WO2007003243A1

WO2007003243A1 - Bone cutter

Info

Publication number: WO2007003243A1
Application number: PCT/EP2006/004568
Authority: WO
Inventors: Reinhard Graf; Christian Maier
Original assignee: Plus Orthopedics Ag
Priority date: 2005-07-05
Filing date: 2006-05-15
Publication date: 2007-01-11
Also published as: DE102005031402A1

Abstract

The invention relates to a bone cutter, in particular a shaving cutter, comprising at least three cutter elements (12) that are hinged on the free end (10) of a drive shaft (11), in such a way that said elements can be pivoted by an adjusting unit (13) from a radial inner position (II) in relation to the drive shaft (11), away from the latter (11) into a radial outer position (I) or vice versa. The bone cutter is characterised in that the respective cutter elements (12) form part of an umbrella or mushroom-shaped cutter head (14) and can be closed or opened in the manner of an umbrella.

Description

'BONE CUTTER "

description

The invention relates to a bone milling cutter, in particular a Raffelfräser with at least three hinged at a free end of a drive shaft milling elements such that they by an adjustment of a relative to the longitudinal axis of the drive shaft, radially inwardly disposed position away from the drive shaft in a radially outwardly disposed position or vice versa are pivotable.

A bone cutter of the type described is known for example from DE 38 40 466 Al.

To insert a hip socket for a total endoprosthesis, a recess is formed in the acetabulum by a Raffel milling cutter, in which the acetabulum is inserted and fixed there.

For the minimally invasive surgical technique it would be sufficient to make only a very small opening in the tissue in the region of the joint, which is just large enough to bring the acetabulum through the opening in the body. The use of this technique is currently not possible, however, because the grinder is too large to be inserted through such a small opening. In addition, the scraper has on its outside cutting edges for scoring the pelvic bone, which would damage the muscle material sustainably when introducing the router through a small opening. For this reason, a relatively large opening is made up to the pelvic bone to introduce the cutter. As a result, the recovery times are extended extraordinarily.

From the genus-establishing DE 38 40 466 A 1, a rotating and oscillating special milling cutter is known, which is used in the context of endoprosthesis for the production of Ausfräsun- conditions. This special milling cutter has several milling blades distributed over the circumference of the milling cutter, which are reversibly deformable. The milling firmly connected to the free end of a drive shaft of the milling cutter. The other end of the Fräslamellen is connected to a longitudinally displaceably mounted on the drive shaft sleeve. The milling blades thus form a substantially spherical milling head. By moving the sleeve in the direction of the free end of the milling cutter, the flexible milling blades are compressed, so that the diameter of the milling head is increased. When the sleeve is moved away from the free end of the milling cutter, the milling blades are stretched in the longitudinal direction of the drive shaft, whereby the diameter is reduced. This special milling cutter is used to make cut-outs in the bone material in which a hip socket can be stored safely and firmly.

However, due to the reversible deformability, the milling blades are not sufficiently stable in order to provide satisfactory milling results, at least over a relatively long period of time. In addition, even when the sleeve is withdrawn, the milling head still has a relatively large diameter, so that the milling head known from DE 38 40 466 A1 still requires a large opening in order to be introduced into the body and brought to the hip bone.

German Auslegeschrift 1 288 241 discloses a device for undercutting bones which has cutting-steel-like elements that can be inflated in the radial direction. The cutting tool formed from these elements can be inserted into a bone hole or the medullary cavity of the bone and cut through the bone from the inside by applying a radially outward contact pressure. This device is not suitable for making a cutout in the hip bone.

German Offenlegungsschrift 28 34 295 discloses a device for producing conical surfaces on bones, in particular for processing a cylindrically pre-machined femoral head for adapting a hip joint prosthesis. This device comprises an internal cutting edge which can be moved radially inwards or outwards, wherein a certain radial offset with respect to the diameter of the machined bone portion is maintained. This device is specially adapted for processing the femoral head and is also not suitable for the production of cutouts in the hip bone.

The invention is therefore the object of further developing the known from DE 38 40 466 A 1 bone cutter so that it can be introduced through a relatively small opening in the body tissue without causing muscle material get hurt. In addition, the bone milling cutter should be sufficiently stable to be able to produce excisions in the acetabulum precisely and repeatably.

According to the invention, this object is achieved with regard to the bone cutter by the subject matter of claim 1.

