TRIAL FEMORAL HEAD PROSTHESIS

Abstract

A trial femoral head for use in a trial fitting of a hip prosthesis, the head having an outer surface and a plurality of cavities configured to mate with a male connection member of a femoral stem component, each cavity having an opening located in the outer surface of the head, each opening being of a different size such that when the male connection member of the femoral stem component is mated with a first cavity it is received at a first depth, and when it is mated with a second cavity it is received at a second depth.

Claims

1. A trial femoral head for use in a trial fitting of a hip prosthesis, the head having an outer surface and a plurality of cavities configured to mate with a male connection member of a femoral stem component, each cavity having an opening located in the outer surface of the head, each opening being of a different size such that when the male connection member of the femoral stem component is mated with a first cavity it is received at a first depth, and when it is mated with a second cavity it is received at a second depth.

2. The trial femoral head of claim 1, wherein each cavity comprises a tapered surface to engage with a tapered male connection member.

3. The trial femoral head of claim 2, wherein a taper angle of the tapered surface of each cavity is the same.

4. The trial femoral head of claim 1, wherein each cavity has a male connection member insertion axis extending inwardly from the opening and wherein the male connection member insertion axis of the first cavity is coaxial with the male connection member insertion axis of the second cavity.

5. The trial femoral head of claim 1, wherein each cavity has a male connection member insertion axis and wherein the male connection member insertion axis of the first cavity is oriented at a non-zero angle relative to the male connection member insertion axis of the second cavity.

6. The trial femoral head of claim 5, wherein the male connection member insertion axis of the first cavity is orthogonal to the male connection member insertion axis of the second cavity.

7. The trial femoral head of claim 2, wherein the tapered surface of the first cavity connects with the tapered surface of the second cavity.

8. The trial femoral head of claim 4, wherein the head further includes a third cavity which has a male connection member insertion axis that is oriented at a non-zero angle relative to the male connection member insertion axis of at least one of the first and second cavities.

9. The trial femoral head of claim 8, wherein the male connection member insertion axis of the third cavity is orthogonal to the male connection member insertion axis of at least one of the first and second cavities.

10. The trial femoral head of claim 8, wherein the third cavity comprises a tapered surface to engage with a tapered male connection member, and wherein the said tapered surface connects with the tapered surface at least one of the first and second cavities.

11. The trial femoral head of claim 8, wherein the head further includes a fourth cavity which has a male connection member insertion axis that is oriented at a non-zero angle relative to the male connection member insertion axis of at least one of the first and second cavities.

12. The trial femoral head of claim 11, wherein the male connection member insertion axis of the fourth cavity is orthogonal to the male connection member insertion axis of at least one of the first and second cavities.

13. The trial femoral head of claim 11, wherein the male connection member insertion axis of the fourth cavity is co-axial with the male connection member insertion axis of the third cavity.

14. The trial femoral head of claim 11, wherein the fourth cavity comprises a tapered surface to engage with a tapered male connection member, and wherein the said tapered surface connects with the tapered surface at least one of the first, second and third cavities.

15. The trial femoral head of any preceding claim, wherein the outer surface is generally spherical.

16. The trial femoral head of claim 4, wherein each opening is substantially flat when viewed in a direction substantially orthogonal to the male connection member insertion axis.

17. A kit comprising first and second trial femoral heads for use in a trial fitting of a hip prosthesis, each head having an outer surface and a plurality of cavities configured to mate with a male connection member of a femoral stem component, each cavity having an opening located in the outer surface of each head, each opening being of a different size such that when the male connection member of the stem component is mated with a first cavity it is received at a first depth, and when it is mated with a second cavity it is received second depth, and wherein the outer surface of the first trial femoral head has a diameter that is different from a diameter of the outer surface of the second trial femoral head.

