C-reactive protein misdiagnoses delayed postoperative spinal implant infections in patients with low-virulent microorganisms

MicroRNA expression analysis in peripheral blood and soft-tissue of patients with periprosthetic hip infection

Aims

Current diagnostic tools are not always able to effectively identify periprosthetic joint infections (PJIs). Recent studies suggest that circulating microRNAs (miRNAs) undergo changes under pathological conditions such as infection. The aim of this study was to analyze miRNA expression in hip arthroplasty PJI patients.

Methods

This was a prospective pilot study, including 24 patients divided into three groups, with eight patients each undergoing revision of their hip arthroplasty due to aseptic reasons, and low- and high-grade PJI, respectively. The number of intraoperative samples and the incidence of positive cultures were recorded for each patient. Additionally, venous blood samples and periarticular tissue samples were collected from each patient to determine miRNA expressions between the groups. MiRNA screening was performed by small RNA-sequencing using the miRNA next generation sequencing (NGS) discovery (miND) pipeline.

Results

Overall, several miRNAs in plasma and tissue were identified to be progressively deregulated according to ongoing PJI. When comparing the plasma samples, patients with a high-grade infection showed significantly higher expression levels for hsa-miR-21-3p, hsa-miR-1290, and hsa-miR-4488, and lower expression levels for hsa-miR-130a-3p and hsa-miR-451a compared to the aseptic group. Furthermore, the high-grade group showed a significantly higher regulated expression level of hsa-miR-1260a and lower expression levels for hsa-miR-26a-5p, hsa-miR-26b-5p, hsa-miR-148b-5p, hsa-miR-301a-3p, hsa-miR-451a, and hsa-miR-454-3p compared to the low-grade group. No significant differences were found between the low-grade and aseptic groups. When comparing the tissue samples, the high-grade group showed significantly higher expression levels for 23 different miRNAs and lower expression levels for hsa-miR-2110 and hsa-miR-3200-3p compared to the aseptic group. No significant differences were found in miRNA expression between the high- and low-grade groups, as well as between the low-grade and aseptic groups.

Conclusion

With this prospective pilot study, we were able to identify a circulating miRNA signature correlating with high-grade PJI compared to aseptic patients undergoing hip arthroplasty revision. Our data contribute to establishing miRNA signatures as potential novel diagnostic and prognostic biomarkers for PJI.

The Role of Combined Inflammatory Biomarkers in the Diagnosis of High- and Low-Virulence FRI Among High-Risk Lower Extremity Fractures

Objective

The aim of this study is to evaluate the diagnostic accuracy of infection-related biomarkers in high-risk lower limb injury patients with fracture-related infection (FRI) caused by high-/low-virulence microorganisms.

Methods

This study was a retrospective analysis of patients with high-risk lower extremity fractures (including tibial plateau, calcaneus, and Pilon fractures) who underwent open reduction internal fixation (ORIF) surgery from January 2017 to February 2022. Peripheral blood samples were collected within 24 hours of admission, and the following information was evaluated: gender, age, BMI, smoking, comorbidities, injury information, surgical details, values for serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), as well as neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), and platelet-to-lymphocyte ratio (PLR).

Results

A total of 576 patients receiving lower extremity fracture surgery were included in this study. Fifty-one patients (8.85%) were identified as FRI, and 28 (54.9%) of these 51 cases were further classified as high-virulence group. The median levels of CRP, ESR, NLR, and MLR were significantly higher in the FRI group than in the non-FRI group (p < 0.01). Similarly, the marginally significantly higher levels of CRP and NLR presented in the high-virulence group, compared to the low-virulence group (p < 0.1). The AUC areas of CRP, NLR, and CRP+NLR were 0.826, 0.650, and 0.873, respectively. We calculated the optimal cut-off points for CRP+NLR as diagnostic markers of high-virulent infection was 0.377.

Conclusion

This study showed the incidence of FRI in high-risk lower extremity fractures was 8.9%, and identified preoperative serum biomarkers, including CRP, ESR, NLR, and PLR, as useful tools for assisting in the diagnosis of infection. Additionally, the combination of CRP with NLR played a discriminating clinical role in postoperative infections caused by different virulence.

