In the United States, there are approximately 1 million fractures annually [1]. These fractures can be treated successfully with the use of casts or internal fixation (i.e. screws, bone plates, or intramedullary rods). However, for approximately 1 out of 20 people with a fracture, these treatments are not successful and result in either a malunion or a non-union. A malunion or a non-union reduces the ability of the bone to withstand the loads it is intended to take. This can cause pain and suffering for the patient. Clinically, non-unions can be treated using mechanical stimulation via an external fixator. Current treatments and the literature suggest that the mechanical environment of a healing fracture callus can influence tissue differentiation, perhaps even stimulate healing [2,3,4,5,6,7]. This leads to the overarching question, what is the precise relationship between the local mechanical environment of a fracture and patterns of bone repair? In order to answer this question, one must be able to control and measure the amount of motion or force applied to the fracture so as to properly relate the healing patterns with a particular stimulus.

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