Gentamicin and vancomycin do not impair experimental fracture healing

Does Topical Vancomycin Powder Use in Fracture Surgery Change Bacteriology and Antibiotic Susceptibilities? An Analysis of the VANCO Trial

OBJECTIVE

To determine whether intrawound vancomycin changes the bacteriology of surgical site infection pathogens and investigate the emergence of antibiotic-resistant pathogens.

METHODS

DESIGN

Secondary analysis of phase III, prospective, randomized clinical trial.

SETTING

Thirty-six US trauma centers.

PATIENT SELECTION CRITERIA

Patients who became infected after fixation of tibial plateau or pilon fracture.

OUTCOME MEASURES AND COMPARISONS

Pathogen types and bacterial susceptibilities as determined from routine clinical culture in the operating room.

RESULTS

Seventy-four patients were studied who were 67.5% male with a mean age of 48.6 years. A lower proportion of gram-positive cocci was observed in the vancomycin powder compared with the standard-of-care group (3.7% vs. 8.0%, P = 0.01). Methicillin-resistant Staphylococcus aureus infection incidence was comparable in both the vancomycin powder and the standard-of-care groups, but rates of methicillin-susceptible S. aureus infections were lower in the treatment group (1.4% vs. 4.8%, P = 0.01). The incidence of coagulase-negative Staphylococci and gram-negative rod infections were similar in both groups. There was no significant difference in susceptibilities between groups in rates of vancomycin-resistant enterococcus.

CONCLUSIONS

Topical vancomycin powder decreases the likelihood of gram-positive infections consistent with the biologic activity of vancomycin. Fewer methicillin-susceptible S. aureus and coagulase-negative Staphylococci infections were observed in the group treated with vancomycin powder. An effect of vancomycin powder on methicillin-resistant S. aureus infection risk was not detected given the low incidence in both the intrawound vancomycin and the standard-of-care groups. There was no emergence of gram-negative rod infections or increased resistance patterns observed. Use of topical vancomycin powder does not seem to produce infections in these patients with greater antibiotic resistance than would have occurred without its use.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

3D additive manufactured composite scaffolds with antibiotic-loaded lamellar fillers for bone infection prevention and tissue regeneration

Bone infections following open bone fracture or implant surgery remain a challenge in the orthopedics field. In order to avoid high doses of systemic drug administration, optimized local antibiotic release from scaffolds is required. 3D additive manufactured (AM) scaffolds made with biodegradable polymers are ideal to support bone healing in non-union scenarios and can be given antimicrobial properties by the incorporation of antibiotics. In this study, ciprofloxacin and gentamicin intercalated in the interlamellar spaces of magnesium aluminum layered double hydroxides (MgAl) and α-zirconium phosphates (ZrP), respectively, are dispersed within a thermoplastic polymer by melt compounding and subsequently processed via high temperature melt extrusion AM (~190 °C) into 3D scaffolds. The inorganic fillers enable a sustained antibiotics release through the polymer matrix, controlled by antibiotics counterions exchange or pH conditions. Importantly, both antibiotics retain their functionality after the manufacturing process at high temperatures, as verified by their activity against both Gram + and Gram - bacterial strains. Moreover, scaffolds loaded with filler-antibiotic do not impair human mesenchymal stromal cells osteogenic differentiation, allowing matrix mineralization and the expression of relevant osteogenic markers. Overall, these results suggest the possibility of fabricating dual functionality 3D scaffolds via high temperature melt extrusion for bone regeneration and infection prevention.

Study of antibiotic efficacy of topical vancomycin powder in treatment of infected mandibular fractures and soft tissue surgical site infections

Aims and Objective

To study the antibiotic efficacy of topical vancomycin in infected mandibular fracture treatment and its effect in preventing surgical site infections.

Materials and Methods

The study comprised of 100 subjects of infected mandibular fractures requiring open reduction and internal fixation, randomly categorized into two equal groups of 50 each, that is, vancomycin group (N = 50) treated for infected mandibular fractures with topical vancomycin powder used as adjunct and non-vancomycin group (N = 50). Clinical parameters like hospital stay, postoperative infections, postoperative fever, abnormal swelling, purulent discharge, and fistula formation at surgical site and radiographic healing was evaluated and compared between the groups.