Level of Evidence

Clinical study.

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.

The role of serum D-Dimer for the diagnosis of periprosthetic shoulder infection

INTRODUCTION

D-Dimer was recently identified as an additional biomarker in the diagnosis of hip and knee periprosthetic joint infection (PJI). Currently, there is only one study in literature dealing with the role of D-Dimer in the diagnosis of shoulder PJI. The purpose of this study was, therefore, to validate the sensitivity and specificity of D-Dimer in detecting shoulder PJI.

MATERIALS AND METHODS

All patients, who underwent septic or aseptic revision shoulder arthroplasty in our institution between November 2018 und March 2021, were analyzed. Our cohort consisted of 30 patients, of that 14 (47%) had a shoulder PJI according the last proposed criteria of the International Consensus Meeting. The diagnostic validity of serum D-Dimer regarding the detection of PJI was analyzed.

RESULTS

The mean D-Dimer level was significantly higher for the patients with shoulder PJI compared to patients with aseptic failure (1.44 ± 1 mg/l vs. 0.76 ± 0.6 mg/l, p = 0.025). Coagulase-negative staphylococci were the most commonly isolated pathogens, in 9/14 patients (64%), followed by Cutibacterium acnes in 5/14 patients (36%). According to the ROC analysis, a serum D-Dimer threshold of 0.75 mg/l had a sensitivity of 86% and a specificity of 56% for detection of a shoulder PJI. The area under curve was 0.74. A serum C-reactive protein (CRP) cutoff of 10 mg/l showed a sensitivity of 69% and a specificity of 88%. When both serum D-Dimer and CRP above the thresholds of 0.75 mg/l and 10 mg/l, respectively, were used to identify a PJI the sensitivity and specificity were 57% and 100%, respectively.

CONCLUSIONS

Serum D-Dimer showed a good sensitivity but a poor specificity for the diagnosis of shoulder PJI. Combination D-Dimer and CRP led to improvement of the specificity, however, at the cost of sensitivity. Thus, combination of both methods may be used as a confirmatory test in the diagnosis of shoulder PJI but not to rule out infection.

LEVEL OF EVIDENCE

Diagnostic level II.

A high prevalence of Cutibacterium acnes infections in scoliosis revision surgery, a diagnostic and therapeutic dilemma

PURPOSE

To investigate if serum inflammatory markers or nuclear imaging can accurately diagnose a chronic spinal instrumentation infection (SII) prior to surgery.

METHODS

All patients who underwent revision of spinal instrumentation after a scoliosis correction between 2017 and 2019, were retrospectively evaluated. The diagnostic accuracy of serum C-reactive protein (CRP) and Erythrocyte Sedimentation Rate (ESR), ¹⁸F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) and Technetium-99m-methylene diphosphonate (99mTc-MDP) 3-phase bone scintigraphy (TPBS) to diagnose infection were studied. Patients with an acute infection or inadequate culture sampling were excluded. SII was diagnosed if ≥ 2 of the same microorganism(s) were isolated from intra-operative tissue cultures.

RESULTS

30 patients were included. The indication for revision surgery was pseudoarthrosis in the majority of patients (n = 15). 22 patients (73%) were diagnosed with SII. In all infected cases, Cutibacterium acnes was isolated, including 5 cases with a polymicrobial infection. The majority of patients had low inflammatory parameters preoperatively. For CRP > 10.0 mg/L, the sensitivity was 9.1% and specificity 100%; for ESR > 30 mm/h, the sensitivity was 9.1% and specificity 100%. The diagnostic accuracy for nuclear imaging was 64% for the FDG-PET/CT and 67% for the TPBS to diagnose infection.

CONCLUSIONS

The prevalence of SII in patients undergoing revision spinal surgery is high, with Cutibacterium acnes as the main pathogen. No diagnostic tests could be identified that could accurately diagnose or exclude SII prior to surgery. Future studies should aim to find more sensitive diagnostic modalities to detect low-grade inflammation.

