Lipopolysaccharide-binding protein: a valuable biomarker in the differentiation between periprosthetic joint infection and aseptic loosening?

Is large unstained cell percentage (%LUC) a novel diagnostic marker for periprosthetic joint infections?

BACKROUND

Periprosthetic joint infection (PJI) is a very important complication that occurs after total joint replacement. Diagnosing PJI is at least as difficult as this disease. There is no biomarker that alone can diagnose PJI.

OBJECTIVE

This study aimed to evaluate the effectiveness of large unstained cell percentage (%LUC) in diagnosing PJI and deciding on re-implantation in two stage septic exchange arthroplasty.

METHODS

Patients who underwent revision arthroplasty between 2019 and 2023 were screened retrospectively. These patients were grouped as those who underwent two-stage septic exchange and those who underwent aseptic exchange. Prosthesis removal from the patients who underwent two-stage septic exchange, before spacer application, and on the 3rd post-operative day after spacer application, Blood parameters were collected at the 1st month and before the second stage after the spacer application, and before the revision surgery from the patients who underwent aseptic exchange. White blood cell, neutrophil percentage, %LUC, albumin, sedim and CRP values were checked and recorded one by one from all patients.

RESULTS

The data of a total of 233 patients, including 133 patients in the two stage septic exchange group and 100 patients in the aseptic exchange group, were included in the study. When the predictive value of %LUC in PJI was accepted as cut-off 1.75, the sensitivity was 69.2% and the specificity was 73%. The change in %LUC over time in patients who underwent two-stage septic exchange was statistically significant (p= 0.0001). A positive correlation was found between the value of .%LUC after spacer application and the value of CRP before prosthesis protrusion/spacer application surgery, and the Spearman correlation coefficient was found to be 0.005.

CONCLUSION

%LUC value can be a promising biomarker for the diagnosis of PJI by considering both sensitivity and specificity rates. Apart from this, it is an easily accessible and effective biomarker for re-implantation decision making and evaluation of response to treatment, especially in two-stage septic exchange surgeries.

Role of Biomarkers in Periprosthetic Joint Infections

Periprosthetic joint infection (PJI) is one of the most serious complications after joint arthroplasty. The incidence rate of PJI after total joint replacement is 1-3%. Although there are different guidelines and diagnostic criteria used to diagnose PJI, diagnosing PJI is a highly difficult process for orthopedists. The current Musculoskeletal Infection Society (MSIS) criteria are widely used for the diagnosis of PJI. These criteria include results from blood/synovial fluid tests, physical examination, and histological and microbiological analyses of intra-operative samples. However, there is currently no blood or synovial test that can definitively diagnose PJI. To make a more effective diagnosis of PJI, a large number of studies have explored and continue to investigate biomarkers. This review aims to provide general information about serum and synovial markers used for the diagnosis of PJI that may be used to create a database to guide researchers in new studies.

Reliable Diagnostic Tests and Thresholds for Preoperative Diagnosis of Non-Inflammatory Arthritis Periprosthetic Joint Infection: A Meta-analysis and Systematic Review

Objective

The current diagnostic criteria for periprosthetic joint infection (PJI) are diverse and controversial, leading to delayed diagnosis. This study aimed to evaluate and unify their diagnostic accuracy and the threshold selection of serum and synovial routine tests for PJI at an early stage.

Methods

We searched the MEDLINE and Embase databases for retrospective or prospective studies which reported preoperative‐available assays (serum, synovial, or culture tests) for the diagnosis of chronic PJI among inflammatory arthritis (IA) or non‐IA populations from January 1, 2000 to June 30, 2022. Threshold effective analysis was performed on synovial polymorphonuclear neutrophils (PMN%), synovial white blood cell (WBC), serum C‐reactive protein (CRP), and erythrocyte sedimentation rate (ESR) to find the relevant cut‐offs.

