MRI-based artificial intelligence to predict infection following total hip arthroplasty failure.

PURPOSE: To investigate whether artificial intelligence (AI) can differentiate septic from non-septic total hip arthroplasty (THA) failure based on preoperative MRI features. MATERIALS AND METHODS: We included 173 patients (98 females, age: 67 ± 12 years) subjected to first-time THA revision surgery after preoperative pelvis MRI. We divided the patients into a training/validation/internal testing cohort (n = 117) and a temporally independent external-testing cohort (n = 56). MRI features were used to train, validate and test a machine learning algorithm based on support vector machine (SVM) to predict THA infection on the training-internal validation cohort with a nested fivefold validation approach. Machine learning performance was evaluated on independent data from the external-testing cohort. RESULTS: MRI features were significantly more frequently observed in THA infection (P < 0.001), except bone destruction, periarticular soft-tissue mass, and fibrous membrane (P > 0.005). Considering all MRI features in the training/validation/internal-testing cohort, SVM classifier reached 92% sensitivity, 62% specificity, 79% PPV, 83% NPV, 82% accuracy, and 81% AUC in predicting THA infection, with bone edema, extracapsular edema, and synovitis having been the best predictors. After being tested on the external-testing cohort, the classifier showed 92% sensitivity, 79% specificity, 89% PPV, 83% NPV, 88% accuracy, and 89% AUC in predicting THA infection. SVM classifier showed 81% sensitivity, 76% specificity, 66% PPV, 88% NPV, 80% accuracy, and 74% AUC in predicting THA infection in the training/validation/internal-testing cohort based on the only presence of periprosthetic bone marrow edema on MRI, while it showed 68% sensitivity, 89% specificity, 93% PPV, 60% NPV, 75% accuracy, and 79% AUC in the external-testing cohort. CONCLUSION: AI using SVM classifier showed promising results in predicting THA infection based on MRI features. This model might support radiologists in identifying THA infection.

Exploring multielement nanogranular coatings to forestall implant-related infections.

Introduction: As we approach the post-antibiotic era, the development of innovative antimicrobial strategies that carry out their activities through non-specific mechanisms could limit the onset and spread of drug resistance. In this context, the use of nanogranular coatings of multielement nanoparticles (NPs) conjugated to the surface of implantable biomaterials might represent a strategy to reduce the systemic drawbacks by locally confining the NPs effects against either prokaryotic or eukaryotic cells. Methods: In the present study, two new multielement nanogranular coatings combining Ag and Cu with either Ti or Mg were synthesized by a gas phase physical method and tested against pathogens isolated from periprosthetic joint infections to address their potential antimicrobial value and toxicity in an in vitro experimental setting. Results: Overall, Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli displayed a significantly decreased adhesion when cultured on Ti-Ag-Cu and Mg-Ag-Cu coatings compared to uncoated controls, regardless of their antibiotic resistance traits. A dissimilar behavior was observed when Pseudomonas aeruginosa was cultured for 30 and 120 minutes upon the surface of Ti-Ag-Cu and Mg-Ag-Cu-coated discs. Biofilm formation was mainly reduced by the active effect of Mg-Ag-Cu compared to Ti-Ag-Cu and, again, coatings had a milder effect on P. aeruginosa, probably due to its exceptional capability of attachment and matrix production. These data were further confirmed by the evaluation of bacterial colonization on nanoparticle-coated discs through confocal microscopy. Finally, to exclude any cytotoxic effects on eukaryotic cells, the biocompatibility of NPs-coated discs was studied. Results demonstrated a viability of 95.8% and 89.4% of cells cultured in the presence of Ti-Ag-Cu and Mg-Ag-Cu discs, respectively, when compared to negative controls. Conclusion: In conclusion, the present study demonstrated the promising anti-adhesive features of both Ti-Ag-Cu and Mg-Ag-Cu coatings, as well as their action in hampering the biofilm formation, highlighting the safe use of the tested multi-element families of nanoparticles as new strategies against bacterial attachment to the surface of biomedical implants.

