Aims

The efficacy of saline irrigation for treatment of implant-associated infections is limited in the presence of porous metallic implants. This study evaluated the therapeutic efficacy of antibiotic doped bioceramic (vancomycin/tobramycin-doped polyvinyl alcohol composite (PVA-VAN/TOB-P)) after saline wash in a mouse infection model implanted with titanium cylinders.

The February 2023 Knee Roundup³⁶⁰ looks at: Machine-learning models: are all complications predictable?; Positive cultures can be safely ignored in revision arthroplasty patients that do not meet the 2018 International Consensus Meeting Criteria; Spinal versus general anaesthesia in contemporary primary total knee arthroplasty; Preoperative pain and early arthritis are associated with poor outcomes in total knee arthroplasty; Risk factors for infection and revision surgery following patellar tendon and quadriceps tendon repairs; Supervised versus unsupervised rehabilitation following total knee arthroplasty; Kinematic alignment has similar outcomes to mechanical alignment: a systematic review and meta-analysis; Lifetime risk of revision after knee arthroplasty influenced by age, sex, and indication; Risk factors for knee osteoarthritis after traumatic knee injury.

Aims. Although readmission has historically been of primary interest, emergency department (ED) visits are increasingly a point of focus and can serve as a potentially unnecessary gateway to readmission. This study aims to analyze the difference between primary and revision total joint arthroplasty (TJA) cases in terms of the rate and reasons associated with 90-day ED visits. Methods. We retrospectively reviewed all patients who underwent TJA from 2011 to 2021 at a single, large, tertiary urban institution. Patients were separated into two cohorts based on whether they underwent primary or revision TJA (rTJA). Outcomes of interest included ED visit within 90-days of surgery, as well as reasons for ED visit and readmission rate. Multivariable logistic regressions were performed to compare the two groups while accounting for all statistically significant demographic variables. Results. Overall, 28,033 patients were included, of whom 24,930 (89%) underwent primary and 3,103 (11%) underwent rTJA. The overall rate of 90-day ED visits was significantly lower for patients who underwent primary TJA in comparison to those who underwent rTJA (3.9% vs 7.0%; p < 0.001). Among those who presented to the ED, the readmission rate was statistically lower for patients who underwent primary TJA compared to rTJA (23.5% vs 32.1%; p < 0.001). Conclusion. ED visits present a significant burden to the healthcare system. Patients who undergo rTJA are more likely to present to the ED within 90 days following surgery compared to primary TJA patients. However, among patients in both cohorts who visited the ED, three-quarters did not require readmission. Future efforts should aim to develop cost-effective and patient-centred interventions that can aid in reducing preventable ED visits following TJA. Cite this article: Bone Jt Open 2022;3(7):543–548

Aims

Use of molecular sequencing methods in periprosthetic joint infection (PJI) diagnosis and organism identification have gained popularity. Next-generation sequencing (NGS) is a potentially powerful tool that is now commercially available. The purpose of this study was to compare the diagnostic accuracy of NGS, polymerase chain reaction (PCR), conventional culture, the Musculoskeletal Infection Society (MSIS) criteria, and the recently proposed criteria by Parvizi et al in the diagnosis of PJI.

Aims

Calprotectin (CLP) is produced in neutrophils and monocytes and released into body fluids as a result of inflammation or infection. The aim of this study was to evaluate the utility of blood and synovial CLP in the diagnosis of chronic periprosthetic joint infection (PJI).

Aims

This study aimed to explore whether serum combined with synovial interleukin-6 (IL-6) measurement can improve the accuracy of prosthetic joint infection (PJI) diagnosis, and to establish the cut-off values of IL-6 in serum and synovial fluid in detecting chronic PJI.

