Treatment of osteomyelitis with antibiotic-soaked porous glass ceramic

Gentamicin Released from Porous Scaffolds Fabricated by Stereolithography

Porous oligolactide-hydroxyapatite composite scaffolds were obtained by stereolithographic fabrication. Gentamicin was then coated on the scaffolds afterwards, to achieve antimicrobial delivery ability to treat bone infection. The scaffolds examined by stereomicroscope, SEM, and μCT-scan showed a well-ordered pore structure with uniform pore distribution and pore interconnectivity. The physical and mechanical properties of the scaffolds were investigated. It was shown that not only porosity but also scaffold structure played a critical role in governing the strength of scaffolds. A good scaffold design could create proper orientation of pores in a way to strengthen the scaffold structure. The drug delivery profile of the porous scaffolds was also analyzed using microbiological assay. The release rates of gentamicin from the scaffolds showed prolonged drug release at the levels higher than the minimum inhibitory concentrations for S. aureus and E. coli over a 2-week period. It indicated a potential of the scaffolds to serve as local antibiotic delivery to prevent bacterial infection.

Drug treatments for prosthetic joint infections in the era of multidrug resistance

INTRODUCTION

Despite many advances, the management of prosthetic joint infection is still a complex issue. Moreover, in recent years the problem of antimicrobial resistance has emerged as an important challenge.

AREAS COVERED

We analysed recent advances in different aspects of prosthetic joint infections. The importance of biofilms needs to be considered for antibiotic selection because, when embedded in these structures, bacteria acquire resistant behaviour. Moreover, the presence of resistance mechanisms in some species of organisms increases the difficulty of management. In this sense, the growing importance of methicillin-resistant staphylococci, multidrug-resistant Enterobacteriaceae or Pseudomonas aeruginosa is of increasing concern. Together with these organisms, others with constitutive resistance against most antibiotics (like Enterococcus sp., mycobacteria or fungi) represent a similar problem for selection of therapy. Research into new materials that can be used as drug carriers opens a new field for management of these infections and will likely come to the front line in the coming years.

EXPERT OPINION

Individualised therapies should carefully consider the aetiology, pathogenesis and antimicrobial susceptibility. Satisfactory clinical outcome could be further fostered by enhancing the multidisciplinary approach, with better collaboration in the antibiotic selection and the surgical management.

Local antibiotic therapy strategies in orthopaedic trauma: Practical tips and tricks and review of the literature

The use of local antibiotics for the prevention of infection in the setting of open fractures and as part of the treatment of osteomyelitis is well established. Antibiotics are most commonly incorporated into polymethylmethacrylate (PMMA) cement, which can then be formed into beads, moulded to fit a bone defect or used to coat a guide wire or IM nail. Newer delivery vehicles and techniques are being evaluated to improve upon these methods. Many factors influence how local antibiotics are applied. Treatment strategies are challenging to standardise due to the variability of clinical presentations. The presence of hardware, upper versus lower extremity, healed versus non-healed fracture and quality of soft tissues overlying the affected bone, as well as patients' comorbidities all need to be considered. Despite the accepted use of local antibiotic therapy in orthopaedic trauma, high-quality evidence regarding the use of local antibiotics is lacking. Indications, techniques, dosages, types of antibiotics, elution properties and pharmacokinetics are poorly defined in the clinical setting. The purpose of our manuscript is to review current strategies and provide practical tips for local application of antibiotics in orthopaedic trauma. We focus on delivery vehicles, types of antibiotics, dosage recommendations when mixed with PMMA and indications.

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.

Two-stage revision surgery for hip prosthesis infection using antibiotic-loaded porous hydroxyapatite blocks

BACKGROUND

Infection of a hip prosthesis is one of the most severe complications encountered in orthopedic practice. Two-stage reconstruction using an antibiotic-impregnated cement spacer has become a popular procedure for the treatment of this condition. However, there are some disadvantages with the use of antibiotic-loaded cement, including low biocompatibility, a very low release ratio, and the possibility of thermal damage to the antibiotic. We have developed an effective drug delivery system for osteomyelitis in which porous hydroxyapatite (HA) blocks are loaded with an antibiotic by the vacuum method. We report here a modification of this delivery system applied for the first stage of two-stage reconstruction surgery against infected hip prosthesis.

