Aims

The purpose of this study was to evaluate the infection-free outcome of patients underwent revision of total joint arthroplasty (TJA) for presumed aseptic causes, with positive intra-operative cultures.

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

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. Periprosthetic joint infection (PJI) is a complication of total joint arthroplasty that typically requires revision surgery for treatment. Systemic antibiotics are usually held prior to surgery to improve yield of intraoperative cultures. However, recent studies suggest that preoperative aspirations have a high concordance with intraoperative cultures, which may allow surgeons to initiate antibiotic treatment earlier. The purpose of the study was to investigate the effect of Pre-surgical systemic antibiotic therapy on the bacterial burden within the periprosthetic space and systemic immune reaction. Method. PJI was induced with MSSA (Xen36) S. aureus in the right knee of 16-week old, female, C57BL6 mice using a previously validated murine model. Mice were randomized to three groups (n=8, each): control; Vanc, receiving systemic vancomycin (110mg/kg, SQ, twice daily); or VancRif receiving vancomycin same as in Vanc group, plus rifampin (12mg/kg dose, IV, once daily). Following 2 weeks of treatment, mice were euthanized and periprosthetic bone, soft tissue and the implant were harvested. Bacterial burden, colony forming units (CFUs), was quantified in soft tissue, tibial bone, and on the implant. Specifically, tissues were homogenized and serially plated for CFUs, while the implant was sonicated and then plated for CFUs. The host immune response was analysed through weighing inguinal and iliac lymph nodes and through measuring serum amyloid A (SAA). Non-parametric pairwise group comparisons of the three outcome measures were performed using a Mann-Whitney U test. Results. VancRif, the combined treatment significantly reduced bacterial burden in the periprosthetic soft tissue, bone, and implant compared to control (p<0.001) and Vanc alone (p<0.001). While not significant, Vanc alone did reduce bacterial load as compared to control. The ipsilateral weight of the iliac lymph nodes was significantly reduced in Vanc and VancRif mice compared to controls (p<0.001), was well as in VancRif versus Vanc alone (p<0.001). Interestingly, SAA levels did not significantly differ among all groups. During tissue harvesting, minimal purulence was observed in antibiotic treatment groups, unlike controls. Conclusions. Treating active PJI with vancomycin alone decreases periprosthetic bacterial loads and reduces the local immunological response. This effect is significantly enhanced with the combined rifampin use. These findings could suggest that when culture positive PJI is diagnosed, pre-surgical treatment with antibiotics may decrease immunosuppression and soft tissue infiltration, leading to a better chance of infection cure with subsequent surgical debridement. Histological investigations and repeat experiments involving subsequent surgical treatment are underway. Acknowledgements. Funding comes from internal institutional grants

Aim. Our aim was to evaluate the prevalence and impact of unexpected intraoperative cultures on the outcome of total presumed aseptic knee and hip revision surgery. Method. Data regarding patients prospectively recruited in our center, who had undergone elective complete hip and knee revision surgery from January 2003 to July 2017 with a preoperative diagnosis of aseptic loosening was retrospectively reviewed. Partial revisions and patients with follow up below 60 months were excluded from the study. The protocol of revision included at least 3 intraoperative cultures. Failure was defined as the need for re-revision due to any-cause at 5 years and/or the need for antibiotic suppressive therapy. Results. A total of 608 cases were initially included in the study, 53 patients were excluded. 123 hip and 432 knee revision surgeries were included. 420 cases (75.7%) had all cultures negative, 114 (20.5%) a single positive culture or two of different microorganisms and 21 (3.8%) had at least 2 positive cultures for the same microorganism. Early failure was found in 4.8% (1/21) of the patients with missed low grade infection. The presence of positive cultures during total exchange was not associated with a higher failure rate than in those with negative cultures (44 of 420, 10.5%). In contrast, patients revised before 24 months had a significant higher rate of re-revision, 18% (15/83) vs. 8.4%. Conclusions. Total hip and knee revisions with unexpected positive cultures were not significantly associated with a higher re-revision risk at 5 years of follow-up. Representing an overall good prognosis. However, revision surgeries performed within the first 24 months have a higher rate of failure

