Navicular stress fracture in high-performing twin brothers: a case report.

Navicular stress fractures mainly occur in sprinting and push-off athletes. Numerous predisposing factors have been implicated in their development. Within a six-week interval in the summer of 2009, twin brothers, both elite track and field athletes, presented to us with medial foot pain. Plain radiographs were negative but a radioisotope bone scan and CT scan revealed an incomplete navicular fracture in both of them. The fracture was typically located in the proximal dorsal cortex of the central portion of the navicular bone. The presence of such a stress fracture in high performing, monozygotic twins, has never been described. As extrinsic and intrinsic risk factors, their comparability of mechanical stresses and kinematics as well as a genetic predisposition can be put forward. This case report suggests that a complex interaction between mechanical and genetic risk factors exists in the development of navicular stress fractures.