Instrument For Transmitting Torque

Abstract

An instrument for transmitting torque is described. The instrument comprises a torque receiving portion at a proximal end of the instrument, a torque delivering portion at a distal end of the instrument, and a flexible shaft extending between the torque receiving portion and the torque delivering portion. The flexible shaft comprises torque transmitting elements coupled in series along a longitudinal direction of the shaft. A female coupling feature of a torque transmitting element comprises a notch and a male coupling of an adjacent torque transmitting element comprises a protrusion sized to fit into the notch. The notch has a constant width or a narrowing width starting from an outer surface of the torque transmitting element comprising the notch.

Claims

1. An instrument for transmitting torque, the instrument comprising: a torque receiving portion at a proximal end of the instrument; a torque delivering portion at a distal end of the instrument; a flexible shaft extending between the torque receiving portion and the torque delivering portion, the flexible shaft comprising torque transmitting elements coupled in series along a longitudinal direction of the shaft such that one of the torque transmitting elements is rotationally fixed and tiltable relative to an adjacent one of the torque transmitting elements, wherein one of the torque transmitting elements comprises a female coupling feature and an adjacent one of the torque transmitting elements comprises a male coupling feature matching the female coupling feature, wherein the one of the torque transmitting elements is coupled to the adjacent one of the torque transmitting elements via the female coupling feature and the male coupling feature, wherein the female coupling feature comprises a notch and the male coupling feature comprises a protrusion sized to fit into the notch.

2. The instrument of claim 1, wherein the notch has only flat or concave side walls.

3. The instrument of claim 1, wherein at least one of the following conditions holds: the notch has a constant width or a narrowing width starting from an outer surface of the torque transmitting element comprising the notch; and the protrusion has a constant width or a width narrowing towards a distal end thereof.

4. The instrument of claim 1, wherein the protrusion has only flat or convex side walls.

5. The instrument of claim 1, wherein the notch extends longitudinally along a notch axis, wherein the notch and the protrusion are configured such that the adjacent one of the torque transmitting elements, having the protrusion coupled to the notch, can be tilted relative to the notch around an axis non-parallel, in particular orthogonal, to the notch axis.

6. The instrument of claim 5, wherein the notch axis is non-parallel to the longitudinal direction of the shaft.

7. The instrument of claim 6, wherein the notch axis is perpendicular to the longitudinal direction of the shaft.

8. The instrument of claim 5, wherein the protrusion extends longitudinally along a protrusion axis and wherein at least one axis chosen from the notch axis and the protrusion axis extends across a radial center of at least element chosen from the one of the torque transmitting elements and the adjacent one of the torque transmitting elements.

9. The instrument of claim 1, wherein the notch of a torque transmitting element extends non-parallel to the protrusion of the same torque transmitting element.

10. The instrument of claim 1, wherein each of the torque transmitting elements comprises a through-hole, and wherein the instrument further comprises an elongate alignment member extending through the through-holes of the torque transmitting elements, wherein the alignment member is made from a spring-elastic material.

11. The instrument of claim 10, wherein the alignment member comprises or consists of a spring wire.

12. The instrument of claim 11, wherein the spring wire is a non-braided wire.

13. The instrument of claim 10, wherein the spring-elastic material is a superelastic or pseudoelastic material.

14. The instrument of claim 10, wherein the alignment member is configured to align the torque transmitting elements in a predefined orientation relative to one another.

15. The instrument of claim 10, wherein the alignment member is configured to, when the torque transmitting elements are in the predefined orientation relative to one another, fulfil at least one of the following criteria: a) the alignment member is in a state of a lowest elastic potential energy; b) the alignment member is free from a shear force; c) the alignment member is free from a bending moment; and d) the alignment member is free from a tensile force.

16. The instrument of claim 10, wherein the alignment member is translationally fixed along at least one direction chosen from the longitudinal direction of the shaft, a first longitudinal axis of the torque delivering portion and a second longitudinal axis of the torque receiving portion.

17. The instrument of claim 16, wherein the alignment member is attached to one or more components of the instrument chosen from the torque receiving portion, the torque delivering portion and the shaft.

18. The instrument of claim 10, wherein the alignment member extends throughout a through-hole provided in each of the torque receiving portion and the torque delivering portion.

19. The instrument of claim 1, comprising at least one recess facing the shaft, the at least one recess being formed in at least one component of the instrument chosen from the torque receiving portion and the torque delivering portion.