Evaluation of Synovial Calprotectin by Using a Lateral Flow Test for the Diagnosis of Prosthetic Joint Infections.

The analysis of synovial fluid is a crucial step in the diagnosis of prosthetic joint infections (PJIs). Recently several studies illustrated the efficacy of synovial calprotectin in supporting the diagnosis of PJI. In this study, synovial calprotectin was analyzed by a commercial stool test to explore whether it might accurately predict PJIs. The synovial fluids of 55 patients were analyzed and calprotectin levels were compared to other synovial biomarkers of PJI. Of the 55 synovial flu-ids, 12 patients were diagnosed with PJI and 43 with an aseptic failure of the implant. Specificity, sensitivity, and AUC of calprotectin resulted in 0.944, 0.80, and 0.852 (95%CI: 0.971-1.00), respectively, with a set threshold of 529.5 µg/g. Calprotectin had a statistically relevant correlation with the synovial leucocyte counts (rs = 0.69, p < 0.001) and the percentage of synovial neutrophils (rs = 0.61, p < 0.001). From this analysis, it can be concluded that synovial calprotectin is a valuable biomarker that correlates with other established indicators of local infection, and the use of a commercial lateral flow stool test could be a cost-effective strategy delivering rapid and reliable results and supporting the diagnostic process of PJI.

The combined evaluation of fibrinogen and D-dimer levels are a helpful tool to exclude periprosthetic knee infection.

This retrospective study was undertaken to (i) define the most appropriate thresholds for serum d-dimer and fibrinogen for differentiating aseptic failure from periprosthetic joint infection (PJI) and (ii) evaluate the predictive value of our d-dimer and fibrinogen threshold compared to previously proposed thresholds. This observational cohort study included consecutive patients who had undergone total knee arthroplasty (TKA) revision between January 2019 and December 2020. International Consensus Meeting diagnostic criteria were used to identify patients affected by the prosthetic infection. Receiver operating characteristic curve analyses assessed the predictive value of the parameters, and the areas under the curves were evaluated. We included 125 patients with a median age of 69 years (53-82) affected by painful TKA. Fifty-seven patients (47%) had PJI. Patients with PJI had higher median d-dimer, fibrinogen, ESR, and CRP when compared to patients believed to be free of PJI. The best threshold values for d-dimer and fibrinogen were 1063 ng/ml (sensitivity 0.72, specificity 0.74) and 420 mg/dl (sensitivity 0.67 and specificity 0.82), respectively. A d-dimer level >1063 ng/ml combined with a fibrinogen level >420 mg/dl had a sensitivity of 0.52, and a specificity of 0.90. We found that an increased d-dimer beyond 1063 ng/ml showed a better predictive value than the previously proposed threshold. The combined determination of d-dimer and fibrinogen displayed high specificity and should be considered an excellent tool to rule out an infection. The accuracy of the proposed cutoffs is more effective than previously reported.

Prediction of Long-Term Recovery From Disability Using Hemoglobin-Based Models: Results From a Cohort of 1,392 Patients Undergoing Spine Surgery.

Hemoglobin and its associated blood values are important laboratory biomarkers that mirror the strength of constitution of patients undergoing spine surgery. Along with the clinical determinants available during the preadmission visit, it is important to explore their potential for predicting clinical success from the patient's perspective in order to make the pre-admission visit more patient-centered. We analyzed data from 1,392 patients with spine deformity, disc disease, or spondylolisthesis enrolled between 2016 and 2019 in our institutional Spine Registry. Patient-reported outcome measure at 17 months after surgery was referred to the Oswestry disability index. High preoperative hemoglobin was found to be the strongest biochemical determinant of clinical success along with high red blood cells count, while low baseline disability, prolonged hospitalization, and long surgical times were associated with poor recovery. The neural network model of these predictors showed a fair diagnostic performance, having an area under the curve of 0.726 and a sensitivity of 86.79%. However, the specificity of the model was 15.15%, thus providing to be unreliable in forecasting poor patient-reported outcomes. In conclusion, preoperative hemoglobin may be one of the key biomarkers on which to build appropriate predictive models of long-term recovery after spine surgery, but it is necessary to include multidimensional variables in the models to increase the reliability at the patient's level.

