Medical instrument and procedure

A medical instrument for preparing a proximal end of a femur to receive a prosthesis having attached anti-rotation lug, the femur having a partially prepared canal with a countersunk frustoconical seat for receiving a trochanteral portion of the prosthesis, the instrument comprising:

• a frame having two spaced frame portions;
• a post attached to one of the frame portions and defining a reference axis;
• a tool guide attached to the other of the frame portions and defining a tool axis fixed at a precise angle with respect to the reference axis;
• a rotary milling cutter operatively disposed in the tool guide configured to advancing move along the tool axis;
• a plurality of spaced collars extending from the tool guide and each of the collars having a radial entrance slot for receiving the rotary milling cutter laterally of the tool axis;
• and
• fixture means extending from the post configured to attach to the countersunk frustoconical seat in the partially prepared canal in the femur to locate the reference axis in relation to the prepared canal so that the tool guide and the cutting axis are set at the precise angle for guiding the cutting tool in the partially prepared canal to accommodate the anti-rotation lug of the prosthesis when implanted in the femur with the trochanteral portion of the prosthesis seated in the countersunk frustoconical seat.

A medical instrument for preparing a proximal end of a femur to receive a prosthesis having an attached anti-rotation lug, comprising:

• a frame having two spaced frame portions;
• a post attached to one of the frame portions and defining a reference axis;
• the post including an external screw thread;
• the post including at least one flat interrupting the screw thread;
• a tool guide attached to the other of the frame portions and defining a cutting axis fixed at a precise angle with respect to the reference axis;
• fixture means extending from the post configured to attach to a frustoconical seat in a partially prepared canal in the femur to locate the reference axis in relation to the prepared canal so that the tool guide and the cutting axis are set at the precise angle for guiding a rotary cutting tool in the partially prepared canal to accommodate the anti-rotation lug of the prosthesis when implanted in the femur;
• bearing block means disposed in the collar configured to prevent rotation of the post with respect to the collar;
• an adjustment nut rotatably mounted in the collar and threadably engaging the screw thread of the post for moving the post in the axial direction during rotation of the adjustment nut and wherein said post is disposed in sliding contact with the bearing block means.

A medical instrument for preparing a proximal end of a femur to receive a prosthesis having an attached anti-rotation lug, comprising:

• a frame having two spaced frame portions;
• a post attached to one of the frame portions and defining a reference axis;
• the post including an external screw thread;
• a tool guide attached to the other of the frame portions and defining a cutting axis fixed at a precise angle with respect to the reference axis;
• fixture means extending from the post configured to attach to a frustoconical seat in a partially prepared canal in the femur to locate the reference axis in relation to the prepared canal so that the tool guide and the cutting axis are set at the precise angle for guiding a rotary cutting tool in the partially prepared canal to accommodate the anti-rotation lug of the prosthesis when implanted in the femur;
• bearing block means disposed in the collar configured to prevent rotation of the post with respect to the collar;
• an adjustment nut rotatably mounted in the collar and threadably engaging the screw thread of the post for moving the post in the axial direction during rotation of the adjustment nut;
• and
• means for locating the post in a plurality of preselected axial positions with respect to the collar.