Value of preoperative investigations in diagnosing prosthetic joint infection: retrospective cohort study and literature review

Imaging in osteoarticular infection in adults

BACKGROUND

Osteoarticular infections are uncommon and required a multimodal approach for diagnosis. Imaging forms an important component of this multimodal approach.

OBJECTIVES

In this narrative review, we describe the different imaging modalities, features of osteoarticular infections present on these imaging approaches and recommendations for which imaging modality should be considered in different types of osteoarticular infections.

SOURCES

This narrative review was based on literature review from PubMed and was limited to bacterial infections in adult patients.

CONTENT

Imaging modalities include modalities that provide information on the anatomy or radionuclide imaging that provides information about the metabolic activity of the area of interest. Anatomical imaging includes plain radiographs (X-ray), computed tomography, and magnetic resonance imaging. Radionuclide approaches include three-phase bone scintigraphy, gallium scans, white blood cell scintigraphy, and 18F-fluorodeoxy-glucose positron emission tomography. The optimal radiological modality for diagnosis is influenced by multiple factors, including infection location, presence of metalware, timing of infection from any preceding surgery or fracture, antibiotic use, and patient comorbidities. Local availability of scanning modality, tracer supply, technical expertise, and patient access also influences choice.

IMPLICATIONS

A collaborative approach with imaging, pathology and clinical input in a multidisciplinary setting is paramount for the diagnosis of osteoarticular infections. Increasing research and improvements in technology will further improve the utility and accuracy of imaging approaches for imaging in osteoarticular infections.

Injectable systems of chitosan in situ forming composite gel incorporating linezolid-loaded biodegradable nanoparticles for long-term treatment of bone infections

The objective of the current study was to create an efficient, minimally invasive combined system comprising in situ forming hydrogel loaded with both spray-dried polymeric nanoparticles encapsulating linezolid and nanohydroxyapatite for local injection to bones or their close vicinity. The developed system was designed for a dual function namely releasing the drug in a sustained manner for long-term treatment of bone infections and supporting bone proliferation and new tissues generation. To achieve these objectives, two release sustainment systems for linezolid were optimized namely a composite in situ forming chitosan hydrogel and spray-dried PLGA/PLA solid nanoparticles. The composite, in situ forming hydrogel of chitosan was prepared using two different gelling agents namely glycerophosphate (GP) and sodium bicarbonate (NaHCO3) at 3 different concentrations each. The spray-dried linezolid-loaded PLGA/PLA nanoparticles were developed using a water-soluble carrier (PVP K30) and a lipid soluble one (cetyl alcohol) along with 3 types of DL-lactide and/or DL-lactide-co-glycolide copolymer using nano-spray-drying technique. Finally, the optimized spray-dried linezolid nanoparticles were incorporated into the optimized composite hydrogel containing nanohydroxy apatite (nHA). The combined hydrogel/nanoparticle systems displayed reasonable injectability with excellent gelation time at 37 °C. The optimum formulae sustained the release of linezolid for 7-10 days, which reveals its ability to reduce the frequency of injection during the course of treatment of bones infections and increase the patients' compliance. They succeeded to alleviate the bone infections and the associated clinical, biochemical, radiological, and histopathological changes within 2-4 weeks of injection. As to the state of art in this study and to the best of our knowledge, no such complete and systematic study on this type of combined in situ forming hydrogel loaded with spray-dried nanoparticles of linezolid is available yet in literatures.

Can C-Reactive Protein-Lymphocyte Ratio Be Used as a Screening Tool to Confirm the Diagnosis of Periprosthetic Joint Infection?

Background

This study aimed to investigate whether periprosthetic joint infection (PJI) can be predicted by the C-reactive protein-to-lymphocyte ratio (CLR), whether this ratio increases the accuracy of PJI diagnosis, and whether it is more sensitive than other blood values and ratios.

Methods

The patients were divided into two groups: the septic revision (SR) group and the aseptic revision (AR) group. In cases of septic revision, the diagnosis of PJI was made based on the criteria proposed by the European Bone and Joint Infection Society (EBJIS). The groups were compared in terms of age, sex, body mass index, comorbidity, and preoperative laboratory results. The sensitivity, specificity, and diagnostic performance of the values and ratios were analyzed and compared.

Results

The receiver operating characteristic (ROC) analysis for the CLR gave a diagnostic value of 15.52, which provided a sensitivity of 91.1% and a specificity of 64.2% for PJI. The CLR gave lower specificity and higher sensitivity compared to the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) values. The ROC analysis showed that the CLR had a similar area under the curve (AUC) with the ESR and CRP (0.808). The CLR had a higher specificity than other ratios (platelet volume ratio, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and monocyte-to-lymphocyte ratio) and a higher value of the AUC. In the multivariate analysis, the CLR (hazard ratio, 1.088; 95% confidence interval, 1.063-1.113; p < 0.001) was found to be a significant risk factor. As CLR increased by one unit, the risk of PJI increased by 1.088 times, and it was statistically significant (p < 0.001).

Conclusions

The findings of this study suggest that CLR can serve as a valuable screening tool for diagnosing PJI. CLR demonstrated higher sensitivity in predicting PJI compared to ESR and CRP, and it exhibited greater specificity than other infection markers.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty: 2023 Update

Total knee arthroplasty is the most commonly performed joint replacement procedure in the United States. This manuscript will discuss the recommended imaging modalities for six clinical variants; 1. follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging, 2. Suspected infection after total knee arthroplasty. Additional imaging following radiographs, 3. Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs, 4. Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs, 5. Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs, and 6. Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy. Additional imaging following radiographs. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Low Risk of Acute Iatrogenic Periprosthetic Joint Infection After Prosthetic Joint Aspiration

BACKGROUND

Synovial fluid analysis is an essential tool in diagnosing periprosthetic joint infection (PJI) after total knee arthroplasty (TKA). However, concern exists that aspiration may introduce infection into a noninfected joint. Therefore, the purpose of this study was to evaluate the incidence of iatrogenic PJI following diagnostic knee aspiration done within 6 months of the primary TKA.

METHODS

Between 2017 and 2021, the senior surgeon performed over 4,000 primary TKAs and aspirated 155 knees in 137 patients for whom there was a suspicion for PJI within 6 months of their primary TKA. There were 22 knees diagnosed as infected from the initial aspiration and therefore were excluded from the study. The remaining 133 aspirates in 115 patients who were negative for infection were followed for 6 months for signs and symptoms of PJI to elucidate whether aspiration introduced infection into an initially noninfected joint.

RESULTS

There were 70 of 133 knees (52.6%) aspirated between 0 and 6 weeks after index TKA, 40 of 133 (30.1%) between 6 weeks and 3 months, and 23 of 133 (17.3%) between 3 and 6 months. At final follow-up, none of the 133 initially noninfected knees exhibited evidence of subsequent iatrogenic PJI or had subsequent surgery for infection.

CONCLUSION

While joint aspiration is a procedure with inherent risks, this study shows that the rate of iatrogenic PJI is extremely low (0%). Therefore, if infection is suspected, the surgeon should consider joint aspiration, even in the initial postoperative period, as the risk for introducing infection is far outweighed by the risk of missing an infection.

Complete blood platelet and lymphocyte ratios increase diagnostic accuracy of periprosthetic joint infection following total hip arthroplasty

INTRODUCTION

Systemically, changes in serum platelet to lymphocyte ratio (PLR), platelet count to mean platelet volume ratio (PVR), neutrophil to lymphocyte ratio (NLR) and monocyte to lymphocyte (MLR) represent primary responses to early inflammation and infection. This study aimed to determine whether PLR, PVR, NLR, and MLR can be useful in diagnosing periprosthetic joint infection (PJI) in total hip arthroplasty (THA) patients.

METHODS

A total of 464 patients that underwent revision THA with calculable PLR, PVR, NLR, and MLR in 2 groups was evaluated: 1) 191 patients with a pre-operative diagnosis of PJI, and 2) 273 matched patients treated for revision THA for aseptic complications.

RESULTS

The sensitivity and specificity of PLR combined with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), synovial white blood cell count (WBC) and synovial polymorphonuclear leukocytes (PMN) (97.9%; 98.5%) is significantly higher than only ESR combined with CRP, synovial WBC and synovial PMN (94.2%; 94.5%; p < 0.01). The sensitivity and specificity of PVR combined with ESR, CRP and synovial WBC, and synovial PMN (98.4%; 98.2%) is higher than only ESR combined with CRP, synovial WBC and synovial PMN (94.2%; 94.5%; p < 0.01).