Exploratory assessment of serological tests to determine antibody titer against SARS-CoV-2: Appropriateness and limits.

BACKGROUND: Serological tests can be used to detect antibodies in the serum of subject's after SARS-CoV-2 infection and vaccination. Currently, variability in antibody titers and the availability of a multiplicity of serological tests have made it necessary to highlight their appropriateness and limitations in various diagnostic settings. METHODS: This study is part of Covidiagnostix, a multicenter project aimed at the assessment of the health technology used in SARS-CoV-2 serological tests. Based on data gained from the analysis of over 5000 subjects, a selected number of serum samples, representative of different diagnostic settings, were analyzed first by qualitative immunoassays (IgA, M, and G MILLIPLEX® SARS-CoV-2 tests based on Luminex® ) to define the immunoglobulins serum composition and subsequently by four serological diagnostic tests (Elecsys Anti-SARS-CoV-2 and Elecsys Anti-SARS-CoV-2 S by Roche, SARS-CoV-2 IgG by Siemens Healthcare, and CHORUS SARS-CoV-2 "NEUTRALIZING" Ab by DIESSE). The first WHO International Standard for SARS-CoV-2 was also analyzed using the same methods. RESULTS: This study evaluated the antibody content and titer of the WHO Standard and serum of subjects with/without previous infection and before/after vaccination for SARS-CoV-2. CONCLUSION: The definition of antibodies in the WHO standard and the analysis of serum samples allowed for the identification of the appropriateness of serological tests in each diagnostic setting, increasing the effectiveness of the resulting laboratory data. Furthermore, we found that it would be optimal to produce new international standards against the S1 domain and RBD of the SARS-CoV-2 spike protein for a more effective serological monitoring of vaccination.

Host Environment Shapes S. aureus Social Behavior as Revealed by Microscopy Pattern Formation and Dynamic Aggregation Analysis.

Understanding how bacteria adapt their social behavior to environmental changes is of crucial importance from both biological and clinical perspectives. Staphylococcus aureus is among the most common infecting agents in orthopedics, but its recalcitrance to the immune system and to antimicrobial treatments in the physiological microenvironment are still poorly understood. By means of optical and confocal microscopy, image pattern analysis, and mathematical modeling, we show that planktonic biofilm-like aggregates and sessile biofilm lifestyles are two co-existing and interacting phases of the same environmentally adaptive developmental process and that they exhibit substantial differences when S. aureus is grown in physiological fluids instead of common lab media. Physicochemical properties of the physiological microenvironment are proposed to be the key determinants of these differences. Besides providing a new tool for biofilm phenotypic analysis, our results suggest new insights into the social behavior of S. aureus in physiological conditions and highlight the inadequacy of commonly used lab media for both biological and clinical studies of bacterial development.

Megaprostheses for the revision of infected hip arthroplasties with severe bone loss.

BACKGROUND: Periprosthetic hip infections with severe proximal femoral bone loss may require the use of limb salvage techniques, but no agreement exists in literature regarding the most effective treatment. Aim of this study is to analyze the infection eradication rate and implant survival at medium-term follow-up in patients treated with megaprostheses for periprosthetic hip infections with severe bone loss. METHODS: Twenty-one consecutive patients were retrospectively reviewed at a mean 64-month follow-up (24-120). Functional and pain scores, microbiological, radiological and intraoperative findings were registered. Kaplan Meier survival analysis and log rank test were used for infection free survival and implant survival analyses. RESULTS: The infection eradication rate was 90.5%, with an infection free survival of 95.2% at 2 years (95%CI 70.7-99.3) and 89.6%(95%CI 64.3-97.3) at 5 years. Only two patients required major implant revisions for aseptic implant loosening. The most frequent complication was dislocation (38.1%). The major revision-free survival of implants was 95.2% (95%CI 70.7-99.3) at 2 years and 89.6% (95%CI 64.3-97.3) at 5 years. The overall implant survival was 83.35% (CI95% 50.7-93.94) at 2 and 5 years. Subgroup analyses (cemented versus cementless MPs, coated versus uncoated MPs) revealed no significant differences at log rank test, but its reliability was limited by the small number of patients included. CONCLUSIONS: Proximal femoral arthroplasty is useful to treat periprosthetic hip infections with severe bone loss, providing good functional results with high infection eradication rates and rare major revisions at medium-term follow-up. No conclusions can be drawn on the role of cement and coatings.

