The role of biomarkers in the diagnosis of periprosthetic joint infection

Rapid multiplex micro-ELISA assay for simultaneous measurement of synovial biomarkers : a potential aid in diagnosing periprosthetic joint infection?

Aims

The diagnosis of periprosthetic joint infection (PJI) remains a challenge, as no single diagnostic test shows high diagnostic accuracy. Recently, the measurement of synovial biomarkers has shown promising results. The aim of this study was to present a novel multiplex micro-enzyme-linked immunosorbent assay (ELISA) method for the rapid and simultaneous measurement of alpha-defensin, interleukin (IL)-6, and calprotectin developed in a model buffer system and human spiked synovial fluid.

Methods

A microfluidics- and chemiluminescence-based multiplex micro-ELISA point-of-care testing system was employed for the rapid and simultaneous measurement of alpha-defensin, calprotectin, and IL-6 developed in a model buffer system and spiked human synovial fluid. Cut-off values of 1.56 µg/ml for alpha-defensin, 50 µg/ml for calprotectin, and 0.031 µg/ml for IL-6 were extracted from the literature as optimal cut-off values for the diagnosis of PJI, and were used for comparison.

Results

Limit of detection (LoD) was determined for each individual biomarker by means of calibration curves with serial dilutions in a model buffer system. LoDs of 0.008, 0.002, and 0.00014 µg/ml were determined for alpha-defensin, calprotectin, and IL-6, respectively. The spiked synovial fluid assay determined LoDs of 0.08, 0.31, and 0.004 µg/ml for alpha-defensin, calprotectin, and IL-6, respectively.

Conclusion

These findings highlight the proposed platform's unique features, including simultaneous measurement of three key synovial biomarkers, minimal sample volume requirements (5 to 50 µl), lower LoDs compared to conventional tests, and a short processing turnaround time of 22 minutes. Further validation studies are necessary to confirm its clinical utility.

Synovial fluid NMR-based metabolomics in septic and aseptic revision total knee arthroplasty: Implications on diagnosis and treatment

Periprosthetic joint infection (PJI) is one of the most challenging complications following total knee arthroplasty. Despite its importance, there is a paucity of reports in the literature regarding its pathogenesis. Recently, cellular metabolic reprogramming has been shown to play an important role in the progression and outcome of infectious diseases. Therefore, the aim of this study was to evaluate the metabolites composition of the synovial fluid from patients with PJI or aseptic failure of total knee arthroplasties. The synovial fluids from 21 patients scheduled for revision total knee arthroplasty (11 with the diagnosis of PJI and 10 with aseptic failures) were analyzed using 1D 1H NMR spectroscopy. Univariate and multivariate statistical analyzes were used to identify metabolites that were differentially abundant between those groups. A total of 28 metabolites were identified and five of them found to be differentially abundant between infected and non-infected synovial fluids. Lactate, acetate and 3-hydroxybutyrate were found to be in a higher concentration, and glucose and creatine were found reduced in the synovial fluid from PJI patients. Synovial fluid from patients with PJI exhibit a distinct metabolic profile, possibly reflecting metabolic adaptation that occurs in the infected periprosthetic microenvironment. Further research and studies are warranted to gain a broader insight into the metabolic pathways engaged by both pathogen and immune cells in the context of a PJI.

The James A. Rand Young Investigator's Award: Keeping It Simple: Are all Musculoskeletal Infection Society Tests Useful to Diagnose Periprosthetic Joint Infection?

BACKGROUND

Current data evaluating the clinical value and cost-effectiveness of advanced diagnostic tests for periprosthetic joint infection (PJI) diagnosis, including alpha-defensin and synovial C-reactive protein (CRP), is conflicting. This study aimed to evaluate the adequacy of preoperative and intraoperative PJI workups without utilizing these tests.

METHODS

This retrospective analysis identified all patients who underwent revision total knee or hip arthroplasty (rTKA and rTHA, respectively) for suspected PJI between 2018 and 2020 and had a minimum follow-up of 2 years. Perioperative data and lab results were collected, and cases were dichotomized based on whether they met the 2018 Musculoskeletal Infection Society (MSIS) criteria for PJI. In total, 204 rTKA and 158 rTHA cases suspected of PJI were reviewed.

RESULTS

Nearly 100% of the cases were categorized as "infected" for meeting the 2018 MSIS criteria without utilization of alpha-defensin or synovial CRP (rTKA: n = 193, 94.6%; rTHA: n = 156, 98.7%). Most cases were classified as PJI preoperatively by meeting either the major MSIS or the combinational minor MSIS criteria of traditional lab tests (rTKA: n = 177, 86.8%; rTHA: n = 143, 90.5%). A subset of cases was classified as PJI by meeting combinational preoperative and intraoperative MSIS criteria (rTKA: 16, 7.8%; rTHA: 13, 8.2%). Only 3.6% of all cases were considered "inconclusive" using preoperative and intraoperative data.

CONCLUSIONS

Given the high rate of cases satisfying PJI criteria during preoperative workup using our available tests, the synovial alpha-defensin and synovial CRP tests may not be necessary in the routine diagnostic workup of PJI. We suggest that the primary PJI workup process should be based on a stepwise algorithmic approach with the most economical testing necessary to determine a diagnosis first. The use of advanced, commercialized, and costly biomarkers should be utilized only when traditional testing is indeterminate.

Periprosthetic hip infection: Current concepts and the Wrightington experience

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

Can serum C-reactive protein determine the timing of reimplantation in two-stage revised arthroplasty for periprosthetic hip infection?

BACKGROUND

There are no definitive guides to determine the timing of reimplantation in two-stage revision total hip arthroplasties (THA) for periprosthetic joint infection (PJI). This study was to design to support a rational strategy of surgical treatment using serum C-reactive protein (CRP).

METHODS

We analyzed a total of 75 hips for PJI in the process of performing two-stage and multiple-stage revision THAs. CRP level was retrospectively evaluated every week and transformed to log2 (CRP) using a logistic regression model. Prosthesis survival from recurrent infection was determined by Kaplan-Meier analysis, using implant removal as the endpoint. Receiver operating characteristic curves were calculated using each log2 (CRP) to assess predictions of recurrent infection.

RESULTS

The 10-year survival rates were 85% (95% confidence interval, 76-95) and 100% for two-stage and multiple-stage revision THAs, respectively. Preoperatively, at 1, 2, 3, and 5 weeks, log2 (CRP) was not associated with recurrent infection. In failed two-stage revision THAs, log2 (CRP) at 3 weeks divided by that at 2 weeks showed a significant difference. Failure was associated with a ratio of >4.0 for the CRP level between 3 and 2 weeks.

CONCLUSION

In two-stage revision THA for PJI, patients with CRP elevation from 2 weeks to 3 weeks, especially 4-fold elevation, suggests the need for further debridement and postponement of second-staged reimplantation.

Acidity Is an Excellent Marker of Infection in Hip and Knee Arthroplasty

BACKGROUND

The diagnosis of joint replacement infection is a difficult clinical challenge that often occurs when the implant cannot be salvaged. We hypothesize that the pH value of synovial fluid could be an important indicator of the inflammatory status of the joint. However, in the literature, there is a lack of data on the pH changes in hip and knee joint replacements and their relation to infection and implant failure. In this study, we aimed to measure the pH levels of synovial fluid in patients with hip and knee joint replacements. We also investigated the potential of pH measurement as a diagnostic tool for joint replacement infection. In this study, we recorded the pH values to be 7.55 and 7.46 in patients where Pseudomonas aeruginosa was identified as the cause of the prosthetic joint infection. We attribute this to the different environments created by this specific bacterium. In other cases where the pH was higher, chronic mitigated infections were diagnosed, caused by strains of Staphylococcus aureus, Streptococcus agalactiase, and coagulase negative staphylococcus.

