TRIAL NECK PIECE FOR A JOINT ENDOPROSTHESIS

Abstract

A trial neck piece for a joint endoprosthesis is designed for temporary arrangement on a separate shaft body (60) that is insertable into a tubular bone (9). It comprises a fastening region (12) which can be plugged temporarily onto a head part (61) of the shaft body (60) by means of a plug connection (l l), and a neck region (IO) for receiving a joint element (19) of the joint endoprosthesis. The trial neck piece (I) is designed as a separate, plug-on attachment piece which, with its fastening region (12), can be plugged with form-fit engagement onto the head part (61) and locked. A latching device (2) is provided which comprises a plurality of latching stages for different height stages of the trial neck piece (I). The invention thus makes available an easily attachable trial neck piece which can be arranged in a defined manner in different height positions in order, on the one hand, to obtain a secure and defined arrangement and, on the other hand, to permit the setting of different heights. The invention further relates to an arrangement with a trial neck piece and with an excavating tool, in particular a reamer, and to an instrument set comprising a trial neck piece and an insertion instrument.

Claims

1. A trial neck piece for a joint endoprosthesis the trial neck piece comprising: a fastening region which has a plug connection, to plug temporarily onto a head part of the shaft body in at least one defined position, a neck region, designed to receive a joint element of a joint endoprosthesis, the trial neck piece having a separate, plug-on attachment piece which, with its fastening region, can be plugged with form-fit engagement onto the head part and locked, wherein a latching device is provided which comprises a plurality of latching stages, for different height stages of the trial neck piece on the head part of the shaft body.

2. The trial neck piece of claim 1, further comprising a securing device for securing the trial neck piece in the respective height stage on the head part of the shaft body, wherein the latching device or securing device is self-locking.

3. The trial neck piece of claim 1, having a guide for coupling to an insertion instrument is provided on the trial neck piece, and the trial neck piece is configured for screwless fastening to the shaft body.

4. The trial neck piece of claim 3, having an angled guide track, with an insertion portion and a locking portion designed as an undercut.

5. The trial neck piece of claim 1, having a fastening region with a turn-around and said fastening region having a lower end, and a shoulder which limits insertion depth.

6. The trial neck piece of claim 1, having a fastening region comprising a sliding sleeve with a through-opening for plugging onto the shaft body, wherein the sliding sleeve is tiltable, and wherein an inner wall of the through-opening comprises a ramp.

7. The trial neck piece of claim 6, comprising a through-opening, having a latching lug wherein when in a locking position, said latching lug engages in a depression of the shaft body and, in a tilting position, is free from the shaft body, wherein the latching lug is arranged on the through-opening.

8. The trial neck piece of claim 7, comprising a latching lug opposite the neck region such that, when force is applied to the neck region, the latching lug is pressed into the depression, and the latching lug is on the same side of the through-opening as the ramp.

9. The trial neck piece of claim 1, comprising a pressure spring, which acts on the inserted shaft body and presses the trial neck piece into a latched position.

10. The trial neck piece of claim 1, comprising a viewing window having an identification field wherein the identification field indicates a size or depth dimension.

11. The trial neck piece of claim 1, comprising a separate shaft body wherein attachment of surgical instruments is provided and the separate shaft body comprises a proximal and a distal part connected in an angularly articulated and rotationally fixed manner.

12. An instrument set comprising the trial neck piece of claim 1 and an insertion instrument comprising a distal end for coupling the trial neck piece at a fixed angle.

13. The instrument set of claim 12, further comprising an insertion instrument having a front end, a gripping module with a rigid receiving fork, and a clamping body arranged in a displaceable manner at the base of the receiving fork.

14. The instrument set of claim 13, further comprising a clamping body which is actuated by a sliding member.

15. The instrument set of claim 14, comprising a beyond-dead-center mechanism.

16. An instrument set for implanting a prosthesis, comprising: a reamer to remove bone substance, having a head part, and a trial neck piece having a fastening region, which can be coupled to the head part of the reamer, and a prosthesis neck region designed to receive a joint ball of the prosthesis, wherein the drive head is a polygon, the trial neck piece has as a plug-on attachment wherein the fastening region, can be plugged with form-fit engagement onto the drive head, and a latching device comprising a plurality of latching stages such that the trial neck piece is attached at different heights on the reamer.