Can the Leukocyte Esterase Strip Test Predict Persistence of Periprosthetic Joint Infection at Second-Stage Reimplantation?

BACKGROUND: We evaluated the reliability of intraoperative assessment of leukocyte esterase (LE) in synovial fluid samples from patients undergoing reimplantation following implant removal and spacer insertion for periprosthetic joint infection (PJI). Our hypothesis was that a positive intraoperative LE test would be a better predictor of persistent infection than either serum C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) or the combination of serum CRP and ESR. METHODS: The records of 76 patients who received a 2-stage exchange for PJI were retrospectively reviewed. Synovial fluid was collected for LE measurement during surgery before arthrotomy in 79 procedures. Receiver operating characteristic curves were generated. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and area under the curve (AUC) of LE, CRP, ESR, and CRP + ESR were calculated. RESULTS: Sensitivity, specificity, positive predictive value, and negative predictive value of the LE assay were 82%, 99%, 90%, and 97%, respectively. Receiver operating characteristic analysis revealed an LE threshold of 1.5 between the first (negative) and the second (positive) level of the ordinal variable, so that a grade starting from 1+ was accurate for a diagnosis of persistent infection (AUC 0.9044). The best thresholds for the CRP and the ESR assay were 8.25 mg/L (82% sensitivity, 84% specificity, AUC 0.8416) and 45 mm/h (55% sensitivity, 87% specificity, AUC 0.7493), respectively. CONCLUSION: The LE strip test proved a reliable tool to diagnose persistence of infection and outperformed the serum CRP and ESR assays. The strip test provides a valuable intraoperative diagnostic during second-stage revision for PJI.

Quantitative serological evaluation as a valuable tool in the COVID-19 vaccination campaign.

OBJECTIVES: After exceptional research efforts, several vaccines were developed against SARS-CoV-2 which sustains the pandemic COVID-19. The Comirnaty vaccine showed high efficacy in clinical trials and was the first to be approved for its distribution to the general population. We evaluated the immune response induced by the first vaccine dose in different sex/age groups and subjects with or without naturally present anti-SARS-CoV-2 antibodies. METHODS: As part of an Italian multicenter project (Covidiagnostix), serum samples from 4,290 health-professionals were serologically tested the day of the first vaccination dose, and 21 days later, using two different instrumentations (Siemens-Healthineers and Roche). RESULTS: In total, 97% of samples showed the presence of specific antibodies 21 days after the vaccination dose; the percentage of non-responders increased with age in both genders. Remarkably, naturally seropositive individuals showed antibody persistence up to 11 months and an exceptionally higher vaccination response compared to subjects never infected by SARS-CoV-2. CONCLUSIONS: This study highlighted the importance of the serological test i) to identify naturally SARS-CoV-2 seropositive individuals and ii) to evaluate the antibody level elicited by the first vaccination dose. Both tests, highlighted differences in the immune response, when subjects were stratified by sex and age, and between naturally seropositive and seronegative subjects. The data obtained show how serological tests could play a crucial role in the triage of the population subjected to the vaccination campaign for COVID-19. The definition of suitable instrumentation-specific thresholds is needed to correctly follow eventually acquired post-vaccination immunity in the general population.

Harmonization of six quantitative SARS-CoV-2 serological assays using sera of vaccinated subjects.

