[1] Rothman Inst, Jefferson Med Coll, 925 Chestnut St, Philadelphia, PA 19107 USA
[2] Univ Kansas, Med Ctr, Kansas City, KS 66045 USA
[3] UCLA, Spine Ctr, Santa Monica, CA USA
[4] USC Spine Ctr, Los Angeles, CA USA
[5] Norton Leatherman Spine Ctr, Louisville, KY USA
[6] Northwestern Univ, Feinberg Sch Med, Chicago, IL 60611 USA
[7] Brown Univ, Providence, RI 02912 USA
[8] Rhode Isl Hosp, Providence, RI 02903 USA
[9] Miriam Hosp, Providence, RI 02906 USA
[10] Norman Prince Neurosci Inst, Providence, RI USA
[11] Duke Univ, Med Ctr, Durham, NC 27706 USA
[12] Univ Pittsburgh, Med Ctr, Pittsburgh, PA 15260 USA
[13] Univ Pittsburgh, Pittsburgh, PA 15260 USA
[14] Cleveland Clin, Cleveland, OH 44106 USA
[15] Mayo Clin, Rochester, MN USA
[16] Indiana Univ, Indianapolis, IN 46204 USA
[17] Indiana Spine Grp, Indianapolis, IN USA
[18] Toronto Western Hosp, Toronto, ON, Canada
[19] Univ Southern Calif, Los Angeles, CA 90089 USA
[20] Univ Calif Los Angeles, Los Angeles, CA 90024 USA
[21] Mayo Clin Hlth Syst, Austin, MN USA
[22] Medstar Union Mem Hosp, Baltimore, MD USA
[23] Johns Hopkins Med Inst, Baltimore, MD 21205 USA
[24] Columbia Univ, New York, NY 10027 USA
[25] New York Presbyterian Allen Hosp, New York, NY USA