MATERIALS AND METHODS

In our cohort of 155 patients with implanted hip (THA; n = 85) or knee (TKA; n = 70) joint replacements, we conducted a prospective study with a pH measurement. Out of the whole cohort, 44 patients had confirmed joint replacement infection (28.4%) (44/155). In 111 patients, infection was ruled out (71.6%) (111/155). Joint replacement infection was classified according to the criteria of the Musculoskeletal Infection Society (MSIS) from 2018. Based on the measured values, we determined the cut-off level for the probability of ongoing inflammation. We also determined the sensitivity and specificity of the measurement.

RESULTS

The group of patients with infection (n = 44) had a significantly lower synovial fluid pH (pH = 6.98 ± 0.48) than the group of patients with no infection (n = 111, pH = 7.82 ± 0.29, p < 0.001). The corresponding median pH values were 7.08 for the patients with infection and 7.83 for the patients with no infection. When we determined the cut-off level of pH 7.4, the sensitivity level of infected replacements was 88.6%, and the specificity level of the measurement was 95.5%. The predictive value of a positive test was 88.6%, and the predictive value of a negative test was 95.5%.

CONCLUSIONS

Our results confirm that it is appropriate to include a pH measurement in the diagnostic spectrum of hip and knee replacements. This diagnostic approach has the potential to provide continuous in vivo feedback, facilitated by specialized biosensors. The advantage of this method is the future incorporation of a pH-detecting sensor into intelligent knee and hip replacements that will assess pH levels over time. By integrating these biosensors into intelligent implants, the early detection of joint replacement infections could be achieved, enhancing proactive intervention strategies.

Management of septic arthritis and prosthetic joint infection

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

Current relevance of biomarkers in diagnosis of periprosthetic joint infection: an update

With a significant rise in the number of arthroplasty procedures performed worldwide, the increasing revision burden posed by periprosthetic joint infection (PJI) is a matter of growing concern. In spite of various attempts to diagnose PJI, there are no defined tests that can be called a gold standard. Given the importance of early diagnosis in PJI, newer tests and biomarkers have been introduced to improve cumulative diagnostic accuracy. Novel biomarkers like calprotectin, lipocalcin, monocyte-to-lymphocyte ratio, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and platelet-to-mean platelet volume ratio have demonstrated a potential as diagnostic biomarkers for PJI. This article discusses the relevance of available and newly described diagnostic biomarkers to provide a perspective on the practical applicability in current medical practice, as well as highlights some recent advances in biomarkers for the diagnosis of PJI.

Joint fluid interleukin-6 combined with the neutral polymorphonuclear leukocyte ratio (PMN%) as a diagnostic index for chronic periprosthesis infection after arthroplasty

BACKGROUND

The diagnosis of periprosthetic joint infection (PJI) remains a challenge in clinical practice. Many novel serum and joint fluid biomarkers have important implications for the diagnosis of PJI. The presented study evaluated the value of joint fluid interleukin-6 (IL-6) combined with the neutral polymorphonuclear leukocyte (PMN%) ratio for chronic PJI diagnosis after arthroplasty.

MATERIALS AND METHODS

Sixty patients with chronic PJI or aseptic failure who underwent hip or knee revision from January 2018 to January 2020 in our department were included in this retrospective study. According to the 2013 MSIS diagnostic criteria, the 60 patients were divided into a PJI group and a non-PJI group (30 patients per group). We collected the joint fluid before surgery and determined the level of IL-6 and the PMN% by ELISA, and the differences between the two groups were compared. The diagnostic efficacy of joint fluid IL-6 combined with PMN% in chronic PJI was analyzed using a receiver operating characteristic curve (ROC curve).

RESULTS

The diagnosis of PJI using joint fluid IL-6 combined with PMN% presented an area under the curve of 0.983, which was more accurate than the areas under the curve for diagnosis using IL-6 and PMN% individually (0.901 and 0.914, respectively). The optimal threshold values for IL-6 and PMN% were 662.50 pg/ml and 51.09%, respectively. Their sensitivity and specificity were 96.67% and 93.33%, respectively. The accuracy of the diagnosis of PJI was 95.00%.

CONCLUSIONS

Joint fluid IL-6 combined with PMN% can be used as an auxiliary method to detect chronic infection around the prosthesis after hip/knee arthroplasty.

LEVEL OF EVIDENCE

Patients who underwent hip/knee revision at the First Hospital of Chongqing Medical University for periprosthetic infection or aseptic failure of the prosthesis after hip/knee arthroplasty from January 2018 to January 2020 were included. Trial registration This study was approved by the ethics committee of the First Hospital of Chongqing Medical University on September 26, 2018 (local ethics committee number: 20187101) and registered with the China Clinical Trials Registry (registration number: ChiCTR1800020440) with an approval date of December 29, 2018.

Evaluation of Synovial Calprotectin by Using a Lateral Flow Test for the Diagnosis of Prosthetic Joint Infections

The analysis of synovial fluid is a crucial step in the diagnosis of prosthetic joint infections (PJIs). Recently several studies illustrated the efficacy of synovial calprotectin in supporting the diagnosis of PJI. In this study, synovial calprotectin was analyzed by a commercial stool test to explore whether it might accurately predict PJIs. The synovial fluids of 55 patients were analyzed and calprotectin levels were compared to other synovial biomarkers of PJI. Of the 55 synovial flu-ids, 12 patients were diagnosed with PJI and 43 with an aseptic failure of the implant. Specificity, sensitivity, and AUC of calprotectin resulted in 0.944, 0.80, and 0.852 (95%CI: 0.971-1.00), respectively, with a set threshold of 529.5 µg/g. Calprotectin had a statistically relevant correlation with the synovial leucocyte counts (rs = 0.69, p < 0.001) and the percentage of synovial neutrophils (rs = 0.61, p < 0.001). From this analysis, it can be concluded that synovial calprotectin is a valuable biomarker that correlates with other established indicators of local infection, and the use of a commercial lateral flow stool test could be a cost-effective strategy delivering rapid and reliable results and supporting the diagnostic process of PJI.

Profiling the Immune Response to Periprosthetic Joint Infection and Non-Infectious Arthroplasty Failure

Arthroplasty failure is a major complication of joint replacement surgery. It can be caused by periprosthetic joint infection (PJI) or non-infectious etiologies, and often requires surgical intervention and (in select scenarios) resection and reimplantation of implanted devices. Fast and accurate diagnosis of PJI and non-infectious arthroplasty failure (NIAF) is critical to direct medical and surgical treatment; differentiation of PJI from NIAF may, however, be unclear in some cases. Traditional culture, nucleic acid amplification tests, metagenomic, and metatranscriptomic techniques for microbial detection have had success in differentiating the two entities, although microbiologically negative apparent PJI remains a challenge. Single host biomarkers or, alternatively, more advanced immune response profiling-based approaches may be applied to differentiate PJI from NIAF, overcoming limitations of microbial-based detection methods and possibly, especially with newer approaches, augmenting them. In this review, current approaches to arthroplasty failure diagnosis are briefly overviewed, followed by a review of host-based approaches for differentiation of PJI from NIAF, including exciting futuristic combinational multi-omics methodologies that may both detect pathogens and assess biological responses, illuminating causes of arthroplasty failure.

Long Pentraxin 3 as a New Biomarker for Diagnosis of Hip and Knee Periprosthetic Joint Infections

BACKGROUND

Preoperative diagnosis of periprosthetic joint infections (PJIs) poses an unmet clinical challenge. The long pentraxin PTX3 is a component of the innate immune system involved in infection immunity. This study evaluated the potential of synovial and plasmatic PTX3 in the diagnosis of hip and knee PJIs.

METHODS

Consecutive total hip and knee arthroplasty (THA/TKA) revisions were prospectively included and classified as septic or aseptic according to the European Bone and Joint Infection Society (EBJIS) and Musculoskeletal Infection Society (MSIS) criteria. The concentration of PTX3 in plasma and synovial fluid samples was measured with ELISA. The AUC, threshold value, sensitivity, specificity, and positive and negative likelihood ratios were calculated using the ROC (receiver operating characteristic) curve method.

