What is the Clinical Utility of Synovial Alpha Defensin Testing of Antibiotic Spacers Before Reimplantation?

BackgroundThe purpose of this study was to evaluate the diagnostic performance of standalone alpha defensin (AD) testing of antibiotic spacers during two stage exchange and to determine if the addition of AD testing to other commonly used laboratory tests improves the ability to detect persistent infection in an antibiotic spacer.MethodsCases of two-stage exchange for periprosthetic joint infection from 2016 to 2019 at a single institution were retrospectively reviewed. Cases were classified as persistently infected or not infected in accordance with 2014 and 2018 Musculoskeletal Infection Society criteria to determine if AD provided any clinical utility beyond the other commonly used tests that make up both criteria. Delphi Consensus criteria at 1 year were used as the gold standard for determining recurrent periprosthetic joint infection.ResultsFifty-two spacers (25 hips and 27 knees) in 51 patients were included for analysis. Five spacers were persistently infected based on Musculoskeletal Infection Society criteria. One spacer underwent reresection and the remaining 4 underwent reimplantation with no subsequent infectious complications. All 48 patients who were categorized as not infected underwent reimplantation; at 1 year postoperatively, 7 (13%) had failed due to infection. Three spacers (6%) had a positive AD test. Two spacers with positive AD tests underwent reimplantation, neither had failed at 1 year postoperatively. Sensitivity of standalone AD testing was 0%, and specificity was 96%.ConclusionStandalone AD testing for the purpose of predicting repeat infection after two-stage exchange arthroplasty exhibits sensitivity of 0% and low predictive value. Addition of synovial AD testing did not increase the diagnostic performance of commonly used synovial and serologic markers of infection.Level of EvidenceIV—retrospective cohort study.     

Diagnostic Accuracy of the Alpha-Defensin Test for Periprosthetic Joint Infection in Patients With Inflammatory Diseases

BackgroundThe alpha-defensin test has been reported to have high accuracy to diagnose periprosthetic joint infection (PJI). There are remaining concerns about the utility of the test in patients with inflammatory diseases. The purpose of this study is to determine sensitivity and specificity of laboratory-based alpha-defensin in diagnosing PJI in patients with systemic inflammatory disease in revision total hip/knee arthroplasty.MethodsA retrospective review was conducted of 1374 cases who underwent revision total hip/knee arthroplasty at a single healthcare system from 2014 to 2017. Cases with inflammatory diseases who received a 1-stage revision arthroplasty, the first stage of 2-stage revision arthroplasty, or irrigation and debridement with available preoperative alpha-defensin results were included. Patients who received a second-stage procedure, spacer exchange, who had insufficient Musculoskeletal Infection Society criteria, or with early postoperative PJI were excluded from this study. Cases were classified as infected or not according to Musculoskeletal Infection Society criteria. A total of 41 cases met the inclusion criteria. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of alpha-defensin to diagnose PJI were calculated.ResultsThe alpha-defensin test demonstrated a sensitivity of 93%, a specificity of 100%, a positive predictive value of 100%, a negative predictive value of 96%, and an accuracy of 97% for diagnosing PJI. There was 1 patient with polymyositis who had a false-negative result.ConclusionAlpha-defensin had high accuracy for diagnosing PJI even in inflammatory diseases. The alpha-defensin test provides useful information with high accuracy in diagnosing PJI in patients with inflammatory diseases.     

Time to Reimplantation: Waiting Longer Confers No Added Benefit

Background

While the preferred surgical treatment for chronic periprosthetic joint infection (PJI) in North America is a 2-stage exchange arthroplasty, the optimal time between first-stage and reimplantation surgery remains unknown. This study was conceived to examine the association between time to reimplantation and treatment failure.

