1 Division of Pain Medicine, Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
2 Berman Institute of Bioethics, The Johns Hopkins University, Baltimore, Maryland.
3 Department of Orthopaedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
4 Department of Orthopaedic Surgery, The University of Pennsylvania, Philadelphia, Pennsylvania, USA.