Device and method for positioning an eccentric humeral head of a humerus prosthesis for a shoulder arthroplasty

1. A prosthesis implantation method. comprising the steps of:

(a) positioning a trial assembly in a resected bone, said trial assembly including a trial body portion having a trial bore defined therein, and a trial head portion having (i) a trial head member which includes a trial offset indicia, and (ii) an eccentrically located trial head stem extending from said trial head member, said trial head stem being configured to be received within said trial bore;

(b) rotating said trial head portion relative to said trial body portion while said trial assembly is positioned in said resected bone so as to position said trial head portion relative to said trial body portion at an aligned orientation in which said trial head portion covers a resected surface of said resected bone;

(c) removing said trial assembly from said resected bone after step (b);

(d) positioning said trial assembly in a scale mechanism having a plurality of distinct values displayed thereon after step (c), said trial offset indicia of said trial head portion being aligned with one of said plurality of distinct values displayed on said scale mechanism in response to step (d);

(e) securing a final head portion to a final body portion based on said one of said plurality of distinct values after step (d) so as to form a final prosthesis assembly; and

(f) implanting said final prosthesis assembly in said resected bone after step (e),

wherein said scale mechanism includes an indicia surface, and

wherein said plurality of distinct values are displayed on said indicia surface, and

wherein said scale mechanism includes a channel defined therein, and step (d) includes the step of locating said trial body portion within said channel.

2. The method of claim 1 , further comprising the step of securing said trial head portion to said trial body portion when said trial head portion is positioned relative to said trial body portion at said aligned orientation.

3. The method of claim 2 , wherein:

said trial body portion includes a set of internal threads located within said trial bore,

said trial head portion further includes an externally threaded fastener positioned within a passageway which extends through said trial head portion, and

said securing step includes the step of advancing said externally threaded fastener into meshing engagement with said set of internal threads so as to secure said trial head portion in fixed relation to said trial body portion.

4. The method of claim 1 , wherein:

said trial body includes (i) a trial body stem, (ii) a neck attached to said trial body stem, and (iii) a flat attached to said neck, and

said trial bore extends through said flat and into said neck.

5. The method of claim 1 , wherein:

said indicia surface is divided into a plurality of sections, and

said one of said plurality of distinct values is identified on one of said plurality of sections.

6. The method of claim 1 , wherein:

said trial body portion locating step includes the step of locating said trial head portion adjacent to said indicia surface.

7. The method of claim 1 , wherein said final head portion includes (i) a final head member having a final offset indicia, and (ii) an eccentrically located final head stem extending from said final head member.

8. The method of claim 7 , wherein:

said final head stem possesses a male taper configuration,

said final body portion has a final bore defined therein,

said final bore possesses a female taper configuration, and

said securing step includes the step of advancing said final head stem into said final bore in a friction fit manner.

9. The method of claim 1 , wherein said resected bone is a resected humerus.

10. A prosthesis implantation method, comprising the steps of:

(a) positioning a trial assembly in a resected bone, said trial assembly including a trial body portion having a trial bore defined therein, and a trial head portion having (i) a trial head member which includes a trial offset indicia. and (ii) an eccentrically located trial head stem extending from said trial head member, said trial head stem being configured to be received within said trial bore;

(b) rotating said trial head portion relative to said trial body portion while said trial assembly is positioned in said resected bone so as to position said trial head portion relative to said trial body portion at an aligned orientation in which said trial head portion covers a resected surface of said resected bone;

(c) removing said trial assembly from said resected bone after step (b);

(d) positioning said trial assembly in a scale mechanism having a plurality of distinct values displayed thereon after step (c), said trial offset indicia of said trial head portion being aligned with one of said plurality of distinct values displayed on said scale mechanism in response to step (d);

(e) securing a final head portion to a final body portion based on said one of said plurality of distinct values after step (d) so as to form a final prosthesis assembly; and

(f) implanting said final prosthesis assembly in said resected bone after step (e),

wherein said final head portion includes (i) a final head member having a final offset indicia, and (ii) an eccentrically located final head stem extending from said final head member,

wherein said scale mechanism includes an indicia surface,

wherein said one of said plurality of distinct values is indicated on said indicia surface,

wherein said scale mechanism further includes a channel defined therein, and

wherein said securing step includes locating said final body portion within said channel.

11. The method of claim 10 , wherein said securing step further includes locating said final head portion adjacent to said indicia surface.

12. The method of claim 11 , wherein said securing step further includes positioning said final head portion relative to said final body portion at said aligned orientation.

13. The method of claim 12 , wherein said step of positioning said final head portion relative to said final body portion includes the step of aligning said final offset indicia with said one of said plurality of distinct values identified on said indicia surface.

14. A prosthesis implantation method, comprising the steps of;

(a) positioning a trial assembly in a resected bone, said trial assembly including a trial body portion having a trial bore defined therein, and a trial head portion having (i) a trial head member which includes a trial offset indicia. and (ii) an eccentrically located trial head stem extending from said trial head member. said trial head stem being configured to be received within said trial bore;

(b) rotating said trial head portion relative to said trial body portion while said trial assembly is positioned in said resected bone so as to position said trial head portion relative to said trial body portion at an aligned orientation in which said trial head portion covers a resected surface of said resected bone:

(c) removing said trial assembly from said resected bone after step (b);

(d) positioning said trial assembly in a scale mechanism having a plurality of distinct values displayed thereon after step (c). said trial offset indicia of said trial head portion being aligned with one of said plurality of distinct values displayed on said scale mechanism in response to step (d);

(e) securing a final head portion to a final body Dortion based on said one of said plurality of distinct values after step (d) so as to form a final prosthesis assembly; and

(f) implanting said final prosthesis assembly in said resected bone after step (e),

wherein said final head portion includes (i) a final head member having a final offset indicia, and (ii) an eccentrically located final head stem extending from said final head member,

wherein said trial offset indicia includes a notch defined in a surface of said trial head member, and

wherein said final offset indicia includes a removable sticker positioned on said final head member.