Aims

We propose a state-of-the-art temporary spacer, consisting of a cobalt-chrome (CoCr) femoral component and a gentamicin-eluting ultra-high molecular weight polyethylene (UHMWPE) tibial insert, which can provide therapeutic delivery of gentamicin, while retaining excellent mechanical properties. The proposed implant is designed to replace conventional spacers made from bone cement.

Aims. There is little information regarding the risk of a patient developing prosthetic joint infection (PJI) after primary total knee arthroplasty (TKA) when the patient has previously experienced PJI of a TKA or total hip arthroplasty (THA) in another joint. The goal of this study was to compare the risk of PJI of primary TKA in this patient population against matched controls. Patients and Methods. We retrospectively reviewed 95 patients (102 primary TKAs) treated between 2000 and 2014 with a history of PJI in another TKA or THA. A total of 50 patients (53%) were female. Mean age was 69 years (45 to 88) with a mean body mass index (BMI) of 36 kg/m. 2. (22 to 59). In total, 27% of patients were on chronic antibiotic suppression. Mean follow-up was six years (2 to 16). We 1:3 matched these (for age, sex, BMI, and surgical year) to 306 primary TKAs performed in 306 patients with a THA or TKA of another joint without a subsequent PJI. Competing risk with death was used for statistical analysis. Multivariate analysis was followed to evaluate risk factors for PJI in the study cohort. Results. The cumulative incidence of PJI in the study cohort (6.1%) was significantly higher than the matched cohort (2.6%) at ten years (hazard ratio (HR) 3.3; 95% confidence interval 1.18 to 8.97; p = 0.02). Host grade in the study group was not a significant risk factor for PJI. Patients on chronic suppression had a higher rate of PJI (HR 15; p = 0.002), with six of the seven patients developing PJI in the study group being on chronic suppression. The new infecting microorganism was the same as the previous in only two of seven patients. Conclusion. In this matched cohort study, patients undergoing a clean primary TKA with a history of TKA or THA PJI in another joint had a three-fold higher risk of PJI compared with matched controls with ten-year cumulative incidence of 6.1%. The risk of PJI was 15-fold higher in patients on chronic antibiotic suppression; further investigation into reasons for this and mitigation strategies are recommended. Cite this article: Bone Joint J 2019;101-B(7 Supple C):91–97

Aims. Two-stage exchange arthroplasty is the most common definitive treatment for prosthetic joint infection (PJI) in the USA. Complications that occur during treatment are often not considered. The purpose of this study was to analyze complications in patients undergoing two-stage exchange for infected total knee arthroplasty (TKA) and determine when they occur. Methods. We analyzed all patients that underwent two-stage exchange arthroplasty for treatment of PJI of the knee from January 2010 to December 2018 at a single institution. We categorized complications as medical versus surgical. The intervals for complications were divided into: interstage; early post-reimplantation (three months); and late post-reimplantation (three months to minimum one year). Minimum follow-up was one year. In total, 134 patients underwent a first stage of a two-stage exchange. There were 69 males and 65 females with an mean age at first stage surgery of 67 years (37 to 89). Success was based on the new Musculoskeletal Infection Society (MSIS) definition of success reporting. Results. Overall, 70 (52%) patients experienced a complication during the planned two-stage treatment, 36 patients (27%) experienced a medical complication and 47 (41%) patients experienced a surgical complication. There was an 18% mortality rate (24/134) at a mean of 3.7 years (0.09 to 8.3). During the inter-stage period, 28% (37/134) of patients experienced a total of 50 complications at a median of 47 days (interquartile range (IQR) 18 to 139). Of these 50 complications, 22 were medical and 28 required surgery. During this inter-stage period, four patients died (3%) and an additional five patients (4%) failed to progress to the second stage. While 93% of patients (125/134) were reimplanted, only 56% (77/134) of the patients were successfully treated without antibiotic suppression (36%, 28/77) or with antibiotic suppression (19%, 15/77) at one year. Conclusion. Reported rates of success of two stage exchanges for PJI have not traditionally considered complications in the definition of success. In our series, significant numbers of patients experienced complications, more often after reimplantation, highlighting the morbidity of this method of treatment. Cite this article: Bone Joint J 2020;102-B(6 Supple A):145–150

