Expandable implant for the spinal column

Abstract

The invention relates to an expandable implant (11) with an upper plate (12) and a lower plate (16) which extend in the xy plane, which serve for anchoring on/in the vertebral support surfaces, and at least three gears (20, 25, 30) which are coupled to each other, wherein the gears (20, 25, 30) serve to expand the implant (11), and each gear (20, 25, 30) has a threaded spindle (21, 25, 31) and a threaded sleeve with corresponding inner thread (22, 27, 32), wherein the pitch of one thread (31, 32) is different from the pitch of the other threads (21, 22; 26, 27). The invention also relates to an operating instrument (80) for this implant.

Claims

1. A combination of an expandable implant and an operating instrument, the expandable implant comprising an upper plate and a lower plate which extend in the xy plane and which serve for anchoring on/in vertebral support surfaces, the expandable implant further comprising at least three gears which are coupled to each other, wherein the gears serve to expand the expandable implant, each gear having a threaded spindle and a threaded sleeve with corresponding inner thread, wherein the pitch of one thread is different from the pitch of the other threads, the operating instrument being engageable with the expandable implant for use in expanding the expandable implant, the operating instrument comprising a handpiece having a longitudinal axis, a gear drive connected to the handpiece for driving one of the gears of the expandable implant, means for securing the gear drive to the expandable implant, and means for moving the expandable implant laterally relative to the longitudinal axis of the handpiece while keeping the handpiece stationary, wherein the moving means comprises a rotatable toothed wheel portion and wherein the rotatable toothed wheel portion is driven by an actuation rod.

2. The combination according to claim 1, characterized in that the gears, in a plan view (z direction), are arranged on an arc of a circle or in a C shape.

3. The combination according to claim 1, characterized in that two end gears have a different pitch than a central gear.

4. The combination according to claim 3, characterized in that the two end gears have a smaller pitch than the central gear.

5. The combination according to claim 1, characterized in that drive wheels are provided on each threaded sleeve and are coupled to each other.

6. The combination according to claim 1, characterized in that the expandable implant has a portion with a threaded bore for screwing on the operating instrument.

7. The combination according to claim 1, characterized in that the operating instrument further comprises a worm drive and a first toothed wheel, in that the worm drive drives the first toothed wheel, in that the first toothed wheel drives the gear drive, and in that the first toothed wheel and the gear drive lie in one plane.

8. The combination according to claim 1, characterized in that the actuation rod is driven via a knurled screw.

Description

(1) In the drawing:

(2) FIG. 1 shows a perspective view of the implant according to the invention at maximum expansion,

(3) FIG. 2 shows a side of the implant from FIG. 1 in the xz direction,

(4) FIG. 3 shows a side view of the implant from FIG. 1 in the yz direction,

(5) FIG. 4 shows the implant from FIG. 2, but in the non-expanded state,

(6) FIG. 5 shows a perspective view of the implant from FIG. 1, secured on the operating instrument and pivoted in,

(7) FIG. 6 shows the operating instrument with pivoted-in implant from FIG. 5 with trocar,

(8) FIG. 7 shows a view of the operating instrument in the xy direction from above (+z direction),

(9) FIG. 8 shows a view of the operating instrument in the xy direction from below (−z direction), and

(10) FIG. 9 shows the toothed wheel portion of the operating element.

(11) The implant 11 comprises an upper plate 12 and a lower plate 16, of which the outer faces 13, 17 are provided with spikes 14 that serve for anchoring on/in the vertebral support surfaces.

(12) Upper plate 12 and lower plate 16 each extend in the xy direction and are spaced apart from each other in the z direction.

(13) The area of the plates 12, 16 of the implant 11 extending in the −y direction, i.e. “rearwards” in FIG. 1, is referred to hereinbelow as “rear area”, and the area extending in the +y direction is referred to as “front area”.

(14) Between the upper plate 12 and the lower plate 16 there are three gears 20, 25, 30, by means of which the lower plate 16 is movable relative to the upper plate 12, i.e. the implant can be expanded.

(15) Each gear 20, 25, 30 consists of a threaded spindle 21, 26, 31 with an outer thread 23, 28, 33 which is guided in a sleeve 22, 27, 32 with inner thread (cf. FIG. 2).

(16) The outer threads 23, 28, 33 of the threaded spindles 21, 26, 31 are spaced apart from each other. The longitudinal axes of the threaded spindles 21, 26, 31 in the z direction extend parallel to each other and are rigidly connected to the upper plate 12, i.e. the three threaded spindles 21, 26 and 31 and the upper plate 12 with the spikes 14 form the upper implant part 15, which is in one piece.

(17) The lower implant part 35 comprises the lower plate 16 with the spikes 14, and the three sleeves 22, 27, 32 that have inner threads and are mounted rotatably in the plate 16.

(18) The inner curved surfaces of the threaded sleeves 22, 27, 32 are provided with threads which form the spindle nuts for the outer threads 23, 28, 33 of the threaded spindles 21, 26, 31.

