Elution characteristics of gentamicin-PMMA beads after implantation in humans

Gentamicin-permeated cement to sustain mechanical support for the treatment of a chronic calcaneal abscess. A case report

INTRODUCTION AND IMPORTANCE

Chronic calcaneal osteomyelitis is a challenging condition associated with high relapse rates, requiring a multidisciplinary approach and various therapeutic options for effective management. We report a very rare case of a pyogenic osteomyelitis of the os calcis presented as a bone abscess.

CASE PRESENTATION

A diabetic male patient presented with chronic osteomyelitis of the calcaneus in the form of bone abscess with a cavity of 6*5 cm. After pus evacuation and debridement of the cavity, gentamycin-impregnated polymethylmethacrylate cement was used to locally assist in controlling the infection and to assure mechanical support. Antibiogram-based oral antibiotic was administrated for 6 weeks. At final follow-up, the patient could walk without any assistance and was able to raise his body on the operated heel, with no signs of infection.

CLINICAL DISCUSSION

This case illustrates successful conservative surgical treatment of calcaneal abscess using antibiotic-impregnated cement for mechanical support and local infection control.

CONCLUSION

Incorporating antibiotic-impregnated cement into conservative foot surgeries for deeply embedded calcaneal abscesses provides effective infection control, mechanical support, and functional preservation, leading to successful treatment outcomes.

Anti-Staphylococcal Activity of Ligilactobacillus animalis SWLA-1 and Its Supernatant against Multidrug-Resistant Staphylococcus pseudintermedius in Novel Rat Model of Acute Osteomyelitis

Osteomyelitis caused by staphylococcal infection is a serious complication of orthopedic surgery. Staphylococcus pseudintermedius is the main causative agent of osteomyelitis in veterinary medicine. Methicillin-resistant S. pseudintermedius (MRSP) has been reported in companion animals, especially dogs. Multidrug-resistant S. pseudintermedius is an emerging pathogen and has acquired antibiotic resistance against various commercial antimicrobial agents. New antimicrobial compounds are urgently needed to address antibiotic resistance, and the development of novel agents has become an international research hotspot in recent decades. Antimicrobial compounds derived from probiotics, such as bacteriocins, are promising alternatives to classical antibiotics. In this study, the antibacterial activities of Ligilactobacillus animalis SWLA-1 and its concentrated cell-free supernatant (CCFS) were evaluated in vitro and in vivo. The CCFS of this bacterium showed no toxicity against osteoblast and myoblast cells in vitro, while significantly inhibiting the multidrug-resistant S. pseudintermedius KUVM1701GC strain in a newly established rat model. The CCFS significantly inhibited multidrug-resistant staphylococci both in vitro and in vivo. This suggests that CCFS derived from L. animalis SWLA-1 has potential as an alternative to classic antibiotics for staphylococcal infections in dogs.

Bone Transport Through Induced Membrane Versus Conventional Bone Transport in Management of Infected Long-Bone Defects of Lower Limbs: A Randomized Controlled Trial

OBJECTIVES

To compare bone transport through induced membrane (BTM) and conventional bone transport (BT) regarding docking site union and infection recurrence in the management of infected long-bone defects.

DESIGN

Prospective, randomized, controlled study.

SETTING

Tertiary-level center.

PARTICIPANTS

Thirty patients with infected nonunited long-bone fractures of lower limbs were included.

INTERVENTION

Fifteen patients were treated by BTM in group A, and 15 patients were treated by BT in group B.

OUTCOME MEASUREMENTS

The outcome measures were external fixation time, external fixation index, and docking time. Bone and functional outcomes were evaluated by the Association for the Study and Application of the Method of Ilizarov scoring system. Postoperative complications were evaluated according to the Paley classification.

RESULTS

The mean docking time was significantly lower in the BTM group than in the BT group (3.6 ± 0.82 months vs. 4.8 ± 0.86 months, respectively; P value 0.001). Docking site nonunion and infection recurrence were significantly lower in the BTM group than in the BT group (0% vs. 40%; P value 0.02 and 0% vs. 33.3%; P value 0.04, respectively), with no significant difference in the external fixation index ( P value 0.08).

CONCLUSIONS

This is the first prospective, randomized, controlled study comparing BTM and BT techniques, showing that BTM had significantly faster docking site union, lower incidence of postoperative complications including docking site nonunion and infection recurrence rates, and lower number of additional procedures needed at the expense of 2-staged operation in comparison with BT.

LEVEL OF EVIDENCE

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

The effectiveness of antibiotic cement-coated nails in post-traumatic femoral and tibial osteomyelitis - comparative analysis of custom-made versus commercially available nails

Background: The first objective of this retrospective study was to assess infection control rates in patients with chronic post-traumatic osteomyelitis (CPTO) of the femur or tibia treated with antibiotic cement-coated nails. The second objective was to compare the efficacy of custom-made nails versus commercially available antibiotic-coated nails in terms of infection control and need for reoperation. Methods: We reviewed a consecutive series of CPTO patients treated with antibiotic-coated nails who had a minimum follow-up of 24 months. We recorded the characteristics of the initial injury, the type of nail used, cement–nail debonding, infecting microorganisms, operating time, infection control, need for reoperation, and failure rate. We performed a comparative analysis between nails manufactured in the operating room (i.e., custom-made) and those commercially available. Results: Thirty patients were included. The affected bones were the femur (n=15) and the tibia (n=15). Twenty-one of the 30 initial injuries were open fractures. Staphylococcus aureus was the most frequently isolated microorganism (50 %). Sixteen patients were treated with custom-made nails and 14 with commercially available antibiotic-coated nails. At the time of extraction, four out of five custom-made antibiotic-coated nails experienced cement–bone debonding. Commercial nails were associated with shorter operating times (p<0.0001). The overall infection control rate was 96.66 %. Eight (26.66 %) patients needed reoperation. There was one failure (3.33 %) in the group treated with custom-made antibiotic-coated nails. We did not find significant differences between nail types in terms of reoperation, infection control, and failure rate. Conclusions: The use of antibiotic cement-coated nails proved useful in CPTO treatment. Commercially available nails had significantly shorter operating times and did not present cement–bone debonding during removal. Our results seem to indicate that both nail types are similar in terms of infection control and reoperation rates.

