A method for forming an implant for a bone comprises the step (20) of generating a first general shape for the implant having a length extending along a long axis of the bone. A step (40) determines an area moment of inertia of a cross section of the implant. Step (40) also determines an area moment of inertia for a cross section of bone coplanar to the cross section of the implant. A percent stress shielding is calculated (50) from the area moments of inertia of the implant and the bone. A step (60) compares the calculated percent stress shielding to a preset threshold. Iteratively, additional general shapes are generated (80) for the implant by locally adjusting the cross section of the implant until the calculated percent stress shielding meets the preset threshold.