Sonication of removed implants improves microbiological diagnosis of postoperative spinal infections

The identification of low-pathogenic bacteria on removed spinal implants and implications for antimicrobial prophylaxis

Introduction

The role of low-pathogenic bacteria cultured from removed spinal implants is unclear and the efficacy of perioperative single-dose antibiotics against such bacteria remains underexplored.

Research question

This study aims to investigate whether pedicle screw loosening is associated with pathogens and if the choice of perioperative antibiotics can prevent these bacteria.

Methods

A retrospective analysis was conducted on 93 patients with implants removed between 01/01/2018 and 03/31/2020. Patients with both loosened and non-loosened implants were included. The latter group was subdivided into cases where implants were exchanged due to adjacent segment degeneration (ASD) and those with elective implant removal after fracture healing. Bacterial cultures from removed implants were analyzed for resistance profiles against the prophylactic single-shot antibiotics administered during implantation. Patients with acute infection, spondylodiscitis, deep wound infection, empyema, and carbon/polyetheretherketone spinal implants were excluded.

Results

Bacterial isolates were detected in both loosened (41%) and non-loosened (27%) implants (p = 0.23). The most frequently cultivated bacteria were Cutibacterium acnes and Staphylococcus epidermidis. Sensitivity to the administered antibiotics was 75%. While Cutibacterium acnes was entirely sensitive, Staphylococcus epidermidis was completely resistant. Patients with loosened implants without bacteria had a significantly lower bone mineral density (BMD) than patients with implants removed due to ASD. However, patients with loosened implants and positive bacterial cultures had comparable BMD to ASD patients.

Conclusions

The high rate of sensitive Cutibacterium acnes and resistant Staphylococcus epidermidis on removed spinal implants suggests a need to revisit current antimicrobial prophylaxis. Further research is required to determine the clinical significance of low-virulence bacteria, especially on non-loosened implants.

Optimal ultrasonic treatment frequency and duration parameters were used to detect the pathogenic bacteria of orthopedic implant-associated infection by ultrasonic oscillation

INTRUDUCTON

The most accurate method for detecting the pathogen of orthopedic implant-associated infections (OIAIs) is sonication fluid (SF). However, the frequency and duration of ultrasound significantly influence the number and activity of microorganisms. Currently, there is no consensus on the selection of these two parameters. Through this study, the choice of these two parameters is clarified.

METHODS

We established five ultrasonic groups (40kHz/10min, 40kHz/5min, 40 kHz/1min, 20kHz/5min, and 10kHz/5min) based on previous literature. OIAIs models were then developed and applied to ultrasound group treatment. Subsequently, we evaluated the efficiency of bacteria removal by conducting SEM and crystal violet staining. The number of live bacteria in the SF was determined using plate colony count and live/dead bacteria staining.

RESULTS

The results of crystal violet staining revealed that both the 40kHz/5min group and the 40kHz/10min group exhibited a significantly higher bacterial clearance rate compared to the other groups. However, there was no significant difference between the two groups. Additionally, the results of plate colony count and fluorescence staining of live and dead bacteria indicated that the number of live bacteria in the 40kHz/5min SF group was significantly higher than in the other groups.

CONCLUSION

40kHz/5min ultrasound is the most beneficial for the detection of pathogenic bacteria on the surface of orthopedic implants.

Global Trends in Orthopedic Biofilm Research: A Bibliometric Analysis of 1994-2022

Objective

Bibliometric analysis is commonly used to visualize the knowledge foundation, trends, and patterns in a specific scientific field by performing a quantitative evaluation of the relevant literature. The purpose of this study was to perform a bibliometric analysis of recent studies in the field of orthopedic biofilm research and identify its current trends and hotspots.

Methods

Research studies were retrieved from the Web of Science Core Collection and Scopus databases and analyzed in bibliometrix with R package (4.2.2).

