Synovial Biomarkers to Detect Chronic Periprosthetic Joint Infection: A Pilot Study to Compare Calprotectin Rapid Test,Calprotectin ELISA Immunoassay and Leukocyte Esterase Test

BackgroundPeriprosthetic joint infection (PJI) is a devastating complication after joint replacement surgery, and making diagnosis is often far from obvious. Calprotectin was recently proposed as a promising synovial biomarker to detect PJI. To our knowledge, no comparative study exists between enzyme-linked immunosorbent assay (ELISA) and rapid calprotectin test (CalFAST). Our purpose was to compare these methods with leukocyte esterase (LE) test from synovial fluid of painful knee arthroplasty subjected to infectious workup.MethodsNinety-three patients were included in this prospective observational study. They underwent synovial fluid aspiration that was analyzed for cell count, microbiological culture, LE test, calprotectin rapid test, and calprotectin immunoassay dosage. The 2018 Consensus Statements criteria for PJI were used to diagnose PJI. Sensitivity, specificity, positive and negative likelihood ratio, and receiver operating characteristic were calculated for detection methods and compared.ResultsWe categorized 39 patients as infected and 50 patients as not infected. The sensitivity comparing the ELISA test and CalFAST test was similar, 92.3% and 97.4%, respectively. LE rapid test showed 46% of sensitivity and 94% of specificity. The highest specificity was found with ELISA test (100%). Comparing the receiver operating characteristic curves by z-test, there were statistically significant differences between LE strip test and the other two methods. Otherwise, no statistically significant differences were present between ELISA and CalFAST test.ConclusionSynovial calprotectin detection has high accuracy in knee PJI diagnosis, both ELISA and rapid test. LE strip test remains a good test to confirm the diagnosis of PJI in case of positivity. In clinical practice, the calprotectin rapid test can be considered an excellent point-of-care test.     

Which International Consensus Meeting Preoperative Minor Criteria is the Most Accurate Marker for the Diagnosis of Periprosthetic Joint Infection in Hip and Knee Arthroplasty?

BackgroundThe accurate preoperative diagnosis of periprosthetic joint infection (PJI) is critical. The aim of this study was to evaluate the diagnostic accuracy and performance of the 2018 International Consensus Meeting (ICM) preoperative minor criteria for the diagnosis of chronic PJI in total hip and knee arthroplasty.MethodsWe retrospectively reviewed 260 patients that underwent a revision knee or hip arthroplasty at our institution between 2015 and 2017. All major and minor 2018 ICM criteria (except erythrocyte sedimentation rate, D-dimer) were available for all patients included. Cases with at least 1 major criterion were considered as infected. Receiver operative characteristic curve analysis was performed for preoperative minor criteria.ResultsThe diagnostic performance of the preoperative minor criteria ranked as per the area under the curve was PMN% (0.926), alpha defensin (0.922), white blood cell count (0.916), leukocyte esterase (0.861), and serum C-reactive protein (0.860). Increasing the PMN % cutoff from 70% to 77.8% improves the diagnostic accuracy (86.5% vs 90.8%). The highest diagnostic performance was achieved by combining all 5 preoperative parameters, and at current ICM thresholds, the diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive were 93.5%, 95.4%, 92.1%, 89.7%, and 96.5%, respectively.ConclusionThe diagnostic performance of preoperative minor criteria was outstanding (PMN%, alpha defensin, white blood cell count) or excellent (leukocyte esterase, serum C-reactive protein). PMN% showed the best diagnostic utility (area under the curve) and should have an increased weight-adjusted score in the ICM scoring system.     

The Utility of Frozen Section Histology in Diagnosing Periprosthetic Joint Infection in Revision Total Joint Arthroplasty

BackgroundSurgeons utilize a combination of preoperative tests and intraoperative findings to diagnose periprosthetic joint infection (PJI); however, there is currently no reliable diagnostic marker that can be used in isolation. The purpose of our study is to evaluate the utility of frozen section histology in diagnosis of PJI.MethodsRetrospective analysis of 614 patients undergoing revision total joint arthroplasty with frozen section histology from a single institution was performed. Discriminatory value of frozen section histology was assessed using univariate analysis and evaluation of area under the curve (AUC) of a receiver operating characteristic curve comparing frozen section histology results to the 2018 International Consensus Meeting (ICM) PJI criteria modified to exclude the histology component.ResultsThe sensitivity of the frozen section histology was 53.6% and the specificity was 95.2%. There was 99.2% concordance between the permanent section and frozen section results. The receiver operating characteristic curve for frozen section yielded an AUC of 0.744 (95% confidence interval 0.627-0.860) and the modified ICM score yielded an AUC of 0.912 (95% confidence interval 0.836-0.988) when compared to the full score. The addition of frozen section histology changed the decision to infected in 20% of “inconclusive” cases but less than 1% of total cases.ConclusionIn comparison to the modified ICM criteria, intraoperative frozen section histology has poor sensitivity, strong specificity, and acceptable overall discrimination for diagnosing PJI. This test appears to be of particular value for patients deemed “inconclusive” for infection using the remaining ICM criteria.     