Results

Two hundred and sixteen studies and information from 45,316 individuals were included in the final analysis. Synovial laboratory‐based α‐defensin and calprotectin had the best comprehensive sensitivity (0.91 [0.86–0.94], 0.95 [0.88–0.98]) and specificity (0.96 [0.94‐0.97], 0.95 [0.89–0.98]) values. According to the threshold effect analysis, the recommended cut‐offs are 70% (sensitivity 0.89 [0.85–0.92], specificity 0.90 [0.87–0.93]), 4100/μL (sensitivity 0.90 [0.87–0.93], specificity 0.97 [0.93–0.98]), 13.5 mg/L (sensitivity 0.84 [0.78–0.89], specificity 0.83 [0.73–0.89]), and 30 mm/h (sensitivity 0.79 [0.74–0.83], specificity 0.78 [0.72–0.83]) for synovial PMN%, synovial WBC, serum CRP, and ESR, respectively, and tests seem to be more reliable among non‐IA patients.

Conclusions

The laboratory‐based synovial α‐defensin and synovial calprotectin are the two best independent preoperative diagnostic tests for PJI. A cut off of 70% for synovial PMN% and tighter cut‐offs for synovial WBC and serum CRP could have a better diagnostic accuracy for non‐IA patients with chronic PJI.

Human transcriptomic response to periprosthetic joint infection

Periprosthetic joint infection (PJI), a devastating complication of total joint replacement, is of incompletely understood pathogenesis and may sometimes be challenging to clinically distinguish from other causes of arthroplasty failure. We characterized human gene expression in 93 specimens derived from surfaces of resected arthroplasties, comparing transcriptomes of subjects with infection- versus non-infection-associated arthroplasty failure. Differential gene expression analysis confirmed 28 previously reported potential biomarkers of PJI, including bactericidal/permeability increasing protein (BPI), cathelicidin antimicrobial peptide (CAMP), C-C-motif chemokine ligand 3 (CCL3), 4(CCL4) and C-X-C-motif chemokine ligand 2 (CXCL2), colony stimulating factor 2 receptor beta (CSF2RB), colony stimulating factor 3 (CSF3), alpha-defensin (DEFA4), Fc fragment of IgG receptor 1B (CD64B), intercellular adhesion molecule 1 (ICAM1), interferon gamma (IFNG), interleukin 13 receptor subunit alpha 2 (IL13RA2), interleukin 17D (IL17D), interleukin 1 (IL1A, IL1B, IL1RN), interleukin 2 receptors (IL2RA, IL2RG), interleukin 5 receptor (IL5RA), interleukin 6 (IL6), interleukin 8 (IL8), lipopolysaccharide binding protein (LBP), lipocalin (LCN2), lactate dehydrogenase C (LDHC), lactotransferrin (LTF), matrix metallopeptidase 3 (MMP3), peptidase inhibitor 3 (PI3), and vascular endothelial growth factor A (VEGFA), and identified three novel molecules of potential diagnostic use for detection of PJI, namely C-C-motif chemokine ligand CCL20, coagulation factor VII (F7), and B cell receptor FCRL4. Comparative analysis of infections caused by staphylococci versus bacteria other than staphylococci and Staphylococcus aureus versus Staphylococcus epidermidis showed elevated expression of interleukin 13 (IL13), IL17D, and MMP3 in staphylococcal infections, and of IL1B, IL8, and platelet factor PF4V1 in S. aureus compared to S. epidermidis infections. Pathway analysis of over-represented genes suggested activation of host immune response and cellular maintenance and repair functions in response to invasion of infectious agents. The data presented provides new potential targets for diagnosis of PJI and for differentiation of PJI caused by different infectious agents.

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.].

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.

Exciting Performance of Plasma Fibrinogen in Periprosthetic Joint Infection Diagnosis

Objective

To test the significance of serum C‐reactive protein (CRP), the erythrocyte sedimentation rate (ESR), the platelet count/mean platelet volume ratio (PC/MPV), plasma fibrinogen, and D‐Dimer in periprosthetic joint infection (PJI) diagnosis.