RESULTS

The study population included 128 patients (94 THAs; 34 TKAs). The AUC of the synovial PTX3 based on EBJIS criteria was 0.85 (p < 0.0001), with a sensitivity of 81.13% and a specificity of 93.33%. The AUC based on MSIS criteria was 0.95 (p < 0.001), with a sensitivity of 91.43% and a specificity of 89.25%. Plasmatic PTX3 failed to discriminate infected from non-infected patients.

CONCLUSIONS

Synovial PTX3 demonstrated an excellent diagnostic potential in hip and knee PJIs, with a very high specificity irrespective of the diagnostic criteria for PJI.

A 92 protein inflammation panel performed on sonicate fluid differentiates periprosthetic joint infection from non-infectious causes of arthroplasty failure

Periprosthetic joint infection (PJI) is a major complication of total joint arthroplasty, typically necessitating surgical intervention and prolonged antimicrobial therapy. Currently, there is no perfect assay for PJI diagnosis. Proteomic profiling of sonicate fluid has the potential to differentiate PJI from non-infectious arthroplasty failure (NIAF) and possibly clinical subsets of PJI and/or NIAF. In this study, 200 sonicate fluid samples, including 90 from subjects with NIAF (23 aseptic loosening, 35 instability, 10 stiffness, five osteolysis, and 17 other) and 110 from subjects with PJI (40 Staphylococcus aureus, 40 Staphylococcus epidermidis, 10 Staphylococcus lugdunensis, 10 Streptococcus agalactiae, and 10 Enterococcus faecalis) were analyzed by proximity extension assay using the 92 protein Inflammation Panel from Olink Proteomics. Thirty-seven of the 92 proteins examined, including CCL20, OSM, EN-RAGE, IL8, and IL6, were differentially expressed in PJI versus NIAF sonicate fluid samples, with none of the 92 proteins differentially expressed between staphylococcal versus non-staphylococcal PJI, nor between the different types of NIAF studied. IL-17A and CCL11 were differentially expressed between PJI caused by different bacterial species, with IL-17A detected at higher levels in S. aureus compared to S. epidermidis and S. lugdunensis PJI, and CCL11 detected at higher levels in S. epidermidis compared to S. aureus and S. agalactiae PJI. Receiver operative characteristic curve analysis identified individual proteins and combinations of proteins that could differentiate PJI from NIAF. Overall, proteomic profiling using this small protein panel was able to differentiate between PJI and NIAF sonicate samples and provide a better understanding of the immune response during arthroplasty failure.

Diagnostic Utility of Synovial Fluid Cell Counts and CRP in Pediatric Knee Arthritis: A 10-Year Monocentric, Retrospective Study

Background: Orthopedic surgeons often use the intra-articular white blood counts (WBCs) and the percentage of polymorphonuclear cells (PMN) in the diagnosis of an acute swollen and painful knee joint in children. Today, there is no established threshold for the synovial WBC, and their differentiation, as indicative of native joint knee bacterial arthritis. We determine the sensitivity and specificity of synovial WBCs and PMN percentages in the prediction of a community-acquired, acute bacterial native joint septic arthritis (SA) in the pediatric population. Methods: A retrospective study on healthy children 0–16 years of age who underwent knee joint aspiration for a community-acquired, acute irritable knee effusion in our tertiary-care children’s hospital between May 2009 and April 2019 was conducted. We divided the study population into two groups according to the detection of bacterial arthritis in the synovial fluid (bacterial arthritis versus its absence) and compared the intra-articular leukocyte and C-reactive protein (CRP) levels. Results: Overall, we found a statistically significant difference regarding the total CRP (p = 0.017), leukocyte or PMN counts (p ≤ 0.001 in favor of a bacterial arthritis). In contrast, the percentage of the neutrophils was not determinant for the later confirmation of bacterial pathogens, and we were unable to establish diagnostically determining minimal thresholds of the intra-articular CRP and leukocyte levels. Conclusions: This pilot study suggests that either the leukocyte or PMN counts may be associated with a bacterial origin of knee arthritis in children. We plan a larger prospective interventional study in the future to confirm these findings including the investigation of other joint aspirate biomarkers.

The autoclaving and re-implantation of an infected prosthesis as a spacer during resection knee arthroplasty: a systematic review

BACKGROUND

Hofmann et al., in 1995, first described an articulating spacer made by cleaning and autoclaving the original femoral component, which is then re-implanted with a new tibial polyethylene. This systematic review aims to assess the state of existing evidence on the intraoperative autoclaving and re-use of an infected prosthesis, as a spacer, during a two-stage revision following Periprosthetic Joint Infections (PJI).

METHODS

A systematic review was conducted with methods described in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. OVID-MEDLINE®, EMBASE, Cochrane Library, SCOPUS, Web of Science, Google Scholar and PubMed were searched from 1995 to April 2020 to identify relevant studies.

RESULTS

Fourteen studies were included in this systematic review: two prospective case series; six retrospective comparative studies and six retrospective case series. The reviewed studies included 567 patients (571 knees): 394 patients treated with autoclaved components and 173 with a spacer made of new components. The cumulative re-infection rate in patients treated with re-used autoclaved components was 13.7% (54 re-infections in 394 patients), whereas in control patients the re-infection rate was 13.3% (23 re-infections in 173 patients). The final Range of Movement in patients treated using the autoclaved components as a spacer, compared with patients receiving static spacers, was significantly higher in three out of four comparative studies.

CONCLUSION

There is a moderate level of evidence that the intraoperative autoclaving and re-use of an infected prosthesis as a spacer, during a knee resection arthroplasty, is an effective procedure in the management of knee PJI.

Activated polymorphonuclear derived extracellular vesicles are potential biomarkers of periprosthetic joint infection

Background

Extracellular vesicles (EVs) are considered as crucial players in a wide variety of biological processes. Although their importance in joint diseases or infections has been shown by numerous studies, much less is known about their function in periprosthetic joint infection (PJI). Our aim was to investigate activated polymorphonuclear (PMN)-derived synovial EVs in patients with PJI.

Questions/Purposes

(1) Is there a difference in the number and size of extracellular vesicles between periprosthetic joint aspirates of patients with PJI and aseptic loosening? (2) Are these vesicles morphologically different in the two groups? (3) Are there activated PMN-derived EVs in septic samples evaluated by flow cytometry after CD177 labelling? (4) Is there a difference in the protein composition carried by septic and aseptic vesicles?

Methods

Thirty-four patients (n = 34) were enrolled into our investigation, 17 with PJI and 17 with aseptic prosthesis loosening. Periprosthetic joint fluid was aspirated and EVs were separated. Samples were analysed by nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM) and flow cytometry (after Annexin V and CD177 labelling). The protein content of the EVs was studied by mass spectrometry (MS).

Results

NTA showed particle size distribution in both groups between 150 nm and 450 nm. The concentration of EVs was significantly higher in the septic samples (p = 0.0105) and showed a different size pattern as compared to the aseptic ones. The vesicular nature of the particles was confirmed by TEM and differential detergent lysis. In the septic group, FC analysis showed a significantly increased event number both after single and double labelling with fluorochrome conjugated Annexin V (p = 0.046) and Annexin V and anti-CD177 (p = 0.0105), respectively. MS detected a significant difference in the abundance of lactotransferrin (p = 0.00646), myeloperoxidase (p = 0.01061), lysozyme C (p = 0.04687), annexin A6 (p = 0.03921) and alpha-2-HS-glycoprotein (p = 0.03146) between the studied groups.

Conclusions

An increased number of activated PMN derived EVs were detected in the synovial fluid of PJI patients with a characteristic size distribution and a specific protein composition. The activated PMNs-derived extracellular vesicles can be potential biomarkers of PJI.