Results

A total of 2426 literature were included in the study. Journal of orthopaedic research and Clinical orthopaedics and related research ranked first in terms of productivity and impact, with 57 published articles and 32 h-index, respectively. Trampuz A, Ohio State Univ and the United States ranked as the most productive authors, institutions, and countries. Biofilm formation, role of sonication, biomaterial mechanism and antibiotic loading have been investigated as the trend and hotspots in the field of orthopedic biofilm research.

Conclusion

This study provides a thorough overview of the state of the art of current orthopedic biofilm research and offers valuable insights into recent trends and hotspots in this field.

Practical Guidance for Clinical Microbiology Laboratories: Microbiologic diagnosis of implant-associated infections

SUMMARYImplant-associated infections (IAIs) pose serious threats to patients and can be associated with significant morbidity and mortality. These infections may be difficult to diagnose due, in part, to biofilm formation on device surfaces, and because even when microbes are found, their clinical significance may be unclear. Despite recent advances in laboratory testing, IAIs remain a diagnostic challenge. From a therapeutic standpoint, many IAIs currently require device removal and prolonged courses of antimicrobial therapy to effect a cure. Therefore, making an accurate diagnosis, defining both the presence of infection and the involved microorganisms, is paramount. The sensitivity of standard microbial culture for IAI diagnosis varies depending on the type of IAI, the specimen analyzed, and the culture technique(s) used. Although IAI-specific culture-based diagnostics have been described, the challenge of culture-negative IAIs remains. Given this, molecular assays, including both nucleic acid amplification tests and next-generation sequencing-based assays, have been used. In this review, an overview of these challenging infections is presented, as well as an approach to their diagnosis from a microbiologic perspective.

Comparison of Mid-Infrared Handheld and Benchtop Spectrometers to Detect Staphylococcus epidermidis in Bone Grafts

Bone analyses using mid-infrared spectroscopy are gaining popularity, especially with handheld spectrometers that enable on-site testing as long as the data quality meets standards. In order to diagnose Staphylococcus epidermidis in human bone grafts, this study was carried out to compare the effectiveness of the Agilent 4300 Handheld Fourier-transform infrared with the Perkin Elmer Spectrum 100 attenuated-total-reflectance infrared spectroscopy benchtop instrument. The study analyzed 40 non-infected and 10 infected human bone samples with Staphylococcus epidermidis, collecting reflectance data between 650 cm-1 and 4000 cm-1, with a spectral resolution of 2 cm-1 (Agilent 4300 Handheld) and 0.5 cm-1 (Perkin Elmer Spectrum 100). The acquired spectral information was used for spectral and unsupervised classification, such as a principal component analysis. Both methods yielded significant results when using the recommended settings and data analysis strategies, detecting a loss in bone quality due to the infection. MIR spectroscopy provides a valuable diagnostic tool when there is a tissue shortage and time is of the essence. However, it is essential to conduct further research with larger sample sizes to verify its pros and cons thoroughly.

A prospective study to identify preoperative serum parameters for spinal implant infection detected by sonication fluid culture

PURPOSE

Low-virulent microorganisms identified on pedicle screws by sonication fluid culture (SFC) are an important cause of implant loosening. While sonication of explanted material improves the detection rate, the risk of contamination exists and no standardized diagnostic criteria for chronic low-grade spinal implant-related infection (CLGSII) are stablished. Besides, the role of serum C-reactive protein (CRP) and procalcitonin (PCT) in CLGSII has not been adequately investigated.

METHODS

Blood samples were collected prior to implant removal. To increase sensitivity, the explanted screws were sonicated and processed separately. Patients exhibiting at least one positive SFC were classified in the infection group (loose criteria). To increase specificity, the strict criteria only considered multiple positive SFC (≥ 3 implants and/or ≥ 50% of explanted devices) as meaningful for CLGSII. Factors which might promote implant infection were also recorded.

