[1] Univ Virginia, Dept Orthoped Surg, Charlottesville, VA 22902 USA
[2] Univ Virginia, Dept Spine Surg, Charlottesville, VA 22902 USA
[3] Radiat Effects Res Fdn, Dept Epidemiol, Minamiku, Hiroshima 7320815, Japan
[4] Harvard Univ, Grad Div, Cambridge, MA 02138 USA
[5] Johns Hopkins Univ, Dept Orthoped Surg, Baltimore, MD USA
[6] Johns Hopkins Orthopaed Good Samaritan Hosp, Dept Spine Surg, Baltimore, MD 21239 USA
[7] Thomas Jefferson Univ, Dept Orthopaed Surg, Philadelphia, PA 19107 USA