The 2018 International Consensus Meeting Minor Criteria for Chronic Hip and Knee Periprosthetic Joint Infection: Validation From a Single Center

BackgroundRecently, a revised definition of the minor criteria scoring system for diagnosing periprosthetic joint infection (PJI) was developed by the second International Consensus Meeting on musculoskeletal infection. The new system combines preoperative and intraoperative findings, reportedly achieving high sensitivity and specificity. We aimed to validate the modified scoring system at a high-volume center.MethodsWe retrospectively reviewed patients who underwent a revision total hip or knee arthroplasty at our institution from May 2015 to August 2018. Serum C-reactive protein, synovial white blood cell count and polymorphonuclear percentage, leukocyte esterase test, alpha-defensin, microbiological and histologic results, and documented existence of sinus tract and intraoperative purulence were available for all patients. Cases with at least 1 major criterion were considered as infected. Using the new minor criteria, a score of ≥6 reflects PJI, while a score <3 can be considered as noninfected. Sensitivity, specificity, mean accuracy (ACC), positive predictive value (PPV), and negative predictive value (NPV) were analyzed.ResultsA total of 345 cases were included. A cutoff score of ≥6 points had the following diagnostic performance: area under the curve (AUC) = 0.90; ACC = 0.88; sensitivity = 0.96; specificity = 0.84; PPV = 0.70; NPV = 0.98. Diagnostic performance was better for the hip (AUC = 0.92; ACC = 0.90; sensitivity = 0.96; specificity = 0.86; PPV = 0.81; NPV = 0.98) than the knee (AUC = 0.89; ACC = 0.85; sensitivity = 0.95; specificity = 0.83; PPV = 0.59; NPV = 0.98).ConclusionThe modified scoring system proposed by the 2018 International Consensus Meeting in diagnosing PJI showed high sensitivity and a good performance, especially as rule-out diagnostic criteria. The cutoff level seems to be different between the hip and knee. Further validation studies considering the acknowledged limitations are recommended.     

Calprotectin Lateral Flow Test: Consistent Across Criteria for Ruling Out Periprosthetic Joint Infection

BackgroundThere are multiple sets of criteria used to define periprosthetic joint infection. The objective of this study is to compare the diagnostic accuracy of the calprotectin lateral flow point-of-care (POC) test in total knee arthroplasty (TKA) patients to diagnose infection using 3 different sets of criteria: (1) 2013 Musculoskeletal Infection Society, (2) 2018 Intentional Consensus Meeting (ICM), and (3) the 2019 proposed European Bone and Joint Infection Society criteria as reference standards.MethodsFrom October 2018 to January 2020, 123 intraoperative synovial fluid samples were prospectively collected from revision total knee arthroplasty patients and tested using a calprotectin lateral flow POC assay. Data were reviewed and adjudicated by 2 independent reviewers blinded to calprotectin test results.ResultsThe 3 criteria sets had 91.8% agreement. Using 2013 Musculoskeletal Infection Society criteria, the POC test demonstrated a sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of 98.1%, 95.7%, 94.5%, 98.5%, and 0.969, respectively. Using the 2018 ICM, the POC test demonstrated a sensitivity, specificity, PPV, NPV, and AUC of 98.2%, 98.5%, 98.2%, 98.5%, and 0.984, respectively. Using the 2019 proposed European Bone and Joint Infection Society criteria, the POC test demonstrated a sensitivity, specificity, PPV, NPV, and AUC of 93.2%, 100.0%, 100.0%, 94.2%, and 0.966, respectively.ConclusionThe calprotectin lateral flow POC test had excellent sensitivity and specificity across current available periprosthetic joint infection definitions, with the best performance observed when applying 2018 ICM criteria.Level of EvidenceDiagnostic I.     

What Is the Optimal Timing for Reading the Leukocyte Esterase Strip for the Diagnosis of Periprosthetic Joint Infection?