Synovial-Based Tests Outperform Serum Markers to Rule Out Infection in Total Knee Arthroplasty and Total Hip Arthroplasty: A Systematic Review and Meta-Analysis

BackgroundTotal knee arthroplasty (TKA) provides successful results in most patients. Periprosthetic joint infection (PJI) accounts for up to 25% of failed TKAs needing revision. In clinical practice, consensus in diagnostic strategy for excluding or diagnosing PJI is still lacking. In this systematic review and meta-analysis, we aim to provide a simplified data-driven diagnostic strategy for aseptic knee and hip revision surgeons to rule out PJI in the outpatient clinic phase.MethodsA literature search in EMBASE, MEDLINE, PubMed, and Cochrane was conducted. Studies involving the diagnosis of PJI in patients with failed TKAs and total hip arthroplasties needing revision were identified. Only studies using the Musculoskeletal Infection Society criteria were included. Quality was assessed using MINORS criteria. Meta-analysis was performed for each diagnostic test identified in the included studies. Pooled estimates of diagnostic accuracy measures were calculated using a bivariate model and plotted in summary receiver–operator characteristic curves. Positive and negative predictive values were calculated in a hypothetical sample of patients with a given disease prevalence.ResultsTwenty-four studies met the inclusion criteria, describing a total of 2974 patients. Quality scores ranged from 13 to 19. Meta-analysis could be performed on 7 unique diagnostic tests. Highest pooled sensitivity and specificity were demonstrated for α-defensin with values of 86% and 96.6%, respectively. α-defensin and white blood cell count in synovial fluid demonstrate highest negative predictive value values.ConclusionsWe recommend, in a clinical setting with low–intermediate prevalence of PJI, performing arthrocentesis and joint fluid analysis using α-defensin and/or white blood cell count before revision TKA and revision total hip arthroplasty surgery to rule out PJI.     

Do Positive Cultures at Second Stage Re-Implantation Increase the Risk for Reinfection in Two-Stage Exchange for Periprosthetic Joint Infection?

BackgroundIntraoperative cultures are important in the diagnosis and targeted treatment of periprosthetic joint infection (PJI). Positive cultures at reimplantation during a two-stage exchange are discussed as a risk factor for reinfection. The aim of this study is the investigation of the incidence and risk factors for positive cultures during reimplantation.MethodsWe retrospectively identified 204 patients (111 knees, 93 hips) who were treated between 2012 and 2016 for PJI using a two-stage exchange protocol at a median follow-up of 42 months. PJI was diagnosed using the criteria of the musculoskeletal infection society (MSIS) of 2011. All cultural findings from first and second stage surgery were recorded. The primary endpoint was revision for infection. Risk factors for positive cultures and reinfection were analyzed.ResultsDuring reimplantation 25% (51/204) of patients had at least one positive culture, in 19.1% (39/204) only a single culture. Patients with culture-negative infections had a higher risk for positive cultures at reimplantation (HR 2.946 (95% CI 1.247-6.961), P = .014) and patients with infected total hip arthroplasty (THA) (HR 3.547 (95% CI 1.7-7.4), P = .001). Patients with positive cultures during reimplantation had a higher risk for reinfection (HR 2.27 (95% CI 1.181-4.363), P = .014) as well as patients with a single positive culture (HR 2.421 (95% CI 1.139-5.143), P = .021).ConclusionAs positive cultures are common and increase reinfection risk irrespective of their numbers, longer antibiotic therapy following reimplantation can be an option. Single positive cultures in reimplantation surgery should not be considered contamination.     

The 2018 New Definition of Periprosthetic Joint Infection is Valuable for Diagnosis of Persistent Infection at Reimplantation in Patients without Synovial Fluid

