Background. Data regarding the diagnostic value of ultrasound (US)-determined fluid film and joint aspiration prior to revision total hip arthroplasty (THA) for suspected periprosthetic joint infections (PJIs) is limited. This study aimed to analyse (1) the value of US-determined fluid film, (2) characterisation of the pre- and intraoperative microbiological spectrum and resistance patterns and (3) the concordance between preoperative synovial fluid and intraoperative culture results. Methods. We analysed 366 US-examinations from 340 patients prior to revision THA. Selected cases were categorized into clearly infected, non-infected and inconclusive, according to the International Consensus Meeting (ICM) 2018 Criteria. If US-determined fluid film was <1mm, no aspiration was performed based on our institutional standard protocol. Patients were grouped into no-aspiration (144/366;[39.3%]), dry-tap (21/366;[5.7%]) and a successful-tap (201/366;[54.9%]). The microbiological spectrum and antibiotic resistance patterns were determined and differences were compared between pre- and intraoperative results. Results. The absence of US-determined fluid film showed no correlation with the presence of hip PJI. Overall, 29.9% cases of the no-aspiration-group had a confirmed PJI. Discrepancies were found in 43.2% between successful taps and intraoperative cultures. The most prevalent microorganisms in preoperative synovial fluid were Staphylococcus epidermidis (20.9%), Staphylococcus aureus (20.9%) and Enterococcus faecalis (9.3%). The most prevalent microorganisms in intraoperative cultures were Staphylococcus epidermidis, Cutibacterium acnes and other coagulase-negative Staphylococci (14.2%). Additional microorganisms were identified in 43.8% intraoperatively. Staphylococcus aureus was more often detected preoperatively (20.9% vs. 5.8%;P=0.003), and Cutibacterium acnes intraoperatively (2.3% vs. 14.4%;P=0.01). There were no differences between the antibiotic resistance patterns of pre- and intraoperative concordant microorganisms. Conclusion. Absence of US-determined fluid film cannot rule out the presence of hip PJI. US-guided joint aspirations is a well-established technique. However, the preoperative analysis of synovial fluid shows high discrepancies especially in Cutibacterium acnes and other rare gram-positive microorganisms compared to intraoperative cultures

Aim. The effectiveness of mandatory joint aspiration prior to re-implantation in patients with a cement spacer already in place is unclear. The aim of this study was to evaluate the role of culturing articular fluid obtained by joint aspiration prior to re-implantation in patients who underwent a two stage septic revision. Method. A retrospective observational study was conducted, assessing51 patients that underwent a two stage septic hip or knee revision from 2010 to 2017. According to the results of intraoperative cultures, after the first stage revision each patient was treated with an antibiotic protocol for 6–8 weeks. Following two weeks without antibiotics, a culture of synovial fluid was obtained. Synovial fluid was obtained by direct joint aspiration in cases of knee spacers by and by joint aspiration guided by fluoroscopy in the theatre room in cases of hip spacers. Synovial fluid was transferred into a Vacutainer ACD. ®. flask. Samples were processed and analysed in the microbiology laboratory. Gram stains were performed and the sample was subsequently transferred into a BacALERT bottle (bioMérieux, France) and incubated in a BacALERT instrument for seven days. Results of these cultures were recorded and compared with cultures obtained during re-implantation surgery. Results. Of the 51 patients analysed, 9 were excluded because joint aspiration was not performed or the samples were not correctly processed. The remaining 42 patients (21 hip and 21 knee spacers) were included in the final analysis. In 40 cases, the culture of synovial fluid was negative while in the remaining two cases (hip spacers) no analysis was possible due to dry aspiration. In 5 of the patients, two or more intraoperative synovial fluid cultures taken during the re-implantation surgery were positive. Conclusions. Although in theory, synovial fluid culture may provide useful information regarding the infection status of the joint, in our study, we found no evidence to support mandatory joint aspiration prior to re-implantation in patients with a cement spacer in place

