MEASURING EQUIPMENT FOR USE IN CONNECTION WITH HIP PROSTHESIS SURGERY

Abstract

A measuring adapter (1) for a measuring instrument for use in connection with hip prosthesis surgery is provided. The measuring adapter (1) comprises a measuring head (2) and a connector (3); the measuring head (2) comprises a front end (2a), a rear end (2b) and an upper surface (4a). The upper surface (4a) is convex. The measuring head (2), along an axial direction of the measuring adapter (1), further comprises a central through-going bore (5) adapted to receive an actuating rod (8). The measuring head (2) is adapted to expand from a relaxed state to an expanded state when the actuating rod (8) is axially displaced in the central through-going bore (5); and the measuring head (2) is divided into at least two separate sections (6). The connector (3) is hollow and slotted at one end in axial direction of the measuring head (2) into a number of legs (7), the number of legs (7) corresponding to the number of the at least two separate sections (6) of the measuring head (2). The legs (7) of the connector (3) are each connected to one of the at least two separate sections (6) of the measuring head (2) on the rear end (2b) of the measuring head (2). A securing arrangement (18) is provided at the opposite end of the connector (3) relative to the connection to the measuring head (2), and at least a part of the upper surface (4a) of the measuring head (2) is adapted to, in one expanded state, adopt the shape of a spherical cap or a convex shape comprising at least a spherical segment. A measuring adapter (1) is also provided that comprises windows or through-going holes (10) or windows.

Claims

1. A measuring adapter for a measuring instrument for use in connection with hip prosthesis surgery, wherein the measuring adapter comprises a measuring head and a connector; the measuring head comprises a front end, a rear end and an upper surface; wherein the upper surface is convex; the measuring head, along an axial direction of the measuring adapter, further comprises a central through-going bore adapted to receive an actuating rod; the measuring head is adapted to expand from a relaxed state to an expanded state when the actuating rod is axially displaced in the central through-going bore; and the measuring head is divided into at least two separate sections; the connector is hollow and slotted at one end in an axial direction of the measuring head to define a number of legs, the number of legs corresponding to the number of the at least two separate sections of the measuring head; wherein the legs of the connector are each connected to one of the at least two separate sections of the measuring head on the rear end of the measuring head; and a securing arrangement is provided at the opposite end of the connector relative to the connection to the measuring head; at least a part of the upper surface of the measuring head is adapted to, in one expanded state, adopt the shape of a spherical cap; or a convex shape comprising at least a spherical segment.

2. The measuring adapter according to claim 1, wherein the measuring head is adapted, in one expanded state, to adopt the shape of a largely hemispherical surface.

3. The measuring adapter according to claim 1, wherein the measuring head in the relaxed state has the surface of a collapsed hemisphere; the surface of a collapsed spherical cap; or a convex shape comprising at least a collapsed spherical segment.

4. The measuring adapter according to claim 1, wherein the measuring head has a width (w) and a height (h); wherein the width is an ideal width (w) of the measuring head perpendicular to the axial direction of the connector, and the height (h) is a height of the measuring head along the axial direction of the connector; and wherein
h<w/2

5. The measuring adapter according to claim 1, wherein the measuring head in the relaxed state is collapsed compared to a perfect hemisphere and adapted, in one expanded state, to adopt the shape of a largely hemispherical surface.

6. The measuring adapter according to claim 1, wherein the measuring head has at least two radii r1 and r2; wherein r1 is the ideal radius of the measuring head perpendicular to the axial direction of the connector; r2 is the radius of the measuring head as measured along the axial direction of the connector from the intersection of an axis along the axial direction of the connector with the radius r1; and r2 is smaller than r1.

7. The measuring adapter according to claim 5, wherein the measuring head in the relaxed state has a convex shape comprising at least a collapsed spherical segment.

8. The measuring adapter according to claim 1, wherein the measuring head comprises windows or through-going holes.

9. The measuring adapter according to claim 1, wherein the measuring head is divided into at least three separate sections.

10. The measuring adapter according to claim 1, wherein at least a part of the upper surface of the measuring head comprises a rough surface.

11. The measuring adapter according to claim 1, wherein the upper surface of the measuring head of the measuring adapter comprises a rough surface at the lower part of the upper surface and a smooth surface on the upper part of the upper surface.

12. The measuring adapter according to claim 1, wherein the securing arrangement comprises recesses for a bayonet socket.

