Implantable devices for fixation of curved bones such as the pelvic ring pubic symphysis and acetabulum, and methods for the use of the devices are disclosed. The implantable devices are convertible between a flexible state and a rigid state using a shape locking section. The implantable devices further include a main body and a distal bone interface. In a flexible state, the devices may be inserted along, and conform to a curved pathway, and in the rigid state, the devices may support the mechanical loads required to fixate a fracture.