Aim. Periprosthetic joint infection (PJI) is a complication of total joint arthroplasty that typically requires revision surgery for treatment. Systemic antibiotics are usually held prior to surgery to improve yield of intraoperative cultures. However, recent studies suggest that preoperative aspirations have a high concordance with intraoperative cultures, which may allow surgeons to initiate antibiotic treatment earlier. The purpose of the study was to investigate the effect of Pre-surgical systemic antibiotic therapy on the bacterial burden within the periprosthetic space and systemic immune reaction. Method. PJI was induced with MSSA (Xen36) S. aureus in the right knee of 16-week old, female, C57BL6 mice using a previously validated murine model. Mice were randomized to three groups (n=8, each): control; Vanc, receiving systemic vancomycin (110mg/kg, SQ, twice daily); or VancRif receiving vancomycin same as in Vanc group, plus rifampin (12mg/kg dose, IV, once daily). Following 2 weeks of treatment, mice were euthanized and periprosthetic bone, soft tissue and the implant were harvested. Bacterial burden, colony forming units (CFUs), was quantified in soft tissue, tibial bone, and on the implant. Specifically, tissues were homogenized and serially plated for CFUs, while the implant was sonicated and then plated for CFUs. The host immune response was analysed through weighing inguinal and iliac lymph nodes and through measuring serum amyloid A (SAA). Non-parametric pairwise group comparisons of the three outcome measures were performed using a Mann-Whitney U test. Results. VancRif, the combined treatment significantly reduced bacterial burden in the periprosthetic soft tissue, bone, and implant compared to control (p<0.001) and Vanc alone (p<0.001). While not significant, Vanc alone did reduce bacterial load as compared to control. The ipsilateral weight of the iliac lymph nodes was significantly reduced in Vanc and VancRif mice compared to controls (p<0.001), was well as in VancRif versus Vanc alone (p<0.001). Interestingly, SAA levels did not significantly differ among all groups. During tissue harvesting, minimal purulence was observed in antibiotic treatment groups, unlike controls. Conclusions. Treating active PJI with vancomycin alone decreases periprosthetic bacterial loads and reduces the local immunological response. This effect is significantly enhanced with the combined rifampin use. These findings could suggest that when culture positive PJI is diagnosed, pre-surgical treatment with antibiotics may decrease immunosuppression and soft tissue infiltration, leading to a better chance of infection cure with subsequent surgical debridement. Histological investigations and repeat experiments involving subsequent surgical treatment are underway. Acknowledgements. Funding comes from internal institutional grants

Aim. In trauma surgery, the development of biomaterial-associated infections (BAI) is one of the most common complications affecting trauma patients, requiring prolonged hospitalization and the intensive use of antibiotics. Following the attachment of bacteria on the surface of the biomaterial, the biofilm-forming bacteria could initiate a chronic implant-related infection. Despite the use of conventional local and systemic antibiotic therapies, persistent biofilms involve various resistance mechanisms that contribute to therapeutic failures. The development of in vivo chronic BAI models to optimize antibiofilm treatments is a major challenge. Indeed, the biofilm pathogenicity and the host response need to be finely regulated, and compatible with the animal lifestyle. Previously, a Galleria mellonella larvae model for the formation of an early-stage biofilm on the surface of a Kirschner (K)-wire was established. In the present study, two models of mature biofilm using clinical Staphylococcus aureus strains were assessed: one related to contaminated K-wires (in vitro biofilm maturation) and the second to hematogenous infections (in vivo biofilm maturation). Rifampicin was used as a standard drug for antibiofilm treatment. Method. In the first model, biofilms were formed following an incubation period (up to 7 days) in the CDC Biofilm Reactor (CBR, BioSurface Technologies). Then, after implantation of the pre-incubated K-wire in the larvae, rifampicin (80 mg/kg) was injected and the survival of the larvae was monitored. In the second model, biofilm formation was achieved after an incubation period (up to 7 days) inside the larvae and then, after removing the K-wires from the host, in vitro rifampicin susceptibility assays were performed (according to EUCAST). Results. The first model indicate that in vitro biofilm maturation affects the bacterial pathogenicity in the host, depending on the S. aureus strain used. Furthermore, the more the biofilm is matured, the more the rifampicin treatment efficiency is compromised. The second model shows that, despite the fast in vivo biofilm formation in the host, the number of bacteria, either attached to the surface of the K-wire surface or in surrounding tissue of the larvae, was not increased over time. Conclusions. Altogether, these results allow the establishment of biofilm models using G. mellonella larvae in order to understand the impact of biofilm maturation on both the bacterial pathogenicity and the efficiency of antibiofilm treatments

Aims

It is well described that patients with bone and joint infections (BJIs) commonly experience significant functional impairment and disability. Published literature is lacking on the impact of BJIs on mental health. Therefore, the aim of this study was to assess health-related quality of life (HRQoL) and the impact on mental health in patients with BJIs.

