Aim. Periprosthetic Joint Infection (PJI) is a devastating complication in hip and knee joint arthroplasty. The “JS BACH” classification system was developed in 2021 to stratify the complexity of PJI, and more importantly, to act as a tool to guide referrals to specialist centers. The “JS BACH” classification has not been validated in an external cohort. This study aimed to do so using a large prospective cohort from Australia and New Zealand. Method. We applied the JS-BACH classification to the Prosthetic Joint Infection in Australia and New Zealand Observational (PIANO) cohort. This prospective study of newly diagnosed PJI collected 2-year outcome data from 653 participants enrolled in 27 hospitals. The definition of PJI treatment failure at 24 months was any of the following: death, clinical or microbiological signs of infection, destination prosthesis removed, or ongoing antibiotic use. Results. Individual cases were classified as per JS-BACH into “1 - uncomplicated” (n = 268), “2 - complex” (n = 330), and “3 - limited options” (n = 55). This cohort was similar to the original JS-BACH population in terms of baseline characteristics. However, there was a difference in complexity, with more DAIR procedures, fewer revision procedures, and a higher proportion of uncomplicated patients in the PIANO cohort. The risk of treatment failure correlated strongly with the JS-BACH category, with odds ratios (95% CI [confidence interval]) for category 2 versus 1 of 1.75 (1.24 to 2.47) and for category 3 versus 1 of 7.12 (3.42 to 16.02). Conclusions. Despite the PIANO study population being less complicated than the original derivation cohort, the JS-BACH classification showed a clear association with treatment failure in this large external cohort

Aim. This retrospective study evaluated the outcome of treatment for unhealed fracture-related infections (FRI). Methods. We identified a consecutive, single-centre cohort of patients having treatment for an FRI Consensus confirmed FRI. All fractures were unhealed at the time of treatment. Patients were followed up for at least one year. Successful outcome was a healed fracture without recurrent infection. Lack of union, persistent infection and/or unplanned reoperation defined failure. Results. Demographics: 183 patients (184 FRIs) with mean age 52.1 years (range 17-96) were treated and followed up for a mean of 2.8 years (range 1-9.4). Mean duration of FRI was 1.1 years with 65 (35.5 %) presenting within 6 months of injury. 118 patients had established infected non-union. FRI was most frequent in the tibia (74), femur (48) and humerus (24). 171 patients were BACH Complex. 75.5% of FRIs were culture positive, with Staph. aureus being the most frequent organism. Polymicrobial infection and Gram negative cultures were common (25.5% and 33.6%). Treatment: 98.3% of surgeries were performed in one stage with just 3 planned 2-stage procedures (2 endoprosthetic replacements and 1 free fibular flap). No bone graft was used in any surgery and all wounds were closed at first operation. 48 cases (26%) required flap coverage (29 free flaps and 19 local flaps). Local antibiotics were used in 124 cases (67.4%) of primary surgeries. All patients had sampling, debridement, systemic antibiotics and wound closure. 40 (21.7%) had DAIR, 31 (16.8%) had new internal fixation and 105 (57.1%) had external fixation (including 79 Ilizarov fixators). Outcomes: After primary surgery, 84.6% of all patients were infection-free and 77.2% had united. After further surgery, 98.8% were infection-free and 98.1% had united. External fixation techniques achieved infection eradication in 89.1% compared to 71.7% with any internal fixation (p=0.005). Primary internal fixation achieved union in 81.7% compared to 74.3% with external fixation (p=0.27). Secondary surgery after external fixation was mainly docking site fixation. Conclusion. Unhealed FRIs present a difficult challenge for treatment. This large series demonstrated that single-stage treatment, without bone grafting, gave acceptable results with few reoperations. Primary external fixation gave more certainty of infection eradication but required more reoperations to secure union. However, this difference in reoperation was not statistically significant. We strongly advocate managing these patients with a multidisciplinary team which can treat all aspects of the condition