Aims. Currently, the US Center for Medicaid and Medicare Services (CMS) has been testing bundled payments for revision total joint arthroplasty (TJA) through the Bundled Payment for Care Improvement (BPCI) programme. Under the BPCI, bundled payments for revision TJAs are defined on the basis of diagnosis-related groups (DRGs). However, these DRG-based bundled payment models may not be adequate to account appropriately for the varying case-complexity seen in revision TJAs. Methods. The 2008-2014 Medicare 5% Standard Analytical Files (SAF5) were used to identify patients undergoing revision TJA under DRG codes 466, 467, or 468. Generalized linear regression models were built to assess the independent marginal cost-impact of patient, procedural, and geographic characteristics on 90-day costs. Results. A total of 9,263 patients (DRG-466 = 838, DRG-467 = 4,573, and DRG-468 = 3,842) undergoing revision TJA from 2008 to 2014 were included in the study. Undergoing revision for a dislocation (+$1,221), periprosthetic fracture (+$4,454), and prosthetic joint infection (+$5,268) were associated with higher 90-day costs. Among comorbidities, malnutrition (+$10,927), chronic liver disease (+$3,894), congestive heart failure (+$3,292), anaemia (+$3,149), and coagulopathy (+$2,997) had the highest marginal cost-increase. The five US states with the highest 90-day costs were Alaska (+$14,751), Maryland (+$13,343), New York (+$7,428), Nevada (+$6,775), and California (+$6,731). Conclusion. Under the proposed DRG-based bundled payment methodology, surgeons would be reimbursed the same amount of money for revision TJAs, regardless of the indication (periprosthetic fracture, prosthetic joint infection, mechanical loosening) and/or patient complexity. Cite this article: Bone Joint J 2020;102-B(7):959–964

Introduction. Aseptic loosening is a major cause of revision of total joint arthroplasty (TJA). Although crosslinked Ultra-high molecular weight polyethylene (UHMWPE) have improved wear resistance, residual radicals remaining in the material have a possibility to increase bio-reactivity of particles [2]. In this study, we attempt to evaluate the effects of irradiation and residual radicals on bio-reactivity of the material with a new method called the inverse culture method [1]. Material and methods. UHMWPE particles (10µm diameter in average, Mitsui chemicals Co., LTD) along with irradiated particles (RAD, 300kGy electron irradiation) and particles annealed after the irradiation (RAD+ANN, 100°C 72 hours) are co-incubated with mouse macrophage cell line RAW264 using the inverse culture method. The amount of TNF-α was measured with ELISA. Results and discussion. The amount of TNF-α released by macrophages reacting with virgin UHMWPE, RAD and RAD+ANN is shown in Figure 1. The horizontal axis represents the total surface area of the particles. The coefficient of determination and inclination of the approximate curve are calculated to analyze the result. The coefficient of determination suggested that cytokines released from macrophage is dose-dependent to the surface area of polyethylene particles, which was consistent with the result of our former study[1]. We use the inclination of the approximation curve in Figure 1 as an index to evaluate the bio-reactivity. The values of the index of virgin, RAD and RAD+ANN were 21×10. -4. gLm. -2. , 100×10. -4. gLm. -2. and 59×10. -4. gLm. -2. The inclination of the approximation line of RAD is significantly larger than that of virgin (test for the difference of regression line angle). These suggest that the irradiation to UHMWPE particles increases their bio-reactivity possibly due to radicals. The increased reactivity cannot be eliminated by annealing (100°C 72 hours) completely. Conclusion. Although electron irradiation increases the bio-reactivity of UHMWPE particles, annealing after the irradiation can decrease it, but cannot restore to original reactivity. For any figures or tables, please contact authors directly

