 0.06. Aspiration volume for infected (n=17) and non-infected (n=108) joints was compared and showed no significant difference. Dry taps were experienced five times; in each instance the dry tap agreed with the biopsy result. Conclusions: Our data show that hip aspiration culture is a highly specific investigation for diagnosing infection but that it is not sensitive. Aspiration volume showed no significant difference between infected and non-infected groups. Each time a joint was infiltrated with saline to achieve a result, the result matched tissue sampling.

Effects of different tissue specimen pretreatment methods on microbial culture results in the diagnosis of periprosthetic joint infection

Aims

Microbiological culture is a key element in the diagnosis of periprosthetic joint infection (PJI). However, cultures of periprosthetic tissue do not have optimal sensitivity. One of the main reasons for this is that microorganisms are not released from the tissues, either due to biofilm formation or intracellular persistence. This study aimed to optimize tissue pretreatment methods in order to improve detection of microorganisms.

Methods

From December 2017 to September 2019, patients undergoing revision arthroplasty in a single centre due to PJI and aseptic failure (AF) were included, with demographic data and laboratory test results recorded prospectively. Periprosthetic tissue samples were collected intraoperatively and assigned to tissue-mechanical homogenization (T-MH), tissue-manual milling (T-MM), tissue-dithiothreitol (T-DTT) treatment, tissue-sonication (T-S), and tissue-direct culture (T-D). The yield of the microbial cultures was then analyzed.

Results

A total of 46 patients were enrolled, including 28 patients in the PJI group and 18 patients in the AF group. In the PJI group, 23 cases had positive culture results via T-MH, 22 cases via T-DTT, 20 cases via T-S, 15 cases via T-MM, and 13 cases via T-D. Three cases under ongoing antibiotic treatment remained culture-negative. Five tissue samples provided the optimal yield. Any ongoing antibiotic treatment had a relevant influence on culture sensitivity, except for T-DTT.

Conclusion

T-MH had the highest sensitivity. Combining T-MH with T-DTT, which requires no special equipment, may effectively improve bacterial detection in PJI. A total of five periprosthetic tissue biopsies should be sampled in revision arthroplasty for optimal detection of PJI.

Cite this article: Bone Joint Res 2021;10(2):96–104.

Anatomic Landmark-Guided Hip Aspiration in the Diagnosis of Periprosthetic Joint Infection

Hip aspirations used to detect a periprosthetic joint infection (PJI) are usually performed under fluoroscopy or ultrasound. The aim of this study was to evaluate the results of simply using anatomic landmarks for aspiration and detecting PJI without the use of any complicated technologies. The authors retrospectively reviewed a total of 186 consecutive hip aspirations performed between April 2015 and December 2018. All patients were suspected to have infections after total hip arthroplasty. The procedures were performed with the patients in the supine position. The authors aimed to aspirate at the neck of the prosthesis. They located the y-axis of the puncture point approximately 2 to 3 cm lateral to the pulse of the femoral artery in the region of the inguinal ligament. The x-axis was estimated by using the pubic symphysis or greater trochanter according to an anteroposterior radiograph of the hip joint. The aspiration failure rate, incidence of complications, and culture results were recorded. The overall aspiration failure rate was 3.8% (7 of 186). No obvious complications related to aspiration were observed. The saline lavage and reaspiration rate was 45.3% (81 of 179) due to "dry taps." The sensitivity, specificity, positive predictive value, and negative predictive value of the remaining 169 patients with definite diagnoses were 0.781 (95% CI, 0.678-0.860), 0.939 (95% CI, 0.857-0.977), 0.931 (95% CI, 0.841-0.975), and 0.802 (95% CI, 0.706-0.874), respectively. Anatomic landmark-guided hip aspiration was a convenient method that could provide satisfactory detection of PJI. [Orthopedics. 2021;44(1):e85-e90.].

The 2018 New Definition of Periprosthetic Joint Infection is Valuable for Diagnosis of Persistent Infection at Reimplantation in Patients without Synovial Fluid

BACKGROUND

Diagnosis of persistent infection at reimplantation of 2-stage exchange revision is a challenging problem. The aim of our study is to evaluate the performance of the 2018 new definition and Musculoskeletal Infection Society (MSIS) criteria in determining the persistent infection at reimplantation in patients without synovial fluid.

