Instrument for preparing an implant support surface and associated method

1. An instrument assembly for preparing a surface of a joint, the surface adapted for receiving a glenoid component having a feature closely conforming to the glenoid surface, the prosthetic component providing a bearing surface for a portion of a long bone, the instrument assembly comprising:

a guide having a housing, a base and a restraining component, said base including a convex lower surface sized and shaped to be seated in the prepared joint surface and the restraining component operably associated with said base, the restraining component being pivotably and removably coupled to the housing, the housing including a pintle and the restraining component including a bearing having a u-shaped slot, wherein the pintle slidably fits within the u-shaped slot; and

a tool for cooperation with the housing for preparing the surface, the housing adapted to at least partially control the position of the tool as it prepares the surface, the base adapted to assist in positioning of the guide with respect to the joint.

2. An instrument assembly as in claim 1 , wherein the base of said guide further comprises a pin.

3. An instrument assembly as in claim 1 :

wherein the housing of said guide is defined by a wall in said guide forming a cylindrical opening; and

wherein said tool comprises a rotatable tool fitted to the cylindrical opening.

4. An instrument assembly as in claim 1 , wherein said tool comprises a milling tool.

5. An instrument assembly as in claim 1 , wherein said base further comprises a protrusion extending from the convex lower surface for cooperation with the joint.

6. An instrument assembly as in claim 1 , wherein said bearing defines a bearing centerline of rotation and wherein said centerline is generally parallel to the convex surface of said base.

7. An instrument assembly as in claim 1 , further comprising a handle for positioning the guide with respect to the joint.

8. An instrument assembly for preparing a feature on a scapula, the feature adapted for receiving an augmented glenoid component for providing a bearing surface for a head portion of a humerus, the instrument assembly comprising:

a guide including a housing, a base and a restraining component, the base including a convex lower surface sized and shaped to be seated in the prepared joint surface and the restraining component operably associated with said base, the restraining component being pivotably and removably coupled to the housing, the housing including a pintle and the restraining component including a bearing having a u-shaped slot, wherein the pintle slidably fits within the u-shaped slot; and

a tool for cooperation with the housing for preparing the glenoid surface, the housing adapted to at least partially guide the tool as it prepares the feature, the base adapted to assist in locating the guide with respect to the scapula.

9. An instrument assembly as in claim 8 :

wherein the housing of said guide is defined by a wall in said guide forming a cylindrical opening; and

wherein said tool comprises a rotatable tool fitted to the cylindrical opening.

10. An instrument assembly as in claim 8 , wherein said tool comprises a milling tool.

11. An instrument assembly as in claim 8 , wherein said base further comprises a protrusion extending from the convex lower surface for cooperation with the scapula.

12. An instrument assembly as in claim 8 , wherein said bearing defines a bearing centerline of rotation and wherein said centerline is generally parallel to the convex surface of said base.

13. An instrument assembly as in claim 8 , further comprising a handle for positioning the guide with respect to the glenoid fossa.