Background. Standard preoperative protocols in total joint arthroplasty utilize the International Normalized Ratio (INR) to determine patient coagulation profiles. However, the relevance of preoperative INR values in joint arthroplasty remains controversial. Acceptable INR cutoff values for joint replacement are inconsistent, and are often based on studies of primary arthroplasty, or even non-orthopedic procedures. This analysis examined the relationship between preoperative INR values and post-operative outcomes in revision total hip arthroplasty (rTHA). Optimal cutoff INR values correlated with specific outcomes were subsequently determined. Methods. The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) was retrospectively queried for revision total hip arthroplasty procedures performed between 2006 and 2017. Patients with a preoperative INR collected no later than 1 day prior to surgery were further stratified for analysis. INR values which correlated with specific outcomes were determined using receiver operating characteristics (ROC) curves for each outcome of interest. The optimal cutoff INR value for each outcome was then obtained using univariate and multivariate models which determined INR values that maximized both sensitivity and specificity. Results. There were a total of 11,393 patients who underwent a revision total hip arthroplasty from 2006–2017 recorded in NSQIP. Of the 2,012 patients who met inclusion and exclusion criteria, 858 had an INR < 1.0, 931 had an INR > 1.0 to 1.25, 175 had an INR > 1.25 to 1.5, and 48 patients had an INR > 1.5. Patients with progressively higher INR values had a significantly different risk of mortality within 30 days (p=0.005), bleeding requiring transfusion (p< 0.001), sepsis (p=0.002), stroke (p<0.001), failure to wean from ventilator within 48 hours (p=0.001), readmission (p=0.01), and hospital length of stay (p< 0.001). Similar results were obtained when utilizing optimal INR cutoff values. When correcting for other factors, the following poor outcomes were significantly associated with the respective INR cutoff values (Estimate, 95% CI, p value): LOS (1.67, 1.34–2.08, p <0.001), bleeding requiring transfusion (1.65, 1.30–2.09, p<0.001), sepsis (2.15, 1.11–4.17, p 0.02), and any infection (1.82, 1.01–3.29, p 0.04). Conclusions. INR values >1.65, >1.67, >1.82, and >2.15 were correlated with increased transfusion requirements, LOS, any infection, and sepsis respectively. Therefore, even subtherapeutic elevations in INR may predict poor outcomes following revision total joint replacement. Surgeons and perioperative medical specialists should consider more stringent INR goals when optimizing patients prior to revision arthroplasty. Level of Evidence. Prognostic Level IV. For any figures or tables, please contact authors directly

Aims. The purpose of this study was to evaluate the infection-free outcome of patients underwent revision of total joint arthroplasty (TJA) for presumed aseptic causes, with positive intra-operative cultures. Patients and Methods. A retrospective cohort study was assembled with 130 patients undergoing revision knee (21 cases) or hip arthroplasty (109 cases) for presumed aseptic causes. For all patients five to seven separate intra-operative cultures were obtained and prosthesis sonication was done. Patients were diagnosed with a previously unsuspected prosthetic joint infection (PJI) if two or more cultures were. positive or a positive prosthesis sonication. Data were reviewed for demographic details, preoperative laboratory results and culture results. The endpoint was infection-free implant survival at 24 months. Results. Patients with unsuspected PJI was 16 out of 130 (12,3%). Following revision surgery, the rate of infection-free implant survival in patients with an unsuspected PJI was 68,8% (95% confidence intervals (CI) 45,6 to 92) at two years compared. with 94,7% (95% CI 90,5 to 98,9) in patients without PJI (p = 0.001). Conclusion. Around 12% of positive cultures can be expected after TJA aseptic revision surgery; in these cases, the rate of infection-free implant survival is lower than in cases without PJI

The AAOS clinical practice guideline for diagnosis of periprosthetic joint infection (PJI) and the MSIS definition of PJI were both “game changers” in terms of diagnosing PJI and the reporting of outcomes for research. However, the introduction of new diagnostic modalities, including biomarkers, prompted a re-look at the diagnostic criteria for PJI. Further there was a desire to develop an evidence-based, validated algorithm for the diagnosis of PJI. This multi-institutional study led by Dr. Jay Parvizi examined revision total joint arthroplasty patients from three academic institutions. For development of the algorithm, infected and aseptic cohorts were defined. PJI cases were defined using only the major criteria from the Musculoskeletal Infection Society (MSIS) definition (n=684). Aseptic cases underwent revision for a non-infective indication and did not show evidence of PJI or undergo a reoperation for any reason within 2 years (n=820). Risk factors, clinical findings, serum and synovial markers as well as intraoperative findings were assessed. A stepwise approach using random forest analysis and multivariate regression was used to generate relative weights for each of the various variables assessed at each stage to create an algorithm for diagnosing PJI using the 3 most important tests from each step. The algorithm was formally validated on a separate cohort of 422 patients, 222 who were treated with a 2-stage exchange for PJI who subsequently failed secondary to PJI within one year and 200 patients who underwent revision surgery for an aseptic diagnosis and had no evidence of PJI within two years and did not undergo a reoperation for any reason. The first step in evaluating PJI should include a physical examination to identify a sinus tract, followed by serum testing for C-reactive protein (cut-off value 1mg/dl), D-dimer (cut-off value 860ng/mL) and/or erythrocyte sedimentation rate (cut-off value 30mm/hr) in that order of importance. If at least one of these are elevated, or if there is a high clinical suspicion, joint aspiration should be performed, sending the fluid obtained for a synovial fluid white blood-cell (cut-off value 3,000 wbc/uL) or leukocyte esterase strip testing, polymorphonuclear percentage (cut-off value 80%) and culture. Alpha defensin did not show added benefit as a routine diagnostic test. Major diagnostic criteria are the same whereby the presence of a sinus tract or (2) positive cultures showing the same organism defines PJI. Special care should be taken in cases of ALTR (failed metal-on-metal bearing), crystalline deposition disease, inflammatory arthritis flares or slow growing organisms. In the rare cases where no fluid is obtained at the time of an attempted aspiration and revision surgery is not planned, then this is the rare scenario where nuclear imaging (my preference is an indium labeled white blood cell scan) or a biopsy can be performed. The updated definition of PJI demonstrated a higher sensitivity of 97.7% when compared to the MSIS criteria (79.3%) and the ICM definition (86.9%), with a similar specificity of 99.5%. However, just over 2% of patients examined do fall into the “inconclusive” category. The proposed diagnostic algorithm demonstrated a high overall sensitivity (96.9%) and specificity (99.5%)