CONCLUSION

The study results demonstrate that both PLR and PVR calculated from complete blood counts when combined with serum and synovial fluid markers have increased diagnostic sensitivity and specificity in diagnosing periprosthetic joint infection in THA patients.

LEVEL OF EVIDENCE

III, case-control retrospective analysis.

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.

Serum D-lactate, a novel serological biomarker, is promising for the diagnosis of periprosthetic joint infection

Background

Although many markers are used for diagnosis of periprosthetic joint infection (PJI), serological screening and diagnosis for PJI are still challenging. We evaluated the performance of serum D-lactate and compared it with ESR, coagulation-related biomarkers and synovial D-lactate for the diagnosis of PJI.

Methods

Consecutive patients with preoperative blood and intraoperative joint aspiration of a prosthetic hip or knee joint before revision arthroplasty were prospectively included. The diagnosis of PJI was based on the criteria of the Musculoskeletal Infection Society, and the diagnostic values of markers were estimated based on receiver operating characteristic (ROC) curves by maximizing sensitivity and specificity using optimal cutoff values.

Results

Of 52 patients, 26 (50%) were diagnosed with PJI, and 26 (50%) were diagnosed with aseptic failure. ROC curves showed that serum D-lactate, fibrinogen (FIB) and ESR had equal areas under the curve (AUCs) of 0.80, followed by D-dimer and fibrin degradation product, which had AUCs of 0.67 and 0.69, respectively. Serum D-lactate had the highest sensitivity of 88.46% at the optimal threshold of 1.14 mmol/L, followed by FIB and ESR, with sensitivities of 80.77% and 73.08%, respectively, while there were no significant differences in specificity (73.08%, 73.08% and 76.92%, respectively).

Conclusion

Serum D-lactate showed similar performance to FIB and ESR for diagnosis of PJI. The advantages of serum D-lactate are pathogen-specific, highly sensitive, minimally invasive and rapidly available making serum D-lactate useful as a point-of-care screening test for PJI.

Preoperative Serum C-Reactive Protein/Albumin Ratio Is a Predictor of Complications After Single-stage Revision for the Treatment of Periprosthetic Joint Infection

BACKGROUND

The C-reactive protein/albumin ratio (CAR) is a marker of inflammation that has been associated with negative outcomes in the general surgery. This study investigates the potential association of preoperative CAR with postoperative complications and readmission rates in the treatment of patients with single-stage revision total joint arthroplasty for periprosthetic joint infection.

METHODS

A total of 213 consecutive patients who had undergone single-stage revision for total joint arthroplasty with the preoperative diagnosis of periprosthetic joint infection and preoperative C-reactive protein and albumin values were included. The area under receiver operating characteristic curves was calculated to evaluate the CAR as a predictive value for the complications.

RESULTS

Significant differences between the mean CAR were found for patients with 30- and 60-day readmissions and reinfection (P < 0.01). CAR combined with serum and synovial fluid markers demonstrated significantly higher sensitivities and specificities for the prediction of 30-day (total knee arthroplasty [TKA]: 94%; 95%; total hip arthroplasty [THA]: 91%; 96%) and 60-day readmissions (THA: 94%; 95%; TKA: 92%; 96%) and reinfections (TKA: 94%; 95%; THA: 87%; 96%), when compared with only serum and synovial fluid markers combined (83%; 84%; 85%; 87%; 85%; 88%; P <0.01).

DISCUSSION

High preoperative CAR, when combined with serum and synovial fluid markers, was associated with increased risk of reinfection and 30- and 60-day readmissions, suggesting that preoperative CAR is a clinically useful predictor for postoperative complications in patients with periprosthetic hip and knee joint infections.

Limited value of serum neutrophil-to-lymphocyte ratio in the diagnosis of chronic periprosthetic joint infection

Background

Diagnosing chronic periprosthetic joint infection (PJI) is challenging. No single biomarker can accurately recognize PJI preoperatively in a timely manner. Therefore, the aim of the present study was to investigate the usefulness of the serum neutrophil-to-lymphocyte ratio (NLR) in aiding the diagnosis of chronic PJI.

Materials and methods

We retrospectively evaluated the medical records of 158 patients who had undergone revision arthroplasty (104 with aseptic mechanic failure and 54 with chronic PJI) from July 2011 to July 2020. Univariate analysis followed by multivariate logistic regression was applied to compare NLR, C-reactive protein (CRP), and erythrocyte sedimentation ratio (ESR) between the two groups. The receiver operating characteristic (ROC) curve was used to assess the diagnostic performance of NLR alone and in combination with CRP and ESR.

Results

NLR, CRP, and ESR were significantly higher in patients with chronic PJI than in the aseptic revision group (p < 0.05). ROC curve analysis revealed that NLR had a sensitivity of 57.41% and a specificity of 77.88% with an optimal threshold of 2.56. The optimal threshold for CRP and ESR was 7.00 mg/L (sensitivity 62.50% and specificity 83.12%) and 43 mm/h (sensitivity 59.38% and specificity 80.52%), respectively. The combined diagnostic value of NLR with CRP and ESR was shown to have no additional diagnostic value in predicting chronic PJI.

Conclusion

Compared with traditional inflammatory biomarkers (ESR and CRP), the value of serum NLR alone or combined with CRP and ESR for diagnosing chronic PJI is limited.

Level of evidence

Level 3.

Non-vascular contributing factors of diabetic foot ulcer severity in national referral hospital of Indonesia

PURPOSE

Diabetic foot ulcer (DFU) is a common chronic complication of type 2 diabetes mellitus (T2DM) in Indonesia, with a prevalence of 7.3%. However, the characteristics of these patients remain unclear. We investigated the characteristics of patients with DFU without peripheral arterial disease (PAD) and analyzed non-vascular factors related to severity of DFU in a tertiary care national referral hospital in Indonesia.

METHODS

This was a cross-sectional study including 123 hemodynamically stable DFU patients without PAD recruited from Dr. Cipto Mangunkusumo National General Hospital, Jakarta, Indonesia from 2010-2015.

RESULTS

DFU patients were predominantly over 50 years old (75.6%) and diagnosed with T2DM for 5 years with poor glycemic control (82.7%) and peripheral neuropathy (91.3%). Most patients had anemia (86.7%), leukocytosis (84.6%), and were undernourished, as characterized by a low lipid profile (90.8%) and hypoalbuminemia (83.7%). Most had extensive size of ulcer at the initial visit, with a median size of 16.23 (2.92-60.16) cm2. Ulcers were mostly located of the forefoot (62.5%) and were caused by mechanical trauma (46.2%). Bivariate analysis revealed that significant factors for the development of DFU were related to DFU size, including duration of T2DM (p = 0.04), leukocyte levels (p =  < 0.01), and thrombocyte levels (p =  < 0.01). Multivariate analysis showed leucocyte (p = 0.03) and thrombocyte (p = 0.023) had significantly correlated with DFU severity.

CONCLUSION

Leucocyte and thrombocyte may be the greatest contributing non-vascular factors for severity of DFU in Indonesia.

Fluorescent-conjugated antibodies as rapid ex vivo markers for bacterial presence on orthopedic surgical explants and synovium: A pilot study

Surgical infection is one of the most pressing problems in the field of orthopedic surgery; however, current detection methods are plagued by high costs and long wait times. This study seeks to demonstrate the ability of a novel assay using fluorescently conjugated antibodies and confocal laser scanning microscopy (CLSM) to accurately detect bacterial presence on orthopedic surgical explants, tissue, and synovial fluid in 30 min. Explanted hardware, tissue, and synovial fluid samples suspected to be infected were collected from human subjects with institutional review board consent. Samples were prepared using a 30-min protocol, consisting of rinsing, nonspecific blocking and staining steps, and imaged using CLSM. Images were analyzed using ImageJ (National Institute of Health) to determine the percent area of Gram positive and Gram negative bacteria. Results of the assay were compared to the hospital's microbiological laboratory and Gram staining results. Ninety three samples were collected and tested using the 30-min testing protocol; 75 samples were synovial fluid and 18 were tissue and explants. Seventy four of 75 (98.6%) synovial fluid samples correlated with the hospital laboratory's microbiological findings. Of the 18 explant and tissue samples, our assay found bacterial presence in 14 of 18 samples, while the hospital microbiology laboratory found bacterial presence in 13 of 18 samples. This assay reliably stained and rapidly identified the presence of Gram negative and Gram positive bacteria on surgical explants, tissue and synovial fluid in 30 min. This methodology may serve as a point of service tool for the determination of bacterial presence during surgical procedures.