Antibiotic coated hinged threaded rods in the treatment of infected nonunions and intramedullary long bone infections

INTRODUCTION

Local delivery of high dose antibiotics in the form of antibiotic impregnated polymethyl methacrylate (PMMA) cement beads or coated rods is commonly used in the management of long bone infections. The downsides of antibiotic cement beads for intramedullary long bone infections are associated with difficulty in removal from the medullary canal, bead breakage, and lack of stability. Antibiotic cement-coated smooth flexible guide wires, rods and nails can have complications such as delamination or debonding of the cement. In addition, the current techniques for cement rod insertion have a risk of iatrogenic joint contamination. To improve upon this technique and decrease potential complications, we propose the use of an antibiotic cement-coated hinged threaded rod as a temporary intramedullary spacer. This technique utilizes both an antegrade and retrograde insertion of the threaded rod into the medullary canal through the bony defect site with connection at the hinge to treat intramedullary long bone infections and infected nonunions.

MATERIAL AND METHODS

A total of 40 patients were included in the study. The details in making the cement rod were well documented. The shape of cement rod and the integrity of the cement at the time of rod insertion and rod removal were compared to identify any cement debonding or delamination. Potential postoperative complications including iatrogenic joint infection, displacement or breakage of the threaded cement rods, and fracture displacement were all carefully documented. The preliminary biological effect of the initial debridement and antibiotic cement rod placement was determined using the negative conversion rate of intraoperative cultures.

RESULTS

A single antibiotic coated threaded rod was inserted in 18 cases. Two separate antibiotic coated threaded rods were inserted and connected via hinge in 22 cases. There were zero cases of rod breakage and no secondary loss of reduction from antibiotic rod placement to the definitive staged operation. There were zero iatrogenic joint infections. There were zero cases of cement debonding or delamination from the rod. The conversion rate to a negative culture after initial debridement and antibiotic rod placement was 85% (34/40 cases).

CONCLUSIONS

The use of an antibiotic coated cement threaded rod with a hinge as an intramedullary spacer provides the benefits of local antibiotic delivery, offers improved construct stability, makes implant removal easier without delamination of the cement mantle, and utilizes the versatility of a hinge to prevent violation of native joints when treating infected nonunions and intramedullary long bone infections.

An Overview of the Percutaneous Antibiotic Delivery Technique for Osteomyelitis Treatment and a Case Study of Calcaneal Osteomyelitis

BACKGROUND

A percutaneous antibiotic delivery technique (PAD-T) used for the adjunctive management of osteomyelitis is presented.

METHODS

This surgical technique incorporates a calcium sulfate and hydroxyapatite (calcium phosphate) bone void filler acting as a carrier vehicle with either an antibiotic or an antifungal medicine, delivering this combination directly into the area of osteomyelitis.

RESULTS

The benefit of the PAD-T is reviewed with a case presentation of a successfully treated calcaneal osteomyelitis.

CONCLUSIONS

No previously reported PAD-T using a simple bone cortex incision in the adjunctive treatment of osteomyelitis has been reported. The PAD-T safely and effectively uses a calcium sulfate and hydroxyapatite bone void filler carrier vehicle to deliver either an antibiotic or an antifungal medicine directly into the area of osteomyelitis.

Nanoparticulate drug delivery platforms for advancing bone infection therapies

INTRODUCTION

The ongoing surge of resistance of bacterial pathogens to antibiotic therapies and the consistently aging median member of the human race signal an impending increase in the incidence of chronic bone infection. Nanotechnological platforms for local and sustained delivery of therapeutics hold the greatest potential for providing minimally invasive and maximally regenerative therapies for this rare but persistent condition.

AREAS COVERED

Shortcomings of the clinically available treatment options, including poly(methyl methacrylate) beads and calcium sulfate cements, are discussed and their transcending using calcium-phosphate/polymeric nanoparticulate composites is foreseen. Bone is a composite wherein the weakness of each component alone is compensated for by the strength of its complement and an ideal bone substitute should be fundamentally the same.

EXPERT OPINION

Discrepancy between in vitro and in vivo bioactivity assessments is highlighted, alongside the inherent imperfectness of the former. Challenges entailing the cross-disciplinary nature of engineering a new generation of drug delivery vehicles are delineated and it is concluded that the future for the nanoparticulate therapeutic carriers belongs to multifunctional, synergistic and theranostic composites capable of simultaneously targeting, monitoring and treating internal organismic disturbances in a smart, feedback fashion and in direct response to the demands of the local environment.

Gentamycin-impregnated calcium phosphate cement for calcaneal osteomyelitis: a case report

We report a case of chronic calcaneal osteomyelitis in a diabetic patient who was successfully treated with radical debridement and gentamycin-impregnated calcium phosphate cement. At 1.5-year follow-up, the patient could walk without any assistance. Calcium phosphate cement is an effective local antibiotic delivery system and a biocompatible material for filling the debrided space to facilitate bone formation.

Current therapies for diabetic foot infections and osteomyelitis

Treatment of the patient with a diabetic foot infection and underlying osteomyelitis is currently an evolving process, often complicated by neuropathy, peripheral vascular disease, and renal insufficiency. Understanding which patients require hospitalization, intravenous antibiotic therapy, and urgent operative intervention may ultimately prevent the spread of infection or major limb amputation. The treating surgeon should focus on accurate and early diagnosis, proper antibiosis, and appropriate surgical debridement to eradicate infection while preserving function with a plantar-grade foot.

