C. Difficile infections in elderly patients with hip fractures is associated with high morbidity and mortality. Antibiotic regimens with penicillin and its derivatives is a leading cause. Antibiotic prophylactic preferences vary across different hospitals within NHS. We compared two antibiotic prophylactic regimens - Cefuroxime only prophylaxis and Teicoplanin with Gentamicin prophylaxis in fracture neck of femur surgery, and evaluated the incidence of C. Difficile diarrhea and Surgical Site Infection (SSI). To assess the Surgical Site Infection and C. Difficile infection rate associated with different regimens of antibiotics prophylaxis in fracture neck of femur surgery. Data was analyzed retrospectively. Neck of femur fracture patients treated surgically from 2009 in our unit were included. Age, gender, co morbidities, type of fracture, operation, ASA grade was collected. 1242 patients received Cefuroxime only prophylaxis between January 2009 and December 2012 (Group 1) and 486 patients received Teicoplanin with Gentamicin between October 2015 and March 2017 (Group 2). There were 353 males and 889 female patients in Group 1 and 138 males and 348 female patients in Group 2. The co morbidities in both groups were comparable. Incidence of C. Difficile diarrhea and Surgical Site Infection (SSI) was noted. Statistical analysis with chi square test was performed to determine the ‘p’ value. C. Diff diarrhea rate in Group 2 was 0.41 % as compared to 1.29 % in Group 1. The Surgical Site Infection (SSI) rate in Group 2 was 0.41 % as compared to 3.06 % in Group 1. The comparative results were statistically significant (p = 0.0009). Prophylactic antibiotic regimen of Teicoplanin with Gentamicin showed significant reduction in C. Difficile diarrhea & Surgical Site Infection in fracture neck of femur patients undergoing surgery

Introduction. Cancellous and cortical bone used as a delivery vehicle for antibiotics. Recent studies with cancellous bone as an antibiotic carrier in vitro and in vivo showed high initial peak concentrations of antibiotics in the surrounding medium. However, high concentrations of antibiotics can substantially reduce osteoblast replication and even cause cell death. Objectives. To determine whether impregnation with gentamycine impair the incorporation of bone allografts, as compared to allografts without antibiotic. Materials and method. Seventy two healthy rabbits (24 rabbits in each group) were used for this study. Bone defects (3-mm diameter, 10-mm depth) were created in the femur. Human femoral head prepared according to the Marburg bone bank system was used as bone allograft. In the experimental groups, in 1 group - the defects were filled with bone allografts, in 2 group – Perforated Gentamycin-impregnated bone allografts. The control group did not receive any filling. The animals were killed after 14, 30 and 60 days. Evaluations consisted of X-ray plain radiography, histology at 14-, 30- and 60-days post-surgery. Results. Active osteoblast activity and active formation of new bones were detected around the defect area in all groups, but the amount of new bone formation was greater in the experimental groups than the control group. We found no statistically significant differences in the rate of bone formation between 1 and 2 groups at 14, 30 and 60 days in any of the parameters studied. X-ray results showed no significant difference in bony callus formation around allografts in 1 and 2 groups. In contrast, no significant callus formation was observed in the control group. Conclusion. The use of gentamycin-impregnated bone allografts may be of value in procedures performed at the site of osteomyelitis which require a second stage reconstruction with impacted bone grafting techniques