Clinical relevance of occult infections in spinal pseudarthrosis revision

Background

Occult infections in spinal pseudarthrosis revisions have been reported in the literature, but the relevance of such an infection on patient outcomes is unknown. We aimed to elucidate clinical outcomes and re-revision risks between patients with and without occult infections in spinal revision surgery for pseudarthrosis.

Methods

In this matched case-control study, we identified 128 patients who underwent thoracolumbar revision surgery from 2014–2019 for pseudarthrosis of the spine. Among them, 13 (10.2%) revealed an occult infection (defined by at least two positive intraoperative tissue samples with the same pathogen), and nine of these 13 were available for follow-up. We selected 18 of the 115 controls using a 2:1 fuzzy matching based on fusion length and length of follow-up. The patients were followed up to assess subsequent re-revision surgeries and the following postoperative patient-reported outcome measures (PROMs): overall satisfaction, Oswestry Disability Index, 5-level EQ-5D, and Short Form 36.

Results

Patient characteristics, surgical data, and length of follow-up were equal between both study groups. The rate of re-revision free survival after the initial pseudarthrosis revision surgery was higher in the occult infection group (77.8%) than the non-infectious controls (44.4%), although not significantly (0.22). The total number of re-revision surgeries, including re-re-revisions, was thirteen (in ten patients) in the control and two (in two patients) in the occult infection group (p = 0.08) after a median follow-up of 24 months (range 13-75). Four cases in the control group underwent re-revision for pseudarthrosis compared to none in the infected group. Satisfactory scores were recorded in all PROMs, with similar scores between the two groups.

Conclusions

The presence of an occult infection accompanying spinal pseudarthrosis revision was not inferior to non-infected pseudarthrosis revisions in a matched, small sample size cohort study. This may be explained due to the possibility of targeted treatment of the identified cause of pseudarthrosis.

Postoperative Spinal Implant Infections (PSII)-A Systematic Review: What Do We Know So Far and What is Critical About It?

STUDY DESIGN

Systematic review.

OBJECTIVES

Postoperative spinal implant infections (PSII) are an increasing challenge in the daily clinical routine. This review summarizes existing knowledge in the field of PSII, including definitions, epidemiology, classifications, risk factors, pathogenesis, symptoms, diagnosis, and treatment.

METHODS

A systematic review was performed using a structured PubMed analysis, based on the PRISMA criteria. The search terminology was set as: "spinal implant associated infection OR spinal implant infection OR spinal instrumentation infection OR peri spinal implant infection." PubMed search was limited to the categories randomized controlled trials (RCT), clinical trials, meta-analysis and (systematic) reviews, whereas case reports were excluded. Studies from January 2000 to December 2020 were considered eligible. A total of 572 studies were identified, 82 references included for qualitative synthesis, and 19 for detailed sub analysis (12 meta-analysis, 7 prospective RCT).

RESULTS

Structural problems in the field of PSII were revealed, including (1) limited level of evidence in clinical studies (missing prospective RCT, metanalyzes), (2) small patient numbers, (3) missing standardized definitions, (4) heterogeneity in patient groups, and (5) redundancy in cited literature.

CONCLUSION

Evidence-based knowledge about spinal implant-associated infections is lacking. All involved medical fields should come together to define the term PSII and to combine their approaches toward research, training, and patient care.

The role of serum C-reactive protein in the diagnosis of periprosthetic shoulder infection

INTRODUCTION

There is a paucity of literature regarding serum C-reactive protein (CRP) in the evaluation of a shoulder periprosthetic joint infection (PJI). The purpose of the current study was to establish cutoff values for diagnosing shoulder PJI and evaluate the influence of the type of infecting microorganism and the classification subgroups according to last proposed International Consensus Meeting (ICM) criteria on the CRP level.

MATERIALS AND METHODS

A retrospective analysis of all 136 patients, who underwent septic or aseptic revision shoulder arthroplasty in our institution between January 2010 and December 2019, was performed. Shoulder PJI was defined according to the last proposed definition criteria of the ICM. Serum CRP levels were compared between infected and non-infected cases, between infection subgroups, as well as between different species of infecting microorganisms. A receiver-operating characteristic (ROC) analysis was performed to display sensitivity and specificity of serum CRP level for shoulder PJI.