13. The measuring adapter according to claim 1, wherein the measuring adapter is made of a hard yet flexible material, wherein the material is chosen from the group consisting of a metal alloy, a plastic material, a plastic composite, a ceramic material, and combinations thereof.

14. The measuring adapter according to claim 1, wherein the central through-going bore is conical.

15. The measuring adapter according to claim 1, wherein the diameter of the measuring head in the relaxed state is from 42 to 85 mm.

16. The measuring adapter according to claim 1, wherein the diameter of the measuring head in the fully expanded state is up to 4 mm larger than the diameter of the measuring head in the relaxed state.

17. A measuring adapter for a measuring instrument for use in connection with hip prosthesis surgery, wherein the measuring adapter comprises a measuring head and a connector; the measuring head comprises a front end, a rear end and an upper surface; wherein the upper surface is convex; the measuring head, along an axial direction of the measuring adapter, further comprises a central through-going bore adapted to receive an actuating rod; the measuring head is adapted to expand from a relaxed state to an expanded state when the actuating rod is axially displaced in the central through-going bore; and the measuring head is divided into at least two separate sections; the connector is hollow and slotted at one end in an axial direction of the measuring head into a number of legs, the number of legs corresponding to the number of the at least two separate sections of the measuring head; wherein the legs of the connector are each connected to one of the at least two separate sections of the measuring head on the rear end of the measuring head; and a securing arrangement is provided at the opposite end of the connector relative to the connection to the measuring head; the measuring head comprises windows or through-going holes or windows.

18. A measuring instrument comprising a measuring adapter according to claim 1 and a measuring unit comprising an actuating rod adapted to be received by the central through-going bore of the measuring adapter, wherein a main part of the actuating rod is adapted to interact displaceably axially with the central through-going bore of the measuring adapter and thereby change the diameter of the measuring head, the measuring unit further comprising a mounting ring comprising means for engaging the securing arrangement of the measuring adapter, wherein the mounting ring is connected with a handle means, wherein, in connection with the handle means, means for axial displacement of the actuation rod and registration of the relative displacement of the actuation rod relative to the measuring head is provided.

19. A measuring instrument comprising a measuring adapter according to claim 17 and a measuring unit comprising an actuating rod adapted to be received by the central through-going bore of the measuring adapter, wherein a main part of the actuating rod is adapted to interact displaceably axially with the central through-going bore of the measuring adapter and thereby change the diameter of the measuring head, the measuring unit further comprising a mounting ring comprising means for engaging the securing arrangement of the measuring adapter, wherein the mounting ring is connected with a handle means, wherein, in connection with the handle means, means for axial displacement of the actuation rod and registration of the relative displacement of the actuation rod relative to the measuring head is provided.

20. The measuring adapter according to claim 1, wherein the diameter of the measuring head in the relaxed state is from 50 mm to 70 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0111] By way of example, embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0112] FIG. 1a is a schematic view of a measuring adapter according to the present invention;

[0113] FIG. 1b is a cross sectional view of measuring head of a measuring adapter according to the present invention;

[0114] FIG. 2a is a schematic view of a cross-section of measuring adapter according to the present invention, wherein the measuring head (2) in the relaxed state is collapsed compared to a perfect hemisphere;

[0115] FIG. 2b is a cross sectional view of a measuring adapter according to the present invention, wherein the measuring head in FIG. 2a is in an expanded state;

[0116] FIG. 3a is a schematic view of cross-section of a measuring adapter according to the present invention, wherein the height (h) of the measuring head (2) is less than half of the ideal width (w) of the measuring head (2);

[0117] FIG. 3b is a schematic view of a measuring adapter according to the present invention, wherein the measuring head in FIG. 3a is in an expanded state;

[0118] FIG. 4a is a schematic view of a cross-section of a measuring adapter according to the present invention, wherein the measuring head (2) is in the relaxed state and wherein the measuring head (2) is described by two radiuses r1 and r2;

[0119] FIG. 4b is a schematic view of a cross-section of a measuring adapter according to the present invention, wherein the measuring head (2) is described by two radiuses r3 and r4;

[0120] FIG. 5 is a schematic view of a measuring adapter according to the present invention;

[0121] FIG. 6 is a schematic view of a measuring instrument according to the present invention;

[0122] FIG. 7 shows a cross-section of the interaction between measuring head and actuation rod;

[0123] FIG. 8 shows a cross-section of a metal socket inserted into acetabulum.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0124] One embodiment of the invention will now be described in relation to the figures.

