Aim. The current antibiotic treatment of periprosthetic joint infection (PJI) is optimized by measuring concentrations in plasma. However, it remains unclear whether effective concentrations of the antibiotics are reached at the site of PJI. Nonetheless, adequate target site concentrations are important to achieve effective eradication of the micro-organism. In order to determine the efficacy of cefuroxime and flucloxacillin in synovial fluid, synovial tissue and bone tissue in relation to the minimal inhibitory concentration (MIC) of the pathogen causing the PJI, we perform a pharmacokinetic/pharmacodynamic (PK/PD) study. Therefore, we aimed to develop validated analytical methods for analysis of cefuroxime and flucloxacillin in synovial fluid, synovial tissue and bone tissue. Method. Blank samples of synovial fluid, synovial tissue and bone tissue were obtained by orthopedic surgeons during surgery. For validation the samples of each matrix were spiked with both cefuroxime and flucloxacillin. Synovial tissue and bone tissue was pulverized with a mikro-dismembrator. Samples were kept frozen at −20°C until analysis. After a sample preparation quantification of cefuroxime and flucloxacillin in each matrix was performed on the ultra-performance convergence chromatography-tandem
Introduction. Autologous fat grafting has favourable potential as a regenerative strategy and is the current gold-standard to repair large contour defects, as needed in breast reconstruction after mastectomy and traumatic soft tissue reconstruction. Clinically, there is a limit on the volume of lipoaspirate which can be utilised to repair a soft-tissue defect. Surgical complications are the result of poor structural fidelity of lipoaspirate and graft resorption as a filling material and are hindered further by poor graft vascularisation. This study aims to develop injectable lipoaspirate-derived adipose tissue grafts with enhanced biologically and clinically-admissible structural and functional properties adopting light photocrosslinking of unmodified lipoaspirate. Methods. Patient-derived lipoaspirate was harvested and crosslinked using novel photoinitiator and exposure to visible light (wavelength 450nm) in surgery, establishing bonds between extracellular matrix (ECM) proteins within the material. The degree of crosslinking was tuned (photoinitiator concentration, light exposure, light intensity) and covalent bond formation measured using
Aim. Antibiotic concentration at the infected site is a relevant information to gain knowledge about deep-seated infections. The combination of antibiotic therapy and debridement is often indicated to treat these infections. At University Hospital Basel the most frequently administered antibiotic before debridement is amoxicillin in combination with clavulanic acid. Amoxicillin is a fragile beta-lactam antibiotic that brings multiple challenges for its quantification. As for many sample materials only little material is available, the aim of this work was to establish a sensitive and reliable quantification method for amoxicillin that only requires a small sample mass. We did not quantify clavulanic acid as we focused on the drug with antibiotic action. Method. Usually discarded sample material during debridement was collected and directly frozen. The thawed tissues were prepared using simple protein precipitation and manual homogenization with micro pestles followed by a matrix cleanup with online solid-phase extraction. Separation was performed by HPLC followed by heated electrospray ionization and tandem
Aim. Prosthetic joint infections (PJI) are a common reason for revisions in patients that underwent total arthroplasty of the hip (THA) or knee (TKA). Extensive antibiotic treatment follows while a clear understanding of target site concentrations is lacking. The aim is to investigate the target site concentrations, like bone and synovial tissue concentrations, which consequently may lead to an optimisation of the dosing regiments of cefuroxime of PJI patients suffering from pain and immobility. Dosing optimisation may lead to a reduced risk of (re-)infection and adverse effects like renal-insufficiency and therefore lower health-care costs. Method. Patients (n=26) with PJI of hip or knee undergoing a one- or two-stage revision treated with cefuroxime were included as part of the ASTERICS study. During implant removal two samples were collected 15-30 and 60-120 minutes after IV infusion of plasma, bone tissue and synovial tissue and one synovial fluid sample. Samples were analysed using a UltraPerformance Convergence Chromotography – quadruple
