24 patients with Th12-L1 fractures treated with a Dick internal fixator were analyzed to assess predictors of poor outcome. 4 patients had fixation without bone transplantation, 20 patients had a posterior fusion, and 12 of them had additional transpedicular spongioplasty. There were fractures of the transpedicular screws in 4 and screw migration in 2 cases. The increase in the local kyphosis angle was greater than the increase in the anterior compression angle and this did not correlate with spongioplasty or fusion. Fixation failure was in all cases related to a disproportionate increase in the local kyphosis angle. There was no difference between the patients with transpedicular spongioplasty and posterior fusion and the other patients with respect to results and complications. Bony collapse was not the major cause of failure and consequently there was no measureable contribution of transpedicular spongioplasty. We found that the Dick internal fixator for unstable fractures was associated with a higher complication rate than earlier reported.