[1] Rochester Inst Technol RIT, Dept Biomed Engn, Rochester, NY 14623 USA
[2] Paracelsus Med Univ Salzburg Austria, Acad Teaching Hosp, Spine Ctr, Schon Clin Munich Harlaching, D-81547 Munich, Germany
[3] Paracelsus Med Univ Salzburg Austria, Spine Res Inst, D-81547 Munich, Germany