Development of systemic immune dysregulation in a rat trauma model of biomaterial-associated infection

Orthopedic biomaterial-associated infections remain a major clinical challenge, with Staphylococcus aureus being the most common pathogen. S. aureus biofilm formation enhances immune evasion and antibiotic resistance, resulting in a local, indolent infection that can persist long-term without symptoms before eventual hardware failure, bone non-union, or sepsis. Immune modulation is an emerging strategy to combat host immune evasion by S. aureus. However, most immune modulation strategies are focused on local immune responses at the site of infection, with little emphasis on understanding the infection-induced and orthopedic-related systemic immune responses of the host, and their role in local infection clearance and tissue regeneration. This study utilized a rat bone defect model to investigate how implant-associated infection affects the systemic immune response. Long-term systemic immune dysregulation was observed with a significant systemic decrease in T cells and a concomitant increase in immunosuppressive myeloid-derived suppressor cells (MDSCs) compared to non-infected controls. Further, the control group exhibited a regulated and coordinated systemic cytokine response, which was absent in the infection group. Multivariate analysis revealed high levels of MDSCs to be most correlated with the infection group, while high levels of T cells were most correlated with the control group. Locally, the infection group had attenuated macrophage infiltration and increased levels of MDSCs in the local soft tissue compared to non-infected controls. These data reveal the widespread impacts of an orthopedic infection on both the local and the systemic immune responses, uncovering promising targets for diagnostics and immunotherapies that could optimize treatment strategies and ultimately improve patient outcomes.

Hematologic Expression After Shoulder Surgery: Normalization Curve of Serum Inflammatory Markers

PURPOSE

To determine the normalization curves of the serologic markers including white blood cell (WBC) count, WBC differential for segmented neutrophil (WBC seg.), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) after elective shoulder surgery and to investigate the hematologic differences among different shoulder surgeries.

METHODS

Seventy-seven patients underwent arthroscopic rotator cuff repair (RCR, group A), 44 patients had open rotator cuff repair (group B), and 84 patients had shoulder arthroplasty (group C). Peak and normalization times of markers were determined at preoperatively, postoperative day (POD) 1 and 2 days, 1 and 2 weeks, 1, 2, 3, 6 months, and 1 year after surgery. The normal ranges of serologic markers were set to WBC 4000 to10,000/μL, WBC seg. 40% to 60%, ESR 0 to 20 mm/h, and CRP 0 to 0.8 mg/dL.

RESULTS

Groups reached peak mean WBC count and WBC seg. on POD 1; mean WBC count started decreasing on POD 2 but was within normal value afterwards. Mean WBC seg. decreased to normal value at 1 month postoperatively in group A and B and at 2 months postoperatively in group C. Mean ESR peaked at 2 weeks postoperatively and normalized after 1 month in groups A and B and 3 months in group C. Mean CRP levels peaked on POD 2 in all groups and normalized within 2 weeks postoperatively in groups A and B and 1 month postoperatively in Group C. Normalized values of WBC count, WBC seg., and ESR varied widely. In contrast, CRP showed a consistent undetectable median, upper and lower quartile values less than 0.5 after normalization. Mean serum ESR and CRP values at peak time were significantly greater in group C than in the other groups (P = .001).

CONCLUSIONS

The mean CRP levels were normalized at 2 weeks after rotator cuff repair and at 1 month after arthroplasties. Unlike the other serologic markers, CRP had consistent normalized values of median, upper and lower quartile afterwards. The peak levels of the inflammatory markers were greater and therefore normalized slower following more invasive surgery.

LEVEL OF EVIDENCE

Level III, case control study.

Serum globulin and albumin to globulin ratio as potential diagnostic biomarkers for periprosthetic joint infection: a retrospective review

Background

Periprosthetic joint infection (PJI) has been increasingly documented; however, its preoperative accurate diagnosis remains challenging. Furthermore, there is a dire need to identify appropriate and effective biomarkers. We aimed to evaluate the relationship between globulin, albumin to globulin (A/G) ratio, and development of PJI in patients undergoing revision total joint arthroplasty (TJA).

Methods

A retrospective study was conducted on patients who had undergone revision TJA between 2011 and 2018 (89 with aseptic mechanic failure and 38 with PJI). The serum proteins were explored using univariate analysis followed by multivariate logistic regression. The diagnostic performance of these proteins was assessed by the receiver operating characteristic (ROC) curve.

Results

Higher globulin levels (odds ratio [OR], 1.239; P < 0.001) and lower A/G ratio (OR, 0.007; P < 0.001) were strongly associated with the risk of PJI. ROC curve analysis demonstrated reasonable diagnostic performance for globulin (area under the curve [AUC], 0.77; sensitivity, 78.95%; and specificity, 69.66%) and A/G ratio (AUC, 0.779; sensitivity, 65.79%; and specificity, 78.65%).

Conclusions

Both globulin and A/G ratio were associated with PJI and may serve as potential adjuvant biomarkers in the diagnosis of PJI.

Risk Factors for Fungal Prosthetic Joint Infection

Background: Fungal prosthetic joint infections (PJIs) are rare and often associated with poor outcome; however, risk factors are not well described. Methods: This was a retrospective case control study among all patients with PJIs from 2006-2016 at two major academic centers. Each fungal PJI case was matched 1:1 with a bacterial PJI control by joint (hip, knee, shoulder) and year of diagnosis. We compared demographics, comorbidities, and clinical characteristics between cases and controls using chi square/Fisher's exact or Wilcoxon rank sum test. Independent risk factors were identified with multivariable logistic regression. Results: Forty-one fungal PJIs occurred over the study and 61% were due to Candida albicans. The hip was involved in 51.2% of cases, followed by the knee (46.3%). Compared to bacterial PJI, fungal PJI cases were more likely to have received antibiotics within the previous 3 months (70.7% vs 34%, P=.001), wound drainage lasting >5 days (48% vs 9%, P=.0002), had a lower median CRP (2.95 mg/dl vs 5.99, P=.013) and synovial fluid white blood cell count (13,953 cells/mm3 vs 33,198, P=.007), and a higher proportion of prior two-stage exchanges (82.9% vs 53.6%, P=.008). After controlling for center, prolonged wound drainage (OR, 7.3; 95% CI, 2.02-26.95) and recent antibiotics (OR, 3.4; 95% CI, 1.2-9.3) were significantly associated with fungal PJI. Conclusion: In our study, Candida albicans was the most common species in fungal PJIs and prolonged wound drainage and recent antibiotics were independent risk factors. These clinical characteristics may help providers anticipate fungal PJI and adjust management strategies.

Plasma Fibrin Degradation Product and D-Dimer Are of Limited Value for Diagnosing Periprosthetic Joint Infection

BACKGROUND

Although the Musculoskeletal Infection Society introduced the use of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) as inflammatory markers for diagnosing periprosthetic joint infection (PJI), no single blood marker reliably detects infection before revision arthroplasty. We therefore posed 2 questions: (1) Are fibrin degradation product (FDP) and D-dimer of value for diagnosing PJI before revision arthroplasty? (2) What are their sensitivity and specificity for that purpose?

METHODS

To answer these questions, we retrospectively enrolled 318 patients (129 with PJI [group A], 189 with aseptic mechanical failure [group B]) who underwent revision arthroplasty during 2013-2018. Receiver operating characteristic curves were used to determine maximum sensitivity and specificity of the 2 markers. Inflammatory and fibrinolytic markers were evaluated based on (1) the Tsukayama-type infection present and (2) the 3 most common PJI-related pathogens.

RESULTS

FDP and D-dimer levels were higher in group A than in group B: 4.97 ± 2.83 vs 4.14 ± 2.67 mg/L and 2.14 ± 2.01 vs 1.51 ± 1.37 mg/L fibrinogen equivalent units (FEU), respectively (both P < .05). Based on the Youden index, 2.95 mg/L and 1.02 mg/L FEU are the optimal FDP and D-dimer predictive cutoffs, respectively, for diagnosing PJI. Sensitivity and specificity, respectively, were 65.12% and 60.33% (FDP) and 68.29% and 50.70% (D-dimer). ESR, CRP, and interleukin-6 values were diagnostically superior to those of FDP and D-dimer.

CONCLUSION

The value of plasma FDP and D-dimer for diagnosing PJI is limited compared with traditional inflammatory markers (ESR, CRP, interleukin-6) before revision arthroplasty.

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.