Aim. Dalbavancin is a lipoglycopeptide with a broad antimicrobial spectrum against Gram-positive bacteria and effect against microorganisms in biofilm in vitro. Its pharmacokinetic properties, with an exceptionally long half-life of approximately 300 hours, allow for simplified administration that may be of value in the long-term treatment of bone and joint infections, such as prosthetic joint infections (PJIs). Several case reports and case series with “off-lable” treatment with dalbavancin of PJIs exist, but the optimal dosing regimen remains to be defined. Therapeutic drug monitoring (TDM) is recommended for treatment with >2 doses of dalbavancin. In the absence of TDM, the Swedish national guidelines for bone and joint infections (2023, . www.infektion.net. ) recommends a loading dose of dalbavancin 1,500 mg on day 1 and 1,500 mg on days 8 – 14, after which from day 28 1,000 mg is given biweekly or 500 mg every week. The aim of the present study was to determine trough levels of dalbavancin in patients with long-term treatment of PJIs according to the national guidelines. Method. Twelve patients with PJI were treated with at least 6 doses of dalbavancin, of which the first two doses were 1500 mg and the following doses were 1000 every second week, and prospectively sampled biweekly for determination of serum concentrations (trough levels) of dalbavancin which was measured by liquid chromatography coupled to electrospray tandem
Aim. S. aureus and S. epidermidis remain the leading biofilm-forming agents causing orthopedic implant-associated infections (OIAI), but other coagulase-negative Staphylococcus (CoNS) with clinical importance is emerging. Besides, few studies have assessed specific genomic traits associated with patient outcome. This is a preliminary descriptive study of phenotypic and genomic features identified in clinical isolates of S. aureus and CoNS isolates recovered from OIAIs patients that progressed to treatment failure. Methods. Ten isolates were identified by matrix-time-of-flight laser-assisted desorption
Background. Surgical site infection following spine surgery is associated with increased morbidity, mortality and increased cost for the health care system. The reported pooled incidence is 3%. Perioperative antibiotic prophylaxis is a key factor in lowering the risk of acquiring an infection. Previous studies have assessed perioperative cefuroxime concentrations in the anterior column of the cervical spine with an anterior surgical approach. However, the majority of surgeries are performed in the posterior column and often involve the lumbar spine. Accordingly, the objective was to compare the perioperative tissue concentrations of cefuroxime in the anterior and posterior column of the same lumbar vertebra using microdialysis in an experimental porcine model. Method. The lumbar vertebral column was exposed in 8 female pigs. Microdialysis catheters were placed for sampling in the anterior column (vertebral body) and posterior column (posterior arch) within the same vertebra (L5). Cefuroxime (1.5 g) was administered intravenously over 10 min. Microdialysates and plasma samples were continuously obtained over 8 hours. Cefuroxime concentrations were quantified by Ultra High Performance Liquid Chromatography Tandem
Aim. It is traditionally stated that around 80% of all periprosthetic joint infections (PJI) are caused by well-known gram-positive organisms such as Staphylococcus aureus. With the advances in diagnostic modalities and improved abilities to isolate infective organisms, we believe the organism profile causing PJI has changed over time and includes numerous other organisms that were either not recognized as pathogens and/or considered as contaminants. Method. We retrospectively reviewed the medical records of 1,363 patients with confirmed PJI (559 THA and 804 TKA) who received treatment at our institution between 2000 and 2019. Pertinent data related to demographics, microbiological findings, and outcome of treatment were collected. Organisms were differentiated using culture or confirmed by Matrix-Assisted Laser Desorption Ionization-time of flight (MALDI-tof)
