1. Department of General Surgery, Aberdeen Royal Infirmary, Foresterhill Health Campus, Foresterhill Rd, Aberdeen AB25 2ZN, UK
2. Department of Surgery, Queens Hospital, Belvedere Road, Burton on Trent, DE13 0RB, UK
3. Department of Neurosurgery, Aberdeen Royal Infirmary, Foresterhill Health Campus, Foresterhill Rd, Aberdeen AB25 2ZN, UK