Continuous Antibiotic Therapy Can Reduce Recurrence of Prosthetic Joint Infection in Patients Undergoing 2-Stage Exchange

BACKGROUND

Reimplantation microbiology and serum C-reactive protein have low diagnostic accuracy in predicting recurrence in patients with prosthetic joint infection (PJI) undergoing 2-stage exchange. We aimed at identifying factors relating to failure and comparing effect of continuous antibiotic therapy versus a holiday antibiotic period pre-reimplantation.

METHODS

This observational study included patients with PJI undergoing 2-stage exchange. Group A patients did not discontinue antibiotic treatment pre-reimplantation; in group B patients, antibiotic treatment was followed with 2 weeks of holiday antibiotic period pre-reimplantation. We defined cure as absence of recurrence for 96 weeks post-reimplantation. Statistical analyses were performed using Mann-Whitney U test, Fisher exact test, and multivariate analysis.

RESULTS

We evaluated 196 patients with PJI (median age, 66 years [interquartile range, 59-72], 91 [46%] males). Comorbidity was reported in 77 (39%), and microbiologic evidence was obtained in 164 (84%). Staphylococcus aureus was isolated in 63 of 164 (38%) patients; coagulase-negative staphylococci were isolated in 71 of 164 (43%). Favorable outcome was achieved for 169 (86%) patients (91% and 79% in groups A and B, respectively). No immunocompromise (odds ratio [OR], 2.73; 95% confidence interval [CI], 1.3-7.3; P = .04), a positive culture (OR, 3.96; 95% CI, 1.55-10.19; P = .02), and no antibiotic discontinuation (OR, 3.32; 95% CI, 1.3-8.44; P = .02) predicted favorable outcome using multivariate analysis.

CONCLUSION

Treatment with continuous antibiotic therapy ameliorated success rate, permitting a better outcome in immunocompromised and reducing the time to reimplantation. Continuous antibiotic therapy can be considered a valid option for the treatment of patients with PJI undergoing 2-stage exchange.

LEVEL OF EVIDENCE

Therapeutic level II.

Polymerase Chain Reaction Assay Using the Restriction Fragment Length Polymorphism Technique in the Detection of Prosthetic Joint Infections: A Multi-Centered Study

BACKGROUND

PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) techniques have been used for the diagnosis of bacteria in some infections. In this study, we aimed to evaluate the diagnostic accuracy of PCR for the diagnosis of prosthetic joint infections (PJI) and to identify isolated microorganisms, using the RFLP method.

METHODS

During January 2015 to January 2018, patients who were suspected of having PJI after arthroplasty surgery or were candidates for revision surgery due to loosening of implant entered the study. Patients who had 1 major criterion or 3 minor criteria for PJI based on the Philadelphia Consensus Criteria (PCC) on Periprosthetic Joint Infection were considered as cases of PJI. Both culture results and PCR findings, were cross compared with results of the PCC (as the gold standard criteria).

RESULTS

Overall, 76 samples were included in the study. Mean (standard deviation) age of patients was 66.72 ± 11.82 years. Overall, 57.9% of patients were females. Prevalence of PJI was 50% based on the PCC. Sensitivity, specificity, positive predictive value, negative predictive value, and general efficacy of PCR for detection of PJI was 97.4%, 100%, 100%, 97.4%, and 98.7%, respectively. Sensitivity, specificity, positive predictive value, negative predictive value, and general efficacy of culture was 31.6%, 100%, 65.7%, 100%, and 59.4%, respectively. We isolated a broad range of bacteria using PCR-RFLP including Gram-positive cocci such as Staphylococcus sp., Streptococcus sp., and Enterococcus sp., and Gram-negative bacilli such as Enterobacteriaceae sp., Pseudomonas sp. Citrobacter sp., as well as Chlamydophila pneumonia, Stenotrophomonas maltophilia, Brucella melitensis, non-gonococcal Neisseria, Kingella kingae, Bacteroides ovatus, and Proteus mirabilis from PJI patients.

CONCLUSION

Inhere, for the first time, we showed that PCR-RFLP is a powerful tool for identifying the type of bacteria involved in PJI, and can be used for follow-up of patients suspected of PJI and those with a history of antibiotic use. PCR-RFLP may be able to substantially decrease detection time of PJI among PCR-based methods, while allowing more accurate identification of the bacteria involved.

Consensus document for the diagnosis of prosthetic joint infections: a joint paper by the EANM, EBJIS, and ESR (with ESCMID endorsement)

Background

For the diagnosis of prosthetic joint infection, real evidence-based guidelines to aid clinicians in choosing the most accurate diagnostic strategy are lacking.

Aim and Methods

To address this need, we performed a multidisciplinary systematic review of relevant nuclear medicine, radiological, orthopaedic, infectious, and microbiological literature to define the diagnostic accuracy of each diagnostic technique and to address and provide evidence-based answers on uniform statements for each topic that was found to be important to develop a commonly agreed upon diagnostic flowchart.

Results and Conclusion

The approach used to prepare this set of multidisciplinary guidelines was to define statements of interest and follow the procedure indicated by the Oxford Centre for Evidence-based Medicine (OCEBM).

Electronic supplementary material

The online version of this article (10.1007/s00259-019-4263-9) contains supplementary material, which is available to authorized users.

Suitability of serum cytokine profiling for early diagnosis of implant-associated infections after orthopaedic surgery: A preliminary prospective study

The C-reactive protein (CRP) is still the conventional marker used to diagnose implant-associated infections (IAI) after orthopaedic surgery. However, the CRP level can lead to misdiagnosis since it is up-regulated not only during bacterial infection. In this prospective study, we evaluated the serum cytokine profile before (pre-OP) and after orthopaedic surgery (post-OP) as well as after confirmation of a developed infection (COI) to identify candidate biomarkers for diagnosis of IAI. Sera from 10 controls 7 to 1 days pre-OP and 0 to 22 days post-OP as well as from 5 patients who developed IAI 5 to 1 days pre-OP, 0 to 197 days post-OP and after COI were analyzed for 27 different cytokines using a multiplex cytokine assay. In addition to CRP, 14 cytokines IL-1ra, IL-4, IL-5, IL-6, IL-8, IL-12(p70), IL-13, IL-17, eotaxin, G-CSF, IFN-γ, IP-10, MCP-1, and MIP-1β were significantly altered (P ≤ 0.05) during the study although some differences were low-fold elevations compared to the pre-OP levels. IL-6 as well as IL-12(p70) were consistently elevated in infected patients. Surgery influenced cytokine production with some overlap of cytokines in both groups, implying that the use of cytokines is maximized when the cytokines are not or no longer affected by surgical trauma. To lend more robustness to the selection of candidate cytokines, in addition to the statistical differences, we applied a threshold cut-off of approximately 2-fold elevations when comparisons were made. This resulted in the selection of 8 cytokines, namely IL-6, IL-1ra, IL-8, IL-12(p70), eotaxin, IP-10, MCP-1, and MIP-1β, which may be used in a multiplex assay for detection of IAI after surgery. Furthermore, IL-1ra and IL-8 may be used as prognostic cytokines prior to surgery. The present results imply that the use of cytokines may be a suitable alternative to CRP for IAI diagnosis.

Periprosthetic Joint Infection in Patients with Inflammatory Joint Disease: Prevention and Diagnosis

PURPOSE OF REVIEW

Periprosthetic joint infection (PJI) is a devastating complication that can occur following total joint arthroplasty (TJA), causing significant morbidity and often requiring revision surgery. This goal of this manuscript is to review the current evidence for the prevention and diagnosis of PJI in patients with inflammatory arthritis.

RECENT FINDINGS

Patients with inflammatory arthritis have a higher risk of PJI after TJA; however, there are several preventive, diagnostic, and therapeutic measures that can be optimized to lower the burden of PJI in this population. This manuscript will review the current evidence and clinical practice recommendations that support specific features of preoperative evaluation, perioperative medication management, and surgical planning in inflammatory arthritis patients undergoing TJA. Evidence and recommendations for the diagnosis of PJI in this patient population will also be reviewed. Despite increased research efforts directed towards PJI, specific approaches directed at the inflammatory arthritis patient population remain surprisingly limited. Optimization strategies such as adequately managing disease-modifying medications, treating preoperative anemia, encouraging smoking cessation, and improving weight management are strongly encouraged before entering the perioperative period. If PJI does occur in the inflammatory arthritis patient, establishing the diagnosis is challenging, since guidelines were created from investigations of PJI in primarily patients without inflammatory arthritis. Future prospective research is required to better guide clinicians in preventing and diagnosing PJI in inflammatory arthritis patients undergoing TJA.

