Fractures resulting in impaired healing can be treated with mechanical stimulation via external fixators. To examine the effect of mechanical stimulation on fracture healing, we developed an external fixator for use in a mouse model. A 0.5 mm tibial osteotomy was stabilized with the external fixator in C57BL/6 mice. Osteotomies in the treatment group (nt = 41) were subjected to daily sessions of 150 μm of controlled displacement with the aim to create a more mineralized callus at 21 days compared with the control group (nc = 39). Qualitative assessment of the histology found no notable difference in healing patterns between groups at 7, 12, 17, and 21 days. At 21 days, micro-computed tomography (CT) analysis showed that the control group had a significantly higher bone volume (BV) fraction and trabecular number compared with treatment; however there was no significant difference in the total volume (TV) of the callus or trabecular thickness between groups. In summary, the external fixator was used with a motion application system to apply controlled displacement to a healing fracture; however, this treatment did not result in a more mineralized callus at 21 days.