Objectives. The objective of this study was to compare the elution characteristics, antimicrobial activity and mechanical properties of antibiotic-loaded bone cement (ALBC) loaded with powdered antibiotic, powdered antibiotic with inert filler (xylitol), or liquid antibiotic, particularly focusing on vancomycin and amphotericin B. Methods. Cement specimens loaded with 2 g of vancomycin or amphotericin B powder (powder group), 2 g of antibiotic powder and 2 g of xylitol (xylitol group) or 12 ml of antibiotic solution containing 2 g of antibiotic (liquid group) were tested. Results. Vancomycin elution was enhanced by 234% in the liquid group and by 12% in the xylitol group compared with the powder group. Amphotericin B elution was enhanced by 265% in the liquid group and by 65% in the xylitol group compared with the powder group. Based on the disk-diffusion assay, the eluate samples of vancomycin-loaded ALBC of the liquid group exhibited a significantly larger inhibitory zone than samples of the powder or the xylitol group. Regarding the ALBCs loaded with amphotericin B, only the eluate samples of the liquid group exhibited a clear inhibitory zone, which was not observed in either the xylitol or the powder groups. The ultimate compressive strength was significantly reduced in specimens containing liquid antibiotics. Conclusions. Adding vancomycin or amphotericin B antibiotic powder in distilled water before mixing with bone cement can significantly improve the efficiency of antibiotic release than can loading ALBC with the same dose of antibiotic powder. This simple and effective method for preparation of ALBCs can significantly improve the efficiency of antibiotic release in ALBCs. Cite this article: Bone Joint Res 2014;3:246–51

We used a goat model of a contaminated musculoskeletal defect to determine the effectiveness of rapidly-resorbing calcium-sulphate pellets containing amikacin to reduce the local bacterial count. Our findings showed that this treatment eradicated the bacteria quickly, performed as well as standard polymethylmethacrylate mixed with an antibiotic and had many advantages over the latter. The pellets were prepared before surgery and absorbed completely. They released all of the antibiotic and did not require a subsequent operation for their removal. Our study indicated that locally administered antibiotics reduced bacteria within the wound rapidly. This method of treatment may have an important role in decreasing the rate of infection in contaminated wounds

Allograft bone is widely used in orthopaedic surgery, but peri-operative infection of the graft remains a common and disastrous complication. The efficacy of systemic prophylactic antibiotics is unproven, and since the graft is avascular it is likely that levels of antibiotic in the graft are low. Using an electrical potential to accelerate diffusion of antibiotics into allograft bone, high levels were achieved in specimens of both sheep and human allograft. In human bone these ranged from 187.1 mg/kg in endosteal (. sd. 15.7) to 124.6 (. sd. 46.2) in periosteal bone for gentamicin and 31.9 (. sd. 8.9) in endosteal and 2.9 (. sd. 1.1) in periosteal bone for flucloxacillin. The antibiotics remained active against bacteria in vitro after iontophoresis and continued to elute from the allograft for up to two weeks. Structural allograft can be supplemented directly with antibiotics using iontophoresis. The technique is simple and inexpensive and offers a potential means of reducing the rate of peri-operative infection in allograft surgery. Iontophoresis into allograft bone may also be applicable to other therapeutic compounds

Bone infection occurring after fractures or orthopedic surgery can progress to the chronic stage and lead to poor results of treatment. Optimal treatment of chronic osteomyelitis are stabilization the fracture, biological recovery of bone defects and destroy bacterial infection. Traditional methods of treatment are systemic administration of antibiotics and surgical treatment of active infection focus. Systemic antibiotics are part of the standard therapy after surgical treatment of infected bone, but their effectiveness is limited due to malnutrition and low absorption at the site of infection. Moreover, long-term treatment and higher doses are associated with serious side effects. The aim of this investigation was to study the results of the complex treatment of patients with chronic osteomyelitis using biodegradable nanomaterials “PerOssal” as antibiotic delivery system. The study was performed at Regional center traumatology and orthopedics, Karaganda, Kazakhstan. A total 20 patient with post-traumatic/post-operative osteomyelitis were included in this open-label, prospective study. Bacteriological examination was taken with the determination of culture and sensitivity test preoperatively, during and postoperatively. After radical surgical debridement and ultrasound cavitation, the bone cavity was full filled with Perosal which can be loaded with different antibiotics depending from the antibiotic sensitivity test. Postoperative wound is completely was sutured. Systemic antibiotic treatment are allowed. The course of infection was monitored by determination leukocyte count and blood sedimentation rate; blood samples were taken befor, 24 hours after surgery, and on days 3, 7, 10, 14. Wound healing was assessed on days 2, 3, 7, 10, and at the time of removal of sutures. Resorption of implanted beads and bone reconstruction were evaluated by X-ray at after operation and at approximately one, three and six months after implantation. A total of 20 patients (mean age 38,1 (26 to 53), 14 male, 6 female) were treated with Perossal pellets (AAP, Germany) from October 2013 to April 2015. Mean leukocyte counts and blood sedimentation rate were within the normal laboratory range and did not indicate infectious complications during the first 21 days after surgery. Primary wound healing occurred in 18 patients and secondary wound healing in two patients. There were two cases of re-infection during the course of the study, one of them related to an incomplete eradication of infected tissue and multidrug-resistant strain occurring during the course of the study, the other is occurred that patient non-compliance. Radiographic analysis six months after surgery showed progressive resorption of the implanted pellets, but only 10 cases have decreasing size of defects on X-ray. This study in adult patients with chronic post-traumatic/post-operative osteomyelitis demonstrated that these biodegradable bone filler pellets which can be loaded with different antibiotics are a clinically useful local antibiotic delivery system and bone substitute which can be used as an alternative to other anti-infective implants. The implantation of the pellets was safety and well tolerated in all patients. This composite can provide adequate protection against bacterial infection during the first weeks after implantation and to support the bone healing process