Aim. Periprosthetic joint infection (PJI) is one of the main reasons for revision surgery after primary unicompartmental knee arthroplasty (UKA), total knee arthroplasty (TKA) or total hip arthroplasty (THA). Currently the MSIS and EBJIS criteria sets are considered to be the gold standards in determining PJI. These criteria sets are complex and contain tests that are time-consuming and many are rather costly. Therefore, further research is indicated to find a simpler but equally reliable diagnostic test. In this study we evaluated the additional value of calprotectine measurement in synovial fluid in patients undergoing hip and knee (revision) arthroplasty following routine work-up. Method. In a retrospective cohort study, we analyzed 182 synovial fluid samples from 143 patients with suspected PJI after UKA, TKA, THA or revision arthroplasty. Twenty-six of those cases were classified as PJI according to the MSIS and EBJIS criteria. Subsequently, synovial calprotectin was determined, using a lateral flow assay and two cut-off thresholds of ≥14 mg/L and ≥50 mg/L. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of synovial calprotectin was determined. Results. When applying the MSIS and EBJIS criteria and a calprotectin level ≥14 mg/L, synovial calprotectin revealed an area under the curve of 0.96 (95% CI 0.90-1.00), with 92.3% sensitivity and 100% specificity. The PPV and NPV were 100% and 92.9% respectively. When applying the MSIS and EBJIS criteria and a calprotectin level ≥ 50 mg/L, synovial calprotectin revealed an area under the curve of 0.94 (95% CI 0.87-1.00), with 88.5% sensitivity and 100% specificity. The PPV and NPV were 100% and 89.7% respectively. Conclusions. The value of calprotectin in synovial fluid gives valuable information with a single test result, resulting in high predictive value in the diagnosis of PJI after hip or knee arthroplasty and should seriously be considered as part of PJI diagnostics in an outpatient clinical setting. The high specificity can help rule in patients that are suspected of PJI. Therefor this test can be helpful in a preop diagnostic work-up to avoid unnecessary revisions in patients with well-placed and well-fixed arthroplasties with a suspected PJI. These conclusions are independent of which criteria set was used as a gold standard

Aim. The current recommendation in Norway is to use four doses of a first-generation cephalosporin (cefazolin or cephalotin) as systemic antibiotic prophylaxis (SAP) the day of surgery in primary joint arthroplasty. Due to shortage of supply, scientific development, changed courses of treatment and improved antibiotic stewardship, this recommendation has been disputed. We therefore wanted to assess if one dose of SAP was non-inferior to four doses in preventing periprosthetic joint infection (PJI) in primary joint arthroplasty. Method. We included patients with primary hip- and knee arthroplasties from the Norwegian Arthroplasty Register and the Norwegian Hip Fracture Register for the period 2005-2023. We included the most used SAPs (cephalotin, cefazolin, cefuroxime, cloxacillin and clindamycin), administered as the only SAP in 1-4 doses, starting preoperatively. Risk of revision (Hazard rate ratio; HRR) for PJI was estimated by Cox regression analyses with adjustment for sex, age, ASA class, duration of surgery, reason for- and type of arthroplasty, and year of primary arthroplasty. The outcome was 1-year reoperation or revision for PJI. Non-inferiority margins were calculated for 1, 2 and 3 doses versus reference of 4 doses of SAP at the day of surgery, against a predetermined limit of 15% increased risk of PJI. Results. In total 274,188 primary arthroplasties (total hip 133,985, hemi hip 51,442, and total knee 88,761) were included. Of these primary arthroplasties, 2,996 (1.1%) had subsequent revisions for PJI during the first postoperative year. One dose of SAP was given in 9,603 arthroplasties, two doses in 10,068, three doses in 18,351, and four doses in 236,166 arthroplasties. With the recommended four doses as reference, the HRR (95% CI) for 1-year revision for infection was 0.9 (0.7-1.1) for one dose, 1.0 (0.8-1.2) for two doses, and 0.9 (0.8-1.1) for three doses. The corresponding adjusted 1-year revision incidences for PJI was 0.9 (0.7-1.1), 1.0 (0.8-1.2), 0.9 (0. 8-1.1) and 1.0 (1.0-1.1) for one, two, three and four doses respectively, and less than four doses was found to be non-inferior. Conclusions. One preoperative dose of SAP in primary joint arthroplasty surgery seems to be non-inferior to the current recommendation of four doses of a first-generation cephalosporin as PJI-prophylaxis. This finding may simplify the course of treatment for arthroplasty patients, save costs, and improve antibiotic stewardship