(19) Each threaded sleeve 22, 27, 32 also has, on its outer curved surface, a drive wheel 24, 29, 34, which is designed as a toothed wheel. The toothed wheels 24, 29, on the threaded sleeves 22, 27, 32 couple the rotation movement of the three threaded sleeves 22, 27, 32.

(20) The threaded sleeves 22, 27, 32 are mounted rotatably in the lower plate 16. When a rotation movement takes place on a toothed wheel 24 of a threaded sleeve 22, the rotation movement is transferred on the one hand to the central threaded sleeve 32 by the meshing of the pairs of toothed wheels 24, 34, and it is also transferred to the threaded sleeve 27 by the further coupling of the pair of toothed wheels 34, 29. These coupled toothed wheels 24, 29, 34 have the effect that the expansion mechanism is driven with a triple adjustment mechanism.

(21) On the other hand, however, the rotation movement on each threaded sleeve 22, 27, 32 also has the effect that a displacement movement of the threaded spindles 21, 26, 31 relative to the threaded sleeves 22, 27, 32 in the z direction takes place, and thus a displacement of the lower plate 16 relative to the upper plate 12, and thus an expansion of the implant 11.

(22) In this way, the expansion of the implant 11, upon rotation of one of the three threaded sleeves 22, 27, 32, takes place in a smooth movement, and jamming of the threads is avoided.

(23) The rotation movement is introduced into the toothed wheel 24 of the threaded sleeve 22 of the gear 20 by virtue of the fact that a toothed wheel 85 of an operating instrument 80 (to be described in more detail below) engages on the toothed wheel 24 of the gear 20 and introduces the rotation movement into the toothed wheel 24.

(24) In the implant 11 according to the invention, the three threads 20, 25, 30, seen in a plan view, are not arranged in a line but instead in the shape of an arc or “C”. The two threads 20, 25 lie near the ends of the C, while the thread 30 lies at the centre of the C. The three threads 20, 25, 30 are mirror-symmetrical with respect to the yz axis. In the plan view (in the −z direction), the three threads 20, 25, 30 are arranged in the form of a flat isosceles triangle.

(25) If the central thread 30 has a different pitch than the two end threads 20, 25, this arrangement of the threads and the likewise arc-shaped (C-shaped) form of the plates 12, 16 mean that, during the expansion, it is also possible to obtain a slight tilting of the upper plate 12 relative to the lower plate 16.

(26) The pitches of the outer threads 23, 28 of the threaded spindles 21, 26 and the corresponding inner threads of the threaded sleeves 22, 27 are equal and smaller than the pitch of the central gear 30, namely the outer thread 33 of the threaded spindle 31 and the corresponding inner thread of the threaded sleeve 32.

(27) The different thread pitches mean that, during the expansion, the upper plate 12 is lifted less strongly in the front area (area in the +y direction in FIG. 1) than in the rear area of the implant 11 (area in −y direction in FIG. 1), i.e. the distance between the upper plate 12 and the lower plate 16 of the implant 11 is greater at the plate end in the −y direction than at the plate end in the +y direction, i.e. the two plates 12, 16 are slightly “tilted” relative to each other and thus have a lordosis shape (cf. in particular FIG. 3).

(28) In a preferred embodiment, the pitches of the threads 23, 22, 28, 27 of the two outer gears 20, 25 are each 1.0 mm, and the pitch of the central gear 30 is 1.25 mm. However, the pitches can of course also be different from this.

(29) In the non-expanded state (FIG. 4), the distances in the z direction between the upper plate 12 and the lower plate 16 are the same all over, i.e. the planes of the plates 12, 16 extend parallel to each other. A pin 43, 45 with a limit stop 44, 46 is arranged parallel to the longitudinal axes (z direction) of the threaded sleeves and spindles 21, 22, 26, 27, 31, 32 near the central thread 30 in the “rear” area (i.e. in the −y direction) and in the front area (i.e. in the +y direction), wherein each pin 43, 45 with limit stop passes through a respective bore in the upper plate 12 and lower plate 16. At maximum expansion, the head ends of each pin 43, 45 bear on the top face of the upper plate 12 and the limit stops 44, 46 bear on the underside of the lower plate 16, i.e. the pins 43, 45 and limit stops 44, 46 define the expansion movement and additionally serve as a guide.

(30) Since the expansion in the +z direction in the front area, i.e. in the +y direction, is smaller than in the rear area, i.e. in the −y direction, the pin 43 in the rear area is also longer than the pin 45 in the front area.

(31) Two vertically extending portions 50 are provided on the lower plate 16, adjacent to the gear 20, and are rigidly connected to each other via a horizontal portion 51 with a threaded bore 52. The threaded bore 52 serves to secure a screw 78 provided on the proximal end of the operating instrument 80.

(32) The lower plate 16, the two vertical portions 50 and the horizontal portion 51 form a rigid unit. The thickness of the upper and lower plates 12, 16 is relatively small. In addition, the threaded sleeves 22, 27, 32 and the threaded spindles 21, 25, 31 are secured in the plates 12, 16 and pass through these, and each gear consists exactly of one sleeve 22, 27, 32 and one spindle 21, 25, 31. A compact structure with maximum lift is thus obtained.