RESULTS

A total of 52 patients (38%) were classified as infected, 18 meeting the criteria for definitive infection, 26 for probable infection and 8 for possible infection. According to the ROC curve, an optimized serum CRP threshold of 7.2 mg/l had a sensitivity of 69% and specificity of 74% (area under curve = 0.72). Patients with definitive infection group demonstrated significantly higher median serum CRP levels (24.3 mg/l), when compared to probable, possible infection groups and PJI unlikely group (8 mg/l, 8.3 mg/l, 3.6 mg/l, respectively, p < 0.05). The most common isolated microorganism was Cutibacterium acnes in 25 patients (48%) followed by coagulase-negative staphylococci (CNS) in 20 patients (39%). Patients with a PJI caused by high-virulent microorganisms had a significantly higher median serum CRP level compared to patients with PJI caused by low-virulent microorganisms (48 mg/l vs. 11.3 mg/l, p = 0.04).

CONCLUSIONS

Serum CRP showed a low sensitivity and specificity for the diagnosis of shoulder PJI, even applying cutoffs optimized by receiver-operating curve analysis. Low-virulent microorganisms and patients with probable and possible infections are associated with lower CRP levels compared to patients with definitive infection and infections caused by high-virulent microorganisms.

LEVEL OF EVIDENCE

Diagnostic Level III.

Occult infection in pseudarthrosis revision after spinal fusion

BACKGROUND CONTEXT

Pseudarthrosis after attempted spinal fusion is yet not sufficiently understood and presents a surgical challenge. Occult infections are sometimes observed in patients with pseudarthrosis and no inflammatory signs of infection. The prevalence of such occult infection and its association with patient demographics and inflammatory markers are largely unknown.

PURPOSE

To determine the prevalence of unexpected low-grade infection in spinal pseudarthrosis revision surgery, and to evaluate whether such infection is associated with patient demographics and inflammatory markers.

STUDY DESIGN

Retrospective observational study.

PATIENT SAMPLE

One-hundred-and-twenty-eight patients who underwent thoracolumbar revision surgery due to presumed aseptic pseudarthrosis after spinal instrumentation.

OUTCOME MEASURES

Culture-positive infections or noninfectious pseudarthrosis.

METHODS

Samples were routinely taken for microbiological examination from all adults (n=152) who underwent revision surgery for presumed aseptic thoracolumbar pseudarthrosis between 2014 and 2019. A full intraoperative microbiological workup (at least three intraoperative tissue samples) was done for 128 (84%) patients, and these patients were included in further analyses. Patient characteristics, medical history, inflammatory markers, and perioperative data were compared between those with and without microbiologically-confirmed infection based on samples obtained during pseudarthrosis revision.

RESULTS

The microbiological workup confirmed infection in 13 of 128 cases (10.2%). The predominant pathogen was Cutibacterium acnes (46.2%), followed by coagulase-negative staphylococci (38.5%). The presence of infection was associated with the body mass index (30.9±4.7 kg/m² [infected] vs. 28.2±5.6 kg/m² [controls], p=.049), surgery in the thoracolumbar region (46% vs. 18%, p=.019), and a slightly higher serum C-reactive protein level on admission (9.4±8.0 mg/L vs. 5.7±7.1 mg/L, p=.031). Occult infection was not associated with age, sex, prior lumbar surgeries, number of fused lumbar levels, American Society of Anesthesiologist score, Charlson Comorbidity Index, presence of diabetes mellitus, and smoking status.

CONCLUSIONS

Occult infections were found in 10% of patients undergoing pseudarthrosis revision after spinal fusion, even without preoperative clinical suspicion. Occult infection was associated with higher body mass index, fusions including the thoracolumbar junction, and slightly higher C-reactive protein levels. Intraoperative microbiological samples should be routinely obtained to exclude or identify occult infection in all revision surgeries for symptomatic pseudarthrosis of the spine, as this information can be used to guide postoperative antibiotic treatment.

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.

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.

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.

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.