BackgroundThe leucocyte esterase (LE) strip test often is used to diagnose periprosthetic joint infection (PJI). In accordance with the manufacturer’s directions, the LE strip test result is read 3 minutes after exposing it to joint fluid, but this has not been supported by robust research. Moreover, we have noted that the results of the LE strip test might change over time, and our previous studies have found that centrifugation causes the results of the LE strip test to degrade. Still, there is no evidence-based recommendation as to when to read the LE strip test to maximize diagnostic accuracy, in general, and the best reading times for the LE strip test before and after centrifugation need to be determined separately, in particular.Questions/purposes(1) What is the optimal timing for reading LE strip test results before centrifugation to diagnose PJI? (2) What is the optimal timing for reading LE strip test results after centrifugation to diagnose PJI?MethodsThis study was a prospective diagnostic trial. In all, 120 patients who were scheduled for revision arthroplasty and had signs of infection underwent joint aspiration in the outpatient operating room between July 2018 and July 2019 and were enrolled in this single-center study. For inclusion, patients must have had a diagnosis of PJI or nonPJI, valid synovial fluid samples, and must not have received antibiotics within 2 weeks before arthrocentesis. As such, 36 patients were excluded; 84 patients were included for analysis, and all 84 patients agreed to participate. The 2018 International Consensus Meeting Criteria (ICM 2018) was used for the classification of 49 patients with PJI (score ≥ 6) and 35 without PJI (score ≤ 2). The classification was used as the standard against which the different timings for reading LE strips were compared. All patients without PJI were followed for more than 1 year, during which they did not report the occurrence of PJI. All patients were graded against the diagnostic criteria regardless of their LE strip test results. In 83 patients, one drop of synovial fluid (50 μL) was applied to LE strips before and after centrifugation, and in one patient (without PJI), the sample was not centrifuged because the sample volume was less than 1.5 mL. The results of the strip test were read on an automated colorimeter. Starting from 1 minute after centrifugation, these strips were automatically read once every minute, 15 times (over a period of 16 minutes), and the results were independently recorded by two observers. Results were rated as negative, ±, 1+, and 2+ upon the machine reading. Grade 2+ (dark purple) was used as the threshold for a positive result. An investigator who was blinded to the study performed the statistics. Optimal timing for reading the LE strip before and after centrifugation was determined by using receiver operative characteristic (ROC) analysis. The specificity, sensitivity, and positive predictive and negative predictive values were calculated for key timepoints.ResultsBefore centrifugation, the area under the curve was the highest when the results were read at 5 minutes (0.90 [95% CI 0.83 to 0.98]; sensitivity 0.88 [95% CI 0.75 to 0.95]; specificity 0.89 [95% CI 0.72 to 0.96]). After centrifugation, the area under the curve was the highest when the results were read at 10 minutes (0.92 [95% CI 0.86 to 0.98]; sensitivity 0.65 [95% CI 0.50 to 0.78]; specificity 0.97 [95% CI 0.83 to 1.00]).ConclusionThe LE strip test results are affected by time and centrifugation. For samples without centrifugation, we found that 5 minutes after application was the best time to read LE strips. We cannot deny the use of centrifuges because this is an effective way to solve the sample-mingling problem at present. We recommend 10 minutes postapplication as the most appropriate time to read LE strips after centrifugation. Multicenter and large–sample size studies are warranted to further verify our conclusion.Level of EvidenceLevel II, diagnostic study.     

Synovial Fluid Calprotectin for the Preoperative Diagnosis of Chronic Periprosthetic Joint Infection

