Patent ID: 8615286

Claim:
Apparatus for determining the position, in three dimensional space, of a bone covered by soft tissue, said apparatus comprising: a needle having a tip for penetrating soft tissue; position-determining means for determining the position of said tip of said needle in three-dimensional space; force-sensing means for sensing the level of force encountered by said tip of said needle; discriminating means for determining the rate of change in the level of force encountered by said tip of said needle in relation to the distance travelled by said needle so as to discriminate between (i) when said tip of said needle is engaging soft tissue, and (ii) when said tip of said needle is engaging bone; recording means for recording the position of said tip of said needle in three dimensional space when said discriminating means indicate that said tip of said needle is engaging bone; and processing means for receiving a plurality of data points from said recording means and, using the plurality of data points from said recording means, determining the position, in three dimensional space, of a bone covered by soft tissue.