Prosthetic joint infection

A Review of Novel Antibiotic Regimens for the Treatment of Orthopedic Infections

As a result of the increasing numbers of joint replacement surgeries and other implant-associated procedures performed, the incidences of periprosthetic joint infections and osteomyelitis are on the rise. Antibiotic resistance to gram-positive species, which are mostly isolated from such infections, is a significant obstacle in clinical practice. Promising clinical outcomes have been reported with the use of novel antibiotics for patients with periprosthetic joint infections and osteomyelitis. Further research is necessary for the establishment of these novel antibiotic therapies in routine clinical practice. [Orthopedics. 2018; 41(6):323-328.].

Totally Implantable Venous-Access Device Infection Causing Hematogenous Prosthetic Joint Infection: A Retrospective Case Series

Introduction: Prosthetic joint infections (PJIs) can be acquired hematogenously from a distant site or device. Notably, 30%-40% of patients with PJIs have Staphylococcus aureus bacteremia. No case reports or series of PJIs acquired from totally implantable venous-access device (TIVAD) infection or colonization have been published. This study was undertaken to describe epidemiological, clinical, microbiological and radiological characteristics of such PJIs, their treatments and outcomes. Methods: This retrospective study included all patients, identified in a prospective French Bone-and-Joint Infections Referral Center cohort treated between 2004 and 2017, with PJI secondary to TIVAD infection, with the same microbiologically documented microorganism isolated from both. Results: We describe six consecutive hematogenous PJIs (4 women, 2 men; median age: 66.5 years) acquired from TIVAD primary infections. The main infection risk factors were malignancy (n=5) and prior septic arthritis (n=2). Four participants' TIVADs were implanted for chemotherapy, preceding the prosthesis for one patient. The median TIVAD-implantation-to-symptom-onset interval was 12 months. Microorganisms were Staphylococcus epidermidis (n=4), Staphylococcus capitis (n=1) and Staphylococcus aureus (n=1). All TIVADs were removed. Five participants received curative treatment, with a median of 12 weeks of antibiotics. After median follow-up of 42 months, none have relapsed. Conclusions: When PJI occurs in a patient with a TIVAD, the latter must be tested as a potential source of the prosthesis infection. Conversely, PJIs must sought in all patients with bacteremia.

Origin and characteristics of haematogenous periprosthetic joint infection

OBJECTIVES

Recognition of infectious origin of haematogenous periprosthetic joint infections (PJI) is crucial. We investigated the primary focus and characteristics of haematogenous PJI.

METHODS

Consecutive patients who presented with haematogenous PJI between 01/2010 and 01/2018 were retrospectively analysed. Haematogenous PJI was defined by diagnosis of infection ≥1 month after surgery, acute manifestation after a pain-free period and positive blood or prosthetic-site culture and/or evidence of distant infectious focus consistent with the pathogen. Fisher's exact, Student's t and Mann-Whitney U tests were used, as appropriate.

RESULTS

A total of 106 episodes of PJI were included, involving 59 knee, 45 hip, one shoulder and one elbow prostheses. The median time from last surgery until haematogenous PJI was 47 months (range, 1-417 months). The pathogen was identified in 105 episodes (99%), including Staphylococcus aureus (n = 43), streptococci (n = 32), enterococci (n = 13), Gram-negative bacteria (n = 9) and coagulase-negative staphylococci (n = 8). Gram-negative bacteria were significantly more often found in hip joints than in knee joints. Blood cultures grew the pathogen in 43 of 70 episodes (61%). The primary infectious focus was identified in 72 episodes (68%) and included infections of intravascular devices or heart valves (22 episodes), skin and soft tissue (16 episodes), the oral cavity (12 episodes), urogenital (12 episodes) or gastrointestinal tract (seven episodes) and other sites (three episodes).

CONCLUSIONS

In acute PJI manifesting after a pain-free period, the haematogenous infection route should be considered and the primary infectious focus should be actively searched for. The cardiovascular system, skin and soft tissue, oral cavity, urogenital and gastrointestinal tracts were common origins of haematogenous PJI.

Clostridium difficile infection in the USA: incidence and associated factors in revision total knee arthroplasty patients

INTRODUCTION

Revision total knee arthroplasty (TKA) procedures performed secondary to periprosthetic joint infection (PJI) are associated with significant morbidity and mortality. These poor outcomes may be further complicated by postoperative infection requiring antibiotics. However, antibiotic overuse may suppress patients' bacterial flora, leading to Clostridium difficile infection (CDI). Therefore, we aimed to study the: (1) incidence; (2) costs; and (3) risk factors associated with CDI in revision TKA patients.

METHODS

The National Inpatient Sample database was queried for individuals diagnosed with PJI who underwent revision TKA between 2009 and 2013 (n = 83,806). Patients who developed CDI during their inpatient stay were identified (n = 799). Logistic regression analysis was conducted to assess the association between hospital- and patient-specific characteristics and the development of CDI.

RESULTS

The incidence of CDI after revision TKA was 1.0%. These patients were older (mean age 69.05 vs. 65.52 years), had greater LOS (median 11 vs. 5 days) and greater costs ($30,612.93 vs. 18,873.75), and experienced higher in-hospital mortality (3.6 vs. 0.5%; p < 0.001 for all) compared to those without infection. Patients with CDI were more likely to be treated in urban, not-for-profit, medium/large hospitals in the Northeast or Midwest (p < 0.05 for all) and to have underlying depression (OR 4.267; p = 0.007) or fluid/electrolyte disorders (OR 3.48; p = 0.001).

CONCLUSION

Although CDI is rare following revision TKA, it can have detrimental consequences. We demonstrate that CDI is associated with longer LOS, higher costs, and greater in-hospital mortality. With increased legislative pressure to lower healthcare expenditures, it is crucial to identify means of preventing costly complications.

Antibiotic Elution Characteristics and Pharmacokinetics of Gentamicin and Vancomycin from a Mineral Antibiotic Carrier: An in vivo Evaluation of 32 Clinical Cases

Introduction: Locally implanted antibiotic-eluting carriers may be a valuable adjuvant to the management of prosthetic joint infections. Aim: to assess local and plasma antibiotic concentrations as well as cumulative antibiotic urine excretion associated with clinical use of a gentamicin - or vancomycin-loaded mineral composite antibiotic carrier. Methods: 32 patients (male/female=19/13, mean age=56; 21-82 years) were prospectively followed after implantation of gentamicin (n=11), vancomycin (n=15), or a combination (n=7), using an antibiotic carrier (CERAMENT™|G or CERAMENT™|V, mean amount 11 (3-20) mL) during resection arthroplasty of the hip/knee. We measured antibiotic concentrations in plasma (1h, 3h, 24h, 48h and 72h post-implantation), urine (24h, 48h and 72h post-implantation) and in drain (n=15). Results: We observed low antibiotic concentrations in plasma (Gentamicin: 0.33 mg/L (95%-CI: 0.25-0.44) and vancomycin: 1.33 mg/L (95%-CI: 1.02-1.66)) and high concentrations in drain (Gentamicin: mean 57.8 mg/L (95%-CI: 45.8-69.7) and vancomycin: mean 234.4 mg/L (95%-CI: 198.9-269.7)). Use of a drain was associated with a statistically significant reduction in vancomycin urine excretion (55.6% (95% CI: 36.45-74.92) to 28.71% (95% CI: 13.07-44.35), p=0.042). A similar trend was observed for gentamicin (34.17% (95% CI: 24.62-43.72) to 16.22% (95% CI: 0-33.86), p=0.078). Conclusions: CERAMENT™G/V was associated with safe plasma concentrations and high local concentrations above minimum inhibitory concentration. Installation of a surgical drain results in removal of a substantial amount of antibiotics and reduces antibiotic urine excretion.

Single versus Double Skin Preparation for Infection Prevention in Proximal Humeral Fracture Surgery

Preoperative skin preparation plays a major role in preventing postoperative infections. This study aims to compare a single skin preparation (povidone iodine) with a double skin preparation (chlorhexidine gluconate followed by povidone iodine). Forty patients affected by proximal humeral fracture were included in the study. The day of surgery the two skin preparation strategies were performed in the same shoulder, divided into two areas, at the level of the deltopectoral approach. Skin swabs were collected from each area and subjected to microbiological analysis. Both skin preparations significantly reduced the positive culture rate. Coagulase-negative staphylococci (CoNS) dropped from 92.5% to 40% and to 7.5% after the single and double skin preparation (p<0.001), respectively. The positivity rate was reduced from 50% to 17.5% (p=0.002) and from 27.5% to 0% (p= 0.001) for Propionibacterium acnes and Staphylococcus aureus, respectively, with no difference between the two preparations. The double skin preparation had a more significant effect on bacterial load against CoNS compared to the single skin preparation (p<0.001 versus p= 0.015). In conclusion, both the approaches reduced S. aureus and P. acnes skin load, whereas the double skin preparation is more effective than the single one against CoNS. In light of our findings, preoperative strategies able to reduce bacterial load could potentially increase the final efficacy of perioperative traditional skin preparations.