The most challenging complications in orthopaedic trauma surgery are fracture-related infections (FRI). The incidence ranges from approximately 1% after closed fractures or joint replacement, to more than 30% in complex open limb fractures. Despite tremendous efforts with prolonged antibiotic therapy and multiple revision surgeries, these complications are associated with considerable rates of recurrent infections as well as permanent functional impairment. The primary aim for the clinician is to prevent infection, because once established, an infection is difficult to eradicate. The main reason for this is biofilm formation on the implanted device, which allows pathogens to protect themselves from host immune response and antimicrobial therapy. In open fractures with a considerable wound contamination and soft- tissue damage, systemically-delivered antibiotics may not reach sufficient local concentrations to eradicate the bacteria. Locally delivered antibiotics can overcome this problem by providing high local concentrations. Currently, several antibiotic loaded biomaterials for local infection prophylaxis and/or treatment are available. In this talk, next to the diagnostic challenges of FRIs, the currently available antimicrobial-loaded biomaterials will be described. Against a backdrop of increasing infection and antimicrobial resistance, the prudent use and availability of such materials will become even more important

Introduction. Prosthetic joint infections (PJI) occur infrequently, but due to its increased clinical use represent the most devastating complication with high morbidity and substantial cost. Staphylococcus aureus and coagulase-negative staphylococci are the most common infecting agents associated with PJI. A possible therapeutic approach could be the local antibiotic by fluoride-TiO2 nanostructured anodic layers in order to prevent surface colonisation during the early moments after surgery. Here we describe the first results of this model using two common antibiotics. Methods. Fluoride-TiO2 nanostructured anodic layers on Ti6Al4V alloy were produced as described previously by Arenas et al (2013). Discs shaped pieces of Ti6Al4V alloy were loaded with a solution of 150 mg antibiotic (vancomycin or gentamicin)/20 ml sterile distilled water. Samples were immersed in this solution during 24 hours at room temperature with agitation, and then were dried during 48 hours at 20°C. Antibiotic release was studied by introducing both discs in sterile PBS and samples were taken at different times. Samples were then frozen at −80°C until HPLC measurements and biological activity tests using Bacillus subtilis ATCC 6051 (vancomycin) and Escherichia coli ATCC 25922 (gentamicin) were performed. Results. Release kinetic constant was not be obtained by HPLC-UV due to chemical degradation, therefore it was needed to prove biological activity. According to biological activity test, vancomycin and gentamicin estimated concentration mean and standard deviation were 2.9±0.61 and 2.71±0.64 mg/L over time respectively. Conclusions. Fluoride-TiO2 nanostructured anodic layers on Ti6Al4V alloy could be considered as promising vector of antibiotics for the prevention of PJI during early moments after surgery

