Patent ID: 8303588

Claim:
An external skeletal fixation device comprising: a first pin clamp unit for fixedly holding rodlike members adapted to be inserted into a first part of a bone; a second pin clamp unit for fixedly holding rodlike members adapted to be inserted into a second part of a bone on an opposite side, respectively, of a virtual hinge point corresponding to a center of rotational angulation of the bone, a center on which the first and the second part of the bone respectively on the opposite sides of a fracture site of the bone or an osteotomy site for correction are turned, or a center about which a joint turns; a first arm having a proximal end and a distal end, said distal end being operatively connected to said first pin clamp unit; a second arm having a proximal end and a distal end, said distal end being operatively connected to the second pin clamp unit; and a connecting mechanism connecting the proximal end of the first arm to the proximal end of the second arm; a first shaft operatively connected to either said first pin clamp unit or said distal end of the first arm to turnably connect the first pin clamp unit relative to the first arm, said first shaft having an axis projecting in a direction to extend toward and substantially intersect at the virtual hinge point; a second shaft operatively connected to either the second pin clamp unit or said distal end of the second arm to turnably connect the second pin clamp unit relative to the second arm, said second shaft having an axis projecting in a direction to extend toward and substantially intersect at the virtual hinge point; a connecting shaft being operatively connected to either said proximal end of said first arm or said proximal end of said second arm for pivotally joining the first and second arms together, said connecting shaft including an axis projecting in a direction to extend toward and substantially intersect at the virtual hinge point; wherein an extension from said axis of the first shaft, an extension from the axis of the second shaft and an extension from the axis of the connecting shaft extend towards and substantially intersect at said virtual hinge point; and wherein the first shaft, the second shaft and the connecting shaft include ring parts formed on an end of the first shaft, the second shaft and the connecting shaft and retaining rings positioned on the ends of the first shaft, the second shaft and the connecting shaft to press the ring parts against base parts of the first shaft, the second shaft and the connecting shaft, respectively, worm wheels attached to the first shaft, the second shaft and the connecting shaft and provided with teeth arranged around the circumferences thereof, respectively, and worms supported on end parts of the ring parts so as to extend parallel to tangents to the inner circumferences of the ring parts and engaged with the worm wheels, respectively.