[1] Univ Hosp Regensburg, Dept Traumasurg, Regensburg, Germany
[2] BG Unfallklin, Ctr Spinal Surg & Neurosurg, Frankfurt, Germany
[3] Regensburg Univ Hosp, Dept Neurosurg, Regensburg, Germany
[4] Univ Bern, Bern Univ Hosp, Inselspital, Dept Orthopaed Surg & Traumatol, Bern, Switzerland