[0125] FIG. 1a shows the measuring adapter 1 which includes a connector 3 and a measuring head 2 having a surface 4c. In the connector 3 there is shown axially extending slots 13 that divide the end 14 of the connector 3 into a number of legs 7. The slot 13 ends in a circular opening 19 that prevents notch effect in the connector 3 when the measuring head 2 expands.

[0126] The measuring head 2 includes a surface 4c which is divided into a number of sections 6 each connected with one of the legs 7 of the connector 3. The surface 4c of the measuring head 2 is divided into two areas with different roughness: bottom part 4a with rough surface and a top part 4a with smooth surface. In FIG. 1a the number of legs 7 is three. The number of sections 6 is three.

[0127] The measuring head has several through-going holes 10 or windows.

[0128] FIG. 1b shows a cross-section in the measuring head 2. Inside the measuring head 2 is provided an axial through-going conical bore 5 which is designed to interact with actuation rod (not shown). In order to bear against and produce some resistance against acetabulum, the surface 4c of the measuring head 2 is divided into a bottom part 4a with a rough surface and a top part 4a with a smooth surface.

[0129] FIG. 2a is a schematic view of a cross-section of a measuring head 2 of a measuring adapter 1, which, in the relaxed state, is collapsed compared to a perfect hemisphere. The measuring head 2 includes a surface 4c which is divided into a number of sections 6 each connected with one of the legs 7 (not shown) of the connector 3. In the relaxed state shown, the sections 6 are collapsed towards the axis A of the measuring head 2 such that the surface 4c is not hemispherical. Specifically, a curve from a point a to a point b, through points a, c and b is not an arc of a circle. Points a and b are located on the outline of the measuring head 2 located on the farthest perpendicular distance from an axis A along the axial direction of the connector 3. Other structures may be located proximal of points a and b, respectively. Points a and b are located on the rim of the central through-going bore 5. Point c is an imaginary point located on the axis a along the axial direction of the connector 3. A line (a-b) intersects the axis in a point d.

[0130] FIG. 2b shows the measuring adapter 1 of FIG. 2a in an expanded state, wherein the surface 4c of the measuring head 2 is hemispherical. Specifically, a curve from a point a to a point b, through points a, b and c is an arc of a circle. Points a and b are located on the outline of the measuring head 2 located on the farthest perpendicular distance from an axis A along the axial direction of the connector 3. Other structures may be located proximal of points a and b, respectively. Points a and b are located on the rim of the central through-going bore 5. Point c is an imaginary point located on the axis A along the axial direction of the connector 3. A line (a-b) intersects the axis in a point d.

[0131] Thus, in an expanded state, the curve (a-a-c-b-b-d-a) encloses a hemi circle. Thus, the distances (a-d), (d-b) and (d-c) are equal.

[0132] In some embodiments, in an expanded state, the surface 4c of the measuring head 2 is not hemispherical, but rather a spherical segment, and the curve (a-a-c-b-b-d-a) encloses a circle segment. Thus, the distances (a-d) and (d-b) are equal, and the distance (d-c) is less than the distance (a-d).

[0133] FIG. 3a is a schematic view of a measuring head 2 of a measuring adapter 1, wherein the height h of the measuring head 2 is less than half of the ideal width w of the measuring head 2. The measuring head 2 has a surface 4c. The measuring head 2 is flattened, such that the surface 4c is not hemispherical and its cross section resembles an elliptical rather than circular geometry.

[0134] FIG. 3b shows the measuring adapter 1 of FIG. 3a in its expanded state, wherein the surface 4c of the measuring head 2 is hemispherical.

[0135] FIG. 4a is a schematic view of a cross-section of a measuring head of a measuring adapter 1, wherein the measuring head 2 is described by two radiuses r1 and r2. It is also possible to describe the measuring head 2 by more than two radiuses, such as 3, 4, or 5 radiuses.

[0136] FIG. 4b is a schematic view of a cross-section of a measuring head of a measuring adapter 1, wherein the measuring head 2 is described by two radiuses r3 and r4. It is also possible to describe the measuring head 2 by more than two radiuses, such as 3, 4, or 5 radiuses.

