Local antibiotic delivery with demineralized bone matrix

Palmitic acid coating of allogeneic cancellous bone for local antibiotic treatment: A porcine impaction bone grafting model

Introduction

The worldwide rising number of joint replacements results in increasing revision surgery including a relevant portion of septic loosening accompanied by bone deficiencies. Loading of allogeneic bone with antibiotics provides high local antibiotic concentrations and might eradicate bacteria which appear resistant to systemic antibiotic application. Hydrophobic palmitic acid was shown to be a suitable carrier for antibiotics and prevents biofilm.

Methods

Cancellous bone derived from 6 to 7 months old piglets was used for a standardized in vitro impaction bone grafting model according to previous studies. The specimens were either thermodisinfected or remained native and palmitic acid with one third and two third partial weight were added and compared with control. Shear force at the interface prosthesis to cement and between cement and bone was measured. The relative micromovements were measured with 6 inductive sensors with a resolution of 0.1 μm at three different measuring heights up to a maximum movement of 150 μm between cement and bone. Taking into account the corresponding applied torque the measured values were normalized in μm/Nm. Statistical analysis was done with SPSS Statistics® Version 26.0 IBM.

Results

Smallest movement was measured for thermodisinfected cancellous bone and a not significant decrease of shear force resistance with addition of palmitic acid was found since supplementing native cancellous bone reduced shear force resistance significantly depending on the weight percentage of palmitic acid.

Conclusion

Supplementation of porcine cancellous bone with palmitic acid did not significantly reduce shear force resistance of thermodisinfected bone since adding palmitic acid to native bone decreased it significantly depending on the volume added. Palmitic acid seems to be a suitable coating for allogeneic cancellous bone to deliver high local antibiotic concentrations and thermodisinfected cancellous bone might be able to store larger volumes of palmitic acid than native bone without relevant influence on shear force resistance.

New dual-function in situ bone repair scaffolds promote osteogenesis and reduce infection

Background

The treatment of infectious bone defects is a difficult problem to be solved in the clinic. In situ bone defect repair scaffolds with anti-infection and osteogenic abilities can effectively deal with infectious bone defects. In this study, an in situ polycaprolactone (PCL) scaffold containing ampicillin (Amp) and Mg microspheres was prepared by 3D printing technology.

Results

Mg and Amp were evenly distributed in PCL scaffolds and could be released slowly to the surrounding defect sites with the degradation of scaffolds. In vitro experiments demonstrated that the PCL scaffold containing Mg and Amp (PCL@Mg/Amp) demonstrated good cell adhesion and proliferation. The osteogenic genes collagen I (COL-I) and Runx2 were upregulated in cells grown on the PCL@Mg/Amp scaffold. The PCL@Mg/Amp scaffold also demonstrated excellent antibacterial ability against E. coli and S. aureus. In vivo experiments showed that the PCL@Mg/Amp scaffold had the strongest ability to promote tibial defect repair in rats compared with the other groups of scaffolds.

Conclusions

This kind of dual-function in situ bone repair scaffold with anti-infection and osteogenic abilities has good application prospects in the field of treating infectious bone defects.

Role of Implantable Drug Delivery Devices with Dual Platform Capabilities in the Prevention and Treatment of Bacterial Osteomyelitis

As medicine advances and physicians are able to provide patients with innovative solutions, including placement of temporary or permanent medical devices that drastically improve quality of life of the patient, there is the persistent, recurring problem of chronic bacterial infection, including osteomyelitis. Osteomyelitis can manifest as a result of traumatic or contaminated wounds or implant-associated infections. This bacterial infection can persist as a result of inadequate treatment regimens or the presence of biofilm on implanted medical devices. One strategy to mitigate these concerns is the use of implantable medical devices that simultaneously act as local drug delivery devices (DDDs). This classification of device has the potential to prevent or aid in clearing chronic bacterial infection by delivering effective doses of antibiotics to the area of interest and can be engineered to simultaneously aid in tissue regeneration. This review will provide a background on bacterial infection and current therapies as well as current and prospective implantable DDDs, with a particular emphasis on local DDDs to combat bacterial osteomyelitis.

