Diagnosis of periprosthetic joint infection

The World Association against Infection in Orthopaedics and Trauma (WAIOT) procedures for Microbiological Sampling and Processing for Periprosthetic Joint Infections (PJIs) and other Implant-Related Infections

While implant-related infections continue to play a relevant role in failure of implantable biomaterials in orthopaedic and trauma there is a lack of standardised microbiological procedures to identify the pathogen(s). The microbiological diagnosis of implant-related infections is challenging due to the following factors: the presence of bacterial biofilm(s), often associated with slow-growing microorganisms, low bacterial loads, previous antibiotic treatments and, possible intra-operative contamination. Therefore, diagnosis requires a specific set of procedures. Based on the Guidelines of the Italian Association of the Clinical Microbiologists (AMCLI), the World Association against Infection in Orthopaedics and Trauma has drafted the present document. This document includes guidance on the basic principles for sampling and processing for implant-related infections based on the most relevant literature. These procedures outline the main microbiological approaches, including sampling and processing methodologies for diagnostic assessment and confirmation of implant-related infections. Biofilm dislodgement techniques, incubation time and the role of molecular approaches are addressed in specific sections. The aim of this paper is to ensure a standardised approach to the main microbiological methods for implant-related infections, as well as to promote multidisciplinary collaboration between clinicians and microbiologists.

Can we rely on the combination of serological tests and frozen sections at the time of reimplantation for two-stage exchange hip arthroplasty in patients with a "dry tap"?

Purpose

The optimal timing of reimplantation of two-stage exchange arthroplasty for periprosthetic joint infection remains unknown. The purpose of the study was to (1) evaluate performance of combination of serum erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and frozen section in predicting persistent infection at the time of second-stage hip reimplantation and (2) compare accuracies of 5 and 10 polymorphonuclear neutrophils (PMNs) per high power field (HPF) as the threshold of frozen section.

Methods

We retrospectively reviewed 97 two-stage exchange hip arthroplasties from 2012–2016. Persistent infection at time of reimplantation was diagnosed using the Musculoskeletal Infection Society (MSIS) criteria. Two diagnostic models were developed. Model 1 utilized ESR, CRP, and > 5 PMNs/HPF on frozen section. Model 2 utilized ESR, CRP, and > 10 PMNs/HPF. Receiver operating characteristic (ROC) curves of the two models were generated, and areas under the curves (AUCs) were compared. A set of sensitivity analysis, using the Delphi-based consensus criteria for treatment success, was conducted to verify the accuracy of our models.

Results

The overall rate of infection at reimplantation was 14.4%. AUCs for models 1 and 2 were 0.709 (95% confidence interval [CI], 0.557–0.852) and 0.697 (95% CI, 0.529–0.847), respectively. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 57.1%, 88.0%, 44.4%, and 92.4%, respectively, in model 1 and 42.9%, 96.4%, 66.7%, and 90.9%, respectively, in model 2. Models 1 and 2 had no significant difference in predictive values (p = 0.821). Results remained robust in the sensitivity analysis.

Conclusions

This study reveals that the combination of serum ESR, CRP, and frozen section has limited diagnostic value in predicting persistent infection at reimplantation. Additionally, no significant difference in accuracies between 5 and 10 PMNs/HPF as the threshold of frozen section were found. There is a need for timely biomarkers with higher accuracy in diagnosing infection before reimplantation.

Positive Culture During Reimplantation Increases the Risk of Reinfection in Two-Stage Exchange Arthroplasty Despite Administrating Prolonged Antibiotics: A Retrospective Cohort Study and Meta-Analysis

BACKGROUND

The significance of a positive culture at reimplantation remains an important topic of consideration given the lack of clear metrics for when reimplantation can be performed. The purpose of this study is thus to investigate the (1) association between a positive culture during reimplantation and failure following 2-stage exchange arthroplasty and the (2) influence of prolonged antibiotics on these patients.

METHODS

We retrospectively reviewed 117 patients undergoing 2-stage exchange hip arthroplasty from 2012 to 2016. Of them, 23 had positive culture during reimplantation and were treated with 2 weeks of intravenous and 4 weeks of oral antibiotics following reimplantation. All patients had a minimum follow-up of 1 year. Logistic regression models were performed to identify association between positive culture and subsequent treatment failure. A meta-analysis was also performed to validate findings. A subgroup analysis was performed to explore whether 6-week antibiotics (oral, intravenous, or both) after reimplantation improved outcomes.

RESULTS

A total of 11 studies, which included 141 cases with a positive culture at reimplantation and 784 with negative cultures, were included in the meta-analysis. The pooled data showed a higher risk of failure in patients with a positive culture than those with a negative culture (41.1% vs 14.8%, odds ratio 4.58). The subgroup analysis revealed that 6 weeks of antibiotic administration following reimplantation decreased the odds of reinfection from 9.35 to 3.12. The findings in the retrospective cohort were consistent with those of the meta-analysis; the failure rate was significantly higher in patients with a positive culture than those with negative cultures (26.1% vs 6.4%, P < .001).

CONCLUSION

Six weeks of antibiotics appear to decrease the odds of reinfection after reimplantation. However, despite patients receiving 6 weeks of antibiotics after reimplantation, the risk of reinfection in patients with a positive culture at reimplantation is still more than 3 times higher than those with negative cultures. Further studies are needed to investigate optimal management for such patients.

The Leukocyte Esterase Test for Periprosthetic Joint Infection Is Not Affected by Prior Antibiotic Administration

BACKGROUND

It has been demonstrated that administration of antibiotics prior to performing diagnostic testing for periprosthetic joint infection can interfere with the accuracy of the standard diagnostic tests. Therefore, the purpose of this study was to evaluate the effects of antibiotic administration prior to performing the synovial leukocyte esterase strip test for periprosthetic joint infection.

METHODS

We identified 121 patients who underwent revision hip or knee arthroplasty for a Musculoskeletal Infection Society (MSIS)-confirmed periprosthetic joint infection. All patients also had a leukocyte esterase strip test performed. Patients in one group (32%) took antibiotics prior to the diagnostic workup, whereas patients in another group (68%) did not receive antibiotics within 2 weeks of the diagnostic workup. The leukocyte esterase strip test, erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP), synovial white blood-cell (WBC) count, and polymorphonuclear neutrophil (PMN) percentage were collected and were compared between the 2 groups.

RESULTS

The median serum ESR (85 compared with 67 mm/hr for patients who did not and did receive antibiotics; p = 0.009), CRP (16.5 compared with 12.9 mg/L; p = 0.032), synovial WBC count (45,675 compared with 9,650 cells/µL; p < 0.0001), and PMN percentage (93% compared with 88%; p = 0.004) were all significantly lower for patients receiving antibiotics. Furthermore, the administration of antibiotics resulted in a significant decrease in the sensitivity of all tests, except leukocyte esterase: ESR (79.5% in the antibiotics cohort compared with 92.7% in the no-antibiotics cohort [relative risk (RR) for false-negative results, 2.8; p = 0.04]), CRP (64.2% compared with 81.8% [RR, 1.9; p = 0.03]), WBC count (69.3% compared with 93.4% [RR, 5.0; p = 0.001]), PMN percentage (74.4% compared with 91.5% [RR, 3.0; p = 0.01]), and leukocyte esterase (78% compared with 83% [RR, 1.6; p = 0.17]). The rate of negative cultures was higher in the antibiotics group at 30.7% compared with the no-antibiotics group at 12.1% (p = 0.015).

CONCLUSIONS

This current study and previous studies have demonstrated that the administration of premature antibiotics can compromise the results of standard diagnostic tests for periprosthetic joint infection, causing significant increases in false-negative results. However, in this study, the leukocyte esterase strip test maintained its performance even in the setting of antibiotic administration. Antibiotic administration prior to diagnostic workups for periprosthetic joint infection stands to interfere with diagnosis. The leukocyte esterase strip test can be used as a reliable diagnostic marker for diagnosing periprosthetic joint infection even when prior antibiotics are administered.

LEVEL OF EVIDENCE

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

Can leucocyte esterase replace frozen sections in the intraoperative diagnosis of prosthetic hip infection?

AIMS

Leucocyte esterase (LE) has been shown to be an accurate marker of prosthetic joint infection (PJI), and has been proposed as an alternative to frozen section (FS) histology for intraoperative diagnosis. In this study, the intraoperative assessment of LE was compared with FS histology for the diagnosis of prosthetic hip infection.

PATIENTS AND METHODS

A total of 119 patients undergoing revision total hip arthroplasty (THA) between June 2015 and December 2017 were included in the study. There were 56 men and 63 women with a mean age of 66.2 years (27 to 88). Synovial fluid was collected before arthrotomy for the assessment of LE using enzymatic colourimetric strips. Between five and six samples were stained with haematoxylin and eosin for FS histology, and considered suggestive of infection when at least five polymorphonuclear leucocytes were found in five high-power fields.