Osteogenesis Imperfecta (OI) is a heritable bone disorder characterized by bone fragility and often caused by mutations in the Type I collagen-encoding genes COL1A1 and COL1A2. The pathophysiology of OI, particularly at the cellular level, is still not well understood. This contributes to the lack of a cure for this disorder as well as an effective preventive or management options of its complications. In the bone environment, mesenchymal stem cells (MSCs) and osteoblasts (Ob) exert their function, at least partially, through the secretion of extracellular vesicles (EV). EV is a heterogeneous group of nanosized membrane-enclosed vesicles that carry/transfer a cargo of proteins, lipid and nucleic acids from the secreting cell to its target cells. Our objective is to characterize EVs secreted by human control (HC)- and OI-MSCs and their derived Obs, with focus on their protein content. We hypothesize that there will be differences in the protein content of EVs secreted by OI-Obs compared to HC-Ob, which may indicate a deviation from healthy Ob behavior and, thus, a role in OI pathophysiology. MSCs were harvested from the adipose tissue of four COL1A1-OI and two HC patients. They were proliferated in an EV-depleted media, then induced to differentiate to extracellular matrix (ECM)-producing osteoblasts, which then gets mineralized. EVs secreted by MSCs (MSC-EV) and Obs (Ob-EV) were then purified and concentrated. Using liquid chromatography- tandem
Aim. The purpose of this study was to compare the presence of P.acnes on the skin after topical pre-operative application with benzoyl peroxide (BPO) to chlorhexidine soap (CHS) and whether this also affected skin recolonization after surgical preparation and draping. Method. Forty volunteers – twenty-four men and sixteen women were randomized to pre-operative topical treatment at home with either CHS or BPO in the area of a delto-pectoral approach of their left shoulder. The right served as a control. Five skin swabs were taken in a standardized manner on different occasions: before and after topical treatment, after surgical skin preparation and sterile draping and 120 minutes after draping. A fifth sample was taken on the contralateral untreated side as a control when the patient was draped. The draping took place in an operating room with laminar air flow and skin preparation was performed for 2 minutes with 0.5% chlorhexidine solution in 70% ethanol according to the recommendations of the Swedish National Board of Health and Welfare. Bacterial colonies were then analyzed on agar plates by colony forming units (CFU) and surface characteristics. P.acnes were identified with matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF)
Aim. Thermal stability is a key property determining the suitability of an antibiotic agent for local application. Long-term data describing thermal stability without interference from carrier materials are scarce. Method. In this study, a total of 38 common antibiotic agents have been maintained at 37 °C in saline solution, and degradation and antibacterial activity assessed over 6 weeks. The impact of an initial supplementary heat exposure mimicking exothermically-curing bone cement has also been tested. Antibiotic degradation was assessed by chromatography coupled to
Aim. Propionibacterium acnes is a skin commensal colonizing the deeper structures of the pilous bulb. It is responsible for 5–10% of lower limb prosthetic joint infections (PJI) but accounts for as many as 50% of shoulder arthroplasty infections. P. acnes PJIs characteristically feature limited systemic inflammation, limited polymorphonuclear infiltration and clinical signs compatible with aseptic loosening. All current microbiological definitions of PJI require two or more identical commensal isolates to be recovered from the same procedure to diagnose PJI to increase specificity and rule out contamination. Whereas the antimicrobial susceptibility patterns of coagulase negative staphylococci are highly polymorphic and commonly allow the ready distinction of unrelated strains, P. acnes shows a highly stereotypical susceptibility profile and it is impossible to phenotypically assess the clonal relationship of isolates. In order to determine the clonal relationship of multiple P. acnes isolates recovered from arthroplasty revisions, we analyzed by multi-locus sequence typing (MLST) P. acnes isolates grown from PJI in a reference center for bone and joint infection. Method. We retrospectively selected all cases of microbiologically documented monomicrobial PJI caused by P. acnes diagnosed in our center from January 2009 to January 2014. Microorganisms were identified by MALDI-TOF