Aims. The aim of this study was to determine if the local delivery of vancomycin and tobramycin in primary total knee arthroplasty (TKA) can achieve intra-articular concentrations exceeding the minimum inhibitory concentration thresholds for bacteria causing acute prosthetic joint infection (PJI). Methods. Using a retrospective single-institution database of all primary TKAs performed between January 1 2014 and May 7 2019, we identified patients with acute PJI that were managed surgically within 90 days of the initial procedure. The organisms from positive cultures obtained at the time of revision were tested for susceptibility to gentamicin, tobramycin, and vancomycin. A prospective study was then performed to determine the intra-articular antibiotic concentration on postoperative day one after primary TKA using one of five local antibiotic delivery strategies with tobramycin and/or vancomycin mixed into the polymethylmethacrylate (PMMA) or vancomycin powder. Results. A total of 19 patients with acute PJI after TKA were identified and 29 unique bacterial isolates were recovered. The mean time to revision was 37 days (6 to 84). Nine isolates (31%) were resistant to gentamicin, ten (34%) were resistant to tobramycin, and seven (24%) were resistant to vancomycin. Excluding one Fusobacterium nucleatum, which was resistant to all three antibiotics, all isolates resistant to tobramycin or gentamicin were susceptible to vancomycin and vice versa. Overall, 2.4 g of tobramycin hand-mixed into 80 g of PMMA and 1 g of intra-articular vancomycin powder consistently achieved concentrations above the minimum inhibitory concentrations of susceptible organisms. Conclusion. One-third of bacteria causing acute PJI after primary TKA were resistant to the aminoglycosides commonly mixed into PMMA, and one-quarter were resistant to vancomycin. With one exception, all bacteria resistant to tobramycin were susceptible to vancomycin and vice versa. Based on these results, the optimal cover for organisms causing most cases of acute PJI after TKA can be achieved with a combination of tobramycin mixed in antibiotic cement, and vancomycin powder. Cite this article: Bone Joint J 2020;102-B(6 Supple A):163–169

Introduction. Periprosthetic infection (PJI) after primary total knee arthroplasty (TKA) remains a challenging issue affecting 1–2% of cases. Locally delivered prophylactic antibiotics, including tobramycin or gentamicin mixed in polymethylmethacrylate (PMMA) bone cement and vancomycin powder, are increasingly used despite a lack of high quality evidence for either practice. In this study, we report the antibiotic susceptibility of organisms recovered in culture from patients with acute prosthetic joint infection after primary TKA to gentamicin, tobramycin and vancomycin. Methods. Using a retrospective database of all primary TKA performed at a single institution between January, 1 2014 and July 1, 2018, we identified 18 cases of acute PJI after primary TKA, as defined by the Musculoskeletal Infection Society 2011 guidelines as less than 3 months from symptoms or index surgery to presentation. The use of antibiotic bone cement during the index procedure and time to surgical management of the infection were recorded. Fluid cultures and tissue cultures were obtained intraoperatively at the time of revision. The organisms from positive cultures underwent MIC testing to gentamicin, tobramycin and vancomycin using a gradient diffusion method (ETEST). MIC breakpoints for susceptibility were based on Clinical and Laboratory Standards Institute definitions. Results. 18 cases of PJI after TKA were identified, including 4 polymicrobial infections (22.2%) (Table 1). Average time to revision for infection was 38 days (range: 6–84 days). 34.8% of bacterial isolates were resistant to gentamicin, 39.1% were resistant to tobramycin and 17.4% were resistant to vancomycin. Of the 8 bacterial isolates resistant to gentamicin, 7 (87.5%) were susceptible tobramycin. Of the 9 bacterial isolates resistant to tobramycin, (88.9%) were susceptible to vancomycin. One bacterial isolate, a Fusobacterium nucleatum from a polymicrobial infection was resistant to gentamicin, tobramycin and vancomycin. Conclusion. Over one third of bacteria causing acute PJI after primary TKA were resistant to the aminoglycosides pre-mixed in commercially available bone cements. All but one of the bacteria resistant to gentamicin and tobramycin were susceptible to vancomycin. The addition of vancomycin to bone cement or as powder in the surgical field has the potential to expand antibiotic coverage to include most organisms responsible for acute PJI after TKA. For figures, tables, or references, please contact authors directly

