Joshua D. Lindsey, MD and James C. Krieg, MD J Am Acad Orthop Surg, Vol 19, No 1, January 2011, Intramedullary nailing of femoral shaft fracture can result in inadvertent malalignment. Malrotation is the most common cause of deformity, but it is underrecognized, in part because of the difficulty in accurately assessing rotation as well as the variation that exists in normal anatomy. The consequences of femoral malrotation are not completely understood. However, initial biomechanical studies suggest that it causes a substantial change in load bearing in the affected extremity. Clinical examination, fluoroscopy, and ultrasonography are useful in measuring femoral rotational alignment intraoperatively and postoperatively. CT is useful in the identification of the degree of malrotation and in surgical planning.