Serum calprotectin: a potential biomarker to diagnose chronic prosthetic joint infection after total hip or knee arthroplasty

The preoperative detection of prosthetic joint infection (PJI) prior to revision of total hip or knee arthroplasty is still a challenge. Serum Calprotectin (CP) is a heterodimer of two calcium-binding proteins present in the cytoplasm of neutrophils that is released in inflammatory processes and infections. The objective of this study is to determine the reliability of serum CP in the diagnosis of chronic PJI. 81 patients (40 women, 41 men) that presented a potential indication for revision arthroplasty of the hip (THA; n = 18) or knee (TKA, n = 63) at a single institution were prospectively evaluated. The joints were diagnosed as chronically infected or aseptic based on the musculoskeletal infection society (MSIS) criteria of 2018. Receiver operating characteristics and the Youden's index were used to define an ideal cutoff value. The median serum CP level was significantly higher in the group with chronic PJI (15,120 vs. 4980 ng/ml; p < 0.001) compared to the aseptic cases. The calculated optimal cut-off value was 9910 ng/ml (AUC 0.899, 95% CI 0.830-0.968) with a specificity of 91% and sensitivity of 81%. The present investigation suggests that serum CP has a high specificity and good sensitivity to diagnose chronic PJI after TJA of the knee or hip.

The combined measurement of synovial markers in the diagnosis of periprosthetic joint infection

INTRODUCTION

Currently there is no single test for periprosthetic joint infection (PJI) that demonstrates an acceptable level of sensitivity. The aim of this pilot study was to identify a combination of biomarkers that could exclude periprosthetic infection prior to revision surgery in hip and knee arthroplasty. This would help in equivocal cases of PJI, such as those with low-virulence organisms, chronic low-grade infection or 'aseptic' loosening. Current research has focused on measuring the levels of biomarkers in the patient's synovial fluid, and these can be combined to improve accuracy.

METHODS

We selected synovial white cell count (SF-WCC) and C-reactive protein (SF-CRP), as they demonstrated an acceptable level of sensitivity and specificity which could be measured using existing equipment. One hundred and sixty-one synovial fluid samples from 134 patients were collected and analysed prospectively using calculated cut-off values of 10mg/l for SF-CRP and 3,000×10⁶/l for SF-WCC. Samples were deemed positive for infection when either of the SF-CRP or SF-WCC values were above the cut-off.

RESULTS

The combined test demonstrated a sensitivity greater than 98.5% and specificity above 80% in all samples analysed or looked at separately for total hip replacement and total knee replacement infections. All ten aspirates taken from chronically infected joints tested positive.

CONCLUSIONS

The combination of SF-CRP and SF-WCC measurement has been shown to have high sensitivity of over 99% in detecting both acute and chronic PJI in both hip and knee arthroplasty. This ability of the test to exclude infection with a high degree of certainty will help in preoperative planning of PJIs.

Analysis of Failed Two-Stage Procedures with Resection Arthroplasty as the First Stage in Periprosthetic Hip Joint Infections

Resection arthroplasty can be performed as the first stage of a two-stage procedure in some patients with severe periprosthetic hip joint infections with poor bone stock. This retrospective study aimed to evaluate factors associated with the subsequent failure or success of these patients. Between 2011 and 2020; in 61 (26.4%) of 231 patients who underwent a two-stage protocol of periprosthetic hip joint infections; no spacer was used in the first stage. The minimum follow-up period was 12 months. Patient's demographics and various infection risk factors were analyzed. In total, 37/61 (60.7%) patients underwent a successful reimplantation, and four patients died within the follow-up period. Patients within the failure group had a significantly higher Charlson comorbidity index (p = 0.002); number of operations prior to resection arthroplasty (p = 0.022) and were older (p = 0.018). Failure was also associated with the presence of a positive culture in the first- and second-stage procedures (p = 0.012). Additional risk factors were persistent high postoperative CRP values and the requirement of a negative-pressure wound therapy (p ≤ 0.05). In conclusion, multiple factors need to be evaluated when trying to predict the outcome of patients undergoing resection arthroplasty as the first stage of a two-stage procedure in patients with challenging periprosthetic hip joint infections.

Synovial fluid pH sensor for early detection of prosthetic hip infections

We describe an implantable sensor developed to measure synovial fluid pH for noninvasive early detection and monitoring of hip infections using standard-of-care plain radiography. The sensor was made of a pH responsive polyacrylic acid-based hydrogel, which expands at high pH and contracts at low pH. A radiodense tantalum bead and a tungsten wire were embedded in the two ends of the hydrogel in order to monitor the change in length of the hydrogel sensor in response to pH via plain radiography. The effective pKa of the hydrogel-based pH sensor was 5.6 with a sensitivity of 3 mm/pH unit between pH 4 and 8. The sensor showed a linear response and reversibility in the physiologically relevant pH range of pH 6.5 and 7.5 in both buffer and bovine synovial fluid solutions with a 30-minute time constant. The sensor was attached to an explanted prosthetic hip and the pH response determined from the X-ray images by measuring the length between the tantalum bead and the radiopaque wire. Therefore, the developed sensor would enable noninvasive detection and studying of implant hip infection using plain radiography.

Combined serum and synovial C-reactive protein tests: a valuable adjunct to the diagnosis of chronic prosthetic joint infection

Background

Diagnosis of periprosthetic joint infection (PJI), especially chronic PJI, is very confusing and challenging. The value of C-reactive protein (CRP) in infectious diseases has been recognized, but the diagnostic value of CRP in chronic PJI is unknown. Our aim was to investigate the diagnostic value of synovial CRP in chronic PJI and to explore the role of combined serum and synovial CRP in distinguishing chronic PJI from aseptic failure after knee and hip arthroplasties.

Methods

We prospectively enrolled patients scheduled to have a revision surgery for chronic PJI or aseptic loosening from January 2019 to December 2020, in which synovial CRP was additionally measured along with routine preoperative diagnostic serum ((ESR, CRP) and synovial (PMN%) biomarkers. The receiver operating characteristic (ROC) curves and area under the curve (AUC) were analyzed for each biomarker to determine diagnostic efficacy.

Results

There were no statistically significant differences between the infection (n = 39) and aseptic (n = 58) groups, including 61 hips and 36 knees. The synovial CRP levels were significantly higher in the infection group than in the aseptic group (median: 9.93 mg/l vs 3.58 mg/l; p < .001). The optimal cut-off value for detecting chronic PJI of Synovial fluid (SF) CRP was of 7.26 mg/l with a sensitivity of 84.62%, a specificity of 93.10%. The combined model I (Serum CRP > 10.2 mg/l OR SF CRP > 7.26 mg/l) had a negative predictive value (NPV) of 96.67%, and a sensitivity of 97.44%. The combined model II (Serum CRP > 10.2 mg/l AND Synovial CRP > 7.26 mg/l) led to a specificity of 1, and a positive predictive value (PPV) of 1.

Conclusions

The present study demonstrated that the combination of serum and synovial CRP can be used as an adjunct to the diagnosis of chronic PJI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04545-6.

Serum and Synovial Biomarkers for the Diagnosis of Implant-Associated Infection After Orthopedic Surgery

Implant-associated infection is one of the most devastating complications following orthopedic surgery. Early identification is crucial for treatment. Currently, however, a reliable diagnostic tool is lacking, partly due to disparate bacteria colonies (virulent vs non-virulent), difficulty in distinguishing infection from inflammatory disease, and highly diverse diagnostic thresholds and testing methods. Given the importance of biomarkers in the initial screening for the infection, an extensive effort has been made to develop serum and synovial biomarkers. In this review, the authors summarize the results from the most relevant studies to provide comprehensive information on biomarkers for the diagnosis of implant-associated infection. [Orthopedics. 2021;44(2):e158-e166.].

Globulin, the albumin-to-globulin ratio, and fibrinogen perform well in the diagnosis of Periprosthetic joint infection

Background

Although periprosthetic joint infection (PJI) is a severe complication of total joint arthroplasty (TJA), the diagnosis of PJI remains challenging. Albumin (ALB), globulin (GLB), the albumin-to-globulin ratio (AGR), and fibrinogen could be indicators of the body’s inflammatory state. This study aimed to compare the diagnostic accuracy of these biomarkers with that of other inflammatory biomarkers in PJI patients.