Local application of free antibiotic powder in the treatment of osteomyelitis in a rat model

To date, several strategies have been developed to provide local antibiotic therapy in the treatment of osteomyelitis, such as antibiotic-loaded bone cement, antibiotic-impregnated collagen sponges, polymethylmethacrylate beads, antibiotic-loaded bone graft, antibiotic-loaded synthetic bone substitutes, and antibiotic-coated implants. The optimum carrier for local antibiotic therapy has not been identified. Tibial osteomyelitis using methicillin-sensitive Staphylococcus aureus was created in a rat model. Rats were assigned to 3 treatment groups: group A, systemic antibiotics only; group B, systemic antibiotics plus surgical debridement; and group C, systemic antibiotics, surgical debridement, and application of cefazolin. Infection was assessed using gross tissue analysis, radiographs, quantitative bacteriology, and histopathology. One-half of the rat tibias were randomly chosen for histological evaluation and the other half were used for microbiological analysis. Radiographs were reviewed and graded by 4 blinded board-certified radiologists. Histology slides were reviewed and graded by a blinded board-certified pathologist. Gross tissue analysis of treatment groups B and C demonstrated a statistically significant improvement in soft tissue infection clearance compared with group A (P<.05). No difference was found between treatment groups B and C. No significant difference existed in gross tissue, radiographic, microbiologic, or histopathologic analyses among the 3 groups for osteomyelitis. The results of this study demonstrated that the local application of free antibiotic powder is as effective as local debridement alone in treating soft tissue infection associated with tibial osteomyelitis in a rat model.

A new type of biphasic calcium phosphate cement as a gentamicin carrier for osteomyelitis

Osteomyelitis therapy is a long-term and inconvenient procedure for a patient. Antibiotic-loaded bone cements are both a complementary and alternative treatment option to intravenous antibiotic therapy for the treatment of osteomyelitis. In the current study, the biphasic calcium phosphate cement (CPC), called α-TCP/HAP (α-tricalcium phosphate/hydroxyapatite) biphasic cement, was prepared as an antibiotics carrier for osteomyelitis. The developed biphasic cement with a microstructure of α-TCP surrounding the HAP has a fast setting time which will fulfill the clinical demand. The X-ray diffraction and Fourier transform infrared spectrometry analyses showed the final phase to be HAP, the basic bone mineral, after setting for a period of time. Scanning electron microscopy revealed a porous structure with particle sizes of a few micrometers. The addition of gentamicin in α-TCP/HAP would delay the transition of α-TCP but would not change the final-phase HAP. The gentamicin-loaded α-TCP/HAP supplies high doses of the antibiotic during the initial 24 hours when they are soaked in phosphate buffer solution (PBS). Thereafter, a slower drug release is produced, supplying minimum inhibitory concentration until the end of the experiment (30 days). Studies of growth inhibition of Staphylococcus aureus and Pseudomonas aeruginosa in culture indicated that gentamicin released after 30 days from α-TCP/HAP biphasic cement retained antibacterial activity.

The successful use of vancomycin-impregnated cement beads in a patient with vancomycin systemic toxicity: a case report with review of literature

We report the use of vancomycin laden antibiotic cement beads in a patient with calcaneal osteomyelitis who had prior acute kidney injury (AKI). The patient experienced non-oliguric renal failure after exposure to intravenous vancomycin and recovered well after antibiotic discontinuation and adequate hydration. We are not aware of any similar case report where vancomycin laden antibiotic cement has been used in a patient with AKI to vancomycin.

Outcome in patients with an infected nonunion of the long bones treated with a reinforced antibiotic bone cement rod

OBJECTIVES

This study looks at the treatment of 16 cases of infection in long bone fractures that had an adverse effect on healing. The goal was to find a method that may be effective in getting these most difficult injuries to heal. The use of reinforced antibiotic-impregnated bone cement rods was studied to see if this could be an effective form of treatment. The use of such devices makes sense because they provide stability that the fractures need for healing while also providing a high concentration of antibiotics locally. The concept was to reduce the amount of metal used for stability while still giving the fracture the correct milieu for healing.

DESIGN

This was a retrospective analysis of 16 patients with infected nonunions of long bones. A protocol for the use of intravenous and per oral antibiotics was developed based on the type of bacteria found from cultures of the infected sites. All cases included operative débridement and stabilization with a reinforced antibiotic-impregnated bone cement rod.

PATIENTS

The patient population was selected from all those who presented to the Department of Orthopaedic Surgery of Dayanand Medical College & Hospital, Ludhiana, India.

MAIN OUTCOME

Success was considered when the nonunion healed and the limb became functional.

RESULTS

The infected nonunions were treated successfully in 14 of 16 cases. This represents an alternative to external fixation alone as a means of stabilizing nonunions while providing a high concentration of antibiotic locally for combating this most difficult problem.

CONCLUSIONS

The use of reinforced antibiotic-impregnated bone cement rods with appropriate surgical débridement and antibiotics may be an effective way of treating infected nonunions of long bones.

LEVEL OF EVIDENCE

Therapeutic Level IV. See page 128 for a complete description of levels of evidence.

Permanent antibiotic impregnated intramedullary nail in diabetic limb salvage: a case report and literature review

Managing complications after attempted hind foot and ankle arthrodesis with intramedullary nail fixation is a challenge. This situation becomes more problematic in the patient with diabetes mellitus and multiple comorbidities. Infection and subsequent osteomyelitis can be a devastating, limb threatening complication associated with these procedures. The surgeon must manage both the infectious process and the skeletal instability concurrently. This article provides a literature review and detailed management strategies for a modified technique of employing antibiotic impregnated polymethylmethacrylate-coated intramedullary nailing.

The role of polymethylmethacrylate antibiotic-loaded cement in addition to debridement for the treatment of soft tissue and osseous infections of the foot and ankle

Polymethylmethacrylate (PMMA) has been used in skeletal surgery for >40 years as a means of securing prosthetic implants and more recently was used as a delivery agent for local high-dose antibiotics to treat soft tissue and osseous infections. The purpose of this study was to determine the role of PMMA antibiotic-loaded cement (PMMA-ALC) in combination with aggressive debridement for the treatment of foot and ankle soft tissue and osseous infections requiring operative intervention. A retrospective observational cohort study of prospectively collected data was performed for all patients who underwent aggressive debridement with placement of PMMA-ALC for foot and ankle soft tissue and osseous infections between July 2006 and January 2009. There were 35 (29 men, 6 women) patients, 29 who had diabetes, with a mean age of 61 1 13 years (range, 16-86 years). A total of 36 feet/ankles (20 right, 16 left) were involved, and the infections were anatomically divided into 6 groups: (1) toes (n = 9), (2) metatarsalphalangeal joints (MTPJ) (first MTPJ, n = 5; fifth MTPJ, n = 5), (3) forefoot (n = 11), (4) rearfoot (n = 4), and (6) ankle/lower leg (n = 3). All patients had confirmed bacterial infection via microbiologic or pathologic analysis before PMMA-ALC insertion. A total of 73 cultures were obtained at the time of PMMA-ALC removal, with 66 showing no bacterial growth (90.4%) and 7 positive for bacterial growth (9.6%). Methicillin-resistant Staphylococcus aureus was the most commonly cultured organism both preoperatively and postoperatively. When combined with aggressive irrigation and debridement, the use of PMMA-ALC appears to be a beneficial adjunctive therapy for the treatment of foot and ankle soft tissue and osseous infections.