Effect of synthetic bone replacement material of different size on shear stress resistance within impacted native and thermodisinfected cancellous bone: an in vitro femoral impaction bone grafting model

Antibiotic carrier particles of variable size might influence mechanic properties within impacted thermodisinfected and native cancellous bone different. Herafill®G containing calciumsulfate and calciumcarbonate provides high local concentrations of gentamicin being important for revision surgery in infected joint replacements. Native and thermodisinfected cancellous bone derived from 6 to 7 months old piglets was used for in vitro impaction bone grafting and supplemented each with Herafill®G granules of two different sizes. Micromovement of implants related to shear force was measured in 29 specimens distributed in 6 groups. Thermodisinfected cancellous bone revealed a significant higher shear force resistance than native bone with a mean difference of 423.8 mdeg/Nm (p < 0.001) ranging within 95% confidence interval from 181.5 to 666.0 mdeg/Nm. Adding small granules to thermodisinfected bone did not reduce shear force resistance significantly since adding large granules to native bone improved it by 344.0 mdeg/Nm (p < 0.003). Shear force resistance was found higher at the distal region of the implant compared to a proximal point of measurement throughout all specimens. Less impaction impulses were necessary for thermodisinfected bone. Thermodisinfected cancellous bone might achieve a higher degree of impaction compared with native bone resulting in increased resistance against shear force since impaction was found increased distally. Supplementation of thermodisinfected bone with small granules of Herafill®G might be considered for application of local antibiotics. Large granules appeared more beneficial for supplementation of native bone. Heterogeneity of bone graft and technical aspects of the impaction procedure have to be considered regarding the reproducibility of femoral impaction bone grafting.

Preparation of Poly(MTZ) n -(DMAEMA) m Micelles and Study on Their Antibacterial Property

Bacterial infections are the most common type of clinical infection. The abuse of clinical antibiotics has led to the frequent appearance of drug-resistant strains and even some super bacteria. In this study, we synthesized Poly(MTZ) _n -(DMAEMA) _m polymer micelles with cations on the surface. The synthesis of this novel polymer comes in two steps. First, Poly(MTZ) _n was synthesized with metronidazole (MTZ) referred as the macromolecular chain transfer agent and v-501 as the initiator for initiating the polymerization of 4-cyanopentanoic acid dithiobenzoate. Then, novel polymer micelles were synthesized with Poly(MTZ) _n referred as the macromolecular chain transfer agent and v-501 as the initiator for initiating the polymerization of the monomer 2-(dimethylamino) ethyl methacrylate, which could adsorb to the negatively charged bacterial surface via electrostatic interaction and enhance bactericidal activity. Scanning electron microscopy showed that the micelles could be accurately targeted to the surface of bacteria, and the zone of inhibition assay confirmed that the micelles could enhance the sensitivity of bacteria to drugs. Hence, Poly(MTZ) _n -(DMAEMA) _m polymer micelles will have potential use for the clinical treatment of anaerobic infections in the future.

The Road to Survival for Haemodynamically Unstable Patients With Open Pelvic Fractures

Management of haemodynamically unstable pelvic ring injuries has been simplified into treatment algorithms to streamline care and emergent decision making in order to improve patient outcomes whilst decreasing mortality and morbidity. Pelvic ring injuries are most commonly a result of high-velocity and energy forces that exert trauma to the pelvic bones causing not only damage to the bone but the surrounding soft-tissue, organs, and other structures and are usually accompanied by injuries to other parts of the body resulting in a polytraumatised patient. Open pelvic fractures are a rare subset of pelvic ring fractures that are on the more severe end of the pelvic fracture continuum and usually produce uncontrolled haemorrhage from fractured bone, retroperitoneal haematomas, intraabdominal bleeding from bowel injury, soft tissue injuries to the anus, perineum, and genitals, fractures of the pelvic bones, causing bleeding from cancellous bone, venous, and arterial injuries combined with bleeding from concomitant injuries. This is a very complex and challenging clinical situation and timely and appropriate decisions and action are paramount for a positive outcome. Consequently, open pelvic fractures have an extremely high rate of mortality and morbidity and outcomes remain poor, despite evidence-based improvements in treatment, knowledge, and identification of haemorrhage; in the pre-hospital, critical care, and operative settings. In the future utilisation of haemostatic drugs, dressings, devices, and procedures may aid in the time to haemorrhage control.