RESULTS

The sensitivity and specificity of the LE assay were 100% and 93.8%, respectively; the positive (PPV) and the negative (NPV) predictive values were 79.3% and 100%, respectively. The mean time between the collection of the sample and the result being known was 20.1 minutes (sd 4.4). The sensitivity and specificity of FS histology were 78.3% and 96.9%, respectively; the PPV and the NPV were 85.7% and 94.9%, respectively. The mean time between the collection of the sample and the result being known was 27.2 minutes (sd 6.9).

CONCLUSION

The sensitivity of LE assay was higher, with similar specificity and diagnostic accuracy, compared with FS histology. The faster turnaround time, its ease of use, and low costs make LE assay a valuable alternative to FS histology. We now use it routinely for the intraoperative diagnosis of PJI. Cite this article: Bone Joint J 2019;101-B:372-377.

Alpha defensin, leukocyte esterase, C-reactive protein, and leukocyte count in synovial fluid for pre-operative diagnosis of periprosthetic infection

Synovial fluid analysis for diagnosis of prosthetic joint infections has gained increasing interest in the recent past when markers more specific for these infections than the serum ones have been identified. Despite the important steps forward, identification of a gold standard has not yet been identified. In this study, usefulness of alpha defensin, leukocyte esterase, C-reactive protein (CRP), and white blood cells (WBCs) in synovial fluids alone and in combination for diagnosis of prosthetic joint infection was evaluated. Synovial fluids from 32 infected and 34 not infected patients were analyzed. Sensitivity, specificity, positive and negative predictive values, diagnostic accuracy, and receiver-operating characteristic (ROC) curves were calculated for each parameter. Moreover, combination of coupled variables was also evaluated by logistic regression analysis. Sensitivity of alpha defensin, CRP, leukocyte count, and leukocyte esterase were 84.4%, 87.5%, 93.7%, and 93.8%, respectively. Specificity was 91.2% for leukocyte counts, 94.1% for alpha defensin, 97.0% for CRP, and 97.1% for leukocyte esterase. Diagnostic accuracy was 89.4% for alpha defensin, 92.4% for WBC counts and CRP, and 95.5% for leukocyte esterase. No statistical differences were observed in area under the curve (AUC) of the ROC curves of alpha defensin, CRP, and leukocyte counts. Logistic regression analysis applied to a model comprising all the variables showed an AUC higher than AUC of coupled variables. In conclusion, results of this study confirm the high sensitivity and specificity of synovial leukocyte esterase for diagnosis of prosthetic joint infection, also suggesting the need to assess a panel of markers to optimize diagnosis of these infections.

Persistent Wound Drainage After Total Joint Arthroplasty: A Narrative Review

BACKGROUND

Persistent wound drainage after total joint arthroplasty (TJA) is an important complication with potential substantial adverse consequences, in particular periprosthetic joint infection.

METHODS

This review evaluated the available literature regarding several issues in the field of persistent wound drainage after TJA and offers a classification of persistent wound drainage and an algorithmic approach to the decision-making process.

RESULTS

Available literature addressing the diagnosis and treatment of persistent wound drainage after TJA is scarce and an evidence-based clinical guideline is lacking. This is partially caused by the absence of a universally accepted definition of persistent wound drainage. In patients with persistent wound drainage, clinical signs and serological tests can be helpful in the diagnosis of a developing infection. Regarding the treatment of persistent wound drainage, nonsurgical treatment consists of absorbent dressings, pressure bandages, and temporary joint immobilization. Surgical treatment is advised when wound drainage persists for more than 5-7 days and consists of open debridement with irrigation and exchange of modular components and antimicrobial treatment.

CONCLUSION

Based on this literature review, we proposed a classification and algorithmic approach for the management of patients with persistent wound drainage after TJA. Hopefully, this offers the orthopedic surgeon a practical clinical guideline by finding the right balance between overtreatment and undertreatment, weighing the risks and benefits. However, this classification and algorithmic approach should first be evaluated in a prospective trial.

Routine Diagnostic Tests for Periprosthetic Joint Infection Demonstrate a High False-Negative Rate and Are Influenced by the Infecting Organism

BACKGROUND

Current guidelines recommend serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) as the first-line testing for evaluation of suspected periprosthetic joint infection, in addition to synovial white blood-cell (WBC) count and polymorphonuclear percentage. However, the sensitivity and other diagnostic measures of these tests using a standardized definition of periprosthetic joint infection and the influence of organisms on these inflammatory markers remain inadequately investigated.

METHODS

A retrospective review of an institutional database of 549 periprosthetic joint infection cases and 653 aseptic total joint arthroplasty revisions was performed. Periprosthetic joint infection was defined using major criteria from the International Consensus Meeting (ICM) on Periprosthetic Joint Infection. The mean inflammatory marker levels were compared among organisms with Student t tests and the proportions of elevated laboratory levels were compared among organisms with chi-square analyses. Receiver operating characteristic curve analyses were performed to calculate new cutoffs, sensitivities, and specificities for each organism and overall for serum CRP and ESR and synovial WBC and polymorphonuclear percentage.

RESULTS

The sensitivity of these markers for diagnosing chronic periprosthetic joint infection was 0.85 for ESR, 0.88 for CRP, 0.83 for WBC count, and 0.78 for polymorphonuclear percentage. For ESR, antibiotic-resistant organisms had higher mean values (84.3 mm/hr) than culture-negative cases (57.4 mm/hr), coagulase-negative Staphylococcus (68.3 mm/hr), and Streptococcus species (66.1 mm/hr); Staphylococcus aureus (81.0 mm/hr) was higher than culture-negative cases (57.4 mm/hr). For CRP, culture-negative cases had lower mean values (41.0 mg/L) than gram-negative organisms (87.4 mg/L), antibiotic-resistant organisms (86.0 mg/L), S. aureus (112.2 mg/L), and Streptococcus species (114.6 mg/L); S. aureus (112.2 mg/L) was higher than coagulase-negative Staphylococcus (66.0 mg/L). For WBC count, culture-negative cases had lower mean values (27,984.5 cells/mL) than S. aureus (116,250.0 cells/mL) and Streptococcus species (77,933.7 cells/mL). For polymorphonuclear percentage, there were no significant differences in mean values among all organisms.

CONCLUSIONS

It appears that serological markers, namely ESR and CRP, have a higher false-negative rate than previously reported. Synovial markers similarly exhibit high false-negative rates. Furthermore, the sensitivity of these tests appears to be related to organism type. Surgeons should be aware of the high rate of false-negatives associated with low-virulence organisms and culture-negative cases.

LEVEL OF EVIDENCE

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

Knee replacement surgery significantly elevates the urinary inflammatory biomarkers neopterin and 7,8-dihydroneopterin

CONTEXT

Knee arthroplasty surgery is significant trauma, leading to an activated immune system causing inflammation and oxidative stress. Many current biomarkers are invasive, costly, and often slow to analyse, limiting their use for rapid inflammatory measurements.

OBJECTIVES

We have examined the use of urinary neopterin and total neopterin in knee arthroplasty patients to non-invasively measure oxidative stress and inflammation from immune system activation. We aim to validate the use of these biomarkers for quick, cost effective and predictive measurements of post-surgical inflammation assessment.

METHODOLOGY

19 Knee arthroplasty patients were analysed pre-operatively and for a defined post-operative period to determine the urinary levels of neopterin and total neopterin (neopterin +7,8-dihydroneopterin) using high performance liquid chromatography with fluorescence detection. These results were then compared to a control group of 20 participants with normal knee function.

RESULTS

7,8-Dihydroneopterin was stable in urine over 12 h when refrigerated. Knee arthritis was associated with an increase in pre-operative neopterin (oxidative stress) and total neopterin (inflammation). The subsequent arthroplasty surgery generated a significant increase neopterin and total neopterin. Both biomarkers were reduced immediately post-operatively, before becoming elevated on the following days. There was no clear evidence of an association between initial neopterin and total neopterin levels and a patient's level of inflammation during in-hospital recovery.

CONCLUSIONS

The stability of 7,8-dihydroneopterin in urine allows for its use as an inflammatory marker. Urinary neopterin and total neopterin provided a fast, non-invasive, and simple measure of oxidative stress and inflammation after knee arthroplasty.

Knee replacement

Knee replacement surgery is one of the most commonly done and cost-effective musculoskeletal surgical procedures. The numbers of cases done continue to grow worldwide, with substantial variation in utilisation rates across regions and countries. The main indication for surgery remains painful knee osteoarthritis with reduced function and quality of life. The threshold for intervention is not well defined, and is influenced by many factors including patient and surgeon preference. Most patients have a very good clinical outcome after knee replacement, but multiple studies have reported that 20% or more of patients do not. So despite excellent long-term survivorship, more work is required to enhance this procedure and development is rightly focused on increasing the proportion of patients who have successful pain relief after surgery. Changing implant design has historically been a target for improving outcome, but there is greater recognition that improvements can be achieved by better implantation methods, avoiding complications, and improving perioperative care for patients, such as enhanced recovery programmes. New technologies are likely to advance future knee replacement care further, but their introduction must be regulated and monitored with greater rigour to ensure patient safety.