20. The instrument of claim 19, wherein the at least one recess fulfils at least one of the following conditions: (i) it is configured as a blind hole; (ii) it is arranged in a radial center of the at least one component; (iii) it has an essentially cylindrical shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

[0046] FIG. 1 shows an embodiment of an instrument in accordance with the present disclosure;

[0047] FIG. 2 shows a longitudinal cross-section of the instrument of FIG. 1;

[0048] FIGS. 3a-3b show different views of a torque transmitting element of the instrument of FIG. 1;

[0049] FIGS. 4a-4b show different views of a torque delivering portion of the instrument of FIG. 1; and

[0050] FIG. 5 shows a torque receiving portion of the instrument of FIG. 1

DETAILED DESCRIPTION

[0051] In the following description, exemplary embodiments of an instrument will be explained with reference to the drawings. The same reference numerals will be used to denote the same or similar structural features.

[0052] FIG. 1 shows an embodiment of an instrument 2000 in accordance with the present disclosure. The instrument 2000 is adapted for transmitting torque. The instrument 2000 comprises a torque receiving portion 46 at a proximal end of the instrument 2000 and a torque delivering portion 54 at a distal end of the instrument 2000. The instrument 2000 further comprises a flexible shaft 48 extending between the torque receiving portion 46 and the torque delivering portion 54. The flexible shaft 48 comprises a plurality of torque transmitting elements 52. The plurality of torque transmitting elements 52 are coupled in series along a longitudinal direction 50 of the shaft 48 such that each of the torque transmitting elements 52 is rotationally fixed and tiltable relative to an adjacent one of the plurality of torque transmitting elements 52. In some variants, the shaft 48 may comprise between 4 and 40 (e.g., between 10 and 25) torque transmitting elements 52.

[0053] One may say that the plurality of torque transmitting elements 52 form a chain along the longitudinal direction 50 of the shaft 48. In other words, the shaft 48 may be formed by the plurality of mutually coupled, or interlinked, torque transmitting elements 52.

[0054] The shaft 48 may be flexible in that it is (e.g., reversibly) bendable. That is, an extension of the shaft may be changed from a linear extension to a curved extension and vice versa. Put differently, the shaft 48 may be reversibly bent from a first shape into a second shape from the first shape. The shaft 48 may be bendable by changing a relative orientation between the torque receiving portion 46 and the torque delivering portion 54.

[0055] Each of the plurality of torque transmitting elements 52 may be tiltable relative to an adjacent one of the plurality of torque transmitting elements 52 by changing an angle between an axis (e.g., central, longitudinal or rotational axis) of the torque transmitting element 52 relative to an axis (e.g., central, longitudinal or rotational axis) of the adjacent one of the plurality of torque transmitting elements 52. The two axes may be part of or define at least a part of the longitudinal direction 50. By tilting the torque transmitting elements 52 relative to one another, the shape of the shaft 48 may be changed in regard to its extension between the torque receiving portion 46 and the torque delivering portion 54. One may say that by bending the shaft 48, at least some of the plurality of torque transmitting elements 52 are tilted relative to one another.

[0056] The plurality of torque transmitting elements 52 may be rotationally fixed relative to one another such that a torque applied around the longitudinal direction 50 of the shaft 48 at one of the plurality of torque transmitting elements 52 is transmitted to all others of the plurality of torque transmitting elements 52. The flexible shaft 48 may be configured such that the shaft can be bent whilst permitting a transmission of torque between the plurality of torque transmitting elements 52 around the longitudinal direction 50 of the shaft 48. The shaft 48 may have an overall cylindrical shape. Each of the plurality of torque transmitting elements 52 may have an essentially cylindrical outer surface forming part of an overall cylindrical outer surface of the shaft 48. Each of the plurality of torque transmitting elements 52 may have the same geometry. Each of the plurality of torque transmitting elements 52 may be rotationally offset from a respective adjacent one of the plurality of torque transmitting elements 52 of the shaft 48.

[0057] A first one of the plurality of torque transmitting elements 52 may be coupled to the torque receiving portion 46 such that the first of the plurality of torque transmitting elements 52 is rotationally fixed and tiltable relative to the torque receiving portion 46. A second one of the plurality of torque transmitting elements 52 may be coupled to the torque delivering portion 54 such that the second of the plurality of torque transmitting elements 52 is rotationally fixed and tiltable relative to the torque delivering portion 54.