18-22. (canceled)

Description

DETAILED DESCRIPTION OF THE DRAWINGS

[0049] The invention will now be described, by way of example only, with reference to the following drawings in which:

[0050] FIG. 1 is schematic of a conventional trial femoral head.

[0051] FIG. 2 is a schematic of a first construction of the trial femoral head.

[0052] FIG. 3 is a schematic of a second construction of the trial femoral head.

[0053] FIG. 4 is a schematic of a third construction of the trial femoral head.

[0054] FIG. 5 is a series of perspective and cross-sectional views of a conventional trial femoral head, the first construction of the femoral head shown in FIG. 2 and a fourth construction of the trial femoral head.

[0055] FIG. 6 shows a trial femoral head according to the invention assembled onto a femoral stem component via a first cavity of the head to provide a first neck length.

[0056] FIG. 7 shows the same trial femoral head of FIG. 6 assembled onto a femoral stem component via a second cavity of the head to provide a second neck length.

[0057] Referring now to FIG. 1, there is shown a conventional trial femoral head 10. The trial femoral head has a single cavity 12, shown here in the form of tapered bore. The tapered bore includes a tapered surface 14 which engages with a male tapered connection member at the proximal end of a femoral stem component (not shown). The use of this conventional trial femoral head only allows the surgeon to trial a single neck length. To trial a different neck length, the surgeon must remove this trial femoral head and replace it with a different trial femoral head which has a cavity dimensioned such that when the male tapered connection member is mated with the femoral head it is received at a different depth.

[0058] Referring now to FIGS. 2 to 4, there are shown three different constructions of a multi-cavity femoral head according to the invention.

[0059] FIG. 2 shows a first construction of the trial femoral head 100 which includes a first cavity 112 and second cavity 114. Each cavity is dimensioned for receipt of a male connection member of a femoral stem component (not shown) at a different depth. Each of the first and second cavities has a male connection member insertion axis, X.sub.1 and X.sub.2, respectively that extends inwardly from an opening 116, 118, located in the generally spherical outer surface 120. It is along the male connection member insertion axis of each cavity that the male connection member of the stem component is inserted and removed when the trial femoral head is connected to and disconnected from the stem component. In the construction shown, axis X.sub.1 and X.sub.2 are coaxial.

[0060] The formation of the opening 116, 118 in the outer spherical surface creates an opening that is substantially flat when viewed in a direction substantially orthogonal to the male connection member insertion axis X.sub.1 of the first cavity and the male connection member insertion axis X.sub.2 of the second cavity.

[0061] The opening 118 is larger than the opening 116. Each opening can be substantially circular, although other shapes of openings that are configured to receive a complementary shaped male connection member are envisaged.

[0062] In the construction shown, each of the first and second cavities has a tapered surface 122, 124, respectively. This tapered surface can engage with the tapered male connection member of the femoral stem component. A Morse taper connection can be formed between the assembled components.

[0063] The tapered surface 122 of the first cavity 112 connects with the tapered surface 124 of the second cavity 114. There is not a dividing member (e.g., a wall) between the cavities. An advantage of this inter-connection is that a surgeon can thread a suture through the two cavities, and through adjacent soft tissue. This helps to prevent accidental loss of the trial femoral head within the surgical site.

[0064] In use, a surgeon will be able to use the illustrated dual-cavity trial femoral head to trial two different neck lengths. Insertion of the male connection member into the first cavity will provide a first neck length. As a result of the second cavity having a wider opening than the first cavity, the male connection member can be inserted deeper into the second cavity. This will provide a second neck length, which is shorter than the first neck length.

[0065] FIG. 3 shows a second construction of the trial femoral head 200. This construction is similar to the dual-cavity construction shown in FIG. 1, apart from the relative positioning of the first and second cavities 212, 214. In this second construction, the male connection member insertion axis, X.sub.1 and X.sub.2, of the first and second cavities are generally orthogonal to each other.