Introduction. Since the expanded war in Ukraine in 2022, explosives, mines, debris, blast waves, and other factors have predominantly caused injuries during artillery or rocket attacks. These injuries, such as those from shelling shrapnel, involve high-energy penetrating agents, resulting in extensive necrosis and notable characteristics like soft tissue defects and multiple fragmentary fractures with bone tissue defects and a high rate of infection complications caused by multi resistant gram-negative (MRGN) pathogens. Material and Methods. We conducted a prospective study at our center between March 2022 and December 2023. Out of the 56 patients from Ukraine, 21 met the inclusion criteria who had severe war injuries were included in the study. Each of these patients presented with multiple injuries to both bones and soft tissues, having initially undergone treatment in Ukraine involving multiple surgeries. The diagnosis of infection was established based on the EBJIS criteria. Prior to our treatment patients had undergone multiple revision surgeries, including debridement, biopsies, implant and fixator replacement. Additionally, soft tissue management required previously VAC therapy and flap reconstruction for successful treatment. Results. All 21 infections manifested as bone infections (11; 52%), followed by implant-associated infections (5; 24%), soft tissue infections (4; 19%), and septic arthritis (1; 5%). In all patients, the infection was polymicrobial, caused by 3- and 4-MRGN pathogens, as Klebsiella pneumonia 4MRGN, Proteus mirabilis 4MRGN, Enterobacter cloacae 4MRGN etc. Upon admission, all patients carried a diagnosis and exhibited signs indicative of chronic infection. 19 (90.5%) patients required complex antibiotic regimens combined with multiple wound revisions and debridements, changes of fixators and combination of systemic and local antibiotic therapy. In 6 patients (28%) high dosages of local antibiotics such as gentamycin, vancomycin and meropenem were incorporated into a carrier of bio-absorbable calcium sulfate, calcium sulfate/hydroxyapatite which were introduced into the hip joint, femoral canal or bone defect for dead space management during the surgery. When local antibiotics were administered at intervals, the microbiology results at implantation showed negative results. 2 (9%) patients had new infections (different site, different pathogens), 1 (4.8%) is still under the treatment. In 17 (81%) patients infection complications were treated successfully with no recurrence of infection. Conclusion. War injuries result in complex bone and soft-tissue infections caused by 3-, 4-MRGN pathogens. Addressing this challenge necessitates multidisciplinary approach with multiple, thorough surgical debridements, effective local, and systemic antimicrobial therapy. As for the outlook we can see potential in local antibiotic carriers

Aim. Periprosthetic joint infection (PJI) and periprosthetic fracture (PF) are one of the most devastating complications in arthroplasty. Each complication by itself is challenging to solve. Yet, simultaneously, both complications are inconceivably complex to deal with, while the treatment regimen of PJI and PF are contradictory. Chronic PJI most often requires implant removal, while PF requires stability, regularly achieved by stable osteosynthesis. This study aims to (1) analyse the success rate of PJI with following concomitant PF during the treatment course in total hip arthroplasties (THA) and (2) to determine the risk factors for reinfection and subsequent revision surgery after treatment of PJI and PF. Method. This restrospective study analyzed 41 patients with concomitant PJI and PF during the PJI treatment period from 2013 to 2022 involving THA. Patients were divided in two cohorts termed success and failure and were statistically compared. The median follow-up time was 66 months (>12 months). All patients were considered individually and treated according to their individual needs in fracture and infection treatment. Re-arthroplasty survival was analyzed using the Kaplan-Meier method. Relevant risk factors were analyzed using the Mann-Whitney test or Chi-square, depending on the variable's scale. Results. The overall success rate of our cohort was 70,7%. Twelve patients required re-operation due to reinfection, resulting in a cumulative 12-month-reinfection rate of 19,5%. The estimated cumulative reinfection free survival rate was 68,3%. Significance in risk factors for failure were found in pathogen virulence grade, Difficult to treat pathogen and number of debridement during interval. On average the Harris Hip score was 66 in the group of reinfection compared to 77 in the group of success. Conclusions. Reoperation and re-infection rate remains high in patients with simultaneous PJI and PF in THA. Due to the heterogeneity of the fractures, soft tissue conditions and pathogens found, treatment must be individualised to salvage the limb. However, small cohorts impact the statistical strength negatively due to instances of two rare complications

Aim. Decubitus ulcers are found in approximately 4.7% of hospitalized patients, with a higher prevalence (up to 30%) among those with spinal cord injuries. These ulcers are often associated with hip septic arthritis and/or osteomyelitis involving the femur. Girdlestone resection arthroplasty is a surgical technique used to remove affected proximal femur and acetabular tissues, resulting in a substantial defect. The vastus lateralis flap has been employed as an effective option for managing this dead space. The aim of this study was to evaluate the long-term outcomes of this procedure in a consecutive series of patients. Method. A retrospective single-center study was conducted from October 2012 to December 2022, involving 7 patients with spinal cord injuries affected by chronic severe septic hip arthritis and/or femoral head septic necrosis as a consequence of decubitus ulcers over trochanter area. All patients underwent treatment using a multidisciplinary approach by the same surgical team (orthopedic and plastic surgeons) along with infectious disease specialists. The treatment consisted of a one-stage procedure combining Girdlestone resection arthroplasty with unilateral vastus lateralis flap reconstruction, alongside targeted antibiotic therapy. Complications and postoperative outcomes were assessed and recorded. The mean follow-up period was 8 years (range 2-12). Results. Of the 7 patients, 5 were male and 2 were female, with a mean age of 50.3 years at the time of surgery. Minor wound dehiscence occurred in 28.6% of the flap sites, and 2 patients required additional revisional procedures—one for hematoma and the other for bleeding. There were no instances of flap failure, and complete wound healing was achieved in an average of 32 days (range 20-41), with the ability to load over the hip area. No cases of infection recurrence or relapse were observed. Conclusions. An aggressive surgical approach is strongly recommended for managing chronic hip septic arthritis or proximal femur osteomyelitis in patients with spinal cord injuries. A single-stage procedure combining Girdlestone resection arthroplasty with immediate vastus lateralis muscle flap reconstruction proves to be an effective strategy for dead space management and localized antibiotic delivery through the vastus muscle, giving reliable soft tissue coverage around the proximal femur to avoid the recurrence of pressure ulcers. The implementation of a standardized multidisciplinary protocol contributes significantly to the success of reconstruction efforts