METHODS

We retrospectively reviewed 150 patients who underwent 2-stage exchange revision from 2014 to 2018. Two models were used to define persistent infection-model 1: identical major criteria of the MSIS criteria and new definition and model 2: identical major criteria of 2 criteria and/or subsequent infection after reimplantation. The predictive accuracy of the new definition and MSIS criteria was compared by using receiver operating characteristic curves.

RESULTS

The receiver operating characteristic curves showed that the new definition had good performance in determining the persistent infection, with the area under the curve (AUC) of 0.871 in model 1 and 0.835 in model 2. The optimal threshold for aggregate scores in new definition was 4. The MSIS criteria had limited diagnostic value in both model 1 (AUC = 0.708) and model 2 (AUC = 0.664). In model 1, the sensitivity and specificity were 86.96% and 84.25% in new definition, and 47.83% and 93.70% in MSIS criteria in patients without synovial fluid. In model 2, the sensitivity and specificity were 78.57% and 85.25% in new definition, and 39.29% and 93.44% in MSIS criteria.

CONCLUSION

The 2018 new definition of PJI is valuable in the diagnosis of persistent infection, which can improve diagnostic accuracy compared with the MSIS criteria in patients without synovial fluid.

Septic Arthritis: An Evidence-Based Review of Diagnosis and Image-Guided Aspiration

OBJECTIVE. The purpose of this evidence-based review is to equip radiologists to discuss and interpret findings obtained with various imaging modalities, guide patient selection for percutaneous aspiration, and safely perform arthrocentesis to assess for infection in both native and prosthetic joints. CONCLUSION. Septic arthritis is an emergency that can lead to rapidly progressive, irreversible joint damage. Despite the urgency associated with this diagnosis, there remains a lack of consensus regarding many aspects of the management of native and periprosthetic joint infections.

Saline lavage after a "dry tap"

AIMS

In patients with a "dry" aspiration during the investigation of prosthetic joint infection (PJI), saline lavage is commonly used to obtain a sample for analysis. The aim of this study was to investigate prospectively the impact of saline lavage on synovial fluid analysis in revision arthroplasty.

METHODS

Patients undergoing revision hip (THA) or knee arthroplasty (TKA) for any septic or aseptic indication were enrolled. Intraoperatively, prior to arthrotomy, the maximum amount of fluid possible was aspirated to simulate a dry tap (pre-lavage) followed by the injection with 20 ml of normal saline and re-aspiration (post-lavage). Pre- and post-lavage synovial white blood cell (WBC) count, percent polymorphonuclear cells (%PMN), and cultures were compared.

RESULTS

A total of 78 patients had data available for analysis; 17 underwent revision THA and 61 underwent revision TKA. A total of 16 patients met modified Musculoskeletal Infection Society (MSIS) criteria for PJI. Pre- and post-lavage %PMNs were similar in septic patients (87% vs 85%) and aseptic patients (35% vs 39%). Pre- and post-lavage synovial fluid WBC count were far more disparate in septic (53,553 vs 8,275 WBCs) and aseptic (1,103 vs 268 WBCs) cohorts. At a cutoff of 80% PMN, the post-lavage aspirate had a sensitivity of 75% and specificity of 95%. At a cutoff of 3,000 WBCs, the post-lavage aspirate had a sensitivity of 63% and specificity of 98%. As the post-lavage synovial WBC count increased, the difference between pre- and post-lavage %PMN decreased (mean difference of 5% PMN in WBC < 3,000 vs mean difference 2% PMN in WBC > 3,000, p = 0.013). Of ten positive pre-lavage fluid cultures, only six remained positive post-lavage.

CONCLUSION

While saline lavage aspiration significantly lowered the synovial WBC count, the %PMN remained similar, particularly at WBC counts of > 3,000. These findings suggest that in patients with a dry-tap, the %PMN of a saline lavage aspiration has reasonable sensitivity (75%) for the detection of PJI. Cite this article: Bone Joint J 2020;102-B(6 Supple A):138-144.