BackgroundThe diagnosis of periprosthetic joint infection (PJI) represents a challenge in clinical practice and the analysis of synovial fluid is a useful diagnostic tool. Calprotectin is an inflammatory biomarker widely used in the evaluation of chronic inflammatory diseases; however, little is known about its role in PJI. The purpose of this study is to determine the reliability of synovial calprotectin in the diagnosis of PJI.MethodsSeventy-six patients with painful knee arthroplasty were included in this prospective observational study. Synovial fluid was analyzed for cell count, percentage of polymorphonuclear neutrophils, microbiological culture, leukocyte esterase strip test, alpha-defensin rapid test, and calprotectin immunoassay dosage. The 2018 Consensus Statements criteria for PJI were used as standard reference to define the presence of infection. Sensitivity, specificity, positive and negative likelihood ratio, and receiver-operation characteristic curve were calculated for calprotectin immunoassay test.ResultsBy 2018 Consensus Statements criteria for PJI, 28 patients were considered infected, 44 patients were considered not infected, and 4 patients were classified as inconclusive. The calprotectin synovial fluid test resulted in 2 false-positive results and no false-negative results. The calprotectin synovial fluid test demonstrated a sensitivity of 100% (95% confidence interval [CI] 99.96-100) and specificity of 95% (95% CI 89.4-100) for the diagnosis of PJI. The positive likelihood ratio was 22 (95% CI 5.680-85.209) and the negative likelihood ratio was 0 (95% CI 0-0.292). The area under the receiver-operation characteristic curve was 0.996 (95% CI 94.3-100).ConclusionThe present study suggests that synovial calprotectin immunoassay test has a high sensitivity and specificity in the diagnosis of knee PJI. Moreover, it is easily applied, quick and valuable in clinical practice.     

The Leukocyte Esterase Strip Test has Practical Value for Diagnosing Periprosthetic Joint Infection After Total Knee Arthroplasty: A Multicenter Study

Background

Leukocyte esterase (LE) was recently reported to be an accurate marker for diagnosing periprosthetic joint infection (PJI) as defined by the Musculoskeletal Infection Society (MSIS) criteria. However, the diagnostic value of the LE test for PJI after total knee arthroplasty (TKA), the reliability of the subjective visual interpretation of the LE test, and the correlation between the LE test results and the current MSIS criteria remain unclear.

Applying the new shoulder periprosthetic joint infection consensus definition to a case series of revision shoulder arthroplasty procedures to assess concordance between consensus definitions and diagnoses

PurposeAs the number of shoulder arthroplasty procedures performed rises yearly, so does the number of periprosthetic joint infections (PJIs). In this study, PJI consensus definitions were compared and contrasted in a series of revision shoulder arthroplasty cases preoperatively diagnosed as PJI. Understanding the variations in these definitions may guide PJI diagnoses, thereby improving treatment strategies and patient outcomes in the setting of infected shoulder arthroplasty.MethodsAll revision shoulder arthroplasty cases with preoperatively-diagnosed or suspected PJI (determined by procedure code) performed from 2008 – 2017 at a single institution by a single surgeon (fellowship-trained in shoulder and elbow surgery) were retrospectively evaluated. Following Institutional Review Board approval, patient demographic, treatment, and laboratory data were collected. Musculoskeletal Infection Society (MSIS; 2011) and International Consensus Meeting on Orthopaedic Infections (ICM; 2013, 2018 Revision, 2018 Shoulder) definitions of PJI were applied to the data. Statistical analysis assessed significant associations between culture status and PJI classification algorithm criteria.ResultsThirty-seven patients with suspected PJI were identified; 24 culture-positive (CP) and 13 culture-negative (CN). In this series, the 2018 ICM Shoulder definition for definite infection was met at lower rates than all other definitions (CP; 71% vs. 96%; CN; 62% vs. 69%). 2018 ICM Shoulder major criteria showed stronger correlations to 2011 MSIS, 2013 ICM, and 2018 ICM Revision major criteria when “gross intra-articular pus” was excluded than when pus was included as a major criterion. 2018 ICM Revision cases determined to be infected were very strongly, positively, correlated with the 2018 ICM Shoulder cases determined to have definite or probable infections (ρ = 1.000, P < .0001). Additionally, cases classified as “definite” or “probable” infections with the 2018 ICM Shoulder definition were more likely to require reoperation for suspected recurrent infection after completion of antibiotic therapy.ConclusionsIn this series, the 2018 ICM Shoulder definition and previous PJI definitions classified cases as PJI at similar rates. However, the inclusion of a third major criterion of “gross intra-articular pus” weakened the correlation with prior definitions.Level of evidenceLevel IV; Case Series.     