Abstract. Aim. End-stage arthropathy is a well-known complication of haemophilia, with recurrent haemarthroses leading to joint destruction, deformity, pain, and stiffness. In the knee, this is often treated with total knee arthroplasty (TKA), which can be more challenging in patients with haemophilia (PwH) and associated with poorer outcomes. We conducted a systematic literature review and meta-analysis to determine implant survivorship, functional outcomes and complication rates. Method. A systematic review was conducted using MEDLINE, EMBASE, and PubMed for studies reporting TKA outcomes with Kaplan-Meier survivorship in PwH (PROSPERO registered). Meta-analysis was performed for survivorship and outcomes, and the results were compared to outcomes from the National Joint Registry (NJR). Results. 19 studies, totalling 1187 TKAs (average age 39 years) were reviewed. In PwH, implant survivorship at 5, 10, and 15 years was 94%, 86%, and 76% respectively, whereas NJR reported survivorship for males <55 years was 94%, 90%, and 86%. Survivorship generally improved over the time period studied (1973–2017), but was inversely correlated with HIV infection (common in PwH). Range of motion improved by 10–20° post-operatively, and there were large improvements in Patient Reported Outcome Measures (PROMS). The prosthetic joint infection rate (PJI) was 6% compared to 0.5-1% in non-PwH, but the reporting of other complications, especially haematological, was inconsistent. Conclusions. TKA in PwH has similar 5-year survivorship to non-PwH, but a six-fold higher infection rate. There were marked improvements in range of motion and PROMS, but complications were poorly reported. There remains a need for larger, long-term studies with standardised reporting

Abstract. Background. Prosthetic joint infection (PJI) is a significant cause of morbidity and mortality following knee replacement surgery. Identifying the causative agent(s) and their antibiotic sensitivities is critical in determining the choice of treatment methods used and the likelihood of successful eradication. This study aimed to investigate:. Whether biopsy alone was superior to aspiration alone in specificity and sensitivity for diagnosing PJI following knee replacement. Whether biopsy identifies the same microbiological flora as aspiration. Methods. We identified consecutive patients passing through our knee infection Multi-Disciplinary Team meeting between December 2014 and March 2020. Data was collated data retrospectively using electronic records. Statistical analysis was performed using Stata (Timberlake, February 2020). Results. 65 of 100 patients identified had both pre-operative aspiration and biopsy. In 29% of positive patients, biopsy identified new or additional organisms not previously identified by aspiration. Aspiration had a sensitivity of 70%, specificity of 88%, positive predictive value of 90.3% and negative predictive value of 64.7%. Biopsy had a sensitivity of 97.5%, specificity of 88%, positive predictive value of 92.9% and negative predictive value of 95.7%. Conclusion. Biopsy is superior to aspiration in the diagnosis of PJI and can be performed safely and successfully. It identifies organisms when aspiration may be negative and identifies additional microorganisms in a polymicrobial setting not identified by aspiration alone (29% of positive cases). We would recommend, where possible, aspiration and biopsy as routine pre-operative sampling in order to identify all causative agents and their susceptibilities prior to embarking on revision surgery

Aims. In patients with a “dry” aspiration during the investigation of prosthetic joint infection (PJI), saline lavage is commonly used to obtain a sample for analysis. The aim of this study was to investigate prospectively the impact of saline lavage on synovial fluid analysis in revision arthroplasty. Methods. Patients undergoing revision hip (THA) or knee arthroplasty (TKA) for any septic or aseptic indication were enrolled. Intraoperatively, prior to arthrotomy, the maximum amount of fluid possible was aspirated to simulate a dry tap (pre-lavage) followed by the injection with 20 ml of normal saline and re-aspiration (post-lavage). Pre- and post-lavage synovial white blood cell (WBC) count, percent polymorphonuclear cells (%PMN), and cultures were compared. Results. A total of 78 patients had data available for analysis; 17 underwent revision THA and 61 underwent revision TKA. A total of 16 patients met modified Musculoskeletal Infection Society (MSIS) criteria for PJI. Pre- and post-lavage %PMNs were similar in septic patients (87% vs 85%) and aseptic patients (35% vs 39%). Pre- and post-lavage synovial fluid WBC count were far more disparate in septic (53,553 vs 8,275 WBCs) and aseptic (1,103 vs 268 WBCs) cohorts. At a cutoff of 80% PMN, the post-lavage aspirate had a sensitivity of 75% and specificity of 95%. At a cutoff of 3,000 WBCs, the post-lavage aspirate had a sensitivity of 63% and specificity of 98%. As the post-lavage synovial WBC count increased, the difference between pre- and post-lavage %PMN decreased (mean difference of 5% PMN in WBC < 3,000 vs mean difference 2% PMN in WBC > 3,000, p = 0.013). Of ten positive pre-lavage fluid cultures, only six remained positive post-lavage. Conclusion. While saline lavage aspiration significantly lowered the synovial WBC count, the %PMN remained similar, particularly at WBC counts of > 3,000. These findings suggest that in patients with a dry-tap, the %PMN of a saline lavage aspiration has reasonable sensitivity (75%) for the detection of PJI. Cite this article: Bone Joint J 2020;102-B(6 Supple A):138–144