Detecting the presence of bacterial RNA by polymerase chain reaction in low volumes of preoperatively aspirated synovial fluid from prosthetic joint infections

Aims

Preoperative diagnosis is important for revision surgery after prosthetic joint infection (PJI). The purpose of our study was to determine whether reverse transcription-quantitative polymerase chain reaction (RT-qPCR), which is used to detect bacterial ribosomal RNA (rRNA) preoperatively, can reveal PJI in low volumes of aspirated fluid.

Methods

We acquired joint fluid samples (JFSs) by preoperative aspiration from patients who were suspected of having a PJI and failed arthroplasty; patients with preoperative JFS volumes less than 5 ml were enrolled. RNA-based polymerase chain reaction (PCR) and bacterial culture were performed, and diagnostic efficiency was compared between the two methods.According to established Musculoskeletal Infection Society (MSIS) criteria, 21 of the 33 included patients were diagnosed with PJI.

Results

RNA-based PCR exhibited 57.1% sensitivity, 91.7% specificity, 69.7% accuracy, 92.3% positive predictive value, and 55.0% negative predictive value. The corresponding values for culture were 28.6%, 83.3%, 48.5%, 75.0%, and 40.0%, respectively. A significantly higher sensitivity was thus obtained with the PCR method versus the culture method.

Conclusion

In situations in which only a small JFS volume can be acquired, RNA-based PCR analysis increases the utility of preoperative puncture for patients who require revision surgery due to suspected PJI.

Cite this article:Bone Joint Res. 2020;9(5):219–224.

The accuracy of joint aspiration for the diagnosis of shoulder infections

BACKGROUND

Shoulder joint aspirations are frequently performed to rule out infection. In case of unsuccessful aspiration, physicians often augment the aspiration liquid by injecting saline solution.

METHODS

We performed shoulder joint aspirations by fluoroscopic assistance and analyzed the value of an additional saline solution irrigation in patients undergoing revision shoulder surgery. Native joints and post-fracture repair, post-arthroscopy, and post-arthroplasty shoulders were included. A minimum of 3 deep intraoperative tissue samples served as the microbiological gold standard.

RESULTS

We performed 106 aspirations occurring between 0 and 179 days before revision surgery. Among them, we could sample intra-articular liquid directly in 60 cases and after saline solution injection in 43 cases, whereas 3 cases remained unsuccessful. According to intraoperative samples, 24 shoulders were infected but only 10 of 24 (42%) yielded pathogens in the aspirate. Moreover, of the 43 saline solution-enforced irrigations, none revealed bacteria but 8 (17%) confirmed infection in intraoperative samples. Overall, the sensitivity, specificity, positive predictive value, and negative predictive value of presurgical aspirations were 33%, 98%, 80%, and 83%, respectively.

CONCLUSION

When surgical revision is planned, presurgical shoulder joint aspiration is not reliable to sufficiently exclude shoulder joint infection. Nevertheless, a positive aspiration finding can guide clinical decision making, so we propose to perform aspiration only if there is a clinically high index of suspicion for an infection. Irrigation after unsuccessful primary aspiration is futile.

Risk factors, diagnosis and management of prosthetic joint infection after total hip arthroplasty

Introduction: Although a relatively rare complication, the incidence and prevalence of prosthetic joint infection (PJI) is certainly rising. This is mainly due to the number of arthroplasties performed each year and our ability to capture more cases. There is currently no consensus in the optimal diagnosis and management of the infected total hip arthroplasty. Various management techniques have been described in literature.Areas covered: We discuss and summarize the literature in diagnosing prosthetic joint infection (PJI) including next-generation sequencing. An in-depth critical analysis of the biomarkers and the novel tests available in the market is reviewed including the evolving nature of the diagnostic criteria for PJI. The key issues in managing infected THA are identified.Expert commentary: The senior authors' expert opinion on diagnostic criteria is discussed. We also stress the importance of tissue/fluid analysis of microbiology and histology being key to diagnosis of PJI. The indications of one-stage versus two-stage revision arthroplasty is examined, including techniques for successful one-stage revision.

Can we rely on the combination of serological tests and frozen sections at the time of reimplantation for two-stage exchange hip arthroplasty in patients with a "dry tap"?