Methods

We retrospectively analyzed the clinical data of 149 patients diagnosed from July 2016 to December 2019 with primary osteoarthritis (OA group, average age 63.18 years [range, 53–82 years] 18 males, 46 females), PJI (PJI group, average age 63.74 years [range, 52–81 years], 16 males, 31 females), and aseptic loosening (aseptic group, average age 63.18 years [range, 53–80 years], 12 male, 26 female) in our department. Demographic data and the sensitivity and specificity of preoperative CRP, ESR, PC/MPV, fibrinogen, and D‐Dimer in PJI diagnosis were compared.

Results

There were no significant differences when the demographic data of the three groups were compared. The expression level of CRP (50.67 ± 58.98 mg/L), ESR (50.55 ± 25.81 mm/h), PC/MPV (35.79 ± 18.00), and fibrinogen (4.85 ± 1.33 μg/mL) in the PJI group were higher than in the OA group (CRP: 4.09 ± 9.68 mg/L; ESR:13.44 ± 9.32 mm/1 h; PC/MPV: 24.97 ± 7.58; fibrinogen: 3.09 ± 0.55 μg/mL) and the aseptic group (CRP: 7.01 ± 11.83 mg/L; ESR: 22.47 ± 17.53 mm/1 h; PC/MPV: 25.18 ± 11.48; fibrinogen: 3.39 ± 0.80 μg/mL), respectively. The expression level of plasma D‐dimer (1.60 ± 1.29 mg/L) in the PJI group was higher than in the OA group (0.49 ± 0.42 mg/L) but similar to that in the aseptic group (1.21 ± 1.35 mg/L). Receiver operating characteristic (ROC) curve analysis demonstrated that the areas under the ROC curve (AUC) for CRP, ESR, PC/MPV, fibrinogen, and D‐dimer were 0.892 (95% confidence interval, 0.829–0.954), 0.888 (0.829–0.947), 0.686 (0.589–0.784), 0.873 (0.803–0.943), and 0.835 (0.772–0.899), respectively. When PC/MPV > 31.70, fibrinogen >4.01 μg/mL, and D‐dimer >1.17 mg/L were set as the threshold values for the diagnosis of PJI, the sensitivity of PC/MPV in PJI diagnosis was lower than that of ESR and plasma fibrinogen. In contrast, there was no significant difference when comparing the specificity of CRP, ESR, PC/MPV, fibrinogen, and D‐dimer in PJI diagnosis.

Conclusion

Plasma fibrinogen is a good new auxiliary diagnostic marker for PJI.

Combination Tests in the Diagnosis of Chronic Periprosthetic Joint Infection: Systematic Review and Development of a Stepwise Clinical Decision-Making Tool

BACKGROUND

Our objective was to identify combination tests used to diagnose chronic periprosthetic joint infection (PJI) and develop a stepwise decision-making tool to facilitate diagnosis.

METHODS

We conducted a systematic review of existing combinations of serum, synovial, and tissue-based tests for diagnosing chronic PJI after hip or knee replacement. This work is an extension of our systematic review of single tests, from which we chose eligible studies that also described the diagnostic performance of combination tests.

RESULTS

Thirty-seven eligible articles described the performance of 56 combination tests, of which 8 combinations had at least 2 studies informing both sensitivity and specificity. We also identified 5 types of combination tests: (1) a type-I Boolean combination, which uses Boolean logic (AND, OR) and usually increases specificity at the cost of sensitivity; (2) a type-II Boolean combination, which usually increases sensitivity at the cost of specificity; (3) a triage-conditional rule, in which the value of 1 test serves to triage the use of another test; (4) an arithmetic operation on the values of 2 tests; and (5) a model-based prediction rule based on a fitted model applied to biomarker values.

CONCLUSIONS

Clinicians can initiate their diagnostic process with a type-II Boolean combination of serum C-reactive protein (CRP) and interleukin-6 (IL-6). False negatives of the combination can be minimized when the threshold is chosen to reach 90% to 95% sensitivity for each test. Once a joint infection is suspected on the basis of serum testing, joint aspiration should be performed. If joint aspiration yields a wet tap, a leukocyte esterase (LER) strip is highly recommended for point-of-care testing, with a reading of ++ or greater indicating PJI; a reading below ++ should be followed by one of the laboratory-based synovial tests. If joint aspiration yields a dry tap, clinicians should rely on preoperative tissue culture and histological analysis for diagnosis. Combinations based on triage-conditional, arithmetic, and model-based prediction rules require further research.