RESULTS

Thirty-six patients and 200 screws were included. Among them, 18 (50%) patients had any positive SFCs (loose criteria), whereas 11 (31%) patients fulfilled the strict criteria for CLGSII. Higher serum protein level was the most accurate marker for the preoperative detection of CLGSSI, exhibiting an area under the curve of 0.702 (loose criteria) and 0.819 (strict criteria) for the diagnosis of CLGSII. CRP only exhibited a modest accuracy, whereas PCT was not a reliable biomarker. Patient history (spinal trauma, ICU hospitalization and/or previous wound-related complications) increased the likelihood of CLGSII.

CONCLUSION

Markers of systemic inflammation (serum protein level) and patient history should be employed to stratify preoperative risk of CLGSII and decide the best treatment strategy.

Changes of the microbiological spectrum and antibiotic resistance pattern in postoperative spinal implant infections with multiple culture-positive revision surgeries

BACKGROUND CONTEXT

In severe cases of postoperative spinal implant infections (PSII) multiple revision surgeries may be needed. Little is known if changes in the microbiological spectrum and antibiotic resistance pattern occur between revision surgeries.

PURPOSE

Analysis of the microbiological spectrum and antibiotic resistance pattern in patients with multiple revision surgeries for the treatment of PSII STUDY DESIGN: Retrospective database analysis.

PATIENT SAMPLE

Between 01/2011 and 12/2018, 103 patients underwent 248 revision surgeries for the treatment of PSII. Twenty patients (19.4%) who underwent multiple revision surgeries for PSII were included in this study.

OUTCOME MEASURES

Microbiological spectrum, antibiotic resistance pattern.

METHODS

A retrospective analysis of a prospectively maintained single center spine infection database was performed with a minimum follow-up of 3 years. Overall, 20 patients (six male/14 female) underwent 82 revisions for PSII (median 3; range 2-12). There were 55 of 82 (67.1%) procedures with a positive microbiological result. Microbiological analysis was performed on tissue and implant sonication fluid. Changes in microbial spectrum and antibiotic resistance pattern between surgeries were evaluated using Chi-Square and Fisher's exact test.

RESULTS

In total, 74 microorganisms (83.3% gram-positive; 10.8% gram-negative) were identified. The most common microorganisms were Staphylococcus epidermidis (18.9%) and Cutibacterium acnes (18.9%). All S. epidermidis identified were methicillin-resistant (MRSE). Overall, there were 15 of 55 (27.3%) polymicrobial infections. The microbiological spectrum changed in 57.1% (20/35) between the revision stages over the entire PSII period. In 42.9% (15/35) the microorganism persisted between the revision surgeries stages. Overall, changes of the antibiotic resistance pattern were seen in 17.4% (8/46) of the detected microorganisms, comparing index revision and all subsequent re-revisions. Moreover, higher resistance rates were found for moxifloxacin and for ciprofloxacin at first re-revision surgery compared with index PSII revision. Resistances against vancomycin increased from 4.5% (1/23) at index PSII revision to 7.7% (2/26) at first re-revision surgery.

CONCLUSIONS

Changes of the microbiological spectrum and the resistance pattern can occur in patients with severe PSII who require multiple revision surgeries. It is important to consider these findings in the antimicrobial treatment of PSII. The microbiological analysis of intraoperative tissue samples should be performed at every revision procedure for PSII.

The role of biofilm formation in the pathogenesis and antimicrobial susceptibility of Cutibacterium acnes

Cutibacterium acnes (previously known as Propionibacterium acnes) is frequently found on lipid-rich parts of the human skin. While C. acnes is most known for its role in the development and progression of the skin disease acne, it is also involved in many other types of infections, often involving implanted medical devices. C. acnes readily forms biofilms in vitro and there is growing evidence that biofilm formation by this Gram-positive, facultative anaerobic micro-organism plays an important role in vivo and is also involved in treatment failure. In this brief review we present an overview on what is known about C. acnes biofilms (including their role in pathogenesis and reduced susceptibility to antibiotics), discuss model systems that can be used to study these biofilms in vitro and in vivo and give an overview of interspecies interactions occurring in polymicrobial communities containing C. acnes.