Methods

We conducted a retrospective cohort study that included a consecutive series of patients undergoing debridement antibiotic irrigation and implant retention (DAIR), one-stage or the first stage of a two-stage revision total knee arthroplasty (TKA) or total hip arthroplasty (THA) for acute (n = 31) or chronic (n = 51) PJI, or revision TKA or THA for aseptic failures (n = 139) between January 2017 and December 2019 in our hospital. The 2013 criteria of the Musculoskeletal Infection Society (2013 MSIS) were used as the reference standard for the diagnosis of PJI. The preoperative ALB, GLB, AGR, fibrinogen, D-dimer, platelet count, fibrin degradation product (FDP), platelet-to-lymphocyte (PLR), platelet count to mean platelet volume ratio (PVR), neutrophil-to-lymphocyte ratio (NLR), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels were assessed. The receiver operating characteristic curve (ROC), sensitivity, and specificity were utilized to compare different biomarkers.

Results

Compared with the aseptic patients, the GLB, D-dimer, fibrinogen, FDP, platelet count, PVR, PLR, NLR, ESR, and CRP levels of PJI patients were significantly higher (P < 0.01); however, the ALB and AGR levels were significantly lower (P < 0.01). The area under the curve (AUC), sensitivity and specificity were 0.774, 67.50, 77.54% for ALB; 0.820, 57.50, 89.86% for GLB; 0.845, 66.25, 93.48% for AGR; 0.832, 78.48, 78.95% for fibrinogen; 0.877, 81.48, 85.07% for ESR; 0.909, 83.95, 88.89% for CRP; 0.683, 55.22, 75.83% for D-dimer; 0.664, 38.81, 88.33% for FDP; 0.678, 52.44, 79.86% for platelet count; 0.707, 48.78, 86.33% for PVR; 0.700, 51.22, 80.58% for PLR; and 0.678, 52.44, 81.30% for NLR, respectively. In the clinic, GLB, AGR and fibrinogen could be used for diagnosis of patients suspected of having PJI.

Conclusion

Our study demonstrated that GLB, AGR, and fibrinogen were promising biomarkers in the diagnosis of PJI.

Diagnostic accuracy of the BJI InoPlex™ (Diaxonhit) immunoassay on blood samples for periprosthetic joint infection in complex microbiological situations. Preliminary results of 24 cases in a French Reference Center for Complex Bone and Joint Infection (CRIOAC)

BACKGROUND

While joint aspiration is the benchmark for diagnosing periprosthetic joint infections (PJI), the results can be flawed because certain bacteria are difficult to culture, the patient is on concurrent antibiotic therapy or in some cases, repeated joint aspirations confer conflicting results. The BJI InoPlex™ (Diaxonhit) is a multiplex ELISA (Enzyme Linked Immunosorbent Assay) that measures the immune response (presence of specific IgG) to certain bacterial species from three families: Staphylococcus (8 antigens) epidermidis, aureus and lugdunensis, Streptococcus B (4 antigens) and Cutibacterium acnes (4 antigens). This assay is done with peripherally collected blood. However, there are few published studies about this assay, especially if the microbiological diagnosis is in doubt in cases of suspected chronic PJI. This led us to conduct a retrospective study in a French tertiary care center to determine 1) the sensitivity and specificity of the BJI InoPlex™, 2) its positive (PPV) and negative predictive value (NPV) and 3) what causes diagnostic errors.

HYPOTHESIS

The BJI InoPlex has a sensitivity/specificity and PPV/NPV above 75%.

MATERIALS AND METHODS

The BJI InoPlex was used 24 times on 24 patients between January 2016 and January 2017 in scenarios where the microbiological diagnosis was difficult: 1 with on-going antibiotic therapy, 13 conflicting repeat joint aspirations, 10 negative cultures with history of infection and/or clinical evidence of a PJI. The series consisted of 11 hip arthroplasty and 13 knee arthroplasty cases. The results of the BJI InoPlex test were compared to the MusculoSkeletal Infection Society (MSIS) the criteria for a joint infection.

RESULTS

For the bacterial species covered by the test, the sensitivity of the BJI InoPlex for diagnosing a chronic PJI based on the 2018 MSIS criteria was 50%, the specificity was 56%, the PPV was 36% and the NPV was 69%.

DISCUSSION

While innovative, minimally invasive, and rapid (results in a few hours), the BJI InoPlex does not provide an effective diagnosis of chronic PJI in complex microbiological situations. In this study, we used the test in the most difficult situations possible and on a small number of patients, which may explain why the results were not as good as in other studies. Its current performance and cost mean there is no role for it in our algorithm for treating patients with a suspected PJI, contrary to other biomarkers. Its spectrum must include other bacterial strains involved in chronic PJI. Knowledge of the specific infectious agent increases its diagnostic value, it could be used to monitor the outcome of a PJI, although other studies would be needed to support this use.

LEVEL OF EVIDENCE

IV-Retrospective diagnostic study.

The Expanding Role of Biomarkers in Diagnosing Infection in Total Joint Arthroplasty: A Review of Current Literature

Consistent diagnosis of periprosthetic infection in total joint arthroplasty continues to elude the orthopedic surgeon because no gold standard test exists. Therefore clinicians must rely on a combination of tests to help aid the diagnosis. The expanding role of biomarkers has shown promising results to more accurately diagnose an infection when combined with clinical suspicion and bacterial culture testing. This paper reviews the diagnostic capabilities of the most current serum and synovial biomarkers as well as next generation sequencing in the setting of periprosthetic joint infection. Future research and high-powered studies will be necessary to determine sensitivity and specificity of each biomarker.

Synovial fluid IL-1β appears useful for the diagnosis of chronic periprosthetic joint infection

PURPOSE

The purpose of this study was to investigate the role of synovial fluid interleukin (IL)-1β in diagnosing chronic periprosthetic joint infection (PJI) and to identify the optimal threshold of synovial fluid IL-1β for differentiating chronic PJI from aseptic failure after knee and hip arthroplasties.

METHODS

Between January 2019 and December 2019, we prospectively included patients scheduled to have a revision surgery for chronic PJI or aseptic failure after total joint arthroplasty. Then, synovial IL-1β was additionally measured along with routine preoperative diagnostic serum and synovial biomarkers. The receiver operating characteristic (ROC) curves and area under the curve (AUC) were analyzed for each biomarker to determine diagnostic efficacy.

RESULTS

Of the 93 patients included, their demographic data were not found to be statistically significant. The median synovial IL-1β levels were significantly higher in the chronic PJI group than in the aseptic group (894.73 pg/mL vs. 34.49 pg/mL, P<0.01). The AUC for synovial fluid IL-1β was 0.991, which was higher than serum ESR (0.627) and CRP (0.712). The optimal threshold value for detecting chronic PJI of synovial IL-1β was 312.7 pg/mL, with a sensitivity of 97.3% and a specificity of 94.64%. And the combined measurement of synovial fluid IL-1β and synovial fluid PMN% can led to a specificity of 1, and a negative predictive value (NPV) of 1.

CONCLUSIONS

The present study demonstrated that synovial fluid IL-1β is a valuable biomarker for detection of chronic PJI. The combination of synovial fluid IL-1β and PMN% led to an improvement in specificity compared with evaluation of each single index.

TRIAL REGISTRATION

This study was prospectively registered on the Chinese Clinical Trial Registry (a non-profit organization, established according to both the WHO International Clinical Trials Register Platform Standard and Ottawa Group Standard), and the registering number was ChiCTR1800020440 . Registered on December 29, 2018.

