A pull wire attachment system for a minimally invasive medical instrument comprises an anchoring element, a steerable tube, and a pull wire assembly. The anchoring element comprises a hollow tube having a first outer diameter. The pull wire assembly comprising a pull wire having a proximal end and a distal end and a securing element coupled to the distal end. A portion of the pull wire is disposed within a groove having an open cross-sectional shape extending along a length of the steerable tube. The securing element includes a second outer diameter sized smaller than the first outer diameter. The securing element is coupled to the anchoring element to prevent proximal translation of the distal end of the pull wire along a longitudinal axis of the medical instrument past the anchoring element. A proximal end of the securing element is disposed distal to a distal end of the steerable tube.