1. Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
2. Rehabilitation Engineering R&D, Brockton/West Roxbury VA Medical Center, West Roxbury, Massachusetts 02132.
3. Department of Orthopedic Surgery, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
4. Department of Surgery, New England Deaconess Hospital, Harvard Medical School, Boston, Massachusetts 02115.
5. Division of Neurology, Brockton/West Roxbury VA Medical Center, Harvard Medical School, West Roxbury, Massachusetts 02132.