Tissue sampling is non-inferior in comparison to sonication in orthopedic revision surgery

BACKGROUND

The aim of this study was to assess the role of sonication fluid cultures in detecting musculoskeletal infections in orthopedic revision surgery in patients suspected of having peri-prosthetic joint infection (PJI), fracture-related infections (FRI), or postoperative spinal implant infections (PSII).

METHODS

Between 2016 and 2019, 149 cases with a data set including sonication fluid cultures and tissue specimen and histological analysis were included. Accuracy of each diagnostic tool as well as the influence of antibiotic therapy was analyzed. Pathogens identified in the sonication cultures and in the associated tissue samples were compared based on the matching of the antibiograms. Therapeutic benefits were then assessed.

RESULTS

Of 149 cases, 43.6% (n = 65) were identified as PJI, 2.7% (n = 4) as FRI, 12.8% (n = 19) as PSII, 6.7% (n = 10) as aseptic non-union, and 34.2% (n = 51) as aseptic implant loosening. The sensitivity and specificity of tissue and synovial specimens showed no significant difference with respect to sonication fluid cultures (sensitivity/specificity: tissue: 68.2%/96.7%; sonication fluid cultures: 60.2%/98.4%). The administration of antibiotics over 14 days prior to microbiological sampling (n = 40) resulted in a lower sensitivity of 42.9% each. Histological analysis showed a sensitivity 86.3% and specificity of 97.4%. In 83.9% (n = 125) of the cases, the results of sonication fluid cultures and tissue specimens were identical. Different microorganisms were found in only four cases. In 17 cases, tissue samples (n = 5) or sonication (n = 12) were false-negatives.

CONCLUSION

Sonication fluid culture showed no additional benefit compared to conventional microbiological diagnostics of tissue and synovial fluid cultures. Preoperative administration of antibiotics had a clearly negative effect on microbiologic test accuracy. In over 83.9% of the cases, sonication fluid and tissue cultures showed identical results. In the other cases, sonication fluid culture did not further contribute to the therapy decision, whereas other factors, such as fistulas, cell counts, or histological analysis, were decisive in determining therapy.

Implant Microbial Colonization Detected by Sonication as a Cause for Spinal Device Failure: A Prospective Study

STUDY DESIGN

A prospective single center observational study.

OBJECTIVES

The aim of this study was to examine the potential role of sonication in the diagnosis of low-grade infections and its association with pedicle screw (PS) loosening, and to describe risk factors and radiological findings associated with spinal implant infection.

SUMMARY OF BACKGROUND DATA

Although PS loosening has mainly been attributed to mechanical overload, implant colonization and biofilm formation have recently been suggested. Culturing of sonication fluid implants is promising in the field of spine instrumentation infection, but little data are available.

METHODS

We prospectively included all patients who were subjected to implant removal. PS loosening was assessed with computed tomography (CT) scan. Different clinical and radiological parameters which could serve as indicators of implant infection were studied.

RESULTS

Thirty-eight patients were included in the study and 11 of them (29%) had a positive sonication result. Patients with spinal implant infection were associated with screw loosening (P = 0.005). Particularly, those screws with a positive microbiological culture showed signs of screw loosening in the preoperative CT scan (P < 0.001). Our results also showed that radiological screw loosening at L1-L3 level, and loosened larger constructs were associated with screw microbial colonization. The most common isolated microorganisms were coagulase-negative staphylococci and Cutibacterium acnes. An implant-based multivariate analysis indicated that screw loosening, the absence of prophylactic cefazolin, ICU hospitalization, screw breakage, and L1-L3 spine level were independent risk factors for implant-associated infection. Our model exhibited a high predictive power with an area under the curve of 0.937.

CONCLUSION

As clinical presentation of deep implant chronic infection is unspecific, consideration of these factors enables preoperative prediction and risk stratification of implant colonization, thus helping patient's management.Level of Evidence: 3.

High Frequency of Low-Virulent Microorganisms Detected by Sonication of Implanted Pulse Generators: So What?