Aim. Periprosthetic joint infections follow 1-3% of arthroplasty surgeries, with the biofilm nature of these infections presenting a significant treatment challenge. 1. Prevention strategies include antibiotic-loaded bone cement; however, increases in cementless procedures means there is an urgent need for alternative local antimicrobial delivery methods. 2. A novel, ultrathin, silica-based sol-gel technology is evaluated in this research as an anti-infective coating for orthopaedic prosthetic devices, providing local antibiotic release following surgery. Method. Reduction in clinically relevant microbial activity and biofilm reduction by antimicrobial sol-gel coatings, containing a selection of antibiotics, were assessed via disc diffusion and microdilution culture assays using the Calgary biofilm device. 3. Proliferation, morphology, collagen, and calcium production by primary bovine osteoblasts cultured upon antibiotic sol-gel surfaces were examined, and cytotoxicity evaluated using Alamar blue staining and lactate dehydrogenase assays. Concentrations of silica, calcium and phosphorus compounds within the cell layer cultured on sol-gel coatings and concentrations eluted into media, were quantified using ICP-OES. Furthermore, cellular phenotype was assessed using alkaline phosphatase activity with time in culture. Results. Low antibiotic concentrations within sol-gel had an inhibitory effect on clinically relevant biofilm growth, for example 0.8 mg ml. -1. tobramycin inhibited clinically isolated S. aureus (MRSA) growth with an 8-log reduction in viable colony forming units. There was no significant difference in metabolic activity between untreated and sol-gel exposed primary bovine osteoblasts in elution-based assays. Reduction (2-fold) in metabolic activity in direct contact assays after 48 hours exposure was likely to be due to increased osteoinduction, whereas no impact upon cell proliferation were observed (p=0.92 at 14 days culture). The morphology of primary osteoblasts was unaffected by culture on sol-gel coatings and collagen production was maintained. Calcium containing nodule production within bovine osteoblastic cells was increased 16-fold after 14 days culture upon sol-gel. Conclusions. The ultrathin sol-gel coating showed low cytotoxicity, strong biofilm reducing activity and antimicrobial activity, which was comparable to antibiotics alone, demonstrating that sol-gel delivery of antibiotics could provide local antimicrobial effects to inhibit PJI growth without the need for bone cement. Future work will develop and evaluate sol-gel performance in an ex vivo explant bone infection model which will reduce the need for animal experimentation

Aim. There is limited data on the frequency and impact of untoward events such as glove perforation, contamination of the surgical field (drape perforation, laceration, detachment), the unsterile object in the surgical field (hair, sweat droplet…), defecation, elevated air temperature…that may happen in the operating theatre. These events should influence the surgical site infection rate but it is not clear to what extent. We wanted to calculate the frequency and measure the impact of these events on the infection and general revision rate. Method. In our institution, scrub nurses prospectively and diligently record untoward events in the theatres. We have an institutional implant registry with close to 100% data completion since 2001, and surgeons register complications before discharge. We analysed the respective databases and compared the revision and infection rate in the group with untoward events with the outcome of all arthroplasty patients within the same period. Two-tailed Z statistical test was used for analysis. Results. Between 1.1.2012 and 31.12.2018 we operated 13574 prosthetic joints: 6232 primary THR (total hip replacement) and 5466 primary KR (total and partial knee replacement) and 1245 and 631 revisions respectively. During this period, we recorded 372 events (2.74%) including 20 (0.15 %) defecations, 40 (0.29 %) unsterile object in the surgical field, 73 (0.54%) field sterility violations, 45 (0.33 %) glove perforations, 45 (0.33 %) occasions with elevated air temperature, 106 (0.78%) with guests in the OR, 11 (0.08%) with wound near the surgical field, and 32 (0.24%) with other events. We followed the patients till 1.1.2022, in this time we recorded 27 (7.26%) reoperations in the cohort with untoward events. There were 9 (2.42%) infections and 18 (4.84%) aseptic revisions in the group with unwanted events. The infection rate for all TJR (total joint replacement) from the period 2012-2018, followed till 1.1.2022 was 2.23%, the revision rate for any reason was 4.37%. For all THR (primary and revision) the infection rate was 0.84%, the overall revision rate was 3.18% and for the KR (primary and revision) 1.71% and 5,82% respectively. The difference is significant at p>0.05 for infection rate. Conclusions. The potentially serious sterility disruptive events in the operative rooms did result in an increased infection rate but not an increase in revision rate. There is no data about the rate and the impact of these events besides for perforated surgical gloves with higher reported incidences than in our study influencing infection rate if perioperative antibiotic prophylaxis was not used. Ours is the first study reporting the impact of these unwanted events in the operating theatre. Key words. orthopaedic surgery, unwanted events, revision rate

