Aim. Surgical management of PJI remains challenging with patients failing treatment despite the best efforts. An important question is whether these later failures reflect reinfection or the persistence of infection. Proponents of reinfection believe hosts are vulnerable to developing infection and new organisms emerge. The alternative hypothesis is that later failure is a result of an organism that was present in the joint but was not picked up by initial culture or was not a pathogen initially but became so under antibiotic pressure. This multicenter study explores the above dilemma. Utilizing next-generation sequencing (NGS), we hypothesize that failures after two-stage exchange arthroplasty can be caused by an organism that was present at the time of initial surgery but not isolated by culture. Method. This prospective study involving 15 institutions collected samples from 635 revision total hip(n=310) and knee(n=325) arthroplasties. Synovial fluid, tissue and swabs were obtained intraoperatively for NGS analysis. Patients were classified per 2018 Consensus definition of PJI. Treatment failure was defined as reoperation for infection that yielded positive cultures, during minimum 1-year follow-up. Concordance of the infecting pathogen cultured at failure with NGS analysis at initial revision was determined. Results. Among the total cohort, 203 revisions were considered infected and 432 were aseptic (based on ICM-criteria). Of the infected cases, 157 were NGS-positive and 46 NGS-negative. Twenty-nine ICM-positive patients (29/157;18.5%) failed by reoperation with an organism confirmed on culture. In 23 of these (23/29;79.3%), the organism at failure was present on NGS at initial revision. The remaining 6 cases detected discordant organisms between initial NGS and culture at failure. Of the 432 ICM-negative patients, NGS identified microbes in 48.1% (208/432) of “aseptic” revisions, and 17 of these failed. Thirteen of the 17 failures (76.5%) were due to an organism previously detected by NGS at initial revision. Conclusion. Our collaborative findings suggest that most failures (79.3%) by infection recurrence could be attributed to an organism previously detected by NGS at index revision surgery

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

Aims. Periprosthetic fungal infections are rare and account for 1–2% of all periprosthetic joint infections (PJI). This study aims at presenting treatment details, clinical and microbiological results in a large single centre cohort. Methods. We retrospectively identified 29 patients (9 total knee replacements (TKA) and 20 total hip replacements (THA) treated for a fungal infection between 2007 and 2019. Microbiological findings, patient demographics and complications were analysed. Statistical analysis was performed using descriptive statistics; non-parametric analysis were performed using the Mann-Whitney U-Test. Infection-free survival was determined using Kaplan-Meier analysis and differences in survival were analysed using the log-rank test. The p value was set at p<0.05 with 95% confidence intervals (95% CI) provided. Results. 28% (8/29) suffered from reinfection. The reinfection-free survival probability was 65% (95% CI 45–85) after a median follow- up period of 28 months (IQR 6 – 39). With the numbers we had, we were not able to detect a difference between THA and TKA re-infections (p=0.517). Four patients underwent amputation, 3 patients had a definitive girdlestone hip and eight patients died after a median of 5 months after first-stage surgery (IQR 1–7). All patients treated had positive synovial fluid or tissue cultures for Candida species. In 22 /29 patients C. albicans, in 3 patients C. parapsilosis, in 2 patients C. glabrata and in 1 patient each C. famata, C. dubliniensis and C. gulliermondii. Polymicrobial bacterial infection was found in 86% of patients with staphylococci in 20 patients, E. coli in 2 patients, vancomycin-resistant enterococci, pseudomonas, acinetobacter and achromobacter species in 1 patient each. When investigating risk factors for reinfection, with the numbers we had we were not able to find a significant difference for patients with polymicrobial infection (p=0.974), azole-resistant Candida (p=0.491), tobacco users (p=0.175), or diabetics (p=0.54). Furthermore, median age (73 vs. 72, p=0.756) and Charlson comorbidity score (6 (interquartile range (IQR) 4–8) vs. 8 (IQR 5–10), p=0.184) were not different between the groups while on the other hand there was a trend for a higher body mass index in patients with reinfection (34 (IQR 31–38) vs. 28 (IQR 25–33), p=0.075). Conclusions. Fungal PJI is associated with poor reinfection free survival, frequent revisions, and high mortality. All infections were caused by Candida spp. in which azole-resistance most be considered when planning treatment. While polymicrobial infection complicated treatment there was no difference in survival. A higher BMI and comorbidity score might be associated with higher risk for reinfections

