Comparison of two headless screw designs for fixation of capitellum fractures.

In order to determine the effects of two different headless screw designs on fixation of simulated capitellum fractures six matched pairs of embalmed humeri had simulated capitellum fractures created. Fixation with Acutrac compression screws was compared to Herbert screws in a matched pair experimental design. All specimens were cyclically tested with simulated physiologic loading. Both displacement of the capitellum as a function of the number of cycles and failure loads were determined. Fixation by the Acutrac screws was significantly more stable than Herbert screws at 2000 cycles, 0.17 mm wersus 1.57 mm (p < 0.02) The Acutrac fixation also had a higher failure load, 154 N versus 118 N (p < 0.05). The Acutrac screws tested in this biomechanical study provided more stable fixation of simulated capitellum fractures than Herbert screws. This appears to be related to the design of these screws.