Duroplasty for injured cervical spinal cord with uncontrolled swelling: protocol of the DISCUS randomized controlled trial by Saadoun, S, Grassner, L, Belci, M, Cook, J, Knight, R, Davies, L, Asif, H, Visagan, R, Gallagher, MJ, Thomé, C, Hutchinson, PJ, Zoumprouli, A, Wade, J, Farrar, N, Papadopoulos, MC