Aims

The management of periprosthetic joint infection (PJI) remains a major challenge in orthopaedic surgery. In this study, we aimed to characterize the local bone microstructure and metabolism in a clinical cohort of patients with chronic PJI.

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

Local antimicrobial therapy is an integral aspect of treating orthopaedic device related infection (ODRI), which is conventionally administered via polymethylmethacrylate (PMMA) bone cement. PMMA, however, is limited by a suboptimal antibiotic release profile and a lack of biodegradability. In this study, we compare the efficacy of PMMA versus an antibioticloaded hydrogel in a single- stage revision for chronic methicillin-resistant Staphylococcus aureus (MRSA) ODRI in. sheep. Antibiofilm activity of the antibiotic combination (gentamicin and vancomycin) was determined in vitro. Swiss alpine sheep underwent a single-stage revision of a tibial intramedullary nail with MRSA infection. Local gentamicin and vancomycin therapy was delivered via hydrogel or PMMA (n = 5 per group), in conjunction with systemic antibiotic therapy. In vivo observations included: local antibiotic tissue concentration, renal and liver function tests, and quantitative microbiology on tissues and hardware post-mortem. There was a nonsignificant reduction in biofilm with an increasing antibiotic concentration in vitro (p = 0.12), confirming the antibiotic tolerance of the MRSA biofilm. In the in vivo study, four out of five sheep from each treatment group were culture negative. Antibiotic delivery via hydrogel resulted in 10–100 times greater local concentrations for the first 2–3 days compared with PMMA and were comparable thereafter. Systemic concentrations of gentamicin were minimal or undetectable in both groups, while renal and liver function tests were within normal limits. This study shows that a single-stage revision with hydrogel or PMMA is equally effective, although the hydrogel offers certain practical benefits over PMMA, which make it an attractive proposition for clinical use

Aim. The duration of systemic antibiotic therapy following first-stage surgery is contentious. Our Institution's philosophy is to perform an aggressive debridement, use high concentration targeted antibiotics through cement beads and systemic prophylactic antibiotics alone. In the presence of significant soft tissue infection or microbiological diagnostic uncertainty; systemic antibiotics may be prescribed for 5 days whilst awaiting tissue culture results. The aim of this study was to assess the success of our philosophy in the management of PJI of the hip using our two-stage protocol. Method. A retrospective review of our Institution's prospectively-collected database was performed to identify those patients who were planned to undergo a two-stage hip revision procedure for PJI. All patients had a confirmed diagnosis of PJI as per the major criteria of MSIS 2013, a minimum 5-years follow up and were assessed at the time of review using the MSIS working group outcome-reporting tool (2018). They were then grouped into “successful” or “unsuccessful” (suppressive antibiotics, further revision for infection, death within 1 year). Results. 299 intended two-stage hip revisions in 289 patients (6 repeat ipsilateral two-stage, 4 bilateral two-stage) met our inclusion criteria. 258 (86%) patients proceeded to 2. nd. stage surgery. Median follow up was 10.7 years. 91% success rate was observed for those patients who underwent reimplantation; dropping to 86% when including the patients who did not proceed to second stage surgery. The median duration of post-operative systemic antibiotics following first stage surgery was 5 days (IQR 5–9). No significant difference in outcome was observed in patients who received either; < / = 48 hours (86%; n=70) compared to > 48 hours antibiotics (86%; n=229; p=0.96) or </= 5 days of antibiotics (88%; n=202) compared to > 5 days antibiotics (82%; p=0.38). A significant majority had gram-positive (88%) infection with 30% being polymicrobial. Greater success rates were observed for gram-positive PJI (87%); than for gram-negative PJI (84%) and mixed Gram infection (72%; p=0.098). Conclusion. Aggressive surgical debridement with high concentration, targeted local antibiotic delivery at time of first stage hip surgery, without prolonged systemic antibiotics, provides a high rate of success, responsible antibiotic stewardship and reduced hospital costs

