[1] Univ Calif San Francisco, Dept Neurosurg, 400 Parnassus Ave, San Francisco, CA 94143 USA
[2] Univ Virginia, Med Ctr, Dept Neurosurg, POB 800212, Charlottesville, VA 22908 USA
[3] Hosp Valle De Hebron, Spine Surg Unit, 119-129 Traumatol Bldg,2nd Floor, Barcelona 08035, Spain
[4] Washington Univ, Dept Orthopaed Surg, 4400 Clayton Ave, St Louis, MO 63110 USA
[5] Norton Leatherman Spine Ctr, 210 East Gray St,Suite 900, Louisville, KY 40205 USA
[6] Acibadem Univ, Dept Orthoped & Traumatol, 40 Maslak, TR-344457 Istanbul, Turkey
[7] Ankara ARTES Spine Ctr, Iran Caddesi 45-2, TR-06700 Ankara, Turkey
[8] Hosp Univ La Paz, Spine Surg Unit, Paseo Castellana 261, Madrid 28046, Spain
[9] Schulthess Klin, Dept Orthoped & Neurosurg, Spine Ctr Div, Lengghalde 2, CH-8008 Zurich, Switzerland
[10] Bordeaux Univ Hosp, Spine Surg Unit, Pl Amelie Raba Leon, F-3300 Bordeaux, France
[11] VHIR, Barcelona, Spain
[12] Univ Kansas, Med Ctr, Dept Orthopaed Surg, 3901 Rainbow Blvd, Kansas City, KS 66103 USA
[13] Hosp Special Surg, Dept Orthopaed Surg, 541 E 71st St,4th Floor, New York, NY 10021 USA
[14] Presbyterian St Lukes Rocky Mt Hosp Children, Denver Int Spine Ctr, 1601 E 19th Ave 6250, Denver, CO 80218 USA
[15] Univ Pompeu Fabra, Ctr Res Hlth & Econ, Dept Econ & Business, Off 23-111 Merce Rodoreda Bldg,Ciutadella Campus, Barcelona 08005, Spain