DE29922792U1 - Instrument for handling and inserting a prosthetic component - Google Patents

Description

CeramTecAG ·":: . ·: ·*: :":?5't2.i999 Dr. sat/we

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Instrument for handling and inserting a prosthetic component

The invention relates to an instrument for handling and inserting an insert shell into an outer shell of a two-part acetabular prosthesis according to the preamble of the first claim.

Joint prostheses in which one joint partner is designed as a socket and the other joint partner as a ball head that is rotatably mounted in the socket are particularly known as shoulder and hip joint prostheses. These prostheses are usually modular in design. This means that, for example, the joint socket is in two parts and consists of an outer shell that is inserted into the bone.

&iacgr;&ogr; and an insert shell that is inserted into the outer shell and which has the joint surface, the sliding surface for the other joint partner. The insert shell is usually inserted into the outer shell using a press fit. To do this, the insert shell must be aligned very precisely with the outer shell to avoid jamming when inserting. If the insert shell is jammed, damage to the insert shell can occur, in addition to an inaccurate alignment of the joint surface with the ball head. Insert shells made of ceramic in particular can break or even break.

If the insert shells are inserted by hand by the surgeon, handling in the area around the surgical wound is difficult due to the surgeon's gloves being wetted with body fluids and the poor visibility. For this reason, it is known to provide instruments with which the insert shells to be inserted can be handled better. European patent application EP 0 888 759 A1 discloses a handling instrument for inserting an insert of an implant, in particular an artificial hip joint socket, into the associated shell. The instrument comprises a tubular rod which has a holding device at one end for holding the insert. It also has a

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Actuating element for releasing the insert. It is a rod which can be moved in the tube of the holding device and with which the insert can be pressed out of the holding device. The holding device comprises at least three springy lamellae pointing in the axial direction, which are arranged in such a way that their free ends point away from the rod and which are designed in such a way that when the insert is held they form a snap connection with the insert.

The disadvantage is that the implant must first be inserted into the snap-on device, which is difficult when a surgeon is wearing gloves that are wet with body fluids. Furthermore, the instrument must be disinfected after each use. In addition, the instrument is long, which is unwieldy in a confined operating area.

The present innovation is based on the task of presenting an instrument for handling and inserting an insert shell into an outer shell of a two-part acetabular cup prosthesis, which allows easy positioning and tilt-free insertion with a low overall height.

The problem is solved with the help of the characterizing features of the first claim. Advantageous embodiments of the innovation are claimed in the subclaims.

The instrument according to the invention differs from the known instruments in that the lamellae of the holding tool extend outwards in a spiral shape, similar to a paddle wheel, from a hub through the centre of which the shaft of the tappet runs. The profile of the lamellae tapers outwards from the hub. This makes the lamellae more elastic towards the outside. Due to their shape, the spiral lamellae exert a significantly higher clamping force on the insert shell to be held than holding tools with shorter, radially extending lamellae. The higher clamping force enables significantly safer handling. In addition, the spiral

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Lamellas allow for radial expansion and thus compensate for differences in the diameter of the insert shells. This means that insert shells with different external diameters can be held securely with one instrument. For example, insert shells with external diameters of 30 mm to 34 mm can be held easily and securely in the same holding tool.

The insert shells are held in a clamp fit, formed by a stop surface extending radially inwards from the slats and a claw perpendicular to this, extending in the direction of the plunger, which rests against the insert shell in the radial direction and can be placed in the axial direction with its front surface as a contact surface on the edge of the outer shell. Since the claws on the slats are all the same length, when all the claws are placed on the front surface of the outer shell, the insert shell is precisely positioned for use. In the difficult environment of the surgical wound, the surgeon can thus position the insert shell safely and precisely for pressing into the outer shell.

The displacement path of the plunger when inserting an insert shell is made up of parts. The first part is the displacement path from its starting position to a position in which the plunger disk used to press the insert shell into place rests against the insert shell. The further displacement path is the path that is covered from the release of the insert shell from the holding tool to its contact with the outer shell and a small path to create the clamping fit in the outer shell. It is advantageous that when an insert shell is held by a holding tool, the plunger disk does not rest directly against the insert shell. On the one hand, insert shells with the same outer diameter can have different inner diameters, so that the plunger would have to be fixed in different positions. On the other hand, the position of the plunger gives the surgeon an indication of the position of the insert shell when inserting an insert shell. If the insert shell is positioned on the outer shell with the instrument, the plunger disk in the insert shell is first pushed in when the plunger is pressed in.