Aim. Despite a preoperative workup with no evidence to suspect a prosthetic joint infection (PJI) before revision surgery, routinely obtained intraoperative cultures still can be unexpectedly positive. The purpose of this study was (1) to assess the incidence of unexpected positive intraoperative cultures in presumed aseptic knee and hip revisions and (2) to determine whether a difference exists between the infection-free implant survival rate of patients with and without unexpected positive intraoperative cultures. Method. We selected patients who underwent a one-stage revision total knee arthroplasty (TKA) or total hip arthroplasty (THA) for different reasons. Three or more separate intraoperative cultures were obtained during each procedure. A negative result was defined as less than two positive cultures with the same microorganism. An unsuspected PJI was defined as having two or more positive cultures with the same microorganism. Patients’ medical records were reviewed to collect demographics, preoperative laboratory results, culture results, and the occurrence of infection during follow-up. Results. A total of 340 and 339 patients with a presumed aseptic knee and hip revision, respectively, were analyzed. The incidence of unsuspected PJIs was 7.9% and 12.1% in the knees and hips, respectively. Of these unsuspected PJIs, the infection-free prosthetic survival rate at 2 year follow-up was 88% (95%CI 59–97) and 92% (95%CI 73–98) in knees and hips, respectively. In the knee group, the infection-free prosthetic survival rate of patients with an unsuspected PJI was significantly lower compared to that of patients with negative intraoperative culture results (88% (95%CI 59–97) versus 97% (95%CI 93–99) with p=0.01). In the hip group, there was no such a difference (92% (95%CI 73–98) versus 93% (95%CI 88–96) with p=0.41). Conclusions. We found incidences of unsuspected PJI and infection-free prosthetic survival rates that are comparable with previous studies. During follow-up after one-stage revision TKA, a higher incidence of infection was observed in patients with an unsuspected PJI. This difference was not observed in the hip revisions

Aim. Surgical and antimicrobial treatment of periprosthetic joint infections (PJI) depends largely on the causative pathogen. We assessed the pathogen detection rates and the concordance of preoperative synovial fluid culture and culture of intraoperative samples harvested during revision surgery in patients with PJI. Method. Culture-positive PJI cases treated at our institution from 02/2011 to 07/2018, for which culture results from preoperative (synovial fluid) and intraoperative samples (periprosthetic tissue, synovial or sonication fluid) were available, were retrospectively assessed. For organisms belonging to the resident skin flora (coagulase-negative staphylococci, cutibacteria and corynebacteria) significant growth was considered, if the identical pathogen grew in ≥2 samples or >50 cfu/ml sonication fluid. For other pathogens (S. aureus, streptococci, enterococci, fungi and gram-negative rods) or patients under antimicrobials, any growth was considered positive. We determined the pathogen detection rate in preoperative and intraoperative cultures and compared it in different subgroups using Fisher's exact test. Furthermore, we assessed the concordance of preoperative and intraoperative cultures. Results. We included 167 culture-positive PJI cases (76 hip and 91 knee joints). Coagulase-negative staphylococci (n=55, 33%), Staphylococcus aureus (n=34, 20%) and streptococci (n=22, 13%) were the most common pathogens. In 17 cases (10%) polymicrobial infection was found. The pathogen(s) grew in synovial fluid in 105 cases and in intraoperative samples in 146 cases (63% vs. 87%, p<0.001). 49 patients received antibiotics before aspiration and/or surgery. No differences were observed comparing hip and knee prostheses, primary and revision prostheses or patients receiving or not receiving antibiotics before sampling. Congruent results of preoperative and intraoperative cultures were found in 85 cases (concordance 51%). In 14 cases (8%), the pathogen was detected preoperatively only, in 59 cases (35%) the pathogen was found intraoperatively only; in 3 cases an additional pathogen was found preoperatively, in 6 cases an additional organism was found intraoperatively. Pathogen detection was significantly better in intraoperative compared to preoperative cultures in low-virulent pathogens (87% vs 36%, p<0.001), polymicrobial infections (88% vs. 47%, p<0.001) and delayed/late PJI (>3months; 92% vs 64%, p<0.001). There was no difference regarding detection rate of high-virulent pathogens (88% vs 83%) and in early postoperative PJI (<3 months, 91% vs. 73%). Conclusions. As concordance of preoperative and intraoperative microbiological results was 51%, surgical and antimicrobial treatment should not be selected based on preoperative synovial fluid cultures only. An additional pathogen was found intraoperatively in 39%

