[1] Univ Kansas, Med Ctr, Dept Neurosurg, Mail Stop 3021,3901 Rainbow Blvd, Kansas City, KS 66160 USA
[2] Univ Toronto, Toronto Western Hosp, Univ Hlth Network, Toronto, ON M5T 2S8, Canada
[3] Univ Toronto, Toronto Western Hosp, Dept Surg, Techna Res Inst, Toronto, ON M5T 2S8, Canada
[4] Univ Hlth Network, Toronto Western Hosp, Toronto Western Res Inst, Toronto, ON, Canada
[5] Univ Kansas, Med Ctr, AR Dykes Lib Hlth Sci, Kansas City, KS 66160 USA
[6] Thomas Jefferson Univ Hosp, Dept Neurol, Philadelphia, PA 19107 USA
[7] Thomas Jefferson Univ Hosp, Dept Orthopaed Surg, Philadelphia, PA 19107 USA
[8] Univ Toronto, Toronto Western Hosp, Dept Surg, Univ Hlth Network, Toronto, ON M5T 2S8, Canada
[9] Thomas Jefferson Univ Hosp, Dept Orthopaed Surg, Philadelphia, PA 19107 USA