BackgroundDiagnosis of persistent infection at reimplantation of 2-stage exchange revision is a challenging problem. The aim of our study is to evaluate the performance of the 2018 new definition and Musculoskeletal Infection Society (MSIS) criteria in determining the persistent infection at reimplantation in patients without synovial fluid.MethodsWe retrospectively reviewed 150 patients who underwent 2-stage exchange revision from 2014 to 2018. Two models were used to define persistent infection—model 1: identical major criteria of the MSIS criteria and new definition and model 2: identical major criteria of 2 criteria and/or subsequent infection after reimplantation. The predictive accuracy of the new definition and MSIS criteria was compared by using receiver operating characteristic curves.ResultsThe receiver operating characteristic curves showed that the new definition had good performance in determining the persistent infection, with the area under the curve (AUC) of 0.871 in model 1 and 0.835 in model 2. The optimal threshold for aggregate scores in new definition was 4. The MSIS criteria had limited diagnostic value in both model 1 (AUC = 0.708) and model 2 (AUC = 0.664). In model 1, the sensitivity and specificity were 86.96% and 84.25% in new definition, and 47.83% and 93.70% in MSIS criteria in patients without synovial fluid. In model 2, the sensitivity and specificity were 78.57% and 85.25% in new definition, and 39.29% and 93.44% in MSIS criteria.ConclusionThe 2018 new definition of PJI is valuable in the diagnosis of persistent infection, which can improve diagnostic accuracy compared with the MSIS criteria in patients without synovial fluid.     

Plasma D-dimer Does Not Anticipate the Fate of Reimplantation in Two-stage Exchange Arthroplasty for Periprosthetic Joint Infection: A Preliminary Investigation

BackgroundInflammatory markers such as the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels have always been a part of the diagnostic criteria for periprosthetic joint infection (PJI), but they perform poorly anticipating the outcome of reimplantation. D-dimer has been reported in a small series as a potential marker to measure infection control after single-stage revisions to treat PJI. Nonetheless, its use to confirm infection control and decide the proper timing of reimplantation remains uncertain.Questions/purposes(1) What is the best diagnostic threshold and accuracy values for plasma D-dimer levels compared with other inflammatory markers (ESR and CRP) or what varying combinations of these tests are associated with persistent infection after reimplantation? (2) Do D-dimer values above this threshold, ESR, CRP, and varying test combinations at the time of reimplantation indicate an increased risk of subsequent persistent infection after reimplantation?MethodsWe retrospectively studied the electronic medical records of all 53 patients who had two-stage revisions for PJI and who underwent plasma D-dimer testing before reimplantation at one of two academic institutions from November 22, 2017 to December 5, 2020. During that period, all patients undergoing two-stage revisions also had a D-dimer test drawn. The minimum follow-up duration was 1 year. We are reporting at this early interval (rather than the more typical 2-year time point) because of the poorer-than-expected performance of this diagnostic test. Of these 53 patients, 17% (9) were lost to follow-up before 1 year and could not be analyzed; the remaining 44 patients (17 hips and 27 knees) were studied here. The mean follow-up was 503 ± 135 days. Absence or persistence of infection after reimplantation were defined according to the Delphi criteria. The conditions included in these criteria were: (1) control of infection, as characterized by a healed wound without fistula, drainage, or pain; (2) no subsequent surgical intervention owing to infection after reimplantation; and (3) no occurrence of PJI-related mortality. The absence of any of the aforementioned conditions until the final follow-up examination was deemed a persistent infection after reimplantation. Baseline patient characteristics were not different between patients with persistent infection (n = 10) and those with absence of it after reimplantation (n = 34) as per the Delphi criteria. Baseline patient characteristics evaluated were age, gender, self-reported race (white/Black/other) or ethnicity (nonHispanic/Hispanic), BMI, American Society of Anesthesiologists (ASA) status, smoking status(smoker/nonsmoker), and joint type (hip/knee). The optimal D-dimer threshold to differentiate between persistence of infection or not after reimplantation was calculated using the Youden index. A receiver operating characteristic curve analysis was performed to test the accuracy of D-dimer, ESR, CRP, and their combinations to establish associations, if any, with persistent infection after reimplantation. A Kaplan-Meier survival analysis (free of infection after reimplantation) with a log-rank test was performed to investigate if D-dimer, ESR, and CRP were associated with absence of infection after reimplantation. Survival or being free of infection after reimplantation was determined as per Delphi criteria. Alpha was set at p < 0.05.ResultsIn the receiver operating characteristic curve analysis, with an area under the curve of 0.62, D-dimer showed low accuracy and did not anticipate persistent infection after reimplantation. The optimal D-dimer threshold differentiating between persistence of infection or not after reimplantation was 3070 ng/mL. When using this threshold, D-dimer demonstrated a sensitivity of 90% (95% CI 55.5% to 99.7%) and negative predictive value of 94% (95% CI 70.7% to 99.1%), but low specificity (47% [95% CI 29.8% to 64.9%]) and positive predictive value (33% [95% CI 25.5% to 42.2%]). Although D-dimer showed the highest sensitivity, the combination of D-dimer with ESR and CRP showed the highest specificity (91% [95% CI 75.6% to 98%]) defining the persistence of infection after reimplantation. Based on plasma D-dimer levels, with the numbers available, there was no difference in survival free from infection after reimplantation (Kaplan-Meier survivorship free from infection at minimum 1 year in patients with D-dimer below 3070 ng/mL versus survivorship free from infection with D-dimer above 3070 ng/mL: 749 days [95% CI 665 to 833 days] versus 615 days [95% CI 471 to 759 days]; p = 0.052). Likewise, there were no associations between high ESR and CRP levels and persistent infection after reimplantation, but the number of events was very small, and insufficient power is a concern with this analysis.ConclusionIn this preliminary series, with the numbers available, D-dimer alone had poor accuracy and was not associated with survival free from infection after reimplantation in patients who underwent two-stage exchange arthroplasty. D-dimer alone might be used to establish that PJI is unlikely, and the combination of D-dimer, ESR, and CRP should be considered to confirm PJI diagnosis in the setting of reimplantation.Level of Evidence Level IV, diagnostic study.     

