[1] Univ Wisconsin, Dept Orthopaed Surg, Madison, WI USA
[2] Univ Wisconsin, Dept Neurol Surg, Madison, WI USA
[3] Univ Alabama, Div Neurol Surg, Birmingham, AL USA
[4] Harvard Univ, Sch Med, Dept Neurosurg, Boston, MA USA
[5] Beth Israel Deaconess Med Ctr, Boston, MA 02215 USA
[6] Univ Med & Dent New Jersey, New Jersey Med Sch, Dept Neurosurg, Newark, NJ 07103 USA
[7] Univ Calif Los Angeles, David Geffen Sch Med, Div Neurosurg, Los Angeles, CA 90095 USA
[8] Columbia Univ, Neurol Inst, Dept Neurol Surg, New York, NY USA
[9] Univ Calif San Francisco, Dept Neurosurg, San Francisco, CA 94143 USA
[10] Univ Iowa Hosp & Clin, Dept Neurosurg, Iowa City, IA 52242 USA
[11] Mt Sinai Sch Med, Dept Neurosurg, New York, NY USA
[12] Penn State Coll Med, Dept Orthopaed Surg, Milton S Hershey Med Ctr, Hershey, PA USA