Tests for predicting reimplantation success of two-stage revision for periprosthetic joint infection: A systematic review and meta-analysis

BACKGROUND

Several tests are used before reimplantation to detect persistent infection in patients with periprosthetic joint infection (PJI) undergoing two-stage revision. However, there is no consensus as to the optimal tests for excluding persistent infection or predicting successful reimplantation by stage. We aimed to determine the accuracy of different tests used to detect persistent infection after the first stage, and/or predicting failure following reimplantation in patients with PJI.

METHODS

We conducted a systematic review and meta-analysis of PubMed, Embase and the Cochrane Library databases. Two reviewers independently conducted quality assessments and data extractions to estimate pooled sensitivity and specificity, diagnostic odds ratio and area under the receiver operating characteristic curves (AUSROC) for each test.

RESULTS

We included 24 studies published between May 1999 and September 2017. Synovial fluid polymorphonuclear neutrophils (PMN)% had the highest sensitivity of 0.70, followed by serum erythrocyte sedimentation rate (0.57) and spacer sonication fluid culture (0.53). Synovial fluid culture had the highest specificity of 0.97, followed by frozen section (0.93) and the Musculoskeletal Infection Society criteria (0.92). Spacer sonication fluid culture was the most accurate test with an AUSROC of 0.8089, followed by synovial fluid culture (0.7749) and frozen section (0.7819).

DISCUSSION

Spacer sonication fluid culture had a relatively high diagnostic accuracy. We emphasize that no test can be used alone to exclude persistent infection beyond the first stage and/or predict failed reimplantation beyond the second stage.

LEVEL OF EVIDENCE

II, systematic review and meta-analysis of level 2 to level 4 studies with inconsistent results.

Two-Stage Exchange Arthroplasty Is a Favorable Treatment Option Upon Diagnosis of a Fungal Periprosthetic Joint Infection

BACKGROUND

This study investigated the prevalence of medical comorbidities, risk factors, and treatment outcomes in patients with fungal periprosthetic joint infection (PJI).

METHODS

All patients with fungal PJI treated from 1999 to 2014 were retrospectively identified at a single institution. Demographic data, comorbidity, and surgical variables were obtained from medical records. Patients were followed up for at least 2 years. PJI was diagnosed using the Musculoskeletal Infection Society criteria. Treatment success was defined using the Delphi consensus criteria. Kaplan-Meier survivorship curves with 95% confidence interval were used for analysis.

RESULTS

Overall, fungal PJIs accounted for 2.4% of the PJI treated at our institution. Twenty-seven patients (93.1%) had 2 or more underlying systemic illnesses. Age and revision surgery were significant risk factors for development of fungal PJI after adjusting for confounding variables. Overall treatment success was 55.2% at 1 year and 40.5% at 5 years. When stratified by initial surgical management, treatment success was 57.1% at 1 year and 28.6% at 5 years following irrigation and debridement; 33.3% at 1 year and 5 years following 1-stage revision; and 57.9% at 1 year and 46.3% at 5 years for 2-stage exchange arthroplasty.

CONCLUSION

Patients with fungal PJI have a high prevalence of systemic illness and poor outcome after surgical management. Irrigation and debridement and single-stage revision demonstrate poor longterm outcomes and may have no place as treatment choices for fungal PJI. Moving forward, our efforts should concentrate on optimizing the systemic status of these patients prior to 2-stage exchange arthroplasty.

Culturing Periprosthetic Joint Infection: Number of Samples, Growth Duration, and Organisms

BACKGROUND

Owing to the difficulty isolating microorganisms in periprosthetic joint infection (PJI), current guidelines recommend that 3-5 intraoperative samples be cultured and maintained for 3-14 days. We investigated (1) the optimal number of culture samples and growth duration to diagnose PJI and (2) the microbiology profile at our institution.

METHODS

A retrospective review of 711 patients (329 hips, 382 knees) with PJI that met Musculoskeletal Infection Society criteria from 2000 to 2014 was performed. Two thousand two hundred ninety aerobic and anaerobic cultures were analyzed. A manual chart review collected demographic, surgical, and microbiological data. Microbiology profiles were trended. Logistic regression analysis was performed to determine statistical significance.

RESULTS

Obtaining 5 samples provided the greatest yield positive cultures for diagnosing PJI. The percentage of positive cultures overall was 62.6% and stratified by organism type: antibiotic resistant (80.0%), Staphylococcus aureus (76.0%), gram negative (58.9%), Pseudomonas (52.0%), variant PJI organisms (28.2%), Propionibacterium acnes (20.0%), and Escherichia coli (8.0%). Although most organisms were cultured in 5 days or less, 10.8 days were needed for Propionibacterium acnes, 6.6 for variant PJI organisms, and 5.2 for coagulase-negative Staphylococcus. At 3 days, only 42.2% of cultures turned positive compared with 95.0% at 8 days. There was a significant decrease in time in gram-positive PJIs and an increase in culture-negative PJIs.

CONCLUSION

The optimal number of cultures and growth duration depended on the type of organism. This study provides evidence that 5 samples should be obtained and held for at least 8 days given that the type of organisms is likely to be unknown at the time of surgery.

Cefazolin Prophylaxis for Total Joint Arthroplasty: Obese Patients Are Frequently Underdosed and at Increased Risk of Periprosthetic Joint Infection

BACKGROUND

One of the most effective prophylactic strategies against periprosthetic joint infection (PJI) is administration of perioperative antibiotics. Many orthopedic surgeons are unaware of the weight-based dosing protocol for cefazolin. This study aimed at elucidating what proportion of patients receiving cefazolin prophylaxis are underdosed and whether this increases the risk of PJI.

METHODS

A retrospective study of 17,393 primary total joint arthroplasties receiving cefazolin as perioperative prophylaxis from 2005 to 2017 was performed. Patients were stratified into 2 groups (underdosed and adequately dosed) based on patient weight and antibiotic dosage. Patients who developed PJI within 1 year following index procedure were identified. A bivariate and multiple logistic regression analyses were performed to control for potential confounders and identify risk factors for PJI.

RESULTS

The majority of patients weighing greater than 120 kg (95.9%, 944/984) were underdosed. Underdosed patients had a higher rate of PJI at 1 year compared with adequately dosed patients (1.51% vs 0.86%, P = .002). Patients weighing greater than 120 kg had higher 1-year PJI rate than patients weighing less than 120 kg (3.25% vs 0.83%, P < .001). Patients who were underdosed (odds ratio, 1.665; P = .006) with greater comorbidities (odds ratio, 1.259; P < .001) were more likely to develop PJI at 1 year.

CONCLUSION

Cefazolin underdosing is common, especially for patients weighing more than 120 kg. Our study reports that underdosed patients were more likely to develop PJI. Orthopedic surgeons should pay attention to the weight-based dosing of antibiotics in the perioperative period to avoid increasing risk of PJI.

Malnutrition and the Development of Periprosthetic Joint Infection in Patients Undergoing Primary Elective Total Joint Arthroplasty

BACKGROUND

Although an abundance of literature exists linking malnutrition with infectious complications in surgical patients, there is little specifically examining the link between malnutrition and periprosthetic joint infection (PJI). This study evaluated the relationship between abnormal nutritional parameters and development of PJI in patients undergoing primary total joint arthroplasty (TJA).

METHODS

We retrospectively reviewed TJA patients from 2000 to 2016 with preoperative nutritional screening at a single institution. Any development of PJI at 2 years was assessed as the primary outcome. The Musculoskeletal Infection society criteria were used to define PJI. The association between the aforementioned nutritional markers and PJI was evaluated in a bivariate analysis followed by multivariate logistic regression. Performance for markers was assessed using receiver operator characteristic curves. Sensitivity and specificity were also compared.

RESULTS

Multivariate analysis demonstrated that low albumin (adjusted odds ratio [OR], 4.69; 95% confidence interval [CI], 2.428-9.085; P < .001) and low hemoglobin (adjusted OR, 2.718; 95% CI, 1.100-2.718; P = .018) were significantly associated with PJI. Albumin had the highest specificity and (95% CI, 97.8%-98.4%) and positive predictive value compared to all other markers. Platelet-to-white blood cell ratio had the highest sensitivity (95% CI, 29.5%-40.3%). The area under the curve was greatest for albumin (0.61; 95% CI, 0.55-0.67) followed by hemoglobin (0.57; 95% CI, 0.51-0.63), platelets (0.56; 95% CI, 0.50-0.62), and platelet-to-white blood cell ratio (0.54; 95% CI, 0.49-0.60).