[0137] FIG. 5 shows schematic views of a measuring head 2 of a measuring adapter 1, wherein the measuring head 2 in the relaxed state is collapsed compared to a perfect hemisphere. The measuring adapter 1 includes a connector 3 and a measuring head 2 having a surface 4c. In the connector 3 there is shown axially extending slots 13 that divide the end 14 of the connector 3 into three legs 7. The slot 13 ends in a circular opening 19 that prevents notch effect in the connector 3 when the measuring head 2 expands.

[0138] The measuring head 2 includes a surface 4c which is divided into three sections 6 each connected with one of the legs 7 of the connector 3. The surface 4c of the measuring head 2 is divided into two areas with different roughness: bottom part 4a with rough surface and a top part 4a with smooth surface. In the relaxed state shown, the sections 6 are collapsed towards the axis of the measuring head 2 such that the surface 4c is not hemispherical.

[0139] The measuring head has several through-going holes 10 or windows.

[0140] FIG. 6 shows a measuring instrument 11 including a measuring adapter 1 and a measuring unit 12.

[0141] The measuring adapter 1 includes a connector 3 and a measuring head 2 that has a surface 4c. The connector 3 has at least two axially extending slots 13 dividing the end 14 of the connector 3 into a number of legs 7. The measuring head 2 includes a hemispherical surface 4c divided into a number of sections 6 so that each part is connected with one leg 7 of the connector 3. At the end 14 of the connector 3 recesses may be provided, which are designed to interact with corresponding pins (not shown) provided in the securing arrangement (e.g. a mounting ring) of the measuring unit 12. Inside the measuring head 2 is provided an axially through-going conical bore 5 which is designed to interact with the actuation rod 8 of the measuring unit 12.

[0142] The measuring unit 12 includes an actuation rod 8, a mounting ring 16 and a millimetre screw device 17. The actuation rod 8 has a conical main part 11 which by axial displacement and engagement with the conical bore 5 in the measuring head 2 forces the separate sections (not shown) of the measuring head 2 from each other. The outward going force caused by the displacement of the actuation rod 8 in relation to the conical opening 8 of the measuring head is absorbed in bending the legs 7 of the connector 3.

[0143] The mounting ring 16 may be provided with pins (not shown) which are designed to engage the recesses in the end 14 of the measuring adapter 1.

[0144] In order to achieve axial displacement of the actuation rod 8 in relation to the conical opening 8 of the measuring head 2, the measuring unit 12 is provided as a millimetre screw device 17 which by rotation axially displaces the actuation rod 8. Inside the millimetre screw device 17 a releasable ratchet device that ensures tightening of the millimetre screw device 17 may be provided.

[0145] FIG. 7 shows a cross-section of the measuring head 2 by actuation of the actuation rod 8, where the conical main part 8a of the actuation rod 8 is engaging the conical opening 5 (the through-going bore) of the measuring head 2. An upwards directed axial displacement of the actuation rod 8 will result in the sides of the conical main part 8a of the actuation rod 8 forcing the sections 6 of the measuring head from each other, and the slot 13 will be enlarged.

[0146] FIG. 8 shows a metal socket 20 inserted in an acetabulum 21. The metal socket 20 is inserted according to the press-fit technique and is oversize compared with acetabulum 21. Therefore, the outwards directed forces 23 will arise, and the metal socket 20 will be securely anchored in the acetabulum. Behind the metal socket 20 an interspace 24 typically appears which is filled with bone mass so that the metal socket 20 is secured in a natural and solid bed in acetabulum 21. It is the depth of this interspace 24 which is measured with the depth gauge (not shown). It is the outwards directed forces 23 that are very necessary in the long run for measuring in order to optimize hip prosthesis operations.

[0147] The measuring head 2 according to the embodiments described above may also be provided with pressure sensors evenly distributed on the upper surface 4a; the central through-going bore 5, such as the conical through-going bore 5; or in between the upper surface 4a and the central through-going bore 5, such as the conical through-going bore 5. The pressure sensors may be piezoceramic pressure sensors. When providing the measuring head 2 with such sensor arrangements, the pressure in acetabulum or the pressure with which the measuring head is pushed into the acetabulum may be measured. In this way a better fit may be accomplished.

[0148] It will be appreciated that the invention has been illustrated with reference to exemplary embodiments, and that the invention can be varied in many different ways within the scope of the claims.

[0149] It should also be noted that the inclusion in the appended claims of some of the numerals used in the figures is purely for illustrative purposes and not to be considered as limiting the scope of the claims.