Joint aspiration, including culture of reaspirated saline after a 'dry tap', is sensitive and specific for the diagnosis of hip and knee prosthetic joint infection

Aims

The aim of this study was to establish the diagnostic accuracy of culture of joint aspirate with and without saline injection-reaspiration.

Patients and Methods

This is a retrospective analysis of 580 hip and knee aspirations in patients who were deemed to have a moderate to high risk of infection, and who subsequently proceeded to revision arthroplasty over a period of 12 years. It was carried out at a large quaternary referral centre where preoperative aspiration is routine.

Results

Fluid was aspirated primarily in 313 (54%) cases and after saline injection-reaspiration of a 'dry tap' in 267 (46%) cases. Overall sensitivity and specificity of the diagnostic aspirate were 84% (78% to 89%) and 85% (81% to 88%), respectively. Sensitivity and specificity of saline injection-reaspiration after 'dry tap' were 87% (79% to 92%) and 79% (72% to 84%) compared with 81% (71% to 88%) and 90% (85% to 93%) for direct aspiration.

Conclusion

Preoperative joint aspiration and culture is a sensitive and specific test for the confirmation of diagnosis in patients at a moderate to high risk of prosthetic joint infection. Culture of saline injection-reaspiration also provides accurate diagnostic information in the event of a 'dry tap'. Both methods allow susceptibility testing of relevant organisms and are therefore able to guide perioperative antibiotic therapy. Cite this article: Bone Joint J 2018;100-B:749-54.

Prosthetic Joint Infections: an Update

PURPOSE OF REVIEW

Prosthetic joint infection (PJI) is a rare but serious complication that is frequently misdiagnosed. We aimed to highlight the nuances of PJI diagnosis and antimicrobial therapies and provide clarity in key areas of management.

RECENT FINDINGS

Current research in PJI centers on a potential role for diagnostic biomarkers, molecular techniques, and implant sonication to reduce culture-negativity rates. The optimal duration of antimicrobial therapy remains controversial. A high clinical index of suspicion for PJI combined with data from multiple preoperative and intraoperative tests enables timely diagnosis and treatment. Biomarkers, molecular methods, and implant sonication are currently adjunctive to traditional diagnostic techniques. Shorter courses of antimicrobial therapies as well as the role of chronic suppressive therapy need confirmation by randomized controlled trials. Existing practices for preoperative dental prophylaxis and treatment of asymptomatic bacteriuria warrant revision based on evidence arguing against risk for PJI.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty

Total knee arthroplasty (TKA) is the most commonly performed joint replacement procedure in the United States and annual demand for primary TKA is expected to grow by 673% by 2030. The first part provides an overview of imaging modalities (radiographs, CT, MRI, ultrasound, and various nuclear medicine studies) and discusses their usefulness in the imaging evaluation of TKA. The second part focuses on evidence-based imaging and imaging-guided intervention algorithms for the workup of TKA and its complications, including routine follow-up, component wear, periprosthetic infection, aseptic loosening, granulomas/osteolysis, conventional and rotational instability, periprosthetic fracture, patellar complications, and a variety of periprosthetic soft tissue abnormalities. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Detecting the Presence of Bacterial DNA and RNA by Polymerase Chain Reaction to Diagnose Suspected Periprosthetic Joint Infection after Antibiotic Therapy

OBJECTIVE

To explore the diagnostic efficiency of DNA-based and RNA-based quantitative polymerase chain reaction (qPCR) analyses for periprosthetic joint infection (PJI).

METHODS

To determine the detection limit of DNA-based and RNA-based qPCR in vitro, Staphylococcus aureus and Escherichia coli strains were added to sterile synovial fluid obtained from a patient with knee osteoarthritis. Serial dilutions of samples were analyzed by DNA-based and RNA-based qPCR. Clinically, patients who were suspected of having PJI and eventually underwent revision arthroplasty in our hospital from July 2014 to December 2016 were screened. Preoperative puncture or intraoperative collection was performed on patients who met the inclusion and exclusion criteria to obtain synovial fluid. DNA-based and RNA-based PCR analyses and culture were performed on each synovial fluid sample. The patients' demographic characteristics, medical history, and laboratory test results were recorded. The diagnostic efficiency of both PCR assays was compared with culture methods.

RESULTS

The in vitro analysis demonstrated that DNA-based qPCR assay was highly sensitive, with the detection limit being 1200 colony forming units (CFU)/mL of S. aureus and 3200 CFU/mL of E. coli. Meanwhile, The RNA-based qPCR assay could detect 2300 CFU/mL of S. aureus and 11 000 CFU/mL of E. coli. Clinically, the sensitivity, specificity, and accuracy were 65.7%, 100%, and 81.6%, respectively, for the culture method; 81.5%, 84.8%, and 83.1%, respectively, for DNA-based qPCR; and 73.6%, 100%, and 85.9%, respectively, for RNA-based qPCR.

CONCLUSIONS

DNA-based qPCR could detect suspected PJI with high sensitivity after antibiotic therapy. RNA-based qPCR could reduce the false positive rates of DNA-based assays. qPCR-based methods could improve the efficiency of PJI diagnosis.

Oral Therapy, Microbiological Findings, and Comorbidity Influence the Outcome of Prosthetic Joint Infections Undergoing 2-Stage Exchange

BACKGROUND

The aim of the present study was to investigate potential predictive factors of an unfavorable outcome in patients with prosthetic joint infection (PJI) undergoing 2-stage exchange.

METHODS

Patients with PJI undergoing 2-stage exchange and observed over a 5-year period (2009-2013) were included. Cure was defined by the disappearance of infection after a 96-week follow-up period. Statistical analysis was performed using the Mann-Whitney U test, the Fisher exact test, and the multivariate analysis.

RESULTS

One-hundred twenty-two patients with PJI were included (median age, 69 years [range, 36-80 years]; 48% males, 47 hip PJI, and 75 knee PJI). Known comorbidities related to an increased risk of infection were reported in 43 patients (35%). Microbiological definition was obtained in 101 (83%) patients, and Staphylococcus aureus was isolated in 44 (36%) patients. Coagulase-negative staphylococci were isolated in 41 (34%) patients. A favorable outcome was obtained in 102 of 122 patients (84%). After univariate analysis, bacterial growth from operative specimens (P = .007), growth of Gram-positive bacteria (P < .001), use of oral therapy (P = .01), and absence of known comorbidities (P = .02) were associated with favorable outcome. Administration of rifampin (P = .99) and results of blood analysis were not predictive of outcome. After multivariate analysis was applied, infection sustained by Gram-positive bacteria, administration of oral antibiotics, and absence of known comorbidities frequently resulted in favorable outcome.

CONCLUSION

A favorable outcome in patients with PJI undergoing 2-stage procedure was associated with an infection sustained by Gram-positive bacteria, absence of known comorbidities, and administration of oral therapy. Therefore, failure rate can be reduced with appropriate treatment choices.

What is the Diagnostic Accuracy of Aspirations Performed on Hips With Antibiotic Cement Spacers?

BACKGROUND

Periprosthetic joint infection is a serious complication after THA and commonly is treated with a two-stage revision. Antibiotic-eluting cement spacers are placed for local delivery of antibiotics. Aspirations may be performed before the second-stage reimplantation for identification of persistent infection. However, limited data exist regarding the diagnostic parameters of synovial fluid aspiration with or without saline lavage from a hip with an antibiotic-loaded cement spacer.

QUESTIONS/PURPOSES

We asked: (1) For hips with antibiotic cement spacers, does saline lavage influence the diagnostic validity of aspirations? (2) What is the diagnostic accuracy of preoperative aspirations performed on hips with antibiotic cement spacers using the Musculoskeletal Infection Society (MSIS) criteria, stratified by saline and nonlavage? (3) For hips with antibiotic spacers, what are the optimal thresholds for synovial fluid white blood cell (WBC) count and polymorphonuclear neutrophil (PMN) percentage for diagnosing infections?

METHODS

One hundred seventy-four hips (155 patients) with antibiotic-eluting cement spacers inserted between October 2012 and July 2015 were reviewed. Of these, 98 hips (80 patients) met the inclusion criteria and were included in the analysis (77 nonlavage, 21 saline lavage aspirations). Laboratory data from the aspiration and preoperative workup and intraoperative details were collected. Infection status of each hip procedure was determined based on a modified MSIS criteria using serologic, histologic, and intraoperative findings (sinus tract communicating with the joint at surgery or two positive intraoperative periprosthetic cultures with the same organism or two of the three following criteria: elevated erythrocyte sedimentation rate [ESR] [> 30 mm/hour] and C-reactive protein [CRP] [> 10 mg/L], a single positive intraoperative periprosthetic tissue culture, or a positive histologic analysis of periprosthetic tissue [> 5 neutrophils per high power field]). The diagnostic parameters were calculated for the MSIS criteria thresholds for synovial fluid (ie, WBC count > 3000 cells/µL and PMN percentage > 80%). Optimal thresholds were calculated for the corrected synovial WBC count and PMN percentage with a receiver operating characteristic curve. Separate analyses were performed for the hips with successful aspirations (nonlavage group) and those with saline lavage aspirations.

