1. Department of Neurosurgery, St. Hedwig’s Regional Specialist Hospital, ul.Wodociagowa 4, 45-221 Opole, Poland
2. Department of Neurosurgery, Institute of Medical Sciences, University of Opole, Al.Witosa 26, 45-401 Opole, Poland
3. Department of Radiotherapy, Opole Center of Oncology, ul.Katowicka 66a, 45-061 Opole, Poland
4. Department of Orthopaedic Surgery, Okayama Rosai Hospital, Okayama 702-8055, Japan