Aim. Aseptic loosening is the leading cause of revision of total hip arthroplasty (THA). It is well recognized that an occult infection is the underlying cause of some aseptic revisions. Intraoperative cultures are central to the diagnosis of prosthetic joint infection (PJI). However, the diagnostic and prognostic value of unexpected positive intraoperative cultures remains unclear. The aim was to study whether first-time aseptic revision of a total hip arthroplasty with unexpected bacterial growth in cultures of intraoperatively taken biopsies have an increased risk of secondary revision due to all causes and increased risk of PJI revision, specifically. Method. Cases reported as first-time aseptic loosening revisions to the Danish Hip Arthroplasty Register (DHR) performed during January 1. st. , 2010, to May 15. th. , 2016, were included. DHR data were merged with the Danish Microbiology Database, which contains data from all intraoperatively obtained cultures in Denmark. Included first-time revisions were grouped based on the number of positive cultures growing the same bacteria genus: ≥2, 1 and 0 cultures. Revisions were followed until secondary revision, death, or end of follow-up period after one year. Relative risk for secondary revision due to all causes and PJI was estimated. Results. We included 2,305 first-time aseptic revisions. Unexpected growth was found in 282 (12%) of which 170 (60%) cases showed growth of the same bacteria in only one culture. Coagulase-negative staphylococcus accounted for 121 (71%). Secondary revision was performed in 163 (7%) cases, with PJI being the indication for revision in 43 (26%) cases. The relative risk of secondary revision was significantly higher for cases of one positive culture growing the same bacteria compared to culture negative cases, both for revision due to all causes; 1.73 (95%CI 1.07; 2.80) and PJI exclusively; 2.63 (1.16; 5.96). Cases of 2 or more biopsies culturing the same bacteria had a relative risk of all cause revision of 1.52 (0.82; 2.80). Conclusions. First-time aseptic loosening THA revisions with unexpected growth in only one biopsy culture had an increased risk of secondary revision, both due to all causes and PJI. Our findings indicate that some cases of unexpected growth of bacteria should likely be regarded as clinically significant and not sample contamination, underlining the need for more awareness and better strategies when treating patients with unexpected positive intraoperative cultures. The improved diagnosis of occult PJI in clinically aseptic THA is of great importance for future care of this large and growing patient group

Introduction:. The diagnosis of implant-associated infections is challenging, and the conventional culturing of periprosthetic tissue has been the gold standard for diagnosis of implant-associated infections. However, conventional diagnostic tests are inaccurate because the pathogenesis of implant-associated infection is related to microorganisms growing in biofilms. We compared culture of samples obtained by sonication of explanted implants to dislodge adherent bacteria from implants with conventional culture of periprosthetic tissue. The purpose of this study is to evaluate the results of sonication that is microbiological diagnostic method for implant-associated infections. Materials and Methods:. Between January 2013 and April 2013, a total of 19 consecutive patients underwent the removal of implants at our institution. There were 15 women and 4 men with a mean age of 71 years (32 to 90) at the time of the operation. Implants were removed because of aseptic loosening in 9 patients, infection in 6 patients, necrosis in 2 patients, dislocation in 1 patient and implant fracture in 1 patient. Removed implants, including 17 joint prostheses and 2 fracture fixation devices, were subjected to sonication in a BactoSonic (BANDELIN, Germany). Preoperative bacterial culture, intraoperative conventional culture of periprosthetic tissue, intraoperative culture of sonicate-fluid, and pathological examination were assessed. Results:. Of the 9 patients with aseptic loosening, 1 patient was positive for intraoperative conventional culture of periprosthetic tissue, and 2 patients were positive for intraoperative culture of sonicate-fluid. In the patient with negative culture of periprosthetic tissue and positive culture of sonicate-fluid, pathological findings indicated the presence of neutrophils in tissue specimen. Of the 6 patients with infection, 4 patients were positive for intraoperative conventional culture of periprosthetic tissue, and 3 patients were positive for intraoperative culture of sonicate-fluid. Of the 4 patients with necrosis, dislocation, and implant fracture, no patients were positive for intraoperative conventional culture of periprosthetic tissue or intraoperative culture of sonicate-fluid. Conclusion:. Culture of sonicate-fluid has been shown to improve the diagnosis of implant-associated infections. In the future, it may be common technique for diagnosis of implant-associated infections associated with biofilm, but this new technique needs further study

