Implant trial head

1. An implant trial head, comprising:

an exterior surface;

a distal end;

a proximal end including an opening in the exterior surface;

a cavity in the implant trial head and configured to receive a taper portion of a femoral stem component, the cavity extending from the opening into the implant trial head, the cavity comprising an interior surface defining portions of the cavity including:

a first cavity portion having a distal end and a proximal end;

a second cavity portion having a distal end and a proximal end, the first cavity portion and second cavity portion configured to receive the taper portion of the femoral stem component;

a third cavity portion having a distal end, a proximal end, and a height defined between the proximal end and the distal end, the third cavity portion positioned between the first and second cavity portions such that the proximal end of the third cavity portion is adjacent to the distal end of the first cavity portion, and the distal end of the third cavity portion is adjacent to the proximal end of the second cavity portion, and the third cavity portion tapering outward from the proximal end to the distal end such that a diameter of a cross-section of the third cavity portion increases from the proximal end to the distal end; and

an O-ring positioned laterally in the third cavity portion such that the O-ring contacts the interior surface in the third cavity portion, a diameter of the O-ring being less than the height of the third cavity portion allowing movement of the O-ring between the proximal end of the third cavity and the distal end of the third cavity as the taper portion the femoral stem component is inserted into the trial head.

2. The implant trial head of claim 1 , wherein the height of the third cavity portion from the proximal end to the distal end is between about 0.01 inches and about 0.3 inches.

3. The implant trial head of claim 1 , wherein the height of the third cavity portion from the proximal end to the distal end is between about 0.125 inches and about 0.165 inches.

4. The implant trial head of claim 1 , wherein the height of the third cavity portion from the proximal end to the distal end is about 0.145 inches, plus or minus 0.1 inches.

5. The implant trial head of claim 1 , wherein the diameter of the O-ring is between about 0.05 inches and about 0.3 inches.

6. The implant trial head of claim 1 , wherein the diameter of the O-ring is between about 0.08 inches and about 0.13 inches.

7. The implant trial head of claim 1 , wherein the diameter of the O-ring is about 0.103 inches plus or minus 5%.

8. The implant trial head of claim 1 , wherein the interior surface of the third cavity portion includes a tapered wall having an angle of about 30 degrees, plus or minus 5 degrees, with respect to a longitudinal axis of the implant trial head, the tapered wall angling away from the longitudinal axis as it extends from the proximal end of the third cavity portion towards the distal end of the third cavity portion.

9. The implant trial head of claim 1 , wherein the interior surface of the third cavity portion includes a tapered wall having an angle of between about 1 degrees and 60 degrees with respect to the longitudinal axis of the implant trial head, the tapered wall angling away from the longitudinal axis as it extends from the proximal end of the third cavity portion towards the distal end of the third cavity portion.

10. The implant trial head of claim 1 , wherein the interior surface of the third cavity portion includes a tapered wall having an angle of between about 20 degrees and 40 degrees with respect to the longitudinal axis of the implant trial head, the tapered wall angling away from the longitudinal axis as it extends from the proximal end of the third cavity portion towards the distal end of the third cavity portion.

11. The implant trial head of claim 1 , wherein the interior surface of the third cavity portion includes a tapered wall having an angle with respect to the longitudinal axis of the implant trial head, the tapered wall angling away from the longitudinal axis as it extends from the proximal end of the third cavity portion towards the distal end of the third cavity portion allowing the O-ring to contact the tapered wall and move along the tapered wall from the proximal end of the third cavity portion towards the distal end of the third cavity portion when the tapered portion inserted into the implant trial head.

12. The implant trial head of claim 11 , wherein the third cavity portion comprises a curved distal surface on the distal end of the third cavity portion, and a curved proximal surface on the proximal end of the third cavity portion, wherein the tapered wall is positioned between the curved distal surface and the curved proximal surface.

13. The implant trial head of claim 1 , wherein the first cavity portion and the second cavity portion have cross-sectional diameters that are aligned and sized to define a receiving portion of the cavity to receive the taper portion of a femoral stem component such that the taper portion can extend through the first, second, and third cavity portion, and the third cavity portion and the O-ring are sized such that the O-ring can expand outward at the distal end of the third cavity farther than it can expand outward at the proximal end of the third cavity portion.

14. An implant trial head, comprising:

an exterior surface;

a distal end;

a proximal end including an opening in the exterior surface; and

a cavity extending into the implant trial head from the opening, the cavity comprising an asymmetric groove aligned substantially perpendicular to a longitudinal axis extending from the proximal end to the distal end of the implant trial head,

wherein the cavity extending into the implant trial head from the opening is further comprised of a first cavity portion, a second cavity portion, and a third cavity portion positioned between the first cavity portion and the second cavity portion, and

wherein the third cavity portion further comprises a distal end, a proximal end, and a height defined between the proximal end and the distal end, and wherein a diameter of an O-ring is less than height of the third cavity portion.

15. The implant trial head of claim 14 , wherein the asymmetric groove is positioned within the third cavity portion.

16. The implant trial head of claim 14 , wherein the cavity further comprises a circumferential angled wall defining a diameter of cross-sections of at least a portion of the cavity, the cross-sections aligned perpendicular to a longitudinal axis of the cavity.

17. The implant trial head of claim 16 , wherein the angled wall is aligned such that a diameter of a cross-section of the asymmetric groove of the cavity at the proximal end is less than a diameter of a cross-section of the asymmetric groove of the cavity at the distal end.