Instrument for use in a joint replacement procedure

1. An instrument for locating the cutting plane on the head of a long bone in a surgical procedure wherein the head of the bone is replaced with a joint prosthesis component, the long bone having an axis, comprising:

an axial reference shaft arranged parallel to the axis of the long bone;

a cutting guide movable relative to the axial reference shaft in a direction parallel to the axis of the long bone, the cutting guide comprising a reference block configured to be located against the lateral edge of the bone, and at least one arm shaped so that, when the reference block is positioned against the lateral edge of the bone, the at least one arm extends from the cutting guide over the face of the head and contacts the head; and

wherein the at least one arm has a distal end, and the distal end contacts a medial edge of the bone when the reference block is positioned against the lateral edge of the bone.

2. The instrument of claim 1 , wherein the at least one arm has a lip provided on the distal end of the arm and the lip contacts the medial edge of the bone when the reference block is positioned against the lateral edge of the bone.

3. The instrument of claim 1 , wherein the at least one arm and the reference block are together moveable relative to the axial reference shaft.

4. The instrument of claim 1 , wherein the at least one arm is slidable relative to the cutting guide.

5. The instrument of claim 1 , wherein the at least one arm includes an approximately straight portion that extends from the cutting guide and a curved portion that extends from the straight portion towards the medial edge of the bone when the reference block is positioned against the lateral edge of the bone.

6. The instrument of claim 1 , wherein the reference block defines a reference block plane and the arm extends from the cutting block in an arm plane that is substantially parallel to the reference block plane, and the distance between the reference block plane and the arm plane is a defined distance.

7. The instrument of claim 6 , wherein the defined distance ranges from approximately 15 mm to 21 mm.

8. The instrument of claim 1 , wherein the at least one arm is shaped so that, when the reference block is positioned against the lateral edge of the bone, the at least one arm extends from the cutting guide over the face of the head and contacts the superior surface of the head.

9. The instrument of claim 1 , further comprising a first arm and a second arm, each of which have a distal end, and wherein the first arm and the second arm are connected to the cutting guide at spaced-apart locations and, when the reference block is positioned against the lateral edge of the bone, each of the first arm and the second arm extends from the cutting guide over the superior face of the head of the bone and at least one distal end of the first and second arm contacts a medial edge of the bone.

10. The instrument of claim 1 , further comprising a clamp for locking the cutting guide against movement relative to the axial reference shaft.

11. The instrument of claim 1 , wherein the reference block has features that are in or parallel to the intended cutting plane.

12. The instrument of claim 11 , wherein the reference block has bores formed therein to define the locations of holes in the long bone to fasten a resection guide block.

13. The instrument of claim 11 , wherein the reference block has a surface that corresponds to the cutting plane when the block is properly aligned relative to the head of the bone.

14. The instrument of claim 6 , wherein the axial reference shaft is connected on one end to the reference block and is movable relative to the intramedullary element in a direction parallel to the axis of the long bone.

15. The instrument of claim 1 , wherein the cutting guide further comprises a mounting block, and wherein the at least one arm is slidably attached to the mounting block in a direction that is not parallel to the axis of the long bone, and the shaft is slidable attached to the mounting block in a direction parallel to the axis of the long bone.

16. An instrument for locating the cutting plane on the head of a long bone in a surgical procedure wherein the head of the bone is replaced with a joint prosthesis component, the long bone having an axis, comprising:

an axial reference shaft arranged parallel to the axis of the long bone;

a cutting guide movable relative to the axial reference shaft in a direction parallel to the axis of the long bone, the cutting guide comprising a reference block configured to be located against the lateral edge of the bone, and at least one arm shaped so that, when the reference block is positioned against the lateral edge of the bone, the at least one arm extends from the cutting guide over the face of the head and contacts the head; and

wherein the reference block defines a reference block plane and the arm extends from the cutting block in an arm plane that is substantially parallel to the reference block plane, and the distance between the reference block plane and the arm plane is a defined distance.

17. The instrument of claim 16 , wherein the defined distance ranges from approximately 15 mm to 21 mm.

18. The instrument of claim 16 , wherein the axial reference shaft is connected on one end to the reference block and is movable relative to the intramedullary element in a direction parallel to the axis of the long bone.

19. An instrument for locating the cutting plane on the head of a long bone in a surgical procedure wherein the head of the bone is replaced with a joint prosthesis component, the long bone having an axis, comprising:

an axial reference shaft arranged parallel to the axis of the long bone;

a cutting guide movable relative to the axial reference shaft in a direction parallel to the axis of the long bone, the cutting guide comprising a reference block configured to be located against the lateral edge of the bone, and at least one arm shaped so that, when the reference block is positioned against the lateral edge of the bone, the at least one arm extends from the cutting guide over the face of the head and contacts the head;

a first arm and a second arm, each of which have a distal end, and wherein the first arm and the second arm are connected to the cutting guide at spaced-apart locations and, when the reference block is positioned against the lateral edge of the bone, each of the first arm and the second arm extends from the cutting guide over the superior face of the head of the bone and at least one distal end of the first and second arm contacts a medial edge of the bone.