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

Introduction. The burden of prosthetic joint infection (PJI) in total knee arthroplasty (TKA) has been rising in line with the number of primary operations performed. Current estimates suggest an infection rate of 1–2.4%. Two-stage revision has traditionally been considered the gold standard of treatment; however, some studies suggest comparable results can be achieved with single-stage procedures. The potential advantages include less time in hospital, a single anaesthetic, reduced costs, and greater patient satisfaction. Methods. We reviewed data for 72 patients (47 males, 25 females), with a mean age of 71 years (range, 49 to 94), who underwent single-stage revision TKA for confirmed PJI between 2006 and 2016. A standardized debridement protocol was performed with immediate single-stage exchange. All cases were discussed preoperatively at multidisciplinary team (MDT) meetings, which included input from a senior musculoskeletal microbiologist. Patients were not excluded for previous revisions, culture-negative PJI, or the presence of a sinus. Results. The average length of follow-up was 8 years (range, 2 to 13). In total, 65 patients (90.3%) were infection free at most recent follow-up, with seven reinfections (9.7%). Three of these patients with recurrent infections underwent arthrodesis, two underwent re-revision, and two received long-term antibiotics following debridement and implant retention (DAIR). No amputations were undertaken. Conclusions. Single-stage revision for the infected TKA, according to a strict debridement protocol with MDT input, demonstrates reinfection rates comparable with two-stage revision procedures. This is the largest single-surgeon series to date, with extensive follow-up, and supports a growing evidence base for one-stage exchange

Aim. The aim of this study was to investigate the clinical relevance of an isolated positive sonication fluid culture (SFC) in patients who underwent revision surgery of a prosthetic joint. We hypothesized that cases with a positive SFC have a higher rate of infection and prosthesis failure during follow-up compared to controls with a negative SFC. Method. This retrospective multicentre observational study was performed within the European Study Group of Implant-Associated Infections (ESGIAI). All patients who underwent revision surgery of a prosthetic joint between 2013 and 2019 and had a minimum follow-up of 1 year were included. Patients with positive tissue cultures or synovial fluid cultures were excluded from the study. Results. 95 cases (positive SFC) and 201 controls (negative SFC) were included. There was no difference in infection and prosthesis failure during follow-up between both groups. When solely analysing patients that were not treated with antibiotics, 16% of the cases had an infection during follow-up versus 5% of the controls (P 0.046). Conclusions. Withholding antimicrobial treatment in patients with an isolated positive SFC is associated with a higher reinfection rate. Antimicrobial treatment should be considered in isolated positive SFC, especially in case of high virulent pathogens

The optimum indications for debridement, antibiotics and implant retention (DAIR) are unclear. Previous studies have demonstrated higher success rate of DAIR within one year of the primary arthroplasty. This study aimed to compare the success rate of DAIR vs revision in “early” and “late” infections to provide guidance for clinical decision making. The Prosthetic Joint Infection in Australia and New Zealand Observational (PIANO) cohort prospectively recorded PJIs between July 2014 and December 2017 in 27 hospitals. This study included PIANO patients with first time PJIs occurring after primary TKA. Treatment success was defined as the patient being alive, free from further revision and without clinical or microbiological evidence of reinfection at two years follow-up. “Early” and “late” infections were analyzed separately. Univariate analysis compared demographic and disease specific factors between the DAIR and Revision groups. Multivariate binary logistic regression identified whether treatment strategy and other risk factors were associated with treatment success in “early” and “late” infections. In 117 “early” (<1 year) infections, treatment success rate was 56% in the DAIR group and 54% in the revision group (p=0.878). No independent risk factors were associated with treatment outcome on multivariate analysis. In 134 “late” (>1 year) infections, treatment success rate was 34.4% in the DAIR group and 60.5% in the revision group (OR 3.07 p=0.006). On multivariate analysis, revision was associated with 2.47x higher odds of success (p=0.041) when compared to DAIR, patients with at least one significant co-morbidity (OR 2.27, p=0.045) or with Staphylococcus aureus PJIs (OR 2.5, p=0.042) had higher odds of failure. In “late” PJIs occurring >1 year following primary TKA, treatment strategy with revision rather than DAIR was associated with greater success. Patients with significant comorbidities and Staphylococcus aureus PJIs were at higher risk of failure regardless of treatment strategy