Aim. Bone infections often manifest with soft tissue complications such as severe scarring, fistulas, or ulcerations. Ideally, their management involves thorough debridement of infected bone and associated soft tissues, along with achieving stable bone structure, substantial tissue coverage, and long-term antibiotic therapy. The formation of a multidisciplinary team comprising orthopedic surgeons, plastic surgeons, and infectious disease specialists is essential in addressing the most complex cases. Method. We conducted a retrospective study during six years (2018-2023) at our university center. Focusing on the most challenging cases, we included patients with bone infections in the leg and/or foot requiring free flap reconstruction. Each patient underwent simultaneous bone debridement and reconstruction by the orthopedic team, alongside soft tissue debridement and free flap reconstruction by the plastic surgery team. Targeted antibiotic therapy for either 6 weeks (acute) or 12 weeks (chronic osteitis) was initiated based on intraoperative cultures. Additional procedures such as allografts, arthrodesis, or autografts were performed if necessary. We analyzed the rates of bone union, infection resolution, and limb preservation. Results. Forty-five patients were enrolled. Twenty-four patients (53.3%) had urgent indications (e.g., open infected fractures, osteitis, acute osteoarthritis, or wound dehiscence), while 21 (46.7%) underwent elective surgery (e.g., septic pseudarthrosis or chronic osteitis). Two patients underwent amputation due to flap failure (4.4%), and one patient was lost to follow-up. Follow-up of the remaining 42 patients averaged 28 months (range: 6–60 months). During this period, 35 patients (83.4%) experienced no recurrence of infection. Similarly, 35 patients (83.4%) achieved bone union. Overall, the rate of lower limb preservation was 93.3%. Conclusions. Managing bone infection coupled with soft tissue defects brings significant challenges. Although the majority of patients treated here belong to a complex framework based on the BACH classification, the outcomes achieved here appear to align with those of the simpler cases, thanks to optimal care with a dedicated septic ortho-plastic team. Our study demonstrates a notable success rate in treating infection, achieving bone consolidation, and preserving lower limb function

Periprosthetic joint infections (PJI) continue to be a diagnostic challenge for orthopedic surgeons. Chronic PJI are sometimes difficult to diagnose and occasionally present in a subclinical fashion with normal CRP/ESR and/or normal joint aspiration. Some institutions advocate for routine use of intraoperative culture swabs at the time of all revision surgeries to definitively rule out infection. The purpose of this study is to determine whether routine intraoperative cultures is an appropriate and cost effective method of diagnosing subclinical chronic PJI in revision joint replacement patients with a low clinical suspicion for infection. We performed a retrospective chart review and identified 33 patients that underwent revision hip or knee replacement from a single surgeon over a five-month period. The AAOS guidelines for preoperative PJI workup were followed. 13 patients were diagnosed preoperatively with infection and excluded from the study. 20 patients underwent revision joint replacement and three separate cultures swabs were taken for each patient to help in determining true-positive cultures. Infectious Disease was consulted for all patients with any positive culture. Culture results were reviewed. At our hospital, the cost billed to insurance for a single culture is $1,458.58. We did not calculate the cost of the consultant fee. Three (15%) of the 20 revision arthroplasty patients had a single positive culture. Infectious Disease consultants diagnosed all three of these positive cultures as contaminants. None of the patients had a true-positive intraoperative culture. The total cost billed by the hospital to obtain these cultures in all 20 patients was $87,514.80. In our study, obtaining a set of three intraoperative cultures for those patients with a negative preoperative infection workup was not only cost prohibitive but did not diagnose a single subclinical infection. Studies to find other more reliable, accurate, and cost effective alternatives to diagnose PJI are warranted. In patients undergoing revision hip or knee arthroplasty with a low preoperative clinical suspicion for infection, it does not seem that routine intraoperative culture swabs are necessary or cost effective method for diagnosing subclinical periprosthetic joint infection