PATIENTS AND METHODS

Eight consecutive patients who developed hip prosthesis infection underwent two-stage revision total hip arthroplasty (THA) using antibiotic-loaded porous HA blocks prepared by the vacuum method. Thorough debridement and insertion of antibiotic-loaded HA blocks was performed in the first stage, followed by conversion to THA after eradication of infection in the second stage.

RESULTS

The mean interval between the stages was 16.8 weeks. There were no complications related to the use of the antibiotic-loaded HA blocks. The patients were followed up for an average of 49 months with no evidence of recurrent infection. The mean Japanese Orthopedic Association hip score improved from 45.1 before surgery to 79.6 at the latest follow-up.

INTERPRETATION

This simple approach utilizing antibiotic-impregnated HA blocks prepared by the vacuum method is considered to be effective for treatment of hip prosthesis infection.

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.

Biodegradable microspherical implants containing teicoplanin for the treatment of methicillin-resistant Staphylococcus aureus osteomyelitis

BACKGROUND

The aim of this study was to prepare poly(d,l-lactide-co-glycolide) (PLGA) microspherical implants containing teicoplanin (TCP) using a double emulsion solvent evaporation method and to evaluate its efficacy for the local treatment of chronic osteomyelitis.

METHODS

The particle size and distribution, morphological characteristics, thermal behaviour, drug content, encapsulation efficiency and in vitro release assessments of the formulations were carried out. Sterile TCP–PLGA microspheres were implanted in the proximal tibia of rats with methicillin resistant Staphylococcus aureus (MRSA) osteomyelitis. After 3 weeks of treatment, bone samples were analysed with a microbiological assay and evaluated histopathologically.

RESULTS

Microspheres between the size ranges of 2.01 and 3.91 μm were obtained. Production yield of all formulations was found to be higher than 82% and encapsulation efficiencies of 33.6–69.8% were obtained. DSC thermogram showed that the TCP was in an amorphous state in microspheres. In vitro drug release studies had indicated that the drug release rate of microspheres was decreased upon increasing the polymer:drug ratio. Based on the in vivo data, rats treated with implants and intramuscular injection showed 1.7 × 10(3) ± 1.3 × 10(3) and 5.8 × 10(4) ± 5.3 × 10(4) colony forming unit of MRSA in 1 g bone samples (CFU/g), respectively (P < 0.01).

CONCLUSIONS

The in vitro and in vivo studies had shown that the TCP–PLGA microspheres were effective for the treatment of chronic osteomyelitis in an animal experimental model. Hence, these microspheres may be potentially useful in the clinical setting with the need for further investigation for optimal dosing of TCP–PLGA microspheres.

Efficacy of ciprofloxacin-releasing bioabsorbable osteoconductive bone defect filler for treatment of experimental osteomyelitis due to Staphylococcus aureus

The concept of local antibiotic delivery via biodegradable bone defect fillers with multifunctional properties for the treatment of bone infections is highly appealing. Fillers can be used to obliterate surgical dead space and to provide targeted local bactericidal concentrations in tissue for extended periods. Eventually, the osteoconductive component of the filler could guide the healing of the bone defect. The present experimental study was carried out to test this concept in a localized Staphylococcus aureus osteomyelitis model in the rabbit (n = 31). A metaphyseal defect of the tibia was filled with a block of bone cement, followed by insertion of a bacterial inoculum. After removal of the bone cement and surgical debridement at 2 weeks, the defect was filled with a ciprofloxacin-containing (7.6% +/- 0.1%, by weight) composite (treated-infection group) or with a composite without antibiotic (sham-treated group). Both a positive control group (untreated-infection group) and a negative control group were also produced. The treatment response, monitored by positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose ([18F]FDG) at 3 and 6 weeks, showed rapidly decreasing amounts of [18F]FDG uptake in the treated-infection group (P = 0.001 compared with the results for the untreated-infection group at 6 weeks). The bacteriological analysis confirmed the eradication of the bone pathogen in the treated-infection group. However, three animals had culture-positive soft tissue infections. All animals in the sham-treated and untreated-infection groups had culture-positive bone infections with typical radiographic changes of osteomyelitis. Histomorphometry, peripheral quantitative computed tomography, and backscattered electron imaging of scanning electron microscopy images verified the osteoconductive properties of the bioactive glass microspheres within the composite. The median bone ciprofloxacin concentrations were 1.2 and 2.1 microg/g at two anatomic locations of the tibia. This is the first report to show the value of [18F]FDG PET for quantitative monitoring of the treatment response in bone infections. The collaborative results of bacteriologic and [18F-FDG] PET studies showed that use of the multifunctional composite was successful for eradication of the S. aureus pathogen from bone.