Aim. Cutibacterium acnes is a major skin commensal that may also act as an opportunistic pathogen. Findings of C. acnes in tissue cultures obtained during arthroplasty revision surgery are difficult to interpret, since they may represent true infection or contamination. This study investigated whether C. acnes isolates obtained from prosthetic joint infections (PJIs) were related and shared common genomic traits that might correlate with clinical courses and patient outcomes. Method. C. acnes isolates from revision surgery of patients with PJIs of the hip, shoulder, and knee were characterized using molecular methods to determine sequence type (ST) and the presence of virulence determinants (CAMP factors, dermatan sulfate-binding adhesion 1, hyaluronidase lyase, and linear plasmid). A standardized review of the patients’ medical charts was performed. Results. The study included 37 patients with C. acnes culture-positive tissue samples where multiple isolates of C. acnes belonged to the same ST. Most of the isolates belonged to phylotype IA. 1. Phylogenetic analysis of virulence determinants revealed no shared pattern among PJI isolates. Seven patients had a polymicrobial infection. Exchange revision was performed in 70% of the patients, and >50% of all patients received antibiotic treatment for ≥3 months. Failure was noted in seven patients, all of whom had shoulder PJIs. Conclusions. No specific ST or any identifiable unique feature among virulence determinants were found among C. acnes isolated from PJIs of hips and shoulders. The majority of all included patients had low inflammatory markers and were treated successfully, even when the infection consisted of a polymicrobial infection

Aim. Predicting success of a Debridement, Antibiotics and Implant Retention (DAIR) procedure for Periprosthetic Joint Infection (PJI) remains a challenge. A failed DAIR might adversely affect the outcome of any future revision surgery for PJI. Hence, the ability to identify and optimise factors predictive of DAIR success would help target the procedure to the appropriate patient cohort and avoid unnecessary surgery for patients where a DAIR is unlikely to eradicate infection. Method. A retrospective review of our prospective Bone Infection Group database was performed to identify all patients who underwent a DAIR of their hip or knee arthroplasty. Diagnosis of PJI was confirmed using the Musculoskeletal Infection Society (MSIS) 2013 and the European Bone and Joint Infection Society (EBJIS) 2021 classification systems. DAIR surgery was grouped into “successful” or “unsuccessful” outcomes as per the MSIS working group outcome-reporting tool. Results. Sixty-Four consecutive patients with an acute PJI underwent a DAIR procedure between 2009 and 2020. Treatment was successful in 44 (69%). The chance of a successful DAIR was significantly greater if performed within one week of symptom onset compared to greater than one week duration (adjusted odds ratio (OR 0.11; p=0.027; 95% CI [0.02- 0.78]). The chances of a successful DAIR was not influenced by whether the surgeon was an arthroplasty or non-arthroplasty surgeon (OR 0.28; p=0.13; 95% CI [0.05- 1.48]). Isolated Streptococcus infection had a success rate of 100%; followed by Coagulasenegative Staphylococci 71% and Methicillin-susceptible Staphylococcus Aureus 65%. Polymicrobial infection had the worst outcome with a success rate of 47%. Conclusions. In our experience DAIR surgery performed within one week of symptom onset, significantly increased chances of successful infection eradication. Collaborative work is required to ensure arthroplasty patients access prompt appropriate surgical decision-making, remove barriers to early assessment and minimise delays to surgery