17. The instrument set of claim 16, comprising the trial neck piece of claim 1.

Description

[0032] The invention is explained in more detail below on the basis of advantageous exemplary embodiments and with reference to the drawing, in which:

[0033] FIG. 1 shows an overview of an instrument set for excavating and testing;

[0034] FIGS. 2a, b show detailed view of a reamer according to one embodiment of the invention;

[0035] FIGS. 3a-c show views of a trial neck piece according to one embodiment;

[0036] FIGS. 4a-d show a trial neck piece in different positions, with and without latching or securing;

[0037] FIGS. 5a, b show a plan view of the trial neck piece depicting a transition and a locked position;

[0038] FIGS. 6a-c show several views of an insertion instrument for the trial neck piece;

[0039] FIGS. 7a, b show views of a gripper of the insertion instrument, in the open state and locked state;

[0040] FIGS. 8a-c show views of different phases in the coupling of the trial neck piece to the insertion instrument; and

[0041] FIGS. 9a, b show views of an extraction adapter for the reamer.

[0042] An exemplary embodiment of an instrument set with a trial neck piece according to an exemplary embodiment of the invention is explained below. An overview of such an instrument set is shown in FIG. 1. This is an instrument set for inserting a femoral component of a hip joint endoprosthesis (not shown) into the proximal end of a femur 9. Here, the femoral component has an elongate shaft for anchoring in a cavity of the femur 9. For this purpose, a medullary channel 99 naturally present in the femur is widened by means of the instrument set in order to accommodate the shaft of the femoral component.

[0043] The depicted embodiment of an instrument set according to the invention comprises a trial neck piece 1, a reamer 6, an insertion instrument 7 for the trial neck piece 1, and an extraction adapter 8. Further instruments can be provided, in particular instruments that are usually part of an instrument set for implanting a hip joint endoprosthesis, in particular the femoral component thereof.

[0044] The reamer 6 is designed to widen the medullary canal 99 in the femur 9 at its proximal and adjoining medial diaphyseal region. This is done by excavation, wherein bone substance is removed from the interior of the femur 9 by means of a cutting region 67 of the reamer 6.

[0045] Optionally, other instruments can also be used before the reamer 6, such as a bone saw for removing a defective neck of the femur 9, and drills or other suitable tools for opening an access to the medullary canal 99 of the femur 9.

[0046] The excavation itself can take place in one or more steps, if appropriate also using different reamers (not shown) of progressively increasing size. At the end of the actual excavation, a check has to be made to ascertain whether the medullary canal 99 has been sufficiently widened. This trial is often carried out conventionally using a separate trial implant. According to the invention, this is no longer necessary. Instead, according to the invention, the reamer 1 used for the excavation and present anyway in the medullary canal 99 is used. For this purpose, the reamer 1 can remain in its position; it now functions with its shaft body 60 as the shaft of a trial implant.

[0047] The trial neck piece 1 essentially imitates the neck region of a trial implant. In other words, it corresponds substantially to a trial implant without its shaft. The trial neck piece 1 has a fastening region 12, which is designed for arranging the trial neck piece 1 on the shaft body 60, and a neck region 10, which is designed like a conventional neck region of a trial implant or of an implant. The neck region 10 is designed to carry a joint element (joint ball 19) of the joint endoprosthesis. To carry the joint ball 19, a receiving cone 18 is preferably formed in a manner known per se on the neck region 10, at the outer end thereof. The joint ball 19 can therefore be mounted with the same geometry as in the final joint endoprosthesis, and the joint can thus be moved using the joint endoprosthesis, so as to check the correct fit of the prosthesis and the mobility of the limbs. This procedure is also referred to as testing. If it turns out that the fit is not optimal, for example because the free space in the medullary canal 99 has not yet been made sufficiently deep, this can then be corrected by further excavation of the medullary canal 99 and easily checked, without for this purpose having to remove the reamer 6 or without even having to use the final joint endoprosthesis.