Accuracy of the International Consensus Scoring System for diagnosis of periprosthetic joint infection in revision shoulder arthroplasty

BackgroundTotal shoulder arthroplasty (TSA) continues to undergo dramatic growth with expanding indications and improvements in implants and surgical techniques. A major complication following TSA is periprosthetic joint infection (PJI), which remains difficult to diagnose, often relying on clinical judgment. A contemporary definition of PJI was established at the 2018 International Consensus Meeting (ICM) on Musculoskeletal Infection. We sought to retrospectively examine the accuracy of this scoring system in previously performed revision TSA and hypothesized that the ICM scoring system would be reliable in determining the presence of TSA PJI.MethodsOur institutional database was reviewed to identify patients undergoing revision TSA before the advent of the ICM PJI scoring system. Clinical notes and operative reports were reviewed for data regarding the preoperative clinical examination, laboratory values, and intraoperative findings. The findings were assigned scores based on the definition of probable PJI by the ICM scoring system. Scores were compared to treatment plans of infected vs. noninfected patients. The diagnosis of PJI was made using a combination of clinical examination, laboratory values, and intraoperative findings. Sensitivity, specificity, positive and negative predictive values, and accuracy of the ICM scoring system were calculated compared to actual treatment decision, the gold standard.ResultsOf 81 revision arthroplasties, 52 were revision reverse TSA (rTSA), and 29 were revision anatomic TSA (aTSA). Seven rTSA patients were treated as infected (7/52, 13.5%), and the scoring system identified 4 of those as being probable infections (4/7, 57.1%). One additional rTSA patient scored as probable infection, underwent a revision for instability, and was found to have no infection. Three aTSA patients were treated as infected (3/29, 10.3%), with one of those identified as probable infection by the scoring system (1/3, 33.3%). Four patients in the rTSA group and no patients in the aTSA group met the criteria for definite infection. Using the threshold of probable infection to identify PJI, the sensitivity of the scoring system was 0.6, and specificity was 0.99. The positive predictive value was 0.86, and the negative predictive value was 0.95. With the same threshold, the ICM scoring system was 93.8% accurate.ConclusionsIdentifying PJI in TSA remains difficult in the absence of definite signs of joint sepsis. This study found the scoring system to be highly accurate, although with modest sensitivity, and a reliable tool for the diagnosis of PJI following TSA.Level of evidenceLevel IV; Retrospective Case Series with No Comparison Group Treatment Study     

The Utility of Serum d-Dimer for the Diagnosis of Periprosthetic Joint Infection in Revision Total Hip and Knee Arthroplasty

BackgroundThere is scarce and contradicting evidence supporting the use of serum d-dimer for the diagnosis of periprosthetic joint infection in revision total hip (THA) and knee (TKA) arthroplasty. Therefore, the purpose of this study is to test the accuracy of serum d-dimer against the 2013 International Consensus Meeting (ICM) criteria.MethodsA retrospective review was performed on a consecutive series of 172 revision THA/TKA surgeries performed by 3 fellowship-trained surgeons at a single institution (August 2017 to May 2019) and that had d-dimer performed during their preoperative workup. Of this cohort, 111 (42 THAs/69 TKAs) cases had complete 2013 ICM criteria tests and were included in the final analysis. Septic and aseptic revisions were categorized per 2013 ICM criteria (“gold standard”) and compared against serum d-dimer using an established threshold (850 ng/mL). Sensitivity, specificity, likelihood ratios, and positive/negative predictive values were determined. Independent t-tests, Fisher’s exact tests, chi-squared tests, and receiver operating characteristic curve analysis were performed.ResultsThere was no statistically significant difference in baseline demographics between septic and aseptic cases per 2013 ICM criteria. When compared to ICM criteria, d-dimer demonstrated high sensitivity (95.9%) and negative predictive value (90.9%) but low specificity (32.3%), positive predictive value (52.8%), and overall, poor accuracy (61%) to diagnose periprosthetic joint infection. Positive likelihood ratio was 1.42 while negative likelihood ratio was 0.13. The area under the curve (AUC) was 0.742.ConclusionSerum d-dimer has poor accuracy to discriminate between septic and aseptic cases using a described threshold in the setting of revision THA and TKA.     

The Performance of Diagnostic Tests for Identifying Periprosthetic Joint Infection After Failed Partial Knee Arthroplasty