Introduction and Objective. Management of bone loss associated with bone contamination or infection represents a double biological and clinical challenge frequent in traumatology. The advent of new biomaterials can allow a different approach in the treatment of bone gap. The purpose of this study was to evaluate the prophylactic and therapeutic effectiveness of addition of a new absorbable bone substitute (BS) eluting different antibiotics in reconstruction of bone defects after infections and fractures with soft tissue damage. Materials and Methods. We conducted a review of patients with contaminated or infected bone defects treated using a new biomaterial, a porous composite of collagen matrices and Beta tricalcium phosphate (β TCP), able to provide a long-term release of different antibiotics. We have included treatment of osteomyelitis and osteosynthesis of exposed fracture (Gustilo Anderson 1–3b) or fractures with soft tissue damage and high risk of contamination. Surgical technique included debridement filling bone defect with BS eluting antibiotics, osteosynthesis (plate, nail, external fixator, kirschner wire), soft tissue coverage, and systemic antibiotic therapy. Radiographic and clinical data including complications (wound dehiscence, superficial or deep infection, osteomyelitis) were collected. Results. We treated 25 patients (21 male, 4 female) with mean age 47 yrs. (range 21–83). The locations treated (for incidence) was: 9 femurs (7 plates, 2 nail), 7 calcanei (one bilateral), 3 tibias, 2 forearms, 2 metatarsi, 2 hands, 1 elbow. 6 patients had large bone loss. 7 patients had bone infections (4 were Cierny Madern 4); 8 patients had osteosynthesis of exposed fractures Gustilo Anderson 1–3b (9 plate, one bilateral calcaneus). 8 patients had treatment for pseudoarthrosis of exposed fractures (6 femurs, 1 forearm, 1 metatarsus) and 3 patients a prophylactic treatment for calcaneal fractures with soft tissue damage. 4 deep infection were treated with multiple surgical debridement and new filling bone defect with BS eluting antibiotic with infection eradication. We have used a combination of vancomycin and gentamicin on 15 cases, vancomycin alone on 4 cases, combination of vancomycin and amikacin on 1 case and amikacin and Linezolid in a targeted multi drug resistance. At final follow-up functional outcome was good in all cases with bone healing. Conclusions. Extensive debridement is a fundamental requisite for eradication of bone infections and contamination. Filling of the bone void with loaded bio-composite eluting diversifiable local antibiotics with synergistic anti-biofilm activity is desirable. Treatment of this bone defects are advantaged when combining his reconstruction with BS and the possibility of release high antibiotic concentration at least for 10 days. This is an important complementing prophylactic and therapeutic antimicrobial option with adjuvant role to systemic therapy that enlarges the success rate

Aims

In the absence of an identified organism, single-stage revision is contraindicated in prosthetic joint infection (PJI). However, no studies have examined the use of intra-articular antibiotics in combination with single-stage revision in these cases. In this study, we present the results of single-stage revision using intra-articular antibiotic infusion for treating culture-negative (CN) PJI.

Aims

Biopsy of the periprosthetic tissue is an important diagnostic tool for prosthetic joint infection (PJI) as it enables the detection of the responsible microorganism with its sensitivity to antibiotics. We aimed to investigate how often the bacteria identified in the tissue analysis differed between samples obtained from preoperative biopsy and intraoperative revision surgery in cases of late PJI; and whether there was a therapeutic consequence.