Results

Mean age of vancomycin group and non-vancomycin group was 32.5 and 33.2 years, respectively. Demographic factors of the patients like age, sex, and hospital stay (3 ± 0.5 days) did not show significant difference between two groups. Vancomycin group shows 1 hyperthermia, 2 abnormal swelling and discharge, whereas non-vancomycin group shows 6 hyperthermia, 5 postoperative abnormal swelling and discharge with statistically significant (P < 0.05). Culture sensitivity of discharged fluid shows staphylococcal + MRSA infection in two patients in vancomycin group and eight patients in non-vancomycin group. Bony healing in vancomycin group shows one patient had non-union and one had graft rejection, whereas five patients had non-union and graft rejection in non- vancomycin group. The comparative results were statistically significant (P < 0.05).

Conclusion

From the result of our study we can conclude that routine use of vancomycin powder in surgical site as a surgical adjunct reduces the incidence of infections at surgical site when it is applied in addition to standard antibiotic prophylaxis. Topical application into a surgical wound also reduces the risk associated with parenteral administration of vancomycin.

Vancomycin powder for the prevention of surgical site infection in posterior elective spinal surgery

OBJECTIVE

To assess the effectiveness and safety of vancomycin powder as surgical site infection (SSI) prophylaxis in posterior bilateral elective spinal surgery.

MATERIALS AND METHODS

Single-center quasi-experimental pre and postintervention comparative cohort study. The post-intervention group received standard intravenous antibiotic prophylaxis plus 1g of vancomycin powder into the surgical field before wound closure, and the pre-intervention group only the intravenous prophylaxis.

RESULTS

150 patients were included in each group. Twelve SSI (7 superficial and 5 deep) occurred in the post-intervention group and 16 SSI (7 superficial and 9 deep) in the pre-intervention group. The risk of deep SSI decreased from 6.0% to 3.3% (OR 0,54, 95%CI 0.17-1.65, p=0.411) with vancomycin powder. The percentage of deep SSI due to gram negative-positive germs were 80%-20% and 33%-67% for the post- and pre-intervention groups, respectively (p=0.265). No local or systemic adverse effects occurred attributable to vancomycin powder.

CONCLUSION

In posterior elective spinal surgery, prophylaxis with vancomycin powder did not result in a significantly reduced incidence of superficial and deep SSI. There was a trend towards a higher incidence of deep SSI caused by gram negative microorganisms among those treated with vancomycin.

Local Intra-wound Administration of Powdered Antibiotics in Orthopaedic Surgery

Surgical site infection (SSI) is one of the most common complications after orthopaedic surgery, leading to significant morbidity and its associated costs. Surgical guidelines strongly recommend the use of systemic antibiotic prophylaxis to reduce the risk for developing SSI. Locally administered powdered antibiotics have the potential to provide remarkably high intra-wound concentrations without risk for systemic toxicity. However, a paucity of high quality evidence in the orthopaedic literature has prevented widespread adoption of this technique. The majority of clinical studies on local intra-wound antibiotics have evaluated the use of topical powdered vancomycin in spinal surgery, though only a single prospective study currently exists. This review will discuss all the available evidence describing the effectiveness, pharmacokinetics, and potential adverse effects with the use of topical powdered antibiotics in orthopedic surgery.

Effect of cefazolin and cefuroxime on fracture healing in rats

OBJECTIVE

To determine the effect of cefazolin and cefuroxime (the two most commonly used beta lactam antibiotics) at therapeutic doses in fracture healing in an animal model.

MATERIAL AND METHODS

75 adult male wistar rats (3months old) were selected. They were divided into three groups of 25 animals each (placebo, cefazolin and cefuroxime). A closed fracture was made in the middle third of the right femur of each rat and fixed with a Kirschner wire. Each group was treated with either saline (placebo), cefazolin or cefuroxime at therapeutic doses during fracture healing. Four weeks after fracture rats were killed and femora analysed through mechanical and histological testing.

RESULTS

The group treated with cefuroxime showed a lower mechanical resistance of the healing callus and a lower histological grade than placebo. The group treated with cefazoline showed a similar mechanical resistance and histological grade of callus to placebo.