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.     

Patients With Failed Prior Two-Stage Exchange Have Poor Outcomes After Further Surgical Intervention

Background

Failure of 2-stage exchange arthroplasty for the management of periprosthetic joint infection (PJI) poses a major clinical challenge. There is a paucity of information regarding the outcomes of further surgical intervention in these patients. Thus, we aim to report the clinical outcomes of subsequent surgery for a failed prior 2-stage exchange arthroplasty.

Can the Leukocyte Esterase Strip Test Predict Persistence of Periprosthetic Joint Infection at Second-Stage Reimplantation?

BackgroundWe evaluated the reliability of intraoperative assessment of leukocyte esterase (LE) in synovial fluid samples from patients undergoing reimplantation following implant removal and spacer insertion for periprosthetic joint infection (PJI). Our hypothesis was that a positive intraoperative LE test would be a better predictor of persistent infection than either serum C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) or the combination of serum CRP and ESR.MethodsThe records of 76 patients who received a 2-stage exchange for PJI were retrospectively reviewed. Synovial fluid was collected for LE measurement during surgery before arthrotomy in 79 procedures. Receiver operating characteristic curves were generated. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and area under the curve (AUC) of LE, CRP, ESR, and CRP + ESR were calculated.ResultsSensitivity, specificity, positive predictive value, and negative predictive value of the LE assay were 82%, 99%, 90%, and 97%, respectively. Receiver operating characteristic analysis revealed an LE threshold of 1.5 between the first (negative) and the second (positive) level of the ordinal variable, so that a grade starting from 1+ was accurate for a diagnosis of persistent infection (AUC 0.9044). The best thresholds for the CRP and the ESR assay were 8.25 mg/L (82% sensitivity, 84% specificity, AUC 0.8416) and 45 mm/h (55% sensitivity, 87% specificity, AUC 0.7493), respectively.ConclusionThe LE strip test proved a reliable tool to diagnose persistence of infection and outperformed the serum CRP and ESR assays. The strip test provides a valuable intraoperative diagnostic during second-stage revision for PJI.     

