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Does the induced membrane have antibacterial properties? An experimental rat model of a chronic infected nonunion
Sami Roukoz1, Georges El Khoury1, Elie Saghbini1
1Orthopedic Surgery Department, Hotel-Dieu de France Hospital, Saint-Joseph University, Beirut, Lebanon.
Introduction:
The Masquelet procedure proved its efficiency in treating infected nonunion filling bony gaps up to 25 cm. Yet the use of local antibiotics is still questionable in the daily practice with lack of evidence regarding its usefulness in controlling infection. An experimental rat model is put in place to study the antibacterial properties of the induced membrane produced during the first stage of Masquelet.
Method:
Twenty-three-month-old wistar male rats are inoculated with a 0.5 mL solution of 10^8 CFU/mL MRSA over a critical fracture done on the right femur. Six weeks later, remaining 11 rats exhibiting signs of a chronic infection with a sinus tract and oozing pus along with radiological nonunion are used for a first stage Masquelet procedure. They are randomly divided into two groups with six rats having no local antibiotic in the cement mixture and five rats having 3 g of vancomycin mixed with gentamycin loaded cement. Six weeks later (twelve weeks from baseline), all eleven rats are euthanized and blood samples for C-reactive protein are withdrawn. The induced membrane is identified and resected along with bone fragments and sent for cultures and pathology.
Results:
MRSA is isolated in the cultures of all six rats in the first group where no local antibiotic was added. Altered polymorphonuclears with abscess and pus are noted on four of six pathology samples. However in the second group where local antibiotics were added, three out of five rats exhibited eradication of MRSA (p = 0.034) and all samples did not exhibit clear infection signs on pathology. A pyo-epithelioid over a foreign body reaction is seen predominantly in this group demonstrating a regenerative process.
Discussion:
The induced membrane does not have antimicrobial properties capable of overcoming an infected nonunion on its own. When local antibiotics were added during the first stage of the Masquelet procedure, new bone formation occurred indicating the need to control an infection in order for bone union to occur.
Conclusion:
Local antibiotics use in adjunction to extensive debridement is advisable during the first stage of a Masquelet procedure for an infected nonunion.
Insights
The Masquelet procedure requires local antibiotics to effectively treat infected nonunion bone fractures. Adding antibiotics to the induced membrane cement during the first stage promotes bone healing and infection control in rats.
Area of Science:
- Orthopedic Surgery
- Infectious Disease Research
- Biomaterials Science
Background:
- The Masquelet technique is effective for large bone defects but its use with local antibiotics for infected nonunion is debated.
- Limited evidence exists on the efficacy of local antibiotics in controlling infection during the Masquelet procedure.
- An experimental rat model was utilized to investigate the antibacterial properties of the induced membrane.
Purpose of the Study:
- To evaluate the antibacterial properties of the induced membrane in the Masquelet procedure.
- To determine the effectiveness of local antibiotics in controlling MRSA infection in a rat model of infected nonunion.
- To assess the impact of local antibiotics on bone healing during the Masquelet procedure.
Main Methods:
- A critical femur fracture in rats was infected with MRSA.
- Rats underwent the first stage of the Masquelet procedure, with cement either containing or lacking local antibiotics (vancomycin and gentamicin).
- Induced membranes were analyzed for bacterial presence, pathology, and C-reactive protein levels.
Main Results:
- Methicillin-resistant Staphylococcus aureus (MRSA) was isolated in all rats without local antibiotics.
- Pathology revealed infection signs in rats without local antibiotics.
- Rats treated with local antibiotics showed significant MRSA eradication (p=0.034) and reduced infection signs, with evidence of regenerative bone formation.
Conclusions:
- The induced membrane alone lacks sufficient antimicrobial properties to resolve infected nonunion.
- Local antibiotics are crucial when combined with the Masquelet procedure for infected nonunion, facilitating bone healing by controlling infection.
- Using local antibiotics during the first stage of the Masquelet procedure is recommended for treating infected nonunion.