BackgroundIndications for unicompartmental knee arthroplasty (UKA) and patello-femoral arthroplasty are expanding. Despite the lower published infection rates for UKA and patello-femoral arthroplasty than total knee arthroplasty, periprosthetic joint infection (PJI) remains a devastating complication and diagnostic thresholds for commonly utilized tests have not been investigated recently. Thus, this study evaluated if diagnostic thresholds for PJI in patients who had a failed partial knee arthroplasty (PKA) align more closely with previously reported thresholds specific to UKA or the 2018 International Consensus Meeting on Musculoskeletal Infection.MethodsWe identified 109 knees in 100 patients that underwent PKA with eventual conversion to total knee arthroplasty within a single healthcare system from 2000 to 2021. Synovial fluid nucleated cell count and synovial polymorphonuclear percentage in addition to preoperative serum erythrocyte sedimentation rate, serum C-reactive protein, and serum white blood cell count were compared with Student’s t-tests between septic and aseptic cases. Receiver operating characteristic curves and Youden’s index were used to assess diagnostic performance and the optimal cutoff point of each test.ResultsSynovial nucleated cell count, synovial polymorphonuclear percentage, and serum C-reactive protein demonstrated excellent discrimination for diagnosing PJI with an area under the curve of 0.97 and lower cutoff values than the previously determined UKA specific criteria. Serum erythrocyte sedimentation rateESR demonstrated good ability with an area under the curve of 0.89.ConclusionSerum and synovial fluid diagnostic thresholds for PJI in PKAs align more closely with the thresholds established by the 2018 International Consensus Meeting as compared to previously proposed thresholds specific to UKA.Level of EvidenceLevel III, retrospective comparative study.     

Application of the ICM diagnostic criteria for shoulder periprosthetic joint infection

BackgroundDiagnosis for shoulder periprosthetic infection (PJI) is a challenge in shoulder arthroplasty. The 2018–2019 International Consensus Meeting (ICM) on Orthopedic Infections created a scoring system with minor and major criteria for shoulder PJI. The purpose of this study was to apply these criteria in a cohort of suspected shoulder PJI cases and assess their treatment course.MethodsAn institutional database was used to query TSA patients from January 2013 to May 2019. Patients for revision shoulder arthroplasty were stratified into groups based on the ICM criteria with four main groups: unlikely PJI, possible PJI, probable PJI, and definite PJI. Each patient included was assessed for baseline demographics, Elixhauser co-morbidities (ECM), prior hardware, timing of infection, treatment type, reinfection incidence at one-year, length of hospitalization and 90-day readmission.ResultsA total of 43 patients were identified. After applying ICM criteria for diagnosis of shoulder PJI, there were 16 cases of unlikely PJI, 15 cases of possible PJI, 5 cases of probable PJI and 7 cases of definite PJI. Comparison of baseline characteristics including age (p = 0.23), BMI (p = 0.62), ASA (p = 0.53) reveled no significant differences between each ICM group. C. acnes was not found in any case of definite PJI. Definite PJI had the highest LOS at 2.6 days, p = 0.04. Revision for PJI that was classified as definite infection demonstrated the highest rate of reinfection at 1-year (28.6%) (p = 0.02).ConclusionICM criteria represent an accurate and reliable tool for defining shoulder PJI. Moreover, the criteria appear to demonstrate a higher risk of reinfection in the definite PJI group. Based on these findings, we recommend careful consideration of treatment strategies due to higher risk for reinfectionLevel of evidenceLevel IV; Retrospective Cohort.     

Clinical Evaluation of Alpha Defensin Test Following Staged Treatment of Prosthetic Joint Infections

BackgroundDiagnosing persistent infection following staged treatment of prosthetic joint infection (PJI) is challenging. The alpha defensin (AD) test has been shown to be an accurate diagnostic test for the primary diagnosis PJI but has limited evaluation for use following a staged treatment of PJI. The goal of this study was to evaluate the diagnostic accuracy of AD testing following staged treatment of PJI before reimplantation surgery and to determine if negative AD test predicted success following reimplantation using Delphi Criteria at time of last follow-up.MethodsPatients who underwent AD testing prior to reimplantation after staged treatment of PJI (n = 52) were reviewed. Preoperative data (AD result, synovial fluid [SF], C-reactive protein level [mg/L], SF culture, SF white blood cell count, % of polymorphonuclear lymphocytes, serum C-reactive protein/erythrocyte sedimentation rate) and intraoperative data (purulence and tissue culture) were reviewed and used to classify patients using 2018 Musculoskeletal Infectious Disease Society criteria for infection, which was then used as a gold standard test to calculate diagnostic accuracy.Chart review was used to determine if patients who underwent reimplantation surgery would go on to treatment failure as defined by Delphi Criteria.ResultsThe sensitivity and specificity of AD test result as compared with Musculoskeletal Infectious Disease Society criteria in diagnosing PJI was calculated to be 71% and 97.78%. Positive predictive value was calculated to be 83.3%, and negative predictive value was calculated to be 95.65%.Patients who underwent reimplantation (46/52 patients) all had negative AD test results, and 9/46 or 19.5% would have treatment failure as defined by the Delphi Criteria with an average follow-up of 588 days.ConclusionAD demonstrates high specificity and negative predictive value, with low sensitivity when utilized after staged treatment of PJI. Further investigation of this and other diagnostic tests following staged treatment of PJI is needed. Additionally, validated criteria used to identify persistent infection following staged treatment of PJI are required.     