Aims. The aim of this study was to determine if a three-month course of microorganism-directed oral antibiotics reduces the rate of failure due to further infection following two-stage revision for chronic prosthetic joint infection (PJI) of the hip and knee. Methods. A total of 185 patients undergoing a two-stage revision in seven different centres were prospectively enrolled. Of these patients, 93 were randomized to receive microorganism-directed oral antibiotics for three months following reimplantation; 88 were randomized to receive no antibiotics, and four were withdrawn before randomization. Of the 181 randomized patients, 28 were lost to follow-up, six died before two years follow-up, and five with culture negative infections were excluded. The remaining 142 patients were followed for a mean of 3.3 years (2.0 to 7.6) with failure due to a further infection as the primary endpoint. Patients who were treated with antibiotics were also assessed for their adherence to the medication regime and for side effects to antibiotics. Results. Nine of 72 patients (12.5%) who received antibiotics failed due to further infection compared with 20 of 70 patients (28.6%) who did not receive antibiotics (p = 0.012). Five patients (6.9%) in the treatment group experienced adverse effects related to the administered antibiotics severe enough to warrant discontinuation. Conclusion. This multicentre randomized controlled trial showed that a three-month course of microorganism-directed, oral antibiotics significantly reduced the rate of failure due to further infection following a two-stage revision of total hip or knee arthroplasty for chronic PJI. Cite this article: Bone Joint J 2020;102-B(6 Supple A):3–9

Aims. Metaphyseal cones with cemented stems are frequently used in revision total knee arthroplasty (TKA). However, if the diaphysis has been previously violated, the resultant sclerotic canal can impair cemented stem fixation, which is vital for bone ingrowth into the cone, and long-term fixation. We report the outcomes of our solution to this problem, in which impaction grafting and a cemented stem in the diaphysis is combined with an uncemented metaphyseal cone, for revision TKA in patients with severely compromised bone. Methods. A metaphyseal cone was combined with diaphyseal impaction grafting and cemented stems for 35 revision TKAs. There were two patients with follow-up of less than two years who were excluded, leaving 33 procedures in 32 patients in the study. The mean age of the patients at the time of revision TKA was 67 years (32 to 87); 20 (60%) were male. Patients had undergone a mean of four (1 to 13) previous knee arthroplasty procedures. The indications for revision were aseptic loosening (80%) and two-stage reimplantation for prosthetic joint infection (PJI; 20%). The mean follow-up was four years (2 to 11). Results. Survival free from revision of the cone/impaction grafting construct due to aseptic loosening was 100% at five years. Survival free from any revision of the construct and free from any reoperation were 92% and 73% at five years, respectively. A total of six patients (six TKAs, 17%) required a further revision, four for infection or wound issues, and two for periprosthetic fracture. Radiologically, one unrevised TKA had evidence of loosening which was asymptomatic. In all unrevised TKAs the impacted diaphyseal bone graft appeared to be incorporated radiologically. Conclusion. When presented with a sclerotic diaphysis and substantial metaphyseal bone loss, this technique combining diaphyseal impaction grafting with a metaphyseal cone provided near universal success in relation to implant fixation. Moreover, radiographs revealed incorporation of the bone graft and biological fixation of the cone. While long-term follow-up will be important, this technique provides an excellent option for the management of complex revision TKAs. Cite this article: Bone Joint J 2020;102-B(6 Supple A):116–122

Aims. The aim of this study was to assess the effects of transferring patients to a specialized arthroplasty centre between the first and second stages (interstage) of prosthetic joint infection (PJI) of the knee. Patients and Methods. A search of our institutional database was performed to identify patients having undergone two-stage revision total knee arthroplasty (TKA) for PJI. Two cohorts were created: continuous care (CC) and transferred care (TC). Baseline characteristics and outcomes were collected and compared between cohorts. Results. A total of 137 patients were identified: 105 in the CC cohort (56 men, 49 women; mean age 67.9) and 32 in the TC cohort (17 men, 15 women; mean age 67.8 years). PJI organism virulence was greater in the CC cohort (36.2% vs 15.6%; p = 0.030). TC patients had a higher rate of persisting or recurrent infection (53.6% vs 13.4%; p < 0.001), soft-tissue complications (31.3 vs 14.3%; p = 0.030), and reduced requirement for porous metal augments (78.1% vs 94.3%; p = 0.006). Repeat first stage debridement after transfer led to greater need for plastic surgical procedures (58.3% vs 0.0%; p < 0.001). Conclusion. Patient transfer during the interstage of treatment for infected TKA leads to poorer outcomes compared with patients receiving all their treatment at a specialized arthroplasty centre. Cite this article: Bone Joint J 2019;101-B:1087–1092

