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 a devasting complication after total hip arthroplasty. Joint aspiration and preoperative biopsy can be helpful diagnostics for PJI. The aim of this study is to evaluate the diagnostic value of preoperative biopsies after inconclusive or dry tap aspiration of the hip in patients undergoing revision hip arthroplasty. Secondarily we will evaluate the diagnostic value of synovial fluid aspiration cultures and peroperative tissue cultures for diagnosing or ruling out PJI. Methods. Patients who underwent diagnostic aspiration and subsequent preoperative biopsy and/or revision surgery between January 2015 and January 2024 were included in the study. Synovial fluid aspirations and tissue samples obtained from biopsy and revision surgery were interpreted using the European Bone and Joint Infection Society criteria for PJI and in close consultation with the microbiologist. Results. 207 Patients were included with 231 synovial fluid aspirations. Sensitivity and specificity of synovial fluid aspiration cultures were 76% and 98%. In 62 patients tissue biopsies were performed, of which 40 after a dry tap. The tissue biopsies after a dry tap aspiration had a sensitivity of 50.0% and a specificity of 95.8%. In 21% tissue biopsies led to the confirmation of PJI in patient with a high suspicion of PJI after dry tap aspiration. In patients with an inconclusive synovial fluid aspiration result the addition of tissue biopsies led to a change in treatment in 14%. In 212 cases revision surgery was performed, intraoperative tissue cultures had a sensitivity and specificity of 83.3% and 99.3%. Conclusions. Diagnosing PJI can be troublesome, especially if synovial fluid aspiration provides a dry tap. Tissue biopsy cultures in patients with a high suspicion of PJI after dry tap aspiration is a feasible way to confirm PJI, in 21% of patients PJI could be confirmed after dry tap aspiration. Ruling out PJI by means of a biopsy after a dry tap aspiration is less successful due to its low sensitivity. Tissue biopsies after an inconclusive aspiration leads to clinically important treatment changes

We analysed the serum C-reactive protein level, synovial fluid obtained by joint aspiration and five synovial biopsies from 145 knee replacements prior to revision to assess the value of these parameters in diagnosing late peri-prosthetic infection. Five further synovial biopsies were used for histological analysis. Samples were also obtained during the revision and incubated and analysed in an identical manner for 14 days. A total of 40 total knee replacements were found to be infected (prevalence 27.6%). The aspiration technique had a sensitivity of 72.5% (95% confidence interval (CI) 58.7 to 86.3), a specificity of 95.2% (95% CI 91.2 to 99.2), a positive predictive value of 85.3% (95% CI 73.4 to 100), a negative predictive value of 90.1% (95% CI 84.5 to 95.7) and an accuracy of 89%. The biopsy technique had a sensitivity of 100%, a specificity of 98.1% (95% CI 95.5 to 100), a positive predictive value of 95.2% (95% CI 88.8 to 100), a negative predictive value of 100% and an accuracy of 98.6%. C-reactive protein with a cut-off-point of 13.5 mg/l had a sensitivity of 72.5% (95% CI 58.7 to 86.3), a specificity of 80.9% (95% CI 73.4 to 88.4), a positive predictive value of 59.2% (95% CI 45.4 to 73.0), a negative predictive value of 88.5% (95% 81.0 to 96.0 CI) and an accuracy of 78.1%. We found that biopsy was superior to joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements

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

Introduction. Pre-operative aspiration and culture is the gold standard for the diagnosis of peri-prosthetic infection. This study aimed to ascertain the diagnostic accuracy of culture of joint aspiration with or without saline re-aspiration in the event of a dry-tap. Patients/Materials & Methods. Retrospective analysis of 343 hip aspirations in patients deemed to have moderate-high risk of infection and ultimately proceeded to revision arthroplasty over 12 years at a large quaternary referral centre where pre-operative aspiration is routine. Results. Fluid was aspirated in 141(41%) cases and dry taps in which saline injection-re-aspiration was performed occurred in 202 (59%) cases. Overall sensitivity and specificity of diagnostic aspirate were 82% (74–88%) and 79% (74–84%) respectively. Sensitivity and specificity of saline injection-re-aspiration after dry tap were 79% (64–87%) and 86% (78–92%) compared to 84% (74–91%) and 74% (66–81%) for direct aspiration. Discussion. Pre-operative joint aspiration and culture is a sensitive and specific test for the confirmation of diagnosis in patients at a moderate to high risk of prosthetic joint infection. Culture of saline injection-re-aspiration also provides accurate diagnostic information in the event of a dry tap. Both methods allow susceptibility testing of relevant organisms and are therefore able to guide peri-operative and cement instilled antibiotic therapy. Conclusions. Culture of pre-operative joint aspirates provides sensitive and specific diagnostic information, including antimicrobial susceptibility results. Saline injection-re-aspiration is a useful additional technique in those patients in whom fluid cannot be aspirated

Aims. The aim of this study was to establish the diagnostic accuracy of culture of joint aspirate with and without saline injection-reaspiration. Patients and Methods. This is a retrospective analysis of 580 hip and knee aspirations in patients who were deemed to have a moderate to high risk of infection, and who subsequently proceeded to revision arthroplasty over a period of 12 years. It was carried out at a large quaternary referral centre where preoperative aspiration is routine. Results. Fluid was aspirated primarily in 313 (54%) cases and after saline injection-reaspiration of a ‘dry tap’ in 267 (46%) cases. Overall sensitivity and specificity of the diagnostic aspirate were 84% (78% to 89%) and 85% (81% to 88%), respectively. Sensitivity and specificity of saline injection-reaspiration after ‘dry tap’ were 87% (79% to 92%) and 79% (72% to 84%) compared with 81% (71% to 88%) and 90% (85% to 93%) for direct aspiration. Conclusion. Preoperative joint aspiration and culture is a sensitive and specific test for the confirmation of diagnosis in patients at a moderate to high risk of prosthetic joint infection. Culture of saline injection-reaspiration also provides accurate diagnostic information in the event of a ‘dry tap’. Both methods allow susceptibility testing of relevant organisms and are therefore able to guide perioperative antibiotic therapy. Cite this article: Bone Joint J 2018;100-B:749–54

No single test is 100% sensitive and specific for the diagnosis of prosthetic joint infection. Joint aspiration is currently the only preoperative investigation that can establish the identity of the infecting organism and its antibiotic susceptibilities. Frequently when attempting to aspirate a joint a ‘dry tap occurs as fluid cannot be aspirated. In this situation, normal saline may be injected into the joint and then reaspirated to provide fluid for culture. The aim of this study was to ascertain the diagnostic accuracy of culture of joint aspiratie with or without saline reaspiration in the event of a dry tap. A retrospective analysis of 580 hip and knee aspirations in patients deemed to have moderate-high risk of infection and ultimately proceeded to revision arthroplasty over 12 years at a large quaternary referral centre where pre operative aspiration is routine. Fluid was aspirated in 313 (54%) cases and dry taps in which saline injection reaspiration was performed occurred in 267 (46%) cases. Overall sensitivity and specificity of diagnostic aspiration were 84% (78–89%) and 85% (81–88%) respectively. Sensitivity and specificity of saline injection-reaspiration after dry tap were 87% (79–82%) and 79% (72–84%) compared to 81% (71–88%) and 90% (85–93%) for direct aspiration. Pre operative joint aspiration and culture is a sensitive and specific test for the confirmation of diagnosis in patients at a moderate to high risk of prosthetic joint infection. Culture of saline injection-reaspiration also provides accurate diagnostic information in the event of a dry tap. Both methods allow susceptibility testing of relevant organisms and are therefore able to guide peri-operative and cement instilled antibiotic therapy. Culture of pre operative joint aspirates provides sensitive and specific diagnostic information including antimicrobial susceptibility results. Saline injection-reaspiration is a useful additional technique in those patients in whom fluid cannot be aspirated