Septic arthritis is a therapeutic emergency with a high mortality rate (about 11%)(1). Inadequate treatment can cause permanent joint damage. Management of the septic arthritis includes prompt antibiotic treatment as well as joint-decompression and removal of purulent material(2). It is still discussed controversially and there is little evidence which surgical concept is preferable: arthroscopy with lavage and debridement or open arthrotomy with synovectomy(3,4). The aim of the study was to compare efficacy of arthroscopy and arthrotomy in patients with septic gonarthritis. We evaluated 70 consecutive patients who underwent arthroscopy or arthrotomy at our clinic, because of a bacterial monarthritis of the knee between 2002 and 2010. Our primary outcome was the early recurrence of infection (> 3 months after surgery), which made a second surgery necessary. We compared patients who suffered reinfection and those who did not, in regard to the surgery type as well as potential confounders like comorbidity (measured by Charlson comorbidity index), age, body mass index (BMI), Gächter's -, Kellgren and Lawrence - and Outerbridge classification, duration of symptoms and inflammatory parameters. Furthermore we evaluated differences of the confounders between the surgery groups. From the 70 patients 41 were treated arthroscopic and 29 with arthrotomy. In total eight patients (11.4%) had to undergo a second surgery because of early reinfection. The rate was significantly higher in patients treated with arthrotomy (n=6; 20.7%) compared to those treated with arthroscopy (n=2; 4.9%) (p=0.041). Whereas we found no significant influence of potential confounders between the reinfection group and the group where primary eradication was achieved. Patients who underwent arthrotomy were significantly older, had more comorbidities (both p<0.001) and higher grades of osteoarthritis according to Kellgren and Lawrence classification (p=0.023). In order to adjust the study population towards confounders we performed a subgroup analysis on patients of the second and third age percentile. When we repeated our analysis we still found a significant higher reinfection rate in the arthrotomy group (p=0.036). At the same time there were no differences in prevalence of confounders, neither between the two surgery groups, nor between the reinfection and the primary eradication group. Patients with bacterial monarthritis of the knee who were treated with arthroscopy had a significantly lower reinfection rate than those treated with arthrotomy. As arthroscopy is the less invasive and more sufficient method it should be considered the routine treatment according to our data

Aim. Periprosthetic joint infections are a devastating complication after modular endoprosthetic reconstruction following resection of a musculoskeletal tumour. Due to long operating times, soft tissue dissection and immunosuppression, the infection rate after limb salvage is high and ranges between 8% and 15%. The aim of this retrospective single centre study was to assess the reinfection and re-reinfection rate after septic complications of megaprostheses. Method. In this retrospective study, 627 patients with a primary replacement of a musculoskeletal tumour of the lower limb and reconstruction by a megaprosthesis were recorded from 1983 – 2016. 83 out of 621 patients available for follow-up experienced an infection (13.4%). Two patients were treated with debridement and removal of the mobile parts, 61 patients with a one-stage revision, 16 patients with a two-stage revision, and 4 patients with an amputation. The mean follow up was 133 months (range: 2 – 423 months). Results. The reinfection rates after debridement, one-stage revision, two-stage revision, and amputation were 100% (CI 95%: 20 −100%), 49% (CI 95%: 36 – 62%), 38% (CI 95%: 6 – 76%), and 0%, respectively. A reinfection occurred after a mean of 38,7 months (range: 0 to 201 months). The most commonly isolated microorganisms were coagulase negative Staphylococci, followed by Staphylococcus aureus. A re-reinfection occurred in 100% after debridement, in 44% (CI 95%: 22 – 69%) after one-stage revision, in 55% (CI 95%: 31 – 91%) after two-stage revision, and 0% after amputation. Regarding two-stage revision, there was a statistically significant difference in infection rates between patients treated with complete removal of the megaprosthesis and patients with at least one retained component (Fisher's exact test, p = 0.027). Conclusions. Septic failures after megaprosthesis reconstruction of a musculoskeletal tumour of the lower limb are difficult to treat and show high reinfection and re-reinfection rates. A two-stage revision with removal of all components showed the best results among limb salvage procedures for periprosthetic megaprosthesis infection