Infected nonunions of long bones of the upper extremity: staged reconstruction using polymethylmethacrylate and bone graft impregnated with antibiotics

This case series evaluates 12 patients presenting posttraumatic infected nonunions affecting long bones of the upper extremity, treated with staged reconstruction using polymethylmethacrylate spacers with antibiotics in the first stage and bone graft impregnated with antibiotics in the definitive surgical procedure. Five nonunions affected the humerus, four the ulna and three the radius. All nonunions were atrophic. Patient's age averaged 35.9 years. The size of the bony defect averaged 2.8 cm. Time between original trauma and revision surgery averaged 9.6 months. Follow-up averaged 19 months. All nonunions healed after an average of 5 months. DASH score at last follow-up averaged 15 points. Although two surgical procedures are needed, one to cure infection and another to achieve bony union, this approach for posttraumatic infected nonunions of long bones of the upper extremities represents a valid treatment alternative.

Elution of gentamicin and vancomycin from polymethylmethacrylate beads and hip spacers in vivo

BACKGROUND AND PURPOSE

Late infections after total hip arthroplasty are still a problem. Treatment procedures include resection arthroplasty with implantation of antibiotic-loaded beads or implantation of an antibiotic-impreganted spacer. However, little is known about antibiotic elution from bone cement beyond the first 2-3 postoperative days in humans.

METHODS

17 hip spacers (80 g PMMA, 1g gentamicin, and 4 g vancomycin) and 11 chains (40 g PMMA, 0.5 g gentamicin, and 2 g vancomycin) in 28 patients were studied. The release of both agents was measured in the drainage fluid on a daily basis. The drains were left in situ until less than 50 mL was produced per day. The elution of both antibiotics was determined by fluorescence polarization immunoassay. Systemic antibiotics were given postoperatively according to antibiogram. If possible, no gentamicin or vancomycin was given.

RESULTS

Peak mean concentrations from beads and spacers were reached for gentamicin (1,160 (12-371) microg/mL and 21 (0.7-39) microg/mL, respectively) and for vancomycin (80 (21-198) microg/mL and 37 (3.3-72) microg/mL) on day 1. The last concentrations to be determined were 3.7 microg/mL gentamicin and 23 microg/mL vancomycin in the beads group after 13 days, and 1.9 microg/mL gentamicin and 6.6 microg/mL vancomycin in the spacer group after 7 days. Between the fifth and seventh day, an intermittent increase in elution of vancomycin from both beads and spacers and of gentamicin from spacers was noticed. No renal or hepatic dysfunction was observed.

INTERPRETATION

Beads showed higher elution characteristics in vivo than the spacers due to their larger surface area; however, a great amount of inter-subject variability was seen for both beads and spacers. The inferior elution properties of spacers emphasize the importance of additional systemic antibiotics for this treatment procedure during the postoperative period. Future studies should clarify whether the dose of antibiotics or length of antibiotic therapy may be reduced in the case of bead implantation, without jeopardizing the control of infection.

Use of antibiotic cement rod to treat intramedullary infection after nailing: preliminary study in 19 patients

The treatment of intramedullary infections after nailing usually includes removal of the nail, debridement, and, in some cases, insertion of antibiotic-impregnated cement beads. We use this self-made antibiotic cement rod to treat intramedullary infections. Compared with the beads, it provides some limited mechanical support and can be preserved in the canal for a long time. We reviewed 19 infected patients who underwent removal of the nails, excision of sinus tracks, debridement of the canal and insertion of the rods. No recurrent infection occurred in 18 cases and 11 cases achieved bone healing, 6 cases achieved partial union. One patient had nonunion and one patient underwent amputation because of severe primary trauma and long-term infection. The rod was removed between 35 and 123 days after implantation. We conclude that the antibiotic cement rods could be a relatively effective, simple and inexpensive method of treating intramedullary infections after nailing.

Does antibiotic elution from PMMA beads deteriorate after 1-year shelf storage?

Antibiotic-impregnated polymethylmethacrylate beads are widely used as an adjunct in the treatment of orthopaedic infections. Because there is no commercially available bead in the United States, surgeons must manufacture bead sets at the time of implantation. This can be time consuming and wasteful. We hypothesized antibiotic-impregnated beads would maintain consistent elution for up to 1 year after manufacturing and storage. Tobramycin-impregnated antibiotic beads were manufactured using a bead mold. The antibiotic was either hand-mixed into the polymethylmethacrylate powder (1.2 g/40 g) or came premixed from the factory (1 g/40 g). Packages of beads were gas-sterilized and stored at room temperature. Beads were tested at 0, 1, 2, 3, 6, and 12 months. Antibiotic levels in the eluent from each day of the month were measured. We were unable to detect any difference in the amount of antibiotic elution between beads tested immediately after manufacture and beads manufactured and stored for 6 or 12 months. Beads with hand-mixed antibiotics eluted higher levels of antibiotics than the beads prepared with factory-mixed antibiotics. We conclude antibiotic beads can be made, sterilized, and used after 1 year of storage with no deleterious effect on antibiotic elution characteristics.

Calcium sulphate delivery system with tobramycin for the treatment of chronic calcaneal osteomyelitis

The case of a 24-year-old woman with Pseudomonas aeruginosa and Proteus mirabilis chronic calcaneal osteomyelitis is presented. Extensive debridement of the necrotic bone and application of tobramycin-loaded polymethylmethacrylate beads was performed and ciprofloxacin was given post-operatively. Three months later, laboratory tests, including complete blood cell count, erythrocyte sedimentation rate and C-reactive protein, were normal. At this time, extensive surgical debridement and filling of the osseous defect with autologous iliac cancellous bone graft and tobramycin-impregnated calcium sulphate pellets and paste were performed. Oral ciprofloxacin was administered for 3 months after surgery. At the latest follow-up, 2 years later, the patient had full weight-bearing function; there was no recurrence of the infection, and complete incorporation of the autologous bone and calcium sulphate graft with the host bone was observed. This case demonstrates that two-stage surgical treatment with extensive debridement and tobramycin-impregnated calcium sulphate was effective in treating chronic calcaneal osteomyelitis.