Aims. The purpose of this study was to compare outcomes of combined total joint arthroplasty (TJA) (total hip arthroplasty (THA) and total knee arthroplasty (TKA) performed during the same admission) versus bilateral THA, bilateral TKA, single THA, and single TKA. Combined TJAs performed on the same day were compared with those staged within the same admission episode. Patients and Methods. Data from the National (Nationwide) Inpatient Sample recorded between 2005 and 2014 were used for this retrospective cohort study. Postoperative in-hospital complications, total costs, and discharge destination were reviewed. Logistic and linear regression were used to perform the statistical analyses. p-values less than 0.05 were considered statistically significant. Results. Combined TJA was associated with increased risk of deep vein thrombosis, prosthetic joint infection, irrigation and debridement procedures, revision arthroplasty, length of stay (LOS), and in-hospital costs compared with bilateral THA, bilateral TKA, single THA, and single TKA. Combined TJA performed on separate days of the same admission showed no statistically significant differences when compared with same-day combined TJA, but trended towards decreased total costs and total complications despite increased LOS. Conclusion. Combined TJA is associated with increased in-hospital complications, LOS, and costs. We do not recommend performing combined TJA during the same hospital stay. Cite this article: Bone Joint J 2019;101-B:573–581

Aims. The best marker for assessing glycaemic control prior to total knee arthroplasty (TKA) remains unknown. The purpose of this study was to assess the utility of fructosamine compared with glycated haemoglobin (HbA1c) in predicting early complications following TKA, and to determine the threshold above which the risk of complications increased markedly. Patients and Methods. This prospective multi-institutional study evaluated primary TKA patients from four academic institutions. Patients (both diabetics and non-diabetics) were assessed using fructosamine and HbA1c levels within 30 days of surgery. Complications were assessed for 12 weeks from surgery and included prosthetic joint infection (PJI), wound complication, re-admission, re-operation, and death. The Youden’s index was used to determine the cut-off for fructosamine and HbA1c associated with complications. Two additional cut-offs for HbA1c were examined: 7% and 7.5% and compared with fructosamine as a predictor for complications. Results. Overall, 1119 patients (441 men, 678 women) were included in the study. Fructosamine level of 293 µmol/l was identified as the optimal cut-off associated with complications. Patients with high fructosamine (> 293 µmol/l) were 11.2 times more likely to develop PJI compared with patients with low fructosamine (p = 0.001). Re-admission and re-operation rates were 4.2 and 4.5 times higher in patients with fructosamine above the threshold (p = 0.005 and p = 0.019, respectively). One patient (1.7%) from the elevated fructosamine group died compared with one patient (0.1%) in the normal fructosamine group (p = 0.10). These complications remained statistically significant in multiple regression analysis. Unlike fructosamine, all three cut-offs for HbA1c failed to show a significant association with complications. Conclusion. Fructosamine is a valid and an excellent predictor of complications following TKA. It better reflects the glycaemic control, has greater predictive power for adverse events, and responds quicker to treatment compared with HbA1c. These findings support the screening of all patients undergoing TKA using fructosamine and in those with a level above 293 µmol/l, the risk of surgery should be carefully weighed against its benefit. Cite this article: Bone Joint J 2019;101-B(7 Supple C):3–9

