Surgical tool with a two degree of freedom wrist

A minimally invasive surgical tool comprising:

• a tubular instrument shaft having a proximal end and a distal end with a bore there between, the shaft having an instrument shaft axis;
• an end effector comprising an end effector body;
• an intermediate wrist member pivotally coupled with the distal end of the instrument shaft and pivotally coupled with the end effector body, pivoting of the intermediate member relative to the instrument shaft orienting the intermediate member about a first axis relative to the instrument shaft, and pivoting of the end effector body relative to the intermediate member orienting the end effector about a second axis relative to the intermediate member, the first axis being transverse to the instrument shaft axis, the second axis being transverse to the first axis, the intermediate member having an exterior width along the first axis and an exterior length along the second axis, the length being significantly different than the width so that the intermediate member has an elongate cross section;
• an actuation system extending distally through the bore of the instrument shaft so as to orient the end effector body and actuate the end effector, a portion of the actuation system laterally separated from the elongate cross section of the intermediate member between the instrument shaft and the end effector body;
• a first joint pivotally coupling the instrument shaft to the intermediate member;
• and
• a second joint pivotally coupling the intermediate member to the end effector body,
• wherein the first joint comprises a single pivot shaft extending along the first axis within the width of the intermediate member so that the first joint is disposed within a central region between the instrument shaft and the end effector body clear of the laterally separated portion of the actuation system, wherein the second joint comprises first and second coaxial pivot shafts separated along the second axis.