Bending Forceps Manipulator with Offset Distance for Single-port Laparoscopy

Toshikazu Kawai , Toshinobu Matsumoto , Atsushi Nishikawa , Yuji Nishizawa , Tatsuo Nakamura
Vol. 5 (2016) p. 56-62

By integrating locally operated, small surgical robots and devices, a surgeon can perform, robotically assisted laparoscopic surgery safely and accurately. However, no locally operated robotic forceps functioning as the third arm can provide the wide field of view and the large working area required for single-incision laparoscopic surgery (SILS). For SILS using a locally operated third arm, the pivot point should be placed far from the other three instruments inserted through the single port, and the pivot axes should be bending. Size reduction of the differential geared mechanism is difficult. Designing bending pivot axes for the flexible worm mechanism is also difficult. Bending pivot axes are also difficult to achieve in the crank-curved manipulator that we proposed previously as the second arm. The crank distance is short because of the high-step cylinders. The curved forceps have low accuracy because of rubber deformation. In the present study, we modified the crank-curved manipulator and designed a new manipulator for use as the third arm in a sterile environment, which provides offset distance using low-step cylinders in the pivot point placed far from the other instruments, as well as bending forceps mechanisms using ball joints in the bending pivot axes. We succeeded to develop a bending forceps manipulator with offset distance as a locally operated, end-effector manipulator (offset LODEM) for use as the third arm. The operating range was 60 mm for the offset, 32° for the pitch and yaw axes, and 24 mm for the insertion/extraction axis. Positional accuracy was evaluated while performing a simulated surgical procedure. The accuracy was 0.5 mm, which is sufficient for handling organs. The manipulator successfully handled the target in the simulated surgical procedures to provide a wide field of view and a large working area. The offset LODEM was designed to allow minimally invasive, robotically assisted surgery performed by a doctor working near the patient. This device may be used for such applications.