The invention is thus based on the idea to design the milling elements in the generic bone cutter such that they are each part of a screen or mushroom-type milling head, wherein the cutting elements are folded or hinged like an umbrella. The application of the umbrella principle means that rigid

Milling elements, and not as previously in the art flexible milling blades, can be used, so that the bone cutter according to the invention is particularly robust and stable. At the same time, the ability to fold in the manner of an umbrella and to be able to unfold the milling elements causes a considerable change in diameter of the milling head. This makes it possible that the milling head is inserted with folded milling elements through a small opening in the body tissue. Once the milling head has arrived at the intended work on the hip joint bone, the cutting elements can be opened so that the milling head occupies the intended in the working position umbrella-like or mushroom-like contour. With the aid of the milling head according to the invention, the application of the minimally invasive surgical technique is also opened up for the implantation of total endoprostheses.

In a preferred embodiment, the milling elements in the unfolded state form a substantially hemispherical umbrella-like contour. This corresponds to the contour of the milling head in the working position, i. in the unfolded state of the hemispherical contour of standard pans, so that the bone cutter is particularly suitable for the preparation of the hip bone for the implantation of standard pans. The milling elements can form a substantially egg-shaped contour in the folded state, which is particularly advantageous for the introduction of the milling head in the body.

In a preferred disclosed embodiment, the free end of the drive shaft has an end portion whose diameter is greater than the diameter of the drive shaft, wherein proximal ends of the cutting elements are distributed over the circumference of the end piece and hinged thereto. The larger-diameter end piece allows secure storage of the proximal ends of the cutting elements. In the end radially arranged slots may be formed in which the proximal ends of the cutting elements are pivotally mounted. As a result, the cutting elements can be sunk in regions in the various positions in the slots, whereby an even more flexible arrangement of the cutting elements is made possible.

To facilitate the assembly of the milling head, the tail can be divided perpendicular to the drive shaft, which in particular the storage of the cutting elements is facilitated in the tail.

Conveniently, the adjusting device comprises a ring which is arranged longitudinally displaceably on the drive shaft and hingedly connected to distal ends of the cutting elements. By moving the ring along the drive shaft along the cutting elements are unfolded or unfolded or folded or folded.

In the ring radially arranged slots may be formed, in each of which guide pins are pivotally mounted, which are each hingedly connected to the distal ends of the cutting elements. By the guide pins is achieved that the distal ends of the cutting elements can be moved relatively far away from the drive shaft when the milling head in the working position, i. is brought into the unfolded position.

For ease of assembly, especially with regard to the bearing of the guide pins in the ring, this can be performed divided perpendicular to the drive shaft.

In another embodiment, the ring is rotatably connected to a nut which is adjustably engaged with an externally threaded portion of the drive shaft. This creates a particularly simple and at the same time robust possibility of adjusting the ring axially along the drive shaft, thus performing the folding or unfolding of the cutting elements.

The male threaded portion may extend at least partially on the side of the ring remote from the free end of the drive shaft. This has the advantage that sufficient space is available to provide a correspondingly long external thread section, so that the ring or the nut connected to the ring can be adjusted by a sufficiently long distance when the cutting elements are pivoted.

In a particularly preferred embodiment, the milling elements each have an arcuately curved arm with cutting edges on the outside, wherein a proximal les Armende with the free end of the drive shaft and a distal end of the arm with the Verstelleinreichung each hinged. It has been shown that the formation of the cutting elements as arcuately curved arms leads to a good milling result, wherein the milling head thereby also has a particularly lightweight construction.

The proximal end of the arms may each extend beyond the pivot point at the free end of the drive shaft and have a cutting edge in this area. This embodiment is particularly advantageous in connection with the introduced in the tail radial contactors, since thereby in the working position of the milling head in use the acetabulum facing surface of the tail is used as part of the cutting tool.

A further improvement is achieved in that the proximal end of two oppositely arranged arms is in each case designed such that in the unfolded state the two proximal ends form a substantially continuous cutting edge with two cutting sections arranged in opposite directions. Thus, the acetabulum in use facing end face of the tail is used in an optimal way for milling.

The invention will be described in more detail below with reference to the accompanying schematic drawings with reference to two embodiments. Show in it

1 is a perspective view of a bone cutter according to a first embodiment of the invention in the working position with unfolded cutting elements.

Fig. 2 shows the milling cutter of Figure 1 in the rest position with folded milling elements.