Aim. Periprosthetic joint infection (PJI) is a devastating complication in revision total hip arthroplasty (THA). As preoperative diagnosis can be difficult, some patients who undergo planned aseptic revision surgery might have positive intraoperative cultures and later be classified as infected. In this retrospective study we analyzed the influence of intraoperative positive cultures and possible underlying risk factors in patients undergoing planned aseptic THA revision. Method. We retrospectively analyzed 276 cases of aseptic THA revision surgery between 2010 and 2017 who had a minimum follow-up period of 24 months. All patients underwent preoperative serum and synovial diagnostics according to the Center of Disease Control (CDC) (2010) or Musculoskeletal Infection Society (MSIS) Criteria (2011–2017) for PJI and were classified as aseptic prior to surgery. In all cases intraoperative tissue samples were taken and reviewed. Primary endpoint was defined as any complication leading to revision surgery. Secondary endpoint was explantation due to PJI or death. Revision free survival (RFS) and infection free survival (IFS) for intraoperative negative and positive cultures was calculated via Kaplan Meyer Method. Patients’ medical history was analyzed for possible risk factors for positive cultures. Results. In 96 (34.78%) cases positive cultures were found. 67 (24.28%) had a single positive culture and 29 (10.51%) had ≥ two positive cultures. Coagulase negative staphylococci were found in 57.69% of the positive cultures. While the revision free survivorship was not different in patients with single positive cultures compared to patients with negative cultures (72.86 (95%CI 60.08–85.64) vs 83.01 months (95%CI 75.42–90.60) p=0.201), patients with ≥ two positive cultures had a reduced mean RFS (38.46 (95%CI 20.16–50.76) vs. 83.01 months (95%CI 75.42–90.60) p<0.02). 22 (7.97%) patients underwent explantation of the THA due to PJI. The IFS was reduced if ≥ two cultures were positive compared to culture negative patients (56.48 (95%CI 46.20–66.75) vs 110.78 months (95%CI 106.78–114.77) p=0.001). Risk for explantation due to PJI increased if ≥ two cultures were positive (Odds Ratio (OR) 3.19 (95%CI 1.36–7.52). A BMI ≥ 30 was associated with the risk of ≥ two positive cultures (OR 2.85 (95%CI 1.40–5.78). Conclusions. Occurrence of two or more positive cultures in aseptic revision THA has devastating influence on the revision free survival and infection free survival. As the risk for ≥ two positive cultures increase almost 3-fold in patients with a BMI ≥ 30, extended preoperative diagnostics in obese patients should be considered to detect possible low grade PJI before revision surgery

Purpose. Unexpected-positive-intraoperative-cultures (UPIC) in presumed aseptic revision-total-knee-arthroplasties (rTKA) are common, and the clinical significance is not entirely clear. In contrast, in some presumably septic rTKA, an identification of an underlying pathogen was not possible, so called unexpected-negative-intraoperative-cultures (UNIC). The purpose of this study was to evaluate alpha defensin (AD) levels in these patient populations. Methods. In this retrospective analysis of our prospectively maintained biobank, we evaluated synovial AD levels from 143 rTKAs. The 2018-Musculoskeletal Infection Society score (MSIS) was used to define our study groups. Overall, 20 rTKA with UPIC with a minimum of one positive intraoperative culture with MSIS 2-≥6 and 14 UNIC samples with MSIS≥6 were compared to 34 septic culture-positive samples (MSIS ≥6) and 75 aseptic culture-negative (MSIS 0–1) rTKAs. Moreover, we compared the performance of both AD-lateral-flow-assay (ADLF) and an enzyme-linked-immunosorbent-assay (ELISA) to test the presence of AD in native and centrifuged synovial fluid. Concentration of AD determined by ELISA and ADLF methods, as well as microbiological, and histopathological results, serum and synovial parameters along with demographic factors were considered. Results. AD was detected in 31/34 (91.2%) samples from the infected-group and in 14/14 (100%) samples in the UNIC group. All UPIC samples showed a negative AD result. Positive AD samples were highly (p<0.001) associated with culture positive and infection related histopathological results. Moreover, we found significantly (p=0.001) more high-virulent microorganisms 19/34 (55.9%) in the infected-group compared to the UPIC-group (0/20). Samples from the infected group with high virulent microorganisms 17/19 (89.5%) showed a positive AD. The presence of methicillin resistant Staphylococcus epidermis (MRSE) led to increased AD (p=0.003) levels when compared to those determined in samples positive for methicillin susceptible S. epidermdis (MSSE). ELISA and ADLF tests were positive with centrifuged (8/8) and native (8/8) synovial fluid. Conclusion. AD showed a solid diagnostic performance in infected and non-infected revisions, and it provided an additional value in the diagnostic of UPIC and UNIC associated to rTKAs. AD levels produced by patients with PJIs caused by high-virulent microorganisms and MRSE are significantly higher compared to those in patients with PJIs caused by either low-virulent or antibiotic susceptible microorganisms. Centrifugation of synovial fluid had no influence in the outcome of ADLF quantification. Keywords: Alpha-defensin, UPIC, UNIC, revision-knee-arthroplasty

