1. Department of Mechanical Engineering, Stanford University, Durand Building 061, 496 Lomita Mall, Stanford, CA 94305-4308
2. Department of Mechanical Engineering, Rose-Hulman Institute of Technology, Rose-Hulman CM 4003, 5500 Wabash Avenue, Terre Haute, IN 47803
3. Department of Mechanical Engineering, Stanford University, Durand Building 061, 496 Lomita Mall, Stanford, CA 94305-4308; Department of Orthopedic Surgery, Stanford University Medical Center, 300 Pasteur Drive, R144, MC 5341, Stanford, CA 94305-5341; and Bone and Joint Center, Palo Alto, VA, 3801 Miranda Avenue, Palo Alto, CA 94304-1290