[0048] For testing, the trial neck piece 1 according to the invention is placed onto the shaft body 60 of the reamer 6. For this purpose, the trial neck piece 1 has a main body, designed as a sliding sleeve 13, with a through-opening 14. The trial neck piece 1 is plugged with its through-opening 14 onto a head part 61 of the shaft body 60 of the reamer 6. This head part 61 of the shaft body is formed as a square 64. The square 64 functions as a drive head of the reamer 6. The trial neck piece 1 is thus fastened to the shaft body 60 with form-fit engagement, such that no relative twisting can occur between the trial neck piece 1 and the shaft body 60. How far the trial neck piece 1 can be plugged onto the shaft body 60 of the reamer 6 is variable. A number of height stages are provided for this purpose, such that the plug-on depth of the trial neck piece 1 on the shaft body 60 can be varied. In this way, different lengths of trial implants can be simulated depending on the selected height stage. To limit the insertion depth, a shoulder 17 is provided at the lower end of the fastening region 12 of the trial neck piece 1.

[0049] For the different height stages, a plurality of latching holes 62 are arranged in a row along the axis of the shaft body 60 on top of the head part 61, on at least one side of the square 64. The arrangement of the latching holes 62 is preferably located on several sides of the square 64, in order to allow the trial neck piece 1 to be rearranged (“turned around”) with respect to its angular position (in 90° steps in the case of a square). Moreover, identification fields 65 assigned to the latching holes 62 are provided on one side of the square 64. These preferably carry markers for the various latching steps 20, in the example shown I-VII for the seven height stages defined by the seven latching holes 62. A corresponding viewing window 21 is provided on the trial neck piece 1. It is designed as a cutout and permits, from the outside, a view of the side face of the square 64 that is provided with the identification fields 65. The identification field 65 corresponding to the respective latching hole 62 thus appears with its marking in the viewing window 21, such that in this way the height stage that has been set can be read off easily and cannot be mixed up.

[0050] For interaction with the latching holes 62, a latching lug 22 is provided on an inner side of the through-opening 14. In the exemplary embodiment shown, the latching lug 22 in the through-opening 14 is arranged on the side face opposite the neck region 10. The latching lug 22 is designed like a sawtooth with an inclined upper region and with a steep lower region (see FIG. 3b). The oblique upper region makes it easier for the latching lug 22 to engage in one of the latching holes 62, while the steep lower region acts as an abutment shoulder in the latched state, and therefore a high force can be safely transmitted between the trial neck piece 1 and the shaft body 60 of the reamer 6. This steep design of the abutment shoulder means that there is no risk of the latching lug 22 springing out of the latching hole 62 in an desired manner, even under a high force. Thus, the latching lug 22 and in each case one of the latching holes 62 together form a latching step 20 of a latching device 2. In the exemplary embodiment shown, the number of latching steps 20 corresponds to the number of latching holes 62. Thus, by moving the trial neck piece 1 on the square 64 and engaging it in one of the latching holes 62, a defined height of the trial neck piece 1 relative to the shaft body 60 of the reamer can be adjusted and locked securely. In this way, different sizes of implants can be simulated using one and the same reamer 6 or trial neck piece 1.

[0051] In order to promote a quick and secure engagement of the latching lug 22 in the respective latching hole 62, a pressure spring 30 designed as a leaf spring is also provided in the through-opening 14. It is arranged on the inner face of the through-opening 14, specifically on the inner face lying opposite the latching lug 22. The pressure spring 30 thus acts on the opposite surface of the square 64 and thus presses it overall in the direction of the latching lug 22. A secure engagement between the latching lug 22 and the corresponding latching hole 62 is thereby promoted. In this way, the latching device 2 almost automatically latches into place as soon as the trial neck piece 1 has been pushed along the shaft body 60 into the appropriate position. This latched state is depicted in FIGS. 4a and 4c.

