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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_17 | Pages 79 - 79
24 Nov 2023
Puetzler J Vallejo A Gosheger G Schulze M Arens D Zeiter S Siverino C Moriarty F
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Aim

The time to onset of symptoms after fracture fixation is still commonly used to classify fracture-related infections (FRI). Early infections (<2 weeks) can often be treated with debridement, systemic antibiotics, irrigation, and implant preservation (DAIR). Late infections (>10 weeks) typically require implant removal as mature, antibiotic-tolerant biofilms have formed. However, the recommendations for delayed infections (2–10 weeks) are not clearly defined. Here, infection healing and bone healing in early and delayed FRI is investigated in a rabbit model with a standardized DAIR procedure.

Method

Staphylococcus aureus was inoculated into 17 rabbits after plate osteosynthesis in a humerus osteotomy. The infection developed either one week (early group, n=6) or four weeks (delayed group, n=6) before a standardized DAIR procedure and microbiological analysis were performed. Systemic antibiotics were administered for six weeks (two weeks: Nafcillin+Rifampin, four weeks: Levofloxacin+Rifampin). A control group (n=5) also underwent a revision operation (debridement and irrigation) after four weeks, but received no antibiotic treatment. Rabbits were euthanized seven weeks after the revision operation. Bone healing was assessed using a modified radiographic union score for tibial fractures (mRUST). After euthanasia, a quantitative microbiological examination of the entire humerus, adjacent soft tissues, and implants was performed.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_14 | Pages 78 - 78
1 Dec 2019
Pützler J Alexander M Everding J Raschke MJ Arens D Zeiter S Richards GR Moriarty FT
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Aim

Focused high energy extracorporeal shockwave therapy (fhESWT) is used to support fracture healing in non-union cases and has been shown to have antibacterial effects. We trialed fhESWT as an adjunct to conventional treatment in a clinically relevant rabbit model of fracture related infection.

Method

A complete humeral osteotomy was performed in 31 rabbits and fixed with a 7-hole-LCP. A fracture-related infection (FRI) was established with Staphylococcus aureus. After two weeks, a revision surgery was performed with debridement, irrigation and implant retention. Rabbits then received: no further treatment (controls); shockwaves (at day 2 and 6 after revision, 4'000 Impulses each time with 23kV); systemic antibiotics (rifampin and nafcillin) over one week in weight adjusted dosages; or the combination of antibiotics and shockwaves. Treatments were applied over one week. Blood cultures were taken before and after shockwave sessions. After an additional week without treatment, rabbits were euthanized, and quantitative bacteriology was performed on implants and tissues to determine infection burden. Indicator organs (brain, heart, liver, lungs, kidneys and spleen) were cultured to assess possible bacteraemia due to fhESWT.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_14 | Pages 87 - 87
1 Dec 2019
Burch MA Thompson K Eberli U Arens D Milstrey A Stadelmann V Richards G Moriarty F
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Aim

Non-steroidal anti-inflammatory drugs (NSAIDs) are a cornerstone of perioperative pain management in orthopedic trauma surgery, although concerns persist regarding the potential impact of these drugs on fracture healing. Furthermore, NSAIDs may also exert an influence on host immune defenses, which may also be important in the context of infection treatment. However, this has been very much under-investigated in the clinical and scientific literature. The aim of this study was to determine the impact of NSAIDs on the course of an orthopedic device-related infection (ODRI) and its response to antibiotic therapy in a rat model.

Method

A polyetheretherketone (PEEK) screw was inserted in the proximal tibia of 48 skeletally mature female Wistar rats: 12 control animals received a sterile screw, of which 6 also received NSAID therapy (carprofen, 5 mg/kg s.c. once daily); 36 rats received a Staphylococcus epidermidis-inoculated screw, of which 18 received NSAID therapy. Antibiotic therapy was administered from day 7–21 in 9 animals from all groups receiving S. epidermidis-inoculated screws (cefazolin: 30 mg/kg; s.c., b.i.d. plus rifampin: 25 mg/kg; s.c., b.i.d.). Bone histomorphometric changes were monitored using longitudinal microCT scanning, performed postoperatively, and at 3, 6, 9, 14, 20 and 28 days (euthanasia). Quantitative bacteriology of the implant, bone and overlying soft tissue was performed to assess infection status of individual animals.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_14 | Pages 79 - 79
1 Dec 2019
Arens D Zeiter S Paulin T Ranjan N Alt V
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Aim

Silver is known for its excellent antimicrobial activity, including activity against multiresistant strains. The aim of the current study was to analyze the biocompatibility and potential influence on the fracture healing process a silver-coating technology for locking plates compared to silver-free locking plates in a rabbit model.