LEVEL OF EVIDENCE

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

Neutrophil to lymphocyte ratio as a predictor for diagnosis of early Periprosthetic joint infection

Background

Periprosthetic joint infection (PJI) is a catastrophic complication after total knee or hip arthroplasty. The diagnosis of PJI is very difficult, especially in the early postoperative period. The value of the neutrophil to lymphocyte ratio (NLR) is useful for diagnosing infectious diseases. The objective of this study was to investigate the accuracy of the NLR for the diagnosis of early PJI after total knee or hip arthroplasty.

Methods

We retrospectively evaluated consecutive primary total knee or hip arthroplasty and identified the patients who readmitted within the first 90 days postoperatively between January 2011 and October 2018.There were 20 cases diagnosed early PJI and 101 uninfected cases on the basis of the modified Musculoskeletal Infection Society (MSIS) criteria. The serum parameters including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), white blood-cell (WBC) count, NLR and interleukin-6 (IL-6) were compared between the two groups. Receiver operating characteristic curves were generated to estimate the optimal cutoff values for each parameter. The sensitivity, specificity, positive predictive value and negative predictive value for each parameter were calculated.

Results

The CRP, ESR, WBC, NLR and IL-6 values were all significally higher in the infected group than the uninfected group. The median of CRP was 66.6 mg/l in the infected group and 8.6 mg/l in the uninfected group (p < 0.001). The median of ESR was 34.8 mm/hr. in the infected group and 17.4 mm/hr. in the uninfected group (p < 0.001). In the infected group and uninfected group, the median of WBC was 8.2X10⁹ /L and 6.1 X10⁹ /L (p = 0.002), respectively; while the median of NLR was 5.2 and 2.1 (p < 0.001). The median of IL-6 was 46 pg/ml and 6.4 pg/ml (p < 0.001),respectively. The best parameter for the diagnosis of early PJI was IL-6 (AUC = 0.814) followed by the NLR (AUC =0.802), CRP (AUC =0.793), ESR (AUC =0.744) and WBC (AUC = 0.632).

Conclusions

This study is the first to show that NLR values are more accurate than CRP and may be considered as useful parameters for the diagnosis of early PJI because it is a cheap and convenient parameter to be calculated in daily practice without extra costs.

Mildly decreased preoperative bilirubin levels are associated with infections after shoulder and knee arthroplasty

Increasing numbers of arthroplasties are also accompanied by postoperative infections. The main purpose was to evaluate preoperative serum bilirubin levels between patients with and without infections after shoulder and knee arthroplasties. For this retrospective case-control single-center study, a total of 108 patients were extracted from a prospectively collected database. Eighteen patients with infections after shoulder (n = 8) and knee (n = 10) arthroplasty were matched by age, gender, and implant type in a 1:5-scenario to 90 patients (40 shoulders and 50 knees) without postoperative infection. Demographic data, preoperative blood parameters, and postoperative infection-related outcomes were evaluated. Total bilirubin was the only preoperative parameter significantly different between the infection (8.21 ± 3.25 μmol/L or 0.48 ± 0.19 mg/dL) and noninfection (10.78 ± 4.62 μmol/L or 0.63 ± 0.27 mg/dL; P = .014) group, while C-reactive protein and other liver parameters were similar between the groups. Significantly more controls (92.1%) had preoperative bilirubin levels above 8.72 μmol/L or 0.51 mg/dL than cases (7.9%; P = .007). The 5-year infection survival-rate was 65.6% for patients with preoperative bilirubin levels < 8.72 μmol/L or < 0.51 mg/dL and 91.2% with ≥ 8.72 μmol/L or ≥ 0.51 mg/dL. Mildly decreased preoperative bilirubin levels with a cutoff at 8.72 μmol/L or 0.51 mg/dL were significantly associated to patients with infections after shoulder and knee arthroplasty. There were no differences in other blood parameters or comorbidities between patients with infections and their matched-controls.