Aim. Swedish guidelines on antibiotic prophylaxis in arthroplasty surgery recommend cloxacillin in fixed doses that pay little attention to the patient's renal function and weight. Nevertheless, there are no studies on whether the resulting free prophylactic cloxacillin in vivo concentrations are optimal. We aimed to evaluate whether the current recommended prophylactic dosage of cloxacillin is adequate. Method. We performed a prospective two-centre study, measuring the free (active) cloxacillin concentrations in plasma throughout surgery, in patients subject to primary hip and knee prosthetic joint replacements, aiming at 100 patients per centre. To account for plasma-bone exposure differences, concentrations were considered adequate if twice the epidemiological cut-off value for cloxacillin concerning wild type Staphylococcus aureus whereas two-three times were labelled threshold values. The two enrolling hospitals are acute care hospitals in central Sweden, also performing 600 - 1200 primary hip and knee joint arthroplasties annually. All patients scheduled for elective primary hip or knee replacements from January 2022 to April 2024 were eligible for participation. Exclusion criteria were allergy towards penicillins, cognitive disorders leading to inability to sign informed consent, and an absence of interpreter in case of a patient not speaking Swedish or English. Results. We present results from the first 49 patients included. Four patients had free cloxacillin concentrations below cut-off (8.2%). These four cases had prolonged surgeries of 77-100 minutes. An additional 5/49 (10.2%) had threshold values. Conversely 5/49 (10.2%) cases had concentrations exceeding 15 times the needed. No cases with threshold or low cloxacillin concentrations were attributable to a lack of concerning timing and dosing of cloxacillin. All concentrations were above or equal to our cut-off at the start of surgery. Eighteen percent of patients were of normal of weight (BMI 18.5- 25). Of the rest 4% were morbidly obese (BMI >40), 41% obese (BMI 30-40) and 37% overweight (BMI 25-30). Twenty seven percent (43/159) had diabetes and 45% suffered cardiac disease. Conclusions. Some patients in our cohort had insufficient active cloxacillin levels at the end of prosthetic joint surgery. Previous studies indicate that insufficient prophylactic antibiotic concentrations might lead to an enhanced risk of prosthetic joint infections. Other patients were massively overdosed, leading to unnecessary ecological effects and potentially adverse reactions. As inadequate cloxacillin concentrations were not associated with a lack of compliance to current guidelines a change in practise might be needed. Our final results may help to determine how dosing should be adjusted

Aim

Periprosthetic joint infection (PJI) is a severe complication after total joint arthroplasty. To prevent PJI, strict infection prevention measures are followed in combination with surgical antibiotic prophylaxis (SAP). To date, scientific reports concerning the optimal duration of SAP in revision arthroplasty are scarce. The aim of this multicenter open-label, randomized controlled trial in the Netherlands, is to investigate the superiority of 5 days (extended) versus a single dose of cefazolin to prevent PJI within the first year after revision arthroplasty of the hip and knee.

Aim. Periprosthetic joint infection (PJI) is one of the most devastating complications after joint replacement. It is associated with high morbidity and economic burden when misdiagnosed as an aseptic failure. Among all cases of PJI, up to 25% could yield negative cultures. Conversely, among cases of aseptic failures, up to 30% may actually be undiagnosed PJIs. In PJIs microbiological diagnosis is a key step for successful treatment. Sonication of the removed prosthesis is more sensitive than conventional periprosthetic-tissue culture, especially in patients who received antimicrobial therapy before surgery. This study aimed to compare the diagnostic value of classic sonication fluid cultures (SF-C) and sonication fluid incubation in blood culture bottle (SF-BCB). Method. Between 2016 and 2018 we analysed 160 revision procedures of joint arthroplasties. For each procedure, at least 5 microbiological and multiple histopathological samples were harvested, and explant sonication was performed which was further analysed by SF-C and SF-BCB. For SF-C classical cultivation of sonication fluid was performed. While for SF-BCB, 10 mL of sonication fluid was inoculated into aerobic and anaerobic lytic blood culture bottles. The definite diagnosis of PJI was based on the EBJIS definition. Results. Among 160 revisions, 59 PJIs were identified, 15 patients were treated with the debridement and implant retention, 7 patients with the one-stage and 35 with the two-stage exchange, remaining 2 were partial revisions. The sensitivity of SF-C and SF-BCB were 81.5% and 94.9%, respectively. The mismatch of microbe identification was observed in 5 cases. We observed positive SF-C while negative SF-BCB in 4 cases, among them having 2 positive histology. While 12 patients have negative SF-C and positive SF-BCB, among them 3 have positive and 6 negative histology. Among these 12 patients, typical low-grade microbes were identified in 9 cases (5 cases of C. acnes, 3 cases of S. epidermidis, and 1 case of S. capitis). Conclusions. The weakest point in all PJI diagnostic criteria is their sensitivity. SF-BCB demonstrates higher sensitivity in diagnosing PJI compared to SF-C. Therefore, it appears prudent to incorporate SF-BCB into the diagnostic protocol for all patients exhibiting either low-grade PJI symptoms or experiencing undiagnosed, presumably aseptic failures, where the likelihood of misdiagnosing infection is greatest