Aim. Two-stage replacement is a frequent procedure in patients with chronic PJI. However, results in the literature after this procedure differ, ranging from 54% to 100% of infection eradication. Positive cultures at reimplantation, when performing the second stage, are perceived as a risk factor for reinfection. This study aims to determine the impact of positive cultures during the second stage on the outcome of patients undergoing a 2-stage septic replacement and the impact of antibiotic holidays between the first and the second stage. Method. We systematically searched four databases from inception to May 31, 2022. We combined terms related to PJI, joint replacement and culture results. We analysed the risk of failure when positive cultures at second stage and performed a subgroup analysis by antibiotic holiday period. Results. We included 24 studies with 2387 patients of which 432 had positive cultures during second stage (18.09%). Global failure rate was 18.01% (430 patients). When dividing failure by culture results during second stage, we found that failure in positive group was 37.01% (161/432 patients) and failure in negative group was 13.7% (269/1953 patients). In the meta-analysis (MA) the odds ratio (OR) was 4.047 (95% CI: 2.954–5.544). When performing the subgroup analysis by antibiotic holidays we found that the rate of positive cultures without and with holidays was 21.3% and 16.05%, respectively. Failure rate without holidays was 15% (90/600 patients) and with holidays was 17.3% (202/1165 patients) (p=0.21). Failure in each group was higher when cultures were positive (without holidays, 25% vs 12.2%, p=0.0003, and with holidays 41.1% vs 12.7%, p<0.0001). In the MA we found that those studies in which antibiotic holiday was reported had higher risk of failure when cultures were positive during second stage (OR 4.798 95%IC 3.142–7.325). When studies reported no antibiotic holidays also had a higher risk of failure when cultures where positive (OR 2.225 95%CI 1.103–4.489), though it was lower. Conclusions. There exists a higher risk of failure after a two-stage septic replacement when cultures are positive during reimplantation. Patients who followed no antibiotic holidays or antibiotic holidays before reimplantation have similar failure rate when cultures are negative. In both groups they have a higher risk of failure when cultures are positive, having higher risk those positive patients in the antibiotic holidays group. Therefore, importance in detecting these patients before reimplantation is crucial to ensure higher survival rates

Aim. Patients with late acute periprosthetic joint infections (PJI) and treated with surgical debridement have a high failure rate. Previous studies have shown that rheumatoid arthritis (RA) is an independent risk factor for treatment failure. We conducted a case-control study to identify predictors for failure in late acute PJI treatment in RA patients. We hypothesize that patients with RA have a higher failure rate compared to controls due to the use of immunosuppressive drugs. Method. Data of an international multicenter retrospective observational study was used. Late acute PJI was defined as a sudden onset of symptoms and signs of a PJI, more than 3 months after implantation. Failure of treatment was defined as persistent signs of infection, relapse with the same or reinfection with a different micro-organism, need for prosthesis removal or death. Cases with RA were matched with cases without RA based on the affected joint. A Cox survival analyses, stratified for RA, was used to calculate hazard ratio's (HR) for failure. Subgroup analyses were used to explore other predictors for treatment failure in RA patients. Results. A total of 40 patients with RA and 80 controls without RA were included. Treatment failure occurred in 65% patients with RA compared to 45% for controls (p= .052). 68% of patients with RA used immunosuppressive drugs at time of PJI diagnosis. The use or continuation of immunosuppressive drugs in PJI was not associated with a higher failure rate; neither were the duration of symptoms and causative microorganism. The time between implantation of the prosthetic joint and diagnosis of infection was longer in RA patients: median 110 (IQR 41-171) vs 29 months (IQR 7.5–101.25). Exchange of mobile components was associated with a lower risk of treatment failure (HR 0.489, 95% CI 0.242–0.989, p-value .047). Conclusions. The use of immunosuppressive drugs does not seem to be associated with a higher failure rate in patients with RA. Mobile exchange in RA patients is associated with a lower risk of failure. This might be due to the significantly older age of the prosthesis in RA patients. Future studies are needed to explore these associations and its underlying pathogenesis

Aim. Calcaneal osteomyelitis is an uncommon and challenging condition. In this systemic review we aim to analyse the concomitant use of bone debridement and soft tissue management for patients diagnosed with calcaneal osteomyelitis. Method. A complete computerised and comprehensive literature search of Pubmed and Cochrane database was undertaken from January 2000 to October 2018. During the review, studies were screened for information about the surgical and antimicrobial treatment, the complications, the reinfection rate and the functional outcome of patients with calcaneal osteomyelitis. Results. Of the 20 studies included, seven (35%) described bone treatment only, six (30%) soft tissue treatment only, five (25%) soft tissue and bone treatment, and two (10%) focused on prognostic factors and differences in outcomes between diabetic and non-diabetic patients. In the studies with bone treatment only, infection recurrence ranged from 0 to 35% and the amputation rate from 0 to 29%. If soft tissue coverage was also needed, both the reinfection rate and amputation rate ranged from 0 to 24%. Studies presenting the functional status showed preservation or even improvement of the preoperative ambulatory status. Conclusions. Calcaneal osteomyelitis is difficult to treat. A multidisciplinary approach involving orthopaedic surgeons, plastic surgeons and infectious disease physicians is necessary for treatment success. Based on the localisation and size of the bone and soft tissue defect, decision for surgical treatment should be made