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

The purpose of our presentation is to propose a asimple and reliable method which does not expose the doctor and the patient to radiation for hip arthrocentesis and to be used by inexperienced doctors as well as for studies. Hip Arthrocentesis (HA) on every day practice is performed by the anatomic knowledge and experience. But as a study has shown there is a high failure rate as it concerns the correct position of the needle in the joint, even in joints as the knee and shoulder where the intraarticular injections as usual. According to the American College of Rheumatology hip arthrocentesis should be performed by experienced Rheumatologists, Orthopaedic Surgeons and Radiologists, and always under radiological control. HA at first has been performed for diagnostic purposes, mainly infections, for fluid aspiration. Later for therapeutic reasons (corticosteroids), and for the differential diagnosis between abdominal and osteoarthritic pain of the hip with the intraarticular injection of local anaesthetic. HA under ultrasound control was initially performed in 1989 for diagnostic reasons and later in 2001 has been used for intraarticular injections of Hyalouronic Acid for the treatment of hip osteoarthritis. In the international literature publications about the help that Ultrasonography provides at hip arthrocentesis are sporadic (sparse). Since 2000 we performed 50 intraarticular injections at the hip joint in our out -patient department under ultrasonographic control for the confirmation of the correct position of the needle in the articulation. All patients suffered from hip osteoarthritis according to the criteria of the American College of Rheumatology, and all were female, 50 – 75 years old. 30 injections were performed with simple head (Convex) of 6 MHz and 20 with linear head of 9 MHz. There was no difference concerning the accuracy of needle placement, but a more clear picture had the linear head. There was no complication. In the Hellenic area, to our knowledge, this method is applied and announced for the first time. In conclusion we believe that it is an accurate and safe method which does not expose neither the patient nor the doctor to radiation and is much less time – consuming than CT. it can be recommended for inexperienced collegues, for studies that need confirmation, as well as for control of the correct placement of the needle intraarticular for therapeutic purposes. In general it can be used for every hip arthrocentesis

Based on the first implementation of mixing antibiotics into bone cement in the 1970s, the Endo-Klinik has used one stage exchange for prosthetic joint infection (PJI) in over 85% of cases. Looking carefully at current literature and guidelines for PJI treatment, there is no clear evidence that a two stage procedure has a higher success rate than a one-stage approach. A cemented one-stage exchange potentially offers certain advantages, mainly based on the need for only one operative procedure, reduced antibiotics and hospitalisation time. In order to fulfill a one-stage approach, there are obligatory pre-, peri- and post-operative details that need to be meticulously respected, and are described in detail. Essential pre-operative diagnostic testing is based on the joint aspiration with an exact identification of any bacteria. The presence of a positive bacterial culture and respective antibiogram are essential, to specify the antibiotics to be loaded to the bone cement, which allows a high local antibiotic elution directly at the surgical side. A specific antibiotic treatment plan is generated by a microbiologist. The surgical success relies on the complete removal of all pre-existing hardware, including cement and restrictors and an aggressive and complete debridement of any infected soft tissues and bone material. Post-operative systemic antibiotic administration is usually completed after only ten to 14 days. . Cite this article: Bone Joint J 2013;95-B, Supple A:77–83

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.

Periprosthetic infection (PPI) remains the most dreaded and difficult complication of total joint arthroplasty. Although there is no definite diagnostic test for PPI, synovial leukocyte count and neutrophil percentage have been reported to have high sensitivity and specificity. However, leukocytes and neutrophils introduced into the joint during a traumatic aspiration can skew results and undermine the predictive value of this diagnostic test. This study intends to determine the diagnostic value of implementing a corrective formula frequently used in traumatic spinal taps to adjust for serum leukocytes introduced into the joint fluid during a bloody tap.

We conducted a review of all TKA aspirations of infected and non-infected patients performed at our institute from 2000 to 2005.