Antibiotics release from cement spacers used for two-stage treatment of implant-associated infections after total joint arthroplasty

Two‐stage revision arthroplasty is the treatment of choice for periprosthetic infection, a serious complication after knee or hip arthroplasty. Our prospective clinical trial aimed to investigate the concentrations of gentamicin and vancomycin in wound exudate and tissue in two‐stage revision arthroplasty. Wound exudate and periprosthetic membrane samples were collected from 18 patients (10 hip and eight knee patients), who were due for two‐stage treatment after a periprosthetic joint infection. Samples were taken during insertion of antibiotic‐impregnated spacers and after their removal. The concentrations of gentamicin and vancomycin in wound exudates and adjacent tissue were analyzed using high‐performance liquid chromatography mass spectrometry. Average time period of spacer implantation was 13.6 weeks (9.3–22.6 weeks). The concentration of vancomycin in wound exudate decreased from a median of 43.28 μg/mL (0.28–261.22) after implantation to 0.46 μg/mL (0.13–37.47) after the removal of the spacer. In the adjacent tissue, vancomycin concentration was mainly undetectable prior to spacer implantation (0.003 μg/g [0.003–0.261]) and increased to 0.318 μg/g [0.024–484.16] at the time of spacer removal. This was also observed for gentamicin in the tissue of patients who previously had cement‐free implants (0.008 μg/g [0.008–0.087] vs. 0.164 μg/g [0.048–71.75]) while in the tissue of patients with previously cemented prosthesis, baseline concentration was already high (8.451 μg/g [0.152–42.926]). Despite the rapid decrease in antibiotics release from spacer cement observed in vitro, in vivo antibiotics are much longer detectable, especially in the adjacent soft tissue. © 2018 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published By Wiley Periodicals, Inc. J Biomed Mater Res B Part B, 2019. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1587–1597, 2019.

Direct covalent attachment of silver nanoparticles on radical-rich plasma polymer films for antibacterial applications

Prevention and treatment of biomaterial-associated infections (BAI) are imperative requirements for the effective and long-lasting function of orthopedic implants. Surface-functionalization of these materials with antibacterial agents, such as antibiotics, nanoparticles and peptides, is a promising approach to combat BAI. The well-known silver nanoparticles (AgNPs) in particular, although benefiting from strong and broad-range antibacterial efficiency, have been frequently associated with mammalian cell toxicity when physically adsorbed on biomaterials. The majority of irreversible immobilization techniques employed to fabricate AgNP-functionalized surfaces are based on wet-chemistry methods. However, these methods are typically substrate-dependent, complex, and time-consuming. Here we present a simple and dry strategy for the development of polymeric coatings used as platforms for the direct, linker-free covalent attachment of AgNPs onto solid surfaces using ion-assisted plasma polymerization. The resulting coating not only exhibits long-term antibiofilm efficiency against adherent Staphylococcus aureus (S. aureus), but also enhances osteoblast adhesion and proliferation. High resolution X-ray photoelectron spectroscopy (XPS), before and after sodium dodecyl sulfate (SDS) washing, confirms covalent bonding. The development of such silver-functionalized surfaces through a simple, plasma-based process holds great promise for the fabrication of implantable devices with improved tissue-implant integration and reduced biomaterial associated infections.

Preferential Colonization of Osteoblasts Over Co-cultured Bacteria on a Bifunctional Biomaterial Surface

Implant-related infection is a devastating complication in clinical trauma and orthopedics. The aim of this study is to use a bifunctional biomaterial surface in order to investigate the competitive colonization between osteoblasts and bacteria, which is the cause of implant-related infection. A bone-engineering material capable of simultaneously facilitating osteoblast adhesion and inhibiting the growth of Staphylococcus aureus (S. aureus) was prepared. Then, three different co-cultured systems were developed in order to investigate the competitive colonization between the two cohorts on the surface. The results suggested that while the pre-culturing of either cohort compromised the subsequent adhesion of the other according to the ‘race for the surface’ theory, the synergistic effect of preferential cell adhesion and antibacterial activity of the bifunctional surface led to the predominant colonization and survival of osteoblasts, effectively inhibiting the bacterial adhesion and biofilm formation of S. aureus in the co-culture systems with both cohorts. This research offers new insight into the investigation of competitive surface-colonization between osteoblasts and bacteria for implant-related infection.

Preoperative Opioids Increase the Risk of Periprosthetic Joint Infection After Total Joint Arthroplasty

BACKGROUND

Opioids have well-known immunosuppressive properties and preoperative opioid consumption is relatively common among patients undergoing total joint arthroplasty (TJA). The hypothesis of this study was that utilization of opioids preoperatively would increase the incidence of subsequent periprosthetic joint infection (PJI) in patients undergoing primary TJA.

METHODS

A comparative cohort study design was set up that used a cohort of 23,754 TJA patients at a single institution. Patient records were reviewed to extract relevant information, in particular details of opioid consumption, and an internal institutional database of PJI was cross-referenced against the cohort to identify patients who developed a PJI within 2 years of index arthroplasty. Univariate and multivariate linear regression analyses were used to examine the potential association between preoperative opioid consumption and the development of PJI.

RESULTS

Among the total cohort of 23,754 patients, 5051 (21.3%) patients used opioids before index arthroplasty. Preoperative opioid usage overall was found to be a significant risk factor for development of PJI in the univariate (odds ratio, 1.63; P = .005) and multivariate analyses (adjusted odds ratio, 1.53 [95% confidence interval, 1.14-2.05], P = .005).

CONCLUSION

Preoperative opioid consumption is independently associated with a higher risk of developing a PJI after primary TJA. These findings underscore a need for caution when prescribing opioids in patients with degenerative joint disease who may later require arthroplasty.

Survival of Staphylococcus epidermidis in Fibroblasts and Osteoblasts

Staphylococcus epidermidis is a leading cause of infections associated with indwelling medical devices, including prosthetic joint infection. While biofilm formation is assumed to be the main mechanism underlying the chronic infections S. epidermidis causes, we hypothesized that S. epidermidis also evades immune killing, contributing to its pathogenesis. Here, we show that prosthetic joint-associated S. epidermidis isolates can persist intracellularly within human fibroblasts and inside human and mouse osteoblasts. We also show that the intracellularly persisting bacteria reside primarily within acidic phagolysosomes and that over the course of infection, small-colony variants are selected for. Moreover, upon eukaryotic cell death, these bacteria, which can outlive their host, can escape into the extracellular environment, providing them an opportunity to form biofilms on implant surfaces at delayed time points in implant-associated infection. In summary, the acidic phagolysosomes of fibroblasts and osteoblasts serve as reservoirs for chronic or delayed S. epidermidis infection.

Prospective Cohort Study of the Tolerability of Prosthetic Joint Infection Empirical Antimicrobial Therapy

The empirical use of vancomycin in combination with a broad-spectrum beta-lactam is currently recommended after the initial surgery of prosthetic joint infection (PJI). However, the tolerability of such high-dose intravenous regimens is poorly known. Adult patients receiving an empirical antimicrobial therapy (EAT) for a PJI were enrolled in a prospective cohort study (2011 to 2016). EAT-related adverse events (AE) were described according to the common terminology criteria for AE (CTCAE), and their determinants were assessed by logistic regression and Kaplan-Meier curve analysis. The EAT of the 333 included patients (median age, 69.8 years; interquartile range [IQR], 59.3 to 79.1 years) mostly relies on vancomycin (n = 229, 68.8%), piperacillin-tazobactam (n = 131, 39.3%), and/or third-generation cephalosporins (n = 50, 15%). Forty-two patients (12.6%) experienced an EAT-related AE. Ten (20.4%) AE were severe (CTCAE grade ≥ 3). The use of vancomycin (odds ratio [OR], 6.9; 95% confidence interval [95%CI], 2.1 to 22.9), piperacillin-tazobactam (OR, 3.7; 95%CI, 1.8 to 7.2), or the combination of both (OR, 4.1; 95%CI, 2.1 to 8.2) were the only AE predictors. Acute kidney injury (AKI) was the most common AE (n = 25; 51.0% of AE) and was also associated with the use of the vancomycin and piperacillin-tazobactam combination (OR, 6.7; 95%CI, 2.6 to 17.3). A vancomycin plasma overexposure was noted in nine (37.5%) of the vancomycin-related AKIs only. Other vancomycin-based therapies were significantly less at risk for AE and AKI. The EAT of PJI is associated with an important rate of AE, linked with the use of the vancomycin and the piperacillin-tazobactam combination. These results corroborate recent findings suggesting a synergic toxicity of these drugs in comparison to vancomycin-cefepime, which remains to be evaluated in PJI. (This study has been registered at ClinicalTrials.gov under identifier NCT03010293.).

