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

The Application of artificial intelligence in periprosthetic joint infection

Periprosthetic joint infection (PJI) represents one of the most devastating complications following total joint arthroplasty, often necessitating additional surgeries and antimicrobial therapy, and potentially leading to disability. This significantly increases the burden on both patients and the healthcare system. Given the considerable suffering caused by PJI, its prevention and treatment have long been focal points of concern. However, challenges remain in accurately assessing individual risk, preventing the infection, improving diagnostic methods, and enhancing treatment outcomes. The development and application of artificial intelligence (AI) technologies have introduced new, more efficient possibilities for the management of many diseases. In this article, we review the applications of AI in the prevention, diagnosis, and treatment of PJI, and explore how AI methodologies might achieve individualized risk prediction, improve diagnostic algorithms through biomarkers and pathology, and enhance the efficacy of antimicrobial and surgical treatments. We hope that through multimodal AI applications, intelligent management of PJI can be realized in the future.

BAPTA-based potentiometric polymer sensor: towards sensing inflammations and infections

Potentiometric ion sensors represent a significant subgroup of electrochemical sensors. In this study, we have developed a potentiometric sensor using an electrically conductive copolymer of 2,2'-bithiophene (BT) and 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) for the selective detection of Ca2+ ions in extracellular interstitial fluids. The integration of BAPTA with its highly selective calcium chelating properties into a polymer matrix via electrochemical polymerization results in a sensitive conductive polymer layer that effectively detects the presence of calcium ions. This sensor aims at the early detection of inflammation or infection around implants because local calcium concentration is strongly elevated in interstitial fluid in such pathologies. The potentiometric study proves the incorporation of BAPTA into the polymer matrix was successful and its potential decreased upon calcium binding demonstrating the Nernstian behavior with a slope of approximately 20 ± 0.3 mV per decade in the concentration range from 0.1 mM to 1 mM. Moreover, the selectivity coefficient of -0.4 was measured by SSM and calculated from the Nicolsky-Eisenmann equation, which indicates selectivity towards Ca2+ ions with respect to Mg2+ ions.

Natural course of postoperative C-reactive protein and erythrocyte sedimentation rate in unilateral and simultaneous bilateral total knee arthroplasty

BACKGROUND

C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are valuable markers for detecting periprosthetic joint infection (PJI) post-total knee arthroplasty (TKA). However, their prolonged elevation after TKA diminishes diagnostic reliability. This study investigates CRP and ESR trends in unilateral (U-TKA) and simultaneous bilateral TKA (SB-TKA) patients, comparing their patterns.

METHODS

Between 2017 and 2023, preoperative and postoperative (weeks 2, 4, 6) CRP and ESR levels were assessed in U-TKA (32 patients) and SB-TKA (29 patients) groups for gonarthrosis.

RESULTS

Median preoperative CRP levels were 1.13 mg/dL (U-TKA) and 0.2 mg/dL (SB-TKA), with corresponding ESR levels of 13.50 mm/h and 10 mm/h. While CRP and ESR increased more in SB-TKA, differences were statistically insignificant (p > 0.05). Both groups showed significant differences in CRP and ESR values at all time points (p < 0.05). U-TKA patients reached CRP < 5 mg/dL and ESR < 30 mm/h by the 6th postoperative week. SB-TKA patients did not exhibit significantly higher CRP and ESR levels at various intervals compared to U-TKA patients (p > 0.05).

CONCLUSION

This study delineates postoperative CRP and ESR trends in U-TKA and SB-TKA for osteoarthritis. CRP values decreased below 5 mg/dL, and ESR values below 30 mm/h within 6 weeks in both groups. Statistically significant differences in CRP and ESR values were observed at all time points. No significant differences were found in CRP and ESR trends between both groups. These findings aid physicians in interpreting laboratory reports for PJI determination.

LEVEL OF EVIDENCE

III.