[0066] Similar to the first construction of the femoral head, the tapered surface 222 of the first cavity 212 connects with the tapered surface 224 of the second cavity 214. There is not a dividing member (e.g., a wall) between the cavities. An advantage of this inter-connection is that a surgeon can thread a suture through the two cavities, and through adjacent soft tissue. This helps to prevent accidental loss of the trial femoral head within the surgical site.

[0067] FIG. 4 shows a third construction of the trial femoral head 300. This construction includes, a first cavity 312, a second cavity 314, a third cavity 326 and a fourth cavity 328.

[0068] In the construction shown, each of the first to fourth cavities has a tapered surface 322, 324, 330 and 332, respectively. This tapered surface can engage with the tapered male connection member of the femoral stem component. A Morse taper connection can be formed between the assembled components.

[0069] Each of the first to fourth cavities has a male connection member insertion axis, X.sub.1, X.sub.2, X.sub.3 and X.sub.4 that extends inwardly from each opening 316, 318, 334, 336 located in the generally spherical outer surface 320. It is along the male connection member insertion axis of each cavity that the male connection member of the stem component is inserted and removed when the trial femoral head is connected to and disconnected from the stem component. In the construction of the trial femoral head shown in FIG. 4, axis X.sub.1 and X.sub.3 are coaxial, and axis X.sub.2 and X.sub.4 are coaxial. Axis X.sub.1 is generally orthogonal to X.sub.2 and axis X.sub.4. Axis X.sub.3 is generally orthogonal to X.sub.2 and axis X.sub.4.

[0070] The formation of each opening in the spherical outer surface of the trial femoral head creates an opening that is substantially flat when viewed in a direction substantially orthogonal to the male connection member insertion axis X.sub.1, X.sub.2, X.sub.3 and X.sub.4 of each of the first to fourth cavities, respectively.

[0071] Unlike the trial femoral heads shown in FIGS. 2 and 3 the tapered surfaces of the cavities are not connected. Instead, each cavity includes an end wall 338, 340, 342, 344. Each end wall includes an aperture through which a suture may be threaded. A suture channel 346 extends between the aperture of the first cavity and the aperture of the third cavity. A suture channel 348 extends between the aperture of the second cavity and the aperture of the fourth cavity. To secure the trial head to the surgical site, a surgeon may thread a suture through the first cavity 312, along suture channel 346 and then out through the third cavity 326. Alternatively, a surgeon may thread a suture through the second cavity 314, along suture channel 348 and then out through the fourth cavity 328.

[0072] FIG. 5 shows perspective views of (a) the conventional trial femoral head 100 as shown in FIG. 1, (b) the dual-cavity trial femoral head 200 as shown in FIG. 2 and (c) a triple-cavity femoral head 400 according to a further construction of the device. Suture holes 450 are shown in the conventional trial femoral head 100.

[0073] FIG. 5 also shows cross-sectional views of (d) head 100, (e) head 200 and (f) head 400 along Plane A. It can be seen that the tapered surfaces of the plurality of cavities in both head 200 and head 400 are connected. This results in an inter-connection between the cavities.

[0074] The use of a trial femoral head 500 having four cavities to trial up to four different neck lengths is demonstrated in FIGS. 6 and 7. The trialing of two of the four possible neck lengths achievable by using this trial femoral head are shown.

[0075] In FIG. 6 the male connection member 552 of a femoral stem 554 is inserted into a first cavity 512. This cavity has an opening of a first size. The male connection member is inserted into the first cavity at a first depth. In FIG. 7 the same male connection member of the same femoral stem is inserted a second cavity 514. This cavity has an opening that is smaller than the opening of the first cavity. As a result, when the male connection member is inserted into the second cavity it is only insertable to a second depth, this depth being shallower than the first depth. As a result, the use of the second cavity provides an assembly between the trial femoral head and the stem component that has a longer neck length than the assembly formed when the first cavity is used. This variability is provided by a single trial femoral head.