Development of patch-stabilizer with stabilizing force control for minimally invasive fetal surgery

The clinical target of this study is intrauterine patch coverage of fetal myelomeningocele. We propose a new surgical robotic system for intrauterine fetal surgery with patch-stabilizer and laser manipulator. The target disease of the fetal surgery is spina bifida or myelomeningocele, which is incomplete closure in the spinal column and one of the common fetal diseases. In the fetal surgery, the collagen patch is supposed to be stabilized onto the fragile fetal tissue during the laser fixation process. In this study, a prototype of the patch-stabilizer using wire driven mechanism has been developed for precise force control on the patch without damaging fetal tissue. The diameter of the patch-stabilizer's shaft is 2.4 mm. The patch-stabilizer including one ball joint and wire driven mechanism is able to bend through 40 degrees. The stabilizing part holds collagen patch with diamond shape mechanism using wire driven. In this paper, we showed that the patch-stabilizer was developed with the stabilizing force control using the torque control of ball joint by the driven wires tension control. Results of the experiment showed that the torque of ball joint was controlled at 0.3 N· mm, that the stabilizing force was controlled at 0.15 kPa to stabilize the collagen patch onto the lesion surface without the damages of fetal tissues and the change of fetal attitude in the uterus.