Fig. 3 is an enlarged view of the milling cutter of FIG. 1 in the region of the free end of the

Drive shaft; Fig. 4 is a perspective view of a bone cutter according to a second embodiment of the invention;

FIG. 5 shows a further perspective view of the milling cutter according to FIG. 4; FIG.

FIG. 6 shows a section through the milling cutter according to FIG. 4; FIG.

FIG. 7 shows a side view of the milling cutter according to FIG. 4; FIG. Fig. 8 is a plan view of the cutter of Fig. 4;

Fig. 9 is a perspective view of the drive shaft with the tail of the cutter of Fig. 4;

FIG. 10 is a detail view of the free end of the drive shaft shown in FIG. 9; FIG.

Fig. 11 is a plan view of the end portion of the drive shaft shown in Fig. 9;

FIG. 12 shows a milling element; FIG.

Fig. 13 is a perspective view of a part of the adjusting device.

In Fig. 1, an inventive embodiment of a surgical Raffelfräsers is shown, as it is mainly used for milling recesses in the acetabulum for the insertion of acetabular cups used. It is also conceivable to use this Raffelfräser for other applications in which bone material or cartilage material must be removed to make room for a prosthesis.

1 is in the working position with unfolded cutting elements 12, i. in a position in which the cutting elements are pivoted away from the drive shaft 11 in a radially outward position I. In the working position the scraper cutter is used to mill out a corresponding cavity. The milling elements 12 form a substantially hemispherical umbrella-like contour. The term "semi-spherical contour" is understood to mean the outline of the milling head 14, which has a screen or mushroom-like design, as can be seen in FIG. 1, the outline or contour being determined by the shape of the milling elements 12.

In the rest position, as shown in FIG. 2, the cutting elements 12 are pivoted into a radially inwardly arranged position II, so that the cutting elements form a substantially egg-shaped contour in the folded state II. In this position II, the roughening cutter can be introduced into the body through a comparatively small opening in the tissue, without muscle material or tissue being damaged by the edges of the razor. In order to change into the working position I or into the rest position II, the cutting elements 12 can be folded in the manner of an umbrella (FIG. 2) or hinged (FIG. 1).

For this purpose, the milling head is constructed as follows:

The free end 10 of the drive shaft 11 has an end piece 15, in particular a disc-shaped end piece 15 that is integrally connected to the drive shaft 11. It is also possible to form the end piece 15 and the drive shaft 11 in two parts. As can be seen in Fig. 1, the diameter of the disc-shaped end piece 15 is larger than the diameter of the drive shaft 11, so that the cutting elements 12 at the free end 10 of the drive shaft 1 1, in particular at the end piece 15 can be hinged. The proximal ends 16 of the cutting elements 12 are distributed over the circumference of the end piece 15. The term "proximal ends 16 of the cutting elements 12" is understood to mean those ends of the cutting elements 12 which are arranged close to the free end 10 of the drive shaft 11. The arranged away from the free end 10 of the drive shaft 11 arranged ends of the cutting elements 12 are referred to as distal ends 17. The cutting elements 12 are formed as arcuately curved arms 24 which engage with their proximal ends 26 formed in the end radial slots. The proximal ends 26 of the arms 24 are pivotally mounted in the radial slots 18, as shown in Figs. 1, 2 can be seen. The distal ends 27 of the arms 24 are hinged to guide pins 21. These guide pins 21 engage in radial slots 20, which are formed in a longitudinally displaceably mounted on the drive shaft 11 ring 19. The ring 19 and the guide pins 21 thereby form an adjusting device 13, with the help of which the cutting elements 12 and arms 24 are folded, i. towards the drive shaft 11, ie. can be moved away from the drive shaft 11. For this purpose, the guide pins 21 are pivotally mounted in the radial slots 20 of the ring 19, so that in total the ring 19 is pivotally connected to the distal ends 27 of the arms 24.

The longitudinal displaceability of the ring 19 is effected by a nut 22 which is rotatably connected to the ring 19 and is adjustably engaged with an externally threaded portion 23 of the drive shaft 11. By turning the nut 22, this is moved axially along the drive shaft 1 1, the nut 22 entrains the ring 19, so that the position of the guide pins 21 and thus the position of the arms 24 is changed. The externally threaded portion 23 extends at least partially on the side facing away from the free end 10 of the drive shaft 11 side 19 a of the ring 19, so that the nut 22 is moved away from the free end 10 of the drive shaft 11 when the milling head is transferred from the working position I in the rest position II.

