IntroductionTreatment options for open tibial shaft fractures include external fixation with or without early conversion to internal fixation. ObjectivesThe aim of this study was to describe 1) early conversion to internal fixation and definitive external fixation and 2) in case of conversion, to identify risk factors for complications. MethodsSeventy-two external fixations of open fractures of the tibial shaft (Gustilo classification, 7 fractures (9.7 %) grade I, 25 fractures (34.7 %) grade II, 40 fractures (55.6 %) grade III (31 grade IIIA and 9 grade IIIB)) were included in a continuous non-randomised study. Thirty-three fractures without infection signs were converted to internal fixation at a mean time of 40.5 +/-15 days (IF group). External fixation was maintened in the remaining 39 fractures (EF group). ResultsIn the “IF” group, the union rate was 69.7 % at 6.3 +/-3.6 months (3–16). All patients had complete union at 16 months, requiring 2.8 +/-0.8 reoperations. Fixation with external fixation only (“EF” group) showed a union rate of 51.3 % at 8.9 +/-4 (5–22) months and 96 % at 16 months after 3.7 +/-0.9 reoperations. Superficial infection (12.1 %; p = 0.011) and numerous surgeries (2.76; p = 0.004) were found to be risk factors for deep infection. Time to wound closure >7 days (p = 0.049), time to reoperation >28 days (p = 0.00), numerous surgeries (2.76; p = 0.004) and deep infection (6.1 %; p = 0.027) were found to be union failure factors. ConclusionEarly conversion of external fixation to internal fixation is an effective option to achieve bone union of open tibial fractures in selected patients.