(33) The upper and lower plates 12, 16 of the implant can have openings through which anchoring screws can be screwed obliquely into the adjacent vertebrae.

(34) At both sides of the threaded bore 52, the horizontal portion 51 has two slightly curved surfaces 55, 56, which serve to position the corresponding surfaces 81, 82 of the securing piece 77 (cf. FIG. 9) at the proximal end of the operating instrument. In this way, with the screw fixed, the implant is rigidly connected to the operating instrument.

(35) The end faces of the threaded sleeves 22, 27, 32 and sleeve-shaped threaded spindles 21, 26, 31 are open, i.e. not covered by the upper plate 12 or lower plate 16. The implant 11 thus has three tubular through-openings extending from the outer face 13 of the upper plate 12 to the outer face 17 of the lower plate 16.

(36) The implant is operated with an instrument 80, which is shown in detail in FIG. 5 ff. The instrument 80 serves both for the securing, screwing in, pivoting in and insertion of the implant 11 and also for the expansion and the fixing of the expansion position.

(37) In order to secure the implant 11 safely on the operating instrument 80 for the subsequent handling, i.e. insertion, positioning, pivoting in and expansion, the instrument 80 is screwed, by means of a locking screw 78 at the proximal end of the operating instrument 80, into the threaded bore 52 of the horizontal portion 51 of the implant 11.

(38) The locking screw 78 is secured non-detachably in a screw thread 79 in a securing piece 77. The securing piece 77 is rigidly connected to the toothed wheel portion 101 described in more detail below (FIG. 9).

(39) The positioning surfaces 81, 82 adjacent to the screw thread 79 correspond to the positioning surfaces 55, 56 adjacent to the screw thread 52, such that the implant 11 is secured rigidly with a form fit on the operating instrument 80.

(40) By screwing the implant 11 to the proximal end of the operating instrument 80, not only is a rigid connection between implant 11 and operating instrument 80 achieved, and thus precise insertion, but also at the same time the toothed wheel 85 located at the proximal end of the operating instrument 80 is brought into engagement with the toothed wheel 24 of the implant. The toothed wheels 85, 24 lie in one plane (xy plane), and the teeth of the wheel 85 engage laterally in the teeth of the drive wheel 24.

(41) The rotation movement of the toothed wheel 85 takes place through rotation of the distal end of a gear rod 90, at the proximal end of which there is a worm drive 91, of which the rotation movement is transferred by means of a further toothed wheel 92 to the toothed wheel 85, which drives the toothed wheel 24 of the implant 11.

(42) The toothed wheels 85, 92 lie in one plane. The worm drive 91 engages laterally on the outwardly pointing teeth of the toothed wheel 92.

(43) By means of this arrangement, a rotation movement of the toothed wheel 85 can be introduced at the proximal end even in the case of a slender configuration of the proximal end of the operating instrument 80.

(44) The gear rod 90 is mounted rotatably in the handpiece 86, specifically in such a way that the gear rod 90 is received in a respective seat 96, 97 in the handpiece 86 near the proximal and distal ends of the rod 90. The rod 90 is secured against falling out by means of the worm drive 91 having a greater circumference than the seats 96, 97, and by means of a limit stop 99 near the proximal end of the operating instrument 80, and by means of the grip 98 at the distal end.

(45) The toothed wheels 85, 92 are mounted rotatably with screws 93, 94 in the handpiece 86. The toothed wheel 92 is much larger than the toothed wheel 85.

(46) In the plan view shown in FIG. 7, the head of the screw 93 lies above the toothed wheel 85. The shank of the screw 93 passes through a bore in the toothed wheel 85. Under the toothed wheel 85, a toothed wheel portion 101 is provided through which the thread of the screw 93 likewise passes (cf. FIG. 8).

(47) When the toothed wheel portion 101 is turned, the portion 101, along with the securing piece 77 connected thereto and also the screw thread 79, is rotated on a circular path about the axis of rotation of the toothed wheel 85, i.e. the shank of the screw 93. Upon actuation of the toothed wheel portion 101, an implant 11 screwed firmly onto the operating instrument 80 can thus be pivoted on a circular path about the toothed wheel 85. In other words, during a rotation movement of the toothed wheel portion 101, the implant 11 at the proximal end of the operating instrument 80 is rotated about the toothed wheel 85 or the screw 93.

(48) The rotation movement of the toothed wheel portion 101 takes place via a toothed rod 102, which is held in the handpiece 86 and which can be moved forwards and backwards via a knurled screw 103.

(49) A forward movement of the toothed rod 102 causes a forward movement of the toothed wheel portion 101 and therefore a rotation movement of the toothed wheel portion 101 and thus a pivoting of the implant 11.

(50) The longitudinal axes of the rod 90, of the toothed rod 102 and of the handpiece 86 extend parallel to each other.