CONCLUSION

The most valuable predictor of PJI following primary TJA, among nutritional parameters examined, was preoperative albumin with a very high specificity and positive predictive value.

Current Recommendations for the Diagnosis of Acute and Chronic PJI for Hip and Knee-Cell Counts, Alpha-Defensin, Leukocyte Esterase, Next-generation Sequencing

PURPOSE OF REVIEW

Despite significant progress in recent years, the diagnosis of periprosthetic joint infection (PJI) remains a challenge and no gold standard test exists. A combination of serological, synovial, microbiological, histological, and radiological investigations is performed that are expensive, often invasive, and imperfect. Novel biomarkers and molecular methods have shown promise in recent years. The purpose of this review is to provide an update about the diagnostic recommendations for PJI and cover a selection of emerging diagnostic tools.

RECENT FINDINGS

Recent literature highlights a new evidence-based definition for diagnosing hip and knee PJI that shows excellent performance on formal external multi-institutional validation. There is also increasing evidence to support the measurement of selected biomarkers in serum and synovial fluid, such as alpha-defensin, D-dimer, and interleukin-6. Finally, the emerging utility of next-generation sequencing for pathogen identification is discussed. In summary, we describe current recommendations and emerging tests for the diagnosis of PJI. Residual limitations and directions for future research are also discussed.

The Leukocyte Esterase Test Strip Is a Poor Rule-Out Test for Periprosthetic Joint Infection

BACKGROUND

The urinary leukocyte esterase (LE) test strip has been suggested as a good screening test for periprosthetic joint infection (PJI). The purpose of this study is to compare the diagnostic profile of LE assays from different manufacturers and determine whether the LE test strip is a good rule-out test.

METHODS

Synovial fluid samples (N = 344), sent to 1 laboratory for PJI testing, were used in this prospective study. Four different tests for synovial fluid LE were simultaneously evaluated for their performance in detecting white blood cell (WBC) positive samples (>3000 cells/µL).

RESULTS

Both neutrophil elastase immunoassays demonstrated greater sensitivity than urinary LE test strips (92.0% and 90.8% vs 72.4% and 80.3%; all P < 0.011). Fifty-three percent of false-negative urinary LE test strip results clearly missed the presence of elevated levels of synovial fluid LE. Invalid urinary LE test strip results were 4-fold more likely among WBC (+) compared with WBC (-) samples (27.0% vs 6.8%; P < 0.0001). The combined failure to detect an elevated WBC count, because of either false-negative or invalid results, was 47.1% and 41.4% for the Roche and Siemens test strips, respectively.

CONCLUSIONS

This study agrees with the existing literature demonstrating that the LE test strips are among the lowest sensitivity tests for PJI. The urinary LE tests strips should not be used to rule-out PJI, as they often fail to detect abundant levels of LE in synovial fluid. Instead, it is more appropriate to use the (++) LE test strip result as a secondary confirmatory rule-in test for PJI because of its high specificity.

Culture-Negative Periprosthetic Joint Infection: An Update on What to Expect

Background:

Culture-negative periprosthetic joint infection (PJI) is a challenging condition to treat. The most appropriate management of culture-negative PJI is not known, and there is immense variability in the treatment outcome of this condition. The purpose of this study was to elucidate the characteristics, outcomes, and risk factors for failure of treatment of culture-negative PJI.

Methods:

A retrospective review of 219 patients (138 hips and 81 knees) who had undergone surgery for the treatment of culture-negative PJI was performed utilizing a prospectively collected institutional PJI database. PJIs for which the results of culture were unavailable were excluded. An electronic query and manual review of the medical records were completed to obtain patient demographics, treatment, microbiology data, comorbidities, and other surgical characteristics. Treatment failure was assessed using the Delphi consensus criteria.

Results:

The prevalence of suspected culture-negative PJI was 22.0% (219 of 996), and the prevalence of culture-negative PJI as defined by the Musculoskeletal Infection Society (MSIS) was 6.4% (44 of 688). Overall, the rate of treatment success was 69.2% (110 of 159) in patients with >1 year of follow-up. Of the 49 culture-negative PJIs for which treatment failed, 26 (53.1%) subsequently had positive cultures; of those 26, 10 (38.5%) were positive for methicillin-sensitive Staphylococcus aureus. The rate of treatment success was greater (p = 0.019) for patients who had 2-stage exchange than for those who underwent irrigation and debridement.

Conclusions:

The present study demonstrates that culture-negative PJI is a relatively frequent finding with unacceptable rates of treatment failure. Every effort should be made to isolate the infecting organism prior to surgical intervention, including extending the incubation period for cultures, withholding antibiotics prior to obtaining culture specimens, and possibly using newly introduced molecular techniques.

Level of Evidence:

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence

The Radiographic Prepatellar Fat Thickness Ratio Correlates With Infection Risk After Total Knee Arthroplasty

BACKGROUND

Obesity has been associated with complications after a total knee arthroplasty (TKA). Surgical site infection (SSI) after TKA is one of the feared complications as it increases revision rates, costs, and stress to the patient. There is conflicting evidence in the literature regarding body mass index (BMI) and risk of infection after TKA, and some studies have suggested that site-specific fat distribution may be a better metric for determining risk of postoperative infections. Here, we investigate the correlation of soft tissue distribution about the knee to SSI after TKA.

METHODS

We retrospectively review 572 patients who underwent primary TKA at a single institution from 2006 to 2010. We introduce the prepatellar fat thickness ratio (PFTR) as a radiographic means to quantitatively assess fat distribution about the knee and evaluate this measurement's ability to assess the risk of developing an SSI after TKA.

RESULTS

The PFTR was shown to be a better predictor of SSI than BMI in both the univariate (P = .05) and multivariate (P = .01) analyses.

CONCLUSION

Although BMI cannot fully account for variations in adipose distribution, the PFTR may account for this variability and may be a helpful tool for assessing a patient's preoperative risk of SSI after TKA.

The value of quantitative histology in the diagnosis of fracture-related infection

Aims

This study aimed to investigate the role of quantitative histological analysis in the diagnosis of fracture-related infection (FRI).

Patients and Methods

The clinical features, microbiology culture results, and histological analysis in 156 surgically treated nonunions were used to stratify the likelihood of associated infection. There were 64 confirmed infected nonunions (one or more confirmatory criteria: pus, sinus, and bacterial growth in two or more samples), 66 aseptic nonunions (no confirmatory criteria), and 26 possibly infected nonunions (pathogen identified from a single specimen and no confirmatory criteria). The histological inflammatory response was assessed by average neutrophil polymorph (NPs) counts per high-power field (HPF) and compared with the established diagnosis.

Results

Assuming a cut-off of over five neutrophils per high-power field to diagnose septic nonunion, there was 80% sensitivity and 100% specificity (accuracy 90%). Using a cut-off of no neutrophils seen in any high-power field to diagnose aseptic nonunion, there was a sensitivity of 85% and a specificity of 98% (accuracy 92%).

Conclusion

Histology can be used in a bimodal fashion as a diagnostic test for FRI. The presence of more than five NPs/HPF had a positive predictive value for infected nonunion of 100%, while the complete absence of any NPs is almost always indicative of an aseptic nonunion (positive predictive value of 98%). Cite this article: Bone Joint J 2018;100-B:966–72.

Diagnostic parameters in periprosthetic infections: the current state of the literature

Despite progress in recent years, a definitive diagnosis of PPI is not yet possible. Due to new diagnostic possibilities and the further development of already existing diagnostic tools, a more accurate diagnostic clarification of uncertain cases should be possible. The following article includes an overview of common existing diagnostic tools and instruments, which will likely gain importance in the future.

Two-Stage Reimplantation in Infected Total Knee Arthroplasty

Two-stage reimplantation is considered the gold standard for the management of periprosthetic joint infection. The first stage involves the removal of the prosthesis, followed by extensive debridement of all nonviable tissues, synovectomy, irrigation, and reaming of the medullary canals. Once the joint has been prepared, antibiotic-impregnated cement beads and/or spacer are inserted. Antibiotic-impregnated spacers are now more commonly used, and an increasing number of orthopaedic surgeons are using articulating spacers if indicated. Antibiotics are then prescribed to the patient based on the sensitivities of the infecting organism. The duration of systemic antibiotic use is decreasing, and short courses of antibiotic therapy have been shown to be as efficacious as prolonged therapy between the first and second stages. The second stage of the procedure involves removal of the antibiotic-impregnated cement beads and/or spacer, repeat irrigation and debridement, and final reconstruction with revision components. While two-stage reimplantation was considered the gold standard in many parts of the world, recent studies have demonstrated that it is associated with a considerable failure rate. This may be due to the lack of accurate diagnostic tools for infection eradication, and future investigation of risk factors for failure of the two-stage reimplantation should be conducted.