Aim. Periprosthetic joint infection (PJI) is nowadays the most important problem leading to failure in primary and revision total knee (TKA) and total hip arthroplasty (THA), therefore accurate diagnosis of PJI is necessary. We evaluated a commercial multiplex PCR system1 for diagnosis of PJI in joint aspiration fluids prior to surgery. Method. A total of 32 patients were included in the study. Twenty-four patients had TKA and eight had THA. Joint aspiration fluids were examined by standard bacteriological procedures. Excess material of joint aspirates was frozen at −20°C until testing by multiplex PCR1. Inclusion criteria were a minimum leucocyte count of 2.000 per ml and at least 60% of polymorphonucleaur neutrophils (PNN) in the joint aspiration fluid. Results. For 21 patients with TKA, both standard bacteriological culture and PCR1 were negative. In these patients the mean leucocyte count in the joint fluid was 15.385/ml with 80% PNN. For three patients culture was negative, but PCR1 was positive. In one patient PCR1 detected Corynebacterium sp. which was considered as contamination as this patient had crystal arthropathy; for the second patient Propionibacterium acnes was detected by PCR1, this patient was treated as having an infection of unknown origin in another hospital. For the third patient PCR1 detected Pseudomonas aeruginosa. This patient was known as having chronic P. aeruginosa infection of his TKA and joint aspiration was done shortly after arrest of antibiotic therapy by ciprofloxacin. The mean leucocyte count in the patients with positive PCR was 61.800/ml with 89% PNN. In three of the eight patients with THA, standard bacterial culture and PCR1 were both negative. The mean leucocyte count in joint aspirates of these patients was 10.087/ml with 77% PNN. In five patients with THA, both culture and PCR1 were positive and concordant. In one case culture and PCR1 detected Staphylococcus aureus, and in the other culture and PCR1 detected P. acnes. In two cases culture grew S. epidermidis and PCR1 detected coagulase negative Staphylococcus. In the fifth patient culture grew C. jeikeium and PCR1 detected Corynebacterium spp. Conclusions. We found concordant results for culture and PCR1 in all eight patients with THA and in 22/24 patients (92%) with TKA. Multiplex PCR1 results are available in 4 hours whereas culture results may demand several days. The commercial multiplex PCR system1 designed for diagnosis of implant and tissue infection can be helpful for the diagnosis of PJI. *Unyvero i60©, Curetis Strasbourg, France

Aim. Synovial fluid investigation is the best alternative to diagnose prosthetic joint infection (PJI) before adequate microbiological/histology sampling during revision surgery. Although accurate preoperative diagnosis is certainly recommended, puncturing every patient before revision arthroplasty raises concerns about safety and feasibility issues especially in difficult to access joint (e.g., hip), that often require OR time and fluoroscopy/ultrasound guidance. Currently there is no clear guidelines regarding optimal indications to perform preoperative joint aspiration to diagnose PJI before revision surgery. The main goal of this study is to determine the accuracy of our institutional criteria using the new European Bone and Joint Infection Society (EBJIS) PJI definition. Method. We retrospectively evaluated every single- or first-stage for presumed aseptic or known infected revision total hip/knee arthroplasty procedures between 2013–2020. Preoperative clinical and laboratory features were systematically scrutinized. Cases with insufficient information for accurate final PJI diagnosis (i.e., no perioperative synovial fluid examination or no multiple cultures including sonication of removed implant) were excluded. Preoperative joint aspiration is recommended in our institution if any of the following criteria are met: 1) elevated CRP and/or ESR; 2) early failure (<2 years) or repeat failure; 3) high clinical suspicion/risk factors are present. Performance of such criteria were compared against final postoperative EBJIS definition PJI diagnosis. Results. A total of 364 revision THAs or TKAs were performed during the study period. After excluding 258 cases with insufficient information, a total of 106 patients were ultimately included. 38 (35,8 %) were classified as confirmed infections, 10 (9.4 %) as likely infected and 58 (54.7%) as infection unlikely. Of those, 37 confirmed infection cases, 9 likely infected cases and 32 infection unlikely cases did have indication for preoperative synovial fluid collection before revision surgery. Institutional criteria showed 95.8 % Sensitivity, 44.83 % Specificity, 92.9 % Negative Predictive Value (NPV) and 59 % Positive Predictive Value (PPV). Conclusions. Sensitivity and NPV of the aforementioned institutional criteria are very high even with the use of the more sensitive EBJIS PJI definition. As such they seem to be a valid alternative in selecting patients that should be punctured before revision arthroplasty. They identify the vast majority of infected patients while saving a significant number of patients from unnecessary procedures

Acute septic arthritis of the knee may be a challenging diagnosis in the emergency department and must always be excluded in any patient with knee pain and local or systemic signs of infection. Arthrocentesis of the suspected knee is mandatory, since the analysis of the synovial fluid gives useful information like the white blood cell count (WBC)/mm3 or the polymorphonuclear cell percentage (PMP). These parameters will help the clinician to make the decision to drain the joint in the operation room, without having to wait for the culture or Gram stain, which may take several days to be available. The classical cutoff of 50,000 WBC/mm3 with more than 90% of PMP may fail to include all the septic arthritis of the knee, since significant variation have been described in recent years. The aim of this study was to evaluate the accuracy of WBC/mm3 and PMP in the synovial fluid in the diagnosis of acute septic arthritis of the knee. We reviewed the clinical data of patients diagnosed with acute septic arthritis of the knee admitted in our center between January 2010 and December 2014, specifically the WBC/mm3 and the PMP of the synovial joint fluid. The criteria for diagnosis of an acute septic arthritis of the knee was report of purulent material when arhtrotomy or arthroscopy was performed or a positive culture of the joint fluid. The statistical evaluation of the results was performed using Student's t-test. 48 patients matched the inclusion criteria. The mean WBC/mm3 was 44.333 (14.610–182.640) and the mean PMP was 91,89% (86,4%–98,1%). 28 patients (58,33%) had a WBC/mm3 below 50.000 and 44 patients (91,67%) had a PMP above 90%, both with no statistical significance. Knee arthrocentesis is mandatory in every patient suspected to have an acute knee pyoarthrosis, since the joint fluid analysis may show several abnormal findings. Our results show that a considerable number of patients may show a relatively low WBC/mm3 in the joint fluid in the presence of a knee pyoarthrosis. The PMP may be a better criteria, but again failed to achieve statistical significance, probably because of the low number of patients. The synovial fluid analysis alone is probably misleading in the diagnosis of an acute septic arthritis of the knee if the clinician is guided by the classical guidelines. The physical examination, medical history, laboratory and imagiologic tests are all key elements in this challenging diagnosis