CONCLUSION

Cefuroxime appear to disturb fracture healing more than cefazolin or placebo in Wistar rats. If those results are similar to human, the use of cefuroxime during fracture healing should be avoided in the clinical setting, if possible.

Intrasite vancomycin powder for the prevention of surgical site infection in spine surgery: a systematic literature review

BACKGROUND CONTEXT

Deep surgical site infections (SSIs) following spinal surgery are a significant burden to the patient, patient's family, and the health-care system. Because of increasing pressures to reduce SSIs and control costs, some spine surgeons have begun placing lyophilized vancomycin powder directly into the surgical wound at the conclusion of the procedure. However, the literature supporting this practice remains limited.

PURPOSE

To review the current literature examining the use of prophylactic intrasite vancomycin powder to control SSIs in spinal surgery and determine if any standard recommendations can be made.

STUDY DESIGN

A systematic review.

METHODS

Ovid Medline and PubMed were searched to identify English language articles.

RESULTS

No current guidelines are available for the use of intrasite vancomycin powder in preventing SSIs, and no standard dosage for the drug exists. Based on the limited literature and evidence currently available, there appears to be a protective effect of intrasite vancomycin powder on the incidence of SSI, without evidence of side effects. However, case reports do exist describing the systemic side effects after intrasite vancomycin powder during spine surgery.

CONCLUSIONS

The interpretation of the available evidence supporting the use of intrasite vancomycin powder in surgical wounds is limited, and its extrapolation should be performed with caution. Despite the lack of significant high-quality evidence available in the literature, many surgeons have adopted this practice; anecdotally, it continues to provide protection from infection without apparent significant risk of side effects.

Antimicrobial delivery systems for local infection prophylaxis in orthopedic- and trauma surgery

Infectious complications occur in a minor but significant portion of the patients undergoing joint replacement surgery or fracture fixation, particularly those with severe open fractures, those undergoing revision arthroplasty or those at elevated risk because of poor health status. Once established, infections are difficult to eradicate, especially in the case of bacterial biofilm formation on implanted hardware. Local antibiotic carriers offer the prospect of controlled delivery of antibiotics directly in target tissues and implant, without inducing toxicity in non-target organs. Polymeric carriers have been developed to optimize the release and targeting of antibiotics. Passive polymeric carriers release antibiotics by diffusion and/or upon degradation, while active polymeric carriers release their antibiotics upon stimuli provided by bacterial pathogens. Additionally, some polymeric carriers gelate in-situ in response to physiological stimuli to form a depot for antibiotic release. As antibiotic resistance has become a major issue, also other anti-infectives such as silver and antimicrobial peptides have been incorporated in research. Currently, several antibiotic loaded biomaterials for local infection prophylaxis are available for use in the clinic. Here we review their advantages and limitations and provide an overview of new materials emerging that may overcome these limitations.

Tissue engineering scaffold for sequential release of vancomycin and rhBMP2 to treat bone infections

The ability of silica calcium phosphate nanocomposite (SCPC75) for the controlled sequential delivery of vancomycin (Vanc) and rhBMP2 was evaluated. Fourier transform infrared spectroscopy analyses of the SCPC75 showed an increase in the bond energy of the PO4 (-3) due to the interactions with negatively charged moieties of Vanc. Furthermore, a decrease in the bond energy of the Si-O-Si functional groups was observed after rhBMP2 adsorption. In conjunction with the differences in bond site and bond energy at the ceramic/drug interface, significant differences in drug release kinetics and bioceramic dissolution rate were found. UV-vis spectrometry showed a burst release of Vanc in the first 8 h followed by a sustained release stage for up to 28 days. ELISA showed first-order release kinetics of rhBMP2 without burst release. The rhBMP2 release from SCPC75 was associated with a significantly lower rate of Ca and a higher rate of Si dissolutions when compared with Vanc release over identical time periods. Differences in the release kinetic profiles of Vanc and rhBMP2 from the SCPC75-Vanc/SCPC75-rhBMP2 scaffolds at 70/30, 50/50, or 20/80 ratios allowed for sequential drug release profiles that could be exploited to customize doses and release duration of each drug. The released rhBMP2 significantly upregulated MC3T3-E1 expression of collagen type I, osteopontin, and osteocalcin mRNA by 12.6-, 3.3-, and 2.4-fold, respectively. The released Vanc demonstrated bactericidal effects on Staphylococcus aureus in vitro. These results suggest the potential of SCPC75-Vanc-rhBMP2 scaffolds in the treatment of damaged and/or infected bone.