Background. Recent clinical studies have suggested that systemic metal ion levels are significantly elevated at midterm follow-up after ceramic-on-metal (COM) bearing. However, it is not clear whether there is a correlation between patient- and surgical-related factors including the lifestyle and elevated levels of serum metal ions following COM total hip arthroplsty (THA). Material and Methods. Two hundred and one patients (234 hips) including 121 COM patients (140 hips) and 80 non-COM patients (94 hips) were enrolled in accordance with the inclusion criteria. The patients were divided into three groups based on the type of surgical bearings used. The Harris Hip Score (HHS), University of California, Los Angeles (UCLA) activity scale score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were measured, and radiographs were obtained for the analysis. Serum metal ion levels of cobalt and chromium were measured using a high-resolution inductively coupled plasma
Tranexamic acid (TEA), an antifibrinolytic agent, is routinely used for reduction of blood loss in total hip arthroplasty (THA). However, use of intravenous (IV) TEA has been questioned due to safety concerns and a lack of biochemical data in the arthroplasty literature. Tranexamic acid given topically as a periarticular solution is a promising alternative route of administration. The purpose of this study is to identify differences in systemic absorption for intravenous and topical TEA administered during primary THA. In a blinded randomised controlled trial of patients undergoing primary cementless total hip arthroplasty, 29 participants received a weight-based bolus infusion of intravenous TEA (20 mg/kg) 10 minutes prior to skin incision. Conversely, 15 participants received a 1.5 g bolus dose of TEA administered topically into the periarticular region of the operative hip at the time of arthrotomy closure. A blood sample was drawn one hour post-administration for measurement of serum TEA concentration (µg/mL) by tandem
Osteoarthritis (OA) is the most common form of arthritis worldwide. It is a major cause of disability in the adult population with its prevalence expected to increase dramatically over the next 20 years. Although current therapies can alleviate symptoms and improve function in early course of the disease, OA inevitably progresses to end-stage disease requiring total joint arthroplasty. Mesenchymal stromal cells (MSCs) have emerged as a candidate cell type with great potential for intra-articular (IA) repair therapy. However, there is still a considerable lack of knowledge concerning their behaviour, biology and therapeutic effects. To start addressing this, we explored the secretory profile of bone marrow derived MSCs in early and end-stage knee OA synovial fluid (SF). Subjects were recruited and categorised into early [Kellgren-Lawrence (KL) grade I and II, n=12] and end-stage (KL grade III and IV, n=11) knee OA groups. The SF proteome of early and end-stage OA was tested before and three days after the addition of bone marrow MSCs (16.5×10^3, single donor) using multiplex ELISA (64 cytokines) and
The ATTUNE™ Knee System (DePuy Synthes) comprises of a tibial insert that is made from AOX™, an antioxidant-stabilized polyethylene. The antioxidant used in AOX is pentaerythritol tetrakis [3-(3, 5-di-tertiary butyl-4-hydroxyphenyl)] propionate (PBHP). A biological risk assessment of the degradation products arising from PBHP has been performed. This assessment focuses on the requirements of ISO 10993–1:2009, ISO 14971:2007, and the Medical Device Directive 93/42/EEC. Because the orthopedic implant is a permanent implant, consideration has been given to all relevant endpoints defined by ISO 10993–1 Biological evaluation of medical devices – Part 1: Evaluation and testing within a risk management process. Comprehensive biocompatibility testing including long-term (26 weeks) subcutaneous implantation has been conducted which confirms the biosafety of the polyethylene compound[1]. In addition to the biological safety testing completed, the overall safety and the associated toxicological risk of exposure to degradation products of PBHP has been given due consideration. The guidelines for the Threshold for Toxicological Concern (TTC) provided by The Product Quality Research Institute (PQRI) Leachables and Extractables Working Group were used in the assessment[2]. This working group is a collaboration of chemists and toxicologists from the U.S. Food and Drug Administration (FDA), industry, and academia. The TTC principle allows safety assessment in the absence of substance-specific hazard data, based on very low levels of exposure to that substance. A Margin