[0052] The shift between different latching holes 62 is visualized in FIG. 4b. It will be seen that the latching lug 22 does not engage in one of the latching holes 62 but instead sits on the outer surface of the square 64 (or slides along it when moving). It will also be seen that the trial neck piece 1 is positioned with a tilt in relation to the latched position (compare FIGS. 4a and 4c). This tilting makes it possible that the latching lug 22 is located outside the latching holes 62, and thus the trial neck piece 1 can be easily displaced along the square 64 of the shaft body 60. In order to facilitate this, a recess designed as an inclined ramp 16 is provided in the through-opening 14, on the same side on which the latching lug 22 is also arranged. As can be seen particularly clearly in FIG. 3b, at this point the wall of the through-opening 14 is not parallel to the opposite side, but rather tilts by a certain angle. This can also be seen from the dashed line, wherein the continuous vertical line represents the central axis 15 of the through-opening 14, and the resulting tilting on account of the ramp 16 is visualized by the line 15′ located to the left of it and tilted by a few degrees. The trial neck piece 1 can be tilted by the resulting angular amount when moving from one latching hole 62 to another of the latching holes 62, as is shown in FIG. 4b. When the desired latching hole 62′ is reached, the trial neck piece 1 is tilted back under the action of the pressure spring 30 to the original position, i.e. parallel to the central axis 15, wherein the latching lug 22 engages in the latching hole 62′. The latching device 2 is thus locked in another latching stage 20′ with respect to an undesired longitudinal movement of the trial neck piece 1 along the shaft body 60.

[0053] To provide additional protection of the latching device 2 against undesired movement or actuation, a securing device 3 is additionally provided. In the exemplary embodiment shown, it is designed as a locking screw 32 in a secondary bore 33. The locking screw 32 is arranged in the transition between the neck region 10 and the fastening region 12 of the trial neck piece 1, and the secondary bore 33 is preferably adjacent to the through-opening 14 and is arranged approximately parallel, wherein the secondary bore 33 ends in the region of the pressure spring 30. By screwing in the locking screw 32, the shank of the latter is moved down so far that at least the tip of the shank of the locking screw 32 pushes the pressure spring 30 against the side faces of the square 64 of the shaft body 60 and thus jams the shaft body 60 in its untilted position in the through-opening 14 of the trial neck piece 1. Tilting is therefore no longer possible, such that the latching lug 22 is caught in the corresponding latching hole 62 and a longitudinal movement of the latching device 2 is reliably blocked. By unscrewing the locking screw 32, this locking can be released again if desired.

[0054] In order to allow the surgeon to easily check from the outside whether the latching device 2 is securely engaged, a test window 21 is provided. The latter is formed at the upper end of the trial neck piece 1 (see FIG. 5a), specifically between the upper end 61 of the shaft body 60 and that side of the trial neck piece 1 facing away from the neck region 10. The test window 21 is visible when the trial neck piece 1 is in the tilted state, as is also depicted in FIG. 4b. When this test window 21 is visible, the latching device 2 is not engaged and there is therefore an unsecure state. It is only when the trial neck piece 1 has once again adopted its untilted state (see FIG. 5b) that the test window 21 disappears. This is the sign that the latching device 2 is now engaged again. Now, if so desired, the locking screw 32 can be screwed in for further securing, so as to achieve the secured state according to FIG. 4d.

[0055] For inserting the trial neck piece 1 and, if necessary, extracting the trial neck piece 1 together with the reamer 6, an insertion instrument 7 is provided. The latter is designed with a long shaft 70, at one end of which a handle 71 is arranged. At the opposite end of the shaft 70, a quick-release coupling 4 is provided which includes a gripping module 44. The gripping module 44 comprises a receiving fork 45, on each of whose mutually facing inner surfaces a retaining pin 46 is arranged. In the exemplary embodiment shown, the retaining pins 46 are formed as cylinder-like projections. The gripping module further comprises a clamping slide 47 which is arranged between the inner surfaces of the receiving fork 45 in such a way as to be displaceable in the longitudinal direction of the shaft. The clamping slide 47 is shaped like a fork at its end remote from the shaft, with pressure lugs 48 provided at the tip. On the shaft side, the clamping slide 47 is arranged on a sliding member 74 which is designed as a sliding pin and which is guided longitudinally displaceably along a central axis 72 of the shaft 70 of the insertion instrument 7. The sliding member 74 is preferably designed as a spring rod.