Aim. Preoperative joint aspiration cultures (PJACs) are of great value in diagnosing prosthetic joint infections (PJIs). Studies investigating the predictive value of PJACs to identify causative pathogens in PJI, which is off course relevant for the correct initiation of antimicrobial treatment, are limited. The objective of this study was to investigate whether the PJACs are in agreement with causative pathogens in PJIs. Method. A retrospective monocentric study was conducted at the 40-bed orthopedics department of a tertiary centre. Medical files of patients with proven prosthetic knee or hip infection with PJACs from maximum 6 months prior to the first stage of a two-stage revision admitted between March 2010 and December 2014 were evaluated. A proven PJI was defined as at least two positive preoperative or intraoperative cultures, the presence of purulent synovial fluid or purulence at the implant site or surrounding the prosthesis without other identifiable causes, the presence of acute inflammation upon histopathological examination of the periprosthetic tissue at the time of surgery or the presence of a sinus tract communicating with the prosthesis. In order to identify the causative pathogen(s) per patient, a multidisciplinary team, consisting out of a microbiologist, a septic orthopedic surgeon, two infectious diseases specialists and two clinical pharmacists, assessed the relevance of pathogens cultured in the PJACs and intraoperative deep samples based on the current 2012 IDSA guidelines. Per patient, agreement of PJACs corresponding to the retained causative pathogen(s) was investigated in two ways: 1) on species level and 2) on Gram stain or fungi level. Results. Forty-six patients (66 ± 10 years; 26 males; 23 knee and 23 hip; 25 first revisions and 21 with multiple revisions) were included. PJACs remained sterile in seven patients. In 25 of 46 patients (54%) there was agreement in terms of causative pathogen species. In 39 of 46 patients (85%), there was agreement in terms of Gram staining or fungi results. In the other 7 patients, PJACs remained sterile, but with positive intraoperative culture results. Conclusions. Only half of PJAC results corresponded to the retained causative pathogens. Therefore, PJACs should not be used to initiate directed antimicrobial therapy; directed therapy should only be instituted when also intraoperatieve cultures are known. Initially, a (combination of) broad spectrum agent(s) should be preferred. Also preliminary narrowing of the spectrum can be implemented based on the Gram staining or fungi results of PJACs, as was seen in our study

YouTube is one of the main sources for learning clinical skills. This study aims to assess the educational outcomes of medical students from self-directed learning about knee arthrocentesis through searching and using YouTube videos in comparison to traditional supervisor-led sessions.

Seventy-one medical students were randomly assigned in three groups. Group A had a classic supervisor-led clinical session, where the supervisor demonstrated the procedure. Group B students were provided with links to YouTube videos of knee arthrocentesis that were deemed of high educational quality, while group C searched and learned from any YouTube video they found appropriate based on the learning objectives provided. The students' performance pre- and post-feedback was examined using a checklist that was based on the guidelines of the American Academy of Family Physicians on knee arthrocentesis.

Pre-feedback, statistically significant higher mean scores for group A were noted in identification of an appropriate puncture site (p = 0.015), puncture site sterilization (p = 0.046), wearing sterile gloves (p < 0 .001), and direction of needle insertion (p < 0.001). The overall mean scores before feedback for group A, group B and group C were 17.9 ± 1.9, 14.9 ± 2 and 15.4 ± 1.8, respectively (p < 0 .001). None of these scores was below 60% of the total possible score (total score = 21). The overall mean scores after feedback for group A, group B and group C were 21, 20.9 ± 0.3 and 21, respectively (p = 0.037).

Without appropriate feedback to the learners from an instructor, YouTube videos cannot replace traditional supervisor-led sessions in learning knee arthrocentesis.