Antibiotic sensitivities of coagulase-negative staphylococci and Staphylococcus aureus in hip and knee periprosthetic joint infections: does this differ if patients meet the International Consensus Meeting Criteria?

Introduction

Coagulase-negative staphylococci (CoNS) are the main pathogens responsible for prosthetic joint infections (PJIs). As normal inhabitants of human skin, it is often difficult to define if they are contaminants, or if they have an active role in initiating infection. This study aims to evaluate differences in CoNS organisms (Staphylococcus hominis, Staphylococcus capitis, Staphylococcus haemolyticus, Staphylococcus warneri) and Staphylococcus aureus in terms of isolation rate and antimicrobial susceptibility from patients who met the International Consensus Meeting (ICM) criteria for PJIs and those who did not.

Methods

Staphylococci isolates from January 2014 to December 2015 retrieved from patients undergoing revision joint arthroplasty were classified in accordance with criteria established by the ICM of Philadelphia.

Results

As per the consensus classification, 50 CoNS and 39 S. aureus infections were recognized as pathogens, while 16 CoNS and four S. aureus were considered as contaminants. Frequency of isolation of S. aureus was significantly higher in infected patients than in those without infection, while no significant differences were observed among CoNS. Resistance to levofloxacin, erythromycin, gentamicin trimethoprim/sulfamethoxazole, and rifampicin was significantly more frequent in S. haemolyticus than in the other species, as well as resistance to erythromycin and gentamicin in S. hominis. In comparison to S. aureus, CoNS were significantly more resistant to daptomycin and gentamicin and more susceptible to rifampicin.

Conclusion

CoNS, other than Staphylococcus epidermidis, are frequently isolated from PJIs, and their infective role and antimicrobial susceptibility need to be assessed on an individual patient basis. S. haemolyticus seems to emerge as responsible for PJI in a large volume of patients, and its role needs to be further investigated, also considering its pattern of resistance.

Cost-benefit analysis of antibiofilm microbiological techniques for peri-prosthetic joint infection diagnosis

BACKGROUND

Implant-related infections, including those of peri-prosthetic joint (PJIs), osteosynthesis and other biomaterials, are biofilm-related. Pathogen identification is considered the diagnostic benchmark; however, the presence of bacterial biofilms makes pathogen detection with traditional microbiological techniques only partially effective. To improve microbiological diagnostic accuracy, some biofilm debonding techniques have been recently proposed. Aim of this health economics assessment study was to evaluate their economic impact on hospital costs.

METHODS

Direct and indirect hospital costs connected with the routine introduction of sonication and dithiothreitol treatment applied to hip and knee PJIs and of tissue cultures were examined. In particular the consequences of diagnostic inaccuracy, the opportunities, costs, and risks of each technique were calculated.

RESULTS

Considering an average of five samples per patient, processed separately with traditional tissue culture with or without sonication of prosthetic components, or pooled together using the MicroDTTect device (a close system for sample collection, transport and treatment with Dithiothreitol for microbial release from biofilm), the overall mean direct cost per patient was € 397 and € 393 for sonication or MicroDTTect, respectively, compared to € 308 for traditional tissue cultures. In terms of opportunity costs, MicroDTTect was the most effective technique, allowing for a 35% or 55% reduction in time required for sample treatment, compared to tissue cultures combined or not with sonication, respectively. Pooling together direct and indirect costs associated with false positive and negative results of the different diagnostic techniques, unnecessary medical treatments and possible medical claims, MicroDTTect or sonication become increasingly cost-effective when the extra-costs, generated by diagnostic inaccuracy of traditional tissue culture, took place, respectively, in 2% or 20% or more of the patients.

CONCLUSIONS

This is the first study specifically focused on the economic impact of the routine clinical use of microbiological antibiofilm sampling and processing techniques in orthopaedics. Although our results may suffer from a potential country and hospital bias, as the data collection process for direct and indirect costs is specific to each institution and country, this analysis highlights the potential economic advantage to hospitals associated with the routine introduction of antibiofilm techniques for microbiological diagnosis of PJI.

Rheumatoid Arthritis, Disease Modifying Agents, and Periprosthetic Joint Infection: What Does a Joint Surgeon Need to Know?

The incidence of periprosthetic joint infection (PJI) among patients with rheumatoid arthritis (RA) is 1.6× greater than in patients undergoing the same procedure for osteoarthritis. This higher risk "may" be due to the immunosuppressive therapies for RA patients including corticosteroids, such as prednisone, and disease-modifying antirheumatic drugs (DMARDs), such as methotrexate. There is a debate about the role of DMARDs in increasing the incidence of subsequent PJI. Studies show conflicting results, with some demonstrating no significant increase in the rates of PJI and some finding otherwise. The International Consensus Meeting on PJI recommended that DMARDs should be halted prior to an elective total joint arthroplasty based on their half-life. Moreover, the International Consensus Meeting stated that cessation of immunosuppressant medications should be performed in consultation with and under the direction of the treating physician. In this review, we aimed to provide an introduction to the available treatment options and cover the recommendations on the treatment protocols for RA patients who undergo elective total joint arthroplasty.

Clinical Outcome of Massive Endoprostheses Used for Managing Periprosthetic Joint Infections of the Hip and Knee

BACKGROUND

Endoprosthetic replacement (EPR) is an option for management of massive bone loss resulting from infection around failed lower limb implants. The aim of this study is to determine the mid-term outcome of EPRs performed in the treatment of periprosthetic joint infection (PJI) and infected failed osteosyntheses around the hip and knee joint and identify factors that influence it.

METHODS

We retrospectively reviewed all hip and knee EPRs performed between 2007 and 2014 for the management of chronic infection following complex arthroplasty or fracture fixation. Data recorded included indication for EPR, number of previous surgeries, comorbidities, and organism identified. Outcome measures included PJI eradication rate, complications, implant survival, mortality, and functional outcome (Oxford Hip or Knee Score).

RESULTS

Sixty-nine EPRs (29 knees and 40 hips) were performed with a mean age of 68 years (43-92). Polymicrobial growth was detected in 36% of cases, followed by coagulase-negative staphylococci (28%) and Staphylococcus aureus (10%). Recurrence of infection occurred in 19 patients (28%): 5 were treated with irrigation and debridement, 5 with revision, 1 with above-knee amputation, and 8 remain on long-term antibiotics. PJI eradication was achieved in 50 patients (72%); the chance of PJI eradication was greater in hips (83%) than in knees (59%) (P = .038). The 5-year implant survivorship was 81% (95% confidence interval 74-88). The mean Oxford Hip Score and Oxford Knee Score were 22 (4-39) and 21 (6-43), respectively.

CONCLUSION

This study supports the use of EPRs for eradication of PJI in complex, multiply revised cases. We describe PJI eradication rate of 72% with acceptable functional outcome.

Multidrug-Resistant Organisms in the Setting of Periprosthetic Joint Infection-Diagnosis, Prevention, and Treatment

BACKGROUND

Periprosthetic joint infection (PJI) is a rare yet challenging problem in total hip and knee arthroplasties. The management of PJI remains difficult primarily due to the evolution of resistance by the infecting organisms.

METHODS

This review profiles acquired mechanisms of bacterial resistance and summarizes established and emerging techniques in PJI diagnosis, prevention, and treatment.

RESULTS

New techniques in PJI diagnosis and prevention continue to be explored. Antibiotics combined with 1 or 2-stage revision are associated with the higher success rates and remain the mainstay of treatment.

CONCLUSION

With higher prevalence of antibiotic-resistant organisms, novel antibiotic implant and wound care materials, improved methods for organism identification, and well-defined organism-specific treatment algorithms are needed to optimize outcomes of PJI.

Total elbow arthroplasty under unfavourable soft tissue conditions

PURPOSE

To evaluate the clinical and radiographic outcomes of patients with total elbow arthroplasty (TEA) and soft tissue reconstruction.

METHODS

We investigated six patients who underwent TEA and soft tissue reconstruction (two elbows with 1-stage surgery and four elbows with 2-stage surgery). The mean patient age at the time of the surgical procedure was 43.2 years; the mean follow-up duration was 88.2 months.

RESULTS

The mean pain visual analogue scale (VAS) during motion was improved from 6.3 pre-operatively to 0.7 at the last follow-up. The mean Mayo Elbow Performance Score (MEPS) improved from 26.7 pre-operatively to 81.7 at the last follow-up. The mean flexion-extension arcs of the 1- and 2-stage surgery groups increased from 12.5° and 13.8° pre-operatively to 72.5° and 100° at the last follow-up, respectively. The mean MEPS of the one and two stage surgery groups were 75 and 85, respectively, at the last follow-up. One of the six elbows had loosening on the simple radiograph at the last follow-up, and there were no cases with bushing wear. Three elbows needed additional skin debridement owing to wound complications (2/2 elbows in the 1-stage surgery group and 1/4 elbows in the 2-stage surgery group).