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brought into contact. To do this, the resistance of the force with which the plunger is held in its initial position is overcome. After overcoming this resistance, a second resistance is felt, which indicates that the plunger disk is in contact with the insert shell. From then on, the surgeon must apply the force that releases the insert shell from the holding tool and then clamps it into the outer shell.

The overall height of the instrument is made up of the dimensions of the holding tool and the respective sections of the displacement path of the plunger. The displacement path of the plunger includes, where applicable, the displacement path from the starting position to the point where the plunger disk rests on the insert shell for pushing out of the holding tool, the displacement path from the point at which the insert shell is released from the holding tool to its rest on the outer shell and then to the position in which the plunger disk completely pushes the insert shell into the outer shell up to the clamping seat.

15 is pressed in.

In order to offer the surgeon the plunger in a defined starting position, the plunger is held in a position that can be overcome by applying force. The plunger can be held in a force-locking or form-locking manner. The force-locking positioning can be achieved, for example, by a conical clamp. A form-locking positioning can be created, for example, by a circumferential groove and a bead engaging in this groove or by engaging springy slats. Fixation in a starting position can also be achieved by combining force-locking and form-locking positioning.

The use of the instrument in the medical field requires that the instrument is made of a sterilizable material. Since sterilization can be carried out using both hot steam and ionizing radiation, such as gamma rays, high demands are placed on the material. The material

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The lamellae must have the same elasticity after sterilization as before sterilization so that the material does not break during handling and when inserting the insert tray.

Furthermore, the material must be resistant to aging. This means that the material must not lose its elasticity during storage, which can last up to five years for medical components.

Furthermore, the material must be biocompatible, i.e. it must not generate any abrasion that could affect the healing process or damage the bone tissue during surgical use.

All of the above-mentioned properties take on particular importance when, according to the invention, the instrument is packaged in a sterilized manner together with an insert tray held by it. The instrument according to the invention makes it possible for the insert tray to be packaged for storage in a sterile atmosphere, ready for use, together with its handling tool. Possible longer storage, for example up to five years, requires that the material is resistant to aging and does not lose its elasticity during storage. One material that has these properties is polyetheramide, for example.

The innovation is explained using practical examples.
Show it:

Figure 1 shows the instrument according to the invention with an insertable

Insert tray in the holding tool,

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Figure 2 is a top view of the instrument with an inserted

Insert tray,

Figure 3 shows an embodiment in which the plunger is clamped into its

Position is held,

Figure 4 shows a force-locking positioning of the plunger by means of a spring,

Figure 5 shows a positive positioning of the plunger by means of a

Groove engaging bead,

Figure 6 a positioning of the plunger by means of a wedge and

Figure 7 is a view of the wedge.

The representation in all figures is on an enlarged scale. In Figure 1, 1 denotes the instrument according to the invention for handling and inserting the insert shell 2 held by it. The instrument 1 consists of a holding tool 3 and a plunger 4 slidably mounted therein. The holding tool consists of a hub 5, in the bore 6 of which the plunger 4 is slidably mounted concentrically to the center line 7.

In the present embodiment, the holding tool 3 has three lamellae 8 which, comparable to a paddle wheel, extend spirally from the hub 5 outwards. The angular distance α of the lamellae 8 is the same in the present embodiment, but this is not absolutely necessary. The profile of the lamellae 8 tapers outwards from the hub 5. The insert shell 2 is held in a clamping fit. This is formed by stop surfaces 9 which each extend radially inwards from the lamellae 8, which can be seen from the right angle 10. Perpendicular to a

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A claw 11 extends from the stop surface 9 in the direction of the center line 7, which claw has a contact surface 12 in the radial direction, with which it rests on the tapered outer surface 13 of the insert shell 2. In order to be able to overlap the outer edge when the insert shells have different outer diameters, the claws 11 each have an undercut 14. In order to enable precise positioning and alignment of the insert shell 2 to the outer shell, the contact surfaces 15 of the claws 11, the end faces that are placed on the end face 16 of the outer shell 17 (Figure 2), are perpendicular to the center line 7. Each extension of the contact surfaces 15 intersects the center line 7 at a right angle 18. The claws 11 also all have the same length.