INTRODUCTION

Deep brain stimulation (DBS) has become a well-established treatment modality for a variety of conditions over the last decades. Multiple surgeries are an essential part in the postoperative course of DBS patients if nonrechargeable implanted pulse generators (IPGs) are applied. So far, the rate of subclinical infections in this field is unknown. In this prospective cohort study, we used sonication to evaluate possible microbial colonization of IPGs from replacement surgery.

METHODS

All consecutive patients undergoing IPG replacement between May 1, 2019 and November 15, 2020 were evaluated. The removed hardware was investigated using sonication to detect biofilm-associated bacteria. Demographic and clinical data were analyzed.

RESULTS

A total of 71 patients with a mean (±SD) of 64.5 ± 15.3 years were evaluated. In 23 of these (i.e., 32.4%) patients, a positive sonication culture was found. In total, 25 microorganisms were detected. The most common isolated microorganisms were Cutibacterium acnes (formerly known as Propionibacterium acnes) (68%) and coagulase-negative Staphylococci (28%). Within the follow-up period (5.2 ± 4.3 months), none of the patients developed a clinical manifest infection.

DISCUSSIONS/CONCLUSIONS

Bacterial colonization of IPGs without clinical signs of infection is common but does not lead to manifest infection. Further larger studies are warranted to clarify the impact of low-virulent pathogens in clinically asymptomatic patients.

Surgical revision strategies for postoperative spinal implant infections (PSII)

Over the last years the number of spine surgeries with instrumentation has grown to an indispensable column in the treatment for different pathologies of the spine. A further increase in the incidence of instrumented spinal surgery is expected throughout the next years. Although the implementation and development of new techniques offer faster and more minimal invasive procedures, shortening surgery time, reducing soft tissue injury and revision due to hardware misplacement, the incidence of postoperative spinal implant infections (PSII) remains high. PSII related complications and revision procedures pose an enormous socioeconomic burden. Therefore, standardized strategies and protocols for treatment of PSII are urgently needed. While in former times hardware exchange or hardware removal was common practise in the field of spine surgery this approach has changed over the last years. Although the evidence from clinical studies in the field of PSII is of limited evidence, critical variables for revision strategies of PSII have been identified. Further, to quickly advance in the field of PSII it is certainly important to extrapolate and learn using data regarding the management from other fields of prosthetic joint infections. This should include clinical as well as experimental work in particular in the context of the biofilm, sonication as well as microbiological concepts. Over the last years, at our institution standardized procedures for diagnostic, surgical as well as antimicrobial treatment have been developed, based on the latest recommendations in peer-reviewed literature and our own data. Here we give an overview about surgical revision strategies for PSII and discuss the key points of our standardized protocol.

Clinical presentation and diagnosis of acute postoperative spinal implant infection (PSII)

Acute postoperative infections after surgical interventions on the spinal column are associated with prolonged treatment duration, poor patient outcomes, and a high socioeconomic burden. In the field of joint replacement, guidelines have been established with recommendations for the diagnosis and treatment of such complications, but in spinal surgery there are no definitions permitting distinction between early and late infections and no specific instructions for their management. Various factors increase the risk of acute postoperative infection, including blood transfusions, leakage of cerebrospinal fluid, urinary tract infection, injury of the dura mater, an American Society of Anesthesiologists (ASA) score >2, obesity, diabetes mellitus, and surgical revision. We suggest defining all infections occurring within the first 4 weeks after spinal surgery as early infections. The symptoms are pain at rest, on motion, and/or pressure pain, abnormal warmth, local erythema, circumscribed swelling of the wound, and newly occurring secretion. Together with laboratory parameters such as C-reactive protein (CRP) and leukocytes, a central role is played by imaging in the form of magnetic resonance imaging (MRI), although diagnosis can be hampered by the presence of postoperative fluid collections such as edema or hematoma or by artifacts from an implant. Once an infection has been confirmed, immediate wound revision with debridement and rinsing (sodium hypochlorite) is essential. Intraoperatively it may prove advantageous to use jet lavage and administer vancomycin. We recommend leaving the implant in place in cases of acute postoperative infection. Patients who are not conditional for surgery can first receive antibiotic suppression treatment before surgery at a later date. In such cases initial computed tomography (CT)-guided aspiration or drain insertion can take place.