CONCLUSIONS

Under unfavorable soft tissue conditions, performing soft tissue reconstruction with TEA provides satisfactory functional improvement and pain relief. The two stage surgery provided a lower rate of wound complication and better elbow function than the one stage surgery, which led to high patient satisfaction post-operatively.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Screening for Infection Before Revision Hip Arthroplasty: A Meta-analysis of Likelihood Ratios of Erythrocyte Sedimentation Rate and Serum C-reactive Protein Levels

INTRODUCTION

Diagnosing periprosthetic joint infection (PJI) before revision hip arthroplasty is critical to ensure effective treatment of patients undergoing surgery for reasons other than infection. The main objective of our study is to determine whether the erythrocyte sedimentation rate (ESR) and the serum C-reactive protein (CRP) level are sufficient to use for testing to rule out infection in patients undergoing revision hip surgery.

METHODS

We performed a systematic review of the literature in the MEDLINE, Ovid, and Embase databases. We included studies in which the investigators used the ESR (>30 mm/h) and serum CRP level (>10 mg/L) for the diagnosis of PJI of the hip. We obtained meta-estimates of sensitivity, specificity, positive likelihood ratio (LR+), and negative likelihood ratio (LR-).

RESULTS

From 511 articles, we analyzed 12 studies in which the investigators reported data on 2,736 patients. Sensitivity and specificity for the ESR were 0.860 (95% confidence interval [CI], 0.825 to 0.890) and 0.723 (95% CI, 0.704 to 0.742), respectively, and for the CRP level were 0.869 (95% CI, 0.835 to 0.899) and 0.786 (95% CI, 0.769 to 0.803), respectively. For the ESR, LR+ was 3.42 (95% CI, 2.55 to 4.59) and LR- was 0.22 (95% CI, 0.12 to 0.41). For the CRP level, LR+ was 4.18 (95% CI, 3.42 to 5.11) and LR- was 0.20 (95% CI, 0.12 to 0.32).

DISCUSSION

With a low pretest probability of PJI, a negative test result for either the ESR or CRP level is enough to rule out infection before revision hip arthroplasty.

LEVEL OF EVIDENCE

III.

Midterm Survivorship and Complications of Total Knee Arthroplasty in Patients With Dwarfism

BACKGROUND

Dwarfism is associated with skeletal dysplasias and joint deformities that frequently result in osteoarthritis requiring treatment with total knee arthroplasty (TKA). These surgeries can be challenging because of alignment deformities, poor bone stock, and smaller components. This study aims to compare TKA implant survivorship and complications between dwarf and nondwarf patients.

METHODS

A retrospective case-control study was performed from 1997-2014 evaluating 115 TKAs in patients under the height threshold of 147.32 cm. This cohort was compared with 164 patients of normal height. Medical records were reviewed for demographics, surgical characteristics, and outcomes. All cases had 2-year minimum follow-up.

RESULTS

The revision rate was 8.7% in dwarfs compared with 3.7% in controls (P = .08). The 2-, 5-, and 10-year implant survivorship in dwarfs was 96.4%, 92.5%, and 90.2%, respectively; and 96.6%, 95.6%, and 94.8% for controls, respectively (P = .24). Dwarfs underwent significantly more manipulations for arthrofibrosis (P = .002). There was greater femoral (17.4% vs 2.1%, P < .01) and tibial (6.5% vs 2.7%, P < .01) component overhang in dwarfs compared with controls.

CONCLUSION

Despite a 2-fold increase in the revision rate of the dwarf cohort, the midterm survivorship is comparable between the dwarf and nondwarf patients. However, dwarfs were more likely to become stiff and undergo manipulation; the increased propensity for stiffness may be associated with oversized components, as evidenced by greater component overhang. Surgeons should be aware of this increased risk and may consider using smaller or customized implants to account for the morphological differences in this patient population.

Single-Dose, Preoperative Vitamin-D Supplementation Decreases Infection in a Mouse Model of Periprosthetic Joint Infection

BACKGROUND

Despite recent advances, infection remains the most common etiology of arthroplasty failure. Recent work suggests that 25-hydroxyvitamin D (25D) deficiency correlates with the frequency of periprosthetic joint infection (PJI). We endeavored to examine whether 25D3 deficiency leads to increased bacterial burden in vivo in an established mouse model of PJI and, if so, whether this effect can be reversed by preoperative 25D3 supplementation.

METHODS

Mice (lys-EGFP) possessing fluorescent neutrophils were fed a vitamin D3-sufficient (n = 20) or deficient (n = 40) diet for 6 weeks. A group of 25D3-deficient mice (n = 20) were "rescued" with 1 intraperitoneal dose of 25D3 at 3 days before surgery. A stainless steel implant was inserted into the knee joint and the joint space was inoculated with bioluminescent Staphylococcus aureus (1 × 10 colony forming units [CFUs]). In vivo imaging was used to monitor bacterial burden and neutrophil infiltration. Blood was drawn to confirm 25D3 levels 3 days before surgery and on postoperative days (PODs) 0 and 14. Mice were killed at POD 21, and CFUs were quantified after culture. Myeloperoxidase (MPO) and β-N-acetylglucosaminidase (NAG) were assayed to look at neutrophil infiltration and activated tissue macrophage recruitment, respectively.

RESULTS

Serum values confirmed 25D3 deficiency and repletion of the 25D3-rescued group. Bacterial bioluminescence and neutrophil fluorescence were significantly greater (p < 0.05) in the 25D3-deficient group. CFU counts from the joint tissue and implant were also significantly greater in this group (p < 0.05). Rescue treatment significantly decreased bacterial burden and neutrophil infiltration (p < 0.05). Compared with the 25D3-sufficient and 25D3-rescued groups, MPO activity was higher (p < 0.02) and NAG activity was lower (p < 0.03) in the 25D3-deficient group.

CONCLUSIONS

This study demonstrated in vivo in a mouse model of PJI that (1) 25D3 deficiency results in increased bacterial burden and neutrophil infiltration, and (2) this effect can be reversed with preoperative repletion of 25D3.

CLINICAL RELEVANCE

Considering that >65% of patients undergoing arthroplasty have insufficient or low levels of total 25D and that 25D levels can be replenished with ease using a U.S. Food and Drug Administration (FDA)-approved, oral 25D3 product, 25D deficiency may be an important modifiable risk factor in humans undergoing joint replacement.

The Role of Biomarkers for the Diagnosis of Implant-Related Infections in Orthopaedics and Trauma

Diagnosis of implant-related (periprosthetic joint) infections poses a major challenge to infection disease physicians and orthopaedic surgeons. Conventional diagnostic tests continue to suffer from issues of accuracy and feasibility. Biomarkers are used throughout medicine for diagnostic and prognostic purposes, as they are able to objectively determine the presence of a disease or a biological state. There is increasing evidence to support the measurement of specific biomarkers in serum and/or synovial fluid of patients with suspected periprosthetic joint infections. Promising serum biomarkers include interleukin (IL)-4, IL-6, tumour necrosis factor (TNF)-α, procalcitonin, soluble intercellular adhesion molecule 1 (sICAM-1), and D-dimer. In addition to c-reactive protein and leucocyte esterase, promising biomarkers that can be measured in synovial fluid include antimicrobial proteins such as human β-defensin (HBD)-2 and human β-defensin (HBD)-3, and cathelicidin LL-37, as well as several interleukins such as IL-1β, IL-6, IL-8, IL-17, TNF- α, interferon-δ, and vascular endothelial growth factor.

Interpretation of Leukocyte Esterase for the Detection of Periprosthetic Joint Infection Based on Serologic Markers

BACKGROUND

Leukocyte esterase (LE) is a rapid, point-of-care test for periprosthetic joint infection. The purpose of this study was to provide a tool for interpreting LE based on an initial serologic screening.

METHODS

We reviewed the records of 319 patients who had erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) screening before hip or knee aspiration; 102 had elevated ESR and CRP levels, 64 had an elevated ESR or CRP level, and 153 had normal serology. The likelihood of infection was calculated based on the results of LE testing.

RESULTS

When LE results were concordant with ESR and CRP levels, LE served to effectively diagnose or rule out a diagnosis of periprosthetic joint infection with >95% certainty. When LE was discordant from serology, only the stricter LE thresholds (2+ or negative) were adequately diagnostic to potentially suggest a change in clinical decision-making.

CONCLUSION

With discordant results, the lesser thresholds (1+ or trace) should serve to incite further diagnostic inquiry.