BACKGROUND AND AIMS: Vaccines, to limit SARS-CoV-2 infection, were produced and reliable assays are needed for their evaluation. The WHO produced an International-Standard (WHO-IS) to facilitate the standardization/comparison of serological methods. The WHO-IS, produced in limited amount, was never tested for reproducibility. This study aims at developing a reproducible and accessible working standard (WS) to complement the WHO-IS. MATERIALS AND METHODS: Sera from vaccinated individuals were used to produce the WSs. The WHO-IS, the WSs and single serum samples (n = 48) were tested on 6 quantitative serological devices. Neutralization assays were performed for the 48 samples and compared with their antibody titers. RESULTS: The WS carry an antibody titer 20-fold higher than the WHO-IS. It was reproducible, showed both good linearity and insignificant intra- and inter-laboratory variability. However, the WSs behave differently from the WHO-IS. Analysis of the 48 samples showed that single correlation factors are not sufficient to harmonize results from different assays. Yet, all the devices predict neutralization activity based on the antibody titer. CONCLUSIONS: A reproducible and highly concentrated WS, specific for IgG against SARS-CoV-2 Spike-glycoprotein was produced. Such characteristics make it particularly suited for the harmonization of commercially available assays and the consequent evaluation of post-vaccinated individuals.

A spacer infection by Candida albicans secondary to a Staphylococcus capitis prosthetic joint infection: a case report.

BACKGROUND: Prosthetic joint infection (PJI) is one of the most feared complications following total arthroplasty surgeries. Gram-positive bacteria are the most common microorganisms implicated in PJIs, while infections mediated by fungi only account for 1% of cases. When dealing with PJIs, a two-stage revision arthroplasty is widely used. Briefly, a spacer is introduced until re-implantation of the definitive prosthesis to provide skeleton stabilization while delivering antibiotics in the site of the infection. Sometimes, antimicrobial therapy may fail, but the isolation of a second microorganism from the spacer is uncommon and even less frequent that of a yeast. CASE PRESENTATION: Here is described a case of a 75-year-old woman who underwent two-stage revision surgery of the left hip prosthesis secondary to a Staphylococcus capitis infection, whose spacer was found to be infected by Candida albicans at a later time. Briefly, the patient underwent revision surgery of the hip prosthesis for a suspected PJI. After the debridement of the infected tissue, an antibiotic-loaded spacer was implanted. The microbiological analysis of the periprosthetic tissues and the implant depicted a S. capitis infection that was treated according to the antimicrobial susceptibility profile of the clinical isolate. Three months later, the patient was admitted to the emergency room due to local inflammatory signs. Synovial fluid was sent to the laboratory for culture. No evidence of S. capitis was detected, however, a yeast was identified as Candida albicans. Fifteen days later, the patient was hospitalized for the removal of the infected spacer. Microbiological cultures confirmed the results of the synovial fluid analysis. According to the susceptibility profile, the patient was treated with fluconazole (400 mg/day) for 6 months. Seven months later, the patient underwent second-stage surgery. The microbiological tests on the spacer were all negative. After 12 months of follow-up, the patient has fully recovered and no radiological signs of infection have been detected. CONCLUSIONS: Given the exceptionality of this complication, it is important to report these events to better understand the clinical outcomes after the selected therapeutic options to prevent and forestall the development of either bacterial or fungal spacer infections.

Ultrasound-Guided Periprosthetic Biopsy in Failed Total Hip Arthroplasty: A Novel Approach to Test Infection in Patients With Dry Joints.

