A catheter assembly including a tapered steering spine having a varying stiffness along an axial length. The tapered steering spine is tailored to provide increasing flexibility from proximal to distal in a way that makes the bend radius more uniform along the length of the steering section. In one embodiment, the tapered steering spine includes structures on adjacent rings that engage with each other when the steering section is flexed to limit the minimum bend radius to a predetermined minimum and which enhances the torsional rigidity of the steering section regardless of the degree of flexure of the steering section. The limited bend radius can prevent excessive bending of components such as fiber optics. The enhanced torsional rigidity can negate the need for torque braid in the section of the catheter shaft that surrounds the tapered steering spine.