Purpose

The optimal timing of reimplantation of two-stage exchange arthroplasty for periprosthetic joint infection remains unknown. The purpose of the study was to (1) evaluate performance of combination of serum erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and frozen section in predicting persistent infection at the time of second-stage hip reimplantation and (2) compare accuracies of 5 and 10 polymorphonuclear neutrophils (PMNs) per high power field (HPF) as the threshold of frozen section.

Methods

We retrospectively reviewed 97 two-stage exchange hip arthroplasties from 2012–2016. Persistent infection at time of reimplantation was diagnosed using the Musculoskeletal Infection Society (MSIS) criteria. Two diagnostic models were developed. Model 1 utilized ESR, CRP, and > 5 PMNs/HPF on frozen section. Model 2 utilized ESR, CRP, and > 10 PMNs/HPF. Receiver operating characteristic (ROC) curves of the two models were generated, and areas under the curves (AUCs) were compared. A set of sensitivity analysis, using the Delphi-based consensus criteria for treatment success, was conducted to verify the accuracy of our models.

Results

The overall rate of infection at reimplantation was 14.4%. AUCs for models 1 and 2 were 0.709 (95% confidence interval [CI], 0.557–0.852) and 0.697 (95% CI, 0.529–0.847), respectively. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 57.1%, 88.0%, 44.4%, and 92.4%, respectively, in model 1 and 42.9%, 96.4%, 66.7%, and 90.9%, respectively, in model 2. Models 1 and 2 had no significant difference in predictive values (p = 0.821). Results remained robust in the sensitivity analysis.

Conclusions

This study reveals that the combination of serum ESR, CRP, and frozen section has limited diagnostic value in predicting persistent infection at reimplantation. Additionally, no significant difference in accuracies between 5 and 10 PMNs/HPF as the threshold of frozen section were found. There is a need for timely biomarkers with higher accuracy in diagnosing infection before reimplantation.

Saline Solution Lavage and Reaspiration for Culture with a Blood Culture System Is a Feasible Method for Diagnosing Periprosthetic Joint Infection in Patients with Insufficient Synovial Fluid

BACKGROUND

Culture is a key step for detecting periprosthetic joint infection (PJI) before surgery. However, using saline solution lavage and reaspiration in patients with insufficient synovial fluid remains controversial. The objective of this study was to evaluate this technique.

METHODS

This study included 286 aspirations performed by 1 surgeon in patients after total joint arthroplasty during the period of April 2015 to August 2018. If >1.0 mL of synovial fluid was obtained, then we directly used the fluid for culture. For cases in which ≤1.0 mL of synovial fluid was aspirated, 10 mL of saline solution was injected and the joint was reaspirated for culture. The samples were injected into 2 blood culture bottles for anaerobic bacterial culture and aerobic bacterial and fungal culture, and were inoculated for 14 days in a BACT/ALERT 3D blood culture system unless microorganisms were detected. A PJI diagnosis was determined on the basis of the modified Musculoskeletal Infection Society criteria.

RESULTS

Saline solution lavage and reaspiration were used in 82 cases (47 PJI cases and 35 non-PJI cases), while direct aspiration was used in 204 cases (99 PJI cases and 105 non-PJI cases). The overall rate for the use of saline solution lavage was 28.7% (82 of 286). Among knee cases, the saline solution lavage rate was 15.0% (21 of 140), and among hip cases, the rate was 41.8% (61 of 146). The overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of culture were 0.795 (95% confidence interval [CI], 0.720 to 0.857), 0.957 (95% CI, 0.909 to 0.984), 0.951 (95% CI, 0.896 to 0.982), and 0.817 (95% CI, 0.749 to 0.873); and for "dry tap" cases, they were 0.851 (95% CI, 0.717 to 0.938), 0.857 (95% CI, 0.697 to 0.952), 0.889 (95% CI, 0.760 to 0.963), and 0.811 (95% CI, 0.648 to 0.920), respectively.

CONCLUSIONS

Saline solution lavage and reaspiration for culture in patients with insufficient synovial fluid before surgery may be a sound practice.

