1. Department of Mechanical Engineering; Polytechnique Montréal; P.O. Box 6079, Station Centre-Ville, Montréal Québec Canada H3C 3A7
2. Sainte-Justine University Hospital Center; 3175 Côte-Ste-Catherine Rd., Montréal Québec Canada H3T 1C5
3. Medtronic; Spinal Applied Research; 1800 Pyramid Place Memphis 38132 Tennessee