Aim. The diagnosis of septic arthritis mostly relies on clinical examination, several blood parameters including white blood cell count, C-reactive protein, sedimentation, and the analysis of the joint aspiration. However, the diagnosis can be difficult when the symptoms are vague and the information obtained from laboratory might be insufficient for definitive diagnosis. This study aimed to evaluate several ratios obtained from routine blood tests for a possible use in the diagnosis of septic arthritis. Method. The adult patients who were operated in our clinic due to septic arthritis between 2014–2020 were identified and retrospectively evaluated. The patients with any blood disorders or missing file information were excluded. A total of 36 patients were found to be eligible for inclusion. The control group included 40 patients without any sign of infection who underwent total knee arthroplasty due to knee osteoarthritis. Preoperative blood tests of each patients were examined. In addition to CRP and sedimentation values, neutrophil-lymphocyte, monocyte-lymphocyte, platelet-lymphocyte, and platelet count-mean platelet volume were calculated and receiving operating characteristics (ROC) curve analysis was made to determine the sensitivity, specificity and area under curve (AUC) values of these parameters. Results. The distribution of affected joint in septic arthritis group was as follow; 22 knees, 6 hips, 4 shoulders, 2 elbows, 1 wrist and 1 ankle. The cultures of joint aspiration yielded positive result in 19 patients while the cultures were negative in 17 patients. All of the analyzed parameters were significantly different between the groups (p<0.001). ROC curve analysis results are given in detail, in Table 1 and Figure 1. The AUC value was 97.3 when only CRP and sedimentation values were used but increased to 98.6 when neutrophile/ lymphocyte ratio was added and increased to 100 when all analyzed parameters were included. Conclusions. The analyzed parameters were found to increase the overall sensitivity and specificity when used together with acute phase reactants. However, when evaluated separately, CRP and sedimentation were still found as the most valuable parameters in the diagnosis of septic arthritis. In the diagnosis of septic arthritis, 35 mm/hr cut-off value for sedimentation and 10 mg/L cut-off value for CRP were found more sensitive and specific compared to standard laboratory cut-off values of 20 mm/hr and 5 mg/L. For any tables or figures, please contact the authors directly

Aim. Synovial fluid D-lactate may be useful for diagnosing septic arthritis (SA) as this biomarker is almost exclusively produced by bacteria. We evaluated the performance of synovial fluid D-lactate and determined its optimal cut-off value for diagnosing SA. Method. Consecutive patients with suspicion of septic arthritis were prospectively included. They underwent joint aspiration and synovial fluid was collected for culture, leukocyte count and D-lactate concentration (by spectrophotometry). Youden's J statistic was used for determining optimal D-lactate cut-off value on the receiver operating characteristic (ROC) curve by maximizing sensitivity and specificity. Results. A total of 155 patients were included. Using institutional criteria, 21 patients (14%) were diagnosed with SA and 134 (86%) patients with aseptic arthropathy, out of which 43 (27%) had osteoarthrosis, 80 (52%) had rheumatic arthropathy and 11 (7%) reactive arthritis. The optimal cut-off of synovial fluid D-lactate to differentiate SA from aseptic cases was 0,035 mmol/l. Synovial fluid D-lactate had a sensitivity 90% (95% CI: 70–99%) and specificity 87% (95% CI: 80–92%) compared to leukocyte count with sensitivity 81% (95% CI: 60–95%) and specificity 83% (95% CI: 76–90%). Culture was positive in only 17 (80%) out of 21 patients with SA. Conclusions. The synovial fluid D-lactate showed high sensitivity and specificity for diagnosis of SA which was higher than the current gold standard of diagnosis (culture and leukocyte count). The high sensitivity makes this biomarker useful as a point-of-care screening test for SA

Aim. The prevalence of unexpected positive cultures (UPC) in aseptic revision surgery of the joint with a prior septic revision procedure in the same joint remain unknown. The purpose of this study was to determine the prevalence of UPC in aseptic revisions performed in patients with a previous septic revision in the same joint. As secondary outcome measure, we explore possible risk factors associated with UPC and the re-revision rates. Method. This retrospective single-center study includes all patients between January 2016 and October 2018 with an aseptic revision total hip or knee arthroplasty procedure with a prior septic revision in the same joint. Patients with less than three microbiology samples, without joint aspiration or with aseptic revision surgery performed <3 weeks after a septic revision were excluded. UPC was defined as a single positive culture in a revision that the surgeon had classified as aseptic according to the 2018 International Consensus Meeting. Results. A total of 139 revision total hip/knee arthroplasties in patients with a previous septic revision were performed during the study period. After excluding 47 cases with insufficient information, a total of 92 patients were recruited for final analysis. The patient cohort consist of 52 males and 40 females with a mean age of 70 years (±10.6). There were 66 (71.7%) hips and 26 (28.3%) knees. The mean time between the septic and the aseptic revision was 83 months (±89). The two main causes for the aseptic revision were aseptic loosening (n=57, 62%) followed by instability (n=21, 22.9%). We identified 11 (12%) UPC in the entire cohort, while in 3 cases there was a concordance of the germ compared to the previous septic surgery. There were no differences for the presence of UPC between hips and knees (p=0.282), diabetes (p=0.701), immunosuppression (p= 0.252), previous one-stage or two-stages septic revision (p=0.316), or between the causes for the aseptic revision ((p=0.429). There was no correlation between the UPC and time after the septic revision (p=0.773). Conclusions. The prevalence of UPC in this specific group was similar to those reported in the literature for aseptic revisons. More studies, regarding this patient group are necessitated to better understand and more securely interprete the results in those high-risk aseptic revisions

