Instrument roll control

A medical instrument, comprising:

• an elongate shaft;
• a handle coupled to a proximal portion of the elongate shaft;
• an axle rotatably mounted to the handle and having a first channel and a mating feature, wherein rotation of the axle causes the elongate shaft to rotate;
• an axle catch disposed within the handle and providing a key, the axle catch being vertically translatable relative to the axle between a locked position, in which the key is engaged with the mating feature to impede rotation of the axle, and an unlocked position, in which the key is disengaged from the mating feature to permit rotation of the axle;
• an axle-retention structure disposed in the handle and defining a second channel;
• and
• a slider including a lower portion disposed in the first channel and an upper portion disposed in the second channel, wherein the slider is moveable relative to the axle along the first channel and moveable relative to the axle-retention structure along the second channel, and wherein the slider interacts with the first and second channels to limit rotation of the axle.

A method of operating a medical instrument, comprising:

• moving an axle catch from a locked position to an unlocked position and thereby disengaging a key feature of the axle catch from a mating feature of an axle, wherein the axle catch and the axle are arranged in a handle;
• rotating the axle in a first rotational direction from a first position to a second position and thereby rotating an elongate shaft coupled to the handle about a roll axis, wherein a lower portion of a slider abuts a first stopper surface of a first channel formed in the axle when the axle is in the second position;
• and
• rotating the axle in the first rotational direction from the second position to a third position to further rotate the elongate shaft and thereby engaging an upper portion of the slider against a second stopper surface of a second channel formed in an underside of an axle-retention structure,
• wherein engagement of the upper portion with the second stopper surface and engagement of the lower portion with the first stopper surface prevents further rotation of the axle in the first rotational direction, and thereby prevents further rotation of the elongate shaft.