During the Spanish Civil War (1935-38) Trueta adopted as standard treatment for gunshot wounds and compound fractures the closed plaster method originated by the American surgeon H. Winnett Orr. Trueta called this the biological treatment of wounds. The treatment consisted of débridement and wound excision followed by packing the wound open and immobilizing the limb in a plaster dressing. Also in 1938 the same publisher issued Trueta's book in Trueta's native Catalan as El tractament de les factures de guerra. Whether the Catalan or Spanish edition preceded the other, or whether they might have been issued simultaneously, is unknown. English translation: Treatment of war wounds and fractures: with special reference to the closed method as used in the war in Spain, London, 1939.

With A. E. Barclay, P. M. Daniel, K. J. Franklin, and M. M. L. Prichard. In studying the anurias which follow injury, especially crushing injuries and burns, Trueta’s team demonstrated that both the processes of filtration and of re-absorption are subject to nervous control, leading to the development of a more rational therapy for these conditions.