Introduction. Despite recent advances in the diagnosis of periprosthetic joint infection(PJI), identifying the infecting organism continues to be a challenge, with up to a third of PJIs reported to have negative cultures. Current molecular techniques have thus far been unable to replace culture as the gold standard for isolation of the infecting pathogen. Next- generation sequencing(NGS) is a well-established technique for comprehensively sequencing the entire pathogen DNA in a given sample and has recently gained much attention in many fields of medicine. Our aim was to evaluate the ability of NGS in identifying the causative organism(s) in patients with PJI. Methods. After obtaining Institutional Review Board approval and informed consent for all study participants, samples were prospectively collected from 148 revision total joint arthroplasty procedures (83 knees, 65 hips). Synovial fluid, deep tissue and swabs were obtained at the time of surgery and shipped to the laboratory for NGS analysis (MicroGenDx). Deep tissue specimens were also sent to the institutional laboratory(Thomas Jefferson University Hospital) for culture. PJI was diagnosed using the Musculoskeletal Infection Society(MSIS) definition of PJI. Statistical analysis was performed using SPSS software. Results. Fifty-five revisions were considered infected; culture was positive in 40 of these (40/55, 72.7%), while NGS was positive in 47 (47/55, 85.5%). Among the positive cultures, complete concordance between NGS and culture was observed in 33 cases (33/40, 82.5%). One case was partially discordant between NGS and culture, with culture detecting three organisms as opposed to one organism on NGS. One case showed complete discordance with NGS and culture detecting different organisms. Three patients with negative NGS results had positive cultures. In another two cases culture simply reported the gross morphology of the organism but the phenotype was not identified, while NGS was able to definitively identify an organism. Among the 15 cases of culture-negative PJI, NGS was able to identify an organism in 10 cases (10/15, 66.7%). These data are summarized in Figure 1. Ninety-three revisions were considered to be aseptic; NGS exclusively identified microbes in 15 of 93 “aseptic” revisions (16.1%) and culture exclusively isolated an organism in 4 of 93 cases(5.3%). One case was positive on both NGS and culture, however the results were discordant from each other. The remaining cases (73/93, 78.5%) were both NGS and culture negative. NGS detected several organisms in most positive samples, with a greater number of organisms detected in aseptic compared to septic cases (6.8 vs. 4.0, respectively). Discussion. NGS was able to detect a pathogen in two-thirds of culture-negative cases and demonstrated a high rate of concordance with culture in culture-positive cases. The rate of false positives was low compared to earlier studies using molecular techniques. Our findings also suggest that some cases of PJI may be polymicrobial and escape detection using conventional culture. NGS may be a useful adjunct for identifying the causative organism(s) in PJI, particularly in the setting of negative cultures. Further study is required to determine the significance of isolated organisms in samples from patients who are not thought to be infected