Serum Fibrinogen Test Performs Well for the Diagnosis of Periprosthetic Joint Infection

BACKGROUND

Serum fibrinogen (FIB) is an acute-phase glycoprotein in the infection response that may stop excessive bleeding. The purposes of this study are to determine the value of FIB that can be used to differentiate between periprosthetic joint infection (PJI) and aseptic loosening of the prosthesis, and to determine the clinical significance of FIB for analyzing infection outcomes after first-stage surgery.

METHODS

This retrospective study included 90 patients undergoing total knee arthroplasty or total hip arthroplasty revision from January 2015 to August 2019. PJI was confirmed in 53 patients (group A), and the other 37 patients were diagnosed with aseptic loosening of the prosthesis (group B). Only 21 patients in group A documented the results for serum FIB, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) after spacer insertion, so the postoperative serological marker levels of the these patients were also assessed.

RESULTS

The FIB, CRP, and ESR levels were significantly higher in group A than in group B (P < .001). The area under the receiver operating characteristic curve was highest for FIB at 0.928. Analyses of FIB levels revealed a sensitivity of 79.25% and a specificity of 94.59%. FIB levels were significantly lower in patients with PJI after spacer insertion (P < .001).

CONCLUSION

FIB is an adequate test to aid in diagnosing PJI, and it is not inferior to CRP and ESR in distinguishing between PJI and aseptic loosening of the prosthesis. It is an especially useful tool in assessing infection outcomes after first-stage surgery.

The Performance of a Dithiothreitol-Based Diagnostic System in Diagnosing Periprosthetic Joint Infection Compared to Sonication Fluid Cultures and Tissue Biopsies

PURPOSE

The aim of this study was to evaluate the performance of a commercially available dithiothreitol (DTT) kit for routine use in diagnosing periprosthetic joint infections (PJIs) in comparison to conventional microbiological tissue specimens and sonication procedures in a maximal care hospital.

METHODS

We applied the DTT system in 40 consecutive cases of revision arthroplasty (23 PJIs and 17 aseptic revisions), with an exchange or a removal of components. The hardware components were split between the DTT system and the conventional sonication procedure. At least three tissue biopsies and a joint fluid specimen were sent for microbiological and histopathological analysis. Data was analysed retrospectively to compare between the different methods.

RESULTS

Cultures of the DTT fluid showed a sensitivity of 65% and specificity of 100%, as referenced to conventional microbiological cultures. Sonication had better sensitivity (75%) but lower specificity (85%). The categorical agreement of DTT cultures compared to sonication fluid cultures was 78% (31/40). Neither pathogen type, infection duration nor antibiotic pretreatment influenced the accuracy of the DTT, but a low pH in the DTT seemed to be associated with false-negative results.

CONCLUSION

DTT was inferior in sensitivity when diagnosing PJIs compared to sonication fluid cultures and tissue biopsies. A low pH in the DTT fluid correlated with false-negative results. Nevertheless, the closed system of the DTT kit avoids contamination and false-positive results, and DTT can be an alternative where sonication is not available.

The serum level of D-Dimer is not suitable for distinguishing between prosthetic joint infection and aseptic loosening

Background

To evaluate the meaning of serum CRP, ESR, and D-Dimer in the diagnosis of prosthetic joint infection.

Methods

In a retrospective study, 101 patients presented with osteoarthritis, PJI, and aseptic loosening were divided into three groups according to the type of operation they received in our department from June 2016 to December 2018: group A, 44 patients treated with primary arthroplasty; group B, 31 PJI patients treated with resection arthroplasty and spacer insertion surgery; group C, 26 aseptic loosening patients treated with revision arthroplasty. Data such as gender, age, preoperative serum CRP, ESR, and D-Dimer level were compared among the three different groups.