Aims. Varus-valgus constrained (VVC) implants are often used during revision total knee arthroplasty (TKA) to gain coronal plane stability. However, the increased mechanical torque applied to the bone-cement interface theoretically increases the risk of aseptic loosening. We assessed mid-term survivorship, complications, and clinical outcomes of a fixed-bearing VVC device in revision TKAs. Methods. A total of 416 consecutive revision TKAs (398 patients) were performed at our institution using a single fixed-bearing VVC TKA from 2007 to 2015. Mean age was 64 years (33 to 88) with 50% male (199). Index revision TKA diagnoses were: instability (n = 122, 29%), aseptic loosening (n = 105, 25%), and prosthetic joint infection (PJI) (n = 97, 23%). All devices were cemented on the epiphyseal surfaces. Femoral stems were used in 97% (n = 402) of cases, tibial stems in 95% (n = 394) of cases; all were cemented. In total, 93% (n = 389) of cases required a stemmed femoral and tibial component. Femoral cones were used in 29%, and tibial cones in 40%. Survivorship was assessed via competing risk analysis; clinical outcomes were determined using Knee Society Scores (KSSs) and range of movement (ROM). Mean follow-up was four years (2 to 10). Results. The five-year cumulative incidence of subsequent revision for aseptic loosening and instability were 2% (95% confidence interval (CI) 0.2 to 3, number at risk = 154) and 4% (95% CI 2 to 6, number at risk = 153), respectively. The five-year cumulative incidence of any subsequent revision was 14% (95% CI 10 to 18, number at risk = 150). Reasons for subsequent revision included PJI (n = 23, of whom 12 had previous PJI), instability (n = 13), and aseptic loosening (n = 11). The use of this implant without stems was found to be a significant risk factor for subsequent revision (hazard ratio (HR) 7.58 (95% CI 3.98 to 16.03); p = 0.007). KSS improved from 46 preoperatively to 81 at latest follow-up (p < 0.001). ROM improved from 96° prerevision to 108° at latest follow-up (p = 0.016). Conclusion. The cumulative incidence of subsequent revision for aseptic loosening and instability was very low at five years with this fixed-bearing VVC implant in revision TKAs. Routine use of cemented and stemmed components with targeted use of metaphyseal cones likely contributed to this low rate of aseptic loosening. Cite this article: Bone Joint J 2020;102-B(4):458–462

Introduction. Treatment of prosthetic joint infection (PJI) following total knee arthroplasty (TKA) may guided by PJI classification, taking into account infection duration and potential for biofilm formation. Debridement, antibiotics and implant retention (DAIR) is recommended for ‘post-operative’ and ‘acute’ haematogenous PJI. However, the time cut-off for ‘post-operative’ PJI varies across classification systems. Furthermore, poor DAIR success rates have been reported in acute haematogenous PJIs. This study aimed to determine the success of DAIR in a large cohort of PJIs, and assess the utility of current classification systems for predicting DAIR outcomes. Method. In this multicentre retrospective, cohort study, we identified 230 patients undergoing DAIR for first episode PJI following primary TKA. Patient demographics, disease and surgical factors were identified, and PJI subtype, post-operative antibiotic regime and treatment outcomes were recorded. Statistical analysis was performed to identify factors associated with failed DAIR, and success rates were analysed by multiple classification systems using receiver operating characteristic (ROC) curves. Results. At average follow-up of 6.9 years, DAIR failed in 46% of cases. ROC analysis found 3 month and 1 year cut-offs for ‘post-operative’ PJIs were equally predictive of outcomes (AUC=0.63). On multivariate survival analysis, DAIR failed in 63% of late haematogenous PJIs (implant age>1 year) compared to 36% of early (<1year) PJIs (OR=1.78, p=0.01). Staphylococcus aureus (OR=4.70, p<0.001) and gram negative infections (OR=2.56, p=0.031) were risk factors for DAIR failure in late PJIs. Conclusions. We found a high failure rate in late infections following TKA, irrespective of their classification as ‘acute haematogenous’ or ‘chronic’. Higher DAIR success rates were seen with implant age <1year. These findings call into question the utility of current classification systems based on duration of bacterial presence. For late infections (>1year), PJI caused by S. aureus or gram negative bacteria have a higher failure rate when treated with DAIR

Aims. With an ageing population of patients who are infected with hepatitis C virus (HCV), the demand for total knee arthroplasty (TKA) in this high-risk group continues to grow. It has previously been shown that HCV infection predisposes to poor outcomes following TKA. However, there is little information about the outcome of TKA in patients with HCV who have been treated successfully. The purpose of this study was to compare the outcomes of TKA in untreated HCV patients and those with HCV who have been successfully treated and have a serologically confirmed remission. Patients and Methods. A retrospective review of all patients diagnosed with HCV who underwent primary TKA between November 2011 and April 2018 was conducted. HCV patients were divided into two groups: 1) those whose HCV was cured (HCV-C); and 2) those in whom it was untreated (HCV-UT). All variables including demographics, HCV infection characteristics, surgical details, and postoperative medical and surgical outcomes were evaluated. There were 64 patients (70 TKAs) in the HCV-C group and 63 patients (71 TKAs) in the HCV-UT cohort. The mean age at the time of surgery was 63.0 years (. sd. 7.5; 44 to 79) in the HCV-C group and 61.7 years (. sd. 6.9; 47 to 88) in the HCV-UT group. Results. HCV-UT patients had a significantly longer mean hospital stay (3.4 days vs 2.9 days; p = 0.04), were more likely to be transferred to the intensive care unit (14.1% vs 4.3%; p = 0.04), and were significantly more often discharged to a post-acute care facility (39.4% vs 14.3%; p < 0.01). HCV-UT patients had significantly more postoperative infections (15.5% vs 4.3%; p = 0.03), surgical complications (21.1% vs 7.1%; p = 0.02), and revision TKA (12.7% vs 1.4%; p < 0.01) than HCV-C patients. Conclusion. The preoperative treatment of HCV can reduce the risk of complications, including prosthetic joint infection and revision TKA. We recommend that HCV treatment regimens should be integrated into the preoperative optimization protocol for this high-risk group of patients. Cite this article: Bone Joint J 2019;101-B:667–674