Aim. Periprosthetic joint infections (PJI) are a severe complications after hip arthroplasty. The infections rate ranges from 0.7 to 1.3 depending on different reports. The aim of the present study is to evaluate the radiological and clinical outcome of patients that underwent two-stage revision for the treatment of periprosthetic joint infection of the hip when an extended trochanteric osteotomy (ETO) was necessary to remove the femoral stem. Methods. We retrospectively analyzed data from 84 patients that underwent two-stage revision of the hip between January 2006 and December 2010 at our institution. In forty-nine patients (Group A, 58.3%), the femoral stem was removed without an ETO, while in the remaining thirty-five patients (Group B, 41.7%) an ETO was necessary. In each case a metallic cerclage was used to closure of the flap. The average age for patients in group A was 64.3 years, while the average age in patients in group B was 66.4 years. The mean follow-up was respectively 117 months in group A and 122 months in group B. Eight patients died before the last follow-up, and data from six patients were incomplete. Complications, radiological and clinical outcome were. Mann Whitney U Test and Chi Square Test were used respectively to analyze continues and categorical variables. Cumulative survival of the implants was calculated for reinfection and mechanical complications with Kaplan-Meyer curves. Results. The mean follow-up was 118 months. The cumulative incidence of reinfection was 4.7% at 1 years and 10.7 at last follow-up. No statistically significant (p-value > 0.05) differences were observed in the two groups neither at 1 year nor at last follow up. The cumulative incidence of mechanical complication was 3.6% at 1 year and 8.3% at last follow-up. No statistically significant differences (p-value > 0.05) were observed in the two groups neither at 1 year nor at last follow up. All the patients had the healing of the ETO at six months (mean 11.4 weeks). The mean Harris Hip Score was 77.5. No statistically significant (p-value > 0.05) differences were observed in the two groups. Discussion. The results obtained in this retrospective study demonstrates that there is no difference in terms of reinfection-rate, mechanical complications and clinical outcome in patients that underwent two-stage revision with or without an ETO. In presence of a well-fixed femoral stem, performing an ETO could be helpful to expose the femoral canal facilitating the femoral stem's removal avoiding intra-operative femoral fracture

INTRODUCTION. Conventional surgical exposures are usually inadequate for 2-stage revision knee replacement ofinfected implants. Reduced range of motion, extensor mechanism stiffness, peripatellar contracture and soft tissue scarring make patellar eversion difficult and forced eversion places the integrity of the extensor mechanism at risk. On the contrary, a wide exposure is fundamental to allow complete cement spacer removal, soft tissue balancing, management of bone loss and reimplantation without damaging periarticular soft tissues. OBJECTIVES. To compare the long-term clinical, functional and radiographic results and the reinfection rate of the quadriceps snip approach and the tibial tubercle osteotomy in 2-stage revision knee replacement performed for septic loosening of the primary implant. METHODS. In our department, 87 patients had a 2 stage revision knee replacement for septic loosening of the primary implant between 1996 and 2008. In all patients, first stage consisted of primary implant removal, extensive soft tissue debridement and positioning of a static antibiotic loaded cement spacer. The timing for reimplantation was decided basing on negative clinical and laboratory (ESR, CRP) signs and negative Leukoscan results. For reimplantation, a quadriceps snip was used in patients with an intraoperative flexion >90° (Group A) while a tibial tubercle osteotomy (Group B) was used in patients with an intraoperative flexion <90°. RESULTS. At observation point, 4 patients died for reasons unrelated to surgery, leaving 42 patients in Group A and 41 in Group B. We had a total amount of 10 recurrent infections (11%) after reimplantation, 7 patients in Group A and 3 patients in Group B (p<0.005). Patients with a reinfection in Group A were treated with a knee fusion in 4 cases, a rerevision in 2 cases and an amputation above the knee in 1 case, while all those with a reinfection in Group B had a knee fusion. According to HSS score, 11 patients were rated as Excelent/Good in Group A and 9 patients in Group B (p=n.s.). Three patients had a major complication in Group A and 0 patients in Group B (p=0.005). No differences were found between the two groups regarding range of motion and subjective satisfaction. CONCLUSION. Tibial tubercle osteotomy is a safe procedure to obtain a wide exposure in 2-stage revision knee replacement performed for septic loosening of the primary implant and it is effective in reducing reinfection rate without compromising clinical results and range of motion

