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

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.

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.