Intra-articular joint replacement and method
Methods of implanting a prosthesis to repair a joint include displacing a first bone from the joint formed by an intersection between the first bone and a second bone. An end portion of the first bone is resected to define a resected end. A concavity is formed into the resected end using a shaping tool. The bone is compacted to form a support layer lining the concavity. The prosthesis is implanted in the concavity against the support layer without attaching the prosthesis to the support layer. The joint is reformed with the prosthesis such that the prosthesis remains unattached to the support layer and the first and second bones articulate about the prosthesis.
1. A method of implanting a prosthesis to repair a joint, the method comprising:
dislocating a first bone from the joint formed by an intersection between the first bone and a second bone;
resecting an end portion of the first bone to define a resected end;
forming a concavity into the resected end using a shaping tool;
compacting bone to form a support layer lining the concavity;
implanting the prosthesis in the concavity against the support layer without attaching the prosthesis to the support layer, the prosthesis including a first surface and a second surface opposite the first surface, each of the first and second surfaces being substantially convex in shape;
reforming the joint with the prosthesis such that the prosthesis remains unattached to the support layer and the first and second bones articulate about the prosthesis.
2. The method of claim 1 , further comprising:
selecting a transverse measurement of the resected end by measuring a plurality of transverse dimensions of the resected end and selecting a smallest one of the plurality of transverse dimensions; and
selecting a desired depth of the concavity using the transverse measurement of the resected end.
3. The method of claim 2 , wherein selecting the desired depth of the concavity using the transverse measurement of the resected end includes subtracting a cortical bone thickness from the transverse dimension.
4. The method of claim 1 , wherein the resected end of the first bone defines a resection plane, the method further comprising selecting a desired depth of the concavity, including:
selecting an implant size based upon an assessment of the joint, the implant size including an implant radius;
determining a desired projection height of the implant above the resection plane; and
calculating the desired depth of the concavity relative to the resection plane by adding to the implant radius an amount corresponding to the implant radius minus the desired projection height.
5. The method of claim 1 , wherein the shaping tool includes a demarcation line and further wherein forming the concavity into the resected end using the shaping tool includes inserting the shaping tool into the resected end up to the demarcation line.
6. The method of claim 5 , wherein the demarcation line is at a position on the shaping tool that corresponds to a diameter of the prosthesis minus a predicted projection height of the prosthesis above the resected end that promotes adequate tensioning of the joint.
7. The method of claim 1 , wherein the shaping tool has a forming surface that extends through at least a hemispherical arc and further wherein forming the concavity into the resected end using the shaping tool includes forming a recess that includes a fully-hemispherical portion.
8. The method of claim 1 , wherein the shaping tool is a compactor having a substantially convex compacting surface including a hemispherical portion and an upswept portion extending beyond the hemispherical portion.
9. The method of claim 1 , wherein the shaping tool is a reamer having a substantially convex cutting surface including a hemispherical portion and an upswept portion extending beyond the hemispherical portion.
10. The method of claim 1 , further comprising inserting a test prosthesis into the concavity prior to inserting the prosthesis into the concavity to test expected joint mobility.
11. The method of claim 10 , wherein the test prosthesis includes a test depth line and inserting the prosthesis into the concavity includes inserting the test prosthesis to the test depth line.
12. The method of claim 10 , wherein the test prosthesis has a receptacle for securing the test prosthesis to a handle, the method further comprising securing the handle to the test prosthesis and removing the test prosthesis from the concavity with the handle before positioning the prosthesis in the concavity.
13. The method of claim 10 , wherein the test prosthesis includes indicia and the shaping tool includes indicia, the indicia of the test prosthesis and the forming tool corresponding to a size of the prosthesis, the method further comprising selecting the shaping tool and the test prosthesis using the indicia.
14. The method of claim 13 , wherein the indicia of the forming tool and the test prosthesis includes color coding.
15. The method of claim 1 , wherein the joint is a glenohumeral joint, the first bone is a humerus, and compacting bone to form a support layer lining the concavity includes compacting metaphyseal bone of the humerus.
16. The method of claim 1 , wherein reforming the joint with the prosthesis includes directly contacting the first and second bones with the prosthesis and articulating the first and second bones about the prosthesis.
17. The method of claim 1 , wherein the prosthesis is a spheroid having a radius and implanting the prosthesis in the concavity includes implanting the prosthesis to a depth relative to the resected end that is greater than the radius of the spheroid.
18. The method of claim 1 , wherein the prosthesis includes an internal hollow portion.