A novel injectable borate bioactive glass cement as an antibiotic delivery vehicle for treating osteomyelitis

Background

A novel injectable cement composed of chitosan-bonded borate bioactive glass (BG) particles was evaluated as a carrier for local delivery of vancomycin in the treatment of osteomyelitis in a rabbit tibial model.

Materials and Methods

The setting time, injectability, and compressive strength of the borate BG cement, and the release profile of vancomycin from the cement were measured in vitro. The capacity of the vancomycin-loaded BG cement to eradicate methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis in rabbit tibiae in vivo was evaluated and compared with that for a vancomycin-loaded calcium sulfate (CS) cement and for intravenous injection of vancomycin.

Results

The BG cement had an injectability of >90% during the first 3 minutes after mixing, hardened within 30 minutes and, after hardening, had a compressive strength of 18±2 MPa. Vancomycin was released from the BG cement into phosphate-buffered saline for up to 36 days, and the cumulative amount of vancomycin released was 86% of the amount initially loaded into the cement. In comparison, vancomycin was released from the CS cement for up 28 days and the cumulative amount released was 89%. Two months post-surgery, radiography and microbiological tests showed that the BG and CS cements had a better ability to eradicate osteomyelitis when compared to intravenous injection of vancomycin, but there was no significant difference between the BG and CS cements in eradicating the infection. Histological examination showed that the BG cement was biocompatible and had a good capacity for regenerating bone in the tibial defects.

Conclusions

These results indicate that borate BG cement is a promising material both as an injectable carrier for vancomycin in the eradication of osteomyelitis and as an osteoconductive matrix to regenerate bone after the infection is cured.

Local gentamicin application does not interfere with bone healing in a rat model

For the prophylaxis and treatment of bony infections antibiotics are locally used. Since several decades antibiotics mixed with bone cement (methylmethacrylate) are successfully used in prosthetic surgery and a gentamicin coated tibial nail is approved in Europe for fracture stabilization. The goal of the present study was to investigate if gentamicin, locally applied from a polymeric coating of intramedullary nails, might interfere with the bone healing process. Female Sprague Dawley rats (n = 72) were used and the tibiae were intramedullary stabilized with Kirschner-wires (k-wires) after osteotomy. This model was established earlier and shows a delayed healing with a prolonged inflammatory reaction. The open approach is clinically more relevant compared to a closed one because it mimics the clinically critical case of an open fracture, which has a higher risk of infection. The k-wire was either coated with the polymer poly(d,l-lactide) (control group) or with 10% gentamicin incorporated into the polymer (gentamicin group). In vivo μCT analyses were performed at days 10, 28, 42, and 84 after osteotomy. Mechanical torsional testing and histological evaluation were done at the days of sacrifice: 28, 42, and 84. The μCT analyses revealed an increase in tissue mineral density (TMD) over the healing period in both groups. In the control group, the torsional stiffness and maximum load did not reach the values of the intact contralateral side at any time point. At day 84 the gentamicin treated tibiae, however, showed significantly better maximum load compared to the control group. The histology showed no bony bridging in the control, whereas in 2 of 5 calluses of the gentamicin group mineralized bridging occurred. Significantly more mineralized tissue was measured in the gentamicin group. This study shows that the local gentamicin application does not negatively interfere with the long term healing process. Local infection prophylaxis is effective without negative effects on bone healing.

Small animal bone healing models: standards, tips, and pitfalls results of a consensus meeting

Small animal fracture models have gained increasing interest in fracture healing studies. To achieve standardized and defined study conditions, various variables must be carefully controlled when designing fracture healing experiments in mice or rats. The strain, age and sex of the animals may influence the process of fracture healing. Furthermore, the choice of the fracture fixation technique depends on the questions addressed, whereby intra- and extramedullary implants as well as open and closed surgical approaches may be considered. During the last few years, a variety of different, highly sophisticated implants for fracture fixation in small animals have been developed. Rigid fixation with locking plates or external fixators results in predominantly intramembranous healing in both mice and rats. Locking plates, external fixators, intramedullary screws, the locking nail and the pin-clip device allow different degrees of stability resulting in various amounts of endochondral and intramembranous healing. The use of common pins that do not provide rotational and axial stability during fracture stabilization should be discouraged in the future. Analyses should include at least biomechanical and histological evaluations, even if the focus of the study is directed towards the elucidation of molecular mechanisms of fracture healing using the largely available spectrum of antibodies and gene-targeted animals to study molecular mechanisms of fracture healing. This review discusses distinct requirements for the experimental setups as well as the advantages and pitfalls of the different fixation techniques in rats and mice.