The diagnosis of infection following shoulder arthroplasty is notoriously difficult. The prevalence of prosthetic shoulder infection after arthroplasty ranges from 3.9 – 15.4% and the most common infective organism is Cutibacterium acnes. Current preoperative diagnostic tests fail to provide a reliable means of diagnosis including WBC, ESR, CRP and joint aspiration. Fluoroscopic-guided percutaneous synovial biopsy (PSB) has previously been reported in the context of a pilot study and demonstrated promising results. The purpose of this study was to determine the diagnostic accuracy of percutaneous synovial biopsy compared with open culture results (gold standard). This was a multicenter prospective cohort study involving four sites and 98 patients who underwent revision shoulder arthroplasty. The cohort was 60% female with a mean age was 65 years (range 36-83 years). Enrollment occurred between June 2014 and November 2021. Pre-operative fluoroscopy-guided synovial biopsies were carried out by musculoskeletal radiologists prior to revision surgery. A minimum of five synovial capsular tissue biopsies were obtained from five separate regions in the shoulder. Revision shoulder arthroplasty was performed by fellowship-trained shoulder surgeons. Intraoperative tissue samples were taken from five regions of the joint capsule during revision surgery. Of 98 patients who underwent revision surgery, 71 patients underwent both the synovial biopsy and open biopsy at time of revision surgery. Nineteen percent had positive infection based on PSB, and 22% had confirmed culture positive infections based on intra-operative tissue sampling. The diagnostic accuracy of PSB compared with open biopsy results were as follows: sensitivity 0.37 (95%CI 0.13-0.61), specificity 0.81 (95%CI 0.7-0.91), positive predictive value 0.37 (95%CI 0.13 – 0.61), negative predictive value 0.81 (95%CI 0.70-0.91), positive likelihood ratio 1.98 and negative likelihood ratio 0.77. A patient with a positive pre-operative PSB undergoing revision surgery had an 37% probability of having true positive infection. A patient with a negative pre-operative PSB has an 81% chance of being infection-free. PSB appears to be of value mainly in ruling out the presence of peri-prosthetic infection. However, poor likelihood ratios suggest that other ancillary tests are required in the pre-operative workup of the potentially infected patient

Aims. The aim of this study was to assess the incidence the microbiological spectrum and clinical outcome of hip and knee revision arthroplasties with unexpected-positive-intraoperative-cultures (UPIC) at a single center with minimum follow up of 2 years. Methods. We retrospectively analyzed our prospectively maintained institutional arthroplasty registry. Between 2011 and 2020 we performed presumably aseptic rTHA (n=939) and rTKA (n= 1,058). Clinical outcome, re-revision rates and causes as well as the microbiological spectrum were evaluated. Results. In total, 219/939 (23.3%) rTHA and 114/ 1,058 (10.8%) rTKA had a UPIC (p<0.001). Single positive intraoperative cultures were found in 173/219 (78.9%) in rTHA and 99/114 (86.8%) in rTKA, whereas 46/219 (21.0%) rTHA and 15/114 (13.2%) rTKA had positive results in ≥2 intraoperative cultures. A total of 390 microorganisms were found among the 333 cases. Staphylococcus epidermidis 30.9%, CoNS (21.9%), Cutibacterium acnes 21.1%, and Bacillus spp. 7.3% were the most common microorganisms. Overall, detected microorganisms showed high sensitivity to daptomycin (96.6%), vancomycin (97.3%) and linezolid (98.0%). After a minimum follow up of 2 years (rTHA 1,470 (735; 3,738) days; rTKA 1,474 (749; 4,055) days). During the 2-year follow-up, 8 patients died and 5 were lost to follow-up. There were 54/219 (24.7%) re-revision in rTHa and 20/114 (17.5%) in rTKA. Overall, there were 23 (10.5%) septic re-rTHA and 9 (7.9%) septic re-rTKA as well as 31 (14.2%) aseptic re-rTHA and 11 (9.6%) aseptic re-rTKA. Patients with previous septic revisions bevor UPIC procedure showed a significant higher risk for septic re-revision (p<0.05). Moreover, there were less septic re-revisions after single culture positive UPIC (rTHA: 16/173 (9.2%); rTKA 6/99 (6.1%)) compared to ≥2 positive intraoperative cultures UPIC (rTHA: 7/46 (15.2%); rTKA 3/15 (20.0%)). The most common reason for re-revision in the rTHA-group was aseptic loosening of the cup (34.2%) or of the stem (23.3%), dislocation (18.3%) and periprosthetic-fractures (7.8%). In the rTKA-group it was aseptic loosening (40.4%), instability (24.6%) and secondary patella resurfacing (7.9%). There was a higher septic re-revision rate in consecutive revisions than in planned revisions 17.3% vs. 8.5% in the rTHA-group and 14.3% vs. 7.5% in the rTKA-group, p<0.001. Conclusion. UPICs are common in rTJA. The rate was higher in hips which may partly explained by the easier pre op joint aspiration in the knee. UPIC may lead to an increase in subsequent re-revisions

