The FLOW trial is a multicenter 2×3 factorial RCT enrolling 2,447 patients with open extremity fractures across 41 centers. It randomized patients to three irrigation pressures (high >20 psi, low 5–10 psi, very low 1–2 psi) and two solutions (castile soap vs. normal saline). The primary endpoint was reoperation within 12 months for infection, wound-healing, or bone-healing problems.
For decades, high-pressure pulsatile lavage was standard teaching for open fracture irrigation, supported by experimental data showing superior bacterial removal. Soap was gaining traction after Anglen's 2005 JBJS RCT (400 patients) appeared to favor it over antibiotic solution — but that trial compared soap to bacitracin-containing saline, not plain saline, and had unblinded adjudication.
FLOW changes two things you do in the OR tonight. First, ditch the pulsed lavage: a bulb syringe or gravity bag at 1–2 psi works just as well and avoids the theoretical harms of high-pressure systems (bone damage, intramedullary bacterial propagation). Second, irrigate with plain normal saline: soap increases reoperation risk by 32% overall and nearly doubles the rate of implant exchange for nonunion.
The practical minimum volumes still stand: 3 liters for Gustilo-Anderson grade I, 6 liters for grade II or III. Standardized in the FLOW protocol and consistent with prior guidance.
The one nuance worth knowing: the soap finding did not survive a worst-case sensitivity analysis for loss to follow-up (P=0.16), so the evidence against soap is strong but not ironclad. What is ironclad: soap is no better than saline, so there is no reason to use it.
The FLOW trial is a multicenter 2×3 factorial RCT enrolling 2,447 patients with open extremity fractures across 41 centers. It randomized patients to three irrigation pressures (high >20 psi, low 5–10 psi, very low 1–2 psi) and two solutions (castile soap vs. normal saline). The primary endpoint was reoperation within 12 months for infection, wound-healing, or bone-healing problems.
For decades, high-pressure pulsatile lavage was standard teaching for open fracture irrigation, supported by experimental data showing superior bacterial removal. Soap was gaining traction after Anglen's 2005 JBJS RCT (400 patients) appeared to favor it over antibiotic solution — but that trial compared soap to bacitracin-containing saline, not plain saline, and had unblinded adjudication.
FLOW changes two things you do in the OR tonight. First, ditch the pulsed lavage: a bulb syringe or gravity bag at 1–2 psi works just as well and avoids the theoretical harms of high-pressure systems (bone damage, intramedullary bacterial propagation). Second, irrigate with plain normal saline: soap increases reoperation risk by 32% overall and nearly doubles the rate of implant exchange for nonunion.
The practical minimum volumes still stand: 3 liters for Gustilo-Anderson grade I, 6 liters for grade II or III. Standardized in the FLOW protocol and consistent with prior guidance.
The one nuance worth knowing: the soap finding did not survive a worst-case sensitivity analysis for loss to follow-up (P=0.16), so the evidence against soap is strong but not ironclad. What is ironclad: soap is no better than saline, so there is no reason to use it.