Evaluation of Oritavancin Combinations with Rifampin, Gentamicin, or Linezolid against Prosthetic Joint Infection-Associated Methicillin-Resistant Staphylococcus aureus Biofilms by Time-Kill Assays

The antibiofilm activity of oritavancin in combination with rifampin, gentamicin, or linezolid was evaluated against 10 prosthetic joint infection (PJI)-related methicillin-resistant Staphylococcus aureus (MRSA) isolates by time-kill assays. Oritavancin combined with rifampin demonstrated statistically significant bacterial reductions compared with those of either antimicrobial alone for all 10 isolates (P ≤ 0.001), with synergy being observed for 80% of the isolates. Oritavancin and rifampin combination therapy may be an option for treating MRSA PJI.

Infection safety of dexamethasone in total hip and total knee arthroplasty: a study of eighteen thousand, eight hundred and seventy two operations

PURPOSE

Dexamethasone has been shown to prevent post-operative nausea and vomiting (PONV) and seems to reduce post-operative pain. Both factors, which can extend the hospital stay, delay rehabilitation, and impact patient satisfaction. Because of the immunosuppressive and glucose-rising effects of dexamethasone, there has been concern of its safety in arthroplasty surgery. The purpose of our study was to examine infection safety of dexamethasone in arthroplasty surgery with enough large study material to reliably detect a possible, even small, difference in infection incidence.

METHODS

A total of 18,872 consecutive primary and revision hip and knee arthroplasties were analyzed with data gathered from clinical information databases and a surgical site infection surveillance database with prospective data collection. Also, emergency operations due to fractures were included except for hip hemiarthroplasties.

RESULTS

During the follow-up, 189 (1.0%) prosthetic joint infections (PJIs) occurred: 0.8% after primary arthroplasty and 1.9% after revision arthroplasty. Dexamethasone was used in 2922 (15.5%) operations. The PJI rate in the dexamethasone group was 1.1% (31/2922) and in the non-dexamethasone group 1.0% (161/15950), with no significant difference in the risk of PJI between the two groups (OR 1.052, 95% CI 0.715-1.548, P = 0.773).

CONCLUSIONS

In our study material, the use of a single 5-10 mg dose of dexamethasone did not increase the incidence of post-operative PJI. A low dose of dexamethasone may be safely used to prevent PONV and as part of multimodal analgesia on patients undergoing arthroplasty operation.

Activity of fixed direct electrical current in experimental Staphylococcus aureus foreign-body osteomyelitis

Fixed DC was compared to ceftriaxone, ceftriaxone with 200 μA fixed DC, or no treatment in a rat model of methicillin-susceptible Staphylococcus aureus foreign-body osteomyelitis. After 3 weeks, fewer bacteria were present in bones of the ceftriaxone group (5.71 log₁₀cfu/g [P = 0.0004]) and the ceftriaxone/DC group (3.53 log₁₀cfu/g [P = 0.0002]) than untreated controls (6.70 log₁₀cfu/g). Fewer bacteria were present in the ceftriaxone/DC group than in the ceftriaxone-alone and DC-alone groups (P = 0.0012 and 0.0008, respectively). There were also fewer bacteria on the implanted wires in the groups treated with ceftriaxone (5.47 log₁₀cfu/cm²) or ceftriaxone/DC (2.82 log₁₀cfu/cm²) than in the untreated controls (6.44 log₁₀cfu/cm² [P = 0.0003 and 0.0002, respectively]). There were fewer bacteria in the ceftriaxone/DC rats than in the ceftriaxone-alone- and fixed DC-alone-treated rats (P = 0.0017 and 0.0016, respectively). Fixed DC with an antibiotic may be useful for treating foreign-body infections caused by S. aureus.

Staphylococcus epidermidis from prosthetic joint infections induces lower IL-1β release from human neutrophils than isolates from normal flora

The aim of this study was to test the hypothesis that Staphylococcus epidermidis isolated from prosthetic joint infections (PJIs) differs from S. epidermidis isolated from normal flora in terms of its capacity to induce activation of caspase-1 and release of IL-1β in human neutrophils. The amount of active caspase-1 was determined over 6 h by detecting Ac-YVAD-AMC fluorescence in human neutrophils incubated with S. epidermidis isolates from PJIs (ST2) or normal flora. The amount of IL-1β was detected by ELISA in neutrophil supernatants after 6 h of incubation. Mean IL-1β release was lower after incubation with S. epidermidis from PJIs compared to isolates from normal flora, but no statistically significant difference was found in active caspase-1. Substantial inter-individual differences in both active caspase-1 and IL-1β were noted. These results suggest that evasion of innate immune response, measured as reduced capacity to induce release of IL-1β from human neutrophils, might be involved in the predominance of ST2 in S. epidermidis PJIs, but that other microbe-related factors are probably also important.

The incidence rate, trend and microbiological aetiology of prosthetic joint infection after total knee arthroplasty: A 13 years' experience from a tertiary medical center in Taiwan

BACKGROUND/PURPOSE

Total knee arthroplasty (TKA) improves the patient's quality of life by relieving pain, correcting the deformity, and helping the patient resume normal activities. However, post-TKA prosthetic joint infection leads to implant failure, is difficult to treat, and causes a significant burden both economically and health-wise. Therefore, an understanding of the current trends in this infection and microbiology data is essential for preventing and treating it.

METHODS

A retrospective study was conducted on 10,768 patients who underwent primary TKA at Taipei Veterans General Hospital, Taiwan, from 2002 to 2014. The incidence of post-TKA prosthetic joint infection in different time periods was investigated, and microbiological results in early- (<3 months post-TKA) and delay-onset prosthetic joint infection were analyzed.

RESULTS

The 2 years incidence of post-TKA prosthetic joint infection was 1.93% (2002-2006), 1.05% (2007-2010), and 0.76% (2011-2014). The incidence of post-TKA prosthetic joint infection decreased significantly from 2002 to 2014. Although Staphylococcus species was most commonly isolated, a significantly higher proportion of gram-negative bacteria were isolated from early-onset compared with delay-onset post-TKA prosthetic joint infection patients: 9/29 (31.0%) versus 13/100 (13%); p = 0.023.

CONCLUSIONS

The results showed that the risk of post-TKA prosthetic joint infection is decreasing. Microbiology results showed that early-onset post-TKA prosthetic joint infection is associated with a higher risk of gram-negative bacterial infection. Physicians should be aware of this risk in order to correctly select empirical agents.

The Impact of Common Urologic Complications on the Risk of a Periprosthetic Joint Infection

BACKGROUND

Periprosthetic infections after total hip arthroplasty (THA) or total knee arthroplasty (TKA) are substantial complications, and there are conflicting reports of their association with urologic complications. Our objective was to determine whether urinary tract infection (UTI) and acute urinary retention (AUR) are significant risk factors for joint infections after THA or TKA.

METHODS

We performed a population-based, retrospective cohort study of patients who were ≥66 years old when they underwent an initial THA or TKA between April 2003 and March 2013. Investigated exposures included a UTI presenting for treatment within 2 years after joint replacement, as well as AUR within 30 days after THA or TKA. The primary outcome was joint infection requiring hospital admission following THA or TKA (which had to occur within 2.25 years after THA or TKA for the UTI exposure or 120 days for the AUR exposure).

RESULTS

A total of 113,061 patients met the inclusion criteria and had arthroplasties (44,495 THAs and 68,566 TKAs) during the study period. The median age was 74 years (interquartile range [IQR], 70 to 79 years). Of those patients, 28,256 (25.0%) had at least 1 UTI and they were more likely to be older and female; to have had previous antibiotic exposure, cystoscopy, or urinary retention; and to have atrial fibrillation. Most of those UTIs were coded as nonspecific UTI, and the patient was seen for outpatient treatment in a non-emergency department setting. A total of 2,516 patients (2.2%) had AUR within 30 days of the procedure. Those patients were more likely to be older and male, to have medical comorbidities, to have had previous transurethral procedures or cystoscopy and previous urology visits, and to have received a general anesthetic during their procedure. A total of 1,262 patients (1.1%) had joint infection requiring hospital admission. In multivariate Cox regression analysis, UTI was associated with an increased risk of joint infection (hazard ratio [HR], 1.21 [95% confidence interval (CI), 1.14 to 1.28]; p < 0.01). However multivariate analysis did not demonstrate an association between AUR and joint infection (HR, 0.99 [95% CI, 0.60 to 1.64]; p = 0.98).

CONCLUSIONS

UTI was associated with increased risk of hip or knee periprosthetic joint infection, whereas AUR was not a significant risk factor. Timely and appropriate treatment of symptomatic UTIs in this patient population may be important to prevent periprosthetic joint infection.