Aim. Two stage revision is the most commonly used surgical treatment strategy for periprosthetic hip infections (PHI). The aim of our study was to assess the intra- and postoperative complications during and after two stage revision using resection arthroplasty between ex- and reimplantation. Method. In this retrospective cohort study, all patients treated with a two stage revision using resection arthroplasty for PHI were included from 2008 to 2014. During the first stage, the prosthesis was removed resulting in a resection arthroplasty without the use a PMMA spacer. During second stage, (cemented or uncemented) reimplantation of the hip prosthesis was performed. The cohort was stratified into two groups according to the length of prosthesis-free interval (≤10 weeks and >10 weeks). Data on complications during explantation, prosthesis-free interval, reimplantation, and after reimplantation was collected. The overall complication rate between both groups was compared using the chi-squared test. The revision-free and infection-free survival was estimated using Kaplan-Meier survival analysis. Results. Overall, 93 patients with hip PJI treated with two-stage revision performing resection arthroplasty were included, 49 had a prosthesis-free interval of ≤10 weeks, and 44 an interval of >10 weeks. A total of 146 complications was documented in the cohort. Patients were followed-up for a mean duration of 42.7 months, range: 13.1 – 104.6 months. Blood loss during reimplantation [n=25], blood loss during explantation [n=23], persistent infection during prosthesis-free interval [n=16], leg length discrepancy [n=13], and reinfection [n=9] were the most common complications. No complication showed a statistically significant difference between both groups except for wound healing disorder after reimplantation, which was more often reported in the group with > 10 weeks interval (p=0.009). A statistically significant increase of periprosthetic bone fractures (p=0.05), blood loss (p=0.039), and total number of complications (p=0.008) was seen with increasing acetabular bone defects (after Paprosky). Infection-free survival rate at 24 months was 93.9% (95% CI: 87.2 – 100) in the group with ≤10 weeks interval and 85.9% (95% CI: 75.4 – 96.4) with an interval of > 10weeks. Conclusions. After two years of follow-up, the infection-free survival rate using resection arthroplasty during two stage revision for PHI was higher in the group with ≤10 weeks interval compared to the group with >10 weeks interval. The most common complications during and after a two stage revision using resection arthroplasty were blood loss during the two surgeries, persistent infection during the prosthesis-free interval, leg length discrepancy, and reinfection

Two-stage treatment of chronically infected TKA is the most common form of management in North America and most parts of the world. One-stage management has pros and cons which will not be discussed in this lecture. There is great variation of techniques and timing and little data to definitively support one technique or timing approach vs. another. Most methods are based on empirical success and logic. At the time of surgery, the first step is removal of infected implants. All metallic implants and cement should be removed. The most common places to leave cement behind inadvertently include patellar lug holes, femoral lug holes, and the anterior proximal tibia behind the tibial tubercle. Formal synovectomy should be performed. The next step is typically antibiotic-impregnated spacer placement. There are pros and cons of dynamic and static spacers with no clear evidence of superiority of one vs. another. Dynamic spacers work satisfactorily with mild to moderate bone loss, but more severe bone loss is usually better treated with static spacers and a cast. Most antibiotic spacers are made of methyl methacrylate cement with addition of high-dose antibiotics. In most cases, doses of 4–8 gm of antibiotics per pack of cement are preferred. The type of dosing depends on the specific antibiotic and the type of cement used. The most common antibiotics used are vancomycin and gentamycin. When the femoral canals have been instrumented, antibiotic-impregnated cement wands are usually placed in the medullary canal, as the medullary canals have been shown to have high risk of residual bacteria being present. The resection interval may vary and there is no clear evidence of a “best” resection interval. Practically speaking, most surgeons use a resection period of 8–16 weeks depending on the type of spacer utilised. During the resection interval, serum markers (ESR and CRP) are followed periodically. One anticipates a decline or normalization of these parameters prior to second stage reimplantation procedure. There has not been a demonstrated advantage to reaspiration of the knee before reimplantation in most circumstances. At the time of reimplantation, the spacers are removed and the knee is redebrided. The key at the time of reimplantation is to obtain good implant fixation but to also balance this with the potential for manageable extraction of the implants at some later date. Good implant fixation is important because failure rates due to mechanical failure are approximately equal to those of failure due to reinfection by 10 years. It is important to remember that reinfection risk is at least 10% by ten years, and therefore extractability of implants is also important. Post-operative management typically includes IV antibiotics, followed by oral antibiotics until final intra-operative cultures are available. The results of two-stage reimplantation are reported in many series. Most show approximately 85–95% rate of successful eradication of infection in the first five years. Reinfections, often with different organisms, may occur even late after reimplantation. By ten years after surgery survival free of mechanical failure and infection in most series drops to 80% or less due to recurrent infections and mechanical failures