Aim. Antibiotic loaded spacers are often used during a two-stage exchange for periprosthetic joint infections (PJI) both for its mechanical properties and as a means for local antibiotic delivery. The main goal of this study is to compare the rate of positive cultures during reimplantation with the use of different antibiotic loaded spacers: aminoglycoside only vs. combined glycopeptide/aminoglycoside vs. combined glycopeptide/carbapenem/aminoglycoside. Method. We retrospectively evaluated every two-stage exchange procedures for infected hip/knee arthroplasty between 2012–2018. Microbiological findings in the first and second stage were registered as well as the type of spacer and antibiotic(s) used. Cases in whom no cultures were obtained during reimplantation and cases without sufficient data on antibiotic(s) used in cement spacers were excluded. Results. Fifty-four cases were included (20THA and 34TKA), with an overall rate of positive cultures during reimplantation of 18.5% (10/54). The rate of positive cultures was statistically significant higher among spacers with monotherapy with aminoglycoside compared to spacers with combined antibiotic therapy- 35.7% (5/14) vs. 12.5% (5/40) respectively(p<0.05). Comparing those with combined glycopeptide/aminoglycoside (2/19) with triple glycopeptide/carbapenem/aminoglycoside therapy (3/21) there was no significant difference. Microorganisms present during the second stage were mostly staphylococci (coagulase-negative in four cases, S.aureus in three), Corynebacterium striatum, Enterococcus faecalis, C.albicans in one case each. In most cases (8/10), the isolated microorganism was the same as the first stage and was resistant to the antibiotic(s) used in the spacer in seven cases. Failure rate with the need for subsequent surgery was significantly higher at 60% (6/10) in cases with positive cultures at reimplantation compared to 4.5% (2/44) for those with negative cultures during reimplantation(p=0.0005). Conclusions. It has recently been suggested that adding a glycopeptide to the spacer may be advantageous when compared to spacers with aminoglycoside monotherapy, as it will produce significantly lower rates of positive cultures during reimplantation which have been shown to increase the risk of subsequent failure as is the case in our study. Local unavailability of obtaining powder aminoglycosides has driven us to manually add high doses of vancomycin and meropenem to commercially available low-dose gentamicin cement in many of our spacers and they seem to to perform just as well as commercially available vancomycin/gentamicin combination. Although many other variables not considered in this study may influence the rate of positive cultures during the second stage (quality of initial debridement, systemic antibiotic therapy, etc.), we believe these results portrait a sufficiently accurate picture of clinical results with the use of different spacers

Device-associated infection remains a serious clinical problem in orthopaedic and trauma surgery. The emergence of resistant organisms such as methicillin resistant Staphylococcus aureus (MRSA) has further exacerbated this problem by limiting the range of treatment options. Currently, systemic antibiotic therapy is the cornerstone of treatment, alongside surgical resection of infected tissues and implant removal. The potential for antibiotic loaded biomaterials to support the prevention and treatment of infection is significant, although the currently available options are limited in number and often re-purposed from other applications e.g. antibiotic loading of bone cement. The first part of the talk will cover the basic concepts involved in antibiotic treatment, with an emphasis on the ideal antibiotic release kinetics from biomaterials, and how bacterial biofilms and antibiotic resistance influence antimicrobial efficacy. The next generation of biomaterials for antibiotic delivery should be specifically designed with this knowledge in mind. Regulatory approval of antimicrobial combination devices, however, is an evolving process as regulatory bodies seek more robust and clinically relevant efficacy data. Approval will require preclinical efficacy using standardized animal models that recapitulate the key features of the clinical disease. The second part of this talk will cover best practice in this important stage of development

Objective

In the present study, we aimed to assess whether gelatin/β-tricalcium phosphate (β-TCP) composite porous scaffolds could be used as a local controlled release system for vancomycin. We also investigated the efficiency of the scaffolds in eliminating infections and repairing osteomyelitis defects in rabbits.

The management of periprosthetic joint infection is challenging and the duration of systemic antibiotic therapy whether it be during the interval phase or after reimplantation of a new prosthesis is controversial. We report our experience of managing chronic periprosthetic infection of the hip by the two stage exchange procedure. Patients who were scheduled to undergo a two stage revision for chronic periprosthetic infection of the hip were identified from our prospective database. Of 425 patients with microbiologically proven periprosthetic infection, 369 (87%) underwent a two stage procedure, leaving 56 patients who did not proceed to reimplantation. 41 of these were clinically infection free but for personal or medical reasons did not proceed. The remaining 15 had persistent infection. The mean age at the time of the first stage was 68 years (26 – 92 yrs). 256 (61%) patients were alive for review. The mean time between stages was 6.3 months with a mean follow up after the second stage was 65 months (range 5 to 276 months). The success rate of a single 1. st. stage debridement, confirmed by negative cultures at the time of second stage reimplantation was 94%. 19 patients underwent a repeat 1. st. stage debridement and were classed as failures of the 1. st. stage. At the time of final review, 340 (92%) patients were deemed infection free out of those who had completed a 2 stage exchange. The duration of systemic antibiotic treatment after both the 1. st. and 2. nd. stages was divided into <48 hrs and >48 hours. There was no significant difference in the success of the 1. st. stage procedure in patients who received < 48 hours (48% of the patients) as opposed to > 48 hours (p = 0.98, Chi Squared Test, Relative Risk 1.009). Similarly there was no difference in the overall success of the two stage procedure irrespective of the duration of antibiotic therapy with 76% of patients receiving <48hrs of antibiotics after the second stage. Aggressive surgical debridement together with targeted local and short term systemic antibiotic therapy should be the mainstay of treatment in two stage revision surgery

