Prosthetic joint infection: managing infection in a bionic era

Assessing the impact of silicon nanowires on bacterial transformation and viability of Escherichia coli

We investigated the biomaterial interface between the bacteria Escherichia coli DH5α and silicon nanowire patterned surfaces. We optimised the engineering of silicon nanowire coated surfaces using metal-assisted chemical etching. Using a combination of focussed ion beam scanning electron microscopy, and cell viability and transformation assays, we found that with increasing interfacing force, cell viability decreases, as a result of increasing cell rupture. However, despite this aggressive interfacing regime, a proportion of the bacterial cell population remains viable. We found that the silicon nanowires neither resulted in complete loss of cell viability nor partial membrane disruption and corresponding DNA plasmid transformation. Critically, assay choice was observed to be important, as a reduction-based metabolic reagent was found to yield false-positive results on the silicon nanowire substrate. We discuss the implications of these results for the future design and assessment of bacteria-nanostructure interfacing experiments.

Prosthetic hip infection due to Salmonella enterica serovar Enteritidis

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Prosthetic joint infection (PJI) due to Salmonella spp. is uncommon, with an estimated prevalence of <0.3 % of all PJI.

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Salmonella enterica serovar Enteritidis and Salmonella enterica serovar Typhimurium are the most common isolates causing PJI.

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Risk factors include malignancy, hemoglobinopathies, diabetes mellitus, HIV/AIDS, alcohol dependency and immunosuppressed state.

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PJI due to Salmonella spp. can occur without significant preceding gastrointestinal symptoms of infection.

Prosthetic joint infection (PJI) is a serious complication of prosthetic joint implantation with a prevalence of about 1–2 % of all prosthetic joint surgeries. While Staphylococcus spp. are the most common organisms isolated, Salmonella spp. are a rare cause of PJI (estimated prevalence < 0.3 %). We present a case of a 62-year-old patient with a history of previous joint trauma complicated by osteonecrosis, infection and chronic alcohol abuse with late hematogenous prosthetic hip infection due to Salmonella enterica serovar Enteritidis. PJI due to Salmonella spp. should be considered in the differential diagnosis when a patient has risk factors such as malignancy, hemoglobinopathies, diabetes mellitus, human immunodeficiency virus/acquired immunodeficiency syndrome, alcohol dependency or immunosuppressed state, even without significant preceding gastrointestinal symptoms. Our patient had a few of these risk factors and required surgical debridement in addition to antimicrobials for treatment of his PJI.

Treatment of Prosthetic Joint Infection: Established Patient Relationships May Impact Medical Decision-Making

BACKGROUND

Choosing the intervention for prosthetic joint infections, whether debridement, antibiotics, and implant retention (DAIR), or explant and antibiotic spacer placement, is multifactorial. One characteristic that may influence this decision is a previously established relationship with the patient. We hypothesized that patients receiving their arthroplasty at an outside institution and presenting with infection would be more likely to undergo removal of their implant without an attempt at DAIR compared to patients who underwent primary arthroplasty at the investigating institution.

METHODS

The institutional database was queried for primary total hip and knee arthroplasty infections. Manual review of medical records was performed, excluding patients who did not meet the Musculoskeletal Infection Society definition of infection. Patient demographics, medical comorbidities, presenting infection characteristics, and surgical intervention were collected. Multivariable analysis was performed to determine the independent predictors of treatment.

RESULTS

A total of 270 patients were included for analysis. McPherson score (P < .001) and duration of symptoms (P < .001) were associated with subsequent treatment. Additionally, when controlling for age, gender, symptom duration category, procedure, McPherson score, and American Society of Anesthesiologists category, patients with index procedures at outside hospitals were more likely to undergo implant removal (odds ratio, 36.30; 95% confidence interval, 8.16-161.51; P < .001).

CONCLUSION

Patients receiving their primary arthroplasty at an outside hospital and presenting with infection are more likely to undergo removal of hardware as their initial treatment. To avoid treatment bias, institutional protocols should be implemented to guide the shared decision-making process.