Aim. To evaluate the analytical performance of synovial fluid D-lactate test for the diagnosis of PJI. Method. Consecutive patients undergoing diagnostic joint aspiration of prosthetic joint were prospectively included. PJI was diagnosed according to the proposed European Bone and Joint Infection Society (EBJIS) definition criteria. Synovial fluid was collected for culture, D-lactate measurement (by spectrophotometry, λ = 570 nm) and leukocyte count and differential (by flow cytometry). The receiver operating characteristic (ROC) analysis was performed to assess the diagnostic performance of D-lactate and leukocyte count. Results. Diagnostic joint aspiration was performed in 224 patients with prosthetic joints. PJI was diagnosed in 87 patients (39%). The optimal D-lactate cut-off value for diagnosing PJI was 1.2 mmol/l. The sensitivity of synovial fluid D-lactate was 97.7%, specificity 83.9%, whereas the sensitivity of synovial fluid leukocyte count was 87.5% with specificity 95.7%. Concentration of SF D-lactate was significantly higher in patients with PJI compared to aseptic loosening of prosthesis (median (range)) 2.33 (0.99–3.36) vs 0.77 (0.01–2.4), p<0.0001. We found positive correlation between D-lactate and erythrocytes in synovial fluid sample in the aseptic group (ρ = 0.339, p< 0.01). Conclusions. The synovial fluid D-lactate showed a good diagnostic performance for the diagnosis of PJI, which was comparable to the synovial fluid leukocyte count. Currently available (UV)-based method for detection of D-lactate showed low specificity (84%) due to influence of hemoglobin with the similar absorbance wavelengths (λ = 540 nm). More specific high-performance methods such as electro-chemical sensing system or lateral flow immunochromatographic assays should be implemented

Joint aspiration is a useful tool during preoperative workup in suspected periprosthetic infection. The aim of this study was to review efficacy of joint aspiration in our unit and compare results with the published literature. We undertook a retrospective review of 153 consecutive patients who underwent joint aspirations for suspected periprosthetic infection between 03/2011 and 10/2012 who were identified from the hospital electronic database. As per protocol, joint fluid was sent in an EDTA tube for cell count, Paediatric blood culture bottle and the remainder in a specimen pot. 105 (69%) were TKRs and 48 (31%) were THRs. Intraoperative samples were sent as per protocol in only 40 (26%) cases. The hit rate of positive cultures was 11/153 (7%) and specimens sent in paediatric culture bottles identified more positives than if it was omitted (10.5 Vs 5.5%). In conclusion, the hit rate of positive cultures is low in this study compared to the literature (7% Vs 33%) and this is likely due to blanket aspiration of all patients who are undergoing revision. In addition, specimens sent in paediatric culture bottles seem to identify more positives. We recommend cases are selected for aspiration according to AAOS guidelines

Aim. Alpha-defensin was recently introduced as a new biomarker having a very high accuracy to rule out periprosthetic joint infection (PJI). A new rapid lateral flow version of the Alpha-defensin test was developed and introduced to detect high levels of Alpha-defensin in synovial fluid quickly and with ease. We conducted a single-centre prospective clinical study to compare the results of the Alpha-defensin rapid test* against the conventional diagnostics according to MSIS criteria. Method. A total of 223 consecutive patients with painful total hip or knee arthroplasty were enrolled into the study. In all patients, blood C-reactive protein was measured and joint aspirations were performed. From the synovial fluid a leukocyte cell count with granulocyte percentage, microbiology cultures and Leukocyte Esterase tests were carried out according to the recommendation of MSIS for diagnosing PJI. At the same time, the Lateral Flow Test* was performed from the aspirate. 191 subjects with 195 joint aspirations (96 hips, 99 knees) were included in final clinical and statistical evaluation. We had 119 joints with an aseptic revision and 76 joints with PJI. Results. After statistical analysis the overall sensitivity of the Lateral Flow Test* was 92.1% (95% confidence interval [CI], 83.6% to 97.1%), the specificity was 100% (95% CI, 97.0% to 100%), the positive predictive value was 100% (95% CI, 94.9% to 100%), and the negative predictive value was 95.2% (95% CI, 89.9% to 98.2%). The overall accuracy of the Lateral Flow Test* was 96.9% (189 of 195, 95% CI, 93.4% to 98.9%). Conclusions. Our results suggest that the PJI test* has a very high accuracy in diagnosing infected THA and TKA. Though the Lateral Flow Test* does not provide information on the identity of the infectious pathogen, the test does have an important role in recognizing PJI early and enables surgeons to start proper therapy without delay. *Synovasure®

