A minimally invasive surgical instrument comprising: an elongate shaft having a working end, a proximal end, and a shaft axis between the working end and the proximal end； an end effector； a wrist member having an inner spring which includes a proximal portion connected to the working end of the elongate shaft and a distal portion connected to the end effector, the wrist member having a plurality of annular disks distributed along an axis of the inner spring, the annular disks each having an inside edge connected with the inner spring； and a plurality of actuation cables having distal portions connected to the end effector and extending from the distal portion of the wrist member through the wrist member toward the elongate shaft to proximal portions which are actuatable to bend the wrist member in pitch rotation and yaw rotation.