Objectives. Thermal stability is a key property in determining the suitability of an antibiotic agent for local application in the treatment of orthopaedic infections. Despite the fact that long-term therapy is a stated goal of novel local delivery carriers, data describing thermal stability over a long period are scarce, and studies that avoid interference from specific carrier materials are absent from the orthopaedic literature. Methods. In this study, a total of 38 frequently used antibiotic agents were maintained at 37°C in saline solution, and degradation and antibacterial activity assessed over six weeks. The impact of an initial supplementary heat exposure mimicking exothermically curing bone cement was also tested as this material is commonly used as a local delivery vehicle. Antibiotic degradation was assessed by liquid chromatography coupled to mass spectrometry, or by immunoassays, as appropriate. Antibacterial activity over time was determined by the Kirby-Bauer disk diffusion assay. Results. The heat exposure mimicking curing bone cement had minimal effect on stability for most antibiotics, except for gentamicin which experienced approximately 25% degradation as measured by immunoassay. Beta-lactam antibiotics were found to degrade quite rapidly at 37°C regardless of whether there was an initial heat exposure. Excellent long-term stability was observed for aminoglycosides, glycopeptides, tetracyclines and quinolones under both conditions. Conclusions. This study provides a valuable dataset for orthopaedic surgeons considering local application of antibiotics, and for material scientists looking to develop next-generation controlled or extended-release antibiotic carriers. Cite this article: E. Samara, T. F. Moriarty, L. A. Decosterd, R. G. Richards, E. Gautier, P. Wahl. Antibiotic stability over six weeks in aqueous solution at body temperature with and without heat treatment that mimics the curing of bone cement. Bone Joint J 2017;6:296–306. DOI: 10.1302/2046-3758.65.BJR-2017-0276.R1

We investigated the antibiotic concentration in fresh-frozen femoral head allografts harvested from two groups of living donors. Ten samples were collected from patients with osteoarthritis of the hip and ten from those with a fracture of the neck of the femur scheduled for primary arthroplasty. Cefazolin (1 g) was administered as a pre-operative prophylactic antibiotic. After storage at −80°C for two weeks the pattern of release of cefazolin from morsellised femoral heads was evaluated by an in vitro broth elution assay using high-performance liquid chromatography. The bioactivity of the bone was further determined with an agar disc diffusion and standardised tube dilution bioassay. The results indicated that the fresh-frozen femoral heads contained cefazolin. The morsellised bone released cefazolin for up to four days. The concentration of cefazolin was significantly higher in the heads from patients with osteoarthritis of the hip than in those with a fracture. Also, in bioassays the bone showed inhibitory effects against bacteria. We concluded that allografts of morsellised bone from the femoral head harvested from patients undergoing arthroplasty of the hip contained cefazolin, which had been administered pre-operatively and they exhibited inhibitory effects against bacteria in vitro

There has been a significant increase in the demand of polymeric scaffolds with promising affects in bone regeneration. However, inflammation is still a problem in transplantations to overcome with local antibiotic therapy. In this study, it is aimed to develop a functional POSS nanocage reinforced chitosan scaffold (CS/POSS) coated with drug loaded chitosan composite nanospheres to provide a controlled antibianyiotic delivery at the defect site. Gentamicin and vancomycin were selected as model antibiotic drugs. Drug loaded nanospheres were fabricated with electrospray method and characterized in terms of morphology, hydrodynamic size, surface charge, FT-IR, in vitro drug release, antimicrobial activity and cytotoxicity. CS/POSS scaffolds were fabricated via lyophilisation and characterized with mechanic, swelling test, SEM and micro CT analyses. Positively charged nanospheres with uniform morphology were obtained. High drug encapsulation efficiency (80–95%) and sustained release profile up to 25 days were achieved with a cumulative release of 80–90%. In addition, the release media of the nanospheres (in 6 hours, 24 hours and 25 days of incubation period) showed a strong antimicrobial activity against S.aureus and E.coli, and did not show any cytotoxic effect to 3T3 and SaOS-2 cell lines. CS/POSS scaffolds were obtained with high porosity (89%) and 223.3±55.2μm average pore size. POSS reinforcement increased the compression modulus from 755.7 to 846.1Pa for 10 % POSS addition. In vitro studies of nanosphere coated bilayer scaffolds have showed high cell viability. Besides ALP activity results showed that POSS incorporation significantly increased the ALP activity of Saos-2 cells cultured on the scaffold. In conclusion, these composites can be considered as a potential candidate in view of its enhanced physico-chemical properties as well as biological activities for infection preventive bone tissue engineering applications