It is strongly recommended that tissue and synovial fluid culture samples be obtained during reimplantation performed as part of a two-stage exchange arthroplasty. The incidence of positive cultures during reimplantation and the influence of positive cultures on subsequent outcome are unknown. This aim of this study was to determine the incidence of positive cultures during reimplantation and to investigate the association between positive cultures at reimplantation and the subsequent outcome. A retrospective review was conducted on 267 patients that met the Musculoskeletal Infection Society (MSIS) criteria for PJI that completed both stages of two-stage exchange arthroplasty (Table 1). Intraoperative culture results from tissue and/or synovial fluid were obtained. Cultures were positive in 33 cases (12.4%) undergoing reimplantation surgery (Figure 1). Treatment failure was assessed based on the Delphi consensus definition. Logistic regression analysis was performed to assess the predictors of positive culture and risk factors for failure of two-stage exchange arthroplasty. Treatment failure was 45.5% for those with a positive intraoperative culture and 20.9% in those with negative cultures at the time of reimplantation. When controlling for organism virulence, comorbidities, and other confounding factors, treatment failure was higher (odds ratio [OR]: 3.3; 95% confidence interval [CI]: 1.3–4.5) and occurred at an earlier time point (hazard ratio: 2.5; 95% CI: 1.3–4.5) in patients with a positive reimplantation culture. The treatment failure rate was not different between cases with two or more positive cultures (36.4%) and one positive culture (42.8%). Positive intraoperative cultures during reimplantation, regardless of the number of positive samples were independently associated with two times the risk of subsequent infection and earlier treatment failure. Surgeons should be aware that a positive culture at the time of reimplantation independently increases the risk of subsequent failure and needs to be taken seriously. Given the significance of these findings, future studies are needed to evaluate the optimal management of positive cultures during reimplantation surgery

Aim. A two-stage exchange of an infected prosthetic joint (PJI) is considered the most effective surgical treatment of chronic PJIs, particularly in North America. However, reinfection rates are unacceptably high (10–20%). This could be the consequence of a persistent infection or a new infection introduced during the first or second stage of the exchange arthroplasty. We aimed to determine: i) the prevalence of positive cultures at reimplantation, ii) whether there is an association between positive cultures at reimplantation and reinfection during follow-up, and iii) if there is a microbiological correlation between primary infections, reimplantations and reinfections. Method. We retrospectively evaluated all two-stage exchange procedures performed at two academic centers between 2000 and 2015. Primary culture-negative PJIs and cases in whom no intraoperative cultures were obtained during reimplantation were excluded from the analysis. One or more positive intraoperative cultures during reimplantation were considered positive for infection. Reinfection was defined as the need for additional surgical intervention after reimplantation or the need for antibiotic suppressive therapy due to persistent clinical signs of infection. Results. A total of 424 cases were included in the final analysis with a mean follow-up of 48 months (SD 37). Eighty-eight cases (20.8%) had positive cultures during reimplantation (second stage) of which 68.1% (n=60) grew a different microorganism than during the first stage of the procedure. The percentage of positive cultures during reimplantation was higher for hips than for knees (26.5% vs 17.1%, p 0.02). For the total group, the reinfection rate during follow-up was 18.4% (78/424), which was 29.5% for the positive-culture group versus 15.5% for the culture-negative group at reimplantation (p=0.002). A positive culture during reimplantation was an independent risk factor for reinfection during follow-up in the multivariate analysis (OR 2.2 (95% CI 1.2 – 3.8), p 0.007). Reinfection was caused by a different microorganism than the primary infection (first stage) in 64.1% of cases (50/78). Conclusions. There is a very high rate of positive cultures at reimplantation, which are mostly attributed to a different microorganism than the primary infection and is associated with a worse outcome. These results stress the importance of developing treatment strategies for this particular population