Diagnostic Thresholds of Synovial Markers for Acute Periprosthetic Joint Infection: One Size Does Not Fit All

BACKGROUND

The diagnosis of periprosthetic joint infection (PJI), particularly during the early postoperative period, remains challenging. The purpose of this multicenter study was to assess the utility of synovial white blood cell (WBC) count and polymorphonuclear leukocyte percentage (PMN%) in the diagnosis of acute PJI at different time intervals after primary total joint arthroplasty (TJA).

METHODS

This retrospective study identified 225 patients who underwent a joint aspiration within 90 days of their primary TJA at three institutions. A PJI was defined as revision TJA for infection within 7 days of joint aspiration with two positive cultures isolating the same organism. Patients were considered aseptic if they had no reoperation for up to 1 year after arthrocentesis. Receiver operator characteristic curves were used to assess the utility of WBC count and PMN% in the diagnosis of acute PJI at zero to 15, 15 to 45, and 45 to 90 days. Youden's index was used to identify the optimal cutoffs at each time interval. A pairwise comparison was performed to compare the area under the curve (AUC) of the two markers. There were 214 patients included. Of these, 81 (37.9%) were infected and 133 (62.1%) were aseptic.

RESULTS

The optimal cutoff at zero to 15 days was 21,003 cells/μL for WBC count (AUC 0.937, sensitivity 88.0%, specificity 100%) and 92.0% for PMN% (AUC 0.638, sensitivity 56.0%, specificity 68.4%). Although the diagnostic threshold for WBC count decreased to 5,111 cells/μL at 15 to 45 days and to 2,503 cells/μL at 45 to 90 days, the cutoffs for PMN% did not downtrend in the same fashion (80% at 15 to 45 days; 86% at 45 to 90 days). Using pairwise comparison, the AUC for WBC count was higher than that of PMN% at 0 to 15 days (P = 0.002); however, there was no difference in AUCs at either 15 to 45 days (P = 0.438) or 45 to 90 days (P = 0.826).

CONCLUSIONS

Based on our findings, it appears that there may be a role for diagnostic thresholds for the identification of acute PJI that are specific to the timing of joint aspiration after primary TJA.

The Utility of Synovial Fluid Interleukin-10 in Diagnosing Chronic Periprosthetic Joint Infection: A Prospective Cohort Study

Background

Diagnosing chronic periprosthetic joint infection (PJI) is challenging. Synovial fluid interleukin-10 (SF IL-10), an anti-inflammatory cytokine produced by leukocytes, plays a pivotal role in inflammation and infection regulation. However, limited research has explored the diagnostic potential of SF IL-10 in chronic PJI patients.

Objective

The study aimed to investigate the relationship between SF IL-10 and incidence of chronic PIJ, and to evaluate its diagnostic reliability.

Design and Methods

We analyzed data from 137 patients who underwent revision surgery for aseptic loosening or chronic PJI between 2017 and 2019 in our hospital. PJI diagnoses followed the 2013 International Consensus Meeting criteria. We measured serum ESR, serum CRP, SF PMN%, SF WBC and SF IL-10 levels, using logistic regression and receiver operating characteristic (ROC) curves to evaluate associations and diagnostic accuracy.

Results

Demographic data showed no significant differences. However, SF IL-10 levels differed significantly between groups. Logistic regression indicated a strong association between SF IL-10 and chronic PJI (OR = 1.11, 95% CI 1.05~1.17, p < 0.001). At a cut-off of 10.305 pg/mL, SF IL-10 had an area under the ROC curve (AUC) of 0.891, with 92.16% sensitivity and 77.91% specificity. Adding SF IL-10 to traditional models improved risk prediction for chronic PJI (net reclassification improvement [NRI]: 0.167 [0.023 ~ 0.312]; integrated discrimination improvement [IDI]: 0.160 [0.096 ~ 0.224]).

Conclusion

Higher SF IL-10 levels were significantly associated with chronic PJI in revision surgery patients, and incorporating SF IL-10 into the traditional risk model enhanced its predictive value for chronic PJI in these patients.