Recently in traumatology various methods of impregnation biodegradable implants and allografts with antibiotics are widely used. Among them the soaking, shaking and ionophores are common used. We aimed to choose the optimal method of impregnation with the antibiotic of the head of the femur, taken from patients after arthroplasty. We studied 6 femoral heads after hip replacement. Head №1 the iohexol (Omnipaque) was injected through circular ligament and through the neck of the femur. Head №2 through the circular ligament, head №3 through the neck of the femur, head №4 through the circular ligament and through the neck of the femur, head №5 through 4 pre-drilled channels a brilliant green solution was injected. The head №6 was soaked in a brilliant green solution. Head №1 assessed by radiology. All the heads, treated with brilliant green, were cut in half to assess the degree of impregnation. On the X-ray image of head №1 the contrast agent has spread enough. In osteotomy, the impregnation with brilliant green head №2, №3, №4, №5 was seen in 3–4 mm around the needle passage place. Head №6 the bone was not impregnated. Despite the fact that the radiograph showed a sufficient spread of contrast agent, on the sections of the head, treated with brilliant green, showed the spread of liquid 3–4 mm around the needle passage place. This indicates that the impregnation of large bone is not effective

Introduction:. Antimicrobial resistance is an important patient safety issue. Antibiotic Stewardship is one of the key strategies in tackling this problem. We present our data over a two year period from October 2011 to December 2013. Method:. A multidisciplinary, consultant led antibiotic ward round was implemented in October 2011. This involved the consultant orthopaedic surgeon, microbiologist, pharmacist and antibiotic prescription nurse. Data from the meetings was collected prospectively over a 118 week period using a standard data form. The case notes, prescription kardex, laboratory results including microbiology data and clinical information of patients was available at the time of the Ward round. The indications for, choice of antibiotics, duration and further treatment plan were made and a note for the case notes was dictated immediately. Changes to prescriptions were also made at the time. Results:. Over the first 2 years 269 patients were reviewed. We noticed a 22% decrease in the volume of IV antibiotic prescriptions. 35% of antibiotic prescriptions were de-escalated (reducing the dose or narrowing the spectrum), however 9% required escalation. 2% of prescriptions were stopped for being clinically not required any more. There was 48% decrease in costs of IV antibiotics and 30% decrease in total cost of oral and IV antimicrobials. Discussion:. We find that this exercise leads to a clear, documented, more cohesive approach to patients' treatment which improves patient care. It makes the orthopaedic consultant and on call team aware of all patients on antibiotics and the plan for the following week. Conclusion:. Antibiotic Stewardship in our hospital has led to the decrease in the use of antibiotics and reduced costs along with several other soft benefits in patient treatment. Given the rising problem of antibiotic resistance, this key pillar strategy against it should be implemented in all hospitals

The role of perioperative antibiotic prophylaxis in sarcoma surgery is well established. There are no guidelines for their use in this context but there is pressure from microbiologists to comply with agreed prophylaxis for joint arthroplasty despite major differences between patient groups and risks of infection in sarcoma surgery. Two simple surveys were conducted online, the first for bone sarcoma surgery, the second for soft tissue sarcomas. An email was sent to the major centres worldwide conducting such surgery with links to the online surveys to assess current practice regarding antibiotic prophylaxis and surgical drains. The survey was limited to 8 questions, the emphasis being a simple survey, but included questions on indications, choice, duration of therapy as well as use, size and duration of surgical drains. We received 38 responses from 15 countries to the bone sarcoma survey and 33 responses from 12 countries to the soft tissue sarcoma survey. Current antibiotic prophylaxis regimens varied widely among surgeons, emphasising the controversy that exists regarding what constitutes best clinical practice. Opinions regarding use of perioperative antibiotic prophylaxis in sarcoma surgery vary widely among orthopaedic surgeons worldwide, illustrating the controversy as to what constitutes best clinical practice. This survey suggests the need for a randomised clinical trial to aid in the development of guidelines in this area