[0058] The flexible shaft 48 may be coupled or rigidly attached to both the torque receiving portion 46 and the torque delivering portion 54. This may ensure that a torque applied at the torque receiving portion 46 around the longitudinal direction 50 is transmitted via the plurality of torque transmitting elements 52 to rotate the torque delivering portion 54 around the longitudinal direction 50. An input torque applied at the torque receiving portion 46 around a longitudinal axis of the torque receiving portion 46 may result in an output torque at the torque delivering portion 54 around the longitudinal axis of the torque delivering portion 54, even if the longitudinal axis of the torque receiving portion 46 is angled or skew relative to the longitudinal axis of the torque delivering portion 54.

[0059] The torque delivering portion 54 may comprise a screw-driving tool portion 78 adapted for fastening a screw. In this case, the instrument 2000 may be configured as a screwdriver. The screw driving tool portion 78 may be configured as a hexagonal screw-driving portion. Other forms of the screw-driving portion are also possible (e.g., slot-type blades, cross-type blades, square or star). Alternatively, the torque delivering portion may comprise a drill head (not shown) adapted for drilling holes (i.e., the instrument 2000 may be configured as a drill).

[0060] The torque receiving portion 46 may be configured to be coupled to a handle or an electrical actuator such as a motor. As illustrated in the example shown in FIG. 1, the instrument 2000 may further comprise a handle 11 attached or coupled to the torque receiving portion 46. The handle 11 may be configured to transmit a torque applied around a longitudinal axis of the handle 11 to the torque receiving portion 46. The handle 11 may thus be rotationally fixed to the torque receiving portion 46. The longitudinal axis of the handle 11 may coincide with a longitudinal axis of the torque receiving portion 46.

[0061] FIG. 2 shows a cross-section of the instrument of FIG. 1 along the longitudinal axis 10. The handle 11 is not illustrated in this figure. As can be seen, each of the torque transmitting elements 52 comprises a through-hole 59. This through-hole 59 may extend along the longitudinal direction 50, for example in a center of the shaft 48. The through-hole 59 may extend in a radial center and along an axial direction of the respective torque transmitting element 52. The through-hole 59 may have a substantially constant diameter (e.g., may be cylindrical).

[0062] As illustrated in FIG. 2, the instrument 2000 may comprise an elongate alignment member 14 extending through the through-holes 59 of the plurality of torque transmitting elements 52. The alignment member 14 may be made from a spring-elastic material. The alignment member 14 may be the only component extending through the through-holes 59.

[0063] The spring-elastic material may be a superelastic or pseudoelastic material. Pseudo- or superelasticity may designate an elastic, reversible response to an applied stress, caused by a phase transformation between an austenitic and martensitic phase of the material. The spring-elastic material may be a shape memory alloy, for example a nickel titanium alloy such as Nitinol.

[0064] In the illustrated example, the alignment member 14 consists of a spring wire 16. The spring wire 16 in this example does not form a coil, and is not rolled, wrapped or wound. The spring wire 16 may be a non-braided wire. The spring wire 16 may have a substantially circular or polygonal cross-section. The alignment member 14, in particular the spring wire 16, may have a diameter between 0.8 mm and 3 mm (e.g., ca 1.5 mm to 2 mm). The alignment member 14, in particular the spring wire 16, may have a length between 30 mm and 400 mm (e.g., 70 mm to 200 mm). The spring wire 16 may extend in a linear direction, for example at least within each of the through-holes 59. The spring wire may extend along the longitudinal direction 50 of the shaft 48. It is noted that other variants of the alignment member 14 are also be possible. For instance, the alignment member 14 may form a coil or be a braided wire. The type and configuration of the alignment member 14 may be selected so as to provide the functionality described in the following.

[0065] The alignment member 14 may be configured to be elastically deformed when the shaft 48 is bent, and provide a spring force counteracting the bending of the shaft 48. To this end, the alignment member 14 may be configured to align the torque transmitting elements 52 in a predefined orientation relative to one another (e.g., along the longitudinal direction 50 of the shaft 48). This configuration may enable the shaft 48 to take a predefined shape when no bending torque is applied thereto. For example, the alignment member 14 may provide a spring force aligning the plurality of torque transmitting elements 52 so that the shaft 48 extends in a linear direction (i.e., has a straight extension).