BACKGROUND: To diagnose periprosthetic joint infection (PJI) preoperatively, ultrasound-guided joint aspiration (US-JA) may not be performed when effusion is minimal or absent. We aimed to report and investigate the diagnostic performance of ultrasound-guided periprosthetic biopsy (US-PB) of synovial tissue to obtain joint samples in patients without fluid around the implants. METHODS: One-hundred nine patients (55 men; mean age: 68 ± 13 years) with failed total hip arthroplasty (THA) who underwent revision surgery performed preoperative US-JA or US-PB to rule out PJI. RESULTS: Sixty-nine of 109 patients had joint effusion and underwent US-JA, while the remaining 40 with dry joint required US-PB. Thirty-five of 109 patients (32.1%) had PJI, while 74/109 (67.9%) had aseptic THA failure. No immediate complications were observed in both groups. Technical success of US-PB was 100%, as the procedure was carried on as planned in all cases. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of US-JA were 52.2%, 97.8%, 92.3%, 80.3%, and 82.6%, while for US-PB, they were 41.7%, 100%, 100%, 80%, and 82.5%, respectively, with no significant difference (P = .779). Using the final diagnosis as reference standard, we observed a moderate agreement with both US-JA (k = 0.56) and US-PB (k = 0.50). CONCLUSION: We present a novel US-guided technique to biopsy periprosthetic synovial tissue of failed THA to rule out PJI. We found similar diagnostic performance as compared with traditional US-JA. This supports future larger studies on this procedure that might be applied in patients without joint effusion.

Clinical Characteristics of Severe COVID-19 Patients Admitted to an Intensive Care Unit in Lombardy During the Italian Pandemic.

Italy was one of the worst affected European countries during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. More than 50% of Italian cases occurred in the northern region of Lombardy, where the saturation of health services between March and April 2020 forced hospitals to allocate patients according to available resources. Eighteen severe coronavirus disease 2019 (COVID-19) patients were admitted to our hospital needing intensive support. Given the disease fatality, we investigated the patients' characteristics to identify mortality predictors. We counted seven deaths from multiple organ failure, two from septic shock, and two from collapsed lungs. The maximum case fatality was observed in patients who contracted SARS-CoV-2 in hospitals. The fatal outcome was associated with the following baseline characteristics: polymorbidity (OR 2.519, p = 0.048), low body mass index (OR 2.288, p = 0.031), low hemoglobin (OR 3.012, p = 0.046), and antithrombin III (OR 1.172, p = 0.048), along with a worsening of PaO2/FiO2 ratio in the first 72 h after admission (OR 1.067, p = 0.031). The occurrence of co-infections during hospitalization was associated with a longer need for intensive care (B = 4.511, p = 0.001). More information is needed to inform intensive care for patients with severe COVID-19, but our findings would certainly contribute to shed some light on this unpredictable and multifaceted disease.

Superior Osteo-Inductive and Osteo-Conductive Properties of Trabecular Titanium vs. PEEK Scaffolds on Human Mesenchymal Stem Cells: A Proof of Concept for the Use of Fusion Cages.

Fusion cages composed of titanium and its alloys are emerging as valuable alternative to standard polyetheretherketone (PEEK) ones routinely used in cervical and lumbar spine surgery. Aim of this study was to evaluate osteo-inductive and osteo-conductive ability of an innovative trabecular titanium (T-Ti) scaffold on human mesenchymal stem cells (hMSCs), in both absence and presence of biochemical osteogenic stimuli. Same abilities were assessed on PEEK and standard 2D plastic surface, the latter meant as gold-standard for in vitro differentiation studies. hMSCs adhered and colonized both T-Ti and PEEK scaffolds. In absence of osteogenic factors, T-Ti triggered osteogenic induction of MSCs, as demonstrated by alkaline phosphatase activity and calcium deposition increments, while PEEK and standard 2D did not. Addition of osteogenic stimuli reinforced osteogenic differentiation of hMSCs cultured on T-Ti in a significantly higher manner with respect to standard 2D plastic culture surfaces, whereas PEEK almost completely abolished the process. T-Ti driven differentiation towards osteoblasts was confirmed by gene and marker expression analyses, even in absence of osteogenic stimuli. These results clearly indicate superior in vitro osteo-inductive and osteo-conductive capacity of T-Ti compared to PEEK, and make ground for further studies supporting the use of T-Ti cages to improve bone fusion.