Prophylaxis and treatment of implant-related infections by antibiotic-coated implants: a review

Implant-related infection is a feared complication in orthopedic and trauma surgery with tremendous consequences for the patient. To reduce this risk, administration of perioperative antibiotic prophylaxis is a routine procedure in orthopedic surgery. A local delivery system for antibiotics based on a polymer implant coating has been developed to optimize the prophylaxis. In an animal experiment, the efficacy of local prophylaxis of gentamicin was compared to a systemic single shot of gentamicin and to a combination of both administrations. The medullary cavities of rat tibiae were contaminated with Staphylococcus aureus and titanium K-wires were implanted into the medullary canals. For local antibiotic therapy, the implants were coated with poly(D,L-Lactide) (PDLLA) loaded with gentamicin. All the animals not treated with local and systemic application of the antibiotic developed osteomyelitis and all cultures of the implants tested positive for S. aureus. Onset of infection was prevented in 80-90% of animals treated with gentamicin-coated K-wires, with and without systemic prophylaxis. Gentamicin-coated intramedullary tibial nails are CE-certified for Europe and Canada and several patients have already been treated for implant-related infection. Up to now, eight patients with open tibia fractures have been treated with an unreamed tibial nail (UTN) coated with PDLLA and gentamicin. In the 1-year follow up, none of the patients developed an infection. A prospective randomized clinical documentation is currently in progress. So far, the results suggest that a local application of gentamicin from PDLLA-coated implants might support systemic antibiotic prophylaxis in preventing implant-associated osteomyelitis.

Effectiveness of hydroxyapatite-vancomycin bone cement in the treatment of Staphylococcus aureus induced chronic osteomyelitis

In the field of local application of antimicrobials, a number of novel drugs and/or new drug delivery systems have been developed in recent years. The present study aimed to investigate hydroxyapatite cement (HAC) as a carrier for vancomycin in the treatment of chronic osteomyelitis due to Staphylococcus aureus strains with various mechanisms of resistance. The release of vancomycin from standard test cylinders was determined in vitro and the efficacy of the delivery system was measured in vivo using a rabbit model of chronic osteomyelitis. First, powdered HAC was mixed with vancomycin at 80, 160 and 240 mg/g. After hardening, formed cylinders were eluted in phosphate buffer and antibiotic release was measured by agar diffusion. High levels of release (1512+/-318 to 1937+/-336 microg/ml) were obtained for 12 to 20 days depending on the dosage of vancomycin. Additionally, bone infection was induced in the tibia of 30 New Zealand white rabbits by injecting either a methicillin-resistant S. aureus strain (MRSA) or a S. aureus strain with a small colony variant (SCV) phenotype. After 3 weeks (chronic infection), all animals were treated by debridement. Moreover, group 1 (challenged with SCVs) and group 2 (challenged with MRSA) were treated by filling the marrow with HAC alone, whereas in groups 3 (SCVs) and 4 (MRSA) the marrow was filled with HAC/vancomycin (160 mg/g). After 6 weeks all animals were sacrificed. At 3 weeks, pathogens were detected in 24 of 30 animals. All swabs of the control groups, positive for S. aureus on day 21, were also positive on day 42 and S. aureus strains recovered were shown to be clonal to the strains used for induction of osteomyelitis. By contrast, no growth was found in the treatment group following 7 days of incubation in BHI bouillon. HAC/vancomycin-treated animals showed no histological evidence of infection on day 42. In the other groups, different stages of chronic osteomyelitis were found histologically. No local or systemic side effects due to HAC or vancomycin were seen. HAC is an effective carrier material for antibiotic compounds even in refractory infections due to MRSA or S. aureus SCVs.

Local and systemic levels of tobramycin delivered from calcium sulfate bone graft substitute pellets

We asked if tobramycin-loaded calcium sulfate pellets could be used to maintain high local site antibiotic concentrations for an extended period with minimal systemic levels and without adverse effects on vital organs. Calcium sulfate pellets loaded with 10% tobramycin were implanted in contained medullary defects in the proximal humeri of canines. The number of pellets implanted was calculated to yield an equivalent human maximum prescribed dose, and 1.8-fold this dose. These doses converted to approximately 20 mg/kg, and 36 mg/kg, respectively, for the canine. Local and systemic tobramycin levels, pellet resorption, bone response, clinical pathology parameters, and histopathologic responses of potential target organs were analyzed to determine if there was any adverse response for a 28-day period. Serum tobramycin was elevated for less than one day while local levels remained elevated for at least 14 days, and in some animals, 28 days. Tobramycin delivered locally from calcium sulfate pellets had no apparent adverse effect on clinical pathology parameters or on any of the organs that were analyzed. In addition, bone formation and pellet resorption followed patterns typically seen with calcium sulfate materials.

Nanoporous delivery system to treat osteomyelitis and regenerate bone: Gentamicin release kinetics and bactericidal effect

Conventional treatment of osteomyelitis involves the repeated surgical removal of dead bone tissue coupled with repeated irrigation of the wound and prolonged systemic administration of antibiotics. Therapy of bone infections could easily last the rest of the patient's life because of the poor accessibility of the infection site by common systemically administered antibiotics. The objective of the present study is to develop a novel bone bioactive resorbable nanocomposite that can serve as a delivery system for antibiotics. We synthesized three different samples of porous bioactive resorbable silica-calcium phosphate nanocomposite (C3S1, C1S1, and C1S3) that has the ability to provide a sustained release of effective dose of gentamicin for 28 days. Porosity measurements showed that the average pore diameter of C3S1, C1S1, and C1S3 samples is 44.8, 54.4, and 70.9 nm, respectively. Moreover, the silica-rich composite (C1S3) is characterized by a significantly higher surface area (155.8 m(2)/g) than the silica-poor samples (C3S1) (42.9 m(2)/g). For all samples, the release profile study showed initial burst release followed by a sustained release of gentamicin. The released gentamicin has a strong inhibitory effect on Staphylococcus aureus bacteria. In addition FTIR analysis showed the formation of a biological apatite layer on the material surface after 24 h of immersion in simulated body fluid. Results of the study suggest that the silica-calcium phosphate nanocomposite can serve as a delivery vehicle for gentamicin to treat osteomyelitis and regenerate bone.