RESULTS

The WBC count and PMN percentage were higher in hips with infection than in hips without infection when nonlavage aspirations were done (WBC count, 6680 cells/µL ± 6980 cells/µL vs 2001 ± 4825; mean difference, 4679; 95% CI, 923-8436; p = 0.015; PMN percentage, 83% ± 13% vs 44% ± 30%; mean difference, 39%; 95% CI, 39%-49%; p < 0.001) and the findings between infected and noninfected aspirations were not different when saline lavage aspirations were done (WBC count, 782 cells/µL ± 696 vs 307 cells/µL ± 343; mean difference, 475; 95% CI, -253 to 1203; p = 0.161; PMN percentage, 67% ± 15% vs 58% ± 28%; mean difference, 10%; 95% CI, -11% to 30%; p = 0.331). Aspirations performed without lavage yielded good diagnostic accuracy in all parameters (WBC count, 78% [95% CI, 70%-86%]; PMN percentage. 79% [95% CI, 70%-88%]; positive culture: 84% [95% CI, 81%-90%]; at least one of the above: 79% [95% CI, 70%-88%]); but in the saline lavage group, none had WBC counts above the threshold (diagnostic accuracies for WBC count, 0%; PMN percentage, 71% [95% CI, 62%-86%]; positive culture, 76% [95% CI, 76%-86%]; at least one: 71% [95% CI, 57%-91%]). Because saline lavage did not result in differences between aspirations from infected and noninfected hips, we calculated the optimal thresholds in the nonlavage group only; the optimal threshold for synovial WBC count was 1166 cells/µL and for synovial PMN the percentage was 68%, which corresponds to WBC count diagnostic accuracy of 78% (95% CI, 69%-87%) and PMN percentage accuracy of 78% (95% CI, 69%-87%).

CONCLUSIONS

Because the MSIS criteria thresholds resulted in suboptimal sensitivities owing to a higher number of false negatives, we recommend considering lower WBC count and PMN percentage thresholds for hip-spacer aspirations. Furthermore, the WBC count and PMN percentage results from aspirations performed with saline lavage are not reliable for treatment decisions.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Drain Tip Culture is Not Prognostic for Surgical Site Infection in Spinal Surgery Under Prophylactic Use of Antibiotics

STUDY DESIGN

A retrospective observational study.

OBJECTIVE

We evaluated the prognostic value of drain tip culture performed for surgical site infection (SSI) after spinal surgery with a large number of subjects, and investigated whether the type of surgery or timing of drain removal correlated with positive drain culture and SSI rates.

SUMMARY OF BACKGROUND DATA

In many institutions, routine culture of suction drain tips that are placed in the surgical site of spinal surgeries has been performed to detect contamination after removal. However, few reports have evaluated whether drain tip culture is prognostic for SSI after spinal surgery.

METHODS

A total of 1240 suction drain tips that had been used in spinal surgeries were cultured after removal. Prophylactic antibiotics were administered during and after the surgery for 48 hours. We evaluated the correlation between the results of positive drain tip culture, SSI, and drain removal timing.

RESULTS

Positive drain tip cultures were found in 55 cases (4.4%). True SSI was identified in 18 cases (1.5%). The most frequently isolated microorganism in the both cases was Staphylococcus. The sensitivity of drain tip culture for SSI after spinal surgery was calculated as 0% according to the concordance rate between bacteria isolated in drain tip culture and SSI cases. There was no correlation between the duration of suction drainage and the drain tip culture results or the onset of SSI within 72 hours. The results of suction drain tip culture could not reflect those of SSI regardless of the type of surgery (primary or revision), surgical region, surgical procedure, or implant use.

CONCLUSION

Drain tip culture in spinal surgery was not prognostic for SSI or helpful in detecting pathogenic bacteria for SSI. Routine use of drain tip culture when prophylactic antibiotics are used is not supported by the results of this study.

LEVEL OF EVIDENCE

4.

Failure of the first step of two-stage revision due to polymicrobial prosthetic joint infection of the hip

Background

The unsuccessful treatment of prosthetic joint infection (PJI) with two-stage revision leads to infection recurrence. The objectives of the study were to assess the clinical and demographic characteristics of patients with polymicrobial PJI, and to evaluate the role of the microbial profile involved in PJI in the risk of infection recurrence after the first step of two-stage revision surgery.

Materials and methods

A retrospective analysis of 189 cases of culture-positive PJI following total hip replacement over a 5-year period was performed. The demographic characteristics of patients, clinical symptoms, microbiology cultures of intraoperative biopsies, laboratory values of C-reactive protein (CRP), white blood cell count and erythrocyte sedimentation rate were analyzed. Patients were divided into two groups—135 with monomicrobial and 54 with polymicrobial infection.

Results

Of all patients, 68.9 % in the monomicrobial and 83.3 % in the polymicrobial group had a body mass index >25 kg/m² (p = 0.05). The median CRP values were 5.7 mg/L (IQR 4.0–10.0 mg/L) in the monomicrobial compared to 8.8 mg/L (IQR 5.0–27 mg/L) in the polymicrobial group (p = 0.01). The percentage of successful outcomes was 27.8 % in patients with microbial associations (p < 0.0001). Gram-negative pathogens caused polymicrobial PJI in 61.5 % of cases with infection recurrence (OR 4.4; 95 % CI 1.18–16.37; p = 0.03).

Conclusions

Overweight and obese patients or those with elevated CRP had a greater risk of polymicrobial PJI. They were predisposed to recurrence of infection after the first step of two-stage revision. An unsuccessful outcome was more likely in cases with polymicrobial infection compared to those with monomicrobial infection. In addition, the presence of multidrug-resistant strains of Gram-negative bacteria substantially increased the risk of PJI treatment being unsuccessful.

Level of evidence

Level III, therapeutic study.

Enrichment of bacteria samples by centrifugation improves the diagnosis of orthopaedics-related infections via real-time PCR amplification of the bacterial methicillin-resistance gene

Background

To effectively treat orthopaedic infections by methicillin-resistant strains, an early diagnosis is necessary. Bacterial cultures and real-time polymerase chain reaction (PCR) have been used to define methicillin-resistant staphylococci. However, even when patients display clinical signs of infections, bacterial culture and real-time PCR often cannot confirm infection. The aim of this study was to prospectively compare the utility of real-time PCR for the mecA gene detection following centrifugation of human samples with suspected orthopaedic infections.

Results

In addition to the conventional real-time PCR method, we performed real-time PCR following centrifugation of the sample at 4,830×g for 10 min in a modified real-time PCR (M-PCR) method. We suspended cultured methicillin-resistant Staphylococcus aureus and generated standard dilution series for in vitro experiments. The in vitro detection sensitivity of the M-PCR method was approximately 5.06 times higher than that of the conventional real-time PCR method. We performed bacterial culture, pathological examination, real-time PCR, and M-PCR to examine the infectious fluids and tissues obtained from 36 surgical patients at our hospital. Of these, 20 patients who had undergone primary total hip arthroplasty were enrolled as negative controls. In addition, 15 patients were examined who were clinically confirmed to have an infection, including periprosthetic joint infection (eight patients), pyogenic spondylitis (two patients), infectious pseudoarthrosis (two patients), and after spine surgery (three patients). In one sample from a patient who developed infectious pseudoarthrosis and two samples from surgical site infections after spine surgery, the mecA gene was detected only by the M-PCR method. In one patient with infectious pseudoarthrosis, one patient with infection after arthroplasty, and two patients with purulent spondylitis, the detection sensitivity of the M-PCR method was increased compared with PCR (clinical sample average: 411.6 times).

Conclusions

These findings suggest that the M-PCR method is useful to detect methicillin-resistant strains infections. In addition, the centrifugation process only takes 10 min longer than conventional real-time PCR methods. We believe that the M-PCR method could be clinically useful to detect orthopaedic infections caused by methicillin-resistant strains.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1180-2) contains supplementary material, which is available to authorized users.