Tobacco Use and Risk of Wound Complications and Periprosthetic Joint Infection: A Systematic Review and Meta-Analysis of Primary Total Joint Arthroplasty Procedures

Background

The purpose of this study was to perform a systematic review and meta-analysis to quantitatively assess the association between tobacco use and the risk of any wound complication and periprosthetic joint infection (PJI) after primary total hip and total knee arthroplasty procedures.

Automated Detection of Periprosthetic Joint Infections and Data Elements Using Natural Language Processing

BackgroundPeriprosthetic joint infection (PJI) data elements are contained in both structured and unstructured documents in electronic health records and require manual data collection. The goal of this study is to develop a natural language processing (NLP) algorithm to replicate manual chart review for PJI data elements.MethodsPJI was identified among all total joint arthroplasty (TJA) procedures performed at a single academic institution between 2000 and 2017. Data elements that comprise the Musculoskeletal Infection Society (MSIS) criteria were manually extracted and used as the gold standard for validation. A training sample of 1208 TJA surgeries (170 PJI cases) was randomly selected to develop the prototype NLP algorithms and an additional 1179 surgeries (150 PJI cases) were randomly selected as the test sample. The algorithms were applied to all consultation notes, operative notes, pathology reports, and microbiology reports to predict the correct status of PJI based on MSIS criteria.ResultsThe algorithm, which identified patients with PJI based on MSIS criteria, achieved an f1-score (harmonic mean of precision and recall) of 0.911. Algorithm performance in extracting the presence of sinus tract, purulence, pathologic documentation of inflammation, and growth of cultured organisms from the involved TJA achieved f1-scores that ranged from 0.771 to 0.982, sensitivity that ranged from 0.730 to 1.000, and specificity that ranged from 0.947 to 1.000.ConclusionNLP-enabled algorithms have the potential to automate data collection for PJI diagnostic elements, which could directly improve patient care and augment cohort surveillance and research efforts. Further validation is needed in other hospital settings.Level of EvidenceLevel III, Diagnostic.     

Periprosthetic Joint Infection Prediction via Machine Learning: Comprehensible Personalized Decision Support for Diagnosis

BackgroundThe criteria outlined in the International Consensus Meeting (ICM) in 2018, which were prespecified and fixed, have been commonly practiced by clinicians to diagnose periprosthetic joint infection (PJI). We developed a machine learning (ML) system for PJI diagnosis and compared it with the ICM scoring system to verify the feasibility of ML.MethodsWe designed an ensemble meta-learner, which combined 5 learning algorithms to achieve superior performance by optimizing their synergy. To increase the comprehensibility of ML, we developed an explanation generator that produces understandable explanations of individual predictions. We performed stratified 5-fold cross-validation on a cohort of 323 patients to compare the ML meta-learner with the ICM scoring system.ResultsCross-validation demonstrated ML’s superior predictive performance to that of the ICM scoring system for various metrics, including accuracy, precision, recall, F1 score, Matthews correlation coefficient, and area under receiver operating characteristic curve. Moreover, the case study showed that ML was capable of identifying personalized important features missing from ICM and providing interpretable decision support for individual diagnosis.ConclusionUnlike ICM, ML could construct adaptive diagnostic models from the available patient data instead of making diagnoses based on prespecified criteria. The experimental results suggest that ML is feasible and competitive for PJI diagnosis compared with the current widely used ICM scoring criteria. The adaptive ML models can serve as an auxiliary system to ICM for diagnosing PJI.     

Trends of Prosthetic Joint Infection Organisms and Recurrence for a Single High-Volume Arthroplasty Surgeon Over 20 Years