Aim. The purpose of this study was to report on outcomes after stabilization of large skeletal defects following radical debridement of hip or knee infections and staged reimplantation using segmental antibiotic mega-spacers. Method. From 1998–2018, 39 patients (18 male, 21 female) were treated for musculoskeletal infections at the hip (14) or knee (25). Patients were treated for infection after a procedure related to oncology (20), arthroplasty (16), or trauma (3). Following debridement, defects were stabilized with antibiotic impregnated PMMA and intramedullary nails. All patients underwent a standardized protocol: 6 weeks of intravenous antibiotics followed by 6 weeks of oral antibiotics guided by intraoperative cultures. After a 6-week holiday of antibiotics, repeat intraoperative cultures and inflammatory markers were analysed for infection resolution. Success was defined by reimplantation without additional infection-related complications or requirement of suppressive antibiotics at latest follow-up. Results. Mean age was 50.5±19.4 years. Mean defect size was 20.4cm. Mean time from surgery until infection was 34.5 months, with 74% of patients presenting with infection greater than one year after their most recent surgery. Mean follow-up was 110±68 months. Most common organisms of infection were Staphylococcus Epidermidis (11) and Staphylococcus Aureus (10). Mean defect size was significantly different among oncology (28±8 cm), trauma (19±5 cm) and arthroplasty (12±6 cm) patients (p<0.0001), though outcomes were comparable. Two patients with antibiotic spacers have not underwent attempted reimplantation – one patient with clinical and laboratory signs of resolved infection; one patient with recent spacer placement. One patient died of oncologic disease shortly after spacer placement. These three patients were excluded from outcomes analysis. Twenty-nine (81%) patients were successfully re-implanted with a segmental endoprosthesis. Eight patients required an additional procedure prior to infection resolution, including additional antibiotic spacer and debridement due to sustained inflammatory markers and clinical signs of infection (5), antibiotic spacer exchange due to mechanical failure (2), and polyethylene exchange 9 months after reimplantation (1). Two patients have remained on chronic suppressive antibiotics, but have retained their limb, prosthesis, and pain-free function. Four (11%) patients ultimately required an amputation for infection control (3 above knee amputations; 1 hip disarticulation). Conclusions. Following radical debridement for infection, staged management of large segmental defects at the hip and knee with antibiotic cement and temporary intramedullary stabilization results in an 81% success-rate of limb salvage with infection control

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

Aim. Currently, gram-negative bacteria (GNB), including multidrug-resistant (MDR-GNB) pathogens, are gaining importance in the aetiology of prosthetic joint infection (PJI). To characterize the antimicrobial resistance patterns of Gram-negative bacteria (GNB) causing hip prosthetic joint infections in elderly patients treated at a Brazilian tertiary academic hospital. Method. This is a retrospective, cross-sectional study of patients over 60 years of age undergoing hip arthroplasty from 2018 to 2023 at a tertiary academic trauma, which were diagnosed with hip prosthetic joint infection. PJI diagnosed was based on EBJIS criteria, in which intraoperative tissue cultures identified the pathogens. Demographics, reason for arthroplasty, type of implant and susceptibility patterns using disk diffusion method were analysed. Results. Overall, among 17 elderly patients diagnosed with hip infected arthroplasty, 45 bacterial isolated were identified. Debridement, irrigation, antibiotic and implant retention (DAIR) procedures due to uncontrolled infection occurred in 47.0% (n=8/17), and five patients underwent more than two DAIR surgeries. Tissue cultures yielded eleven different bacterial species, with GNB accounted for 64.4% (n=29/45) of pathogens. Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, and Pseudomonas aeruginosa were identified in 34.5% (n=10/29), 17.25% (n=5/29), 13.8% (n=4/29), and 13.8% (n=4/29), respectively. In the resistance profile analysis, E. coli was most sensitive to antibiotics, whereas K. pneumoniae showed resistance rates higher than 70% for cephalosporins, carbapenems, and quinolones. All A. baumannii isolates were resistant to meropenem, and 80% of these isolates were resistant to amikacin. Conclusions. This study emphasizes the role of GNB in the microbiological profile of PJI among elderly patients at a tertiary hospital in a Brazilian centre. The present study portrays a worryingly higher rates of MDR-GNB, mainly to quinolones and cephalosporins resistance which have been the cornerstone of PJI antibiotic treatment. In addition, higher rates carbapenems and aminoglycosides resistance shows a threat to antibiotic treatment of PJI. More global studies need to be carried out to show a likely change in the microbial epidemiology of PJI