Unexpected Positive Intraoperative Cultures in Aseptic Revision Arthroplasty

Unexpected positive intraoperative cultures (UPIC) in presumed aseptic revision arthroplasty can be difficult to interpret. The purpose of this retrospective study was to compare the incidence of subsequent periprosthetic joint infection (PJI) in patients who received antibiotic therapy according to an institutional protocol with those who did not and whether they meet Musculoskeletal Infection Society (MSIS) criteria for PJI. In patients who were treated with antibiotic according to institutional criteria, the incidence of PJI after revision was higher in those who did not meet MSIS criteria (22%) than in those that met MSIS criteria (14%; P > 0.71). UPIC in aseptic revision arthroplasty are not uncommon. PJI cannot be excluded in patients that do not meet MSIS definition.     

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.     

Increased Postoperative Glucose Variability Is Associated With Adverse Outcome Following Two-Stage Exchange Arthroplasty for Periprosthetic Joint Infection

BackgroundGlucose variability in the postoperative period has been associated with increased rates of periprosthetic joint infection (PJI) following primary arthroplasty. It is unknown how postoperative glucose control affects outcome of surgical treatment of PJI patients. We hypothesized that postoperative glucose variability adversely affects the outcome of 2-stage exchange arthroplasty.MethodsWe retrospectively reviewed records of 665 patients with PJI of the knee and hip who underwent 2-stage exchange arthroplasty from 2000 to 2017. Of them, 341 PJIs with a minimum follow-up of 1 year, and either a minimum of 2 glucose values per day or greater than 3 overall during the reimplantation were included. Glucose variability was assessed by calculating the coefficient of variation. Adverse outcomes included treatment failure according to the Delphi consensuses criteria, reinfection, reoperation, and mortality. A subgroup analysis was performed based on patients with or without diabetes.ResultsGlucose variability following reimplantation was associated with higher treatment failure, reinfection, and reoperation. Adjusted analysis indicated that for every standard deviation (15%) increase in the coefficient of variation, the risks of treatment failure, reinfection, and reoperation increased by 27%, 31%, and 26%. Although stratifying patients with (n = 81) or without diabetes (n = 260), these associations remained robust in nondiabetic patients, but not in diabetic patients.ConclusionHigher glucose variability is associated with increased risks of treatment failure, reinfection, and reoperation after 2-stage exchange arthroplasty in PJI patients. Compared to diabetic patients, nondiabetic patients have a higher association between glucose variability and poor outcomes. Reducing adverse outcomes may be achieved with close monitoring and strict postoperative glucose control.     

1.5-Stage Exchange Arthroplasty for Total Knee Arthroplasty Periprosthetic Joint Infections

BackgroundPeriprosthetic joint infection (PJI) in total knee arthroplasty (TKA) is a challenging problem. The purpose of this study was to outline a novel technique to treat TKA PJI. We define 1.5-stage exchange arthroplasty as placing an articulating spacer with the intent to last for a prolonged time.MethodsA retrospective review was performed from 2007 to 2019 to evaluate patients treated with 1.5-stage exchange arthroplasty for TKA PJI. Inclusion criteria included: articulating knee spacer(s) remaining in situ for 12 months and the patient deferring a second-stage reimplantation because the patient had acceptable function with the spacer (28 knees) or not being a surgical candidate (three knees). Thirty-one knees were included with a mean age of 63 years, mean BMI 34.4 kg/m², 12 were female, with a mean clinical follow-up of 2.7 years. Cobalt-chrome femoral and polyethylene tibial components were used. We evaluated progression to second-stage reimplantation, reinfection, and radiographic outcomes.ResultsAt a mean follow-up of 2.7 years, 25 initial spacers were in situ (81%). Five knees retained their spacer(s) for some time (mean 1.5 years) and then underwent a second-stage reimplantation; one of the five had progressive radiolucent lines but no evidence of component migration. Three knees (10%) had PJI reoccurrence. Four had progressive radiolucent lines, but there was no evidence of component migration in any knees.Conclusions1.5-stage exchange arthroplasty may be a reasonable method to treat TKA PJI. At a mean follow-up of 2.7 years, there was an acceptable rate of infection recurrence and implant durability.     