Results

There are no statistically significant differences when comparing general data such as gender and age in patients from the three different groups. However, Serum CRP level in group B (43.49 ± 10.00 mg/L) is significantly higher than in group A (2.97 ± 0.75 mg/L) and C (4.80 ± 1.26 mg/L). Serum ESR level in group B (49.84 ± 5.48 μg/L) is significantly higher than those in group A (15.28 ± 2.63 μg/L) and C (22.50 ± 3.47 μg/L). Serum D-Dimer level in group B (1.58 ± 0.17 μg/L) is significantly higher than that in group A (0.51 ± 0.50 μg/L), but similar with group C (1.22 ± 0.29 μg/L). There are no statistically significant differences when compared with sensitivity and specificity of CRP, ESR, and D-Dimer in the diagnosis of PJI among patients from the three different groups when D-Dimer > 0.85 μg/L was set as the optimal threshold value for the diagnosis of PJI.

Conclusion

D-Dimer is not a parameter to distinguish between aseptic loosening and PJI.

The Impact of α-Defensin Test in Diagnosing Periprosthetic Infection After Total Ankle Arthroplasty

Periprosthetic joint infection (PJI) after total ankle arthroplasty (TAA) is a serious complication, and a reliable diagnostic test to identify PJI is needed. The purpose of this study was to investigate the use of synovial α-defensin levels in identifying PJI of the ankle. Data from 33 patients were retrospectively collected between September 2015 and May 2018. Patients who had pain or suspected loosening after TAA and who had undergone joint aspiration were included in the study. Aspiration was performed in a semisterile theatre. Synovial fluid was processed in descending order for microbiological cultures, α-defensin, leukocyte esterase strip test, and cell count. A periprosthetic infection was defined by Musculoskeletal Infection Society criteria. The sensitivity, specificity, and overall accuracy were calculated, and based on a receiver operating characteristic curve, the quality of the α-defensin test was determined. The calculated area under the curve was 0.97 ± 0.32. Two of 33 patients fulfilled the 2014 Musculoskeletal Infection Society criteria and were scheduled for septic revision arthroplasty. Sensitivity, specificity, and overall accuracy of the α-defensin test were 100% (95% confidence interval [CI], 15.8% to 100%), 93.5% (95% CI, 78.6% to 99.2%), and 93.9% (95% CI, 79.8% to 99.3%), respectively. The positive predictive value was 50% (95% CI, 20.7% to 79.3%), and the negative predictive value was 100%. The α-defensin test seems to be the best available synovial test to detect a late-onset PJI after total ankle arthroplasty. Further prospective studies with a larger number of patients are required.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

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

Comparison of two-stage revision arthroplasty and intramedullary arthrodesis in patients with failed infected knee arthroplasty

BACKGROUND

Failed total knee arthroplasty (TKA) with significant bone loss and compromised soft-tissues is challenging and the final results are often inferior to patient's expectation. The objective of this study was to present a comparison of outcomes in patients with failed infected TKA treated with two-stage revision TKA or knee arthrodesis and to assess clinical and functional results, implant survival and infection recurrence. The hypothesis was that an arthrodesis may result in beneficial effects on patients' outcome.

METHODS

Clinical data of 81 patients with periprosthetic joint infection (PJI) of the knee joint were collected and analyzed retrospectively. Between 2008 and 2014, a total of 36 patients had been treated within a two-stage exchange procedure and reimplantation of a modular intramedullary arthodesis nail and 45 patients with revision TKA. Patients were treated according to the same structured treatment algorithm. Clinical and functional evaluation was performed using the Oxford knee score (OKS) and the visual analogue scale (VAS).

RESULTS

The mean follow-up was 32.9 ± 14.0 months. The rate of definitely free of infection at last follow-up in the arthrodesis group was 32 of 36 (88.9%) and 36 of 45 (80.0%) in the revision TKA group (p = 0.272). Mean VAS for pain in the arthrodesis group was 3.1 ± 1.4 compared to 3.2 ± 1.6 in the revision TKA group (p = 0.636). The OKS in the arthrodesis group was 38.7 ± 8.9 and 36.5 ± 8.9 (p = 0.246) in patients with revision TKA. Rate of revisions in the revision-TKA group was 2.8 ± 3.7 compared to 1.2 ± 2.4 in the arthrodesis group (p = 0.021).

