[1] Cleveland Clin, Ctr Spine Hlth, 9500 Euclid Ave,S-40, Cleveland, OH 44195 USA
[2] Case Western Reserve Univ, Sch Med, 2109 Adelbert Rd, Cleveland, OH 44106 USA
[3] Cleveland Clin, Dept Neurosurg, 9500 Euclid Ave,S-40, Cleveland, OH 44195 USA
[4] Cleveland Clin, Dept Orthopaed Surg, 9500 Euclid Ave, Cleveland, OH 44195 USA
[5] Univ Hosp Case Med Ctr, Dept Neurosurg, 11100 Euclid Ave, Cleveland, OH USA
[6] Case Western Reserve Univ, Dept Epidemiol & Biostat, 2109 Adelbert Rd, Cleveland, OH 44106 USA