Administration of perioperative antibiotic prophylaxis (AP) reduces the risk of prosthetic joint infection (PJI) following primary total hip (THA) and knee (TKA) arthroplasty. The optimal type of antibiotic used, and duration of prophylaxis are subject to debate. We compared the risk of revision surgery for PJI in the first year following THA and TKA by AP regimen. A national survey collecting information on hospital-level AP regimen policy was conducted across the Netherlands and linked to data from the LROI arthroplasty registry for 2011–2015. PJI status was defined using the surgical indication reported at revision by surgeons in the registry form. Restricted cubic splines Poisson model adjusted for hospital clustering were used to conduct the comparisons on 130,712 THAs and 111,467 TKAs performed across 99 institutions. These included 399 THAs and 303 TKAs revised for an indication of PJI. Multiple shot of Cefazolin (MCZ), of cefuroxime (MCX) and single shot of Cefazolin (SCZ) were respectively administrated to 87%, 4% and 9% of patients. For THA, the rates of revision for PJI were respectively 31/10,000 person-years 95%CI[28, 35], 39[25, 59] and 23[15, 34] in the groups which received MCZ, MCX and SCZ; respectively, the rates for TKA were 27[24, 31], 40[24, 62] and 24[16, 36]. No evidence of difference between AP regimens was found in the unadjusted and adjusted model (age, gender, BMI and ASA grade). Further work is advocated to confirm whether there is an association between AP regimen collected at patient-level and the risk of subsequent revision for PJI

Infection of orthopaedic implants is a significant problem, with increased antibiotic resistance of adherent ‘biofilm’ bacteria causing difficulties in treatment. We have investigated the in vitro effect of a pulsed electromagnetic field (PEMF) on the efficacy of antibiotics in the treatment of infection of implants. Five-day biofilms of Staphylococcus epidermidis were grown on the tips of stainless-steel pegs. They were exposed for 12 hours to varying concentrations of gentamicin or vancomycin in microtitre trays at 37°C and 5% CO. 2. The test group were exposed to a PEMF. The control tray was not exposed to a PEMF. After exposure to antibiotic the pegs were incubated overnight, before standard plating onto blood agar for colony counting. Exposure to a PEMF increased the effectiveness of gentamicin against the five-day biofilms of Staphylococcus epidermidis. In three of five experiments there was reduction of at least 50% in the minimum biofilm inhibitory concentration. In a fourth experiment there was a two-log difference in colony count at 160 mg/l of gentamicin. Analysis of variance (ANOVA) confirmed an effect by a PEMF on the efficacy of gentamicin which was significant at p < 0.05. There was no significant effect with vancomycin

Introduction. Open fractures occur with an annual incidence of 11.5 per 100,000 (6900 pa in UK). Infection rates, even with intravenous broad-spectrum antibiotics, remain as high as 22%. For this reason necessary bone grafting is usually delayed until soft-tissue cover of the bone injury is achieved. A biodegradable bone graft that released sustained high concentrations of antibiotics and encouraged osteogenesis, that could be implanted safely on the day of injury would reduce infection rates and avoid reoperation and secondary grafting. The non –union rate (approx 350 pa in UK) should also be reduced. Such a graft, consisting of a PLA/PGA co –polymer and containing antibiotics, is under development and here we report assessment of spectrum and duration of antimicrobial activity and effect of addition of antibiotics on mechanical properties. Methods. Varying concentrations of gentamicin, colistin, clindamycin and trimethoprim, singly and in combination, were added to the copolymer and test pieces were made. These were then tested using an established method (SPTT) which determines degree and duration of antimicrobial activity as well as risk of emerging resistance. Test bacteria were Staphylococcus epidermidis, Staphylococcus aureus, MRSA and Escherichia coli. Mechanical properties (compressive strength and porosity) were determined using established methods. Results. A combination of gentamicin (4%w/w) and clindamycin (2.5% w/w) gave best results, with inhibitory activity persisting for over 21 days (the target duration) without emergence of resistance. No significant effect of this combination/concentration on mechanical properties was found. Conclusions. The experimental PLA/PGA scaffold containing antibiotics showed activity against the common pathogens of open fractures for a period considered long enough to eradicate contamination acquired at or soon after trauma. At the optimum concentration, they had no significant effect on mechanical properties. In vivo performance is currently being investigated in a sheep model