Aim. Periprosthetic joint infection (PJI) is a serious complication after joint arthroplasty. Diagnosing PJI can be challenging as preoperative screening and conventional cultures may be inconclusive. Sonication fluid culturing stands out as a valuable adjunct technique to improve microbiological PJI diagnosis. This study aims to determine the clinical relevance of routinely using sonication for all septic and aseptic revisions. Method. All patients who underwent (partial) hip or knee revision arthroplasty for all causes between 2012 and 2021 at our institution were retrospectively reviewed. Based on the European Bone and Joint Society PJI criteria, we categorized them into three groups: infection confirmed, infection likely, and infection unlikely. We analyzed the clinical, laboratory, and radiological screening that could confirm or refute suspicion of PJI. We analyzed microbiology cultures and the most frequently detected microorganisms. Sensitivity and specificity were calculated for synovial fluid cultures (preoperative), tissue cultures, and sonication fluid cultures. We determined the clinical relevance of sonication as the percentage of patients for whom sonication confirmed (microbiological) PJI diagnosis. Results. 429 patients who underwent (partial) revision of hip (246 patients) or knee (183 patients) arthroplasty were included. Sensitivity and specificity were 69% and 99% for preoperative synovial fluid cultures, 76% and 92% for intraoperative tissue cultures, and 80% and 89% for sonication fluid cultures, respectively. Sonication fluid cultures improved tissue culture sensitivity and specificity to 83% and 99%, respectively. In 12 (11%) out of 110 PJIs, sonication fluid cultures were decisive for confirming the causative pathogen. This was applicable to acute and chronic infections. In 29 (9%) out of 319 aseptic cases, a negative sonication fluid culture could confirm contamination of tissue cultures. Conclusions. Routine sonication fluid cultures enhanced the sensitivity and specificity of PJI diagnostics. In 11% of PJI cases, causative pathogens were confirmed by sonication fluid culture results. Routine sonication may be helpful in confirming contamination of synovial fluid cultures and tissue cultures. Routine sonication fluid culture should be performed in all revision arthroplasties

Culture negative prosthetic joint infections (PJI) still remain an issue even the advantages in PJI diagnosis. This is the reason why some orthopedic surgeons fear to use preoperative antibiotic prophylaxis when a PJI is suspected. The purpose of the present study was to evaluate the influence of preoperative antibiotic prophylaxis in intraoperative cultures. An enhanced diagnostic protocol for PJI (Zimmerli criteria) was used for the inclusion criteria in order to collect all PJI accounted in a University Hospital. Patients were prospectively randomized in two groups. The control group received the classical preoperative antibiotic prophylaxis. The study group did not receive prophylaxis prior to surgery. There were 14 patients in each group. They correspond to 13 infections of total hip arthroplasty (THA), 12 infections of total knee arthroplasty (TKA) and 3 reverse shoulder prosthesis (RSA) infections. There were 10 patients in the study group and 10 patients in the control group with at least one positive microbiological criterion. There were 8 patients in each group with culture negative PJI (p>0.05). Preoperative antibiotic prophylaxis does not affect intraoperative cultures in suspected or confirmed PJI. Therefore it is essential to deliver antibiotic prophylaxis in any patient in which prosthesis is to be implanted in order to protect the prosthesis from infection