[0066] The alignment member 14 may be configured to, when the torque transmitting elements 52 are in the predefined orientation relative to one another, fulfil at least one of the following criteria: a) the alignment member is in a state of a lowest elastic potential energy; b) the alignment member is free from a shear force; c) the alignment member is free from a bending moment; the alignment member is free from a tensile force.

[0067] The instrument 2000 may comprise a recess 64 facing the shaft 48. The recess 64 may have an essentially cylindrical shape. The recess 64 may be configured as a blind hole. In the example shown in FIG. 2, the recess 64 is formed in the torque delivering portion 54 and extends along a longitudinal direction of the torque delivering portion 54. The recess 64 may be arranged in a radial center of the torque delivering portion 54.

[0068] As can be seen in FIG. 2, the torque receiving portion 46 may comprise a further recess 62 configured, in the present variant, as a blind hole. The recess 62 may be directed towards the shaft 48 and may extend along the longitudinal direction 50 of the shaft 48. The recess 62 may be arranged in a radial center of the torque receiving portion 46 and may have an essentially cylindrical shape.

[0069] The alignment member 14 may be configured to align the shaft 48 in a predefined orientation relative to at least one component chosen from the torque delivering portion 54 and the torque receiving portion 46. The alignment member 14 in this case may extend at least partially into a through-hole or recess facing the shaft 48 and provided in the respective at least one component. As described above for the plurality of torque transmitting elements 52, this configuration may enable the shaft 48 and the respective at least one component to take a predefined shape when no external bending moment is applied thereon. For example, the alignment member 14 may provide a spring force aligning the plurality of torque transmitting elements 52 and the respective at least one component such that both the shaft 48 and the respective at least one component extend in a linear direction.

[0070] The alignment member 14 may be configured to, when the shaft 48 is in the predefined orientation relative to the at least one component, fulfil at least one of the following criteria: a) the alignment member is in a state of a lowest elastic potential energy; b) the alignment member is free from a shear force; c) the alignment member is free from a bending moment; the alignment member is free from a tensile force. The alignment member 14 may be configured to extend linearly (e.g., in a linear direction) when being in the state of a lowest elastic potential energy.

[0071] The alignment member 14 may “stiffen” the instrument 2000 such that it extends in an essentially linear direction, while providing for a selected degree of flexibility of the shaft 48. Thus, the instrument 2000 may be more easily handled by a user. For instance, aligning the instrument 2000 using the handle 11 such that the torque delivering portion 54 is at in predefined position may be facilitated.

[0072] The instrument 2000 may be configured such that the alignment member 14 is translationally fixed along at least one direction chosen from the longitudinal direction 50 of the shaft 48, the first longitudinal axis and the second longitudinal axis. Optionally, the alignment member 14 may be attached to one or more components of the instrument 2000 chosen from the torque receiving portion 46, the torque delivering portion 54 and the shaft 48. For example, the alignment member 14 (e.g., longitudinal ends thereof) may be attached (e.g., forged, soldered, clamped or welded) to the torque receiving portion 46 and the torque delivering portion 54. In this case, it may be advantageous if the alignment member 14 extends throughout a through-hole provided in each of the torque receiving portion 46 and the torque delivering portion 54.

[0073] Accordingly, the alignment member 14 may not only serve the alignment of the shaft 48, but also ensure that the plurality of torque transmitting elements 52 are restricted in transversal movements along the longitudinal axis of the shaft 48. Also, a loss or decoupling of one component of the instrument 2000 (e.g., the torque delivering portion 54 or one of the plurality of torque transmitting elements 52) may be prevented by the alignment member 14 being attached to the torque receiving portion 46 and the torque delivering portion 54 (e.g., at its longitudinal ends).

[0074] In one variant, the alignment member 14 may be arranged such that tensile forces are applied thereon when bending the shaft 48. The alignment member 14 may be configured to be stretched along a longitudinal axis thereof when bending the shaft 48 such that the plurality of torque transmitting elements 52 are misaligned from the predefined relative orientation. This may increase a restoring force provided by the alignment member 14 upon bending of the shaft 48.