COVID-19 in Elderly Patients Surgically Treated for Lower Limbs Fracture.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic outbreak has posed new problems in the context of patients suffering from other diseases. In particular, musculoskeletal sequelae related to the state of debilitation associated with COVID-19 are important to consider in elderly patients undergoing surgery after lower limbs fracture, especially in the post-operative period. The objective of this study was to evaluate whether COVID-19 influenced biochemical parameter, recovery and mortality of surgically treated patients suffering from lower extremity fractures. METHODS: Laboratory and clinical data of 30 patients were extrapolated and analyzed in the pre-operative and post-operative periods. Among these patients, 13 had COVID-19 infection (COVID-19 +), whereas 17 had no signs of COVID-19 infections (COVID-19 -). Long-term clinical and functional outcomes were also analyzed. RESULTS: Lower calcium, slightly higher values of CRP and much higher values of CPK and AST were observed pre-operatively in COVID-19 + patients, who also showed higher prevalence of long-term sequelae than COVID-19 - patients. CONCLUSIONS: COVID-19 affects long-term outcome of elderly patients with lower limb fractures in a multifactorial way. First, the virus directly damages the muscle tissue. Secondly, the lung function impairment worsens the overall performance, making rehabilitation more challenging.

Failed Total Hip Arthroplasty: Diagnostic Performance of Conventional MRI Features and Locoregional Lymphadenopathy to Identify Infected Implants.

BACKGROUND: Very little has been published about the diagnostic performance of MRI in total hip arthroplasty (THA) infection. PURPOSE: To determine the diagnostic performance of conventional MRI features and of new lymph nodal indices to identify infection in patients with failed THA. STUDY TYPE: Retrospective. POPULATION: In all, 119 patients (66 females; age 66.9 ± 12.4 years) with failed THA. FIELD STRENGTH/SEQUENCES: Metal artifact reduction sequence (MARS) protocol including short tau inversion recovery and turbo spin-echo T1 - and T2 -weighted sequences at 1.5T. ASSESSMENT: Patients underwent pelvis MRI prior to failed THA revision. MRIs were reviewed to identify periprosthetic bone destruction, soft-tissue mass, effusion, synovitis, lamellated synovitis, extracapsular edema, fibrous periprosthetic membrane, bone edema, and extracapsular collection/sinus tract. The number and maximum diameter of inguinal, obturator and iliac lymph nodes of the affected hip were assessed and normalized to those of the unaffected hip to calculate the ratio of nodal size (RNS), ratio of node number (RNN), difference of nodal size (DNS), and difference of node number (DNN). STATISTICAL TESTS: The Mann-Whitney U-and chi-square test were used. Diagnostic performance of indices and odds ratios (OR) were calculated. RESULTS: RNS, RNN, DNS, and DNN indices were significantly different (P = 0.000) between infected and noninfected THA, with accuracies ranging from 84.8% (RNS) and 93.1% (RNN). All other MRI features were significantly more prevalent in infected THA (P ≤ 0.002), except bone destruction, periarticular soft-tissue mass, and fibrous membrane (P ≥ 0.031). Sensitivities ranged from 7.9% (soft-tissue mass) to 76.3% (effusion/bone edema), specificity from 45.7% (bone destruction) to 97.5% (synovitis/lamellated synovitis), accuracy from 49.6% (bone destruction) to 81.5% (synovitis), OR from 0.261 (soft-tissue mass) to 35.550 (synovitis). DATA CONCLUSION: Conventional MRI features have limited accuracy to differentiate septic and aseptic THA failure. Lymph nodal indices, particularly those related to nodal number, may represent biomarkers of THA infection. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY STAGE: 2.

Bacterial adhesion on spinal implants: An in vitro study of "hot spots".