Native Bovine Hydroxyapatite Powder, Demineralised Bone Matrix Powder, and Purified Bone Collagen Membranes Are Efficient in Repair of Critical-Sized Rat Calvarial Defects

Here we evaluated the efficacy of bone repair using various native bovine biomaterials (refined hydroxyapatite (HA), demineralised bone matrix (DBM), and purified bone collagen (COLL)) as compared with commercially available bone mineral and bone autografts. We employed a conventional critical-sized (8 mm diameter) rat calvarial defect model (6-month-old male Sprague–Dawley rats, n = 72 in total). The artificial defect was repaired using HA, DBM, COLL, commercially available bone mineral powder, bone calvarial autograft, or remained unfilled (n = 12 animals per group). Rats were euthanised 4 or 12 weeks postimplantation (n = 6 per time point) with the subsequent examination to assess the extent, volume, area, and mineral density of the repaired tissue by means of microcomputed tomography and hematoxylin and eosin staining. Bovine HA and DBM powder exhibited excellent repair capability similar to the autografts and commercially available bone mineral powder while COLL showed higher bone repair rate. We suggest that HA and DBM powder obtained from bovine bone tissue can be equally applied for the repair of bone defects and demonstrate sufficient potential to be implemented into clinical studies.

Which type of bone releases the most vancomycin? Comparison of spongious bone, cortical powder and cortico-spongious bone

Bone infections can be challenging to treat and can lead to several surgeries and relapses. When a graft is needed, cavitary bone loss can be grafted with cancellous or cortical bone. Both can be used for grafting. However, the antibiotic releasing capacity of these grafts has not been compared. Which type of bone is best at releasing the most antibiotic has not been well established. The aim of this study was to determine which type of bone is best for antibiotic release when the bone is suffused with antibiotics by the surgeon. The hypothesis is that there would be a difference between the type of bone tested due to different release capacities of cortical and cancellous bone. This was an experimental study. Cortical spongy bone in chips, Spongy bone in chips and demineralized cortical bone powder were compared. For each type of bone, 5 samples were tested. Processed and decontaminated grafts were freeze-dried to be kept at room temperature. The primary endpoint was the amount of vancomycin released by the graft as it affects the concentration of antibiotic around the graft in clinical practice. The procedure for the study consisted of full graft immersion in a vancomycin solution. Then, the liquid was removed with aspiration. In order to measure the quantity of antibiotic released, the bone was put into distilled water in agitation in a heated rocker at 37 °C. After 30 min of soaking, 1 mL of the liquid was removed. The same extraction process was also carried out after 60 min soaking, 2 h, 3 h, 24 h, and 48 h. No differences were found between each type of bone relative to the concentration of vancomycin released at each time of the assessment. There was a significant difference in the weight of the bone with a higher weight for the cortical powder (1.793 g) versus cortical spongy bone and spongy bone (1.154 g and 1.013 g) with a p value < 0.0001. A significant difference was seen in the weight of the bone with vancomycin after the aspiration of the liquid with 3.026 g for cortical powder, 2.140 g and 2.049 g for the cortical spongy bone and the spongy bone with a p value < 0.0001. In daily clinical practice, one can use cancellous bone, cortico-cancellous bone or cortical powder in order to add vancomycin to a bone graft. Our results show the release kinetics of the soaked allografts. With a maximum of 14 mg/mL in the first minutes and a rapid decrease it shows a pattern comparable to antibiotic loaded bone cement. The method used appears favourable for prophylactic use, protecting the graft against contamination at implantation, but is not sufficient for treating chronic bone infection. LEVEL OF EVIDENCE: V.

Impact of Gentamicin-Loaded Bone Graft on Defect Healing in a Sheep Model

Infections of bone are severe complications, and an optimization of grafting material with antimicrobial drugs might be useful for prevention and treatment. This study aimed to investigate the influence of gentamicin-loaded bone graft on the healing of bone defects in a sheep model. Metaphyseal and diaphyseal drill hole defects (diameter: 6 mm, depth: 15 mm) were filled with graft or gentamicin-loaded graft (50 mg/g graft) or were left untreated. Analysis of regeneration after three and nine weeks, micro-computed tomography (μCT), and histology revealed a significant increase in bone formation in the drill hole defects, which began at the edges of the holes and grew over time into the defect center. The amount of graft decreased over time due to active resorption by osteoclasts, while osteoblasts formed new bone. No difference between the groups was seen after three weeks. After nine weeks, significantly less mineralized tissue was formed in the gentamicin-loaded graft group. Signs of inflammatory reactions were seen in all three groups. Even though the applied gentamicin concentration was based on the concentration of gentamicin mixed with cement, the healing process was impaired. When using local gentamicin, a dose-dependent, compromising effect on bone healing should be considered.