LEVEL OF EVIDENCE

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

Management of Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is a serious complication after arthroplasty, which is associated with pain, prolonged hospital stay, multiple surgeries, functional incapacitation, and even mortality. Using scientific and efficient management protocol including modern diagnosis and treatment of PJI and eradication of infection is possible in a high percentage of affected patients. In this article, we review the current knowledge in epidemiology, classification, pathogenesis, diagnosis and treatment of PJI.

Coatings as the useful drug delivery system for the prevention of implant-related infections

Implant-related infections (IRIs) which led to a large amount of medical expenditure were caused by bacteria and fungi that involve the implants in the operation or in ward. Traditional treatments of IRIs were comprised of repeated radical debridement, replacement of internal fixators, and intravenous antibiotics. It needed a long time and numbers of surgeries to cure, which meant a catastrophe to patients. So how to prevent it was more important than to cure it. As an excellent local release system, coating is a good idea by its local drug infusion and barrier effect on resisting biofilms which were the main cause of IRIs. So in this review, materials used for coatings and evidences of prevention were elaborated.

Histopathological Diagnosis of Prosthetic Joint Infection: Does a Threshold of 23 Neutrophils Do Better than Classification of the Periprosthetic Membrane in a Prospective Multicenter Study?

No gold standard exists for histopathological diagnosis of a prosthetic joint infection (PJI). The historical criterion considers the presence of neutrophil infiltration upon examination of periprosthetic tissue. Morawietz et al. proposed a classification of periprosthetic membranes (Morawietz et al., Clin Pathol 59:591-597, 2006, https://doi.org/10.1136/jcp.2005.027458) and a more recently described classification with a new cutoff value of 23 neutrophils in 10 high-power fields (Morawietz et al., Histopathology 54:847-853, 2009. https://doi.org/10.1111/j.1365-2559.2009.03313.x). We performed a multicenter prospective study, which compared both methods for the diagnosis of PJI. All suspicions of PJI (n = 264) between December 2010 and March 2012 in seven centers were prospectively included. Five perioperative specimens were collected per patient for cultures, and one was collected for histology. Diagnosis of PJI was made according to the Infectious Diseases Society of America (IDSA) guidelines. Histopathological analysis classified the patients according to the threshold of 23 neutrophils and according to the classification of Morawietz. Performances of both methods were compared by using clinical and/or bacteriological criteria as the gold standard. Among 264 patients with suspected PJI, a diagnosis of infection was confirmed in 215 and unconfirmed in 49 patients. Histopathological analysis was available for 150 confirmed PJI and 40 unconfirmed PJI cases. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 78.7%, 90.0%, 96.7%, 52.9%, and 81.1%, respectively, for the Morawietz classification, and 82.0%, 90.0%, 96.9%, 57.1%, and 83.7%, respectively, for the 23-neutrophil threshold. The new algorithm using a threshold of 23 neutrophils can be proposed as a new gold standard for the histopathological diagnosis of PJI.

Risk Factors and Treatment Options for Failure of a Two-Stage Exchange

PURPOSE OF REVIEW

Although a two-stage exchange revision is reported to have a high success rate, this strategy may fail as a treatment for prosthetic joint infection (PJI). When it does, resection arthroplasty, arthrodesis, amputation, and chronic antibiotic suppression may play a role. The purpose of this review is to determine which are the main risk factors for a two-stage exchange failure and to analyze the indications and results of resection arthroplasty, arthrodesis, amputation, and antibiotic chronic suppression for PJI.

RECENT FINDINGS

Recent literature demonstrates that the main risk factors for a two-stage exchange failure are as follows: hemodialysis, obesity, multiple previous procedures, diabetes mellitus, corticosteroid therapy, hypoalbuminemia, immunosuppression, rheumatological conditions, coagulation disorders, and infection due to multidrug-resistant (MDR) bacteria or fungal species. Regarding microorganisms, besides Staphylococcus aureus, Streptococcus spp., Enterobacteriaceae species such as Klebsiella pneumoniae and Enterobacter sp., Pseudomonas aeruginosa, or Acinetobacter baumannii, and fungus including Candida sp. are also considered risk factors for a two-stage exchange failure. Resection arthroplasty, arthrodesis, and amputation have a limited role. Chronic suppression is an option for high-risk patients or unfeasible reconstruction. In summary, we report the main risk factors for a two-stage exchange failure and alternative procedures when it occurs. Future research on patient-specific risk factors for a two-stage exchange may aid surgical decision-making and optimization of outcomes.

Treatment of periprosthetic joint infection of the elbow: 15-year experience at a single institution

BACKGROUND

Total elbow arthroplasty (TEA) can be complicated by periprosthetic joint infection (PJI) with potentially catastrophic failure. The purpose of this study was to describe the results of elbow PJI treatment at a tertiary-care referral center.

METHODS

An institutional TEA database was queried for infection and reoperation after TEA. Patients who underwent irrigation and débridement (I&D) with component retention were compared with those who underwent component explantation, antibiotic spacer placement, and reimplantation of a revision TEA.

RESULTS

A total of 26 patients (10 men; mean age, 64.3 years) were treated for PJI of TEA. There were 3 polymicrobial infections (11.5%) and 13 Staphylococcus aureus infections (50%) (4 methicillin resistant); 6 patients (23.1%) had negative culture results. Ten patients (38.5%) underwent I&D and component retention, with 5 of those patients (5 of 10, 50%) having recurrent infection at an average of 3.1 years (range, 0.25-7.8 years) after I&D. Of 16 patients who underwent antibiotic spacer placement, 12 (75%) underwent 2-stage reimplantation of a TEA. Among those with reimplantation, 4 of 12 (33.3%) required reoperation. In 3 of 12 (25.0%), reoperation was required for infection, whereas 1 of 12 (8.3%) required surgery for mechanical complications.

CONCLUSION

Two-stage revision results in a decreased rate of recurrent PJI. Certain patients (those with poor health or well-fixed components) may be more suitable for I&D and component retention, with a demonstrated 50% success rate over a period of 3 years. Longer-term follow-up may result in higher reinfection rates in both groups.

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.

A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2018 Update by the Infectious Diseases Society of America and the American Society for Microbiology

The critical nature of the microbiology laboratory in infectious disease diagnosis calls for a close, positive working relationship between the physician/advanced practice provider and the microbiologists who provide enormous value to the healthcare team. This document, developed by experts in laboratory and adult and pediatric clinical medicine, provides information on which tests are valuable and in which contexts, and on tests that add little or no value for diagnostic decisions. This document presents a system-based approach rather than specimen-based approach, and includes bloodstream and cardiovascular system infections, central nervous system infections, ocular infections, soft tissue infections of the head and neck, upper and lower respiratory infections, infections of the gastrointestinal tract, intra-abdominal infections, bone and joint infections, urinary tract infections, genital infections, and other skin and soft tissue infections; or into etiologic agent groups, including arthropod-borne infections, viral syndromes, and blood and tissue parasite infections. Each section contains introductory concepts, a summary of key points, and detailed tables that list suspected agents; the most reliable tests to order; the samples (and volumes) to collect in order of preference; specimen transport devices, procedures, times, and temperatures; and detailed notes on specific issues regarding the test methods, such as when tests are likely to require a specialized laboratory or have prolonged turnaround times. In addition, the pediatric needs of specimen management are also emphasized. There is intentional redundancy among the tables and sections, as many agents and assay choices overlap. The document is intended to serve as a guidance for physicians in choosing tests that will aid them to quickly and accurately diagnose infectious diseases in their patients.

Metagenomics for Clinical Infectious Disease Diagnostics Steps Closer to Reality

Metagenomics approaches based on shotgun next-generation sequencing hold promise for infectious disease diagnostics. Despite substantial challenges that remain, work done over the past few years justifies excitement about the potential for these approaches to transform how clinical pathogen identification and analysis are performed. In an article in this issue of the Journal of Clinical Microbiology, M. I. Ivy et al. (J Clin Microbiol 56:e00402-18, 2018, https://doi.org/10.1128/JCM.00402-18) have applied a shotgun metagenomics approach to the diagnosis of prosthetic joint infections directly from synovial fluid. The results from this work demonstrate both the potentials and challenges of this approach applied in the clinical microbiology laboratory.