An articulated antibiotic spacer used for infected total knee arthroplasty: a comparative in vitro elution study of Simplex and Palacos bone cements

For the staged management of infected total knee arthroplasty (TKA), antibiotic laden polymethylmethacrylate (PMMA) spacers have been recommended. Antibiotic-impregnated PMMA spacers target drug delivery, achieving high local levels while limiting the potential for host toxicity associated with parenteral antimicrobial therapy. This study examined the elution characteristics of an articulating PMMA TKA spacer that has been useful clinically. Tobramycin and vancomycin are both active against many organisms leading to joint infections. We used various combined antibiotic concentrations (maintaining a relative ratio of 55% tobramycin to 45% vancomycin w/w), and then assayed the elution profile of the TKA spacer in vitro. Additionally, the elution qualities of two brands of bone cement, Simplex and Palacos, were compared. Briefly, three groups of PMMA spacers, impregnated with different antibiotic loads, were fashioned from a mold replicating a femoral TKA component. The entire spacer surface area was immersed in sterile phosphate buffered saline (PBS) in a 1:6 ratio of grams of cement to milliliters of PBS and incubated at 37 degrees C for 24 h. After 24 h, aliquot eluates were taken, the PBS discarded, and replaced with fresh, sterile PBS. PBS was changed daily and an aliquot was taken at least weekly for nine weeks. Eluate samples were stored at -70 degrees C until assayed. Each spacer eluate sample's antibiotic concentration was determined by disc diffusion bioassay against Bacillus subtilis. Mean zone inhibition diameters were extrapolated from the standard curve to yield micrograms per milliliter of antibiotic in PBS. In all groups the Palacos spacers demonstrated higher elution levels, above the MIC for the organism used, for a longer period of time than those made with Simplex. Based on the observed elution profiles, antibiotic-impregnated Palacos bone cement may offer a more effective vehicle for local drug delivery during staged treatment of infected TKA.

Local antibiotic therapy in the treatment of open fractures and osteomyelitis

Local antibiotic therapy is part of the treatment protocol of open fractures and osteomyelitis. However, there are limitations in the literature evaluating the efficacy of the technique and controversies remain. Polymethylmethacrylate cement commonly is used as a delivery vehicle, but bioabsorbable vehicles are being investigated. The vehicle is impregnated with antibiotic(s) active against the suspected pathogens, usually an aminoglycoside and/or vancomycin. Elution depends on the surface area, the characteristics and permeability of the delivery vehicle, type and concentration of the antibiotic(s) used, presence of fluid, rate of fluid turnover, and time postimplantation. Local antibiotic therapy is a safe technique resulting in high local concentration of antibiotics with minimal systemic levels. Local antibiotics effectively have controlled infection in animal models and, despite limitations of the existing literature, seem to be useful in the clinical setting. The length of implantation and the need for removal of the delivery vehicle remain controversial. Nonabsorbable vehicles may eliminate the need for reoperation and removal.

Gentamicin coating of metallic implants reduces implant-related osteomyelitis in rats

Antibiotic prophylaxis is a routine procedure in orthopedic surgery. Various local antibiotic delivery techniques are used to reduce bone- and soft tissue-related infection. The objective of this study was to evaluate the efficacy of a new biodegradable, gentamicin-loaded poly(D,L-lactide) (PDLLA) coating of orthopedic devices in preventing implant-related osteomyelitis. The medullary cavities of tibiae in 30 Sprague Dawley rats were contaminated with Staphylococcus aureus (10(3) colony forming units). Simultaneously titanium Kirschner wires, uncoated (group II), coated with PDLLA (group III), or coated with PDLLA + 10% gentamicin (group IV), were implanted. Ten animals that received phosphate-buffered saline and uncoated Kirschner wires served as controls (group I). Follow-up was 6 weeks. In weekly intervals X-rays of the tibiae were performed, blood counts were taken, and body temperature and weight were determined. After sacrifice infection was evaluated by histological and microbiological analysis. All animals of groups II and III developed microbiological, histological, and radiological signs of infection, including osseous destruction and soft tissue swelling. All animals of the control group remained sterile. Cultures of implants of group IV showed significantly reduced bacterial growth compared to cultures of groups II and III, and three implants of group IV remained sterile. Further radiological and histological signs of infection were significantly reduced in the gentamicin-coated group compared to groups II and III. No significant differences in body weight, body temperature, and blood parameters between all groups were observed. Local application of antibiotic-coated orthopedic devices containing PDLLA and 10% gentamicin significantly reduced implant-related infection in this animal model.

Residual gentamicin-release from antibiotic-loaded polymethylmethacrylate beads after 5 years of implantation

In infected joint arthroplasty, high local levels of antibiotics are achieved through temporary implantation of non-biodegradable gentamicin-loaded polymethylmethacrylate beads. Despite their antibiotic release, these beads act as a biomaterial surface to which bacteria preferentially adhere, grow and potentially develop antibiotic resistance. In routine clinical practice, these beads are removed after 14 days, but for a variety of reasons, we were confronted with a patient in which these beads were left in situ for 5 years. Retrieval of gentamicin-loaded beads from this patient constituted an exceptional case to study the effects of long-term implantation on potentially colonizing microflora and gentamicin release. Gentamicin-release test revealed residual antibiotic release after being 5 years in situ and extensive microbiological sampling resulted in recovery of a gentamicin-resistant staphylococcal strain from the bead surface. This case emphasizes the importance of developing biodegradable antibiotic-loaded beads as an antibiotic delivery system.