The insert shell 2 is pressed out of the holding tool 3 by means of the plunger 4. The plunger 4 has a plunger disk 19 on its end facing the insert shell 2. The outer circumference 20 of the plunger disk rests in a ring shape on the joint surface 21 of the insert shell 2. The contact surface is concentric with the center line 7 of the plunger 4, as can be seen from Figure 2. This ensures that the pressure force is evenly introduced into the insert shell.

In order to be able to actuate the tappet 4, the shaft 24 has a further disc 22 at its end facing away from the tappet disc 19. If a force is exerted on this actuating disc 22 in the direction of arrow 23, the tappet disc 19 presses onto the insert shell 2. The lamellae 8 give way due to their elasticity, they are pressed outwards and the claws 11 release the insert shell 2.

Figure 2 shows a top view of the instrument 1, which carries an insert shell 2 in the holding tool 3 and is placed on the front side 16 of an outer shell 17 for the insertion of this insert shell 2. For the sake of clarity, the actuating disk 22 is omitted. It can be clearly seen how the lamellae 8 extend spirally from the hub 5 outwards. Because the lamellae are stressed in the radial direction and the lever arm is long due to the spiral shape

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is, a high clamping force and thus a secure holding of the insert shell can be achieved. Furthermore, the spiral shape of the lamellae offers the possibility of holding insert shells with different external diameters with the same holding tool. For example, it is possible to hold insert shells with an external diameter of 30 mm to 34 mm with one and the same holding tool. This makes it possible to limit the number of holding tools for insert shells with different external diameters to a few types. It is not necessary to have a separate instrument for each of the different external diameters of the insert shells.

&iacgr;&ogr; Figures 3 to 6 show embodiments for fixing the tappet in an initial position before inserting the insert shell into the outer shell. The features that correspond to the previous embodiment are designated with the same reference numerals.

The structure of the instruments shown in the figures is the same in all embodiments, apart from the respective embodiments concerning the positioning of the plunger 4 in its initial position.

In Figure 3, the tappet 4 is held in its initial position by means of a conical clamp in the hub 5. The shaft 24 of the tappet 4 is conically thickened in a region 25 above the tappet disk 19, the conicity 26 in the present embodiment being approximately 1 to 2 degrees and increasing towards the tappet disk 19. Because the bore 6 in the hub 5 remains constant in diameter, a clamping between the tappet 4 and the hub 5 within the bore 6 is achieved by the elasticity of the material of the hub 5 in the region 25.

While the shaft 24 and the tappet disk are made in one piece from a plastic part, the actuating disk 22 is placed on the shaft. This makes it possible to push the holding tool 3 onto the shaft. The actuating disk 22 is connected to the shaft 24 in a form-fitting manner. The free end 27 of the

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The shaft is offset from the latter and has a circumferential groove 28. A bead 30, which runs around the opening 29 in the actuating disk 22, engages in this groove. By pressing the actuating disk 22 onto the shaft 24, the bead 30 engages in the groove 28 and thus fixes the actuating disk 22 onto the shaft 24.

The overall height of the instrument 1 is also shown in Figures 3 to 6. The overall height should be of an optimal size due to the joint packaging with an insert shell already held in the holding tool 3.

The height 31 of the instrument 1 is determined by the thickness 32 of the actuating disk 22 and the thickness 33 of the tappet disk 19, the height 34 of the

&iacgr;&ogr; holding tool 3 and the displacement path 35 of the plunger 4 relative to the hub 5 when inserting an insert shell. The displacement path 35 must be coordinated with the required displacement path in the outer shell, particularly when the insert shells have different diameters. This is made up of the displacement path that the plunger travels from its initial position in which it is held to its position in the insert shell, the path that the insert shell travels from the holding tool to its position on the outer shell, and the path that the insert shell still has to travel to produce the clamping fit in the outer shell. However, the displacement path 35 is generally chosen to be greater than these combined paths in order to make it easier to handle the insert shell with the instrument when positioning it on the outer shell and to enable the insertion of insert shells with different outer diameters.

Figure 4 shows an embodiment in which a spring 36 surrounding the shaft 24 is arranged between the holding tool 3 and the actuating disk 22 of the plunger 4. This spring is under pre-tension and thus holds the plunger 4 in its initial position.

Figure 5 shows an embodiment for a positive holding of the tappet 4 in its initial position. At the transition of the shaft 24 to the tappet disk 19,

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an annular groove 37 in the shaft 24. The holding tool 3, on the other hand, has a bead 38 running in the bore 6 at its end facing the tappet disk 19. This bead 38 engages in the groove 37. By applying force to the actuating disk 22, the bead 38 can be pressed out of the groove 37.