The following inclusion criteria were used:

(a) a red cell count (RBC) was performed on the aspirate, and

Patients with inflammatory arthropathy or those who underwent reimplantation after PPI were excluded. Strict criteria for diagnosis of PPI were used. We previously determined at our institute the cut-off values for fluid leukocyte count (> 1760 cells/μl) and neutrophil percentage (> 73%).

The adjusted fluid leukocyte counts were calculated using the following formula:

Wadjusted = WBCobserved – [(WBCblood * RBC-fluid/RBCblood)] predicted.

A similar formula was implemented to calculate the adjusted absolute neutrophil counts.

Our cohort included 73 infected and 32 aseptic total knee arthroplasties that fulfilled the above criteria. After correcting for introduced red blood cells, cell counts of 3 infected patients dropped below the cut-off value, while the remaining 70 maintained a high cell count. However, the 3 infected patients had initial cell counts below our reported cut-offs. Of the 32 non-infected patients, 10 patients had false positive cell counts due to the presence of extremely high numbers of blood RBC. Five of the 10 false positive aspirates successfully corrected to levels below the thresholds used to diagnose infection. The aspirates that corrected had a greater number of introduced RBCs, an initial higher cell count, and 20 times more fluid WBC deducted from the initial cell count.

The corrective formula can safely adjust for RBC found in a traumatic tap and detect false positive results among non-infected TKA without compromising the diagnosis of infection. Adjusted aspirates of non-infected TKA can be expected to decrease below zero due to one of the following: adherence of the introduced systemic WBC to the joint synovium, greater rate of lysis of the introduced systemic WBC compared to the systemic RBC, laboratory errors in performing fluid cell counts.

Purpose: The role of hip aspiration as a preoperative investigation for the painful hip remains controversial. Since 1999, we have performed hip aspiration under local anaesthetics in the X-ray department. This paper reviews our experience with this technique.

Results: Hip aspirations were carried out subsequently on 182 patients from November 1999 to November 2002. Out of 68 patients that underwent revision hip surgery, 63 were included in the study. Three of the five patients excluded had received antibiotics at induction prior to obtaining the operative samples and two did not have any operative samples taken at the time of surgery. Fifteen (23.8%) of the 63 hips were found to be infected based on operative tissue cultures. The sensitivity and specificity of the test were 80% and 87.5%, respectively. Positive and negative predictive values were 66.6% and 93.3% respectively and the accuracy was 85.7%.

Conclusion: Hip aspiration in the Radiology department is a simple, cost effective and reliable preoperative test when used selectively. When used in combination with other laboratory and radiological investigation it can act as an important preoperative investigation in the diagnosis of sepsis. There is an added advantage of identifying the microorganism along with its antibiotic sensitivities. This can guide clinicians in choosing the correct antibiotic for the cement and also for the postoperative antibiotic therapy.

Aims. Current guidelines consider analyses of joint aspirates, including leucocyte cell count (LC) and polymorphonuclear percentage (PMN%) as a diagnostic mainstay of periprosthetic joint infection (PJI). It is unclear if these parameters are subject to a certain degree of variability over time. Therefore, the aim of this study was to evaluate the variation of LC and PMN% in patients with aseptic revision total knee arthroplasty (TKA). Methods. We conducted a prospective, double-centre study of 40 patients with 40 knee joints. Patients underwent joint aspiration at two different time points with a maximum period of 120 days in between these interventions and without any events such as other joint aspirations or surgeries. The main indications for TKA revision surgery were aseptic implant loosening (n = 24) and joint instability (n = 11). Results. Overall, 80 synovial fluid samples of 40 patients were analyzed. The average time period between the joint aspirations was 50 days (SD 32). There was a significantly higher percentage change in LC when compared to PMN% (44.1% (SD 28.6%) vs 27.3% (SD 23.7%); p = 0.003). When applying standard definition criteria, LC counts were found to skip back and forth between the two time points with exceeding the thresholds in up to 20% of cases, which was significantly more compared to PMN% for the European Bone and Joint Infection Society (EBJIS) criteria (p = 0.001), as well as for Musculoskeletal Infection Society (MSIS) (p = 0.029). Conclusion. LC and PMN% are subject to considerable variation. According to its higher interindividual variance, LC evaluation might contribute to false-positive or false-negative results in PJI assessment. Single LC testing prior to TKA revision surgery seems to be insufficient to exclude PJI. On the basis of the obtained results, PMN% analyses overrule LC measurements with regard to a conclusive diagnostic algorithm. Cite this article: Bone Jt Open 2021;2(8):566–572