The "true" incidence of surgically treated deep prosthetic joint infection after 32,896 primary total hip arthroplasties: a prospective cohort study

BACKGROUND AND PURPOSE

It has been suggested that the risk of prosthetic joint infection (PJI) in patients with total hip arthroplasty (THA) may be underestimated if based only on arthroplasty registry data. We therefore wanted to estimate the "true" incidence of PJI in THA using several data sources.

PATIENTS AND METHODS

We searched the Danish Hip Arthroplasty Register (DHR) for primary THAs performed between 2005 and 2011. Using the DHR and the Danish National Register of Patients (NRP), we identified first revisions for any reason and those that were due to PJI. PJIs were also identified using an algorithm incorporating data from microbiological, prescription, and clinical biochemistry databases and clinical findings from the medical records. We calculated cumulative incidence with 95% confidence interval.

RESULTS

32,896 primary THAs were identified. Of these, 1,546 had first-time revisions reported to the DHR and/or the NRP. For the DHR only, the 1- and 5-year cumulative incidences of PJI were 0.51% (0.44-0.59) and 0.64% (0.51-0.79). For the NRP only, the 1- and 5-year cumulative incidences of PJI were 0.48% (0.41-0.56) and 0.57% (0.45-0.71). The corresponding 1- and 5-year cumulative incidences estimated with the algorithm were 0.86% (0.77-0.97) and 1.03% (0.87-1.22). The incidences of PJI based on the DHR and the NRP were consistently 40% lower than those estimated using the algorithm covering several data sources.

INTERPRETATION

Using several available data sources, the "true" incidence of PJI following primary THA was estimated to be approximately 40% higher than previously reported by national registries alone.

Performance characteristics of broth-only cultures after revision total joint arthroplasty

BACKGROUND

Surgeons frequently obtain intraoperative cultures at the time of revision total joint arthroplasty. The use of broth or liquid medium before applying the sample to the agar medium may be associated with contamination and false-positive cultures; however, the degree to which this is the case is not known.

QUESTIONS/PURPOSES

We (1) calculated the performance characteristics of broth-only cultures (sensitivity, specificity, positive predictive value, and negative predictive value) and (2) characterized the organisms identified in broth to determine whether a specific organism showed increased proclivity for true-positive periprosthetic joint infection (PJI).

METHODS

A single-institution retrospective chart review was performed on 257 revision total joint arthroplasties from 2009 through 2010. One hundred ninety (74%) had cultures for review. All culture results, as well as treatment, if any, were documented and patients were followed for a minimum of 1 year for evidence of PJI. Cultures were measured as either positive from the broth only or broth negative. The true diagnosis of infection was determined by the Musculoskeletal Infection Society criteria during the preoperative workup or postoperatively at 1 year for purposes of calculating the performance characteristics of the broth-only culture.

RESULTS

The sensitivity, specificity, positive predictive value, and negative predictive value were 19%, 88%, 13%, and 92%, respectively. The most common organism identified was coagulase-negative Staphylococcus (16 of 24 cases, 67%). Coagulase-negative Staphylococcus was present in all three true-positive cases; however, it was also found in 13 of the false-positive cases.

CONCLUSIONS

The broth-only positive cultures showed poor sensitivity and positive predictive value but good specificity and negative predictive value. The good specificity indicates that it can help to rule in the presence of PJI; however, the poor sensitivity makes broth-only culture an unreliable screening test. We recommend that broth-only culture results be carefully scrutinized and decisions on the diagnosis and treatment of infection should be based specifically on the Musculoskeletal Infection Society criteria.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

Deep infection after total hip replacement: a method for national incidence surveillance

OBJECTIVE

The purpose of this study was to estimate the incidence of deep periprosthetic joint infections (PJIs) after primary total hip replacement (THR) in Sweden prior to the introduction of a national initiative to reduce these infections.

DESIGN

Prospective open cohort study with 2 years follow-up of each subject.

SETTING

All THR-performing clinics in Sweden.

METHODS

All patients registered for a primary THR in the Swedish Hip Arthroplasty Register between July 1, 2005, and December 31, 2008, were selected for the study (45,531 patients with 49,219 THRs) and were matched with the Swedish Prescribed Drug Register. All patients with a minimum of 4 weeks of continuous outpatient antibiotic treatment within 2 years after their primary THR (1,989 patients with 2,219 THRs) were selected for a medical records review, and the number of cases with PJI was determined.

RESULTS

The cumulative incidence of PJI within 2 years after primary THR was 0.9% (95% confidence interval, 0.85-1.02; n = 443), and 405 of these had been reoperated. The incidence rate of PJI for the first 3 months was 5 per 10,000 THR-weeks and, thereafter, 0.3 per 10,000 THR-weeks. Staphylococcus aureus and coagulase-negative staphylococci were the most common bacteria isolated.

CONCLUSIONS

This study describes a new method of national postoperative infection surveillance. The incidence is similar to previous smaller reports and is useful for monitoring changes over time to evaluate the national initiative to reduce infections.

Effects of Low-intensity Pulsed Ultrasound and Cryotherapy on Recovery of Joint Function and C-reactive Protein Levels in Patients after Total Knee Replacement Surgery

[Purpose] We investigated the effect of low-intensity pulsed ultrasound and cryotherapy on joint function recovery and C-reactive protein (CRP) levels of patients with total knee replacement. [Subjects] Forty-six patients with total knee replacement were recruited and allocated to either low-intensity pulsed ultrasound therapy (n=15), cryotherapy (n=15), or a combination of both (n=16). Therapy was administered once a day, 5 times a week for 3 weeks. To determine functional joint recovery and reduction of inflammation, changes in the Korean Western Ontario and McMaster Universities Arthritis Index (K-WOMAC), range of motion (ROM), and CRP were assessed postsurgically and four times over a 3-week period. Using one-way analysis of variance (ANOVA), homogeneity tests were performed based on participants’ general characteristics. To recognize changes in time-variant K-WOMAC, ROM, and CRP values between groups, repeated measures ANOVA was performed, and Tukey’s test was used for post-test analysis. Values at α=0.05 were considered significant. [Results] We found a difference between groups and times, and the group that received the combined therapies showed greater changes in outcomes than the group that received low-intensity pulsed ultrasound therapy alone. [Conclusion] Applying both low-intensity pulsed ultrasound and cryotherapy can relieve inflammation and enhance joint function in patients who undergo total knee replacement.

Factors related to outcome of early and delayed prosthetic joint infections

In this prospective study, we evaluate the impact of adherence to a diagnostic and therapeutic protocol on prosthetic joint infections (PJI) diagnostic accuracy and outcome.

PATIENTS AND METHODS

Patients with early or delayed PJI referred over a 5-year period were included. Diagnosis was based on characteristic clinical signs, radiographic findings and microbiological evidence. Antibiotics were chosen on the basis of microbiological findings, and drugs active against methicillin-resistant staphylococci were administered if no microbiological evidence had been obtained.

RESULTS

Inclusion criteria were met in 159 cases (median age 64 years, males 45%). 56 were early infections and 103 delayed infections. Comorbidities were reported in 99 (62%) cases. Positive cultures were obtained in 122/159 (77%), coagulase-negative staphylococci were cultured in 20%, Staphylococcus aureus in 28%, and Pseudomonas aeruginosa in 7%. In early infections, cure rate after debridement and antibiotic therapy was 80%. In delayed infections, cure rate after two-stage exchange was 85%. Of 28 patients with delayed infection treated with antibiotics without surgery, only 8 (29%) infections were suppressed 48 weeks after treatment discontinuation. Rifampin afforded a better outcome.

CONCLUSION

Appropriate diagnostic and surgical procedures and microbiologically driven antibiotic therapy including rifampin are recommended to improve diagnostic accuracy and outcome.

Septic bursitis in an 8-year-old boy

Background. The prepatellar bursa can become inflamed owing to repeated trauma. Prepatellar bursitis is extremely rare in children. Methods. We report the case of an 8-year-old boy who was treated for an erythematous, swollen, and severely painful right knee, fever, inability to bear weight on the leg, and purulent material draining from a puncture wound. We describe the differential diagnosis for tender swollen knee, including infection, gout, rheumatoid arthritis, and osteoarthritis. If untreated, prepatellar bursitis can progress to patellar osteomyelitis. Results. Wound cultures grew Streptococcus pyogenes, with the infection resolving with amoxicillin. Conclusions. A high index of suspicion is necessary in children presenting with prepatellar bursitis to prevent potentially devastating sequelae of infection of the septic joint.