Aim. According to Tsukuyama classification, late acute hematogenous prosthesis joint infections (PJI) should be treated with debridement and implant retention (DAIR). We report here a recurrent Salmonella Dublin hip prosthesis infection. Through this case, we show how a recurrence of chronic PJI may have an acute clinical presentation leading to an inadequate surgical treatment. Method. Case report. On May 2011, a 74-year-old woman with bilateral hip prostheses (implanted in 1998 (right) and 2001 (left)), was admitted to intensive care for sepsis and pain of her left hip. Blood cultures and a joint aspiration of the left hip yielded pure cultures of S.Dublin. The patient had a recent history of febrile diarrhea after consuming dubious meat. The patient underwent DAIR followed by a six-week antibiotherapy. Three years later, she presented to the emergency room for an acute onset febrile PJI of the right hip. The patient underwent DAIR of the right hip. Blood cultures, joint aspiration fluid, and all intraoperative periprosthetic tissue samples yielded S.Dublin. Colonoscopy and abdomen ultrasound were negative. The patient received two weeks of intravenous combined antibiotherapy followed by oral antibiotics for further 10 weeks. Six weeks post operatively, the surgical wound was healed and the patient walked normally. One year later, the patient was referred by her primary care practitioner for night fevers without local signs or dysfunction of her prostheses. Radioleucoscintigraphy showed right hip inflammation. Bilateral hip biopsies were nevertheless performed, yet S. Dublin was recovered solely from the right hip biopsy. A one-stage exchange of the right hip was performed. All intraoperative periprosthetic tissue samples yielded S.Dublin. A six-week-combined antibiotherapy was undertaken. One year later, the patient appeared free of infection and walked normally. Results. Whole-genome sequencing was carried out on the three patient's strains (2011/2014/2015). Their genomes differed by only six SNPs, suggesting that they derived from a single “infecting” strain. Conclusions. This is the first report of recurrent S.Dublin PJI proven by whole genome sequencing. In the absence of detectable gallbladder and/or intestinal carriage, it is most likely that S. Dublin was able to persist at the surface of prosthesis, leading to a chronic disease with recurrences occurring years after the initial episode. These recurrences were associated with a clinical acute onset of the infection, inducing an inadequate surgical treatment at the first time. A better knowledge of possible acutisation of chronic PJI by orthopedic surgeons may improve surgical management of these infections

Topically applied vancomycin powder has been used to decrease surgical site infection rates in spinal surgeries, however, randomized controlled trials in total joint arthroplasty are lacking. Application of vancomycin powder topically in the surgical site has theoretical benefit including high local concentration. In this study, we aimed to determine whether intra-operative topical antibiotics are safe and effective as IV antibiotics in preventing post-surgical site infections. The trial was a randomized controlled, double blind, non-inferiority study. All patients received pre-operative IV antibiotics (cefazolin or vancomycin) within 60 minutes of skin incision. The controlled group received two doses of post-operative IV antibiotics (two grams cefazolin or one gram vancomycin if cefazolin allergy). In the treatment group, the orthopaedic surgeon applied one gram vancomycin powder (500mg applied directly on the prosthesis and 500mg applied above the closed joint capsule). The incidence of acute surgical site infection was defined as positive deep cultures within 42 days of procedure. All patients with evidence of infection underwent joint aspiration for culture. After one year, 80 patients had received the topical vancomycin treatment and 85 patients had received the standard treatment. In the topical vancomycin group versus the controlled group, the average age was 64 vs 66, average BMI was 35.7 vs 33.4, number of males 33 vs 29, number of females 47 vs 56, and diabetic patients 16 vs 13. The number of infections in the topical vancomycin group was three vs zero in the post-operative IV antibiotic treatment group. One Tailed Z-test P Value = 0.03. This study statistically demonstrated inferiority of topical vancomycin in comparison to the use of IV antibiotics post-operatively in preventing deep wound infections in TKA. The authors would caution against the sole use of intra-operative vancomycin in TKA to prevent post-operative infection

The causes of pain after TKA can be local (intra or extra-articular) or referred from a remote source. Local intra-articular causes include prosthetic loosening, infection, aseptic synovitis (wear debris, hemarthrosis, instability, allergy), impingement (bone soft tissue or prosthetic), an un-resurfaced patella and stress fracture of bone or the prosthesis. Some surgeons think that isolated component mal-rotation can be a source of pain, but component mal-rotation is rarely present in the absence of other technical abnormalities. Local extra-articular causes include pes anserine bursitis, saphenous neuroma/dysasthesias, post-tourniquet dysasthesias, complex regional pain syndrome and vascular claudication. Referred pain is most often from an arthritic hip or radicular pain from a spinal source. Patients with fibromyalgia can have persistent pain following their knee arthroplasty and should be warned of this possibility. Evaluation of the patient includes a history, physical exam, joint aspiration and plain radiographs. In selected patients, an anesthetic joint injection, bone scan, CT scan or MRI with metal subtraction may be helpful in the diagnosis. The joint aspiration should include a CBC and differential as well as an aerobic and anaerobic culture. Fungal and TB cultures are sometimes indicated. Re-operation for pain of unknown etiology following TKA is unlikely to yield an excellent result and both surgeons and patients should be aware of this probability