In the working position I, the ring 19 abuts against a stop, which may be formed, for example, as a shaft shoulder subsequently to the end piece 15. To lock the milling head in the working position I, the ring 19 is clamped between the nut 22 and the shaft shoulder.

Instead of the nut 22, another suitable displacement element or a latching element can be used to fix the ring 19.

For ease of assembly, the disc-shaped end piece 15 and the ring 19 are each divided into two, whereby in particular the bearing of the guide pins 21 and the proximal ends 26 of the arms 24 is facilitated.

In Fig. 3 is particularly well seen that the proximal end 26 of the arms 24 each extend beyond the pivot point at the free end 10 of the drive shaft 11 addition. In addition to the cutting edge provided on the outside of the arms 24, a cutting edge 28 is likewise provided in the region of the arms 24 extending beyond the pivot point. In the unfolded state I, the proximal ends 26 of the arms 24 are arranged at least in regions over the face of the end piece 15 facing the bone in use. Since the proximal ends 26 of the arms 24 are each provided with a cutting edge 28, thereby the entire surface of the milling head is used as a cutting tool.

FIG. 3 further shows that the proximal end 26 of two oppositely disposed arms 24 ', 24 "is designed such that in the unfolded state I the two proximal ends 26 have a substantially continuous cutting edge 29 with two cutting edge sections 30' arranged in opposite directions. , 30 "form.

The provided on the outside of the arms cutting, as shown in Fig. 3, but also in Figs. 1, 2 can be seen wavy, whereby a particularly good Raffeleffekt when removing the bone or cartilage material is achieved.

Overall, the manner of an umbrella folding or folding or folding or clamping of the cutting elements 12 is achieved by an actuating adjustment device 13, wherein in the illustrated embodiment, the axially sliding ring 19 and the guide pins 21 forms a pivotally connected to the distal end 17 of the cutting elements 12 linkage. By means of an axial movement of the ring 19 away from the free end 10 of the drive shaft 11, the distance between the distal end 17 and the drive shaft 11 is shortened by means of the guide pins 21, so that the cutting elements 12 are moved out of the unfolded working position I into the retracted rest position II ,

The invention is not limited to arm-shaped cutting elements 12, but includes all cutting elements that allow a screen-like folding or unfolding movement.

For example, the cutting elements may also be formed with a larger work surface, as shown in the second embodiment of FIG. 4 to 13.

Also in the Raffelfräser according to the second embodiment, the basic idea of forming the cutting elements 12 as part of a shield or mushroom-type milling head 14, realized, the cutting elements 12 are folded or folded or hinged or clamped in the manner of an umbrella.

The Raffelfräser of FIG. 4 also includes a drive shaft 11 having at its free end 10 an end piece 15 whose diameter is greater than the diameter of the drive shaft 11. The end piece 15 is constructed as a hexagonal element, the O berfläche, i. which is slightly curved in use facing the bone end face. At the edges of the hexagonal end piece 15 six cutting elements 12 are hinged, which can be folded out in working position and folded in the rest position. For this purpose, a likewise hexagonal plate 31 is provided, which is mounted axially displaceably on the drive shaft 11. The cutting elements 12 are articulated with their distal end to this hexagonal plate 31. For storage of the cutting elements 12 on the end piece 15, this is provided with two bearing rings 32 on a side edge of the end piece 15, as can be seen in particular in FIGS. 9 to 11. The cutting elements 12 each have on their inner side a bearing bush 33 ', which is arranged between the two bearing rings 32 of an edge of the end piece. The bearing ring 32 and the bearing bush 31 are rotatably connected by a bolt, not shown.

The adjusting device 13 is also formed from bearing rings 34, which are provided in pairs at one edge of the hexagonal plate 31. The connection of the distal end of the cutting elements 12 with the displaceable hexagonal plate 31 is effected by an intermediate joint 35, which is shown in Fig. 13. The intermediate joint 35 has two Bearing journals, which are rotatably connected to the bearing rings 34 on the hexagonal plate 31 on the one hand and with the bearing bush 33 "on the cutting element 12 on the other hand.

The umbrella mechanism of the Raffelfräsers of FIGS. 4 to 13 functions as the mechanism described in detail according to FIGS. 1 to 3.

