Aims: A biomechanical and clinical study was made to compare two nonunion fixation device: the AO dynamic compresiòn plate and a locked intramedullary nail.

Methods: A retrospective review was made of all patients from three major hospitals in the Barcelona area with the diagnosis of aseptic non-union of the humeral shaft. After exclusion criteria series were limited to fifty-four patients, treated between 1992 and 2002. Of these, 35 were women and 19 were men with a median age of 55 (18–91) years. Operative treatment was with plate in 74.1% and locked nail in 25.9%. Statistical analysis was made to compare consolidation rate, consolidation time and complications in both devices and to looking for possible prognostic consolidation factors. We used the Finite element Method to compare the biomechanical behaviour between plate and nail.

Results: The consolidation rate was 78.6% with nail and 70.3% in plate, but this rate has significantly improved (p< 0.05) when plate is used in hypertrophic non-union and nail in atrophic union.

The median consolidation time was 5.73 months with nail and 4.92 months in plate.

The complication rate was 21.4% with nail and 20.0% in plate.

Focus deformation is lesser with nail than plate in anterior bending, axial charge and torsion but no in lateral bending.

Six or more cortical screws beside focus with plate increase consolidation too (p< 0.05).

The consolidation rate in graft group was 70.5% versus 85.7% in group without graft.

Conclusions: Plating provides better results in hypertrophic nonunions and nailing in atrophic nonunions.

Six or more cortical screws beside focus when plate is used improves consolidation rate.

Consolidation not seems be modified by graft use.