Reamed intramedullary nailing versus circular frame external fixation for segmental tibial fractures (STIFF-F): a mixed methods feasibility study by Hing, C, Tutton, E, Smith, T, Glaze, M, Cook, J, Dritsaki, M, Phelps, E, Cooper, C, Tompeter, A, Pearse, M, Law, M, Costa, M