Direct Detection and Identification of Prosthetic Joint Infection Pathogens in Synovial Fluid by Metagenomic Shotgun Sequencing

Metagenomic shotgun sequencing has the potential to transform how serious infections are diagnosed by offering universal, culture-free pathogen detection. This may be especially advantageous for microbial diagnosis of prosthetic joint infection (PJI) by synovial fluid analysis since synovial fluid cultures are not universally positive and since synovial fluid is easily obtained preoperatively. We applied a metagenomics-based approach to synovial fluid in an attempt to detect microorganisms in 168 failed total knee arthroplasties. Genus- and species-level analyses of metagenomic sequencing yielded the known pathogen in 74 (90%) and 68 (83%) of the 82 culture-positive PJIs analyzed, respectively, with testing of two (2%) and three (4%) samples, respectively, yielding additional pathogens not detected by culture. For the 25 culture-negative PJIs tested, genus- and species-level analyses yielded 19 (76%) and 21 (84%) samples with insignificant findings, respectively, and 6 (24%) and 4 (16%) with potential pathogens detected, respectively. Genus- and species-level analyses of the 60 culture-negative aseptic failure cases yielded 53 (88%) and 56 (93%) cases with insignificant findings and 7 (12%) and 4 (7%) with potential clinically significant organisms detected, respectively. There was one case of aseptic failure with synovial fluid culture growth; metagenomic analysis showed insignificant findings, suggesting possible synovial fluid culture contamination. Metagenomic shotgun sequencing can detect pathogens involved in PJI when applied to synovial fluid and may be particularly useful for culture-negative cases.

Should we expand the indications for the DAIR (debridement, antibiotic therapy, and implant retention) procedure for Staphylococcus aureus prosthetic joint infections? A multicenter retrospective study

To evaluate factors associated with failure in patients treated with DAIR (debridement, antibiotic therapy, and implant retention) for Staphylococcus aureus prosthetic joint infections (PJIs). We retrospectively analyzed consecutive patients with stable PJI due to S. aureus treated with DAIR at six hospitals between 2010 and 2014. Cox proportional hazards regression was used to study factors associated with treatment failure at 2 years. Of 154 eligible patients, 137 were included (mean age 73 ± 13 years; male 56%). The estimated success rate according to the Kaplan-Meier method was 76.2 [95% CI 68-83] at 2 years of follow-up. In multivariate analysis, longer duration of treatment (hazard ratio (HR) 0.78 [0.69-0.88]; p < 0.001) and combination therapy including rifampin (HR 0.08 [0.018-0.36]; p = 0.001) were independently associated with success, whereas active smoking was independently associated with failure (HR 3.6 [1.09-11.84]; p = 0.036). When the analysis was restricted to patients with early infection onset (< 3 months), early acute infection was also predictive of a better prognosis (HR 0.25 [0.09-0.7]; p = 0.009). Failure was not associated with time from prosthesis insertion to debridement, nor with duration of symptoms > 3 weeks and type of prosthesis (hip or knee). These results remained unchanged when the 14 patients under immunosuppressive therapy were removed from analysis. These data suggest that DAIR can be performed even if infection and symptoms are delayed but reserved to patients who are able to follow rifampin-based combination therapy for a prolonged duration that should not be different for hip and knee PJI.

OPAT: proof of concept in a peripheral Belgian hospital after review of the literature

Since its introduction in the 1970s in the United States, outpatient parenteral antibiotic/antimicrobial therapy (OPAT) has been adopted internationally for long-term intravenous (IV) treatment of stable infectious diseases. The aim is to provide a safe and successful completion of IV antimicrobial treatment at the ambulatory care center or at home without complications and costs associated with hospitalization. OPAT implementation has been accelerated by progress in vascular access devices, newly available antibiotics, the emphasis on cost-savings, as well as an improved patient comfort and a reduced incidence of health care associated infections with a similar outcome. OPAT utilization is supported by an extensive published experience and guidelines of the British Society of Antimicrobial Chemotherapy and the Infectious Diseases Society of America for adults as well as for children. Despite these recommendations and its widespread adoption, in Belgium OPAT is only fully reimbursed and established for cystic fibrosis patients. Possible explanations for this unpopularity include physician unfamiliarity and a lack of uniform funding arrangements with higher costs for the patient. This article aims to briefly review benefits, risks, indications, financial impact for supporting OPAT in a non-university hospital as standard of care. Our experience with OPAT at the ambulatory care center of our hospital and its subsequent recent introduction in the home setting is discussed.

Is the Enzyme-linked Immunosorbent Assay More Accurate Than the Lateral Flow Alpha Defensin Test for Diagnosing Periprosthetic Joint Infection?

BACKGROUND

Alpha defensin was proposed as a new biomarker in synovial fluid for the diagnostic workup of failed joint prostheses. To our knowledge, no comparative study of the performance of the quantitative enzyme-linked immunosorbent assay (ELISA) and qualitative lateral flow alpha defensin test has been reported.

QUESTIONS/PURPOSES

(1) Using the proposed European Bone and Joint Infection Society (EBJIS) criteria for defining periprosthetic joint infection (PJI), is there a difference in the diagnostic accuracy of quantitative ELISA and qualitative lateral flow alpha defensin tests? (2) Is there a difference in the performance of the two alpha defensin tests when using three definition classification systems (Musculoskeletal Infection Society [MSIS], Infectious Diseases Society of America [IDSA], and proposed EBJIS)?

METHODS

In this retrospective study of samples collected earlier as part of a related longitudinal study, we included patients in whom aspiration of the prosthetic hip or knee was performed as routine investigation before every revision arthroplasty. Between October 2016 and April 2017, a total of 73 patients were eligible for inclusion. As a result of an insufficient fluid volume for analysis (< 5 mL), two patients were excluded. Among the 71 patients in the final analysis, 54 had a knee and 17 a hip arthroplasty. Using the proposed EBJIS criteria, PJI was diagnosed in 22 patients (31%) and aseptic failure in 49 (69%). The alpha defensin ELISA and lateral flow tests were performed in synovial fluid. Patients were classified as having PJI or aseptic failure using the MSIS, the IDSA, and the proposed EBJIS criteria. Sensitivity and specificity of ELISA and the lateral flow alpha defensin test were calculated. Based on receiver operating characteristic analysis, area under the curve values were compared.

RESULTS

When measured against the proposed EBJIS criteria, the sensitivity of alpha defensin ELISA and the lateral flow test was low and not different from one another with the numbers available at 50% (95% confidence interval [CI], 31%-69%) and 46% (95% CI, 27%-65%; p = 0.857), respectively, whereas both methods showed high specificity (98% [95% CI, 88%-100%]; p = 1.000). For sensitivity, the highest values were seen when compared against the MSIS criteria (ELISA: 85% [95% CI, 56%-97%], lateral flow: 77% [95% CI]; p = 0.871), intermediate with IDSA criteria (ELISA: 73% [95% CI, 48%-89%], lateral flow: 67% [95% CI]; p = 0.867), and lowest with proposed EBJIS criteria (ELISA: 50% [95% CI, 31%-69%], lateral flow: 46% [95% CI]; p = 0.763). Specificity, however, was high regardless of the criteria used, where ELISA and lateral flow produced results that were not different (MSIS: 98% [95% CI, 90%-100%], IDSA: 98% [95% CI, 90%-100%], EBJIS: 98% [95% CI, 88%-100%]; p = 1.000). The area under the curve of alpha defensin ELISA and the lateral flow test was similar, regardless of the definition criteria used (EBJIS: p = 0.566; IDSA: p = 0.425; MSIS: p = 0.339).

CONCLUSIONS

There is no difference between the quantitative and qualitative alpha defensin test for confirmation of PJI, irrespective of applied definition criteria. Having the advantage of providing results within 10 minutes without the need for a laboratory facility, the qualitative test may be of interest in the intraoperative setting, however, at a cost of higher test expense.

LEVEL OF EVIDENCE

Level I, diagnostic study.

Candida periprosthetic joint infection: A rare and difficult-to-treat infection

BACKGROUND

Candida periprosthetic joint infection (CPJI) is a rare, difficult-to-treat disease. The purpose of this study was to evaluate the clinical characteristics and outcomes of CPJI treated with various surgical and antifungal strategies.

METHODS

We conducted a multicenter retrospective study of all CPJI diagnosed between 2003 and 2015 in 16 Spanish hospitals.

RESULTS

Forty-three patients included: median age, 75 years, and median Charlson Comorbidity Index score, 4. Thirty-four (79.1%) patients had ≥1 risk factor for Candida infection. Most common causative species were C. albicans and C. parapsilosis. Thirty-five patients were evaluable for outcome: overall, treatment succeeded in 17 (48.6%) and failed in 18 (51.4%). Success was 13/20 (67%) in patients with prosthesis removal and 4/15 (27%) with debridement and prosthesis retention (p = 0.041). All 3 patients who received an amphotericin B-impregnated cement spacer cured. In the prosthesis removal group, success was 5/6 (83%) with an antibiofilm regimen and 8/13 (62%) with azoles (p = 0.605). In the debridement and prosthesis retention group, success was 3/10 (30%) with azoles and 1/5 (20%) with antibiofilm agents. Therapeutic failure was due to relapse in 9 patients, need for suppressive treatment in 5, persistent infection in 2, and CPJI-related death in 2; overall attributable mortality was 6%.