CONCLUSION

Treatment of PJI needs a distinct therapy with possible fallback strategies in case of failure. A knee arthrodesis is a limb salvage procedure that showed no significant benefits on the considered outcome factors compared to revision TKA but is associated with significantly lower revision rate. After exhausted treatment modalities, a knee arthrodesis should be considered as an option in selected patients.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Serum biomarkers in periprosthetic joint infections

OBJECTIVES

The diagnosis of periprosthetic joint infection (PJI) is difficult and requires a battery of tests and clinical findings. The purpose of this review is to summarize all current evidence for common and new serum biomarkers utilized in the diagnosis of PJI.

METHODS

We searched two literature databases, using terms that encompass all hip and knee arthroplasty procedures, as well as PJI and statistical terms reflecting diagnostic parameters. The findings are summarized as a narrative review.

RESULTS

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were the two most commonly published serum biomarkers. Most evidence did not identify other serum biomarkers that are clearly superior to ESR and CRP. Other serum biomarkers have not demonstrated superior sensitivity and have failed to replace CRP and ESR as first-line screening tests. D-dimer appears to be a promising biomarker, but more research is necessary. Factors that influence serum biomarkers include temporal trends, stage of revision, and implant-related factors (metallosis).

CONCLUSION

Our review helped to identify factors that can influence serum biomarkers' level changes; the recognition of such factors can help improve their diagnostic utility. As such, we cannot rely on ESR and CRP alone for the diagnosis of PJI prior to second-stage reimplantation, or in metal-on-metal or corrosion cases. The future of serum biomarkers will likely shift towards using genomics and proteomics to identify proteins transcribed via messenger RNA in response to infection and sepsis.Cite this article:Bone Joint Res 2018;7:85-93.

Two-stage knee arthrodesis with a modular intramedullary nail due to septic failure of revision total knee arthroplasty with extensor mechanism deficiency

BACKGROUND

Periprosthetic joint infection is a serious complication and reconstruction after failed revision total knee arthroplasty with significant bone loss and compromised soft-tissues can be challenging. Objective of this study was to assess clinical and functional results, implant survival and infection recurrence rates in patients treated with two-stage arthrodesis after failed revision TKA with extensor mechanism deficiencies due to PJI, and to identify the factors that affect outcomes after surgery.

METHODS

Thirty seven patients with PJI treated within a two-stage exchange and reimplantation of an arthrodesis nail between 2008 and 2014 were included. Systemic and local risk factors were graded preoperatively according to McPherson et al. All patients were treated according to a structured treatment algorithm. Clinical and functional evaluation was performed using the Oxford Knee Score and the Visual Analogue Scale.

RESULTS

Thirty two of 37 patients (86.5%) were graded as free of infection. Five patients (13.5%) had recurrent infection after arthrodesis with the need of revision surgery. Mean leg-length discrepancy was 2.2cm. The mean VAS for pain was three, the mean Oxford Knee Score was 38±9. Total implant survival at a 74month follow-up was 74.3% (95% CI: 45.4 to 91.1%), as determined by Kaplan-Meier survival curves. Local McPherson Score, as well as number of revisions was found to be of significant influence to the survival rate.

CONCLUSIONS

Septic failure of revision knee arthroplasty can be effectively treated with two-stage arthrodesis using a modular intramedullary nail, providing a stable and painless limb with satisfactory functional results and acceptable infection eradication rates.

RANK-ligand and osteoprotegerin as biomarkers in the differentiation between periprosthetic joint infection and aseptic prosthesis loosening

AIM

To assess serum levels of RANK-ligand (RANKL) and osteoprotegerin (OPG) as biomarkers for periprosthetic joint infection (PJI) and compare their accuracy with standard tests.