Periprosthetic joint infection (PJI) is a potentially devastating complication of joint replacement surgery. Osteocytes comprise 90–95% of all cells in hard bone tissue, are long-lived and are becoming increasingly recognised as a critical cell type in the regulation of bone and systemic physiology. The purpose of this study was to examine role of these cells in PJI pathophysiology and aetiology, with the rationale that their involvement could contribute to the difficulty in detecting and clearing PJI. This study examined the ability of human osteocytes to become infected by Staphylococcus aureus and the responses of both the host cell and pathogen in this scenario. Several S. aureus (MRSA) strains were tested for their ability to infect human primary osteocyte-like cells in vitro and human bone samples ex vivo. Bone biopsies were retrieved from patients undergoing revision total hip arthroplasty for either aseptic loosening associated with osteolysis, or for PJI. Retrieved bacterial colony number from cell lysates and colony morphology were determined. Gene expression was measured by microarray/bioinformatics analysis and/or real-time RT-PCR. Exposure to planktonic S. aureus (approx. 100 CFU/cell) resulted in intracellular infection of human osteocyte-like cells. We found no evidence of increased rates of osteocyte cell death in bacteria exposed cultures. Microarray analysis of osteocyte gene expression 24h following exposure revealed more than 1,500 differentially expressed genes (fold-change more than 2, false discovery rate p < 0.01). The gene expression patterns were consistent with a strong innate immune response and altered functionality of the osteocytes. Consistent patterns of host gene expression were observed between experimentally infected osteocyte-like cultures and human bone, and in PJI patient bone samples. Internalised bacteria switched to the quasi-dormant small colony variant (SCV) form over a period of 5d, and the ensuing infection appeared to reach a stable state. S. aureus infection of viable osteocytes was also identified in bone taken from PJI patients. We have demonstrated [1] that human osteocytes can become infected by S. aureus and respond robustly by producing immune mediators. The bony location of the infected osteocyte may render them refractory to clearance by immune cells, and osteocytes may therefore be an immune-privileged cell type. The phenotypic switch of S. aureus to SCV, a form less sensitive to most antibiotics and one associated with intracellular survival, suggests that infection of osteocytes may contribute to a chronic disease state. The osteocyte may therefore serve as a reservoir of bacteria for reinfection, perhaps explaining the high prevalence of infections that only become apparent after long periods of time or recur following surgical/medical treatment. Our findings also provide a biological rationale for the recognised need for aggressive bone debridement in the surgical management of PJI

Background. Two-stage revision is considered the gold standard for treatment of knee prosthetic joint infections. Current guidelines for selecting the most appropriate procedure to eradicate knee prosthetic joint infections are based upon the duration of symptoms, the condition of the implant and soft tissue evaluated during surgery and the infecting organism. A more robust tool to identify candidates for two-stage revision and who are at high risk for treatment failure might improve preoperative risk assessment and increase a surgeon's index of suspicion, resulting in closer monitoring, optimization of risk factors for failure and more aggressive management of those patients who are predicted to fail. Methods. Charts from 3,809 revision total joint arthroplasties were reviewed. Demographic data, clinical data and disease follow-up on 314 patients with infected total knee arthroplasty treated with two-stage revision were collected. Univariate analyses were performed to determine which variables were independently associated with failure of the procedure to eradicate the prosthetic joint infections. Cox regression was used to construct a model predicting the probability of treatment failure and the results were used to generate a nomogram which was internally validated using bootstrapping. Results. 209 (66.6%) cases experienced reinfection at an average of 429 days (range, 9 to 3,886) following the two-stage revision. Univariate analysis identified multiple variables independently associated with reinfection including: a longer duration of symptoms (p<0.001), a longer time from the index total knee arthroplasty (p=0.003), a higher number of previous surgeries in the same joint (p<0.001), an elevated C-reactive protein (p=0.005), an elevated erythrocyte sedimentation rate (p=0.006), a low hemoglobin (p=0.001), a previous infection in the same joint (p<0.001), diabetes (p<0.001), and heart disease (p=0.006). Among 1,000 bootstrap samples, the bias corrected receiver operating characteristic for the nomogram was 0.77. Conclusions. Preoperative knowledge of the probability that a treatment strategy will eradicate a patient's prosthetic joint infection may improve risk assessment and allow adequate time for consideration of alternative therapies