CONCLUSIONS

CPJI is usually a chronic disease in patients with comorbidities and risk factors for Candida infection. Treatment success is low, and prosthesis removal improves outcome. Although there is insufficient evidence that use of antifungals with antibiofilm activity has additional benefits, our experience indicates it may be recommendable.

Prosthetic Joint Infections Caused by Candida Species: A Systematic Review and a Case Series

The purpose of this study was to evaluate the efficacy of echinocandins in the treatment of Candida prosthetic joint infection (PJI) based on published literature and on patients we examined. A structured literature review of multiple databases was conducted to identify patients who received echinocandins for Candida PJIs. Additionally, we describe here the first cases of PJIs due to C. parapsilosis, successfully treated with prolonged anidulafungin therapy. Out of 17 patients, 12 were female and the mean age at diagnosis was 66.0 years. No risk factors associated with Candida PJIs were found in four patients (23.5%). Infection sites included the knee (n = 10, 62.5%), the hip (n = 6, 35.3%) and the shoulder (n = 1, 5.9%). The most frequently isolated Candida species were C. albicans (n = 7, 41.2%) and C. glabrata (n = 7, 41.2%), followed by C. parapsilosis (n = 2, 11.8%) and C. freyschussii (n = 1, 5.9%). All patients were cured with the combination of systemic antifungal therapy and surgical interventions. Two-stage exchange arthroplasty and resection arthroplasty were performed in five and nine patients, respectively. The most frequently used echinocandins were caspofungin (n = 11, 64.7%), followed by anidulafungin (n = 4, 23.5%) and micafungin (n = 2, 11.8%). The median duration (days) of echinocandin therapy was as follows: caspofungin (25.5, range 8-56), micafungin (14.0, range 4-56) and anidulafungin (58, range 14-90). This study supports the effective role of echinocandins, as well as the potential advantage of surgical intervention in the treatment of Candida PJIs. Furthermore, it provides fundamental data on the safety of long-term echinocandin therapy.

In vitro activity of oritavancin in combination with rifampin or gentamicin against prosthetic joint infection-associated methicillin-resistant Staphylococcus epidermidis biofilms

This study evaluated the in vitro activity of oritavancin in combination with rifampin or gentamicin against methicillin-resistant Staphylococcus epidermidis (MRSE) biofilms. Oritavancin, rifampin, and gentamicin were tested against 20 MRSE isolates recovered from prosthetic joint infection (PJI). Time-kill studies were used to evaluate the activities of the three antimicrobial agents individually vs. combinations of oritavancin with rifampin or gentamicin against MRSE biofilms formed on Teflon coupons. At 24 h, the combination of oritavancin and rifampin resulted in a significant (P≤0.001) reduction in biofilm density compared with either antimicrobial alone for 85% (17/20) of isolates. Oritavancin combined with gentamicin showed a significant (P≤0.001) reduction in biofilm density compared with either antimicrobial alone against 55% (11/20) of isolates at 24 h. Synergy (defined as a ≥2 log₁₀ cfu/cm² decrease at 24 h for the antimicrobial combination compared with the most active single antimicrobial) was observed against 65% (13/20) of the isolates for oritavancin in combination with rifampin and 35% (7/20) of the isolates for oritavancin in combination with gentamicin. Oritavancin in combination with rifampin or gentamicin demonstrated bactericidal activity (defined as a ≥3 log₁₀ cfu/cm² reduction at 24 h from the starting biofilm bacterial density) for 85% (17/20) and 80% (16/20) isolates, respectively. Our study suggests that oritavancin and rifampin combination therapy may be an option for antimicrobial management of PJIs caused by MRSE.

Highly Stabilized Nanoparticles on Poly-l-Lysine-Coated Oxidized Metals: A Versatile Platform with Enhanced Antimicrobial Activity

The increasing incidence of infections in implantable devices has encouraged the search for biocompatible antimicrobial surfaces. To inhibit the bacterial adhesion and proliferation on biomaterials, several surface functionalization strategies have been developed. However, most of these strategies lead to bacteriostatic effect and only few of these are able to reach the bactericidal condition. In this work, bactericidal surfaces were designed through the functionalization of titanium surfaces with poly-l-lysine (PLL) as the mediator for the incorporation of antimicrobial silver nanoparticles (AgNPs). This functionalization influences the adsorption of the particles on the substrate impeding the agglomeration observed when bare titanium surfaces are used, leading to a homogeneous distribution of AgNPs on the surfaces. The antimicrobial activity of this surface has been tested against two different strains, namely, Staphylococcus aureus and Pseudomonas aeruginosa. For both strains and different AgNPs sizes, the surface modified with PLL and AgNPs shows a much enhanced antimicrobial activity in comparison with AgNPs deposited on bare titanium. This enhanced antibacterial activity is high enough to reach bactericidal effect, a condition hard to achieve in antimicrobial surfaces. Importantly, the designed surfaces are able to decrease the bacterial viability more than 5 orders with respect to the initial bacterial inoculum. That means that a relative low load of AgNPs on the PLL-modified titanium surfaces reaches 99.999% bacterial death after 24 h. The results of the present study are important to avoid infections in indwelling materials by reinforcing the preventive antibiotic therapy usually dosed throughout the surgical procedure and during the postoperative period.

Cerclages after Femoral Osteotomy Are at Risk for Bacterial Colonization during Two-Stage Septic Total Hip Arthroplasty Revision

Aims: In cases of a two-stage septic total hip arthroplasty (THA) exchange a femoral osteotomy with subsequent cerclage stabilization may be necessary to remove a well-fixed stem. This study aims to investigate the rate of bacterial colonization and risk of infection persistence associated with in situ cerclage hardware in two-stage septic THA exchange.

Patients and Methods: Twenty-three patients undergoing two-stage THA exchange between 2011 and 2016 were included in this retrospective cohort study. During the re-implantation procedure synovial fluid, periprosthetic tissue samples and sonicate fluid cultures (SFC) of the cerclage hardware were acquired.

Results: Seven of 23 (30%) cerclage-SFC produced a positive bacterial isolation. Six of the seven positive cerclage-SFC were acquired during THA re-implantation.

Two of the seven patients (29%) with a positive bacterial isolation from the cerclage hardware underwent a THA-revision for septic complications. The other five patients had their THA in situ at last follow-up.

Conclusions: Despite surgical debridement and antimicrobial therapy, a bacterial colonization of cerclage hardware occurs and poses a risk for infection persistence. All cerclage hardware should be removed or exchanged during THA reimplantation.

The Cost-Effectiveness of Preoperative Staphylococcus aureus Screening and Decolonization in Total Joint Arthroplasty

BACKGROUND

This article presents a break-even analysis for preoperative Staphylococcus aureus colonization screening and decolonization protocols in total hip arthroplasty (THA) and total knee arthroplasty (TKA).

METHODS

Protocol costs, baseline infection rates after arthroplasty, and average revision costs were obtained from institutional records and the literature. The break-even analysis determined the absolute risk reduction (ARR) in infection rate required for cost-effectiveness.

RESULTS

S aureus nasal screening ($144.07) was cost effective when initial infection rates of TKA (1.10%) and THA (1.63%) had an ARR of 0.56% and 0.45%, respectively. The most inexpensive decolonization treatment ($5.09) was cost effective with an ARR of 0.02% for both TKA and THA. The most expensive decolonization option ($37.67) was cost effective with ARRs of 0.15% (TKA) and 0.12% (THA).

CONCLUSION

Preoperative S aureus decolonization can be highly cost effective, whereas colonization screening requires excessively high reductions in infection rate.

Diagnostic Utility of Histological Analysis for Detecting Ongoing Infection During Two-Stage Revision Arthroplasty in Patients With Inflammatory Arthritis

BACKGROUND

Surgeons often rely on intra-operative histology (frozen sections [FS]) to determine the next step in surgical management during the second stage (re-implantation surgery) of 2-stage revision arthroplasty. The purpose of the study is to assess the accuracy of permanent sections (PS) and FS in the diagnosis of persistent infection during re-implantation in patients with an inflammatory arthritis.

METHODS

From 2001 to 2016, 47 planned second-stage revision total hip arthroplasty and total knee arthroplasty in patients with inflammatory arthritis were identified. Revisions were classified as having persistent infection if they were Musculoskeletal Infection Society positive at the time of second stage. PS or FS was considered to be positive for infection when at least one of the specimens demonstrated an acute inflammation. Receiver operating characteristic analysis was performed to obtain the diagnostic parameters.

RESULTS

There were 9 (19%) persistent infections. Both PS and FS had very high specificity (PS = FS = 94.7%). Sensitivity of PS was higher than FS, although not statistically significant (PS = 88.9%, FS = 55.6%, P = .083). Overall, PS had a better diagnostic utility than FS (area under the curve: PS vs FS = 0.92 vs 0.75, P = .045). Four specimens had discrepancies between PS and FS histology. In all 4 instances, the specimens were read as positive (infected) by PS, but negative by FS.