Objectives. The objective of this study was to determine if combining variations in mixing technique of antibiotic-impregnated polymethylmethacrylate (PMMA) cement with low frequency ultrasound (LFUS) improves antibiotic elution during the initial high phase (Phase I) and subsequent low phase (Phase II) while not diminishing mechanical strength. Methods. Three batches of vancomycin-loaded PMMA were prepared with different mixing techniques: a standard technique; a delayed technique; and a control without antibiotic. Daily elution samples were analysed using flow injection analysis (FIA). Beginning in Phase II, samples from each mix group were selected randomly to undergo either five, 15, 45, or 0 minutes of LFUS treatment. Elution amounts between LFUS treatments were analysed. Following Phase II, compression testing was done to quantify strength. A-priorit-tests and univariate ANOVAs were used to compare elution and mechanical test results between the two mix groups and the control group. Results. The delayed technique showed a significant increase in elution on day one compared with the standard mix technique (p < 0.001). The transition point from Phase I to Phase II occurred on day ten. LFUS treatments significantly increased elution amounts for all groups above control. Delayed technique resulted in significantly higher elution amounts for the five-minute- (p = 0.004) and 45-minute- (p < 0.001) duration groups compared with standard technique. Additionally, the correlations between LFUS duration and total elution amount for both mix techniques were significant (p = 0.03). Both antibiotic-impregnated groups exhibited a significant decrease in offset yield stress compared with the control group (p < 0.001), however, their lower 95% confidence intervals were all above the 70 MPa limit defined by International Standards Organization (ISO) 5833-2 reference standard for acrylic bone cement. Conclusion. The combination of a delayed mix technique with LFUS treatments provides a reasonable means for increasing both short- and long-term antibiotic elution without affecting mechanical strength. Cite this article: Dr. T. McIff. Combination of modified mixing technique and low frequency ultrasound to control the elution profile of vancomycin-loaded acrylic bone cement. Bone Joint Res 2016;5:26–32. doi: 10.1302/2046-3758.52.2000412

Fracture related infection remains a major challenge in musculoskeletal trauma surgery. Despite best practice, treatment strategies suffer from high failure rates due to antibiotic resistance and tolerance. Bacteriophages represent a promising alternative as they retain activity against such bacteria. However, optimal phage administration protocols remain unknown, although injectable hydrogels, loaded with phage and conventional antibiotics, may support conventional therapy. In this study we tested the activity of meropenem, and two newly isolated bacteriophages (ϕ9 and ϕ3) embedded within alginate-chitosan microbeads and a hydrogel. Antibiotic and phage stability and activity were monitored in vitro, over a period of 10 days. In vivo, the same material was tested in treatment of a 5-day old Pseudomonas aeruginosa infection of a tibial plate osteotomy in mice. Treatment involved debridement and 5 days of systemic antibiotic therapy plus: i- saline, ii-phages in saline, iii-phages and antibiotics loaded into a hydrogel (n=7 mice/group). To assess the efficacy of the treatments, the infection load was monitored during revision surgery with debridement of the infected tissue after 5,10 and 13 days (euthanasia) by CFU and PFU quantification. In vitro testing confirmed that the stability of meropenem and activity of ϕ9 and ϕ3, was not affected within the alginate beads or hydrogel over 10 days. The in vivo study showed that all mice receiving phages and antibiotics loaded into a hydrogel survived the infection with a reduction of the bacterial load in the soft tissue. Active phages could be recovered from the infected site at euthanasia (10. 4. PFU/g). The hydrogel loaded with bacteriophages and meropenem showed a positive result in locally reducing the infection load indicating a synergistic effect of the selected antimicrobials. Overall, our new strategy shows encouraging results for improving the treatment of antibiotic-resistant biofilm infections that are related to medical implants