Gentamicin-loaded calcium carbonate materials: Comparison of two drug-loading modes

Synthetic aragonite-based porous materials were drug loaded with gentamicin sulphate, an antibiotic active on Staphylococcus aureus responsible for osteomyelitis. Drug loading was accomplished by two different ways: by integration of gentamicin in material during processing or by soaking material into gentamicin solutions. We first investigated the influence of drug loading on compressive strength of materials. Results indicate that soaked materials presented the same compressive strength than unloaded materials with the same porosity. By contrast, the integration of gentamicin during processing increased significantly the compressive strength of materials. The materials drug content before elution was a least 10 times higher when gentamicin was integrated during processing comparatively to soaked materials. The study of in vitro gentamicin release showed that for materials with gentamicin integrated during material processing, high concentrations of gentamicin were released up to 8 or 12 days, against 4 days for soaked materials. The transport coefficients calculation, for the first step of release, indicated that the rate of release was higher for materials with integrated gentamicin because of the higher gentamicin content. The porosity rate influenced the rate of release for materials positively with gentamicin integrated during processing contrary to soaked materials for which a higher porosity rate allowed a deeper penetration of gentamicin during drug loading and then a slightly slower release. Results indicate that aragonite-based material with gentamicin integrated during material processing may be used either as resorbable device for release of high concentrations of gentamicin or as biomaterial for combined therapy: bone substitution and prevention or treatment of osteomyelitis.

Evaluation of an in situ setting injectable calcium phosphate as a new carrier material for gentamicin in the treatment of chronic osteomyelitis: Studies in vitro and in vivo

A study was performed to investigate the effectiveness of hydroxyapatite cement (HAC) as a new carrier system in the treatment of chronic, posttraumatic osteomyelitis. In the in vitro study, release of gentamicin from standard cylinders of HAC were measured by agar diffusion test. As a representative for mechanical properties, compression strength was measured in order to detect changes when mixing HAC with gentamicin. In the in vivo study, bone infection was induced according to the model of Norden by injection of 1 ml Na-morrhuat and 3 x 10(6)CFU Staphylococcus aureus. After 3 weeks, when chronic stage of infection was obtained, 17 animals were treated by debridement and filling the marrow either with HAC alone or HAC mixed with gentamicin (32 mg/g). Animals of the control groups were left untreated. After 6 weeks, all animals were sacrificed. Hematological, radiological, microbiological and histological examinations were carried out by covered investigation. Best evidence of the efficiency of treatment was observed in histopathological and microbiological findings. In all swabs of the control groups, taken 6 weeks following infection S. aureus were detected which were clonal to the strain used for induction of osteomyelitis. In HAC/gentamicin-treated animals, no growth was detectable after 7 days of culturing in BHI bouillon. In the HAC/gentamicin-treated group, there was no histopathological evidence of infection. In all other groups different stages of chronic osteomyelitis were found. No side effect was observed, neither locally nor systemically by HAC or gentamicin. Therefore, HAC is considered to be a very effective carrier for antibiotics in treatment of chronic, posttraumatic osteomyelitis.