C-reactive protein (CRP) level is used at our tertiary paediatric hospital in the diagnosis, management, and discharge evaluation of paediatric septic arthritis patients. The purpose of this study was to evaluate the efficacy of a discharge criterion of CRP less than 2 mg/dL for patients with septic arthritis in preventing reoperation and readmission. We also aimed to identify other risk factors of treatment failure. Patients diagnosed with septic arthritis between January 1, 2007 and December 31, 2017 were reviewed retrospectively. The diagnosis of septic arthritis was made based on clinical presentation, laboratory results and the finding of purulent material on joint aspiration or the isolation of a bacterial pathogen from joint fluid or tissue. Bivariate tests of associations between patient or infection factors and readmission and reoperation were performed. Quantitative variables were analyzed using Mann-Whitney tests and categorical variables were analyzed using Chi-square tests. One hundred eighty-three children were included in the study. Seven (3.8%) were readmitted after hospital discharge for further management, including additional advanced imaging, and IV antibiotics. Six (85.7%) of the readmitted patients underwent reoperation. Mean CRP values on presentation were similar between the two groups: 8.26 mg/dL (± 7.87) in the single-admission group and 7.94 mg/dL (± 11.26) in the readmission group (p = 0.430). Mean CRP on discharge for single-admission patients was 1.71 mg/dL (± 1.07), while it was 1.96 mg/dL (± 1.19) for the readmission group (p = 0.664), with a range of < 0 .8 to 6.5 mg/dL and a median of 1.5 mg/dL for the two groups combined. A total of 48 children (25.9%) had CRP values greater than the recommended 2 mg/dL at discharge, though only three of these patients (6.2%) were later readmitted. The only common variable in the readmitted children was either a negative culture result at time of discharge or atypical causative bacteria. CRP values are useful in monitoring treatment efficacy but not as reliable as a discharge criterion to prevent readmission or reoperation in children with septic arthritis. We recommend determining discharge readiness on the basis of clinical improvement and downtrending CRP values. There was a higher risk of readmission in children with an atypical causative bacteria and when culture results were negative at discharge. Close monitoring of these patients after discharge is suggested to identify signs of persistent infection

Aim. Apart from other biomarkers isolated in the synovial fluid, alpha-defensin appears to be a promising diagnostic tool to confirm a periprosthetic joint infection (PJI) in the hip or knee. The purpose of this study was to evaluate the sensitivity and specificity of an alpha defensin lateral flow (ADLF) test compared to usual standard classifications in the diagnostic management of PJI. Method. This investigation was set up as a multicenter prospective cohort study. Synovial fluid was obtained by means of joint aspiration or intra-operative tissue biopsies. A presumptive PJI diagnosis was made according to criteria outlined by the Musculoskeletal Infection Society (MSIS), the Infectious Diseases Society of America (IDSA) and the European Bone and Joint Infection Society (EBJIS). The intention to treat by the surgeon was logged. Sensibility and specificity for the ADLF test was plotted for each aforementioned diagnostic algorithm. Spearman correlations between all scores were analyzed. Multiple logistic regression was used to determine the contribution of independent variables to the probability of PJI. Results. Hundred thirty-six patients with a painful arthroplasty were assessed for infection and rated by the treating surgeon as potentially infected or not on the basis of clinical and laboratory information. According to the EBJIS criteria sixty-eight patients were deemed infected, fifty according to the IDSA criteria, forty-one according to the MSIS criteria and forty according to the ADLF test. However, the sensitivity of ADLF test was 87.8% for MSIS, 70% for IDSA and 55.8% for EBJIS. The specificity of ADLF test was between 94% – 97%. Good correlation was observed between synovial fluid culture and ADLF test (r = 0.73). Low to excellent correlations between the ADLF test and the EBJIS (r = 0.58), IDSA (r = 0.68), and MSIS score (r = 0.84) were observed. The surgeon's intention to treat correlated well with the MSIS score (r = 0.86), and moderately with the EBJIS (r = 0.59). Conclusions. ADLF test sensibility was variable, but its specificity was excellent. Most of the cases, not retained by MSIS but classified by EBJIS as infected, got a negative microbiological result. Considering an accepted 20% negative microbiological result rate in PJI diagnostic, EBJIS is clearly overestimating the number of infected cases. MSIS score correlates with the surgeon intention to treat and ADLF test