During cemented total hip arthroplasty, antibiotic-loaded bone cement is commonly used. Which antibiotics are most commonly incorporated into PMMA cement and what is the mechanism of their local activity?
- A Flucloxacillin — absorbed into cement matrix and released during polymerisation heat
- B Vancomycin and gentamicin — eluted from cement surface over weeks, achieving local concentrations far exceeding MIC while minimising systemic toxicity ✓
- C Rifampicin and linezolid — only effective during cement setting phase
- D Cefazolin — achieves sustained local release for 12 months from deep PMMA layers
Explanation
Vancomycin and gentamicin are the antibiotics most commonly added to PMMA bone cement because they are heat-stable (surviving exothermic polymerisation), water-soluble enough for elution, bactericidal at the cement-bone interface, and cover the most common periprosthetic pathogens (Staphylococcus aureus, coagulase-negative staphylococci, and Gram-negatives). Elution is highest in the first 24–72 hours then sustained at lower levels; local concentrations at the cement-bone interface far exceed systemic MIC for these organisms while systemic absorption is negligible. Beta-lactams degrade in the polymerisation heat and are unsuitable.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.