Aim. The utilization of silver as an anti-infective agent is a subject of debate within the scientific community, with recurring discussions surrounding its biocompatibility. Presently, galvanic silver coating finds widespread clinical application in mitigating infection risks associated with large joint arthroplasties. While some instances have linked this coating to sporadic cases of localized argyria, these occurrences have not exhibited systematic or functional limitations. To address concerns regarding biocompatibility, a novel approach has been devised for anti-infective implant coatings: encapsulating silver nitrate within a biopolymer reservoir for non-articulating surfaces. This poly-L-lactic acid layer releases silver ions gradually, thereby circumventing biocompatibility concerns. Method. Female C57BL/6 mice were utilized as an experimental model, with 6x2 mm Ti6Al4V discs, coated with or without the biopolymer-protected silver coating, implanted subcutaneously on both sides of the vertebrae. Daily blood samples were collected, and serum was analyzed for C-reactive protein (CRP) and silver concentration. After three days, histopathological analyses were conducted on the surrounding soft tissue pouch. Results. Maximum CRP levels in the silver group (4.80 mg/L; Median: 3.29 mg/L; IQR: 2.38 to 3.73) did not significantly differ from the control group (4.58 mg/L; Median: 2.93 mg/L; IQR: 1.91 to 3.78) over the study period. Silver levels in serum 24 hours post-implantation were 64 µg/L (IQR: 35 to 78) and decreased subsequently over three days to 23 µg/L (IQR: 13 to 28). Histopathological examinations revealed a similarly strong expression of inflammation signs in tissue samples from the two groups. Conclusions. Despite evidence of local inflammation indicated by CRP and histopathological analysis, no significant difference was observed between the coated and uncoated groups. This suggests that any inflammation may be attributed to the implantation procedure rather than silver influence. Furthermore, silver levels remained below the toxic limit, indicating the efficacy of the biopolymer-protected reservoir in aiding biocompatibility. This study underlines the potential of biopolymer-protected silver reservoirs in enhancing the safety profile of anti-infective silver implant coatings, warranting further investigation into their clinical application

Aim. Candida species are uncommon pathogens causing prosthetic joint infection (PJI). This study evaluated the surgical management and outcome of Candida PJI. Methods. Patients with EBJIS Definition confirmed PJI, due to Candida species, from 19 medical centres were assessed. Demographic, diagnostic, medical and surgical treatment and outcome data were collected. Results. 269 patients were recruited with follow-up for at least one year. Mean age was 70.2 years (+/- 12.4) with 10.8% being immunocompromised. The most common fungal species were C. albicans (55.8%), C. parapsilosis (29.4%), C. glabrata (7.8%) and C. tropicalis (5.6%). Co-infection with bacteria occurred in 138 (51.3%) cases. DAIR was performed in 96 (36.2%) cases, with 169 (63.8%) having implant exchange or removal (76 one-stage, 78 two-stage, 11 removal/Girdlestone arthroplasty, 2 amputation). Patient demographics and antifungal therapy were similar in all surgical groups. Overall, treatment was successful in 156 (58%) cases. Failure was more likely in older patients (>70 years; p=0.008) and those who had DAIR (OR 1.945; 1.156-3.279; p=0.004). Failure was less likely with C. parapsilosis infection compared to C. albicans (31.6% vs 48%; p=0.037). DAIR patients had more co-infection with bacteria (63.5% vs 47.4%; p=0.013) and more previous surgeries (median 4 vs 3; p=0.007), but multivariate analysis showed that these were not independent risk factors for failure. There was no difference in mortality between DAIR patients and those with other surgery (13.5% vs 17.7%; p=0.372). DAIR was successful in 45/96 (46.9%) cases compared to 110/169 (65.1%) cases with other surgery (p<0.004). Early DAIR (surgery performed <I month from implantation/infection onset) was not more effective than late DAIR (surgery performed after 1 month)(early DAIR 44.4% cure vs 63.9% cure in late DAIR; p=0.004). Two-stage revision was successful in 54/78 (69.2%), which was significantly better than DAIR (p=0.003). One-stage revision was successful in 51/76 (67.1%) patients; also significantly better than DAIR (p=0.002), but equivalent to two-stage revision (p=0.777). Conclusion. DAIR was successful in less than half of patients with Candida PJI. We could not identify any subgroup which might have better outcomes with this surgical option. Interestingly, almost 90% of our patients with Candida PJI had no immunocompromise. One or two-stage revision offer a better option, if possible, and do not increase mortality