Inclusion of ibuprofen in mesoporous templated silica: drug loading and release property

The aim of this study is to determine the feasibility of loading biologically active molecules into templated mesoporous silica (MCM 41). This material shows an important mesoporosity associated to hexagonally organized channels, a narrow pore size distribution and a large surface area. Ibuprofen was selected as a model molecule since it is a well documented and much used anti-inflammatory drug. Furthermore, it has a lipophilic character and its molecular size is suitable for inclusion within the mesopores of the MCM 41 material. In order to load ibuprofen within the mesopores, adsorption experiments using various solvents or successive impregnations with solutions of ibuprofen in ethanol were performed. At each step of the loading process, the pore filling was characterized by nitrogen adsorption experiments and by X-ray diffraction. The impregnation procedure results in a significant improvement of the amount of ibuprofen loaded into MCM 41. The in vitro drug release was investigated with simulated biological fluids (gastric and intestinal). Hundred percent release is observed at the end of the in vitro experiment.

In vitro tobramycin elution analysis from a novel ?-tricalcium phosphate-silicate-xerogel biodegradable drug-delivery system

This in vitro research analyzed local tobramycin elution characteristics from a novel, biodegradable drug delivery system, consisting of a beta-TCP bone substitute, VITOSS trade mark, encapsulated with silicate xerogel prepared by the sol-gel process. Tobramycin elution from silicate-xerogel-encapsulated VITOSS was compared directly with non-silicate-xerogel-encapsulated VITOSS to assess whether xerogels are effective in delivering greater tobramycin quantities in a controllable, sustained manner crucial for microbial inhibition. Tobramycin elution characteristics indicate an initial release maximum during the first 24 h that diminishes gradually several days after impregnation. The copious tobramycin quantity eluted from the VITOSS/silicate-xerogel systems is attributed to various factors: the intrinsic ultraporosity and hydrophilicity of VITOSS, the ability of tobramycin to completely dissolve in aqueous media, tobramycin complexation with highly polar SO(4) (2-) salts that further assist dissolution, and ionic exchanges between VITOSS and the environment. Silicate-xerogel-encapsulated VITOSS eluted 60.65 and 61.31% of impregnated tobramycin, whereas non-silicate-xerogel-encapsulated VITOSS eluted approximately one-third less impregnated tobramycin, at 21.53 and 23.60%. These results suggest that silicate xerogel optimizes tobramycin elution because of its apparent biodegradability. This mechanism occurs through xerogel superficial acidic sites undergoing exchanges with various ions present in the leaching buffer. Tobramycin elution kinetics were evaluated, and demonstrate that first-order elution rate constants are considerably less when silicate xerogels are employed, following a more uniform exponential decay-type mechanism, thus bolstering controlled release. Overall, tobramycin elution rates adhere to linear-type Higuchi release profiles. Elution rate constants are initially first order, and taper into zero-order elution kinetics in the latter stages of release. Because VITOSS and silicate xerogel are completely biodegradable, essentially all impregnated tobramycin will be delivered to the surgical site after implantation.

A novel femoral intramedullary plug with sliding mechanism

A novel femoral intramedullary plug with a sliding mechanism has been developed and evaluated clinically. The new plug consists of a pair of specially designed components, each shaped like an obliquely cut cylinder. Postoperative plain radiographs of 30 arthroplasties using the plug were examined for cement leakage, plug migration, and radiolucent line formation between the cement and the femoral cortex. Plugging was complete in 22 cases. Leakage of the cement was seen in 4 cases, and migration of the plug was seen in the other 4 cases. Our study showed the efficacy of the plug in occluding the femoral canal completely in 14 of 22 cases. The plug appears to be promising for clinical applications, because it has good biocompatibility and can occlude the femoral canal tightly.

Mixture ratios of local bone to artificial bone in lumbar posterolateral fusion

There have been no reports on the effects of the mixture ratio of local bone graft to artificial bone on the outcome of intervertebral bone fusion. The purpose of this study was to determine whether the mixture ratio of local bone removed from laminae and spinous processes to apatite- and wollastonite-containing glass ceramic (AWGC) granules affected fusion rates in spinal fusion. Posterolateral lumbar fusion at two levels without spinal instrumentation was performed in 35 patients who were diagnosed with lumbar spinal canal stenosis. The patients were randomly divided into three groups, each of which received a different mixture ratio of local bone to AWGC granules: 2:1, 1:1, and 1:2. The total mass of grafted bone was 20 g in all three groups. The fusion rate was approximately 80% in all three groups. Our results indicate that lumbar posterolateral fusion can be successfully achieved even when the mixture ratio of local bone graft to AWGC granules is 1:2.

