Mechanical wrist joints with enhanced range of motion, and related devices and methods

A medical instrument comprising:

• a shaft comprising a proximal end portion and a distal end portion;
• an end effector;
• and
• a wrist assembly coupling the end effector to the distal end portion of the shaft, the wrist assembly comprising:
• a proximal segment comprising a first pair of gear features positioned diametrically opposite one another and extending distally from the proximal segment,
• a distal segment comprising a second pair of gear features positioned diametrically opposite one another and extending proximally from the distal segment, the second pair of gear features intermeshable with the first pair of gear features, and
• a pair of load bearing members positioned diametrically opposite each other, each load bearing member of the pair radially offset from the respective first and second pairs of gear features in an intermeshed state with each other;
• and
• a cable drive system operably coupled to drive articulation of the proximal and distal segments relative to one another from a neutral position through a range of articulation via movement of the first and second pairs of gear features relative to each other,
• wherein each of the first pair of gear features comprises a central protrusion, a first outer protrusion, a second outer protrusion, a first recess, and a second recess, wherein the first recess and the second recess are on opposite sides of the central protrusion and between the first outer protrusion and the second outer protrusion, and wherein the central protrusion extends further distally from the proximal segment than the first outer protrusion and the second outer protrusion,
• wherein each of the second pair of gear features comprises a central recess, a first outer recess, a second outer recess, a first protrusion between the central recess and the first outer recess, and a second protrusion between the central recess and the second outer recess,
• wherein, in the neutral position of the proximal and distal segments relative to each other, the central protrusions of the first pair of gear features are respectively received within the central recesses of the second pair of gear features,
• wherein in a first range of articulation of the proximal and distal segments relative to each other in a first direction away from the neutral position, the first outer protrusions of the first pair of gear features are received in the first outer recesses of the second pair of gear features, respectively, and
• wherein in a second range of articulation of the proximal and distal segments relative to each other in a second first direction away from the neutral position, the second outer protrusions of the first pair of gear features are received in the second outer recesses of the second pair of gear features, respectively, and
• wherein the proximal segment and the distal segment are articulatable relative to one another over a range of greater than +/−45 degrees from the neutral position.