Assessing the character of the rhBMP-2- and vancomycin-loaded calcium sulphate composites in vitro and in vivo

BACKGROUND

The treatment of contaminated and infected bone defects remains an intractable problem and the ideal approach is to control infection and repair the bone defect at the same time. Thus, developing an osteoconductive bone graft composite with antibiotic and growth factor release capabilities as well as osteogenesis-matched degradation properties is necessary. A new calcium sulphate composite consisting of vancomycin and rhBMP-2 was developed, and the present study assessed its efficiency in vitro and in a rabbit tibial defect model.

METHODS

Firstly, we detected the bioactivity of rhBMP-2 released from the composites by ALP assay in vitro. Then, the released vancomycin in bone tissue within 1 cm from implanted site was detected by HLPC at 1, 3, 5, 7, 14, 21 and 28 days after implantation. The rhBMP-2 concentration of tissues around the defects was also detected by ELISA. Histomorphometry and histomorphometrical analysis at 5, 14 and 28 days post-implantation was done for assessing its osteoinductivity for bone defects.

RESULTS

The results showed rhBMP-2 was still active in vitro at 29 days. In vivo, the composite released an initial bolus of vancomycin and rhBMP-2 to the bone followed by gradual release for more than 14 and 21 days, respectively. The histomorphometry indicated that the composite significantly augmented new bone formation in the defect compared to the control.

CONCLUSIONS

This composite may be a potential therapeutic agent for contaminated or infected bone defects due to its concomitant osteoinductive and antibiotic properties.

Ag/SiO(x)C(y) plasma polymer coating for antimicrobial protection of fracture fixation devices

Implant-related infections are often devastating situations in orthopaedic trauma surgery particularly if multiresistant bacteria are involved. Protection of the implant surface by an antimicrobial coating exhibiting activity against multiresistant bacterial strains is of high interest. Aim of this study was to investigate the antimicrobial effects of an Ag/SiO(x)C(y) plasma polymer coating for fracture fixation devices, such as nails, plates, and external fixators, including tests against methicillin-resistant Staphylococcus aureus (MRSA) and its biocompatibility. The antimicrobial activity of the coating deposited onto 12 x 3 mm(2) stainless steel implants was tested in vitro against Staphylococcus aureus, Staphylococcus epidermidis, and MRSA using different testing methods (ASTM E-2810, JIS Z 2801, proliferation assay). Additionally, the coated devices were implanted into the paravertebral muscle of rabbits and explanted after 2, 7, 14, and 28 days to test the remaining ex vivo antimicrobial activity. For biocompatibility assessment the Ag/SiO(x)C(y) plasma polymer coating was tested in vitro according to ISO 10993-5. The Ag/SiO(x)C(y) coating exhibited excellent antimicrobial activity against all tested bacterial strains in all three in vitro tests. Ex vivo testing proved suppression of more than 99.9 % of bacterial proliferation by the coating compared to non-coated samples even after 28 days. ISO 10993-5 showed good biocompatibility of the coating without any indications of cytotoxic effects. In summary, Ag/SiO(x)C(y) plasma polymer coating showed excellent antimicrobial activity including effectiveness against MRSA and good in vitro biocompatibility. Therefore, it possesses high potential as a prophylactic agent in orthopaedic trauma surgery.