Aims

Aseptic loosening is the most common cause of failure following cemented total knee arthroplasty (TKA), and has been linked to poor cementation technique. We aimed to develop a consensus on the optimal technique for component cementation in TKA.

Background. In the setting of a “dry” aspiration, saline lavage is commonly used to obtain a sample for analysis. The purpose of this study is to prospectively determine the impact of saline lavage on synovial fluid markers in revision arthroplasty. Methods. 79 patients undergoing revision hip (19) and knee (60) arthroplasty were enrolled. Intraoperatively, prior to arthrotomy, the maximum amount of fluid possible was aspirated to simulate a dry-tap (“pre-lavage”) followed by subsequent injection with 20 mL of normal saline and re-aspiration (“post-lavage”). Pre and post-lavage synovial white blood cell (WBC) count, percent polymorphonuclear cells (%PMN), and cultures were compared. Statistical analyses utilized the Wilcoxon signed-rank test. Results. Nine patients met modified MSIS criteria for prosthetic joint infection (PJI). Pre and post-lavage %PMN were similar in septic patients (90.1% vs. 88.2%, p=0.40 for septic). Pre and post-lavage WBC counts were different in both cohorts (69,432 vs. 6,547 WBCs, p=0.008 for septic; 1,850 vs. 449 WBCs for aseptic, p<0.001). Using a pre-lavage cutoff of >80% PMN, the post-lavage aspirate correctly identified 84.6% of true positives (sensitivity) and 98.5% of true negatives (specificity). Using a pre-lavage cutoff of >3000 WBCs, the post-lavage aspirate correctly identified only 38.1% of true positives (sensitivity). As the synovial fluid WBC count increased, the correlation between pre and post-lavage %PMN was stronger (mean difference of 7.0% PMN in WBC <3000 vs. mean difference −2.9% PMN in WBC >3000, p=0.002). Of seven positive pre-lavage fluid cultures, 4 remained positive post-lavage. Conclusion. While saline lavage aspiration significantly lowers the synovial WBC count, the %PMN is well maintained, particularly at WBC counts >3000. Our findings suggest that in the setting of a dry tap where saline lavage is required to obtain a sample, the %PMN has reasonable sensitivity and specificity for the detection of PJI. For figures, tables, or references, please contact authors directly