CONCLUSION

Histological analysis is recommended at the time of re-implantation surgery even in patients with inflammatory arthritis. PS had a better diagnostic utility than FS suggesting that areas of acute inflammation may be scattered and may not always be captured in the specimens taken for FS.

A Survey of the Prevalence of and Techniques to Prevent Trunnionosis

Trunnionosis of total hip arthroplasty (THA) components has been an increasingly reported complication. Consensus is lacking regarding preventive practices and the overall incidence of trunnionosis. In this study, fellowship-trained adult reconstruction orthopedic surgeons were surveyed to identify expert opinions. A 25-question, web-based survey regarding trunnionosis incidence, prevention, and biomaterials was sent to 345 fellowship-trained adult reconstruction orthopedic surgeons in North America. The survey yielded 151 (43.8%) responses from surgeons with a mean of 11.97±9.49 years of experience. These surgeons believe that the material composite of the head-neck junction is the most important contributor to trunnionosis. They often choose a ceramic head with a metal alloy stem to reduce trunnionosis. They more commonly impact the femoral head 3 times than once. Fifty-one percent believe that trunnionosis leads to THA failure for between 0% and 2% of all THA revisions, whereas 48.3% believe that the failure rate is greater than 2%. More than half (53.6%) of these surgeons recommend a revision THA if a patient's serum cobalt level is greater than 10 µg/L, regardless of symptom presence. The incidence of trunnionosis appears to be increasing due to changes in implants and/or an increased awareness of the problem, with 48.3% of these surgeons believing that trunnionosis is the primary cause of THA failure for more than 1 in 50 patients. Some suggested preventive measures include cleaning and drying the trunnion, using ceramic femoral heads, matching THA components, and adding titanium sleeves on well-fixed stems that are retained during revision surgery. [Orthopedics. 2018; 41(4):e557-e562.].

In-Hospital Acute Kidney Injury After TKA Revision With Placement of an Antibiotic Cement Spacer

BACKGROUND

There is mounting evidence that treatment of periprosthetic joint infection of the knee with an antibiotic cement spacer (ACS) may increase risk for acute kidney injury (AKI). We sought to determine the incidence, as well as potential risk factors, of in-hospital AKI in this cohort.

METHODS

We retrospectively identified 75 patients that received either a static or articulating ACS at a single institution. In-hospital AKI was defined by a more than 50% rise in serum creatinine from preoperative baseline to at least 1.4 mg/dL. Our secondary outcome was percent change in creatinine from preoperative to peak postoperative value. Variables were analyzed for the outcome of AKI with univariate logistic regression. A final multivariate model for percent change in creatinine was formed while controlling for age, gender, body mass index, and baseline creatinine.

RESULTS

The incidence of AKI was 14.6%, occurring at a mean of 6.3 days (2-8 days). A lower preoperative hemoglobin (odds ratio = 1.82, P = .015) significantly increased risk for AKI on univariate analysis. Diagnosis of either hypertension or diabetes also showed a strong statistical trend (P = .056). On multivariate regression, lower preoperative hemoglobin significantly correlated with a greater percent rise in creatinine postoperatively (β = 0.30, P = .015).

CONCLUSION

The incidence of AKI in patients who receive ACS is relatively high, raising clinical concern in the care of periprosthetic joint infection patients. Our results suggest that a lower baseline hemoglobin may be involved in the etiology of AKI in this population. Therefore, it may be clinically appropriate to monitor anemic patients for AKI when implanting an ACS.

Low-Virulence Organisms and Periprosthetic Joint Infection-Biofilm Considerations of These Organisms

PURPOSE OF REVIEW

The purpose of this manuscript is to provide a critical review of peer-reviewed literature over the last 5 years related to low virulent organisms associated with periprosthetic joint infection (PJI). We evaluated the most common organisms, the diagnostic challenges, and the novel tools available in the perioperative workup of PJI as well as the current understanding of how biofilm potentiates the indolent clinical presentation and explore a possible shift in the surgical management of these patients.

RECENT FINDINGS

Biofilm actively prevents macrophage phagocytosis by suppressing proinflammatory activity through the recruitment of myeloid-derived suppressor cells. Given the appropriate host and organism conditions, increased utilization of one-stage exchange arthroplasty in the surgical treatment of these low virulent infections may be on the rise. Biomarkers and molecular techniques offer encouraging results to diagnose low virulent organisms and future research focused on the disruption of biofilm may ultimately give rise to improved treatment strategies.

Total hip arthroplasty infection caused by an unusual organism, Salmonella; its successful management and literature review

Prosthetic joint infection due to Salmonella spp is rare. Here we report an acute case of Salmonella enteritidis infection of a total hip arthroplasty in a man taking immunosuppressant medication. He was managed with antibiotics and two-stage revision surgery.

Arginase-1 Expression in Myeloid Cells Regulates Staphylococcus aureus Planktonic but Not Biofilm Infection

Staphylococcus aureus is a leading cause of device-associated biofilm infections, which represent a serious health care concern based on their chronicity and antibiotic resistance. We previously reported that S. aureus biofilms preferentially recruit myeloid-derived suppressor cells (MDSCs), which promote monocyte and macrophage anti-inflammatory properties. This is associated with increased myeloid arginase-1 (Arg-1) expression, which has been linked to anti-inflammatory and profibrotic activities that are observed during S. aureus biofilm infections. To determine whether MDSCs and macrophages utilize Arg-1 to promote biofilm infection, Arg-1 was deleted in myeloid cells by use of Tie-2^Cre mice. Despite Arg-1 expression in biofilm-associated myeloid cells, bacterial burdens and leukocyte infiltrates were similar between wild-type (WT) and Arg-1^fl/fl;Tie-2^Cre conditional knockout (KO) mice from days 3 to 14 postinfection in both orthopedic implant and catheter-associated biofilm models. However, inducible nitric oxide synthase (iNOS) expression was dramatically elevated in biofilm-associated MDSCs from Arg-1^fl/fl;Tie-2^Cre animals, suggesting a potential Arg-1-independent compensatory mechanism for MDSC-mediated immunomodulation. Treatment of Arg-1^fl/fl;Tie-2^Cre mice with the iNOS inhibitor N6-(1-iminoethyl)-l-lysine (l-NIL) had no effect on biofilm burdens or immune infiltrates, whereas treatment of WT mice with the Arg-1/ornithine decarboxylase inhibitor difluoromethylornithine (DFMO) increased bacterial titers, but only in the surrounding soft tissues, which possess attributes of a planktonic environment. A role for myeloid-derived Arg-1 in regulating planktonic infection was confirmed using a subcutaneous abscess model, in which S. aureus burdens were significantly increased in Arg-1^fl/fl;Tie-2^Cre mice compared to those in WT mice. Collectively, these results indicate that the effects of myeloid Arg-1 are context dependent and are manifest during planktonic but not biofilm infection.

The Preoperative Microbial Detection is No Prerequisite for the Indication of Septic Revision in Cases of Suspected Periprosthetic Joint Infection

Aim of This Study

Periprosthetic joint infections (PJIs) require a special antimicrobial regimen, fundamentally different from an aseptic treatment, making a correct preoperative diagnosis essential. However, a successful preoperative microbe detection is not always possible. We wanted to find out (1) if a preoperative microbe detection is a prerequisite before starting a septic revision in suspected PJIs or if the preoperative diagnosis can solely be based on (para)clinical signs (persistent CRP >1 mg/dl, early X-ray loosening signs in the first 5 years, leucocytes joint aspiration >1700/µl, conspicuous history, and clinical signs like redness, pain, hyperthermia, swelling, and loss of function); (2) if patients with and without preoperative microbe detection have a different outcome; and (3) if the microbial growth is the most important criterion of a multifactorial PJI definition.

Methods

We included all first-line two-stage hip (49) and knee (47) revisions, performed in our department from 06/2013 on, with an available 2-year follow-up. A PJI was defined as one of the following four criteria: fistula or purulence, Krenn Morawietz type 2 or 3, joint aspirate > 2000/μl leukocytes or >70% granulocytes, and microbial growth. This multifactorial PJI definition was based on the European Bone and Joint Infection Society (EBJIS). The standardized diagnostic algorithm is described in detail.

Results

(1) 24 hip and 16 knee cases were treated without preoperative microbe detection solely on the basis of a (para)clinical diagnosis (see above). In the hip 91.6% (22 of 24 cases) showed an intraoperative microbe detection. In the knee, in 68.7% (11 of 16 cases) a microbe was detected intraoperatively and in 93.7% (15 of 16) at least one secure PJI criterion could be confirmed intraoperatively. (2) No statistical significant (p .517) difference between patients with (n = 56, reinfection rate 8.9%) and without (n = 40, 15%) preoperative microbe detection was found in a 2-year follow-up. (3) Microbial growth remains the overall (pre- and intraoperatively) most important criterion (hip 95.9%; knee 89.3%), followed by Krenn Morawietz for the intraoperative diagnosis (hip 67.3%, knee 48.9%), and joint aspiration for the knee and fistula for the hip, respectively, as preoperative criteria.

