In a prospective, randomized, controlled, single-blind study, 186 patients with an open tibial will be randomized to receive either the standard of care (fixation by nail or external fixator and routine soft-tissue management), or the standard of care with percutaneous injection, one month after fracture, of autologous concentrated bone-marrow. Randomization will be stratified by severity of the open wound. The primary outcome measure will be the proportion of patients requiring secondary intervention because of delayed union or nonunion within twelve months post-fracture.