Methods

The implants used in this study were 7-hole titanium locking plates, and plasma electrolytic oxidation (PEO) silver coated equivalents. A total of 24 rabbits were used in this study (12 coated, 12 non-coated). An osteotomy of the midshaft of the humerus was created with an oscillating saw and the humerus stabilized with the 7 hole locking plates with a total of 6 screws. X-rays were taken on day 0, week 2, 4, 6, 8, and 10 for continuous radiographical evaluation of the fracture healing. All animals were euthanized after 10 weeks and further assessment was performed using X-rays, micro-CT, non-destructive four-point bending biomechanical testing and histology. Furthermore, silver concentration was measured in the kidney, liver, spleen and brain.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_22 | Pages 63 - 63
1 Dec 2017
Pützler J Arens D Metsemakers W Zeiter S Richard K Richards G Raschke M Moriarty F
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Aim

Open fractures still have a high risk for fracture-related Infection (FRI). The optimal duration of perioperative antibiotic prophylaxis (PAP) for open fractures remains controversial due to heterogeneous guidelines and highly variable prophylactic regimens in clinical practice. In order to provide further evidence with which to support the selection of antibiotic duration for open fracture care, we performed a preclinical evaluation in a contaminated rabbit fracture model.

Method

A complete humeral osteotomy in 18 rabbits was fixed with a 7-hole-LCP and inoculated with Staphylococcus aureus (2×106 colony forming units, CFU per inoculum). This inoculum was previously shown to result in a 100% infection rate in the absence of any antibiotic prophylaxis. Cefuroxime was administered intravenously in a weight adjusted dosage equivalent to human medicine (18.75 mg/kg) as a single shot only, for 24 hours (every 8 hours) and for 72 hours (every 8 hours) in separate groups of rabbits (n=6 per group). Infection rate per group was assessed after two weeks by quantitative bacteriological evaluation of soft tissue, bone and implants. Blood samples were taken from rabbits preoperatively and on days 3, 7 and 14 after surgery to measure white blood cell count (WBC) and C-reactive protein (CRP) levels.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_22 | Pages 7 - 7
1 Dec 2017
Vallejo A Morgenstern M Puetzler J Arens D Moriarty T Richards G
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Aim

Antibiotic prophylaxis is critical for the prevention of fracture related infection (FRI) in trauma patients, particularly those with open wounds. Administration of prophylactic antibiotics prior to arrival at the hospital (e.g. by paramedics) may reduce intraoperative bacterial load and has been recommended; however scientific evidence for pre-hospital administration is scarce.

Methods

The contaminated rabbit humeral osteotomy model of Arens was modified to resemble the sequence of events in open fractures. In an initial surgery representing the “accident”, a 2mm mid-diaphyseal hole was created in the humerus and the wound was contaminated with a clinical Staphylococcus aureus strain (mean 1.6×106 Colony Forming Units, CFU). The animals were allowed recover for 4 hours mimicking the period from trauma to debridement. At this time, a second procedure was performed in order to debride and irrigate the wound, and to fix a complete osteotomy that was made through the initial defect. Three test groups were included (n=8 rabbits per group): 1) no antibiotic therapy; 2) standard “in-hospital” antibiotic prophylaxis (24 hours therapy starting 30 minutes before surgery); 3) “pre-hospital” antibiotics (single dose 15 minutes after the “accident”). The antibiotic used was cefuroxime and was administered in a weight-adjusted dosage.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_23 | Pages 31 - 31
1 Dec 2016
Metsemakers W Schmid T Zeiter S Ernst M Keller I Cosmelli N Arens D Moriarty F Richards G
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Aim

The aim of this study was to define the role of implant material and surface topography on infection susceptibility in a preclinical in vivo model incorporating appropriate fracture biomechanics and bone healing.

Method

The implants included in this experimental study were composed of: standard Electro polished Stainless Steel (EPSS), standard titanium (Ti-S), roughened stainless steel (RSS) and surface polished titanium (Ti-P). In an in vivo study, a rabbit humeral fracture model was used. Each rabbit received one of three Staphylococcus aureus inocula, aimed at determining the infection rate at a low, medium and high dose of bacteria. Outcome measures were quantification of bacteria on the implant and in the surrounding tissues, and determination of the infectious dose 50 (ID50).