Conclusion

High rates of intraoperatively fulfilled EBJIS PJI criteria show that a preoperative microbe detection is not necessary before intervening in suspected PJIs. The indication for a septic revision can solely be based on (para)clinical signs. The new established diagnostic algorithm based on a multifactorial PJI definition showed high precision in finding PJIs.

SPECT/CT in the Postoperative Painful Knee

This review summarizes the role of SPECT/CT in patients with a painful postoperative knee and describes typical diagnostic criteria in these patients. Pain after knee surgery is common and is influenced by the underlying pathology, the type of surgery, and the patient. Knee joint-preserving surgery includes osteotomy, ligament reconstruction, meniscus surgery, and cartilage repair procedures, often used in combination. Knee arthroplasty procedures consist of unicondylar, patellofemoral, and primary or revision total knee prosthesis. In patients with pain after knee joint-preserving surgery, MRI remains the reference standard. After ligament reconstruction, CT can evaluate postoperative tunnel positioning, and bone SPECT/CT can contribute by assessing overloading or biodegradation problems. After meniscal or cartilage surgery, SPECT/CT can be particularly helpful to identify compartment overloading or nonhealing chondral or osteochondral lesions as cause of pain. SPECT/CT arthrography can assess cartilage damage at an early stage due to altered biomechanical forces. After corrective osteotomy of the knee, SPECT/CT can reveal complications such as overloading, nonunion, or patellofemoral problems. After arthroplasty, conventional radiographs lack both sensitivity to detect aseptic loosening and specificity in differentiating aseptic from infectious loosening. Secondly, hardware-induced artifacts still hamper CT and MRI, despite improving and increasingly available metal artifact reduction techniques. Bone scintigraphy is a proven useful adjunct to conventional radiography and MRI to reveal the pain generator and is less hampered by artifacts from metallic implants compared with CT and MRI. Nevertheless, the optimal imaging strategy in evaluating complications after knee arthroplasty is still a matter of debate. Although the evidence of the use of BS SPECT/CT is still limited, it is growing steadily. In particular, recent data on specific uptake patterns in tibial and femoral zones after total knee arthroplasty and the impact of integrating biomechanics into the assessment of SPECT/CT appear promising, but more research is needed.

Synovial Fluid Aspiration Should Not Be Routinely Performed during the Two-Stage Exchange of the Knee

Purpose

Detection of infection persistence during the two-stage exchange of the knee for periprosthetic joint infection is challenging. Synovial fluid culture (SFC) and synovial white blood cell count (SWBCC) before joint reimplantation are widespread diagnostic means for this indication. The sensitivity and specificity of SFC and of SWBCC for infection persistence before planned reimplantation were evaluated.

Methods

94 two-stage exchanges of the knee with synovial fluid aspiration performed after a drug holiday of at least 14 days and before reimplantation or spacer exchange (planned reimplantation) were retrospectively analyzed. Only cases with at least 3 intraoperative samples at planned reimplantation were included. SFC and SWBCC were compared to pathogen detection (SFC_(culture)/SWBCC_(culture)) and to histopathological signs of infection persistence (SFC_(histo)/SWBCC_(histo)) from intraoperative samples at planned reimplantation. For SFC, the sensitivity and specificity were calculated. For SWBCC, the optimal cut-off value with its sensitivity and specificity was calculated with the Youden-Index.

Results

Sensitivity and specificity of SFC_(culture) were 0.0% and 98.9%. Sensitivity and specificity of SFC_(histo) were 3.4% and 100%. The optimal cut-off value for SWBCC_(culture) was 4450 cells/μl with a sensitivity of 50.0% and a specificity of 86.5%. The optimal cut-off value for SWBCC_(histo) was 3250 cells/μl with a sensitivity of 35.7% and a specificity of 92.9%.

Conclusion

The detection of infection persistence remains challenging and a consented approach is lacking. The results do not warrant the routine performance of SFC during the two-stage exchange at the knee. SWBCC can be used to confirm infection persistence at high cut-offs, but they only occur in few patients and are therefore inappropriate for the routine use.

Usefulness of sonication for diagnosing infection in explanted orthopaedic implants

BACKGROUND

Orthopaedic implant infection is a rare but serious complication whose optimal treatment requires an accurate microbiological diagnosis. The objective of this study was to determine whether culturing sonicated explants improved sensitivity compared to culturing standard sonicated soft-tissue samples.

HYPOTHESIS

Cultures of explant sonication fluid are more sensitive than cultures of soft-tissue sonication fluid in patients with implant infection.

METHODS

This single-centre retrospective study included all sonication fluid samples from implants explanted in orthopaedic surgery theatres for any reason. The microbiological results of the implant sonication fluid cultures were compared to those of cultures of sonicated soft-tissue and bone samples taken during the same procedure. The primary evaluation criterion was the difference in microorganisms recovered from explant sonication fluids versus fluid/tissue cultures.

RESULTS

The study included 187 explants removed between September 2009 and June 2015. Of the definite infections, 83% were identified by explant sonication, 86% by fluid/tissue cultures, and 91% by both techniques combined. Explant sonication recovered causative organisms in 10 patients with definite infection but negative fluid/soft tissue cultures. Antibiotic therapy prior to explantation was associated with lower sensitivity of explant sonication (57% vs. 67% for fluid/soft tissue cultures).

CONCLUSION

Explant sonication improved the diagnosis of infection when combined with fluid/soft tissue cultures.

LEVEL OF EVIDENCE

IV, retrospective single-centre study.

Vitamin E Phosphate Coating Stimulates Bone Deposition in Implant-related Infections in a Rat Model

BACKGROUND

Implant-related infections are associated with impaired bone healing and osseointegration. In vitro antiadhesive and antibacterial properties and in vivo antiinflammatory effects protecting against bone loss of various formulations of vitamin E have been demonstrated in animal models. However, to the best of our knowledge, no in vivo studies have demonstrated the synergistic activity of vitamin E in preventing bacterial adhesion to orthopaedic implants, thus supporting the bone-implant integration.

QUESTIONS/PURPOSES

The purpose of this study was to test whether a vitamin E phosphate coating on titanium implants may be able to reduce (1) the bacterial colonization of prosthetic implants and (2) bone resorption and osteomyelitis in a rat model of Staphylococcus aureus-induced implant-related infection.

METHODS

Twelve rats were bilaterally injected in the femurs with S aureus UAMS-1-Xen40 and implanted with uncoated or vitamin E phosphate-coated titanium Kirschner wires without local or systemic antibiotic prophylaxis. Eight rats represented the uninfected control group. A few hours after surgery, two control and three infected animals died as a result of unexpected complications. With the remaining rats, we assessed the presence of bacterial contamination with qualitative bioluminescence imaging and Gram-positive staining and with quantitative bacterial count. Bone changes in terms of resorption and osteomyelitis were quantitatively analyzed through micro-CT (bone mineral density) and semiquantitatively through histologic scoring systems.

RESULTS

Six weeks after implantation, we found only a mild decrease in bacterial count in coated versus uncoated implants (Ti versus controls: mean difference [MD], -3.705; 95% confidence interval [CI], -4.416 to -2.994; p < 0.001; TiVE versus controls: MD, -3.063; 95% CI, -3.672 to -2.454; p < 0.001), whereas micro-CT analysis showed a higher bone mineral density at the knee and femoral metaphysis in the vitamin E-treated group compared with uncoated implants (knee joint: MD, -11.88; 95% CI, -16.100 to -7.664; p < 0.001 and femoral metaphysis: MD, -19.87; 95% CI, -28.82 to -10.93; p < 0.001). We found decreased osteonecrosis (difference between medians, 1.5; 95% CI, 1-2; p < 0.002) in the infected group receiving the vitamin E-coated nails compared with the uncoated nails.

CONCLUSIONS

These preliminary findings indicate that vitamin E phosphate implant coatings can exert a protective effect on bone deposition in a highly contaminated animal model of implant-related infection.

CLINICAL RELEVANCE

The use of vitamin E coatings may open new perspectives for developing coatings that can limit septic loosening of infected implants with bacterial contamination. However, a deeper insight into the mechanism of action and the local release of vitamin E as a coating for orthopaedic implants is required to be used in clinics in the near future. Although this study cannot support the antimicrobial properties of vitamin E, promising results were obtained for bone-implant osseointegration. These preliminary results will require further in vivo investigations to optimize the host response in the presence of antibiotic prophylaxis.