Aims. The aims of this study were to: 1) report on a cohort of skeletally mature patients with native hip and knee septic arthritis over a 14-year period; 2) to determine the rate of joint failure in patients who had experienced an episode of hip or knee septic arthritis; and 3) to assess the outcome following septic arthritis relative to the infecting organism, whether those patients infected by Staphylococcus aureus would be more likely to have adverse outcomes than those infected by other organisms. Methods. All microbiological samples from joint aspirations between March 2000 and December 2014 at our institution were reviewed in order to identify cases of culture-proven septic arthritis. Cases in children (aged < 16 years) and prosthetic joints were excluded. Data were abstracted on age at diagnosis, sex, joint affected (hip or knee), type of organisms isolated, cause of septic arthritis, comorbidities within the Charlson Comorbidity Index (CCI), details of treatment, and outcome. Results. A total of 142 patients were confirmed to have had an episode of septic arthritis in a native hip (n = 17) or knee joint (n = 125). S. aureus accounted for 57.7% of all hip and knee joint infections. There were 13 inpatient deaths attributed to septic arthritis. The median age of the patients who died was 77.5 (46.9 to 92.2) and their median age-adjusted CCI was 8 (6 to 12). A failure of the joint occurred in 26 knees (21%) and nine hips (53%). Of the knee joints infected by S. aureus (n = 71), 23 knees (32%) went into failure of joint, whereas of those infected by other organisms (n = 54), only three knees (6%) failed. Conclusion. Based on our study findings, hip and knee septic arthritis long-term outcomes were substantially worse than their immediate outcome suggested. Failure of knee joint is 6.1 times more likely to occur in those infected with S. aureus. Cite this article: Bone Jt Open 2024;5(9):785–792

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. Prosthetic joint infection (PJI) is assessed using clinical history and examination, imaging studies and laboratory investigations which inform diagnostic tools such as that proposed by the European Bone and Joint Infection Society to determine the probability of infection. Infection is often confirmed by microbiology culture and histology from intraoperative samples, but ideally a diagnosis of infection is made preoperatively to guide management decisions. At our institution, a tertiary referral centre for PJI, ultrasound (US)-guided synovial biopsy is routinely used as an adjunct to preoperative joint aspiration. Our aim was to evaluate the sensitivity and specificity of microbiology and histology results from US-guided synovial biopsy samples when compared to intraoperative samples. Method. In this retrospective study we analysed all prosthetic hip and knee US-guided biopsies performed at our institution over a 5 year period between 2018 and 2022. Microbiology and histology results from preoperative biopsy samples were individually compared to microbiology and histology findings from intraoperative samples. Results. 381 biopsies were performed; 281 knee, 100 hip. US-guided biopsy results showed strong positive predictive values (PPVs) in hip biopsies (microbiology PPV (79.3%), histology PPV (85.7%)) and knee biopsies (microbiology PPV (77%), histology PPV (85%)). Biopsies showed low sensitivity in predicting intraoperative findings (hip microbiology sensitivity (62%), hip histology sensitivity (31%), knee microbiology sensitivity (70%), knee histology sensitivity (21%). Biopsies showed high specificity for knee (microbiology specificity (89%), histology specificity (97%)) and hip (microbiology specificity (73%), histology specificity (91%)). Conclusions. This study demonstrates that US-guided biopsy is a valuable diagnostic aid for PJI with high specificities and PPVs. Furthermore US-biopsy is valuable when there is limited fluid for aspiration