Comparing a Mechanical Analogue With the Da Vinci User Interface: Suturing at Challenging Angles

Abstract

The da Vinci Surgical System offers a natural user interface and wrist articulation, which enable suturing and other complex surgical actions in confined spaces. However, both the one-time cost of the system and the recurring cost of the limited-use instruments remain high. This has motivated the development of several hand-held alternatives-some partially motorized, some fully mechanical-in recent years. While a few of these have been commercialized, none have yet met with broad commercial success comparable to the da Vinci robot. In this letter, we suggest a user interface-based explanation for this, and describe a new mechanical instrument that provides wrist articulation with a novel user interface. We provide results of a single-user pilot study with an experienced laparoscopic surgeon to compare the new device with a traditional wristless laparoscopic tool, a prior commercial wristed mechanical tool (the RealHand), and the da Vinci robot, in the context of suturing at challenging angles. We observe better targeting of desired suture needle entry and exit points with the new device in comparison to prior wristed and wristless mechanical instruments, with the da Vinci only slightly outperforming the new tool.

Keywords: Medical Robots and Systems; Surgical Robotics: Laparoscopy.

Fig. 1

The da Vinci robot user interface maps motion of control points located between the user’s fingers to corresponding control points on the instruments inside the patient. Image source: http://www.intuitivesurgical.com/, control point illustrations added.

Fig. 2

A comparison of control point location for ⓐ the new tool described in this letter, ⓑ the RealHand, ⓒ the Radius, and ⓓ the FlexDex instrument. The new tool is the only one that places the control point within the user’s grasp as the da Vinci robot’s user interface does.

Fig. 3

The dexterous tool, showing distal wrist (left), proximal wrist (right), and handle. The control point (see Fig. 2 for control point illustration) is between the thumb and forefinger, and the end effector grippers are closed by squeezing the handle.

Fig. 4

Control point mapping: axes of rotation in the proximal wrist joint (left) are mapped to the distal wrist joint (right).

Fig. 5

The distal wrist (right) provides articulation similar the da Vinci EndoWrist (left) [20]. Cables are not shown; routing is illustrated in Fig. 6.

Fig. 6

Side and top section views of the distal wrist mechanism, showing ➀ one set of end effector gripper cables, ➁ lateral wrist cables, ➂ rod, ➃ cable guide, ➄ lateral wrist pulley, ➅ pins, ➆ end effector gripper pulleys, ➇ end effector grippers, and control axes. Cable management is addressed via the grooves shown in Fig. 5 (right).

Fig. 7

Side and section views of handle mechanism, showing ➀ linkage connecting pulley arms to handle, ➁ pulley arms, ➂ proximal wrist, ➃ vent screw, ➄ center pulley, ➅ cable guide, ➆ rod, ➇ cables for one gripper of end effector, ➈ cables for end effector lateral wrist pulley, and control axes.

Fig. 8

Dexterous tool handle, showing ➀ grasp locking mechanism, ➁ Z-bar mechanism, ➂ lock release button, and ➃ lock disable switch.

Fig. 9

Surgical tool angles for suturing experiment, showing the dexterous tool throwing sutures at ⓐ 0°, ⓑ 45°, and ⓒ 90° angles.

Fig. 10

Results of suturing experiment at three tool angles for, from top to bottom, the traditional laparoscopic tool, the RealHand, the dexterous tool, and the da Vinci robot. The subject was unable to complete the 90° suture with the RealHand.