Aim. The treatment of osteomyelitis often requires extensive surgical debridement and removal of all infected tissues and foreign bodies. Resulting bone loss can then eventually be managed with antibacterial bone substitutes, that may also serve as a regenerative scaffold. Aim of the present study is to report the clinical results of a continuous series of patients, treated at our centre with an antibacterial bioglass*. Method. From November 2010 to May 2016, a total of 106 patients, affected by osteomyelitis, were included in this prospective, single centre, observational study. Inclusion criteria were the presence of osteomyelitis with a contained bone defect or segmental defects < 10 mm, with adequate soft tissue coverage. All patients underwent a one-stage procedure, including surgical debridement and bone void filling with the bioactive glass*, with systemic antibiotic therapy and no local antibiotics. Clinical, radiographic and laboratory examinations were performed at 3, 6 and 12 months and yearly thereafter. Results. Two patients were lost to follow-up, hence a total of 104 patients (65 males, 39 females; mean age: 46 ± 17 years, min 6 – max 81) were available at an average follow-up of 38 ± 26 months (range: 12 – 68); forty-eight patients (46.1%) were classified as Type A, 48 (46.1%) as Type B and 8 (7.7%) as Type C hosts, according to McPherson classification. Tibia (N=61) and femur (N=33) were the most common involved bones. On average patients had undergone 2.1 ± 1.3 (min 0 – max 7) previous surgical operations, with a mean infection duration of 18.7 ± 16.6 months (min 2 – max 120). Infection recurrence was observed in 10 patients (9.6%), most often within one year from surgery (8/10). Negative prognostic factors included infection duration > 2 years, Gram negative or mixed flora or negative cultural examination, Type B or C hosts and soft tissue defect. No side effects or complications related to bioglass were noted. Conclusions. This is to our knowledge the longest and the largest single centre consecutive series of patients, affected by bone infections of the long bones, treated according to a one-stage procedure using bioactive glass. Our results confirm, on a larger population and at a longer follow-up, previous reports. Early treatment, pathogen identification and adequate management of soft tissues should be considered to further reduce infection recurrence rate. *BonAlive®

Aim. Propionibacterium acnes (PA) is an important cause of shoulder prosthetic joint infections (SPJIs) for which the optimal treatment has not yet been determined. Rifampicin and Levofloxacin both showed not benefit in recent experimental models of PA-SPJIs. We describe herein the experience of five different medical French centers in order to assess factors associated with patient's outcome with special emphasize on antibiotic regimens. Method. A multicentric retrospective study was performed, on consecutive patients with PA – related SPJIs diagnosed on the basis of at least 2 or more positive cultures of either per-operative or joint aspiration and clinical history compatible with a PJI according to the current guidelines. All patients had surgical management, followed by systemic antibiotic therapy. Remission was defined as an asymptomatic patient with functioning prosthesis at the last contact. Results. Fifty-nine patients of mean age 66.2 ± 10.5 years were included. Most patients were at least ASA 2 (66%), 8 (14%) diabetes mellitus, 3 (5%) had neoplasia. Fourteen patients (24%) had acute, 34 (58%) subacute, and 11 late infections (19%). The mean delay from symptoms of infection to surgery was 89 ± 141 days (1–660). Surgical management consisted in implant exchange in 40 (68%) patients. Antibiotic treatment included mainly clindamycin (49%), levofloxacin (44%) and rifampin (17%), with a mean duration of 52.3 ± 31.9 days. The mean follow-up duration was 540 days ± 488 (range 12 ™ 1925). Forty-five patients were in remission (76%) in this study, 8 patients had a relapsing infection (14%), 1 a recurrence (2%) and 5 a superinfection ™ i.e, due to a different pathogen − (8%). In monovariate analysis, rifampicin/levofloxacin treatment was significantly associated with failure (p=0.038). In multivariate analysis, levofloxacin use and implants retention were significantly related to failure (p=0.02 and p=0.003, respectively). Conclusions. Our results suggest that implant retention and levofloxacin use are two independents factors of failure in patients treated for PA – related SPJIs