BackgroundProsthetic joint infection (PJI) is a morbid complication following total joint arthroplasty (TJA). PJI diagnosis and treatment has changed over time, and patient co-management with a high-volume musculoskeletal infectious disease (MSK ID) specialist has been implemented at our institution in the last decade.MethodsWe retrospectively evaluated all consecutive TJA patients treated for PJI between 1995 and 2018 by a single high-volume revision TJA surgeon. Microbial identities, antibiotic resistance, prior PJI, and MSK ID consultation were investigated.ResultsIn total, 261 PJI patients (median age 66 years, interquartile range 57-75) were treated. One-year and 5-year reinfection rates were 15.8% (95% confidence interval [CI] 11.6-20.7) and 22.1% (95% CI 17.0-27.7), respectively. Microbial identities and antibiotic resistances did not change significantly over time. Despite seeing more prior PJI patients (53.3% vs 37.6%, P = .012), MSK ID-managed patients had similar infection rates as non-MSK ID-managed patients (hazard ratio [HR] 1.02, 95% CI 0.6-1.75, P = .93). Prior PJI was associated with higher reinfection risk (HR 2.39, 95% CI 1.39-4.12, P = .002) overall and in patients without MSK ID consultation, specifically (HR 2.78, 95% CI 1.37-5.65, P = .005). This risk was somewhat lower and did not reach significance in prior PJI patients with MSK ID consultation (HR 1.97, 95% CI 0.87-4.48, P = .106).ConclusionWe noted minimal differences in microbial/antibiotic resistances for PJI over 20 years in a single institution, suggesting current standards of PJI treatment remain encouragingly valid in most cases. MSK ID involvement was not associated with lower reinfection risk overall; however, in patients with prior PJI, the risk of reinfection appeared to be somewhat lower with MSK ID involvement.Level of EvidenceLevel IV–Case Series.     

Alpha-Defensin Offers Limited Utility in Work-Up Prior to Reimplantation in Chronic Periprosthetic Joint Infection in Total Joint Arthroplasty Patients

BackgroundAlpha-defensin (AD) is a synovial biomarker included in the 2018 consensus criteria for diagnosing periprosthetic joint infection (PJI). Its value in assessing eradication of infection prior to second stage reimplantation is unclear. The purpose of this study was to evaluate the impact of AD on eligibility for reimplantation following resection for chronic PJI.MethodsThis study included patients who previously underwent resection arthroplasty for PJI. Synovial fluid aspirated from 87 patients was retrospectively reviewed. All patients completed a 6-week course of intravenous antibiotics and an appropriate drug holiday. Synovial white blood cell count, percentage neutrophils, and culture from the AD immunoassay laboratory were reviewed with serum erythrocyte sedimentation rate and C-reactive protein values from our institution. A modified version of the 2018 consensus criteria was used, including white blood cell count, percentage neutrophils, erythrocyte sedimentation rate, and C-reactive protein. AD was then added to determine if it changed diagnosis or clinical management.ResultsFour patients were categorized as “infected” (score >6), none exhibited a positive AD or positive culture. Sixty eight patients were diagnosed as “possibly infected” (score 2 to 5), none had a positive AD, and one had a positive culture (Cutibacterium acnes). AD did not change the diagnosis from “possibly infected” to “infected” in any case or alter treatment plans. Fifteen patients had a score of <2 (not infected) and none had a positive AD.ConclusionThe routine use of AD in the work-up prior to a second-stage arthroplasty procedure for PJI may not be warranted.     

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

BackgroundPeriprosthetic joint infection (PJI) after total hip arthroplasty (THA) is challenging to diagnose. We aimed to evaluate the impact of dry taps requiring saline lavage during preoperative intra-articular hip aspiration on the accuracy of diagnosing PJI before revision surgery.MethodsA retrospective review was conducted for THA patients with suspected PJI who received an image-guided hip aspiration from May 2016 to February 2020. Musculoskeletal Infection Society (MSIS) diagnostic criteria for PJI were compared between patients who had dry tap (DT) vs successful tap (ST). Sensitivity and specificity of synovial markers were compared between the DT and ST groups. Concordance between preoperative and intraoperative cultures was determined for the 2 groups.ResultsIn total, 335 THA patients met inclusion criteria. A greater proportion of patients in the ST group met MSIS criteria preoperatively (30.2% vs 8.3%, P < .001). Patients in the ST group had higher rates of revision for PJI (28.4% vs 17.5%, P = .026) and for any indication (48.4% vs 36.7%, P = .039). MSIS synovial white blood cell count thresholds were more sensitive in the ST group (90.0% vs 66.7%). There was no difference in culture concordance (67.9% vs 65.9%, P = .709), though the DT group had a higher rate of negative preoperative cultures followed by positive intraoperative cultures (85.7% vs 41.1%, P = .047).ConclusionOur results indicate that approximately one third of patients have dry hip aspiration, and in these patients cultures are less predictive of intraoperative findings. This suggests that surgeons considering potential PJI after THA should apply extra scrutiny when interpreting negative results in patients who require saline lavage for hip joint aspiration.