METHODS

One hundred and twenty patients presenting with a painful total knee or hip arthroplasty with indication for surgical revision were included in this prospective clinical trial. Based on standard diagnostics (joint aspirate, microbiological, and histological samples) and Musculoskeletal Infection Society consensus classification, patients were categorized into PJI, aseptic loosening, and control groups. Implant loosening was assessed radiographically and intraoperatively. Preoperative serum samples were collected and analyzed for RANKL, OPG, calcium, phosphate, alkaline phosphatase (AP), and the bone-specific subform of AP (bAP). Statistical analysis was carried out, testing for significant differences between the three groups and between stable and loose implants.

RESULTS

All three groups were identical in regards to age, gender, and joint distribution. No statistically significant differences in the serum concentration of RANKL (P = 0.16) and OPG (P = 0.45) were found between aseptic loosening and PJI, with a trend towards lower RANKL concentrations and higher OPG concentrations in the PJI group. The RANKL/OPG ratio was significant for the comparison between PJI and non-PJI (P = 0.005). A ratio > 60 ruled out PJI in all cases (specificity: 100%, 95%CI: 89, 11% to 100.0%) but only 30% of non-PJI patients crossed this threshold. The positive predictive value remained poor at any cut-off. In the differentiation between stable and loose implants, none of the parameters measured (calcium, phosphate, AP, and bAP) showed a significant difference, and only AP and bAP measurements showed a tendency towards higher values in the loosened group (with P = 0.09 for AP and P = 0.19 for bAP).

CONCLUSION

Lower RANKL and higher OPG concentrations could be detected in PJI, without statistical significance.

Comparison of bacterial growth in sonication fluid cultures with periprosthetic membranes and with cultures of biopsies for diagnosing periprosthetic joint infection

Total joint arthroplasty is a common operation worldwide with infection rates between 1% and 3%. In cases of suspected periprosthetic joint infection, it is very challenging to rule out the causative microorganisms. In this study, we compared the appearance of periprosthetic membranes with the microbiological results obtained from cultures of sonication fluid and the correlation between classical microbiological cultures and cultures of sonication fluid. The results confirmed a strong correlation of bacterial growth in sonication fluid cultures with bacterial growth in classical microbiological cultures. Most importantly, however, our study documented a highly significant correlation of periprosthetic membranes typical for periprosthetic joint infection (PJI) with bacterial growth in sonication fluid. Sonication fluid cultures yielded a better sensitivity than tissue cultures (72.34-60.87%). These 3 methods are useful tools in diagnosing PJIs, and even more, sonication fluid cultures should be included in the diagnostic path of PJI.

Identification of periprosthetic joint infection after total hip arthroplasty

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

Investigation of neutrophilic peptides in periprosthetic tissue by matrix-assisted laser desorption ionisation time-of-flight imaging mass spectrometry

PURPOSE

The accurate diagnosis of periprosthetic joint infection (PJI) relies on clinical investigation, laboratory parameters, radiological methods, sterile joint aspiration for synovial fluid leucocyte count and microbiological analysis and tissue sampling for histopathology. Due to the limits in specificity and sensitivity of these methods, molecular techniques and new biomarkers were introduced into the diagnostic procedure. Histological examination is related to the amount of neutrophils in the periprosthetic tissue in frozen sections and formalin-fixed paraffin embedded material (FFPE). However, the threshold of neutrophils per defined area of tissue among various studies is very inconsistent.

METHODS

We have applied matrix-assisted laser desorption ionisation time-of-flight imaging mass spectrometry (MALDI IMS) to a total of 32 periprosthetic tissue samples of patients with PJI to detect peptides associated with areas of neutrophil infiltration.

RESULTS

Specific peaks associated with a high amount of neutrophils were detected. Of these m/z peaks, four could be assigned to predictive neutrophil molecules. These peptides include annexin A1, calgizzarin (S100A11), calgranulin C (S100A12) and histone H2A. By MALDI IMS, these peptides could be shown to be co-localised with the infiltration of neutrophils in the immediate vicinity of the periprosthetic interface, whereas more distant areas did not show neutrophil invasion or infection-related peptides.

CONCLUSIONS

MALDI IMS is a new method allowing identification of neutrophil peptides in periprosthetic tissues and may be a surrogate for counting neutrophils as an objective parameter for PJI.