Sensitivities, specificities, and predictive values of microbiological culture techniques for the diagnosis of prosthetic joint infection

Background. Identifying the microorganism in a prosthetic joint infection is the key to appropriately targeting antimicrobial treatment. Despite the availability of various techniques, no single test is considered the definitive gold standard. Aim. Our aim was to determine the sensitivity, specificity, and positive/negative predictive values for a variety of culture techniques. Methods. We performed a retrospective case series of 219 patients undergoing revision surgery of their hip or knee replacement between May 2004 and February 2013. The patients were classified as either infected or noninfected according to criteria set out by the Musculoskeletal Infection Society. The number and type of samples taken intraoperatively varied between cases but included tissue samples and fluid sent in either blood culture vials or sterile containers. Results. The highest sensitivity was found with blood culture vials (0.85) compared to fluid in sterile containers (0.26) and tissues samples (0.32). Blood culture vials also had a better specificity and positive and negative predictive values profile. Conclusion. We conclude that, of the techniques studied, fluid in blood culture vials had the best profile for the correct identification of microorganisms and advocate its use.

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

PURPOSE

The pre-operative differentiation between periprosthetic joint infection (PJI) and aseptic loosening after total hip (THA) or knee (TKA) arthroplasty is essential for successful therapy and relies in part on the use of molecular markers. The objective of this study was to assess serum levels of lipopolysaccharide-binding protein (LBP) as a diagnostic tool for PJI and to compare its accuracy with standard tests.

METHODS

One hundred and twenty patients presenting with a painful TKA or TKA with indication for surgical revision were included in this prospective, controlled, clinical trial at a single centre. Pre-operative blood and serum samples were collected and analysed for white blood cell (WBC) count, C-reactive protein (CRP) and LBP. The definite diagnosis of periprosthetic joint infection was determined on the basis of clinical, microbiological and histopathological examination.

RESULTS

LBP showed significantly higher values in PJI compared with aseptic loosening (p < 0.001) and control (p < 0.001), with a specificity of 66% and a sensitivity of 71% at a cutoff value of >7 ng/ml. In combination with CRP, the positive predictive value for PJI was at 0.67; negative predictive value with both negative was at 0.77.

DISCUSSION

Patients with PJI have elevated serum levels of LBP when compared with patients with aseptic loosening. The use of LBP in serum appears not to be a more accurate marker than CRP level in serum for detecting PJI. On the basis of these results, we cannot recommend the sole use of LBP for differentiating PJI and aseptic loosening following THA and TKA.

Serum interleukin-6 as a marker of periprosthetic shoulder infection

BACKGROUND

Infection after shoulder arthroplasty can be a devastating complication, and subacute and chronic low-grade infections have proven difficult to diagnose. Serum marker analyses commonly used to diagnose periprosthetic infection are often inconclusive. The purpose of this study was to evaluate the effectiveness of serum interleukin-6 (IL-6) as a marker of periprosthetic shoulder infection.

METHODS

A prospective cohort study of thirty-four patients who had previously undergone shoulder arthroplasty and required revision surgery was conducted. The serum levels of IL-6 and C-reactive protein (CRP), the erythrocyte sedimentation rate (ESR), and the white blood-cell count (WBC) were measured. The definitive diagnosis of an infection was determined by growth of bacteria on culture of intraoperative specimens. Two-sample Wilcoxon rank-sum (Mann-Whitney) tests were used to determine the presence of a significant difference in the ESR and WBC between patients with and those without infection, while the Fisher exact test was used to assess differences in IL-6 and CRP levels between those groups. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of each marker were also calculated.

RESULTS

There was no significant difference in the IL-6 level, WBC, ESR, or CRP level between patients with and those without infection. With a normal serum IL-6 level defined as <10 pg/mL, this test had a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 0.14, 0.95, 0.67, 0.61, and 0.62, respectively.

CONCLUSIONS

IL-6 analysis may have utility as a confirmatory test but is not an effective screening tool for periprosthetic shoulder infection. This finding is in contrast to the observation, in previous studies, that IL-6 is more sensitive than traditional serum markers for periprosthetic infection.

2-stage revision recommended for treatment of fungal hip and knee prosthetic joint infections

BACKGROUND AND PURPOSE

Fungal prosthetic joint infections are rare and difficult to treat. This systematic review was conducted to determine outcome and to give treatment recommendations.

PATIENTS AND METHODS

After an extensive search of the literature, 164 patients treated for fungal hip or knee prosthetic joint infection (PJI) were reviewed. This included 8 patients from our own institutions.

RESULTS

Most patients presented with pain (78%) and swelling (65%). In 68% of the patients, 1 or more risk factors for fungal PJI were found. In 51% of the patients, radiographs showed signs of loosening of the arthroplasty. Candida species were cultured from most patients (88%). In 21% of all patients, fungal culture results were first considered to be contamination. There was co-infection with bacteria in 33% of the patients. For outcome analysis, 119 patients had an adequate follow-up of at least 2 years. Staged revision was the treatment performed most often, with the highest success rate (85%).

INTERPRETATION

Fungal PJI resembles chronic bacterial PJI. For diagnosis, multiple samples and prolonged culturing are essential. Fungal species should be considered to be pathogens. Co-infection with bacteria should be treated with additional antibacterial agents. We found no evidence that 1-stage revision, debridement, antibiotics, irrigation, and retention (DAIR) or antifungal therapy without surgical treatment adequately controls fungal PJI. Thus, staged revision should be the standard treatment for fungal PJI. After resection of the prosthesis, we recommend systemic antifungal treatment for at least 6 weeks-and until there are no clinical signs of infection and blood infection markers have normalized. Then reimplantation can be performed.

Diagnosis of prosthetic joint infection by use of PCR-electrospray ionization mass spectrometry

We compared PCR-electrospray ionization mass spectrometry (PCR-ESI/MS) to culture using sonicate fluid from 431 subjects with explanted knee (n = 270) or hip (n = 161) prostheses. Of these, 152 and 279 subjects had prosthetic joint infection (PJI) and aseptic failure, respectively. The sensitivities for detecting PJI were 77.6% for PCR-ESI/MS and 69.7% for culture (P = 0.0105). The specificities were 93.5 and 99.3%, respectively (P = 0.0002).

Preoperative aspiration culture for preoperative diagnosis of infection in total hip or knee arthroplasty

This meta-analysis evaluated preoperative aspiration culture for diagnosing prosthetic joint infection (PJI) in total hip arthroplasty (THA) and total knee arthroplasty (TKA). The pooled sensitivity and specificity were 0.72 (95% confidence interval, 0.65 to 0.78) and 0.95 (0.93 to 0.97), respectively. Subgroup analyses revealed nonsignificant worse diagnostic performance for THA than for TKA (sensitivity, 0.70 versus 0.78; specificity, 0.94 versus 0.96). Preoperative aspiration culture has moderate to high sensitivity and very high specificity for diagnosing PJI.

Periprosthetic joint infection in patients with inflammatory joint disease: a review of risk factors and current approaches to diagnosis and management

BACKGROUND

Prevention, early identification, and effective management of periprosthetic joint infection (PJI) in patients with inflammatory joint disease (IJD) present unique challenges for physicians. Discontinuing disease-modifying anti-rheumatoid drugs (DMARDs) perioperatively may reduce immunosuppression and infection risk at the expense of increasing disease flares. Interpreting traditional diagnostic markers of PJI can be difficult due to disease-related inflammation.

PURPOSES

This review is designed to answer how to (1) manage immunosuppressive/DMARD therapy perioperatively, (2) diagnose PJI in patients with IJD, and (3) treat PJI in this population.

METHODS

The PubMed database was searched for relevant articles with subsequent review by independent authors.

RESULTS

While there is evidence to support the use of methotrexate perioperatively in RA patients, it remains unclear whether using anti-tumor necrosis factor medications perioperatively increases the risk of surgical site infections. Serum erythrocyte sedimentation rate and C-reactive protein can be useful for diagnosis of PJI in this population, but only as part of comprehensive workup that ultimately relies upon sampling of joint fluid. Management of PJI depends on several clinical factors including duration of infection and the likelihood of biofilm presence, the infecting organism, sensitivity to antibiotic therapy, and host immune status. The evidence suggests that two-stage revision or resection arthroplasty is more likely to eradicate infection, particularly when MRSA is the pathogen.

CONCLUSION

Immunosuppression and baseline inflammatory changes in the IJD population can complicate the prevention, diagnosis, and treatment of PJI. Understanding the increase in risk associated with IJD and its treatment is essential for proper management when patients undergo lower extremity arthroplasty.