Few studies evaluated bacterial colonization of spinal implants from a "topographic" point of view. This lack of knowledge could hinder the development of more effective strategies in the prevention and treatment of postoperative spinal infections. The aim of this in vitro study was the analysis of the adhesion pattern of sessile cells on conventional spinal implants, to identify "hot spots" on implants where bacterial adhesion could be favored. Clinically relevant Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa isolates were grown on commercially available end product spinal implants. To identify sessile cells attached to implant surfaces, confocal laser scan microscopy was used. Different areas from the spinal instrumentations (both Ti and CoCr) were selected for biofilm quantification. Bacterial biofilm was markedly increased in the cut of the rods, both Ti and CoCr, as the uneven surface deriving from the cut might foster cell adhesion. Though not statistically significant, a difference was observed between the rod and the area of the notch, possibly as a consequence of the smoothening effect deriving from the bending of the rod. Finally, the amount of biofilm produced on cobalt-chromium surfaces was always more significant than that formed on titanium surfaces. This study highlights how bacterial adhesion through biofilm formation is favored on the surfaces of higher irregularity and that staphylococci are able to increase sessile biomass on CoCr surfaces. These preliminary results show how surface modifications on the implants may play a key role in bacterial adhesion, opening an exciting field for future research.

In Vitro Evaluation of Gentamicin or Vancomycin Containing Bone Graft Substitute in the Prevention of Orthopedic Implant-Related Infections.

Antibiotic-loaded bone graft substitutes are attractive clinical options and have been used for years either for prophylaxis or therapy for periprosthetic and fracture-related infections. Calcium sulfate and hydroxyapatite can be combined in an injectable and moldable bone graft substitute that provides dead space management with local release of high concentrations of antibiotics in a one-stage approach. With the aim to test preventive strategies against bone infections, a commercial hydroxyapatite/calcium sulfate bone graft substitute containing either gentamicin or vancomycin was tested against Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa, harboring different resistance determinants. The prevention of bacterial colonization and biofilm development by selected microorganisms was investigated along with the capability of the eluted antibiotics to select for antibiotic resistance. The addition of antibiotics drastically affected the ability of the selected strains to adhere to the tested compound. Furthermore, both the antibiotics eluted by the bone graft substitutes were able to negatively impair the biofilm maturation of all the staphylococcal strains. As expected, P. aeruginosa was significantly affected only by the gentamicin containing bone graft substitutes. Finally, the prolonged exposure to antibiotic-containing sulfate/hydroxyapatite discs did not lead to any stable or transient adaptations in either of the tested bacterial strains. No signs of the development of antibiotic resistance were found, which confirms the safety of this strategy for the prevention of infection in orthopedic surgery.

Development, evaluation, and validation of machine learning models for COVID-19 detection based on routine blood tests.

Objectives: The rRT-PCR test, the current gold standard for the detection of coronavirus disease (COVID-19), presents with known shortcomings, such as long turnaround time, potential shortage of reagents, false-negative rates around 15-20%, and expensive equipment. The hematochemical values of routine blood exams could represent a faster and less expensive alternative. Methods: Three different training data set of hematochemical values from 1,624 patients (52% COVID-19 positive), admitted at San Raphael Hospital (OSR) from February to May 2020, were used for developing machine learning (ML) models: the complete OSR dataset (72 features: complete blood count (CBC), biochemical, coagulation, hemogasanalysis and CO-Oxymetry values, age, sex and specific symptoms at triage) and two sub-datasets (COVID-specific and CBC dataset, 32 and 21 features respectively). 58 cases (50% COVID-19 positive) from another hospital, and 54 negative patients collected in 2018 at OSR, were used for internal-external and external validation. Results: We developed five ML models: for the complete OSR dataset, the area under the receiver operating characteristic curve (AUC) for the algorithms ranged from 0.83 to 0.90; for the COVID-specific dataset from 0.83 to 0.87; and for the CBC dataset from 0.74 to 0.86. The validations also achieved good results: respectively, AUC from 0.75 to 0.78; and specificity from 0.92 to 0.96. Conclusions: ML can be applied to blood tests as both an adjunct and alternative method to rRT-PCR for the fast and cost-effective identification of COVID-19-positive patients. This is especially useful in developing countries, or in countries facing an increase in contagions.