Epidemiology and Antibiotic Resistance of Late Prosthetic Knee and Hip Infections

BACKGROUND

Prosthetic joint infections (PJI) are still a major complication of hip and knee arthroplasties. Identification of the causative pathogens and knowledge of their antibiotic susceptibilities are essential for the management of these infections. The main purpose of the study was to identify and compare the causative bacteria of prosthetic knee and hip joint infections in a reference Italian orthopedic center and to characterize antibiotic resistance profiles of bacteria involved.

METHODS

Data from 429 patients with diagnosis of PJI were collected from January 2013 to June 2015: 229 presented a hip and 200 a knee prosthesis infection. Prostheses and periprosthetic tissues were treated with dithiothreitol before plating onto different media and broths. Identification and antimicrobial susceptibility testing were carried out by VITEK2 Compact (bioMerieux).

RESULTS

There was not a substantial difference in the etiology of hip and knee PJI: staphylococci were the most frequently isolated bacteria in both groups, followed by Enterobacteriaceae and Propionibacterium acnes. Staphylococci showed a high rate of methicillin resistance (144 of 341) and a worrying frequency of isolates were resistant to teicoplanin (9%). Only 8.3% of Enterobacteriaceae produced extended-spectrum beta-lactamases, whereas the rate of carbapenemase-producing bacteria was not significant.

CONCLUSION

We observed similar etiology of hip and knee PJIs. Nevertheless, bacteria isolated from knee showed higher resistance rates to glycopeptides and fluoroquinolones when compared with those isolated from the hip. The reason for this difference remains to be elucidated in future studies.

Superiority of the sonication method against conventional periprosthetic tissue cultures for diagnosis of prosthetic joint infections

INTRODUCTION

Diagnosis of periprosthetic infections is challenging. The aim of this study was to compare the diagnostic accuracy of conventional periprosthetic tissue culture and culture of sonication fluid of the explanted prostheses.

METHODS

We prospectively enrolled 114 patients undergoing revision hip or knee arthroplasty because of loosening of the prostheses, at our institution, between July 2012 and July 2016. Patients' medical history and demographic characteristics were recorded. The explanted hardware was separated in sterile containers and sonicated under sterile conditions. At least five samples of periprosthetic tissue were sent for culture and histological examination. We compared the culture of samples obtained by sonication of explanted hip and knee prostheses with conventional culture of periprosthetic tissue for the microbiological diagnosis of prosthetic joint infection.

RESULTS

Infectious Diseases Society of America guidelines were used for the definition of prosthetic joint infection. Sixty-one patients had periprosthetic infection and 53 aseptic loosening (73 hip prostheses and 41 knee prostheses). The sensitivity of sonication fluid culture was 77.04%, and the sensitivity of conventional tissue cultures was 55.73% (p value = 0.012). The specificities of the two methods were 98.11 and 94.34%, respectively. The sensitivity of the histopathological examination of the periprosthetic tissue was 72.10%. There were 17 patients with PJI where the isolated pathogen was detected in SFC but not in PTC, while in five cases the pathogen was detected only in PTC. There were nine patients where no bacteria were detected by any microbiological method and the diagnosis was based on clinical and histological findings, according to the guidelines.

CONCLUSIONS

The sonication method represents a reliable test for the diagnosis of prosthetic joint infections with a greater sensitivity and specificity than the conventional periprosthetic tissue cultures.

α-Defensin point-of-care test for diagnosis of prosthetic joint infections: neglected role of laboratory and clinical pathologists

Periprosthetic joint infection (PJI) is a serious complication that may occur after native joint replacement leading to a severe health and economic burden. Currently, due to several confounding factors, PJI is difficult to diagnose. Today, a multidisciplinary approach is indispensable to correctly define a periprosthetic joint infection; indeed, tissue histology, microbiology cultures and clinical findings are used together to achieve this goal. Analysis of α-defensin is commonly used for PJI diagnosis, as it allows the rapid detection of α-defensin present in the synovial fluid following a microbial infection. Currently, a point-of-care testing (POCT) assay able to detect the presence of human α-defensins 1–3 in synovial fluid of patients is aimed directly at orthopedic surgeons. However, many orthopedic surgeons lack experience and training in quality laboratory practices, often failing to appreciate the significance of quality control and proper documentation when using POCT assays. To guarantee the highest quality diagnostic services, the α-defensin test should be used together with other biochemical and microbiological criteria commonly used for PJI diagnosis. Additionally, the close cooperation and communication between laboratory, pathologists and physicians is of fundamental importance in the correct diagnosis of PJI.

Outcome Following Debridement, Antibiotics, and Implant Retention in Hip Periprosthetic Joint Infection-An 18-Year Experience

BACKGROUND

Debridement-antibiotics-and-implant-retention (DAIR) may be considered a suitable surgical option in periprosthetic joint infections (PJIs) with soundly fixed prostheses, despite chronicity. This study aims to define the long-term outcome following DAIR in hip PJI.

METHODS

We reviewed all hip DAIRs performed between 1997 and 2013 (n = 122) to define long-term outcome and identify factors influencing it. Data recorded included patient demographics, medical history, type of DAIR performed (+/- exchange of modular components), and organisms identified. Outcome measures included complications and/or mortality rate, implant survivorship, and functional outcome (Oxford Hip Score).

RESULTS

Most DAIRs (67%) were of primary arthroplasties and 60% were performed within 6 weeks from the index arthroplasty. Infection eradication was achieved in 68% of the first DAIR procedure. In 32 cases, more than one DAIR was required. Infection eradication was achieved in 85% of the cases (104/122) with the (single or multiple) DAIR approach. The most common complication was PJI-persistence (15%), followed by dislocation (14%). Very good functional outcomes were obtained, especially in primary arthroplasties. All streptococcus infections were resolved with DAIR and had better outcome. Twenty-one hips have been revised (17%) to-date, 16 were for persistence of PJI. The 10-y implant survivorship was 77%. Early PJI and exchanging modular components at DAIR were independent factors for a 4-fold increased infection eradication and improved long-term implant survival.

CONCLUSION

DAIR is, therefore, a valuable option in the treatment of hip PJI, especially in the early postoperative period (≤6 weeks), with good outcomes. However, DAIR is associated with increased morbidity; further surgery may be necessary and instability may occur. Where possible, exchange of modular implants should be undertaken.

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.

METHODS

This single-institution study prospectively recruited and retrospectively analyzed 109 patients who underwent two-stage exchange treatment of PJI, from 2009-2016, and had an LE test performed at time of reimplantation. LE results of "2+" were considered positive. Ninety-five patients had 90-day minimum follow-up to assess treatment failure, defined by Delphi criteria. Eighteen patients were excluded due to blood contamination of LE test, resulting in a final cohort of 77 patients (mean follow-up 1.76 years).

RESULTS

Of the final cohort, 19 patients (24.7%) experienced subsequent failure. At reimplantation, LE test was positive in 22.2% of culture-positive and 4.4% of culture-negative cases. The LE test was negative in all patients who had not failed at latest follow-up, yielding sensitivity, specificity, positive predictive value, negative predictive value, and AUC of 26.3%, 100%, 100%, 87.5%, and 0.632, respectively; in comparison, MSIS criteria respectively yielded 25.0%, 87.3%, 27.6%, 85.8%, and 0.562 (P = .01 for specificity). Kaplan-Meier curves revealed higher failure rate in patients who had a positive LE test at time of reimplantation (P < .001).

CONCLUSION

There is a dire need for an accurate diagnostic test to determine optimal timing of reimplantation in patients undergoing surgical treatment for PJI. The current study suggests that a positive LE test may be indicative of persistence of infection and results in a higher rate of subsequent failure.

What is the Accuracy of Nuclear Imaging in the Assessment of Periprosthetic Knee Infection? A Meta-analysis

BACKGROUND

In the assessment of possible periprosthetic knee infection, various imaging modalities are used without consensus regarding the most accurate technique.

QUESTIONS/PURPOSES

To perform a meta-analysis to compare the accuracy of various applied imaging modalities in the assessment of periprosthetic knee infection.

METHODS

A systematic review and meta-analysis was conducted with a comprehensive search of MEDLINE and Embase^® in accordance with the PRISMA and Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) recommendations to identify clinical studies in which periprosthetic knee infection was investigated with different imaging modalities. The sensitivity and specificity of each imaging technique were determined and compared with the results of microbiologic and histologic analyses, intraoperative findings, and clinical followup of more than 6 months. A total of 23 studies, published between 1990 and 2015, were included for meta-analysis, representing 1027 diagnostic images of symptomatic knee prostheses. Quality of the included studies showed low concerns regarding external validity, whereas internal validity indicated more concerns regarding the risk of bias. The most important concerns were found in the lack of uniform criteria for the diagnosis of a periprosthetic infection and the flow and timing of the included studies. Differences among techniques were tested at a probability less than 0.05 level. Where there was slight overlap of confidence intervals for two means, it is possible for the point estimates to be statistically different from one another at a probability less than 0.05. The z-test was used to statistically analyze differences in these situations.