[0075] In another variant, the alignment member 14 may be arranged such that no tensile forces are applied thereon when bending the shaft 48. This effect may be obtained by appropriately designing the torque transmitting elements such that the shaft can be bent whilst maintaining its length. This may be enabled by the protrusion(s) having a convexly curved end face. The alignment member 14 may thus be configured to not be stretched along a longitudinal axis thereof when bending the shaft 48 such that the plurality of torque transmitting elements 52 are misaligned from the predefined relative orientation. This may improve the lifetime of the alignment member 14.

[0076] Referring again to FIG. 1, the torque receiving portion 46 is formed as an (e.g., essentially cylindrical) elongate linear member. An axial length of the torque receiving portion may be longer than an axial length of the shaft 48. Visual indications 56 such as one or more of a manufacturer name, an instrument name or number, certification or warning may be provided on a side or outer surface of the torque receiving portion 46. The torque receiving portion 46 in the illustration of FIG. 1 comprises a coupling portion 57 configured to couple to the handle 11 or an electric actuator (e.g., motor).

[0077] With reference to FIG. 2, which shows a longitudinal cross-section of the instrument 2000 of FIG. 1, the torque receiving portion 46 may comprise a first crimp segment 58 fixing (e.g., attaching) the alignment member 14, extending through through-holes 59 of the torque transmitting elements 52, to the torque receiving portion 46.

[0078] The torque delivering portion 54 may comprise a second crimp segment 60 fixing (e.g., attaching) the alignment member 14 to the torque delivering portion 54. In this case, the alignment member 14 may not need to extend throughout through-holes in each of the torque receiving portion 46 and the torque delivering portion 54, but may extend into recesses 62, 64 provided in the torque receiving portion 46 and the torque delivering portion 54 and facing the shaft 6, the recesses being optionally formed as blind holes.

[0079] The crimp segments 58, 60 may be provided at a longitudinal position of the instrument 2000 corresponding to a longitudinal position of the respective recess 62, 64. Alternative attachment means may be provided instead of the crimp segments 58, 60. For example, the alignment member 14 may be soldered or welded to the torque receiving portion 46 and/or the torque delivering portion 54. The soldering or welding may be applied through a through-hole extending from an exterior of the instrument 2000 to the respective recess 62, 64. In an alternative variant, the alignment member 14 may extend through a through-hole in the torque receiving portion 46 and/or through a through-hole in the torque delivering portion 64 and may be soldered or welded to the respective one of the torque receiving portion 46 and the torque delivering portion 64 at an end of the through-hole facing away from the shaft 48.

[0080] Each of the plurality of torque transmitting elements 52 may have the same geometry and may be rotationally offset from a respective adjacent torque transmitting element 52 of the shaft 48. The torque transmitting elements 52 may have the geometry illustrated in FIGS. 3a and 3b.

[0081] As can be seen in FIGS. 3a and 3b, the torque transmitting element 52 may comprise a female coupling feature 66 and a male coupling feature 68 matching the female coupling feature 66. The plurality of torque transmitting elements 52 may be coupled in series by the female coupling features 66 and the male coupling features 68 of the plurality of torque transmitting elements 52 of the shaft 48.

[0082] The female coupling feature 66 comprises or consists of a notch 70. The male coupling feature 68 comprises or consists of a protrusion 72 sized to fit into the notch 70. As illustrated in FIGS. 3a and 3b, the notch 70 has a constant width. The notch 70 alternatively tapers from an outer surface of the torque transmitting element 52 toward a bottom surface of the notch 70. The bottom surface of the notch 70 may be flat or concavely curved. In a cross-section across a width of the notch 70, the notch 70 may only have flat or concave walls, and for example have an overall rectangular shape.

[0083] The notch 70 may extend non-parallel to the protrusion 72 of the same torque transmitting element 52. The notch 70 may extend orthogonal relative to the protrusion 72 of the same torque transmitting element 52. The notch 70 may extend across a radial center of the torque transmitting element 52. The protrusion 72 may extend longitudinally along a protrusion axis 76. At least one of the notch axis 74 and the protrusion axis 76 may extend across a radial center of the torque transmitting element 52. At least one of the notch axis 74 and the protrusion axis 76 may cut and/or extend essentially perpendicular to the longitudinal axis 50 of the shaft 48. The notch axis 58 may be non-parallel, for example orthogonal, to the protrusion axis 60. The notch 70 may be rotationally offset relative to the protrusion 72 (e.g., around the longitudinal direction 50 of the shaft 52).