Synovial fluid alpha-defensins in Lyme arthritis-a useful marker

Lyme arthritis, one of the possible late manifestations of Lyme borreliosis, predominantly affects the supporting joints and in adults most often occurs in the form of monoarthritis of the knee. Early diagnosis is based on clinical findings and serology. PCR detection of Borrelia in synovial fluid has become an integral part of the laboratory testing algorithm. The clinical presentation and inflammatory markers in Lyme arthritis can resemble septic arthritis. Determining the levels of alpha-defensins (human neutrophil peptide (HNP 1-3)) in synovial fluid by liquid chromatography is a highly sensitive method revealing the presence of inflammatory process. Between 2020 and 2022, we examined eleven patients with Lyme arthritis of the knee. We measured levels of HNP 1-3 from synovial fluid by HPLC in patients, and we compared it with the corresponding C-reactive protein (CRP) levels in paired serum samples. In patients diagnosed with Lyme arthritis, HNP 1-3 levels in synovial fluid ranged from 2.5 to 261 mg/L, with a median of 46.5 mg/L. Average serum CRP was 43 mg/L. The results show that elevated HNP 1-3 can be consistent with not only septic arthritis or systemic disease, but also with Lyme arthritis, especially in patients with negative culture and 16S PCR from synovial fluid. Final diagnosis must be verified by examination for anti-Borrelia antibodies from serum and synovial fluid. The aim of this work is to introduce an HPLC method for the determination of alpha-defensins as one of the possible diagnostic markers.

Comparative performance analysis of Synovasure™ and Leukocyte Esterase assays for the diagnosis of periprosthetic infections in complex microbiological situations

INTRODUCTION

Osteoarticular infections (OAI) after prosthetic surgery have serious functional and economic consequences. Rapid tests for alpha-defensin (TAD) and leukocyte esterase (TLE) are two intra-articular markers involved in the diagnosis of OAIs. TLE cannot be applied in the presence of blood unless centrifugation is used, but the rate of "non-application" of the test for this reason is unknown in complex microbiological situations (discordant or negative puncture, ongoing antibiotic treatment). We therefore conducted a prospective study to determine: 1) the performance of the TAD and TLE rapid tests in diagnosing complex OAI, 2) the rate of non-application of the TLE due to hemarthrosis, and 3) the concordance between the two tests.

ASSUMPTION

These two diagnostic tests had a negative predictive value (NPV) ≥ 90% for the diagnosis of complex OAI.

MATERIALS AND METHODS

A total of 79 suspected OAI patients with complex microbiological diagnoses were included between 2018 and 2023. They were 52 men (66%) for 27 women (34%), with a mean age of 66 ± 13.5 years. The hip (n = 41, 52%) and knee (n = 36, 46%) were the most represented, followed by the elbow (n = 1, 1%) and shoulder (n = 1, 1%). These patients were suspected of having an OAI that required joint puncture, but with a complex microbiological diagnosis due to discordant punctures (n = 21, 27%) or sterile punctures despite strong suspicion of infection (n = 50, 63%), or in case of ongoing antibiotic treatment (n = 8, 10%). All patients underwent joint fluid puncture followed by TAD (Synovasure™, Zimmer, Warsaw, IN, USA) and, when the macroscopic appearance of the sample allowed (clear fluid group), TLE (Multistix 8SG, Siemens Healthcare GmbH, Erlangen, Germany). The results of both tests were compared with Musculoskeletal Infection Society (MSIS) criteria.

RESULTS

Of the 79 patients included, 27 (34%) were considered infected according to the MSIS. In 30% of cases (n = 24), TLE was not feasible due to the presence of blood in the joint fluid. In the "clear fluid" group, the NPV was equal to 90% for both TAD (sensitivity 87%, specificity 88%) and TLE (sensitivity 87%, specificity 81%). The two parameters showed almost perfect agreement (κ = 0.927).