[0056] The gripping module 44 is designed to interact with a guide track 40 on the trial neck piece 1. The guide track is angled, with an elongate insertion portion extending from the upper edge obliquely in the direction of the central axis 15, and with a locking portion 42 which adjoins the far end of the insertion portion and extends like an undercut in the direction of the upper edge of the trial neck piece 1. The guide track 40 is dimensioned to accommodate the retaining pins 46. These can be pushed along the insertion portion 41 onto the main body of the trial neck piece 1 (see FIG. 8a) in order finally to adopt a holding position in the undercut locking portion 42 (see FIG. 8b). The pressure lugs 48 can then be brought to bear on the upper side of the trial neck piece 1. For this purpose, a pressure saddle 35 is preferably provided, having a concavity adapted to the outer contour of the pressure lugs 48. Thus, by bracing the clamping slide 47 with its pressure lugs 48 against the retaining pins 46, the trial neck piece 1 can be securely held on the insertion instrument 7, namely in a secure manner with respect to firm locking both in the longitudinal direction and against tilting (see FIG. 8c).

[0057] The sliding member 74, designed as a spring rod, forms, together with a pivot element 73, a beyond-dead-center mechanism (see FIG. 6). This represents a bi-stable fixing device for the gripping module 44. The front of the pivot element 73 acts on the sliding member 74 and moves the latter forward depending on a pivoting position. The clamping slide 47 arranged at the front end of the sliding member 74 is thus advanced accordingly (see also the arrow in FIG. 7a). The pivot element 73 has two stops, which each define an end position. In one end position, the sliding member 74 is drawn back with the clamping slide 47, and in the other end position the sliding member 74 is located with the clamping slide 47 in the advanced position. The pivot element 73 thus forms with the sliding member 74 a beyond-dead-center mechanism, with which the clamping slide 47 can be fixed in the advanced position and, by virtue of the sliding member 74 being made of spring steel, can be tensioned.

[0058] The actuation of the pivot element 73 and tensioning of the sliding member 74 occur when the gripping module 44 with its retaining pins 46 has been inserted into the guide track 40 on the trial neck piece 1 and the retaining pins 46 have adopted their position in the locking portion 42. By means of tensioning, the clamping slide 47 is then moved forward, such that it acts with its pressure lugs 48 on the pressure saddle 35, and the trial neck piece 1 is firmly gripped and held. It can thus be safely moved and positioned by means of the insertion instrument 7. This fastening is secure and capable of such high force transmission that, if appropriate, the reamer 6 coupled to the trial neck piece 1 via the locking device 2 can also be reliably extracted from the medullary canal 99 of the bone 9 by means of the insertion instrument 7.

[0059] The instrument set can furthermore comprise an extraction adapter 8. The latter is designed to be plugged onto the upper end 61 of the shaft body 60 of the reamer 6. The extraction adapter 8 has a shaft 80, at the front end of which a coupling piece is arranged. The coupling piece comprises a conical widening 88. At the front, free end of the extraction adapter 8, a square receiving opening 81 is provided. The latter is designed to receive the free end 61 of the shaft body 60. A locking device 83 is provided on one side of the receiving opening 81. The locking device 83 is designed as a lever which is pivotable via a bearing pin 84. At its far end, the lever of the locking device 83 has a retaining lug 82, which protrudes into the receiving opening 81. The retaining lug 82 is designed to interact with one of the latching holes 62 on the square 64 of the shaft body 60 of the reamer 6 in order to fix the reamer 6 with tension resistance on the extraction adapter 8. A pressure spring 86, which acts on an actuating lever 85 of the locking device 83, is arranged in the region of the thickening 88. It is pretensioned in such a way that it presses the actuating lever 85 into such a position that the retaining lug 82 is moved in the direction of the latching hole 62 and thus locked. The reamer 6 is thus retained on the extraction adapter 8 in a tension-resistant manner and can be pulled out of the bone 9 in a manner known per se. To release the extraction adapter 8, it is necessary only to exert pressure on the actuating lever 85 in order to pivot the retaining lug 82 out of the region of the receiving opening 81 and thereby release the reamer 6. For simple actuation, a recess 87 in the conical widening 88 is provided as a finger rest around the actuating lever 85.

[0060] At the opposite end of the shaft 80, the extraction adapter 8 preferably has an adapter for connection to conventional instruments, for example what is called a Hudson adapter (not shown). Thus, conventional tools can also be used to safely extract the reamer 6. Alternatively and/or in addition, provision can also be made for such a Hudson adapter to be arranged at the upper end of the head part 61 of the reamer, as long as the cross section thereof is small enough for passage through the through-opening 14 of the trial neck piece 1.