Implications for diagnosis and treatment of peri-spinal implant infections from experiences in periprosthetic joint infections-a literature comparison and review

Both, periprosthetic joint infection (PJI) and peri-spinal implant infection (PSII) are serious complications occurring in arthroplasty and spine instrumentation with absolute numbers expected to rise in the next years. The currently existing literature data describing the characteristics of PSII are limited when compared to PJI studies. However, both PJI and PSII exhibit similarities concerning pathogenesis, symptoms, diagnosis, treatment and prognosis. This literature review aims at comparing PJI and PSII and to develop implications for diagnosis and treatment of PSII from existing studies about PJI. The review was performed on the basis of a structured PubMed, Cochrane Library, and Medline analysis and existing guidelines, with 99 references being included. The results indicate that specific terms like re-infection should be defined in the context of PSII based on existing definitions of PJI, that in vitro biofilm studies and studies analyzing different prosthesis surfaces in arthroplasty could be used for PSII, and that histopathology as an additional standard tool in PSII diagnosis might be helpful. In addition, the development of a standardized algorithm-based treatment system with antibiotic protocols, including long term suppression, for PSII similar to the ones existing for PJI is necessary.

Antibiotic treatment of postoperative spinal implant infections

Postoperative spinal implant infection (PSII) is a serious complication after spinal surgery. It is associated with increased morbidity and mortality for affected patients as well as significant costs for the healthcare system. Due to the formation of biofilm on foreign material, both diagnosis and treatment of PSII can pose a considerable challenge. Modern treatment protocols allow efficient eradication and good clinical outcomes in the majority of patients. In this article, we review the current antibiotic treatment concepts for PSII including the correct choice of antibiotics and their combination. In cases of late-onset PSII where the implants can be removed, two weeks of intravenous (IV) antibiotics followed by 4 weeks of oral antibiotics seem appropriate. If the implant needs to be retained, a 2-week IV antibiotic treatment should be followed by 10 weeks of oral antibiotic therapy with biofilm activity or, in case of problematic pathogens, a long-term suppression therapy. Initial empiric antibiotic therapy should cover staphylococci, streptococci, enterococci and Gram-negative bacilli as the most common pathogens. Antibiotic adjustments according to the type of pathogen and its antimicrobial susceptibility are essential for successful eradication of infection.

Comprehensive treatment algorithm of postoperative spinal implant infection

Postoperative spinal implant infection (PSII) is a commonly found and serious complication after instrumented spinal surgery. Whereas early-onset PSII usually can be diagnosed by clinical symptoms, the diagnosis of late-onset PSII can be often made only by examination of intraoperatively collected samples. The treatment of PSII consists of surgical and antibiotic therapy schemes. In case of early PSII, the retention of spinal implants is a feasible option, whereas late PSII is usually treated by one-staged exchange of the spinal implants. Radical debridement of surrounding tissue should be performed in any case of PSII. The antibiotic treatment depends on either the implants can be removed or need to be retained or exchanged, respectively. If the causative pathogens are sensitive for biofilm-active antibiotic agents, the duration of antibiotic treatment amounts to 12 weeks with retention of spinal implants. In case of problematic pathogens, the application of antibiotics needs to be prolonged for an individual duration. Antibiotic treatment should always be initiated with an intravenous application for at least 2 weeks.

Ultrasound frequency of sonication applied in microbiological diagnostics has a major impact on viability of bacteria causing PJI

OBJECTIVES

Sonication of explanted prosthesis constitutes an element of microbiological diagnostics. The aim of performing this procedure is to remove biofilm and to increase sensitivity of diagnostics. Ultrasound used in medical purposes are low-frequency and low-intensity. With this wide range of frequency which can be used in sonication process it is necessary to find the golden mean between biofilm dislodging and planktonic bacteria sparing.

