A new fluoroscopy-free navigation device for distal interlocking screw placement

During the treatment of tibia fracture with interlocking nails, the most uncomfortable procedure is for an orthopaedic surgeon to find the location for the distal locking screws. In this study, a fluoroscopy-free non-contact navigation device was developed for the placement of distal locking screws in the tibia intramedullary nailing. This device utilizes a 3D digitization arm integrated with spatial coordinate registration module, graphical user interface module and sound-guided navigation module. The 3D digitization arm, a five-DOF passive robotic arm, was used to register the spatial coordinates of proximal and distal landmarks just before placement of the nail. The registered coordinates were then incorporated with the coordinates of the proximal landmarks after nail placement to calculate the coordinate transformation matrix. The transformed spatial coordinates of the distal screw holes were then computed in real time for interlocking nail navigation. A sound-guided navigation module was designed in which a sound with different tones and intermittence frequencies was produced, as the probe of the digitization arm navigates toward the location of distal screw holes. No intra-operative fluoroscopy was required. In vitro assessment was performed successfully with a donor bone, and a clinical case of a young male with tibia fracture was also carried out in the operating theatre. Operation time, distal screw insertion, total radiation time and accuracy of the distal interlocking screw placement were measured. The surgery was conducted under sterile conditions without complication, and the clinical course was smooth with prompt bone healing.