Sustained release of vancomycin from polyurethane scaffolds inhibits infection of bone wounds in a rat femoral segmental defect model

Infection is a common complication in open fractures that compromises the healing of bone and can result in loss of limb or life. Currently, the clinical standard of care for treating contaminated open fractures comprises a staged approach, wherein the wound is first treated with non-biodegradable antibiotic-laden poly(methyl methacrylate) (PMMA) beads to control the infection followed by bone grafting. Considering that tissue regeneration is associated with new blood vessel formation, which takes up to 6 weeks in segmental defects, a biodegradable bone graft with sustained release of an antibiotic is desired to prevent the implant from becoming infected, thus allowing the processes of both vascularization and new bone formation to occur unimpeded. In the present study, we utilized biodegradable porous polyurethane (PUR) scaffolds as the delivery vehicle for vancomycin. Hydrophobic vancomycin free base (V-FB) was obtained by precipitating the hydrophilic vancomycin hydrochloride (V-HCl) at pH 8. The decreased solubility of V-FB resulted in an extended vancomycin release profile in vitro, as evidenced by the fact that active vancomycin was released for up to 8 weeks at concentrations well above both the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Using PUR prepared from lysine triisocyanate (LTI) (PUR(LTI)), the extended in vitro release profile observed for V-FB translated to improved infection control in vivo compared to V-HCl in a contaminated critical-sized fat femoral segmental defect. The performance of PUR(LTI)/V-FB was comparable to PMMA/V-HCl beads in vivo. However, compared with PMMA, PUR is a biodegradable system which does not require the extra surgical removal step in clinical use. These results suggest that PUR scaffolds incorporating V-FB could be a potential clinical therapy for treatment of infected bone defects.

Novel borate glass/chitosan composite as a delivery vehicle for teicoplanin in the treatment of chronic osteomyelitis

Composite materials composed of borate bioactive glass and chitosan (designated BGC) were investigated in vitro and in vivo as a new delivery system for teicoplanin in the treatment of chronic osteomyelitis induced by methicillin-resistant Staphylococcus aureus (MRSA). In vitro, the release of teicoplanin from BGC pellets into phosphate-buffered saline (PBS), as well as its antibacterial activity, were determined. The compressive strength of the pellets was measured after specific immersion times, and the structure of the pellets was characterized using scanning electron microscopy and X-ray diffraction. In vivo, the tibial cavity of New Zealand White rabbits was injected with MRSA strain to induce chronic osteomyelitis, treated by debridement after 4weeks, implanted with teicoplanin-loaded BGC pellets (designated TBGC) or BGC pellets, or injected intravenously with teicoplanin. After 12weeks' implantation, the efficacy of the TBGC pellets for treating osteomyelitis was evaluated using hematological, radiological, microbiological and histological techniques. When immersed in PBS, the TBGC pellets provided a sustained release of teicoplanin, while the surface of the pellets was converted to hydroxyapatite (HA). In vivo, the best therapeutic effect was observed in animals implanted with TBGC pellets, resulting in significantly lower radiological and histological scores, a lower positive rate of MRSA culture, and an excellent bone defect repair, without local or systemic side effects. The results indicate that TBGC pellets are effective in treating chronic osteomyelitis by providing a sustained release of teicoplanin, in addition to participating in bone regeneration.

A biodegradable antibiotic delivery system based on poly-(trimethylene carbonate) for the treatment of osteomyelitis

BACKGROUND AND PURPOSE

Many investigations on biodegradable materials acting as an antibiotic carrier for local drug delivery are based on poly(lactide). However, the use of poly(lactide) implants in bone has been disputed because of poor bone regeneration at the site of implantation. Poly(trimethylene carbonate) (PTMC) is an enzymatically degradable polymer that does not produce acidic degradation products. We explored the suitability of PTMC as an antibiotic releasing polymer for the local treatment of osteomyelitis.

METHODS

This study addressed 2 separate attributes of PTMC: (1) the release kinetics of gentamicin-loaded PTMC and (2) its behavior in inhibiting biofilm formation. Both of these characteristics were compared with those of commercially available gentamicin-loaded poly(methylmethacrylate) (PMMA) beads, which are commonly used in the local treatment of osteomyelitis.

RESULTS

In a lipase solution that mimics the in vivo situation, PTMC discs with gentamicin incorporated were degraded by surface erosion and released 60% of the gentamicin within 14 days. This is similar to the gentamicin release from clinically used PMMA beads. Moreover, biofilm formation by Staphylococcus aureus was inhibited by approximately 80% over at least 14 days in the presence of gentamicin-loaded PTMC discs. This is similar to the effect of gentamicin-loaded PMMA beads. In the absence of the lipase, surface erosion of PTMC discs did not occur and gentamicin release and biofilm inhibition were limited.