The science of bone cement: a historical review

The use of PMMA bone cement has been a key factor in the advent of joint replacement as a surgical option. Despite revolutionary changes in joint replacement technology for the treatment of hip and knee arthritis, the use of PMMA bone cement in its intraoperative application has not significantly changed since Harris' description of third generation cement technique. Future answers to questions regarding cemented implant longevity may lie in the further improvement of existing PMMA technology and standardization of the manufacturing of PMMA bone cement intraoperatively.

Intramedullary infections treated with antibiotic cement rods: preliminary results in nine cases

The treatment of intramedullary infections after nailing usually includes removal of the rod, debridement of the canal, and, in many cases, insertion of antibiotic-impregnated cement beads. These beads offer no mechanical support and are difficult to remove if left in place for more than 2 weeks. We present an alternative for filling the medullary canal's noncollapsible dead space with an antibiotic-impregnated cement rod. This rod can be custom-made at the time of surgery, using different diameter chest tubes as molds and embedding a 3-mm beaded guidewire within the cement. The smooth molded surface of this nail makes extraction of the cement rod relatively easy. The cement rod also provides some limited temporary support to the fracture or nonunion site while the infection is being treated. After 6 weeks, the rod can be removed and replaced with a definitive metal intramedullary nail, with or without bone grafting to treat the previously infected fracture or nonunion site. We retrospectively reviewed nine cases of intramedullary infection treated with antibiotic-impregnated molded cement rods. These included six femora, two tibiae, and one humerus. The cause of infection was lengthening or transport over nail in six cases, fixator-augmented nailing of osteotomies in two, and fracture fixation in one. The follow-up period after surgery ranged from 38 to 48 months. No recurrent infection occurred during this follow-up period, and no patient required antibiotics after the rod was removed. In all cases, the canal cultures were negative after rod removal. The cement rod was removed between 29 and 753 days after implantation. Fracture of the rod occurred in one case in which the rod was left in place for more than 1 year. We conclude that this method is a relatively simple and inexpensive alternative for the treatment of intramedullary infections.

The treatment of experimental osteomyelitis by surgical debridement and the implantation of calcium sulfate tobramycin pellets

Calcium sulfate was used as a biodegradable delivery system for the administration of antibiotics in musculoskeletal infection. New Zealand white rabbits were infected with Staplylococcus aureus, debrided, and randomized to one of four treatment groups: calcium sulfate pellets with 10% tobramycin sulfate, placebo calcium sulfate pellets and IM tobramycin, placebo calcium sulfate pellets, or debridement. Serum and wound exudate tobramycin concentrations and serum calcium levels were measured. Radiographs, cultures, and histology were analyzed for efficacy and treatment. Rabbits treated with 10% tobramycin sulfate pellets showed a significantly higher eradication of infection (11/13) than rabbits treated with debridement only (5/12), placebo pellets and IM tobramycin (5/14). or placebo pellets (3/13). In the group receiving 10% tobramycin sulfate pellets, serum tobramycin concentrations peaked 3 h post-operatively at 5.87 microg/ml and were non-detectable after day 1. In the group receiving placebo pellets and IM tobramycin, serum concentrations peaked at 7.82 microg/ml 1 h post-operatively, fell to 6.12 microg/ml on day 2, and averaged 4.18 microg/ ml for the remainder of the treatment period. The wound exudate tobramycin concentrations in the animals treated with tobramycin sulfate pellets peaked at 11.9 mg/ml on day 1 and dropped to 2.5 microg/ml on day 7. There was no significant difference in the serum calcium levels in any of the treatment groups. Calcium sulfate containing tobramycin sulfate has potential utility as a biodegradable local antibiotic delivery system in the treatment of musculoskeletal infections.

The treatment of chronic osteomyelitis with a biodegradable antibiotic-impregnated implant

The use of local antibiotics from a biodegradable implant for chronic osteomyelitis is an attractive alternative. The implant delivers high tissue levels, obliterates dead space, aids bone repair and does not need to be removed. The purpose of this paper is to review our early clinical experience with custom-made calcium sulfate (Osteoset bone void filler) antibiotic-impregnated implants.

Antibiotic beads in the treatment of diabetic pedal osteomyelitis

Antibiotic-impregnated polymethylmethacrylate (PMMA) beads have improved the outcome of osteomyelitis treatment in both experimental models and clinical trials. The primary benefit of antibiotic-impregnated PMMA beads is that they provide high local concentrations of antibiotic while systemic levels of antibiotic remain low. Little has been written about the specific use of antibiotic-impregnated PMMA beads in the treatment of diabetic pedal osteomyelitis. The authors review antibiotic-impregnated PMMA beads and provide examples of their use in the treatment of diabetic pedal osteomyelitis.

Use of a tobramycin-impregnated polymethylmethacrylate pin sleeve for the prevention of pin-tract infection in goats

OBJECTIVE

To test the hypothesis that antibiotic-laden polymethylmethacrylate (PMMA) pin sleeves prevent infection around skeletal external fixation pins.

DESIGN

An experimental study using an animal model was conducted.

ANIMALS

In each of five goats, three four-millimeter half-pins were placed in the left and right iliac crests, for a total of thirty half-pins. The pins were infected with one milliliter of broth containing 7.6 x 10(5) colony-forming units per milliliter of Staphylococcus aureus (ATCC 25923).

INTERVENTION

The pins in the right iliac crest were treated with the tobramycin-impregnated pin sleeves, and the pins in the left iliac crest (control) were left untreated.

RESULTS

The results showed clinical evidence of infection (i.e., looseness and gross pus) and heavy bacterial growth (average 6.8 x 10(10) colony-forming units per milliliter) for the untreated pins, but no clinical evidence of infection and no bacterial growth at forty-eight hours for the treated pins.

CONCLUSION

The present results indicate that the use of the antibiotic-impregnated PMMA pin sleeve can prevent the development of pin-tract infection and appears to prevent colonization of the external fixation pins.