The Belfast technique for the treatment of chronic osteomyelitis in a tropical teaching hospital

From September 1995 to August 2001, we treated 25 patients with chronic osteomyelitis of long bones by a two-stage technique. This consisted of the radical removal of all infected bone and soft tissue and immediate provision of soft-tissue cover. This was supplemented when necessary with delayed autogenous bone grafting. The average follow-up was 46 months (range: 19-80 months). One patient with haemoglobin sickle cell disease (HbSS) died after the second stage of surgery. There were four recurrences, one of which followed a myocutaneous flap that became necrotic. Ankylosis occurred in five patients.

The use of an antibiotic-impregnated, osteoconductive, bioabsorbable bone substitute in the treatment of infected long bone defects: early results of a prospective trial

OBJECTIVE

We sought to evaluate the use of a bioabsorbable, tobramycin-impregnated bone graft substitute (calcium sulfate alpha-hemihydrate pellets) in the treatment of patients with infected bony defects and nonunions.

STUDY DESIGN/METHODS

Twenty-five patients (15 male and 10 female, mean age 43 years (range 27-69 years) requiring surgical debridement of culture-positive long bone infection (16 with associated nonunion) were entered into an ongoing consecutive, prospective clinical trial. Involved bones included the tibia ( 15), femur ( 6), ulna ( 3), and humerus ( 1). All defects were posttraumatic in origin, and each patient had had previous surgery at the involved site (mean 4.3 surgeries; range 1-8 surgeries). The duration of infection ranged from 4 months to 20 years (mean 43 months). According to the Cierny-Mader classification system, there was 1 stage I (medullary osteomyelitis), 6 stage III (localized osteomyelitis), and 18 stage IV (diffuse osteomyelitis) lesions. There were 4 normal (A) hosts and 21 locally and/or systemically compromised (B) hosts. Mean bone defect/void was 30.5 cm (range 3-192 cm ).

RESULTS

Mean follow-up was 28 months (range 20-38 months). Radiographically, pellets were resorbed at a mean of 2.7 months postoperatively. Infection was eradicated in 23 of 25 patients (92%). Isolated bony defects healed in all nine patients without further treatment. Fourteen of 16 patients with nonunion achieved union, although nine required autogenous bone grafting. Union was achieved in five of seven nonunion patients treated with bone graft substitute in isolation. Complications included refracture (three), recurrence of infection (two), persistent nonunion (two), and superficial wound necrosis (one). Eight patients developed sterile draining sinuses that healed upon radiographic resorption of the pellets.

CONCLUSIONS

In patients with posttraumatic osteomyelitis, the bone graft substitute was effective in eradicating bone infection in 23 of 25 patients. Isolated bony defects healed reliably (nine of nine) following addition of bone graft substitute alone. The role of the bone graft substitute in isolation in the treatment of nonunion is unclear at present.

Liberação In Vitro de Cloridrato de Ciprofloxacina em Compósitos Hidroxiapatita: Colágeno

Compósitos hidroxiapatita:colágeno (HA:col) foram preparados em diferentes proporções para determinar qual a melhor proporção para a incorporação de cloridrato de ciprofloxacina. Foi utilizado colágeno submetido a tratamento alcalino (24 e 48h) e a melhor proporção HA:col obtida foi de 10:1 (m/m), utilizada para incorporação e liberação de ciprofloxacina. Os experimentos de liberação in vitro foram realizados em tampão fosfato salino (PBS), pH 7,4, a 37ºC, mostrando uma liberação máxima em torno de 90% para HA:col 24h e 75% para HA:col 48h, após 10h de imersão. A liberação de ciprofloxacina dos compósitos é controlada pelos poros da matriz, pois segue o modelo de Higuchi. Os resultados indicam que os diferentes tempos de tratamento alcalino no colágeno afetam a liberação de antibiótico. Uma diferença na quantidade de cargas negativas nos colágenos de 24 e 48h provocaria uma diferente interação entre o compósito e o antibiótico.