MATERIALS AND METHODS

The aim of this study was to determine the least harming low-intensity ultrasound frequency (35 kHz, 40 kHz or 53 kHz) used during sonication process with other parameters constant. Four bacteria species were examined: S. aureus, E. faecalis, E. coli, K. pneumoniae. Number of microbiological studies (n) for each group (g) counted 40 specimens (based on scheme 1 bacteria type - 4 groups, 40 studies each).

RESULTS

A detailed analysis of gathered data was conducted. Based on study findings following conclusions were drawn. Sonication has a significant and negative impact on survival of sonicated planktonic bacteria. Part of bacteria in planktonic state are damaged/killed by ultrasound, which is demonstrated by lower CFU count in sonicated samples versus control group.

CONCLUSIONS

Optimal ultrasound frequencies for sonication of S. aureus, P. aeruginosa and E. coli are 35 kHz and 40 kHz. Ultrasound frequencies used in sonication process (35 kHz, 40 kHz, 53 kHz) of E. coli showed same impact on bacteria survival. It is crucial to perform further assessment of ultrasound parameters on clinical effects of sonication used in PJI diagnostics.

Low sensitivity of histopathological examination of peri-implant tissue samples in diagnosing postoperative spinal implant infection

AIMS

To evaluate the histopathological examination of peri-implant tissue samples as a technique in the diagnosis of postoperative spinal implant infection (PSII).

METHODS

This was a retrospective analysis. Patients who underwent revision spinal surgery at our institution were recruited for this study. PSII was diagnosed by clinical signs, histopathology, and microbiological examination of intraoperatively collected samples. Histopathology was defined as the gold standard. The sensitivity for histopathology was calculated. A total of 47 patients with PSII and at least one microbiological and histopathological sample were included in the study.

RESULTS

PSII occurred in approximately 28% of the study population. Histopathology showed a sensitivity of 51.1% in the diagnosis of PSII. The most commonly found pathogens were Cutibacterium acnes and gram-positive staphylococci.

CONCLUSION

Histopathology has low sensitivity for detecting PSII. In particular, infections caused by low-virulence microorganisms are insufficiently detected by histopathology. Cite this article: Bone Joint J 2020;102-B(7):899-903.

The role of implant sonication in the diagnosis of periprosthetic shoulder infection

BACKGROUND

The aim of this study was to investigate the validity of implant sonication fluid cultures in the diagnosis of shoulder periprosthetic joint infection (PJI) compared with tissue culture.

METHODS

This was a retrospective case-control study analyzing all patients who underwent a revision surgery for any kind of suspected septic or aseptic event due to failed shoulder arthroplasty at our institution between July 2014 and December 2018. The diagnostic validity of implant sonication was analyzed on the basis of the last proposed definition criteria of the International Consensus Meeting and compared with standard tissue cultures.

RESULTS

Of the 72 patients, a total of 28 (38.9%) were classified as infected. Of the 28 infected patients, 20 (71.4%) had an identified organism by tissue cultures, and Cutibacterium acnes was the most commonly isolated pathogen. The sensitivities of sonicate fluid (≥50 CFU/mL) and periprosthetic tissue culture for the diagnosis of periprosthetic shoulder infection were 36% and 61% (P = .016), and the specificities were 97.7% and 100% (P > .99), respectively. If no cutoff value was used in sonication culture, the sensitivity increased to 75% whereas the specificity dropped to 82%. Although there was no significant difference in sensitivity between tissue culture and the no-cutoff sonication fluid culture (61% vs. 75%, P = .125), the specificity of tissue culture was significantly higher (100% vs. 82%, P = .01).

CONCLUSION

Tissue culture showed a higher sensitivity and specificity than implant sonication in the diagnosis of shoulder PJI and should remain the gold standard for microbiological diagnosis of shoulder PJI.