[1] Univ Virginia, Dept Neurosurg, Charlottesville, VA 22908 USA
[2] Weill Cornell Med Coll, Dept Neurosurg, New York, NY 10065 USA
[3] Univ Calif San Diego, Sch Med, La Jolla, CA 92093 USA
[4] Rocky Mt Hosp Children, Dept Orthoped Surg, Denver, CO 80205 USA
[5] NYU, Hosp Joint Dis, Dept Orthoped Surg, New York, NY 10016 USA
[6] Univ Calif San Francisco, Dept Neurosurg, San Francisco, CA 94143 USA