Bimodal antibacterial system based on quaternary ammonium silane-coupled core-shell hollow mesoporous silica

Hollow mesoporous silica (HMS) have been extensively investigated as a biomaterial for drug delivery. The present study developed quaternary ammonium silane-grafted hollow mesoporous silica (QHMS) to create a metronidazole (MDZ) sustained delivery system, MDZ@QHMS, with bimodal, contact-kill and release-kill capability. The QHMS was assembled through a self-templating method. Metronidazole was incorporated within the QHMS core using solvent evaporation. Antibacterial activities of the MDZ@QHMS were investigated using single-species biofilms of Staphylococcus aureus (ATCC25923), Escherichia coli (ATCC25922) and Porphyromonas gingivalis (ATCC33277). The MDZ@QHMS maintained a hollow mesoporous structure and demonstrated sustained drug release and bacteridal actvity against the three bacterial strains at a concentration of 100 μg/mL or above. These nanoparticles were not relatively cytotoxic to human gingival fibroblasts when employed below 100 µg/mL. Compared with HMS, the MDZ@QHMS system at the same concentration demonstrated antibiotic-elution and contact-killing bimodal antibacterial activities. The synthesized drug carrier with sustained, bimodal antibacterial function and minimal cytotoxicity possesses potential for localized antibiotic applications. STATEMENT OF SIGNIFICANCE: The present study develops quaternary ammonium silane-grafted hollow mesoporous silica (QHMS) to create a metronidazole (MDZ) sustained delivery system, MDZ@QHMS, with bimodal, contact-kill and release-kill capability. This system demonstrates sustained drug release and maintained a hollow mesoporous structure. The synthesized drug carrier with sustained, bimodal antibacterial function and excellent biocompatibility possesses potential for localized antibiotic applications.

Intra-articular Gentamicin-loaded PLA Microparticle Injection for the Treatment of Septic Arthritis in Rabbits

BACKGROUND

Because local delivery of drugs induces high concentrations, it could be helpful to apply these delivery systems to the treatment of septic arthritis by antibiotics. Thus, a gentamicin-loaded polymer was tested in a rabbit model of Staphylococcus aureus septic arthritis.

METHODS

Thirty New Zealand rabbits were split into five groups: A: infection only; B: infection and systemic gentamicin treatment; C: infection and unloaded polymer and systemic gentamicin treatment; D: infection and gentamicin-loaded polymer only; and E: no infection and unloaded polymer. After inducing nonlethal septic arthritis in the knee joint by injecting 10 colony-forming units (CFUs) of a strain of methicillin-sensitive S aureus in groups A, B, C, and D, rabbits were housed for 15 days, and then the joint capsules were removed and the remaining bacteria were counted. Bacterial load was expressed in CFUs per gram of synovial tissue. In group E, capsules were removed, and a pathologic examination was done.

RESULTS

At day 15, the bacterial load was 6 × 10, 2 × 10, 1.8 × 10, and 7 × 10 CFU/g of tissue for groups A, B, C, and D, respectively. Compared with the mean of groups A, B, and C, the bacterial load of group D was 4.94 units of log10 CFU/g lower than that of these groups. The bacterial load of group D was statistically significantly lower than that of the other three groups. Noticeably, two animals of group D had a nil bacterial count. In group E animals, a minimal foreign body reaction was observed around the polymer.

DISCUSSION

Gentamicin-containing microparticles were more efficient in reducing bacterial load than systemic injections of gentamicin and thus have an interesting role to play in the treatment of human arthritis. However, inserting microparticles in joints is not easy, and hydrogels might be a good alternative approach.

A review of local antibiotic implants and applications to veterinary orthopaedic surgery

In the face of increasing incidence of multidrug resistant implant infections, local antibiotic modalities are receiving increased attention for both infection prophylaxis and treatment. Local antibiotic therapy that achieves very high antibiotic drug concentrations at the site of the implant may represent an avenue for treatment of biofilmforming bacterial pathogens. Randomized controlled trials in human patients have demonstrated an infection risk reduction when antibiotic-impregnated cement is used for infection prophylaxis in implanted joint prostheses, and when a gentamicin-impregnated collagen sponge is used for infection prophylaxis in midline sternotomy. The other modalities discussed have for the most part yet to be evaluated in randomized controlled trials in veterinary or human patients. In general, the in vivo pharmacokinetics and appropriate dosing profiles for local antibiotic modalities have yet to be elucidated. Toxicity is possible, and attention to the dose applied is warranted.