According to Figure 6, a safety wedge 39 must first be removed before the instrument 1 can be operated. In addition, but not necessarily, a conical clamp 26 of the shaft 24 in the bore 6 of the hub 5 can be provided.

In the present embodiment, the safety wedge 39 is U-shaped. One leg 40 of the safety wedge 39, which is made of elastic material, rests with its broad side 41 on the actuating disk 22, while the other leg 42 rests with its broad side 43 on the holding tool 3.

Figure 7 shows a detailed view of the safety wedge 39. The legs 40 and 42 each have a slot 44 and 45 respectively. These slots 44 and 45 are widened in their entrance area in a funnel shape 46 and 47 respectively. This makes it easier to insert the safety wedge 39 between the actuating disk 22 and the holding tool 3. The safety wedge 39 is inserted until the shaft 24 snaps into a recess 48 provided for this purpose in the legs 40 and 49 respectively in the legs 42.

In order to be able to actuate the plunger 4, the locking wedge 39 is pulled out between the actuating disk 22 and the holding tool 3. If a conical clamp 26 is also provided, this holds the plunger 4 in its position until a sufficient force is exerted on the actuating disk 22 to release the clamp.

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Claims (11)

1. Instrument for handling and inserting an insert shell into an outer shell of a two-part joint socket prosthesis with a holding tool which has at least three elastic lamellae for releasably holding the insert shell to be inserted, wherein a displaceable tappet is mounted centrally in the holding tool, which has at one end a device for actuating the tappet and at the opposite side a device which can be placed against the insert shell for pressing the insert shell out of the holding tool, characterized in that the lamellae ( 8 ) of the holding tool ( 3 ) extend outwards from a hub ( 5 ) in a spiral shape comparable to a paddle wheel, that the profile of the lamellae ( 8 ) tapers outwards from the hub ( 5 ) and that the insert shell ( 2 ) is held in a clamping fit, formed by a stop surface ( 9 ) extending radially inwards from the lamellae ( 8 ) and a perpendicular thereto, extending in the direction of the Claw ( 11 ) extending along the center line ( 7 ) of the instrument ( 1 ), which rests against the insert shell ( 2 ) in the radial direction and can be placed with its front face as a contact surface ( 15 ) on the front side ( 16 ) of the outer shell ( 2 ) in the axial direction ( 7 ). 2. Instrument according to claim 1, characterized in that insert shells ( 2 ) with differing outer diameters can be used with the holding tool ( 3 ). 3. Instrument according to claim 1 or 2, characterized in that the overall height ( 31 ) of the instrument ( 1 ) is composed of the thickness ( 32 ) of the actuating disk ( 22 ) as a device for actuating the tappet ( 4 ) and the thickness ( 33 ) and tappet disk ( 19 ) as a device for pressing in the insert shell ( 2 ), the dimensions ( 34 ) of the holding tool ( 3 ) and the displacement path ( 35 ), which is composed at least of the path from the release of the insert shell ( 2 ) from the holding tool ( 3 ) to the contact with the outer shell ( 17 ) and the path required to press the insert shell ( 2 ) into the outer shell ( 17 ) until it is clamped into place. 4. Instrument according to one of claims 1 to 3, characterized in that the plunger ( 4 ) is held in its starting position in a position that can be overcome by the action of force ( 23 ). 5. Instrument according to claim 4, characterized in that the plunger ( 4 ) is held in a force-fitting manner ( 26 ; 36 ). 6. Instrument according to claim 4, characterized in that the plunger ( 4 ) is held in a form-fitting manner ( 37 , 38 ; 39 ). 7. Instrument according to claims 5 and 6, characterized in that the plunger ( 4 ) is held in a force-fitting manner ( 26 ) and a form-fitting manner ( 39 ). 8. Instrument according to one of claims 1 to 7, characterized in that the material of the instrument ( 1 ) consists of a sterilizable material. 9. Instrument according to one of claims 1 to 8, characterized in that the material of the instrument ( 1 ) consists of an ageing-resistant material. 10. Instrument according to one of claims 1 to 9, characterized in that the material is a biocompatible material. 11. Instrument according to one of claims 1 to 10, characterized in that the instrument ( 1 ) is packaged in a sterilized manner together with an insert tray ( 2 ) held by it.