Kinematics of a six-dof fixation device for long-bone fracture reduction

This paper presents a kinematic model for the control of a six-degrees-of-freedom (dof) mechanism proposed for long-bone fracture reduction. The mechanism is an evolution of previous mechanisms known as Ilizarov-like fixation devices. These previous mechanisms perform the fracture reduction by following a trial-and-error adjustment procedure that subjects the patient to several x-ray exposures and provides only an approximate positioning of the two segments of the broken bone to be reduced; in fact, the adjustment procedure relies upon a three-dof instead of the six-dof mechanism that would be necessary for the correct reciprocal location of the bone segments. This procedure also makes the success of the reduction highly dependent on the surgeon's skill. This paper exploits the hardware of a previous device and transforms it into a six-dof mechanism. A kinematic model of the six-dof mechanism is presented. The model provides the adjustment parameters that enable the correct mutual location of the two segments of the broken bone. Consequently, the procedure is freed from the trial-and-error modality, and the correct reduction is less dependent on the surgeon's skill. © 2001 John Wiley & Sons, Inc.