Development Of A Surgical Robot System For Long Bone Fractures

Part I Development and primary test of robot for long bone fracture reductionObjective To develop a nova] reduction robot for femoral shaft intramedullary nailing procedure, and carry out primary test to validate its accuracy.Methods Bone-robot interface, safe zone of surgical approach for femoral intramedullary nailing procedure and biomechanical demand for reduction robot were analyzed, a parallel-serial hybrid reduction robot based on Stewart platform was introduced. Passive photoelectric navigation system (Micron Tracker) was adopted to perform point cloud registration. Versatile safe strategies were integrated into the robot system to avoid iatrogenic injury to the patients. Error of point cloud registration was analyzed with 3-D printed femur phantoms and porcine rear leg bone respectively, and then accuracy of robot was test by simulative reduction with synthetic synbones.Results 3-D printed femur phantoms test showed that error of point cloud registration was 1.02±0.81 mm for proximal femur and 1.13±0.97mm for distal femur. Porcine rear leg bone test showed that error of point cloud registration was 1.52±1.81mm for proximal segment and 1.73±1.67mm for distal segment. Accuracy test of robot showed that the residual reduction error was 2.2±1.4mm for axial displacement,2.7±1.9mm for lateral displacement,1.9±2.1°for varus-valgus deformity,1.2±1.6°orantecurvature-recurvature deformity, and 1.7±1.8°for axial rotation.Conclusion The reduction robot system was validated to present reasonable mechanical structure, reliable registration strategy and high reduction accuracy. Results of primary test demonstrated that the robot meets with the real clinical demand, and provided an innovative, minimally invasive and precise solution for femoral shaft intramedullary nailing procedure.Part Ⅱ Development of a new distal aiming robot for locking nail fixationObjective To develop a universal aiming robot for intramedullary nail distal interlocking screw placement.Methods Based on Universal Robots arm, we designed a six degree-of-freedom robot system and integrated Micron Tracker as navigation device to achieve spatial coordinates registration between robot, C arm, X-rays and navigation device. Innovative software was developed to process the X-rays, make surgical planning and calculate precise aiming parameters. We simulated the distal locking procedure using synthetic femora, with robot assistance in one group and freehand technique in another. X-rays radiation dosage, total surgical time and failure of guidewire placement were compared between the two groups.Results The X-rays radiation dosage was 3.5±2.1s for robot group and 6.4±1.9s for freehand group (P<0.05). The total surgical time was 15.2±3.8min for robot group and 7.6±2.5minforfreehandgroup(P<0.05).Two guidewires (6.7%) were misplaced in robot group, compared to five misplaced guidewires in freehand group(P<0.05).Conclusion Compared to the widely used freehand technique in routine clinical procedure, the distal aiming robot significantly increased the rate of locking screws placement, and decrease the X-rays radiation dosage. With these advantages, the aiming robot can be a competitive alternative for intramedullary nail distal interlocking screw placement.