INTERPRETATION

Since gentamicin-loaded PTMC discs show antibiotic release characteristics and biofilm inhibition characteristics similar to those of gentamicin-loaded PMMA beads, PTMC appears to be a promising biodegradable carrier in the local treatment of osteomyelitis.

In vitro investigation of orthopedic titanium-coated and brushite-coated surfaces using human osteoblasts in the presence of gentamycin

Anti-infective coatings have been developed to protect the surfaces of cementless implants from bacterial colonization that is known to be a prerequisite for device-related infection. The aim of this study is to investigate the effect of brushite-coated arthroplasty surfaces on human osteoblasts and to evaluate the impact of concomitant exposure to gentamycin. We cultured human osteoblasts (hFOB 1.19) on brushite-coated and uncoated titanium alloy in the presence of gentamycin and analyzed cell function and vitality. Our results show that brushite-coated titanium alloy surfaces supported the function of osteoblasts and the expression of extracellular matrix even in the presence of highly dosed gentamycin. Brushite-coated titanium alloy surfaces supported osteogenic function, indicating that this coating could enhance implant osteointegration in vivo. Concomitant exposure to gentamycin slightly decreased osteoblastic activity in vitro, suggesting that there might also be negative effects in vivo. However, in vivo studies are necessary to validate these in vitro findings.

Pharmacological agents and impairment of fracture healing: what is the evidence?

Bone healing is an extremely complex process which depends on the coordinated action of several cell lineages on a cascade of biological events, and has always been a major medical concern. The use of several drugs such as corticosteroids, chemotherapeutic agents, non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, anticoagulants and drugs which reduce osteoclastic activity have been shown to affect bone healing. This review article presents our current understanding on this topic, focusing on data illustrating the effect of these drugs on fracture healing and bone regeneration.

The effects of clindamycin on human osteoblasts in vitro

INTRODUCTION

Clindamycin is an antibiotic frequently used in different local application forms for the treatment of prosthetic joint infections, chronic osteomyelitis or as infection prophylaxis in bone cement. No information is available regarding its direct effects on bone cells, although very high local effective antibiotic concentrations can be achieved.

MATERIALS AND METHODS

We cultured pooled osteoblasts, previously derived from human trabecular bone specimens of four healthy donors, with different concentrations of clindamycin (0-500 microg/ml) for 24, 48 and 72 h. Cell proliferation (MTT), cytotoxicity [lactate dehydrogenase (LDH)-activity], cell metabolism [alkaline phosphatase (ALP)-activity] and extracellular matrix calcification (Alizarin staining) were assessed after antibiotic treatment.

RESULTS

Proliferation significantly decreased in a dose-dependent manner and reached 3.5% of control samples at 500 microg/ml at 72 h. LDH-activity was unaffected at lower concentrations but significantly increased at 500 microg/ml at 48 and 72 h. ALP-activity significantly increased at 10 microg/ml at 24 and 48 h and then decreased in a time- and dose-dependent manner. Calcification increased at 10 and 25 microg/ml, while it decreased or no calcification was found at concentrations of 50 microg/ml and above.

CONCLUSION

We could demonstrate that clindamycin at lower concentrations stimulated the cell metabolism of human osteoblasts and that higher clindamycin levels of 500 microg/ml had cytotoxic effects. The observed effects of high clindamycin levels on human osteoblasts highlight a potential alteration of bone metabolism in vivo and have to be taken into account in local antibiotic administration, e.g., in clindamycin-impregnated bone cement, where such high antibiotic concentrations can be achieved.

Tissue concentrations of vancomycin and Moxifloxacin in periprosthetic infection in rats

BACKGROUND

A one-step exchange of an endoprosthesis with periprosthetic infection requires effective antibiotics at high concentrations around the endoprosthesis. We evaluated the tissue distribution of vancomycin and Moxifloxacin in a standardized in vivo model of periprosthetic infection.

METHODS

36 male rats with periprosthetic infection of the left hind leg, induced by a standardized procedure, received either antibiotic treatment with vancomycin or Moxifloxacin twice daily for 2 weeks, or a sham treatment. After the last administration, different tissues from each animal were evaluated for concentrations of antibiotic.