Elution kinetics of vancomycin and gentamicin from carriers and their effects on mesenchymal stem cell proliferation: an in vitro study

BACKGROUND

Musculoskeletal infections remain a major complication in orthopedic surgery. The local delivery of antibiotics provides the high levels required to treat an infection without systemic toxicity. However, the local toxicity of antibiotic carriers to the mesenchymal stem cells, as a result of both the peak concentrations and the type of carrier, may be significant.

METHODS

To address this concern, the elution kinetics of vancomycin and gentamicin from several commercially available antibiotic carriers and several carriers impregnated by a surgeon (10 ml of each sterile carrier were manually mixed with a 500 mg vancomycin and an 80 mg gentamicin solution, and the duration of impregnation was 30 min) were assessed. Moreover, the effects of these antibiotic carriers on stem cell proliferation were investigated. The following two types of stem cells were used: bone marrow and dental pulp stem cells.

RESULTS

The high eluted initial concentrations from antibiotic impregnated cancellous allogeneic bone grafts (which may be increased with the addition of fibrin glue) did not adversely affect stem cell proliferation. Moreover, an increased dental pulp stem cell proliferation rate in the presence of antibiotics was identified. In contrast to allogeneic bone grafts, a significant amount of antibiotics remained in the cement. Despite the favorable elution kinetics, the calcium carriers, bovine collagen carrier and freeze-dried bone exhibited decreased stem cell proliferation activity even in lower antibiotic concentrations compared with an allogeneic graft.

CONCLUSIONS

This study demonstrated the benefits of antibiotic impregnated cancellous allogeneic bone grafts versus other carriers.

Antibiotic-loaded bone void filler accelerates healing in a femoral condylar rat model

AIMS

Demineralised bone matrix (DBM) is rarely used for the local delivery of prophylactic antibiotics. Our aim, in this study, was to show that a graft with a bioactive glass and DBM combination, which is currently available for clinical use, can be loaded with tobramycin and release levels of antibiotic greater than the minimum inhibitory concentration for Staphylococcus aureus without interfering with the bone healing properties of the graft, thus protecting the graft and surrounding tissues from infection.

MATERIALS AND METHODS

Antibiotic was loaded into a graft and subsequently evaluated for drug elution kinetics and the inhibition of bacterial growth. A rat femoral condylar plug model was used to determine the effect of the graft, loaded with antibiotic, on bone healing.

RESULTS

We found that tobramycin loaded into a graft composed of bioglass and DBM eluted antibiotic above the minimum inhibitory concentration for three days in vitro. It was also found that the antibiotic loaded into the graft produced no adverse effects on the bone healing properties of the DBM at a lower level of antibiotic.

CONCLUSION

This antibiotic-loaded bone void filler may represent a promising option for the delivery of local antibiotics in orthopaedic surgery. Cite this article: Bone Joint J 2016;98-B:1126-31.

Biomaterials with Antibacterial and Osteoinductive Properties to Repair Infected Bone Defects

The repair of infected bone defects is still challenging in the fields of orthopedics, oral implantology and maxillofacial surgery. In these cases, the self-healing capacity of bone tissue can be significantly compromised by the large size of bone defects and the potential/active bacterial activity. Infected bone defects are conventionally treated by a systemic/local administration of antibiotics to control infection and a subsequent implantation of bone grafts, such as autografts and allografts. However, these treatment options are time-consuming and usually yield less optimal efficacy. To approach these problems, novel biomaterials with both antibacterial and osteoinductive properties have been developed. The antibacterial property can be conferred by antibiotics and other novel antibacterial biomaterials, such as silver nanoparticles. Bone morphogenetic proteins are used to functionalize the biomaterials with a potent osteoinductive property. By manipulating the carrying modes and release kinetics, these biomaterials are optimized to maximize their antibacterial and osteoinductive functions with minimized cytotoxicity. The findings, in the past decade, have shown a very promising application potential of the novel biomaterials with the dual functions in treating infected bone defects. In this review, we will summarize the current knowledge of novel biomaterials with both antibacterial and osteoinductive properties.

