Preparing High-Dose Antibiotic-Loaded Bone Cement

Indications

• Cement spacers or beads for treatment of periprosthetic infection
• Cement spacers or beads for treatment of open fracture-associated infections
• Cement beads for acute management of open fractures

Preoperative Planning

• In the setting of chronic infection, culture results should be obtained from a joint aspirate if possible so that antimicrobials in the cement can be tailored to the pathogen. This may not be possible in the acute setting.

Mixing Technique

• Crush any large chunks in the antibiotic powder
• Mix antibiotic powder and PMMA polymer until a homogenous powder is achieved
• Add monomer
  
  **Alternatively, one can add antibiotic powder after mixing the PMMA polymer and monomer
• Mix with spatula and knead with hands
  • wetting gloves with saline will prevent dough from adhering to your hands
• Fashion into beads or spacer
  • Beads
    • roll dough into cylinder with 10-15 mm diameter
    • cut into 1 cm section
    • straighten the needle of a heavy monofilament suture and string the beads
    • tie knots on the ends to prevent the beads from slipping off

Recipes

General Considerations:

• Note that in addition to its antimicrobial role, cefazolin also plays a role as a poragen.  The increased porosity increases the elution of antimicrobials from the cement.
• Eight to fourteen grams of antibiotics should be used per forty gram batch of PMMA.
• When one approaches fourteen grams of antibiotics per batch, workability of the ALBC decreases. Using slightly less (approximately 7/8) polymer, to increase the monomer (liquid) to polymer (powder) ratio, will improve the workability of the cement, but may also further increase the setting time.
• Consider decreasing vanco and tobra doses in patients with history of renal pathology.

Recipe for high-dose antibiotic bone cement per 40 gram batch of PMMA for most applications.

• 3.6 g tobramycin
• 2-6 g cefazolin
• 2-4 g vancomycin

Recipe for high-dose antibiotic bone cement per 40 gram batch of PMMA if coverage for gram negative anaerobes is required:

• 3.6 g tobramycin
• 0-3 g cefazolin
• 3-6 g cefoxitin
• 2-4 g vancomycin

Recipe for antifungal bone cement per 40 gram batch of PMMA:

• 50 mg amphotericin
• 10 g cefazolin

Alternative recipe for antifungal bone cement per 40 gram batch of PMMA:

• 300 or 600 mg voriconazole
• No filler/poragen (eg, cefazolin) is required

Complications

The use of high-dose antimicrobial-loaded bone cement is generally considered safe. Mean peak tobramycin serum levels reported in the literature range from 0.12 to 1.1µg/mL. When given parenterally, optimum peak serum concentration of tobramycin is between 6-10 µg/mL and trough concentrations should be less than 2 µg/mL. Toxicity is associated with peak levels above 12 µg/mL and trough levels above 2µg/mL.

There have been no case reports of acute renal failure (ARF) after implantation of ALBC beads. However there have been approximately 19 cases reported of acute renal failure or acute kidney injury after implantation of ALBC spacers for treatment of chronic PJI. The increased incidence of ARF after spacer implantation is likely due to increased antimicrobial load due to the greater volume of ALBC used for construction of the spacer. Most  cases were associated with elevated serum aminoglycoside levels (range 2 to 19.8 µg/mL).

References

Include limited reference list