LEVEL OF EVIDENCE

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

Diagnostic Accuracy of Serum, Synovial, and Tissue Testing for Chronic Periprosthetic Joint Infection After Hip and Knee Replacements: A Systematic Review

BACKGROUND

Chronic periprosthetic joint infection (PJI) is a devastating complication that can occur following total joint replacement. Patients with chronic PJI report a substantially lower quality of life and face a higher risk of short-term mortality. Establishing a diagnosis of chronic PJI is challenging because of conflicting guidelines, numerous tests, and limited evidence. Delays in diagnosing PJI are associated with poorer outcomes and morbid revision surgery. The purpose of this systematic review was to compare the diagnostic accuracy of serum, synovial, and tissue-based tests for chronic PJI.

METHODS

This review adheres to the Cochrane Collaboration's diagnostic test accuracy methods for evidence searching and syntheses. A detailed search of MEDLINE, Embase, the Cochrane Library, and the grey literature was performed to identify studies involving the diagnosis of chronic PJI in patients with hip or knee replacement. Eligible studies were assessed for quality and bias using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Meta-analyses were performed on tests with sufficient data points. Summary estimates and hierarchical summary receiver operating characteristic (HSROC) curves were obtained using a bivariate model.

RESULTS

A total of 12,616 citations were identified, and 203 studies met the inclusion criteria. Of these 203 studies, 170 had a high risk of bias. Eighty-three unique PJI diagnostic tests were identified, and 17 underwent meta-analyses. Laboratory-based synovial alpha-defensin tests and leukocyte esterase reagent (LER) strips (2+) had the best performance, followed by white blood-cell (WBC) count, measurement of synovial C-reactive protein (CRP) level, measurement of the polymorphonuclear neutrophil percentage (PMN%), and the alpha-defensin lateral flow test kit (Youden index ranging from 0.78 to 0.94). Tissue-based tests and 3 serum tests (measurement of interleukin-6 [IL-6] level, CRP level, and erythrocyte sedimentation rate [ESR]) had a Youden index between 0.61 to 0.75 but exhibited poorer performance compared with the synovial tests mentioned above.

CONCLUSIONS

The quality of the literature pertaining to chronic PJI diagnostic tests is heterogeneous, and the studies are at a high risk for bias. We believe that greater transparency and more complete reporting in studies of diagnostic test results should be mandated by peer-reviewed journals. The available literature suggests that several synovial fluid-based tests perform well for diagnosing chronic PJI and their use is recommended in the work-up of any suspected case of chronic PJI.

LEVEL OF EVIDENCE

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

Irrigation and debridement with chronic antibiotic suppression for the management of infected total knee arthroplasty

Aims

The results of irrigation and debridement with component retention (IDCR) in the treatment of acutely infected total knee arthroplasties (TKAs) have been variable. The aim of this study was to assess the outcome after IDCR when combined with chronic antibiotic suppression. We also evaluated survivorship free from subsequent infection, removal of the components, and death, as well as the risk factors for failure.

Patients and Methods

This was a single-centre retrospective review of 134 infected primary TKAs that were treated with IDCR. Infections within four weeks of the procedure were defined as acute postoperative infections, and those occurring more than four weeks after the procedure with symptoms for less than three weeks were defined as acute haematogenous infections. Patients were treated with intravenous antibiotics for four to six weeks, followed by chronic oral antibiotic suppression. Estimates of survival were made using a competing risk analysis. The mean follow-up was five years (2.1 to 13).

Results

The infection was an acute postoperative infection in 23 TKAs and an acute haematogenous infection in 111 TKAs. The incidence of subsequent infection was 36% in those with an acute postoperative infection and 33% in those with a haematogenous infection, five years postoperatively (p = 0.40). Age < 60 years increased the risk of subsequent infection (hazard ratio (HR) 2.4; p = 0.009) and removal of the components (HR 2.8; p = 0.007). Infection with a staphylococcal species increased the risk of subsequent infection (HR 3.6; p < 0.001), and removal of the components (HR 3.2; p = 0.002). Musculoskeletal Infection Society host type and local extremity grade, body mass index (BMI), the duration of symptoms, gender, and the presence of a monoblock tibial component had no significant effect on the outcome.

Conclusion

In a rigorously defined group of acute periprosthetic infections after TKA treated with IDCR and chronic antibiotic suppression, the infection-free survival at five years was 66%. The greatest risk factor for failure was an infection with a staphylococcal species, followed by age of < 60 years. Cite this article: Bone Joint J 2018;100-B:1471–76.