Osteogenic response and osteoprotective effects in vivo of a nanostructured titanium surface with antibacterial properties

In implantology, as an alternative approach to the use of antibiotics, direct surface modifications of the implant addressed to inhibit bacterial adhesion and to limit bacterial proliferation are a promising tactic. The present study evaluates in an in vivo normal model the osteogenic response and the osteointegration of an anodic spark deposition nanostructured titanium surface doped with gallium (ASD + Ga) in comparison with two other surface treatments of titanium: an anodic spark deposition treatment without gallium (ASD) and an acid etching treatment (CTR). Moreover the study assesses the osteoprotective potential and the antibacterial effect of the previously mentioned surface treatments in an experimentally-induced peri-implantitis model. The obtained data points out a more rapid primary fixation in ASD and ASD + Ga implants, compared with CTR surface. Regarding the antibacterial properties, the ASD + Ga surface shows osteoprotective action on bone peri-implant tissue in vivo as well as an antibacterial effect within the first considered time point.

Coating with a novel gentamicinpalmitate formulation prevents implant-associated osteomyelitis induced by methicillin-susceptible Staphylococcus aureus in a rat model

PURPOSE

Implant-associated osteomyelitis still represents a demanding challenge due to unfavourable biological conditions, bacterial properties and incremental resistance to antibiotic treatment. Therefore different bactericide or bacteriostatic implant coatings have been developed recently to control local intramedullary infections. Controlled local release of gentamicin base from a highly lipophilic gentamicin palmitate compound achieves extended intramedullary retention times and thus may improve its bactericide effect.

METHODS

Forty male Sprague-Dawley rats were divided into two groups receiving an intramedullary femoral injection of 10(2) colony-forming units (CFU) of a common methicillin susceptible Staphylococcus aureus strain (MSSA Rosenbach) and either an uncoated femur nail (Group I) or a nail coated with gentamicin palmitate (Group II). Animals were observed for 28 and 42 days. Serum haptoglobin and relative weight gain were assessed as well as rollover cultures of explanted femur nails and histological scores of periprosthetic infection in dissected femurs.

RESULTS

Implants coated with gentamicin palmitate significantly reduced periprosthetic bacterial growth as well as signs of systemic inflammation compared with uncoated implants.

CONCLUSIONS

Gentamicin palmitate appears to be a viable coating for the prevention of implant-associated infections. These findings will have to be confirmed in larger animal models as well as in clinical trials.

Coatings and surface modifications imparting antimicrobial activity to orthopedic implants

Bacterial colonization and biofilm formation on an orthopedic implant surface is one of the worst possible outcomes of orthopedic intervention in terms of both patient prognosis and healthcare costs. Making the problem even more vexing is the fact that infections are often caused by events beyond the control of the operating surgeon and may manifest weeks to months after the initial surgery. Herein, we review the costs and consequences of implant infection as well as the methods of prevention and management. In particular, we focus on coatings and other forms of implant surface modification in a manner that imparts some antimicrobial benefit to the implant device. Such coatings can be classified generally based on their mode of action: surface adhesion prevention, bactericidal, antimicrobial-eluting, osseointegration promotion, and combinations of the above. Despite several advances in the efficacy of these antimicrobial methods, a remaining major challenge is ensuring retention of the antimicrobial activity over a period of months to years postoperation, an issue that has so far been inadequately addressed. Finally, we provide an overview of additional figures of merit that will determine whether a given antimicrobial surface modification warrants adoption for clinical use.

Analysis of parameters influencing the release of antibiotics mixed with bone grafting material using a reliable mixing procedure

Local infections arising from fracture fixation, defect reconstruction or joint replacement can cause extreme pain and impaired healing, lead to revision operations, prolong hospital stay and increase costs. Treatment options including prophylaxis are afforded by the use of grafts and biomaterials loaded with antibiotics. These can produce local therapeutic concentrations with a reduced systemic concentration and reduced systemic side-effects. Patient-specific loading of osteogenic graft materials with antibiotic could be an important option for orthopaedic surgeons. A local therapeutic concentration must be available for the desired duration and cytotoxic effects must be kept within an acceptable range. The present study investigates a simple and reliable mixing procedure that could be used for the perioperative combination of antibiotic powders and solutions with bone grafting materials. The potential influence of concentration and sampling regime on the release kinetics of gentamicin, tobramycin and vancomycin was studied over a period of 56days and potency and cytotoxicity were evaluated. In all treatment groups, gentamicin and tobramycin were completely released within 3days whilst vancomycin was released over a period of 14days. The results clearly show that the main parameter influencing release is the molecular weight of the drug. Growth of Staphylococcus aureus was inhibited in all 3 treatment groups for at least 3days. Cell viability and alkaline phosphatase activity of primary osteoblast-like cells were not significantly affected by the antibiotic concentrations obtained from the elution experiments. Bone grafting is an established component of surgery for bone defect filling and for biological stimulation of healing. Patient-specific enhancement of such procedures by incorporation of antibiotics for infection prevention or by addition of cytokines for promotion of impaired healing or for treatment of critical size defects will be a relevant issue in the future.