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     

Do Culture Negative Periprosthetic Joint Infections Remain Culture Negative?

BackgroundDiagnosis and treatment of culture negative total knee arthroplasty (TKA) periprosthetic joint infection (PJI) is challenging. There is debate over whether culture negative PJI confers increased risk of failure and which organisms are responsible. It is also unclear as to what factors predict conversion from culture negative to culture positivity. To address these issues, we performed an observational study to detect factors associated with transition from culture negative to culture positive TKA PJI in those patients that failed irrigation and debridement (I&D), determine the incidence of this transition, and identify those organisms that were associated with treatment failure.MethodsA multicenter observational cohort study was performed on patients with TKA PJI as defined by Musculoskeletal Infection Society criteria without cultured organisms and treated with I&D. Primary outcome was failure defined as any subsequent surgical procedure. Secondary outcome included cultured organism within 2 years of initial I&D.ResultsTwo hundred sixteen TKA I&D procedures were performed for PJI, and 36 met inclusion criteria. The observed treatment failure rate for culture negative PJI treated with I&D was 41.67%. Of those culture negative I&Ds that failed, 53.33% became culture positive after failure. Of those that converted to culture positive, 62.5% were Staphylococcus species. The odds ratio associated with becoming culture positive following culture negative treatment failure in the setting of antibiotic administration prior to the initial I&D procedure was 0.69 (95% confidence interval 0.14-3.47, P = .65).ConclusionMany cases of culture negative TKA PJI treated with I&D eventually fail and become culture positive. Staphylococci are common organisms identified after culture negative PJI.     

Total Femur Antibiotic Spacers: Effective Salvage for Complex Periprosthetic Joint Infections

BackgroundA simultaneous periprosthetic joint infection (PJI) of an ipsilateral hip and knee arthroplasty is a challenging complication of lower extremity reconstructive surgery. We evaluated the use of total femur antibiotic-impregnated polymethylmethacrylate (PMMA) bone cement spacers in the staged treatment of such limb-threatening PJIs.MethodsThirteen patients were treated with a total femur antibiotic spacer. The mean age at the time of spacer placement was 65 years. Nine patients had polymicrobial PJIs. All spacers incorporated vancomycin (3.0 g/40 g PMMA) and gentamicin (3.6 g/40 g PMMA), while 8 also included amphotericin (150 mg/40 g PMMA). Eleven spacers were biarticular. Twelve spacers were implanted through one longitudinal incision, while 8 of 12 reimplantations occurred through 2 smaller, separate hip and knee incisions. Mean follow-up after reimplantation was 3 years.ResultsTwelve (92%) patients underwent reimplantation of a total femur prosthesis at a mean of 26 weeks. One patient died of medical complications 41 days after spacer placement. At latest follow-up, 3 patients had experienced PJI recurrence managed with irrigation and debridement. One required acetabular component revision for instability. All 12 reimplanted patients retained the total femur prosthesis with no amputations. Eleven (91%) were ambulatory, and 7 (58%) remained on suppressive antibiotics.ConclusionTotal femur antibiotic spacers are a viable, but technically demanding, limb-salvage option for complex PJIs involving the ipsilateral hip and knee. In the largest series to date, there were no amputations and 75% of reimplanted patients remained infection-free. Radical debridement, antimicrobial diversity, prolonged spacer retention, and limiting recurrent soft tissue violation are potential tenets of success.Level of EvidenceIV.     

Leukocyte Esterase Strip Test Can Predict Subsequent Failure Following Reimplantation in Patients With Periprosthetic Joint Infection

Background

Leukocyte esterase (LE) strip test is an accurate marker for diagnosing periprosthetic joint infection (PJI). This study aims to determine if LE is a good predictor of persistent infection and/or subsequent failure in patients undergoing reimplantation.

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.