The invention relates to an adaptor for tracking an instrument location during image guided surgery. The adaptor has a drive shaft, a proximal handle and a distal instrument tip. The drive shaft has a linear proximal portion, a curved mid-portion and a linear distal portion that is co-linear with the linear proximal portion. Three tracking elements (such as reflective balls) are placed on the sinusoidal portion. When the handle is rotated, the two linear portions remain fixed on the longitudinal axis, but the tracking elements on the sinusoidal portion travel in orbits about the longitudinal axis, thereby allowing a computer to track the location of the instrument tip.