Aim. Unexpected negative-cultures (UNC) are a common diagnostic problem in periprosthetic joint infection (PJI) of the hip and knee when using culture-based methods. A novel molecular approach (MC)1 based on the identification of the vast majority of bacterial species in a single assay using species-specific bacterial interspacing region length polymorphisms and phylum-specific 16S rDNA sequence polymorphisms has demonstrated clinical utility in PJI diagnostics (1). In addition, MC provides an estimate of the leukocyte concentration in the specimen analysed. The aim of this retrospective, blinded study was to evaluate the performance of MC in identifying the microbiological content and determining the leukocyte count in synovial fluid (SF) collected from hip and knee revision arthroplasty cases with UNC. It was also assessed whether antibiotic treatment would have been changed if the result from MC had been known. Method. A total of 89 SF samples from 70 patients (43 female; 27 male) who underwent revision arthroplasty (14 hip; 75 knee) were included. Using European and Bone Joint Infection Society (EBJIS) criteria, 82 cases were classified as infected (77 UNC and 5 septic culture-positive controls), five as non-infected (aseptic culture-negative controls), and two as likely infected, but infected by clinical observation. MC was performed and evaluated together with SF parameters. Antibiotic treatment, clinical outcome, patient demographics and surgical details were analysed. Results. Overall, 29.1% (23/79) of UNC had a positive yield by MC, of which 2/23 (8.7%) had two microorganisms detected simultaneously. Of the 25 microorganisms identified by MC, 12/25 (48%) were clinically relevant after re-evaluation of the patients’ microbiological history. The microorganisms detected were 5/25 (20%) Streptococcus pneumoniae/mitis, 4/25 (16%) Staphylococcus epidermidis, 3/25 (12%) Cutibacterium acnes, 3/25 (12%) Streptococcus agalactiae, 2/25 (8%) Streptococcus bovis, 2/25 (8%) Staphylococcus aureus, and 2/25 (8%) Haemophilus parainfluenzae. The prevalence of Enterococcus faecalis, Bacteroides fragillis, Staphylococcus lugdunensis, Corynebacterium striatum among all MC results was 1/25 (4%) each species. In total, 13/23 (56%) cases were associated with patients receiving antibiotic therapy at the time of SF collection. The yield for leukocyte counts provided the molecular technique was consistently much higher in the UNC and clearly septic groups than in the clearly aseptic group. Overall, 20/61 (32.8%) patients with UNC could have been managed differently and more accurately after MC assessment. Conclusions. MC shows clinical value in the diagnosis and management of PJI with UNC. The included leukocyte count shows promising results. Acknowledgments. This work was partially funded by Inbiome

Aim

As the number of performed total hip arthroplasties (THA) and total knee arthroplasties (TKA) has increased over the years, revision surgeries are expected to increase as well. Revision surgeries are associated with a longer operating room time, prolonged length of stay (LOS), and more frequent complications. Postoperative hematomas are a major reason for wound healing disturbances and periprosthetic joint infections (PJI). We aimed to systematically assess the use and safety of a microporous polysaccharide hemosphere (MPH) in revision THA and TKA. We focused on the risk reduction of further revision surgeries in case of wound healing disorders and hematoma, transfusion of packed red blood cells (PRBC), loss of hemoglobin (hb) and mean LOS following the use of MPH.

Aim. Periprosthetic joint infection (PJI) is a devastating complication that develops after total joint arthroplasty (TJA) whose incidence is expected to increase over the years. Traditionally, surgical treatment of PJI has been based on algorithms, where early infections are preferably treated with debridement, antibiotics, and implant retention (DAIR), while late infections with two-stage revision surgery. Two-stage revision is considered the “gold standard” for treatment of chronic PJI. In this observational retrospective study, we investigated the potential role of inflammatory blood markers (neutrophil-to- lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), systemic inflammatory index (SII)], systemic inflammatory response index (SIRI), and aggregate index of systemic inflammation (AISI)) as prognostic factors in two-stage exchange arthroplasty for PJI. Method. A single-center retrospective analysis was conducted, collecting clinical data and laboratory parameters from patients submitted to prosthetic explantation for chronic PJI. Laboratory parameters (PCR, NLR, MLR, PLR, SIRI, SII and AISI) were evaluated at the explantation time, at 4, 6, 8 weeks after surgery and at reimplantation time. Correlation between laboratory parameters and surgery success was evaluated, defined as infection absence/resolution at the last follow up. Results. 57 patients with PJI were evaluated (62% males; average age 70 years, SD 12.14). Fifty-three patients with chronic PJI were included. Nineteen patients completed the two-stage revision process. Among them, none showed signs of re-infection or persistence of infection at the last available follow up. The other twenty-three patients did not replant due to persistent infection: among them, some (the most) underwent spacer retention; others were submitted to Girdlestone technique or chronic suppressive antibiotic therapy. Of the patients who concluded the two-stage revision, the ones with high SIRI values (mean 3.08 SD 1.7, p-value 0.04) and MLR values (mean 0.4 SD 0.2, p-value 0.02) at the explantation time were associated with a higher probability of infection resolution. Moreover, higher variation of SIRI and PCR, also defined respectively delta-SIRI (mean −2.3 SD 1.8, p-value 0.03) and delta-PCR (mean −46 SD 35.7, p-value 0.03), were associated with favorable outcomes. Conclusions. The results of our study suggest that, in patients with PJI undergoing two-stage, SIRI and MLR values and delta-SIRI and delta-PCR values could be predictive of favorable outcome. The evaluation of these laboratory indices, especially their determination at 4 weeks after removal, could therefore help to determine which patients could be successfully replanted and to identify the best time to replant

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