[0084] In a cross-section across a width of the protrusion 72, the protrusion 72 may only have flat or convex walls and for example have an overall rectangular shape. The protrusion 72 may widen from a longitudinal end of the protrusion (e.g., forming an end of the torque transmitting element 52) towards a base of the protrusion.

[0085] As shown in FIGS. 3a and 3b, the free end of the protrusion 72 may have a convexly curved end face. The protrusion 72 may thus has a convex height profile, with the maximum height being defined in a center portion of the protrusion 72 and minimum heights being defined at opposite lateral portions of the protrusion 72. The lateral portions of the convexly curved end face may define a maximum tilting angle between two adjacent torque transmitting elements 52 (by coming into abutment against the bottom surface of the adjacent notch 70).

[0086] In some variants, the notch 70 may have a concavely formed bottom surface and the protrusion 72 may have a correspondingly formed convex top surface so as to guide a tilting movement of the protrusion 72 of one torque transmitting element 52 in the notch 70 of the adjacent torque transmitting element 52. The notch 70 and the protrusion 72 may be configured such that an adjacent one of the plurality of torque transmitting elements 52, having its protrusion 72 coupled to the notch 70 (e.g., of a certain torque transmitting element 52), can be tilted relative to the notch 70 (e.g., of the certain torque transmitting element 52) around an axis orthogonal to the notch axis 74 of the notch 70 (e.g., of the certain torque transmitting element 52). The adjacent one of the plurality of torque transmitting elements 52 may be tiltable in a plane comprising the notch axis 74 of the notch 70 (e.g., of the certain torque transmitting element 52) and, optionally, the longitudinal direction 50 of the shaft 48). Put differently, the notch 70 and the protrusion 72 may be configured such that an adjacent one of the plurality of torque transmitting elements 52, having its notch 70 coupled to the protrusion 72 (e.g., of a certain torque transmitting element 52), can be tilted relative to the protrusion 72 (e.g., of the certain torque transmitting element 52) around an axis orthogonal to the protrusion axis 76 of the protrusion 72 (e.g., of the certain torque transmitting element 52). The adjacent one of the plurality of torque transmitting elements 52 may be tiltable in a plane comprising the protrusion axis 76 of the protrusion 72 (e.g., of the certain torque transmitting element 52) and, optionally, the longitudinal direction 50 of the shaft 48.

[0087] FIGS. 4a and 4b show different views of a torque delivering portion 54 of the instrument 2000 of FIG. 1. The torque delivering portion 54 may comprise a coupling feature 80 configured to couple to an adjacent one (e.g., the second) of the plurality of torque transmitting elements 52 of the shaft 48. In this example, the torque delivering portion 54 comprises a notch 82 acting as a female coupling feature for the protrusion 72 of the adjacent one (e.g., the second) of the plurality of torque transmitting elements 52. The notch 82 may be configured similar to the notch 70 described above. It is noted that in an alternative implementation, the coupling feature 80 may be a male coupling feature such as the protrusion 72 described above.

[0088] FIG. 5 schematically illustrates a torque receiving portion 46 of the instrument 2000 of FIG. 1. The torque receiving portion 46 may comprise a handle or actuator coupling portion 57 at a longitudinal end thereof (not shown in FIG. 5). The coupling portion 57 may be essentially cylindrical, or prismatic (e.g., hexagonal). At an opposite longitudinal end, the torque receiving portion 46 may comprise a coupling feature 84 configured to couple to an adjacent one (e.g., the first) of the plurality of torque transmitting elements 52 of the shaft 48. In the illustrated example, the torque receiving portion 46 comprises a protrusion 86 configured to couple to the notch 70 of the adjacent one (e.g., the first) of the plurality of torque transmitting elements 52. The protrusion 86 may be configured similar to the protrusion 72 described above and may have a substantially rectangular cross-section. It is noted that in an alternative implementation, the coupling feature 84 may be a female coupling feature such as the notch 70 described above.

[0089] Numerous modifications of the instrument 2000 may be possible. In one particular example, the instrument 2000 does not necessarily comprise the alignment member 14. Other variations will be apparent to those skilled in the art. Although numerous advantages have been described herein, the claimed subject matter is not limited thereto. Those skilled in the art will be aware of additional or alternative advantages and technical effects that may be obtained with the subject matter disclosed herein.