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Since low-dose antibiotic-loaded bone cement (ALBC) was approved by the FDA for second-stage reimplantation after infected arthroplasties in 2003, commercially premixed low-dose ALBC has become available in the United States. However, surgeons continue to mix ALBC by hand. We presumed hand-mixed ALBC was not as homogeneous as commercially premixed ALBC. We assessed homogeneity by determining the variation in antibiotic elution by location in a batch, from premixed and hand-mixed formulations of low-dose ALBC. Four hand-mixed methodologies were used: (1) suspension--antibiotic powder in the liquid monomer; (2) no-mix--antibiotic powder added but not mixed with the polymer powder before adding monomer; (3) hand-stirred--antibiotic powder stirred into the polymer powder before the monomer was added; and (4) bowl-mix--antibiotic powder mixed into polymer powder using a commercial mixing bowl before the monomer was added. Antibiotic elution was measured using the Kirby-Bauer bioassay. None of the mixing methods had consistently dissimilar homogeneity of antibiotic distribution from the others. Based upon our data we conclude hand-mixed low-dose ALBC is not less homogeneous than commercially premixed formulations.

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.

In a consecutive series of 704 compound fractures, 227 open fractures in 204 patients were managed with the antibiotic bead pouch technique. There were 16 Grade I compound fractures, 83 Grade II fractures, and 128 Grade III open fractures. The mean patient age was 35.25 years (range, 14-87). The Injury Severity Score (ISS) ranged from 9 to 57, with a mean of 15. Porous plastic film is placed over the soft-tissue defect to establish a "closed" bead-hematoma-fracture environment containing high local levels of antibiotic at the fracture site. All patients had serial wound debridements and parenteral systemic antibiotics (cefazolin, tobramycin, penicillin). Bead pouch changes ranged from one to seven per patient (mean, two). During these changes, 1248 cultures were taken, 78 (6.25%) of which were positive in 34 patients. Seventeen patients developed clinical signs consistent with an infection. The wound infection rate was 0% in Grade I open fractures, 1.2% in Grade II compound fractures, and 8.6% in Grade III open fractures. The osteomyelitis rate was 0% in Grade I compound fractures, 2.4% in Grade II open fractures, and 5.5% in Grade III compound fractures. Wound closure was obtained in 134 fractures with delayed primary closure of the skin, in 53 fractures with flap coverage, and in 23 fractures with split-thickness skin graft. Coverage was not completed in 17 wounds, at which time an amputation was performed or death occurred. Time of closure ranged from one to 32 days (mean, 7.1 days).(ABSTRACT TRUNCATED AT 250 WORDS)

Successful treatment of chronic osteomyelitis requires sustained high concentrations of antibiotics locally within the infected bone. The efficacy of biodegradable (poly-DL-lactide-co-glycolide) microspheres containing 30.7% ampicillin anhydrate for the local treatment of experimental staphylococcal osteomyelitis was evaluated in rabbits. In the initial experiment, antibiotic therapy was initiated immediately following injection of Staphylococcus aureus into the proximal tibial metaphysis. A single intramedullary injection of microencapsulated ampicillin (100 mg) prevented osteomyelitis in all seven animals tested and was as effective as a two-week course of parenteral ampicillin administration. When antibiotic therapy was delayed for seven days, osteomyelitis developed in four of eight animals treated locally with microencapsulated ampicillin and in six of eight animals that received parenteral ampicillin therapy. When antibiotic therapy was delayed for seven days and was preceded by debridement, all ten animals treated locally with microencapsulated ampicillin had sterile bone cultures. In contrast, seven of ten animals treated locally with unencapsulated ampicillin powder developed osteomyelitis. Biodegradable antibiotic-loaded microspheres may be of clinical benefit for the local treatment of chronic osteomyelitis.

Adequate debridement remains the most important factor in prevention of chronic sepsis in cases of massive lower limb trauma. Despite treatment with chronic antibiotics, muscle flaps, hyperbaric oxygen, and/or free-tissue transfer, failures are common due to inadequate bone debridement. All bony fragments with marginal soft-tissue attachments and exposed bone without evidence of adequate blood flow must be removed during debridement for optimal results. Laser Doppler flowmetry (LDF) may be a useful adjunct for the assessment of bone viability during both initial and subsequent debridements. Preliminary data on eight patients have demonstrated that bone blood flow as determined by LDF is highly correlated with clinical outcome. In 13 cases, LDF has proved to be helpful in the management of chronic osteomyelitis.

An animal model was used to evaluate and compare silver methacrylate with gentamicin methacrylate in experimental Staphylococcus osteomyelitis. One tibia from each of 54 rabbits was innoculated with 4 X 10(6) CFU of S. aureus and inserted with prepolymerized PMM rods containing either 1% Ag2SO4, 2.5% gentamicin, or no additives. By six weeks, the mortality rate was 61% in controls, 22% in Ag-PMM animals and 6% in gentamicin-PMM animals. Bacterial counts from the bone of dying and surviving animals were significantly lower than controls, 23.6% of controls for the Ag-PMM treated and 6.0% for the gentamicin-PMM treated groups. All surviving animals were culture positive, except for three sterile bones obtained from the gentamicin-PMM group. In light of these results and the favorable characteristics as an antimicrobial agent, further investigation of silver in bone cement (or other vehicles) for the prevention or treatment of bone infection appears warranted.