Synovial fluid interleukin-6 is not superior to cell count and differential in the detection of periprosthetic joint infection

Aims

Synovial fluid white blood cell (WBC) count and percentage of polymorphonuclear cells (%PMN) are elevated at periprosthetic joint infection (PJI). Leucocytes produce different interleukins (IL), including IL-6, so we hypothesized that synovial fluid IL-6 could be a more accurate predictor of PJI than synovial fluid WBC count and %PMN. The main aim of our study was to compare the predictive performance of all three diagnostic tests in the detection of PJI.

Methods

Patients undergoing total hip or knee revision surgery were included. In the perioperative assessment phase, synovial fluid WBC count, %PMN, and IL-6 concentration were measured. Patients were labeled as positive or negative according to the predefined cut-off values for IL-6 and WBC count with %PMN. Intraoperative samples for microbiological and histopathological analysis were obtained. PJI was defined as the presence of sinus tract, inflammation in histopathological samples, and growth of the same microorganism in a minimum of two or more samples out of at least four taken.

Results

In total, 49 joints in 48 patients (mean age 68 years (SD 10; 26 females (54%), 25 knees (51%)) were included. Of these 11 joints (22%) were infected. The synovial fluid WBC count and %PMN predicted PJI with sensitivity, specificity, accuracy, PPV, and NPV of 82%, 97%, 94%, 90%, and 95%, respectively. Synovial fluid IL-6 predicted PJI with sensitivity, specificity, accuracy, PPV, and NPV of 73%, 95%, 90%, 80%, and 92%, respectively. A comparison of predictive performance indicated a strong agreement between tests.

Conclusions

Synovial fluid IL-6 is not superior to synovial fluid WBC count and %PMN in detecting PJI.

Level of Evidence: Therapeutic Level II

Cite this article: Bone Jt Open 2020;1-12:737–742.

Analysis of synovial biomarkers with a multiplex protein microarray in patients with PJI undergoing revision arthroplasty of the hip or knee joint

INTRODUCTION

Diagnosing a (low-grade) periprosthetic joint infection (PJI) after hip or knee arthroplasty remains a diagnostic challenge. The aim of this study was to evaluate the utility of using a novel multiplex protein microarray system for synovial biomarkers in determining PJI in patients undergoing revision knee or hip arthroplasty.

MATERIALS AND METHODS

The individual synovial fluid levels of 12 cytokines (IL-1b, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-17, GM-CSF, TNF-α, and INF-γ) were analysed with a novel multiplex protein microarray system in 32 patients undergoing revision hip (n = 22) or knee (n = 10) arthroplasty. Cases were classified into septic and aseptic groups on basis of pre- and interoperative findings: [PJI (n = 14) vs. non-PJI (n = 18)]. Receiver operator characteristic (ROC) curves were calculated to assess the discriminatory strength of the individual parameters. A multiple regression model was used to determine the utility of using a combination of the tested cytokines to determine the infection status.

RESULTS

The levels of all of the evaluated cytokines were significantly elevated in the PJI-group. Best sensitivity and specificity were found for IL-6, followed by IL-1b, IL-10, and IL-17. The multiple regression models revealed a combination of IL-2, IL-4, IL-5, IL6, lL-12, and GM-CSF to be associated with the best sensitivity (100%) and specificity (88.9%) for a cut-off value of 0.41, with a likelihood ratio of 9.0.

CONCLUSION

Analysis of individual synovial fluid cytokine levels showed both high sensitivity and high specificity in diagnosing PJI. A combined model using several cytokines showed even higher sensitivity and specificity in diagnosing PJI and could thus be a useful predictive tool to determine the probability of PJI in patients with a painful prosthesis.

LEVEL OF EVIDENCE

Diagnostic IV.

Increased Diagnostic Certainty of Periprosthetic Joint Infections by Combining Microbiological Results with Histopathological Samples Gained via a Minimally Invasive Punching Technique

Background: The diagnosis of low-grade infections of endoprostheses is challenging. There are still no unified guidelines for standardised diagnostic approaches, recommendations are categorised into major and minor criteria. Additional histopathological samples might sustain the diagnosis. However, ambulatory preoperative biopsy collection is not widespread. Method: 102 patients with hip or knee endoprosthesis and suspected periprosthetic joint infection (PJI) were examined by arthrocentesis with microbiological sample and histopathological punch biopsy. The data were retrospectively analysed for diagnosis concordance. Results: Preoperative microbiology compared to intraoperative results was positive in 51.9% (sensitivity 51.9%, specificity 97.3%). In comparison of preoperative biopsy to intraoperative diagnostic results 51.9% cases were positive (sensitivity 51.9%, specificity 100.0%). The combination of preoperative biopsy and microbiology in comparison to intraoperative results was positive in 70.4% of the cases (sensitivity 70.4%, specificity 97.3%). Conclusion: The diagnosis of PJI is complex. One single method to reliably detect an infection is currently not available. With the present method histopathological samples might be obtained quickly, easily and safely for the preoperative detection of PJI. A combination of microbiological and histopathological sampling increases the sensitivity up to 18.5% to detect periprosthetic infection.

Localized cytokine responses to total knee arthroplasty and total knee revision complications

Background

The study of localized immune-related factors has proven beneficial for a variety of conditions, and one area of interest in the field of orthopaedics is the impact of implants and localized infections on immune response. Several cytokines have shown increased systemic concentrations (in serum/plasma) in response to implants and infection, but tissue-level cytokines have not been investigated as thoroughly.

Methods

This exploratory study investigated tissue-level cytokines in a cohort of patients (N = 17) in response to total knee arthroplasty and total knee revision to better understand the immune response to implants and localized infection (e.g., prosthetic joint infection). The overall goal of this study was to provide insight into the localized cytokine response of tissues and identify tissue-level markers specific to inflammation caused by implants vs. inflammation caused by infection. Tissues were collected across several anatomical locations and assayed with a panel of 20 human inflammatory cytokines to understand spatial differences in cytokine levels.

Results

In this study, six cytokines were elevated in implanted joints, as compared to native joints: IL-10, IL-12p70, IL-13, IL-17A, IL-4, and TNF-α (p < 0.05). Seven cytokines showed infection-dependent increases in localized tissues: IL-1α, IL-1β, IL-6, IL-8, MCP-1, MIP-1α, and MIP-1β (p < 0.05).

Conclusions

This study demonstrated that differences exist in tissue-level cytokines in response to presence of implant, and some cytokines were specifically elevated for infection; these responses may be informative of overall tissue health. These results highlight the utility of investigating localized cytokine concentrations to offer novel insights for total knee arthroplasty and total knee revision procedures, as well as their complications. Ultimately, this information could provide additional, quantitative measurements of tissue to aid clinical decision making and patient treatment options.

Accuracy of blood-tests and synovial fluid-tests in the diagnosis of periprosthetic joint infections

INTRODUCTION

Periprosthetic joint infection (PJI) is one of the most complex complications following total joint arthroplasty. Despite significant progress in recent years, the use of blood and synovial biomarkers to diagnose PJI remains a challenge.

AREAS COVERED

A combination of serological, synovial, microbiological, histological, and radiological investigations is suggested by consensus and international guidelines. Novel biomarkers and molecular methods have shown promise in recent years. The purpose of this review is to provide an update about the biomarkers used to diagnose PJI and highlight their sensitivity and specificity. In addition, guidance on the diagnostic steps and clinical workflow will be included.

EXPERT OPINION

The diagnostic algorithm developed and validated by the international consensus meeting group is still the most valuable resource to approach PJI diagnosis. The current combination of blood and synovial biomarkers yield acceptable results and good performance. However, there is a need for new biomarkers and further research to understand the limitations of current tests better, as well as explore new options such as alpha-defensin, D-dimer, interleukin-6, and leukocyte esterase.

Combined serum biomarker analysis shows no benefit in the diagnosis of periprosthetic joint infection

Purpose

In many cases, the diagnosis of a periprosthetic joint infection (PJI) consisting of the clinical appearance, laboratory tests, and other diagnostic tools remains a difficult task. Single serum biomarkers are easy to collect, are suitable for periodical assessment, and are a crucial tool in PJI diagnosis, but limited sensitivity or specificity is reported in literature. The aim of this study was to combine the best-performing single serum biomarkers into a multi-biomarker model aiming to improve the diagnostic properties.

