[1] Department of Neurosurgery,
[2] University Hospital Vrije Universiteit,undefined
[3] P.O. Box 7057,undefined
[4] 1007 MB Amsterdam,undefined
[5] The Netherlands e-mail: W.vOuwerkerk@azvu.nl Fax: +31-20-4443784,undefined
[6] Department of Orthopedic Surgery,undefined
[7] University Hospital Vrije Universiteit,undefined
[8] 1007 MB Amsterdam,undefined
[9] The Netherlands,undefined
[10] Department of Rehabilitation,undefined
[11] University Hospital Vrije Universiteit,undefined
[12] 1007 MB Amsterdam,undefined
[13] The Netherlands,undefined
[14] Department of Radiology,undefined
[15] University Hospital Vrije Universiteit,undefined
[16] 1007 MB Amsterdam,undefined
[17] The Netherlands,undefined