Influence of isostatic compression on the stability of vancomycin loaded with a calcium phosphate-implantable drug delivery device

It is essential to prevent microbial infections after osteoarticular trauma or prosthesis implantation. As an alternative to antibiotic parenteral administration, antibiotic-loaded biomaterials allow high concentrations to be obtained in situ without systemic toxicity. Although the formulation of biphasic calcium-phosphate (BCP)-vancomycin granules by isostatic compression has recently been used to produce drug-delivery devices, the stability of vancomycin needs to be proven. In this study, vancomycin was associated with BCP powders by isostatic compression at 100, 140, or 200 MPa and then extracted or released by a rotating paddle system for 24 h. Vancomycin assays were performed by spectrophotometric and microbiological methods. The results show that all vancomycin associated with the material was recovered after extraction without degradation. Thus, vancomycin was not denaturated after application of 100, 140, or 200 MPa of isostatic compression. The results for vancomycin released from granules compressed at the three pressures were not significantly different (p =.01) whether assays were performed microbiologically or spectrophotometrically, indicating a good correlation between the two methods. This process involving high pressure appears to be a good means of developing drug delivery devices loaded with therapeutic agents without denaturating the components.

Carrier systems for the local delivery of antibiotics in bone infections

Carriers used for the local delivery of antibacterial agents may be classified as nonbiodegradable or biodegradable. A major representative of the former category are the polymethylmethacrylate (PMMA) beads often impregnated with gentamicin which have been commercially available for the last 2 decades. Examples of the latter category include the collagen-gentamicin sponge, apatite-wollastonite glass ceramic blocks, hydroxyapatite blocks, polylactide/polyglycolide implants and the polylactate polymers. All of the above systems release antibiotics at concentrations exceeding those of the minimum inhibitory concentrations (MICs) for the most common pathogens of chronic osteomyelitis without releasing any antibiotic in the systemic circulation and without producing adverse effects. The major disadvantage of the PMMA beads is the need for their surgical removal at the completion of antibiotic release, which usually takes place 4 weeks after their implantation. The biodegradable carriers do not require surgical removal, and of those listed, the collagen-gentamicin sponge has been applied successfully over the last decade for bone infections. Among the other biodegradable systems which are still in experimental stages, polylactate polymers carrying quinolones seem very promising, since they are characterised by prolonged duration of release at concentrations 100 to 1000 times the MICs of the causative bacteria implicated in bone infections; preliminary results have shown these carriers to be very effective in the management of experimental osteomyelitis caused by methicillin-resistant Staphylococcus aureus. Further development of such biodegradable systems will provide a novel approach in the future for the eradication of chronic osteomyelitis.

Isostatic compression, a new process for incorporating vancomycin into biphasic calcium phosphate: comparison with a classical method

Isostatic compression has rarely been used to load calcium-phosphate biomaterials with therapeutic agents. This report, concerning four processes associating vancomycin, compares isostatic compression with wet granulation, a classical method. In the wet granulation study, vancomycin was associated with biphasic calcium-phosphate (BCP) granules either by adsorption or incorporation with a new granulation. In the isostatic compression study, BCP powder was compressed at 100, 140 and 200 MPa. The blocks obtained were crushed and 200-500 microm, sieved; thus, the vancomycin solution was absorbed on these granules. Compaction of BCP and vancomycin powders gave, after crushing and sieving, granules loaded with vancomycin. In each study, 5% vancomycin was associated with BCP. Vancomycin release profiles were assessed by an in vitro culture chamber dissolution test. Physicochemical studies of BCP and vancomycin showed their structural integrity after isostatic compression. Isostatic compression prolonged vancomycin release time from 3 to 7 days and the release time became greater as isostatic pressure increased, probably because of the porosity decrease of the granules during compression.