Methods

Within a 27-month period, 124 surgical procedures (aseptic or septic revision total knee arthroplasty (TKA) or total hip arthroplasty (THA)) were prospectively included. The serum leukocyte count, C-reactive protein (CRP), interleukin-6, procalcitonin, interferon alpha, and fibrinogen were assessed 1 day prior to surgery. Logistic regression with lasso-regularization was used for the biomarkers and all their ratios. After randomly splitting the data into a training (75%) and a test set (25%), the multi-biomarker model was calculated and validated in a cross-validation approach.

Results

CRP (AUC 0.91, specificity 0.67, sensitivity 0.90, p value 0.03) and fibrinogen (AUC 0.93, specificity 0.73, sensitivity 0.94, p value 0.02) had the best single-biomarker performances. The multi-biomarker model including fibrinogen, CRP, the ratio of fibrinogen to CRP, and the ratio of serum thrombocytes to CRP showed a similar performance (AUC 0.95, specificity 0.91, sensitivity 0.72, p value 0.01).

Conclusion

In this study, multiple biomarkers were tested for their diagnostic performance, with CRP and fibrinogen showing the best results regarding the AUC, accuracy, sensitivity, and specificity. It was not possible to further increase the diagnostic accuracy by combining multiple biomarkers using sophisticated statistical methods.

Is Procalcitonin (PCT) a reliable biomarker for preoperative diagnosing of low grade periprosthetic joint infection? A prospective study

BACKGROUND

Since a "gold-standard" is missing, diagnosing periprosthetic joint infection (PJI) remains a challenge in orthopedic surgery. The purpose of this study was to evaluate the accuracy of serum and synovial fluid Procalcitonin (S-PCT and SF-PCT) as a diagnostic parameter and to compare it to the biomarkers recommended in the 2018 Definition of periprosthetic hip and knee infection.

METHODS

Between August 2018 and July 2019, a prospective cohort study was conducted in 70 patients with painful hip, shoulder and knee arthroplasty. Besides medical history, clinical and laboratory data was gathered. PJI was diagnosed based on the 2018 Definition of periprosthetic hip and knee infection. Preoperative blood and synovial joint fluid were taken for PCT measurement. S-PCT and SF-PCT levels were measured using standard quantitative PCT enzyme immunoassays.

RESULTS

Twenty three patients (33%) were classified as the PJI group and fourty seven patient (67%) as the aseptic group. The mean levels of S-PCT were significantly (p <  0.001) higher in the PJI group than those in the aseptic group (PJI 0.05 ± 0.21 ng/mL (0.0-1.03) vs. aseptic 0.02 ± 0.03 ng/mL (0.0-0.18)). In synovial fluid, the mean PCT values in the aseptic group were significantly higher (p <  0.001) than those of PJI group (PJI 2.7 ± 1.4 ng/mL (0.53-9.7) vs. aseptic 8.7 ± 2.5 ng/mL (0.25-87.9)). S- PCT, with a cut-off level of 0.5 ng/mL, had a sensitivity of 13.0% and a specificity of 91.0%. SF-PCT, with a cut-off level of 5.0 ng/mL, had a sensitivity of 13.0% and a specificity of 52.0%.

CONCLUSION

S-PCT and SF-PCT appeared to be no reliable biomarkers in the differential diagnosis of PJI from aseptic loosening in total joint arthroplasty.

Combined Measurement of D-Dimer and C-Reactive Protein Levels: Highly Accurate for Diagnosing Chronic Periprosthetic Joint Infection

BACKGROUND

Diagnosis of chronic periprosthetic joint infection (PJI) can be challenging and elusive in the absence of a gold standard. D-dimer plays an important role in inflammation that occurs during infections and therefore could be a valuable biomarker for PJI. This study aims to investigate the sensitivity and specificity of D-dimer in detecting chronic PJI and to improve the accuracy of chronic PJI diagnosis through combined measurement of serum D-dimer with C-reactive protein (CRP)/erythrocyte sedimentation rate.

METHODS

One hundred twenty-two patients presenting with a painful knee or hip after total hip or total knee arthroplasty for surgical revision were included in this prospective trial. Our cohort consisted of 55 patients undergoing revision for chronic PJI and 67 patients undergoing revision for aseptic failure. PJI was defined using the Musculoskeletal Infection Society criteria. Receiver operating characteristic curves and area under the curve were analyzed for each biomarker.

RESULTS

The area under the curve for D-dimer was 0.915 and was more accurate than serum erythrocyte sedimentation rate 0.719 and CRP 0.761. 1170 ng/mL was determined to be the optimal threshold value of D-dimer for the diagnosis of chronic PJI, with a sensitivity of 92.73% and a specificity of 74.63% in the diagnosis of chronic PJI. The combination of D-dimer and CRP tests demonstrated a sensitivity of 98.11% and negative predictive value of 96.55% for the diagnosis of chronic PJI.

CONCLUSION

The present study identified the D-dimer is a valuable biomarker in detecting chronic PJI. The combinations of serum D-dimer and CRP led to the improvement of sensitivity compared with those of the single-index test.

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.

Diagnosing Prosthetic Joint Infections in Patients With Inflammatory Arthritis: A Systematic Literature Review

BACKGROUND

Patients with inflammatory arthritis (IA) are at increased risk of prosthetic joint infections (PJI), yet differentiating between septic and aseptic failure is a challenge. The aim of our systematic review is to evaluate synovial biomarkers and their efficacy at diagnosing PJI in patients with IA.

METHODS

A comprehensive literature search was performed in the following databases from inception to January 2018: Ovid MEDLINE, Ovid EMBASE, and the Cochrane Library. Searches across the databases retrieved 367 results. Two of 5 reviewers independently screened a total of 298 citations. Discrepancies were resolved by a third reviewer. Twenty articles fit our criteria, but due to methodological differences findings could not be pooled for meta-analysis. For 5 studies, raw data were provided, pooled, and used to derive optimal diagnostic cut points.

RESULTS

Our final analysis included 1861 non-IA patients, including 426 patients with PJI, and 90 IA patients of whom 26 had PJI. There was a significant difference among the 4 groups for serum C-reactive protein (CRP), erythrocyte sedimentation rate, and synovial CRP, polymorphonuclear neutrophil percent, white blood cells, interleukin (IL)-6, IL-8, and IL-1b. Polymorphonuclear neutrophil percent had the highest sensitivity (95.2%) and specificity (85.0%) to detect infections with an optimum threshold of 78%.

CONCLUSION

While levels of synovial white blood cells, IL-6, IL-8, and serum CRP appear higher in patients with IA, there is overlap with those who are not infected. Further studies are needed to explore diagnostic tests that will better detect PJI in patients with IA.

Curcumin nanoparticles are a promising anti-bacterial and anti-inflammatory agent for treating periprosthetic joint infections

Background

Periprosthetic joint infections (PJIs) have a high incidence of recurrence after total joint replacement and are difficult to treat by debridement or antibiotic treatment. Curcumin is a natural product with anti-inflammatory and anti-bacterial properties. The low bioactivity of curcumin in water restricts its clinical application. Curcumin nanoparticles (CURN) were developed to overcome this limitation.

Methods

In this study, the therapeutic effects of CURN and their anti-inflammatory functions were investigated in a Staphylococcus aureus biofilm-induced PJIs model.

Results

CURN first attenuated the biofilm-induced expansion of myeloid-derived suppressor cells (MDSCs) and then regulated M1- and M2-phenotypic MDSC expression. Down-regulation of cytokines and reactive oxygen species was considered as the mechanism of CURN in reversing the suppression of T cell proliferation. The recovery of bone permeative destruction demonstrated that CURN enhanced therapeutic potency of vancomycin in vivo.

Conclusion

This is the first study to demonstrate that CURN may be useful for treating PJIs.