RESULTS

Bone scintigraphy was less specific than all other modalities tested (56%; 95% CI, 0.47-0.64; p < 0.001), and leukocyte scintigraphy (77%; 95% CI, 0.69-0.85) was less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p < 0.001) or combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Fluorodeoxyglucose positron emission tomography (FDG-PET) (84%; 95% CI, 0.76-0.90) was more specific than bone scintigraphy (56%; 95% CI, 0.47-0.64; p < 0.001), and less specific than antigranulocyte scintigraphy (95%; 95% CI, 0.88-0.98; p = 0.02) and combined leukocyte and bone marrow scintigraphy (93%; 95% CI, 0.86-0.97; p < 0.001). Leukocyte scintigraphy (88%; 95% CI, 0.81-0.93; p = 0.01) and antigranulocyte scintigraphy (90%; 95% CI, 0.78-0.96; p = 0.02) were more sensitive than FGD-PET (70%; 95% CI, 0.56-0.81). However, because of broad overlapping of confidence intervals, no differences in sensitivity were observed among the other modalities, including combined bone scintigraphy (93%; 95% CI, 0.85-0.98) or combined leukocyte and bone marrow scintigraphy (80%; 95% CI, 0.66-0.91; p > 0.05 for all paired comparisons).

CONCLUSIONS

Based on current evidence, antigranulocyte scintigraphy and combined leukocyte and bone marrow scintigraphy appear to be highly specific imaging modalities in confirming periprosthetic knee infection. Bone scintigraphy was a highly sensitive imaging technique but lacks the specificity needed to differentiate among various conditions that cause painful knee prostheses. FDG-PET may not be the preferred imaging modality because it is more expensive and not more effective in confirming periprosthetic knee infection.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Is There Still a Role for Irrigation and Debridement With Liner Exchange in Acute Periprosthetic Total Knee Infection?

BACKGROUND

Periprosthetic joint infection (PJI) is an important cause of failure in total knee arthroplasty. Irrigation and debridement including liner exchange (I&D/L) success rates have varied for acute PJI. The purpose of this study is to present results of a specific protocol for I&D/L with retention of total knee arthroplasty components.

METHODS

Sixty-seven consecutive I&D/L patients were retrospectively evaluated. Inclusion criteria for I&D/L were as follows: fewer than 3 weeks of symptoms, no immunologic compromise, intact soft tissue sleeve, and well-fixed components. I&D/L consisted of extensive synovectomy; irrigation with 3 L each of betadine, Dakin's, bacitracin, and normal saline solutions; and exchange of the polyethylene component. Postoperatively, all patients were treated with intravenous antibiotics. Infection was considered eradicated if the wound healed without persistent drainage, there was no residual pain or evidence of infection.

RESULTS

Forty-six patients (68.66%) had successful infection eradication regardless of bacterial strain. Those with methicillin-resistant Staphylococcus aureus (MRSA) had an 80% failure rate and those with Pseudomonas aeruginosa had a 66.67% failure rate. The success rate for bacteria other than MRSA and Pseudomonas was 85.25%.

CONCLUSION

Our protocol for I&D/L was successful in the majority of patients who met strict criteria. We recommend that PJI patients with MRSA or P aeruginosa not undergo I&D/L and be treated with 2-stage revision. For nearly all other patients, our protocol avoids the cost and patient morbidity of a 2-stage revision.

Radiologic Approach to Musculoskeletal Infections

Imaging is often used to establish a diagnosis of musculoskeletal infections and evaluate the full extent and severity of disease. Imaging should always start with radiographs, which provide an important anatomic overview. MRI is the test of choice in most musculoskeletal infections because of its superior soft tissue contrast resolution and high sensitivity for pathologic edema. However, MRI is not always possible. Alternative imaging modalities including ultrasound scan, computed tomography, and radionuclide imaging may be used. This article reviews the individual imaging modalities and discusses how specific musculoskeletal infections should be approached from an imaging perspective.

Osteomyelitis: Recent advances in pathophysiology and therapeutic strategies

This review article summarizes the recent advances in pathogenic mechanisms and novel therapeutic strategies for osteomyelitis, covering both periprosthetic joint infections and fracture-associated bone infections. A better understanding of the pathophysiology including the mechanisms for biofilm formation has led to new therapeutic strategies for this devastating disease. Research on novel local delivery materials with appropriate mechanical properties, lower exothermicity, controlled release of antibiotics, and absorbable scaffolding for bone regeneration is progressing rapidly. Emerging strategies for prevention, early diagnosis of low-grade infections, and innovative treatments of osteomyelitis such as biofilm disruptors and immunotherapy are highlighted in this review.

[Incidence of hip and knee prosthetic infections in a specialized center of Mexico City]

BACKGROUND

Hip and knee prosthetic replacements have proven to be the most appropriate treatment in the joints that do not benefit from medical or arthroscopic interventions; however, infections are the most feared complication. It is recommended that the incidence of infection should not exceed 2%.

MATERIAL AND METHODS

This was an observational, prospective, longitudinal and observational study conducted in patients fitted with a prosthetic joint from August 2011 to July 2012. Patients were followed up pre and post-surgery for one year to identify a prosthetic infection, diagnosed using international parameters. We calculated the incidence of prosthetic infection, as well as the incidence density.

RESULTS

A total of 339 patients (179 hip and 160 knee) were included. Variations in the time of pre-operative antibiotics' administration were observed. Six prosthetic infections were identified with an incidence rate of 1.79/339 arthroplasties, 2.2/179 hip procedures, and 1.25/160 knee arthroplasties. An incidence density of 0.02/year for hip arthroplasties and 0.11/year for knee procedures was identified. There were 4 infections of hip and 2 of knee. Five infections were acute and one chronic. The isolated microorganisms were E. faecalis, S. epidermidis (2), S. mitis, S. aureus and P. stomatis.

CONCLUSIONS

The incidence of prosthetic joint infection in the first year of follow-up at our centre is within the recommended parameters. Surgical techniques and organizational practices influence the results.

Polymicrobial Periprosthetic Joint Infections: Outcome of Treatment and Identification of Risk Factors

BACKGROUND

The treatment outcomes of periprosthetic joint infection are frequently dependent on characteristics of the causative organism. The objective of this comparative study was to investigate the prevalence of and risk factors for development of polymicrobial periprosthetic joint infection, and the outcome of surgical treatment of these patients.

METHODS

All patients with polymicrobial, monomicrobial, or culture-negative periprosthetic joint infection treated from 2000 to 2014 were identified at a single institution. Ninety-five patients with a polymicrobial periprosthetic joint infection had a minimum follow-up of 12 months. We matched patients with a polymicrobial periprosthetic joint infection with the other cohorts using propensity score matching for several important parameters. Treatment success was defined according to the Delphi criteria; Kaplan-Meier survivorship curves were generated to demonstrate this. A multiple logistic regression analysis was performed to determine risk factors for a polymicrobial periprosthetic joint infection.

RESULTS

Overall, 10.3% (108 of 1,045) of the periprosthetic joint infections treated at our institution were polymicrobial in nature. Patients with a polymicrobial periprosthetic joint infection had a higher failure rate at 50.5% (48 of 95) compared with the monomicrobial periprosthetic joint infection cohort at 31.5% (63 of 200) and the culture-negative periprosthetic joint infection cohort at 30.2% (48 of 159) (p = 0.003). The survivorship of the polymicrobial periprosthetic joint infection group was 52.2% at the 2-year follow-up, 49.3% at the 5-year follow-up, and 46.8% at the 10-year follow-up. Patients with polymicrobial periprosthetic joint infection had a higher rate of amputation (odds ratio [OR], 3.80 [95% confidence interval (CI), 1.34 to 10.80]), arthrodesis (OR, 11.06 [95% CI, 1.27 to 96.00]), and periprosthetic joint infection-related mortality (OR, 7.88 [95% CI, 1.60 to 38.67]) compared with patients with monomicrobial periprosthetic joint infection. Isolation of gram-negative organisms (p < 0.01), enterococci (p < 0.01), Escherichia coli (p < 0.01), and atypical organisms (p < 0.01) was associated with polymicrobial periprosthetic joint infection. Only the presence of a sinus tract (OR, 2.20 [95% CI, 1.39 to 3.47]; p = 0.001) was a significant risk factor for polymicrobial periprosthetic joint infection on multivariate analysis.

CONCLUSIONS

This study reveals that polymicrobial periprosthetic joint infection, occurring at a relatively low rate, is associated with poor outcomes when compared with monomicrobial and culture-negative periprosthetic joint infection. Patients with polymicrobial infections were more likely to require a salvage procedure or to have periprosthetic joint infection-related mortality. Polymicrobial periprosthetic joint infection was associated with soft-tissue defects such as a sinus tract and certain types of organisms, which should be considered when administering antibiotics to these patients.

LEVEL OF EVIDENCE

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