CONCLUSION

TAD and TLE are two rapid, reliable tests with near-perfect concordance and high NPV, even in situations of complex microbiological diagnosis. They are particularly useful for deciding on a therapeutic strategy for patients with complex OAI. The TLE cannot be used in 30% of cases due to hemarthrosis, but centrifugation can correct this defect.

LEVEL OF EVIDENCE

III; Prospective comparative diagnostic accuracy study.

Fungal Shoulder Periprosthetic Infections: A Systematic Review

Background: Data regarding fungal PJIs of the shoulder are scarce. The present systematic review aims to identify and evaluate all published shoulder fungal PJIs in an effort to better understand the diagnostic and therapeutic approach to these infections. Methods: A systematic review according to the PRISMA guidelines was conducted, locating all shoulder fungal PJIs. The initial search located 1435 articles. Data were collected on demographics, the causative fungus, antifungal treatment (AFT), surgical interventions, and infection outcomes. Results: After screening and implementation of the inclusion criteria, a total of 10 articles, including 10 cases, were eligible. The sample's mean age was 62.44 years. Diabetes mellitus was the most common comorbidity (30%), while 70% were immunocompromised. Candida spp. was the most common causative fungus (nine cases; 90%), while all cases were confirmed with cultures. In three cases (30%), there was bacterial co-infection. The mean duration of antifungal treatment (AFT) was 8.4 weeks, while the preferred agent was fluconazole (60% of cases), followed by amphotericin B (30%). Most cases (50%) underwent resection arthroplasty as part of the treatment, while two-stage revision arthroplasty was performed in 30%. Infection's eradication was reported in 90% of the studied cases. Conclusions: The diagnosis and management of fungal periprosthetic shoulder infections are particularly challenging and require a multidisciplinary approach. The combination of antifungal therapy and tailored surgical strategies is crucial, but further research is needed to refine treatment protocols and address the unique considerations in shoulder PJIs.

Sonication protocols and their contributions to the microbiological diagnosis of implant-associated infections: a review of the current scenario

Addressing the existing problem in the microbiological diagnosis of infections associated with implants and the current debate about the real power of precision of sonicated fluid culture (SFC), the objective of this review is to describe the methodology and analyze and compare the results obtained in current studies on the subject. Furthermore, the present study also discusses and suggests the best parameters for performing sonication. A search was carried out for recent studies in the literature (2019-2023) that addressed this research topic. As a result, different sonication protocols were adopted in the studies analyzed, as expected, and consequently, there was significant variability between the results obtained regarding the sensitivity and specificity of the technique in relation to the traditional culture method (periprosthetic tissue culture - PTC). Coagulase-negative Staphylococcus (CoNS) and Staphylococcus aureus were identified as the main etiological agents by SFC and PTC, with SFC being important for the identification of pathogens of low virulence that are difficult to detect. Compared to chemical biofilm displacement methods, EDTA and DTT, SFC also produced variable results. In this context, this review provided an overview of the most current scenarios on the topic and theoretical support to improve sonication performance, especially with regard to sensitivity and specificity, by scoring the best parameters from various aspects, including sample collection, storage conditions, cultivation methods, microorganism identification techniques (both phenotypic and molecular) and the cutoff point for colony forming unit (CFU) counts. This study demonstrated the need for standardization of the technique and provided a theoretical basis for a sonication protocol that aims to achieve the highest levels of sensitivity and specificity for the reliable microbiological diagnosis of infections associated with implants and prosthetic devices, such as prosthetic joint infections (PJIs). However, practical application and additional complementary studies are still needed.