How Many Cultures Are Necessary to Identify Pathogens in the Management of Total Hip and Knee Arthroplasty Infections?

BACKGROUND

Identification of the infecting organism is critical to the successful management of deep prosthetic joint infections about the hip and the knee. However, the number of culture specimens and which culture specimens are best to identify these organisms is unknown.

METHODS

We evaluated 113 consecutive patients with infected total hip and total knee arthroplasties and correlated the type of culture specimen and number of specimens taken during surgery to the likelihood of a positive culture result. From these data, we subsequently developed a model to maximize culture yield at the time of surgical intervention. After exclusions, 74 patients meeting the Musculoskeletal Infection Society criteria were left for final analysis.

RESULTS

From this cohort, 63 of 74 patients had a positive culture result (85%). The odds of a fluid culture result being positive was 35 of 47 (0.75), whereas the likelihood of tissue cultures yielding a positive result was 164 of 245 (0.67; P = .313). The sample designated "best culture" specimen was the only culture with a positive result in 1 of 48 cases in which a best culture was identified. The optimal number of cultures needed to yield a positive test result was 4 (specificity = 0.61 and sensitivity = 0.63). Increasing the number of samples increases sensitivity but reduces specificity.

CONCLUSION

A minimum of 4 tissue cultures from representative areas is necessary to maximize the chance of identifying the infecting organism during management of the infected total hip and total knee arthroplasties. The designation of the best culture specimen for additional testing is arbitrary and may not be clinically efficacious.

"Race for the Surface": Eukaryotic Cells Can Win

With an aging population and the consequent increasing use of medical implants, managing the possible infections arising from implant surgery remains a global challenge. Here, we demonstrate for the first time that a precise nanotopology provides an effective intervention in bacterial cocolonization enabling the proliferation of eukaryotic cells on a substratum surface, preinfected by both live Gram-negative, Pseudomonas aeruginosa, and Gram-positive, Staphylococcus aureus, pathogenic bacteria. The topology of the model black silicon (bSi) substratum not only favors the proliferation of eukaryotic cells but is biocompatible, not triggering an inflammatory response in the host. The attachment behavior and development of filopodia when COS-7 fibroblast cells are placed in contact with the bSi surface are demonstrated in the dynamic study, which is based on the use of real-time sequential confocal imaging. Bactericidal nanotopology may enhance the prospect for further development of inherently responsive antibacterial nanomaterials for bionic applications such as prosthetics and implants.

Complications Following Partial and Total Wrist Arthroplasty: A Single-Center Retrospective Review

PURPOSE

To describe our institution's experience with complications following partial and total wrist arthroplasty (TWA).

METHODS

We performed a retrospective review of 105 wrist surgeries in 100 patients who underwent surgery with prosthetic replacement of the distal radius, the proximal carpus, or both at a single institution. Patient factors including age, sex, body mass index, handedness, underlying disease, and previous injury were recorded. Outcomes focused particularly on postoperative complications and need for revision surgery.

RESULTS

Forty-seven TWAs, 52 distal radius hemiarthroplasties, and 6 proximal carpal hemiarthroplasties were reviewed with a mean follow-up duration of 35 ± 28 months. Overall complication and revision rates were 51% (53 of 105) and 39% (41 of 105), respectively. Postoperative contracture accounted for the largest number of complications needing additional surgery (20%), followed by component failure (15%). Deep infections occurred in 2 TWAs and 1 distal radius hemiarthroplasty and required removal of hardware, antibiotic spacer placement, and a prolonged course of intravenous antibiotics prior to a definitive operation. Of those patients requiring additional surgery, 41% (n = 10) underwent at least 2 procedures, and 10% (n = 4) underwent at least 6 additional surgeries.

CONCLUSIONS

Although TWA and partial wrist arthroplasty are attractive treatment options for the painful arthritic wrist, there remains a noteworthy potential for complications requiring additional surgery. A detailed understanding of these risks is essential for surgeons so that patients may be counseled accordingly and that alternative treatment options may be considered.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.