What is the best antibiotic for a laceration to the bone?

Best Antibiotic for Laceration to the Bone

For a laceration extending to bone, use cefazolin 2g IV as the first-line antibiotic, with treatment limited to 24-48 hours maximum unless there are signs of active infection. 1

Antibiotic Selection Based on Wound Characteristics

Clean, Non-Contaminated Bone Exposure

• Cefazolin 2g IV slow infusion is the preferred agent for soft tissue wounds with bone involvement 1
• Provides excellent coverage against Staphylococcus aureus, streptococci, and common gram-positive organisms that colonize skin 1
• Re-dose with 1g if procedure/treatment duration exceeds 4 hours 1
• Duration should be limited to the operative period, maximum 24 hours 1

Contaminated or Severely Contused Wounds

For large, contused soft tissue wounds with bone exposure (equivalent to open fracture stage II-III):

• Aminopenicillin + beta-lactamase inhibitor (e.g., ampicillin-sulbactam) 2g IV 1
• Re-dose with 1g if duration exceeds 2 hours 1
• Maximum duration: 48 hours unless active infection is present 1
• This provides broader coverage including anaerobes and gram-negative organisms 1

Penicillin Allergy

• Clindamycin 900 mg IV slow infusion 1, 2
• Re-dose with 600 mg if duration exceeds 4 hours 1
• For contaminated wounds, add gentamicin 5 mg/kg/day to cover gram-negative organisms 1
• Alternative: Vancomycin 30 mg/kg over 120 minutes (single dose) 1

Critical Timing Considerations

Antibiotics must be administered as early as possible—ideally within 30 minutes of injury or before surgical incision—to prevent intracellular bacterial penetration. 3 Research demonstrates that MRSA can infiltrate bone cells within 15-30 minutes of exposure, and delayed antibiotic administration (beyond 3 hours) significantly increases infection risk 1, 3.

Duration of Therapy: Key Distinction

Prophylaxis vs. Treatment

• For clean lacerations requiring surgical repair: prophylaxis only, limited to 24 hours maximum 1
• For contaminated wounds (open fractures): therapy for 48 hours maximum in absence of active infection 1
• The 2023 World Society of Emergency Surgery guidelines specifically recommend no more than 24 hours of antibiotics after injury for type III open extremity fractures in the absence of clinical infection 1

When to Extend Beyond 48 Hours

• Only continue antibiotics beyond 48 hours if there are clinical signs of active infection (erythema, purulent drainage, fever, elevated inflammatory markers) 1
• For established bone infections (osteomyelitis), treatment duration extends to weeks with different regimens 4

Special Considerations

Simple Hand Lacerations

• No antibiotic prophylaxis is needed for simple hand lacerations that do not involve bone, tendon, nerve, or joint structures 5
• A randomized controlled trial showed only 1% infection rate regardless of antibiotic use 5

Bite Wounds with Bone Involvement

• Amoxicillin-clavulanate orally or ampicillin-sulbactam IV for broader anaerobic coverage 1
• These provide coverage against Eikenella (human bites) and Pasteurella (animal bites) 1

MRSA Risk Factors

Consider vancomycin instead of cefazolin if:

• Known MRSA colonization 1
• Recent hospitalization in unit with high MRSA prevalence 1
• Previous antibiotic therapy 1
• Reoperation 1

Common Pitfalls to Avoid

• Do not extend prophylactic antibiotics beyond 24-48 hours "just to be safe"—this increases antibiotic resistance without improving outcomes 1
• Do not delay antibiotic administration—the window for preventing intracellular bacterial penetration is narrow (15-30 minutes) 3
• Do not use antibiotics for simple lacerations without bone involvement—there is no evidence of benefit 5
• Do not assume systemic antibiotics alone are sufficient for severe contamination—consider local antibiotic therapy (antibiotic beads) for type III open fractures with bone loss 1