Differences in the Synovial Fluid Proteome of Septic and Aseptic Implant Failure

Implant loosening is a severe complication after total joint replacement. Here, differential diagnosis between septic and aseptic cases is crucial for further surgical treatment, but low-grade periprosthetic joint infections (PJIs) in particular remain a challenge. In this study, we analyzed the synovial fluid proteome of 21 patients undergoing revision surgery for septic (eight cases) or aseptic (thirteen cases) implant failure using LC-MS/MS to identify potential new biomarkers as future diagnostic tools. Staphylococci were found in four cases, Streptococci in two cases, Serratia marcescens and Cutibacterium acnes in one case. Proteomic analysis of the synovial fluid resulted in the identification of 515 different proteins based on at least two peptides. A statistical comparison revealed 37 differentially abundant proteins (p < 0.05), of which 17 proteins (46%) showed a higher abundance in the septic group. The proteins with the highest fold change included the known marker proteins c-reactive protein (7.57-fold) and the calprotectin components protein S100-A8 (4.41-fold) and protein S100-A9 (3.1-fold). However, the protein with the highest fold change was leucine-rich alpha-2-glycoprotein 1 (LRG1) (9.07-fold), a currently discussed new biomarker for inflammatory diseases. Elevated LRG1 levels could facilitate the diagnosis of PJI in the future, but their significance needs to be further investigated.

Application of the New Irrigation Protocol to Reduce Recurrence Rate in the Management Of Periprosthetic Joint Infection

OBJECTIVE

Irrigation is a conventional treatment for acute and chronic periprosthetic joint infections (PJI). However, there has been no unified standard for irrigation during surgery for PJI in the past, and the efficacy is uncertain. The purpose of this study is to create a new irrigation protocol to enhance the infection control rate and reduce the postoperative recurrence rate of PJI patients.

METHODS

We conducted a single-institution retrospective review with a total of 56 patients who underwent revision total hip or knee arthroplasties due to PJI from January 2011 to January 2022. Conventional irrigation (CI) was used in 32 cases, and standard operating procedure of irrigation (SOPI) was used in 24. The CI protocol carries out an empirical irrigation after debridement, which is quite random. Our SOPI protocol clearly stipulates the soaking concentration and time of hydrogen peroxide and povidone-iodine. The irrigation is carried out three times, and tissue samples are taken from multiple parts before and after irrigation, which are sent for microbial culture. The important statistical indicators were the rate of positive microbiological culture and postoperative recurrence rate with an average follow-up of 24 average months.

RESULTS

The drainage volume was lower in the SOPI group than in the CI group on postoperative day 3 (p < 0.01) and 7 (p = 0.016). In addition, the percentage of positive microbiological cultures after the third irrigation was less than that before (p < 0.01) and after (p < 0.01) the first irrigation. The most common causative organism was Staphylococcus aureus, which was detected in 25.0% and 12.5% of the SOPI and CI groups, respectively. The failure rate at the final follow-up was 8.3% and 31.3% (p = 0.039) for the SOPI and CI groups, respectively.

CONCLUSION

Compared with the traditional CI method, SOPI standardized the soaking time of hydrogen peroxide and povidone-iodine, increased the frequency of and irrigation, and proved that microorganisms were almost completely removed through the microbial culture of multiple tissues. SOPI has the potential to become a standardized irrigation process worthy of promotion, effectively reducing the postoperative recurrence rate of PJI patients.

An Innovative Approach to Produce Silicone Mold-Based Antibiotic-Loaded Knee Spacer for Infected Knee Arthroplasty

This study aimed to evaluate the efficacy of antibiotic-loaded cement articulating spacers produced through a silicone mold in the two-stage revision of infected total knee arthroplasty. Five individuals were prospectively treated with 2-stage revision using spacers made by this mold. Clinical assessment was conducted during and after implantation using the WOMAC Score, Oxford knee score, and range of motion (ROM). The results showed that the ROM increased by an average of 35 degrees during the spacer stage, with an average ROM of 100 degrees. Furthermore, there was an average gain of 85.2 points in the Knee Society Score and an average rise of 22.8 points in the total WOMAC scores. This approach had a similar effect on improving infection, motion performance, and patients' satisfaction with metal articular molds but without high-technology equipment and low-cost price. Therefore, this method could be applied to any operating room that performs arthroplasty surgery.