The assumption that flooding a surgical wound with antibiotics guarantees lower infection rates has long guided orthopedic practice — but a randomized clinical trial examining adjunctive intrawound tobramycin in periarticular tibial fractures is now challenging that logic in a meaningful way. If local antibiotic saturation alone cannot prevent surgical site infections, the question becomes: what biological mechanism is allowing bacteria to survive?
The correspondence published in JAMA responds to a recent randomized clinical trial that found combination therapy using intrawound tobramycin powder — applied directly to the fracture site during surgery — provided no significant benefit over standard care in reducing surgical site infections (SSIs) in tibial fractures. Tobramycin is an aminoglycoside antibiotic with established activity against gram-negative organisms and is commonly deployed in orthopedic settings via antibiotic-loaded bone cement or powder. The null result held despite tobramycin achieving locally high concentrations that would be expected to exceed minimum inhibitory concentrations for most susceptible pathogens.
The authors of this letter suggest that intracellular bacterial persistence may be a key explanatory mechanism — certain bacteria, particularly Staphylococcus aureus, can invade osteoblasts and other host cells, effectively shielding themselves from extracellular antibiotic exposure regardless of local concentration. This intracellular sanctuary model is well-supported in basic science literature but rarely enters clinical trial design considerations. From a broader research perspective, this finding places fracture-related infection in the same conceptual territory as other persistent bacterial infections — biofilm-associated pathology and small colony variants — where pharmacodynamic thinking must shift from extracellular killing to intracellular penetration. The trial's null result, while incremental in isolation, may be paradigm-challenging if it prompts a reorientation toward agents with proven intracellular activity, such as rifampicin combinations or newer antibiotics, in future fracture infection prevention protocols.