RESULTS

Compared to plasma, the tissue concentrations of Moxifloxacin were higher in all tissues investigated (lung, muscle, fat, bone) and the tissue-plasma ratio of Moxifloxacin was considerably higher than that of vancomycin. The concentrations of Moxifloxacin were equally high in the infected and the uninfected hind leg, whereas the vancomycin concentrations were significantly higher in the infected leg.

INTERPRETATION

The standardized model of periprosthetic infection described here can be extrapolated to different bacterial and mycotic pathogens, and also to different antibiotics or therapeutic regimes. It provides a way of correlating tissue concentrations with clinical outcome in future studies.

Effect of vitamin C on fracture healing in elderly Osteogenic Disorder Shionogi rats

We studied the effect of vitamin C on fracture healing in the elderly. A total of 80 elderly Osteogenic Disorder Shionogi rats were divided into four groups with different rates of vitamin C intake. A closed bilateral fracture was made in the middle third of the femur of each rat. Five weeks after fracture the femora were analysed by mechanical and histological testing. The groups with the lower vitamin C intake demonstrated a lower mechanical resistance of the healing callus and a lower histological grade. The vitamin C levels in blood during healing correlated with the torque resistance of the callus formed (r = 0.525). Therefore, the supplementary vitamin C improved the mechanical resistance of the fracture callus in elderly rats. If these results are similar in humans, vitamin C supplementation should be recommended during fracture healing in the elderly.

In vitro and in vivo release of ciprofloxacin from osteoconductive bone defect filler

OBJECTIVES

Impregnation of antimicrobial agents within biodegradable carriers with osteoconductive properties could provide the means for one-stage surgical treatment of osteomyelitis. In this study, the in vitro and in vivo antibiotic release from this type of bone defect filler was characterized.

METHODS

Cylindrical pellets (2.5 x 1.5 mm) were manufactured from bioabsorbable poly(L-lactide-co-glycolide) (PLGA) matrix, ciprofloxacin [8.3 +/- 0.1% (w/w)] and osteoconductive bioactive glass microspheres (90-125 microm) [27 +/- 2% (w/w)]. In vitro studies were carried out to delineate the release profile of the antibiotic. The antimicrobial activity of the release antibiotic was verified with MIC testing. In a time-sequence study in the rabbit, pellets were surgically implanted in the proximal tibia and the antibiotic concentrations achieved in bone were measured at 1, 2, 3, 4, 5 and 6 months.

RESULTS

In vitro elution studies showed sustained release of ciprofloxacin at a therapeutic level (>2 microg/mL) over a time period of 4 months. The released ciprofloxacin had maintained its antimicrobial capacity against five standard ATCC strains. In vivo, the delivery system produced high local bone concentrations (247.9 +/- 91.0 mug/g of bone) for a time period of 3 months with no significant systemic exposure. Histomorphometry and micro-CT imaging confirmed new bone formation around the pellets within 3 months as a sign of an independent osteoconductive property of the composite.

CONCLUSIONS

The tested composite seems to be a promising option for local therapy of surgically treated bone infections. The main advantages are the antibiotic release for a definite time period with therapeutic concentrations, which may minimize slow residual release at suboptimal concentrations.

Local antibiotic delivery vehicles in the treatment of musculoskeletal infection

The primary benefit achieved with local antibiotic delivery vehicles is the ability to obtain extremely high levels of local antibiotics without increasing systemic toxicity. Antibiotic-loaded bone cement represents the current standard as an antibiotic delivery vehicle in orthopaedic surgery. Biodegradable alternatives to antibiotic-loaded bone cement also are being used clinically and there are many new products in the active stages of development. These alternatives can be categorized as bone graft, bone graft substitutes or extenders, natural polymers (protein-based products), and synthetic polymers. Composite biomaterials that simultaneously provide the functions of variable antibiotic delivery patterns and also contribute to the process of bone regeneration represent the most ideal class of local antibiotic delivery vehicles. High concentrations of certain antibiotics have been shown to affect the process of normal bone regeneration adversely in a dose dependent response. Considerable investigation still is required to determine the proper use of locally administered antibiotics to negotiate the balance between eradicating infection without excessively inhibiting the processes of bone regeneration.