Bone mounted hexapod robot for outpatient distraction osteogenesis

Distraction Osteogenesis with external fixators is widely used to correct bone defects and deformities. The hexapod external fixator is based upon parallel kinematics well-known from high-precision robotics. This allows for fracture movements in all six degrees of freedom without losing stability of fixation. The fixator movements are effected manually by the patient several times a day over the course of healing. Based on the manual hexapod fixator an "intelligent" fixator system has been developed. Effectively, it is a bone mounted robot system for fracture control. By implementation of motors, gears and position sensors a motorized external fixator was accomplished. A permanently mounted microcontroller system allows for autonomous adjustments of the fixator according to the planned six degree of freedom movements of the fracture fragments. Additionally, it will inform the surgeon and the patient about the fracture healing process. The motorized actuators of this system are interchangeable with the manual elements thus allowing easy mounting after the operation. In addition to a small electrical motor, gear head and position sensor each of the actuators contains a microcontroller unit that controls the motor and stores the current length of the actuator. All six actuators are connected by a digital two-wire bus with the central microcontroller system providing energy and position data. Software was developed to perform motor controlled bone movements via a 3D navigation device ("3D mouse"). The movements can be simulated and stored to be executed autonomously later on or can also be effected immediately and observed online on the computer screen. The "intelligent" external fixator will optimize bone healing and increase patient safety and comfort by increasing precision and frequency of the bone movements and preventing maloperation by computer-aided planning and autonomous movements.