In the embodiments shown in FIGS. 1 to 13, the drive shaft is designed in a straight line. It is also possible, depending on the access options, to use a curved drive shaft.

Both the Raffelfräser of FIGS. 1 to 3 and the Raffelfräser of FIGS. 4 to 13 has the advantage that the cutting elements can be folded or opened in the manner of an umbrella so that the milling head 14 with folded milling elements 13 easily in a relatively small opening in the body can be introduced to the pelvic bone. There, the milling head is unfolded and takes its umbrella-like or mushroom-like shape, so that the desired cutout can be made. Due to the trained cutting elements 12 and arms 24 of the milling head is particularly stable and robust.

LIST OF REFERENCE NUMBERS

10 free end

1 1 drive shaft

12 cutting elements

13 adjusting device

14 milling head

15 tail

16 proximal ends

17 distal ends

18, 20 radially arranged slots

19 ring

19 a side facing away

21 guide pins

22 mother

23 male thread section

24, 24 ', 24 "arms

25, 28, 29 cutting

26 proximal end of arm

27 distal end of arm

29 continuous cutting edge

30 ', 30 "cutting sections

31 hexagonal plate

32, 34 bearing ring

33 ', 33 "bearing bush

35 intermediate joint

Claims

claims

1. Bone cutter, in particular Raffelfräser, with at least three at a free end (10) of a drive shaft (11) hinged milling elements (12) such that these by an adjusting device (13) from a relative to the drive shaft (11), radially inside arranged position (II) of the drive shaft (11) away in a radially outer position (I) or vice versa are pivotally, characterized in that the cutting elements (12) are each part of a screen or mushroom-type milling head (14) in the manner of an umbrella can be folded or hinged.

2. Bone cutter according to claim 1, characterized in that the cutting elements (12) in the unfolded state (I) form a substantially hemispherical umbrella-like contour.

3. Bone cutter according to claim 1 or 2, characterized in that the cutting elements (12) form a substantially egg-shaped contour in the folded state (II).

4. Bone cutter according to one of claims 1 to 3, characterized in that the free end (10) of the drive shaft (11) has an end piece (15) whose diameter is larger than the diameter in the drive shaft (11), wherein proximal ends (16) of the cutting elements (12) distributed over the circumference of the end piece (15) and are articulated thereto.

5. Bone cutter according to claim 4, characterized in that in the end piece (15) radially arranged slots (18) are formed, in which the proximal ends (16) of the cutting elements (12) are pivotally mounted.

6. Bone cutter according to claim 4 or 5, characterized in that the end piece (15) perpendicular to the drive shaft (11) is divided.

7. Bone cutter according to one of claims 1 to 6, characterized in that the adjusting device (13) comprises a ring (19) on the drive shaft (11) arranged longitudinally displaceable and with distal ends (17) of the cutting elements (12) articulated connected is.

8. Bone cutter according to claim 7, characterized in that in the ring (19) radially arranged slots (20) are formed, in each of which guide pins (21) are pivotally mounted, each with the distal ends

(17) of the cutting elements (12) are hingedly connected.

9. Bone cutter according to claim 8, characterized in that the ring (19) perpendicular to the drive shaft (11) is divided.

10. Bone cutter according to one of claims 7 to 9, characterized in that the ring (19) is rotatably connected to a nut (22) which is adjustably engaged with an external ßengewindeabschnitt (23) of the drive shaft (11).

11. Bone cutter according to claim 10, characterized in that the externally threaded portion (23) extends at least partially on the side facing away from the free end (10) of the drive shaft (11) (19 a) of the ring (19).

12. Bone cutter according to one of claims 1 to 11, characterized in that the cutting elements (12) each have an arcuately curved arm (24) with cutting (25) on the outside, with a proximal arm end (26) with the free End (10) of the drive shaft (11) and a distal arm end (27) with the adjusting device (13) is articulated respectively.

13. Bone cutter according to claim 12, characterized in that the proximal end (26) of the arms (24) in each case extends beyond the pivot point at the free end (10) of the drive shaft (11) and has a cutting edge (28) in this region.

14. Bone cutter according to claim 13, characterized in that the proximal end (26) of two oppositely arranged arms (24 ', 24 ") is in each case designed such that in the unfolded state (I), the two proximal ends (26) is a substantially continuous cutting edge (29) with two oppositely disposed cutting portions (30 ', 30 ") form.