We describe a case series using calcium sulphate bio composite with antibiotics (Cerament/Stimulan) in treating infected metalwork in the lower limb. Eight patients aged 22–74 (7 males, 1 female) presented with clinical evidence of infected limb metal work from previous orthopaedic surgery. Metal work removal with application of either cerement in 5 cases (10–20ml including 175mg–350mg gentamycin) or stimulan in 3 cases (10–20ml including either 1g vancomycin or clindamycin 1.2g or 100mg tigecycline) into the site was performed. Supplemental systemic antibiotic therapy (oral/intravenous) was instituted based on intraoperative tissue culture and sensitivity. Four patients had infected ankle metalwork, 2 patients infected distal tibial metalwork and 2 had infected external fixators. Metal work was removed in all cases. The mean pre operative CRP was 15.8mg/l (range 1–56mg/l). The mean postoperative CRP at 1 month was 20.5mg/l (range 2–98mg/l). The mean pre op WCC was 7.9×10. 9. (range 4.7–10.5 ×10. 9. ). Mean post op WCC at 1 month was 7.1×10. 9. (range 5.0–9.2×10. 9. ). The organisms cultured included enterobacter, staphylococcus aureus, staphylococcus epidermidis, staphylococcus cohnii, stenotrophomonas, acinetobacter, group B streptococcus, enterococcus and escherichia coli. No additional procedures were required in any case. All surgical wounds went on to heal uneventfully. Infection control and union was achieved both clinically and radiologically in all cases. Our results support the use of a calcium sulphate bio composite with antibiotic as an adjuvant for effective local infection control in cases with implant related bone sepsis. The technique is well tolerated with no systemic or local side effects. We believe that implant removal, debridement and local antibiotic delivery can minimise the need for prolonged systemic antibiotic therapy in such cases

To prevent infections after orthopedic surgery, intravenous antibiotics are administered perioperatively. Cefazolin is widely used as the prophylactic antibiotic of choice. Systemic antibiotic therapy may however be less effective in longstanding surgery where bone allografts are used. Bone chips have been shown to be an effective carrier for certain types of antibiotics. Bone allografts impregnated with antibiotics may therefore provide the necessary local antibiotic levels for prophylaxis. To be efficient, a prolonged release from these bonechips is required. In contrast to vancomycin, for which prolonged release has clearly been proven effective from Osteomycin®, a commercially available impregnated bone allograft, no prolonged release bone chip preparations have been described so far for cefazolin. We developed a protocol to bind cefazolin in the porous structure of bone chips by means of a hydrogel composed of proteins naturally present in the human body. Three types of bone chips were evaluated: fresh frozen, decellularized frozen and decellularized lyophilized. Bone chips were incubated with 20 mg/ml cefazolin or treated with liquid hydrogel containing either 1 mg/ml fibrin or 1 mg/ml collagen and 20 mg/ml cefazolin. The cefazolin hydrogel was distributed in the porous structure by short vacuum treatment. Bone chips with cefazolin but without hydrogel were either incubated for 20 min- 4h or also treated with vacuum. Cefazolin elution of bone chips was carried out in fetal bovine serum and analyzed by Ultra Performance Liquid Chromatography – Diode Array Detection. Soaking of bone chips without hydrogel resulted in a quick release of cefazolin, which was limited to 4 hours. When vacuum was applied elution of >1 µg/ml cefazolin was measured for up to 36 hours. Combination with collagen hydrogel resulted in a higher cefazolin concentration released at 24 hours (3.9 vs 0.3 µg/ml), but not in a prolonged release. However, combination of decellularized frozen bone chips with fibrin hydrogel resulted in an initial release of 533 µg/ml followed by a gradual decline reaching the minimal inhibitory concentration for S. aureus at 72 hours (1.7 µg/ml), while not measurable anymore after 92 hours. Processed bone chips with hydrogel-cefazolin showed a markedly prolonged cefazolin release. When combined with a fibrin hydrogel, high initial peak levels of cefazolin were obtained, followed by a decreasing release over the following three days. This elution profile is desirable, since high initial levels are important to maximize anti-bacterial action whereas low levels of antibiotic for a limited time may stimulate osteogenesis. It is important that antibiotic release is ending after a few days as prolonged low levels of antibiotics are not clinically helpful and may lead to antibiotic resistance. Further preclinical studies are warranted to show effectiveness of hydrogel-cefazolin impregnated bone chips