of Safety (MOS) is calculated as the ratio of the threshold safety value to the actual exposure quantities determined and used in the assessment. A MOS value greater than 1 is typically judged by risk assessors and regulatory bodies to be unlikely to cause harm and the risk may be considered low. The identity of the degradation products as well as the corresponding 30-day leachable quantities from a water:acetone extraction media has been previously reported [3] and provided here (Table 1). The amount of leachables determined from Table 1 for all products were well below the TTC of 150 ng/device and hence no toxicological risks were identified for these compounds. In order to further examine the toxicological risk assessment, aggressive extraction using Dynamic Head Space (DHS) extraction was done and analytical testing was performed on the degradation products of PBHP using gas chromatography/
Introduction. Modern metal-on-metal bearing resurfacings have been in use for nearly two decades. Local and systemic metal ion exposure continues to cause concern. We could not find a prospective metal ion study in such patients with a 10-year follow-up. This is the first ten year prospective study of metal ion levels in blood and their release in urine following hybrid fixed metal-on-metal surface arthroplasty. Methods. Twenty six patients were included in an ongoing longitudinal metal ion study of patients with unilateral metal-on-metal hip resurfacings. Three of them were excluded due to subsequent contralateral resurfacing and one has relocated abroad. Cobalt and chromium levels were assessed in 12 hour urine collections before and periodically after operation (5 days to 10 years) using high resolution plasma
It is thought that metal ions from metal on metal bearing hip replacements cause DNA damage and immune dysfunction in the form of T cell mediated hypersensitivity. To explore the hypothesis that there is a relationship between metal ion levels and DNA damage and immune dysfunction in matched patient groups of hip resurfacings and standard hip replacements reflected in the levels of lymphocyte subtypes (CD3+ T cells, CD4+ T helper cells, CD8 +T cytotoxic/suppressor cells, CD16 +Natural Killer and CD19+ B cells) in peripheral blood samples, we analysed peripheral blood samples from 68 patients: 34 in the hip resurfacing group and 34 in the standard hip arthroplasty group. Samples were analysed for counts of each sub-group of lymphocyte and cytokine production. Whole blood cobalt and chromium ion levels were measured using inductively-coupled
Introduction. Large diameter metal-metal total hip replacements (MM THRs) offer the advantages of low wear and low dislocation risk and are being increasingly used in high-demand patients whose bone quality rules out the possibility of a hip resurfacing. However suggests that large headed MM devices may result in greater systemic metal exposure compared to small diameter bearings. This raises fresh concerns of elevated systemic metal levels. Methods. Whole blood concentrations and daily output of cobalt and chromium in 28 patients with unilateral large diameter MM THRs (42 to 54mm bearings) were studied at 1-year follow-up. These were compared with the whole blood levels in 20 patients at 1 year and daily output of metal ions in 28 patients with 28mm MM THRs at 1 to 3 years. Both bearings are made of high carbon cobalt-chrome alloy, the larger bearing is as-cast alloy and the smaller is wrought alloy. High resolution inductively coupled plasma
Introduction. Higher concentrations of metal ion levels after Metal-on-metal (MoM) THA are a cause for concern. Elevated cobalt (Co) and chromium (Cr) ion levels in the blood indicate metal wear, and may predict secondary soft-tissue damage (adverse reaction to metal debris; ARMD). Although, it is well known that concentrations of metal ion levels are elevated in the short term after MoM, the long-term consequences in ion concentration and risk factors for increased ion levels are not clarified. We sequentially investigated the postoperative Co and Cr ion levels after MoM THA and the relationship between the metal ion levels and several risk factors. Materials and Methods. We reviewed the data on one hundred and eighty six patients of two hundred ninety one MoM THA cases. The one hundred eighty six patients were measured at least three times after a MoM THA surgery over a five year (2005–2010) period in our institution. Serum cobalt and chromium levels were measured by inductor coupled plasma –