Aim. What is the fate of revision total joint arthroplasty, when conventional tissue sample culture (TSC) is negative and sonication fluid culture (SFC) is positive, in terms of re-revision?. Method. We prospectively analyzed explanted prosthetic materials from 211 consecutive cases of total hip and knee arthroplasty revision surgery performed on any indication during a one year period. We used a sonication apparatus and protocol that was previously described [Borens et al, 2013. J Orthop Res]. Sampling of five periprosthetic tissue biopsies was performed according to the local protocol and incubated for 5 days. In our non-interventional study design, clinicians were blinded to the results from sonication-culture, which were not used for the subsequent treatment strategy. In cases with suspected deep infection, thorough debridement was performed during revision surgery, and routine antibiotic treatment was dicloxacillin for 6–8 weeks. Patients were routinely seen in the outpatient clinic after 3 and 12 months, where clinical examination and any antibiotic treatment were documented. Minimum follow-up was 1 year. This cohort study is reported according to the STROBE guidelines. Results. Microbial findings in TSC and SFC were similar in 41/211 cases. Additional 11/211 cases were identified with positive SFC, despite negative in conventional culture. Of these, 8/11 cases with suspected prosthetic joint infection (PJI) a strategy of revision and empirical antibiotic therapy was completed. Another 3/11 cases with suspected aseptic failure, partial 1-stage revisions were performed with no subsequent antibiotic therapy. Re-revisions were necessary in 5/11 cases of expected PJI, and 2/11 of these ended up with permanent Girdlestone status. A strategy of antibiotic suppression was implemented in 1/11 case. Another 1/11 patient diseased in circulatory failure 4 days after 2nd stage operation. In 3/11 cases the painful joint prosthesis is still unsolved after 1 year, and only 1/11 case had an asymptomatic prosthesis at follow-up after 1 year. Culture results of the subsequent revisions in this small cohort shows several links to the microbiological findings in SFC. Conclusions. We identified 11/211 revisions of total joint arthroplasty, where conventional TSC was negative and SFC was positive. The fate of these cases included re-revision in 5/11. From a clinical perspective, patients with additional microbial findings by SFC had a discouraging prognosis and may represent true positive findings that have to be taken into consideration in the infection treatment

Aims

We present our experience of using a metal-backed prosthesis and autologous bone graft to treat gross glenoid bone deficiency.

Total joint replacement is a successful clinical intervention. However, aseptic loosening due to wear related particulate debris is still one of the most frequent reasons for late revision of total joint replacement. This lecture gives an overview about the application of methods to study wear and friction in total joint replacements (e.g. hip, knee, shoulder). This involves complex joint simulation conditions as well as analytical assessments. Regarding joint simulation the focus will be on ligament stabilized joints. New approaches will be shown and discussed. Furthermore, analytical methods to study the release of wear products in term of solid particles and soluble complexes like metal ions will be presented

Aims

The aim of this study was to compare the results of 16S/28S rRNA sequencing with the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and synovial fluid analysis in the diagnosis of prosthetic joint infection (PJI).

Stems are a crucial part of implant stabilization in revision total knee arthroplasty. In most cases the metaphyseal bone is deficient, and stabilization in the diaphyseal cortical bone is necessary to keep the implant tightly fixed to bone and to prevent tilt and micromotion. While sleeves and cones can be effective in revision total joint arthroplasty, they are technically difficult and may lead to major bone loss in cases of loosening or infection, especially if the stem is cemented past the cone. A much more conservative method is to ream the diaphysis to the least depth possible to achieve tight circumferential fixation, and to apply porous augments to the undersurface of the tibial tray or inner surface of the femoral component to allow them to bottom out against the bone surface and apply compressive load. If a robust, strong taper, stem and component combination is used, rim contact on only one side is necessary to achieve rigid permanent fixation. Porous and non-porous stems are available. The non-porous stems should have a spline surface that engages the diaphyseal bone and achieves rigid initial fixation but does not provide long-term axillary support. In that way the porous rim-engaging surface can bear compressive load and finally unload the stem and taper junction. Correctly designed stems do not stress relieve unless they are porous-coated. In situations where metaphyseal bone is not available, porous-coated stems that link to hinge prostheses are a very important part of the armamentarium in complex revision arthroplasty. Use of stems requires experience and special technique. Slight underreaming and initial scratch fit are necessary techniques. This does not result in tight fixation every time because split of the cortex does occasionally occur. In most cases these splits do not need to be repaired, but when there is a question, an intra-operative x ray should be taken and the surgeon should be prepared to repair the fracture. Stems are an essential part of revision total knee arthroplasty. A tightly fit stem in the diaphysis is necessary for fixation when metaphyseal bone is deficient. No amount of cement pressed into the deficient metaphyseal bone will substitute for rigid stem fixation