Evidence-Based Management of Trunnionosis in Metal-on-Polyethylene Total Hip Arthroplasty: A Systematic Review

Multiple recent reports have indicated a rising awareness of trunnionosis-related implant failures, accounting for up to 3% of all total hip arthroplasty revisions. Moreover, aseptic loosening and osteolysis from local release of metal debris can be the presenting manifestations, and thus the true incidence of trunnionosis is thought to be underreported. Furthermore, the relatively unclear and multifactorial pathogenesis and the widely variable clinical presentations pose a diagnostic challenge. A consensus regarding the ideal intervention and its timing is also lacking. Because of the relative paucity of reports regarding the diagnosis and management of trunnionosis, we conducted this evidence-based review to evaluate the (1) incidence, (2) pathogenesis, (3) diagnosis, and (4) treatment of trunnionosis in metal-on-polyethylene total hip arthroplasty. We then propose an algorithm for the diagnostic work-up and management of this condition.

Current Recommendations for the Diagnosis of Acute and Chronic PJI for Hip and Knee-Cell Counts, Alpha-Defensin, Leukocyte Esterase, Next-generation Sequencing

PURPOSE OF REVIEW

Despite significant progress in recent years, the diagnosis of periprosthetic joint infection (PJI) remains a challenge and no gold standard test exists. A combination of serological, synovial, microbiological, histological, and radiological investigations is performed that are expensive, often invasive, and imperfect. Novel biomarkers and molecular methods have shown promise in recent years. The purpose of this review is to provide an update about the diagnostic recommendations for PJI and cover a selection of emerging diagnostic tools.

RECENT FINDINGS

Recent literature highlights a new evidence-based definition for diagnosing hip and knee PJI that shows excellent performance on formal external multi-institutional validation. There is also increasing evidence to support the measurement of selected biomarkers in serum and synovial fluid, such as alpha-defensin, D-dimer, and interleukin-6. Finally, the emerging utility of next-generation sequencing for pathogen identification is discussed. In summary, we describe current recommendations and emerging tests for the diagnosis of PJI. Residual limitations and directions for future research are also discussed.

Fibrinogen - A Practical and Cost Efficient Biomarker for Detecting Periprosthetic Joint Infection

The early and accurate diagnosis of periprosthetic joint infection (PJI) can be challenging. Fibrinogen plays an important role in mediating inflammation of bacterial infections and therefore could be a valuable biomarker for PJI. The purpose of this study was to investigate the sensitivity and specificity of serum levels of fibrinogen in detecting PJI, and to compare the results with the established PJI biomarkers C-reactive protein (CRP) and leukocyte count. Eighty-four patients (124 surgeries) were prospectively included. The preoperatively analyzed parameters were fibrinogen, CRP and leukocyte count. The sensitivity and specificity of the biomarkers were calculated and compared. Fibrinogen (p < 0.001), CRP (p < 0.001) and leukocyte count (p < 0.001) had a statistically significant correlation with the criteria defining the presence of PJI. For fibrinogen, the value of 519 mg/dl had a sensitivity of 0.90 and a specificity of 0.66. The CRP cut-off point of 11.00 mg/dl had a sensitivity of 0.90 and a specificity of 0.74. The leukocyte count of 5.68 G/l had a sensitivity of 0.90 and a specificity of 0.39. Our results indicated that fibrinogen is a significant biomarker for detecting a bacterial PJI. It has shown to be a cost-efficient diagnostic support with high sensitivity and specificity.

Puncture Protocol in the Diagnostic Work-Up of a Suspected Chronic Prosthetic Joint Infection of the Hip

BACKGROUND

Diagnosing a chronic prosthetic joint infection (PJI) can be challenging. We hypothesized that obtaining preoperative tissue samples for culture in hip arthroplasty will increase the likelihood of diagnosing an infection before revision surgery. The aim of this cohort study was to determine the diagnostic accuracy of 2 tissue acquiring biopsy strategies to diagnose a PJI.

METHODS

Patients with a painful hip arthroplasty, in which a chronic PJI was suspected, were included. Tissue samples were obtained either by ultrasound guidance with a 16-Gauge needle (2012-2013) or in the operating room with a thick-bore needle (2013-2016). Revision surgery tissue biopsies were used as the gold standard. Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio were calculated.

RESULTS

A total of 16 patients in the ultrasound cohort and 29 patients in the surgical cohort were included. Thirty-one percent (n = 14) were finally diagnosed with a PJI. The addition of thick bore needle tissue biopsies resulted in 9% more diagnosed PJIs compared with synovial fluid alone. The sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio was 33%, 85%, 33%, 85%, 2.2, and 0.8, respectively, for the ultrasound-guided biopsy cohort and 82%, 100%, 100%, 90%, infinite, and 0.2, respectively, for the surgical biopsy cohort.

CONCLUSION

Obtaining multiple good quality tissue biopsies in a sterile environment will contribute to the diagnosis of a chronic PJI of the hip, with a higher diagnostic accuracy compared with ultrasound-guided thin needle biopsies and compared with synovial fluid culture alone.

Periprosthetic knee infection: two stage revision surgery

Periprosthetic joint infection (PJI) remains a serious complication following a total joint replacement.  Diagnosis and management of PJI is challenging for surgeons since there is no "gold standard". This challenging condition requires a coordinated management approach to achieve good patient outcomes. Further difficulties involve choosing the optimal method to treat the periprosthetic joint infection. In this article, it is stressed the role of the two-stage revision: implant removal, debridement and placement of an antibiotic spacer, and antibiotic therapy with cessation prior to reimplantation. Published literature shows that two stage revision is a valid treatment option for periprosthetic joint infection.

Diagnostic accuracy of alpha-defensin in periprosthetic joint infection: a systematic review and meta-analysis

BACKGROUND

Alpha-defensin, a novel biomarker, has shown great potential for the accurate diagnosis of periprosthetic joint infection (PJI) in recent years: many published studies have presented encouraging results. Nevertheless, the diagnostic accuracy of alpha-defensin is inconsistent across published studies. Moreover, the optimum value of the diagnostic threshold urgently needs to be ascertained. This meta-analysis sought to estimate the precision of alpha-defensin for the diagnosis of PJI and, where possible, to confirm the threshold.

METHOD

We systematically searched PubMed, Embase, Cochrane, Web of Knowledge, and ClinicalTrials.gov for relevant literature on alpha-defensin in the diagnosis of PJI (searching publications from the inception of each database until February 2017, with no language restriction). Pooled sensitivity, specificity, diagnostic odds ratios, and likelihood ratios were the indexes used for assessment, with the use of a random-effects model.

RESULT

Eleven of the 426 studies that evaluated the diagnostic accuracy of alpha-defensin in periprosthetic joint infection (PJI) were included in this analysis. The pooled diagnostic sensitivity of alpha-defensin for PJI was 0.96 (95% confidence interval [CI], 0.87 to 0.99) and the specificity was 0.95 (95% CI, 0.91 to 0.97). Since there was substantial heterogeneity among studies, based on the inconsistency index (I²), threshold, site of arthroplasty, study design and techniques for the alpha-defensin test, subgroup analyses were performed to estimate the impacts of these variables on heterogeneity.

CONCLUSION

In summary, this meta-analysis clearly lends support to the conclusion that alpha-defensin is a promising addition to the current methods for diagnosis of PJI.

Periprosthetic knee infection: two stage revision surgery

Periprosthetic joint infection (PJI) remains a serious complication following a total joint replacement.  Diagnosis and management of PJI is challenging for surgeons since there is no "gold standard". This challenging condition requires a coordinated management approach to achieve good patient outcomes. Further difficulties involve choosing the optimal method to treat the periprosthetic joint infection. In this article, it is stressed the role of the two-stage revision: implant removal, debridement and placement of an antibiotic spacer, and antibiotic therapy with cessation prior to reimplantation. Published literature shows that two stage revision is a valid treatment option for periprosthetic joint infection.