Use of lincomycin-impregnated demineralized freeze-dried bone allograft in the periodontal defect after third molar surgery

PURPOSE

The aim of the present study was to evaluate the periodontal regenerative capacity of demineralized freeze-dried bone allograft (DFDBA) alone or used with local lincomycin.

MATERIALS AND METHODS

In the present single-blind, randomized, controlled clinical trial, 20 subjects 26 years old or older, requiring extraction of bilateral third molars (M3s), were included. Each subject was randomly assigned to receive either DFDBA or DFDBA plus lincomycin therapy. Within the subjects, 1 M3 site was randomly selected to be the experimental site and the contralateral served as the control and was permitted to heal without intervention. The primary variables were changes in the probing depth (PD), clinical alveolar bone levels (ABLs), and radiographic alveolar bone density (ABD) on the distal aspect of second molar between baseline (immediately postoperatively) and 26 weeks postoperatively (T26). Appropriate sample sizes and descriptive, bivariate, and multivariate statistics were computed.

RESULTS

For both treatment and control sites, between T0 and T26, statistically significant improvements were seen in the ABLs and ABD (P < .05). Within-subject comparisons showed no significant differences in PD, ABL, or ABD between the treatment and control M3 sites at T0 or T26 (P > .05). Also, no significant differences were found in the PD, ABL, or ABD between the 2 treatment M3 sites at T26 (P > .05).

CONCLUSIONS

The results of the present study have revealed that the PD, ABL, and ABD improved after M3 removal in subjects 26 years old or older, irrespective of the treatment or control group. Reconstructive procedures (e.g., DFDBA with or without lincomycin therapy) did not offer predictable benefits compared with a no-treatment protocol in patients younger than 30 years old.

Multipotent adult progenitor cell-loaded demineralized bone matrix for bone tissue engineering

Multipotent adult progenitor cells (MAPCs) from bone marrow have been shown to be capable of forming bone, cartilage and other connective tissues. In addition, MAPCs differentiate into lineages that are different from their germ layers of origin. Previous studies showed the ability of MAPCs to improve cardiac function and control allogenic-reactive responses associated with acute graft versus host disease. In the current study, we evaluated the ability of MAPCs to produce bone matrix on demineralized bone allograft substrates. Specifically, MAPCs expressed alkaline phosphatase, produced extracellular matrix proteins and deposited calcium-containing mineral on demineralized bone matrices. Furthermore, the addition of MAPCs on demineralized bone matrix (DBM) scaffolds enhanced osteoinductivity of the carrier in a rat ectopic pouch model. These results demonstrated the potential of MAPCs as a new approach for bone repair in tissue-engineering applications.

Demineralized bone matrix as a vehicle for delivering endogenous and exogenous therapeutics in bone repair

As a unique human bone extract approved for implant use, demineralized bone matrix (DBM) retains substantial amounts of endogenous osteoconductive and osteoinductive proteins. Commercial preparations of DBM represent a clinically accessible, familiar, widely used and degradable bone-filling device, available in composite solid, strip/piece, and semi-solid paste forms. Surgically placed and/or injected, DBM releases its constituent compounds to bone sites with some evidence for inducing new bone formation and accelerating healing. Significantly, DBM also has preclinical history as a drug carrier by direct loading and delivery of several important classes of therapeutics. Exogenous bioactive agents, including small molecule drugs, protein and peptide drugs, nucleic acid drugs and transgenes and therapeutic cells have been formulated within DBM and released to bone sites to enhance DBM's intrinsic biological activity. Local release of these agents from DBM directly to surgical sites in bone provides improved control of dosing and targeting of both endogenous and exogenous bioactivity in the context of bone healing using a clinically familiar product. Given DBM's long clinical track record and commercial accessibility in standard forms and sources, opportunities to formulate DBM as a versatile matrix to deliver therapeutic agents locally to bone sites in orthopedic repair and regenerative medicine contexts are attractive.