Antibiotic Containing Bone Substitute in Major Hip Surgery: A Long Term Gentamicin Elution Study

Area of Science:

• Orthopedic Surgery
• Pharmacokinetics
• Biomaterials Science

Background:

• Surgical site infections are a risk in orthopedic procedures.
• Antibiotic-eluting bone substitutes can deliver localized antimicrobial agents.
• Hydroxyapatite and calcium sulfate composites offer potential for bone regeneration and drug delivery.

Purpose of the Study:

• To evaluate gentamicin elution from a novel biphasic bone substitute (hydroxyapatite/calcium sulfate).
• To compare the pharmacokinetics of this substitute with poly (methyl methacrylate) bone cement.
• To assess the safety and efficacy in patients undergoing hip fracture surgery or hip revision.

Main Methods:

• Gentamicin elution measured in serum (4 days) and urine (30 days) in 20 patients.
• Pharmacokinetic comparison with published data on gentamicin-PMMA cement.
• Clinical follow-up for up to one year.

Main Results:

• Serum gentamicin levels were significantly lower than urine levels, indicating high local concentrations.
• The biphasic substitute demonstrated a higher initial gentamicin release ('burst') compared to PMMA.
• Complete gentamicin elution occurred by 30 days, unlike PMMA which showed sub-inhibitory levels at 60 days.
• No surgical site infections were observed in the study group.

Conclusions:

• The gentamicin-eluting biphasic bone substitute ensures efficient, localized antibiotic delivery.
• This novel biomaterial shows promise for infection prophylaxis in hip fracture and revision surgeries.
• Complete elution within 30 days suggests effective local antimicrobial activity and reduced systemic exposure.