Introduction. Infections affect 1–3% of Total Knee Arthroplasty (TKA) patients with severe ramifications to mobility. Unfortunately, reinfection rates are high (∼15%) suggesting improved diagnostics are required. A common strategy to treat TKA infection in North America is the two-stage revision procedure involving the installation of a temporary spacer in the joint while the infection is treated for 6–12 weeks before permanent revision. Subdermal temperature increases during infection by 1–4°C providing a potential indicator for when the infection has been cleared. We propose an implantable temperature sensor integrated into a tibial spacer for telemetric use. We hypothesized that suitable sensing performance for infection monitoring regarding precision and relative accuracy can be attained using a low power, compact, analog sensor with <0.1ºC resolution. Materials & Methods. An experimental sensor was selected for our implanted application due to its extremely low (9 μA) current draw and compact chip package. Based upon dynamic range it was determined that the analog/digital converter must be a minimum of 11 bits to deliver suitable (<0.1ºC) resolution. A 12-bit ADC equipped microcontroller was selected. The MCP9808 (Microchip Technology, Chandler, AZ, USA) delivers manufacturer characterized thermal data in decimal strings through serial communication to the same microcontroller. The rated accuracy of the MCP9808 sensors in the required temperature range is max/typ +/− 0.5/0.25ºC with a precision of +/− 0.05ºC delivered at a resolution of 0.0625ºC. Within a thermally insulated chamber with a resistive heating element, the following experiment was conducted: Using empirical plant modelling tools, simulation and implementation an effective PI control scheme was implemented to create a highly precise temperature chamber. With MCP9808 as reference, the temperature in the thermal chamber was driven to 20 different temperatures between 35 and 40ºC for 10 minutes each and sampled at 5 Hz. This trial was repeated three times over three days. Transient data was discarded so as only to evaluate the steady state characteristics, wavelet denoising was applied, and a regression between the reference MCP9808 temperature response vs the experimental sensor intended for implantation was tabulated in Matlab. Results. Compared to reference values, the experimental temperature sensor displayed relative accuracy of +/− 0.275ºC (with 95% confidence) and precision of +/−0.135ºC over a 35–40ºC range as determined over 190,212 relevant samples. Note that in practice, the precision is independent of reference, but the absolute accuracy is relative to the gold standard's accuracy. Conclusion. Infection frequently results in permanent mobility issues in the context of total knee arthroplasty. This has led to an ongoing call for better treatments. Analysis suggests that the proposed experimental sensor offers high precision and reasonable relative accuracy in temperature sensing, substantially tighter than the expected stimulus from infection, while also offering desirable characteristics for implantation. This sensing platform will be integrated into an instrumented tibial spacer in future work. For any figures or tables, please contact authors directly

Nutritional Status and Short-Term Outcomes Following THA; Initial Metal Ion Levels Predict Risk in MoM THA; THA Bearing Surface Trends in the US ‘07- ’14; Dislocation Following Two-Stage Revision THA; Timing of Primary THA Prior to or After Lumbar Spine Fusion; Failure Rate of Failed Constrained Liner Revision; ESR and CRP vs. Reinfection Risk in Two-Stage Revision?; Mechanical Complications of THA Based on Approach; Impaction Force and Taper-Trunnion Stability in THA; TKA in Patients Less Than 50 Years of Age; Post-operative Mechanical Axis and 20-year TKA Survival and Function; Return to Moderate to High-intensity Sports after UKA; “Running Two Rooms” and Patient Safety in TJA; Varus and Implant Migration and Contact Kinematics after TKA; Quadriceps Snips in 321 Revision TKAs; Tubercle Proximalization for Patella Infera in Revision TKA; Anterior Condylar Height and Flexion in TKA; Compression Bandage Following Primary TKA; Unsupervised Exercise vs. Traditional PT After Primary TKA and UKA