Introduction. Robotic technology has been applied to unicompartmental knee arthroplasty (UKA) in order to improve surgical precision in prosthetic component placement, restore knee anatomic surfaces, and provide a more physiologic ligament tensioning throughout the knee range of motion. Recent literature has demonstrated high reliability of robotic-arm assisted UKA in component placement and executing a soft-tissue tensioning plan, with excellent short-term survivorship. Few studies have investigated survivorship and patients' satisfaction at longer follow-ups. Therefore, the purpose of the present study was to determine the survivorship, clinical results and patients' satisfaction of robotic-arm assisted UKAs at a mid-term follow-up, with a minimum of 5 years of follow-up. Methods. The present retrospective study includes 252 patients (260 knees) who underwent robotic-arm assisted fixed bearing metal backed UKAs at a single centre between April 2011 and July 2013. The mean age at surgery was 66.2 years (SD 8.6). Post-operatively, patients were administered the Forgotten Joint Score-12 (FJS) and asked about their satisfaction level after knee surgery (grade from 1 to 5). Post-operative complications were recorded. Failure mechanisms, revisions and reoperations were also assessed. Kaplan-Meier survival curves were calculated, considering reoperation for all causes and revision as the events of interest. Results. A total of 223 patients (231 robotic-arm assisted UKAs) were assessed at a mean follow-up of 5.8 years post-operatively (88.5% follow-up rate, min. 60 months, max. 87 months). In 219 cases, a medial robotic-arm assisted UKA was implanted, in 12 cases a lateral implant was performed. Five medial robotic-arm assisted UKAs were revised, resulting in a survivorship of 98% (C.I. 96.0%–99.1%). One case underwent revision for prosthetic joint infection, one for tibial aseptic loosening, one for post-traumatic tibial plateau fracture, and two for unexplained pain. No lateral robotic-arm assisted UKAs were revised, resulting in a survivorship of 100%. On average, the FJS and the satisfaction level resulted 75.6 (SD 26.1) and 4.2 (SD 1.0) in medial UKAs, and 81.7 (SD 15.3) and 4.4 (SD 0.8) in lateral UKAs, respectively. In medial UKAs 83% of the examined cohort reported good/excellent FJS outcomes, while 92% of the lateral UKA patients had good/excellent FJS results. In medial UKAs, male patients resulted to have better FJS (p<0.01) and higher satisfaction level (p<0.03) compared to female patients, while no outcome differences were reported in patients with BMI>30 and among different age groups. Given the small number of lateral UKAs included in the present patients' cohort, no statistical analysis was performed on this group. Conclusion. In the present study, survivorship and clinical outcomes of a large cohort of 223 patients undergoing medial and lateral robotic-arm assisted UKAs were assessed at a mean of 5.8 years of follow-up. The overall survivorship was found to be 98%, with unexplained knee pain as the most common reason for UKA revision. The present study shows that robotic-arm assisted UKA patients had lower revision rates for aseptic loosening and osteoarthritis progression compared to conventional UKA at mid-term follow-up, as reported in the literature. The good post-operative clinical scores highlight the efficacy of robotic-arm assisted UKA in restoring knee function and relieving pain. For figures, tables, or references, please contact authors directly

Introduction. Antibiotic-impregnated bone cement (AIBC) has been used for decades to treat and prevent post-operative infections in joint arthroplasty. Local delivery of antibiotics may theoretically have a bactericidal effect, however evidence supporting this is controversial and literature suggests its prophylactic use in primary total knee arthroplasty (TKA) is seldom justified. With evolving standards of care, historical data is no longer relevant in addressing the efficacy of AIBC in the contemporary TKA. The purpose of this study was to evaluate outcomes following primary TKA using AIBC and regular non-AIBC by comparing rates of surgical site infection (SSI) and prosthetic joint infection (PJI). Methods. A retrospective review was conducted of all cemented primary TKA procedures from a large institutional database between January 1, 2015 and December 31st, 2016. This identified 6,073 cases, n=2,613 in which AIBC was used and n=3,460 cases using bone cement without antibiotics. Patients were stratified into low risk and high-risk groups based on age (>65 years), BMI (>40), and Charlson Comorbidity Index (CCI; >3). Medical records were reviewed for diagnoses of SSI (skin and superficial wound infections) and PJI (deep joint infections requiring surgery) over a 2-year postoperative period. Univariate analysis and multivariate regression models were used to ascertain the effects of cement type, patient factors (age, gender, BMI, CCI), operative time, and length of stay on infection rates. Additionally, mixed models (adjusted for gender, age, race, BMI, and CCI) were built to account for surgeon variability. Results. The use of AIBC and risk group distributions were equal across the study period and no collinearity was found between the study variables. The SSI rate was 3.0% and the PJI rate was 0.8% in the total study population. Univariate analysis showed there was no significant difference in SSI rates with AIBC compared to non-AIBC (3.3% vs. 2.8%, p=0.278) or in PJI rates (1.0% vs. 0.7%, p=0.203). Multivariate logistic regression analysis adjusted for patient factors, operative time, and length of stay showed no significant difference in SSI rates with a procedure using AIBC compared to non-AIBC (OR=0.90; 95% CI, 0.66–1.23; p=0.515) and no significant difference in PJI rates (OR=1.01; 95% CI, 0.55–1.84; p=0.984). Mixed models also showed no difference in PJI rates with AIBC use after adjusting for surgeon variability as well as patient factors (gender, race, age, BMI, and CCI). Discussion. Prophylactic use of AIBC in primary TKA is not without consequence when considering the significant increase in cost and its potential side effects, namely organism specific antibiotic resistance and mechanical loosening. This study shows that even when adjusted for patient factors, procedure-related factors, and length of stay, there is no clinically significant decrease in infection rates with the use of AIBC in primary TKAs