Instrument for use in a joint replacement procedure

1. An instrument for use in a joint replacement procedure involving a bone having an intramedullary cavity, comprising:

a trial head that corresponds to the head of an orthopaedic joint component having an upper curved surface that defines a polar axis and a lower surface, and a bore formed in the lower surface, the bore having a bore axis;

a trial connector for connecting the trial head to a stem part of the orthopaedic joint component that is intended for location in the intramedullary cavity of the bone, wherein the trial connector can be fitted into the bore in the trial head at variable angular orientations; and

a rotating indicator pivotally coupled about the polar axis, the rotating indicator being coupled to the trial connector such that a rotational position of the rotating indicator about the polar axis is indicative of a rotational position of the trial connector within the bore of the trial head;

wherein the bore of the trial head is located eccentrically relative to the polar axis and the trial connector has a center and a recess located eccentrically relative to the center of the trial connector.

2. The instrument of claim 1 , wherein the rotating indicator includes at least one edge arranged to engage the stem part of the orthopaedic joint component such that the rotational position of the rotating indicator about the polar axis is indicative of the rotational position of the trial connector within the bore in the trial head.

3. The instrument of claim 1 , wherein the trial connector comprises a lower surface and the rotating indicator comprises a disc coupled to the lower surface of the trial connector about the polar axis.

4. The instrument of claim 3 , wherein the disc is circular.

5. The instrument of claim 3 , wherein the disc further comprises one of a raised annular portion and a corresponding annular recess extending about the polar axis, and the lower surface of the trial head comprises the other of one of the raised annular portion and the corresponding annular recess, the raised annular portion of one of the disc and the trial head being receivable in the recess of the other of one of the disc and the trial head to pivotally couple the rotating indicator to the lower surface of the trial head about the polar axis.

6. The instrument of claim 1 , wherein the rotating indicator is pivotally coupled to the trial head.

7. The instrument of claim 6 , wherein the rotating indicator further comprises at least first surface extending from near the polar axis towards the trial connector.

8. The instrument of claim 7 , wherein the rotating indicator comprises a pair of parallel surfaces arranged to engage opposite sides of the stem part of the orthopaedic joint component.

9. The instrument of claim 8 , wherein the pair of parallel surfaces comprises sides of a closed slot.

10. The instrument of claim 6 , wherein the rotating indicator is pivotally coupled to the trial head by engagement of at least one portion of the rotating indicator that extends from the lower surface of the trial head with the upper surface of the trial head.

11. The instrument of claim 1 , wherein the trial connector further comprises a skirt portion that extends from the lower surface of the trial head when the trial connector is engaged with the trial head.

12. The instrument of claim 1 , wherein the rotational position of the trial connector in the trial head bore determines the rotational position of the rotating indicator.

13. The instrument of claim 1 , wherein the rotational position of the rotating indicator determines the rotational position of the trial connector in the trial head bore.

14. The instrument of claim 1 , wherein the trial connector recess has a recess axis, and a predetermined point on the rotating indicator is indicative of the eccentricity of the trial head relative to the recess axis.

15. An instrument for use in a joint replacement procedure involving a bone having an intramedullary cavity, comprising:

a trial head that corresponds to the head of an orthopaedic joint component having an upper curved surface that defines a polar axis and a lower surface, and a bore formed in the lower surface, the bore having a bore axis;

a trial connector for connecting the trial head to a stem part of the orthopaedic joint component that is intended for location in the intramedullary cavity of the bone, wherein the trial connector comprises a lower surface and can be fitted into the bore in the trial head at variable angular orientations;

a rotating indicator pivotally coupled about the polar axis, the rotating indicator comprises a disc coupled to the lower surface of the trial connector about the polar axis such that a rotational position of the rotating indicator about the polar axis is indicative of a rotational position of the trial connector within the bore of the trial head; and

wherein the bore of the trial head is located eccentrically relative to the polar axis and the trial connector has a center and a recess located eccentrically relative to the center of the trial connector.

16. The instrument of claim 15 , wherein the disc is circular.

17. The instrument of claim 15 , wherein the disc further comprises one of a raised annular portion and a corresponding annular recess extending about the polar axis, and the lower surface of the trial head comprises the other of one of the raised annular portion and the corresponding annular recess, the raised annular portion of one of the disc and the trial head being receivable in the recess of the other of one of the disc and the trial head to pivotally couple the rotating indicator to the lower surface of the trial head about the polar axis.

18. An instrument for use in a joint replacement procedure involving a bone having an intramedullary cavity, comprising:

a trial head that corresponds to the head of an orthopaedic joint component having an upper curved surface that defines a polar axis and a lower surface, and a bore formed in the lower surface, the bore having a bore axis;

a trial connector for connecting the trial head to a stem part of the orthopaedic joint component that is intended for location in the intramedullary cavity of the bone, wherein the trial connector can be fitted into the bore in the trial head at variable angular orientations; and

a rotating indicator pivotally coupled about the polar axis to the trial head, the rotating indicator being coupled to the trial connector such that a rotational position of the rotating indicator about the polar axis is indicative of a rotational position of the trial connector within the bore of the trial head;

wherein the bore of the trial head is located eccentrically relative to the polar axis and the trial connector has a center and a recess located eccentrically relative to the center of the trial connector; and wherein the rotating indicator further comprises a pair of parallel surfaces that form sides of a closed slot, the pair of surfaces being arranged to engage opposite sides of the stem part.