A new drug delivery system with controlled release of antibiotic only in the presence of infection

An ideal drug delivery system (DDS) releases an appropriate drug at specific locations and times. We tried to create a new antibiotic delivery system that releases gentamicin only when wounds are infected by Pseudomonas aeruginosa (P.A.). Exudate from the dorsal pouch of rats infected with P.A. showed significantly higher hydrolytic activity-thrombin-like activity-toward Boc-Val-Pro-Arg-MCA than exudate from noninfected wounds. We therefore constructed a device for controlled release of an antimicrobial drug triggered by thrombin-like activity. Briefly, gentamicin was bound to a polyvinyl alcohol derivative (PVA) hydrogel through a newly developed peptide linker cleavable by the proteinase, PVA-(linker)-gentamicin. In vitro experiments showed that proteinases from wounds infected with P.A. cleaved the linker and gentamicin was released while the exudate from noninfected wounds had no hydrolytic activity toward the linker. This device shows potential as an occlusive dressing with an effective antibiotic delivery system for treating infected wounds.

Preparation and in vitro characterization of gentamycin-impregnated biodegradable beads suitable for treatment of osteomyelitis

A new method for preparing poly(L-lactide) (PLA) biodegradable beads impregnated with an ionic aminoglycoside, gentamycin, is described. The process employs hydrophobic ion pairing to solubilize gentamycin in a solvent compatible with PLA, followed by precipitation with a compressed antisolvent (supercritical carbon dioxide). The resulting precipitate is a homogeneous dispersion of the ion-paired drug in PLA microspheres. The microspheres are approximately 1 microm in diameter and can be compressed into beads (3-6 mm in diameter) strung on surgical sutures for implantation. The bead strings exhibit no significant change in release kinetics upon sterilization with a hydrogen peroxide plasma (Ster-Rad). The kinetics of gentamycin release from the PLA beads are consistent with a matrix-controlled diffusion mechanism. While nonbiodegradable poly(methyl methacrylate) (PMMA) beads initially release gentamycin in a similar manner, the drug release from PMMA ceases after 8 or 9 weeks, while the PLA beads continue to release drug for over 4 months. Moreover, only 10% of the gentamycin is released from the PMMA beads, while PLA beads release more than 60% of their load, if serum is present in the release medium. The PLA system displays improved release kinetics relative to PMMA, is biodegradable, is unaltered by gas sterilization, can be used for a range of antibiotics, and can be manipulated without disintegration. These are all desirable properties for an implantable drug delivery system for the prevention or treatment of osteomyelitis.

Staged management of infected humeral nonunion

Fourteen patients with infected humeral nonunion complicated by sinus discharge were treated with a staged protocol consisting of (1) radical debridement with local antibiotic beads implantation, and (2) external skeletal fixation with autologous bone grafting. In the first stage, a thorough debridement and sequestrectomy were done. Antibiotic beads were used to obliterate the bone defect, and the wound was then directly closed. In the second stage, the bead chains were replaced with autogenous cancellous bone graft. Unilateral Hoffman external skeletal fixators were applied simultaneously. The mean follow-up period was 73.6 months (range, 29 months to 9 years). The length of time to achieve bony union ranged from 3.5 to 8 months (average, 4.3 months). Hoffman pin complication was found in two cases, which were then shifted to plate internal fixation. All the infections were eradicated, and the wounds healed without further skin graft or flap coverage. All the fractures achieved bony union except for one in a patient who died. Most patients acquired satisfactory function of elbow motion after removal of external fixation and physical therapy. The method of two-stage management was effective for infected humeral nonunion. Not only was the infection eradicated and osseous union achieved, but also the limb function and joint motion were preserved.

Treatment of experimental osteomyelitis by surgical debridement and the implantation of bioerodable, polyanhydride-gentamicin beads

Osteomyelitis was induced in the radius in 77 rabbits and confirmed by histological examination and culture. At 4 weeks, the wounds were debrided and the animals were treated with (a) fatty acid dimer-sebacic acid beads (a bioerodable composite) impregnated with 20% or (b) 10% gentamicin sulfate, (c) placebo beads and intramuscular gentamicin sulfate, (d) placebo beads alone, or (e) debridement only. After 4 weeks, eradication of infection was determined by histological examination and culture. Osteomyelitis was eradicated in 93% of the animals treated with the beads and 20% gentamicin, in 67% of those treated with the beads and 10% gentamicin, in 25% of those treated with placebo beads and intramuscular gentamicin, in 7% of those treated with placebo beads alone, and in 12.5% of those treated with debridement only (p values from < 0.001 to 0.02). Fatty acid dimer-sebacic acid beads with gentamicin were then implanted in noninfected rabbits, and gentamicin sulfate concentrations in bone, serum, urine, and wound exudate were measured. Gentamicin sulfate was detectable in bone for as long as 8 weeks after implantation. Levels as high as 4,746 micrograms/ml were present in the wound exudate for the first 7 days. Levels in the serum peaked at 1.03 micrograms/ml. Urine levels peaked at 135 micrograms/ml.

Controlled release of antibiotics from coated orthopedic implants

Chronic osteomyelitis is one of the most serious complications of orthopedic open fracture treatment. The objective of this study was to develop a biodegradable implant coating with impregnated antibiotics as an adjunct to current therapy. We used a polylactic-co-glycolic acid copolymer (PLGA) as the biodegradable carrier and gentamicin as the antibiotic. Our objectives were to establish elution characteristics of the antibiotic from the polymer, and determine if the coated orthopedic implants would inhibit bacterial growth in vitro. In the elution study, coated implants were incubated in phosphate buffered saline (PBS) at 37 degrees C and sampled daily for gentamicin levels. The in vitro model consisted of test tubes containing Mueller-Hinton culture broth inoculated with 5 x 10(6) cfu of Staphylococcus aureus and incubated at 37 degrees C. The implants were switched to a new set of inoculated tubes each day. Tubes were sampled for colony counting to determine bactericidal effects. Implant coatings consisted of 40 mg of gentamicin as a 20% mixture with PLGA. The elution curve showed an average level of 138 micrograms/mL over 15 days. This local concentration would be more than adequate to kill susceptible organisms. The in vitro study showed a significant reduction in bacterial growth in the test tubes containing coated implants. Control tubes averaged 2.5 x 10(8) cfu/mL of S.aureus over 24 days. Coated implant tubes averaged 0.9 cfu/mL. This was a reduction of greater than 99.999% (p < 0.0001). This study showed that a thin biodegradable implant coating can be developed with bactericidal activity against the organisms frequently associated with osteomyelitis in cases of open fractures.