HK1025026B - Device for backbone osteosynthesis with offset intervertebral fixing rod - Google Patents

Description

The present invention relates in a general way to devices for osteosynthesis of the spine.

In particular, a spinal osteosynthesis implant is already known from document FR-A-2 659 546 which comprises a pedicular screw with a head in the general shape of a diapason which can directly receive a cylindrical intervertebral ligament rod.

The surgeon has no major difficulty in placing this type of implant if the heads of the different pedicular screws are sufficiently aligned with respect to each other, since the intervertebral ligament can then be placed relatively easily in these heads without excessive strain or twisting.

However, depending on the type of pedicle sighting performed by the surgeon and the orientation of the pedicles, the axes of the pedicle screws are often significantly inclined with respect to the sagittal plane, and therefore the intervertebral ligament housing, defined by the heads of the different screws, may have very marked misalignment.

The solution in this case, which is to deform the rod very significantly to force it to follow the required path, is either impracticable because of the considerable deformation effort that would have to be applied or dangerous because it risks weakening the rod.

There are also various devices for securing and locking a rod in a way that is laterally offset from a pedicle screw.

The Commission has not yet received any information on the application of this Regulation.

US-A-5 575 791 discloses a device according to the preamble to claim 1.

However, all these known devices have drawbacks: some are very heavy, particularly in height, which is quite undesirable and greatly reduces the advantage of the Diapason type screws described above in terms of compactness; others are complex in construction, with many parts; some are also unable, by their structure, to receive rods at a suitable distance from the pedicles, which is otherwise imposed by Diapason type screws; and some of these known devices are unable to provide a sufficiently strong and firm blockage of the rod in relation to the bony anchorage.

The present invention is therefore intended to overcome these disadvantages and to propose simple means, and thus not significantly complicating the placement operations, allowing a conventional type bone implant to be rigidly connected to an intervertebral ligament rod while the rod is significantly displaced from the bone implant.

Another object of the invention is to enable the same type of pedicle screw to be used in all vertebrae, regardless of the magnitude of these displacements.

Another aim is to propose a disjointed fixation of a connecting rod also at the level of a sacred fixation of a particular type.

Thus, the present invention proposes a device for osteosynthesis of the spine as claimed 1.

Preferred, but not limited, aspects of the device of the invention are: the ball joint comprises a seat, generally spherical, provided in a head of the bony anchorage element and a compression ring essentially complementary to that seat, and the first part of the intermediate component comprises a cylindrical appendix received in that ring.The said cylindrical appendix is circular in cross-section.The said cylindrical appendix has a length such that before locking it may slide relative to the ring to vary the interlock between the bony anchorage element and the intervertebral ligament.The said cylindrical appendix has in the region of its free end an expansion designed to prevent the said appendix from escaping freely from the locking.the ring is a split ring and as the extension has a diameter such that the appendix can be engaged forcefully through the ring with temporary elastic deformation of the latter.the first part of the intermediate element includes a housing for a head of the bony anchorage element, and the ball linkage includes a usually spherical seat defined in said housing and a basically complementary spherical wall formed on said head.the means of blocking the ball linkage include a threaded stopper screwed into an opening in said housing opposite to its seat.the said branches of the pince define a clear passage between them to receive the intervertebral linkage rod,and that the said clamping organ is a screw.

Other aspects, purposes and advantages of the present invention will be better illustrated by reading the following detailed description of a preferred embodiment of the invention, given by way of example and made by reference to the attached drawing, on which: Figure 1 is a split cross-sectional view of an osteosynthesis device according to a first embodiment of the invention,Figure 2 is a cross-sectional view after partial assembly of the device in Figure 1,Figures 3 and 4 are cross-sectional views of the device in Figures 1 and 2 in two different locking positions, some organs of the device not being illustrated for the sake of simplicity,Figure 5 is a profile view of a part of an osteosynthetic device according to a second embodiment of the invention,Figure 6 is a front view according to arrow VI of Figure 5,Figure 7 is a back view according to arrow VII of Figure 5,Figure 8 is a top view according to arrow VIII of Figure 5,Figure 9 is a perspective view of the element in Figures 5 to 8,Figure 10 is a perspective view of the osteosynthetic device according to the second embodiment of the invention in the assembled state,and Figure 11 is a cross-sectional view of the device in Figure 10.

In reference to the drawing, and firstly to Figures 1 to 4, a first form of an osteosynthesis device for the spine has been shown, which includes a bone anchorage element 10 in the case of a pedicular screw, with a threaded part 11 intended to cooperate with the bone and a head 12.

This head 12 has two branches 123 in the general shape of a tuning fork, threaded inwards and defining a cavity 121 at the bottom of which a spherical seat 122 is formed.

A threaded stopper 20 having an outer thread 21 and a span 22 usually flat or concave is suitable for screwing between the two branches by means of a tool inserted into a screwing pin 23 as explained below.

Finally, a cap 30 having a top face 31 in which an opening 32 for the above-mentioned screwing tool and a downward-pointing peripheral skirt 33 are formed may be applied to the top of head 12 covering the 123 branches, in particular to prevent the branches from becoming apart during the above-mentioned screwing.

The device in this first embodiment also comprises an intermediate element 40 whose first end, on the right in Figure 1, defines a cylindrical appendix of revolution 41 called a rod, on which is placed a ring 50 having a generally spherical outer contour and a cylindrical cross-section of a diameter slightly greater than that of the rod 41.

The rod 41 has a slightly protruding rib 42 near its free end, which prevents the ring 50 from escaping freely from the rod 41 once it has been placed on it by forcibly crossing the rib.

The middle element 40 has, at its opposite end, a part forming clamp 43 having two branches 43a, 43b arranged one above the other. In the region of their root, the two branches each have a hollow essentially semi-cylindrical, 44a, 44b respectively, these two hollows jointly defining a cylindrical passage 45 oriented perpendicular to the axis of the rod 41.

Between the openings and their free ends, branches 43a, 43b are separated by an interstice 43c and are crossed by two coaxial cylindrical passages, oriented perpendicularly to the passage 45 and the stem 41.

A screwdriver 60 is intended to be inserted and screwed into these passages, this screwdriver typically having a threaded rod 62, a wider head 61 and a screwdriver 63 in the head 61.

It will be noted here that the assembly consisting of pedicle screw 10, threaded cap 20, cap 30 and ring 50 complies with the description in document FR-A-2 659 546.

Figure 2 shows the device in Figure 1 in a partially mounted state.

Thus, the pedicular screw 10 having been previously anchored in a vertebra, the rod 41 fitted with the ring 50 was placed in the inner space 121 of the head 12 of the screw 10, the ring 50 resting at its lower region on the concave spherical span 122 provided at the bottom of this inner space.

Once the intermediate element 40 is in the correct position, the stopper 20 is pre-mounted in head 12, the cap is placed on top of the head and the stopper 20 is tightened with a tool.

The stopper 20 then compresses and deforms the ring 50 to lock the rod 41 in the desired position both translated along its axis and angularly.

The 45-pass is intended to receive an intervertebral ligament (not shown), connected to other identical or different bone anchorages.

The clamping of screw 60 allows the above-mentioned connecting rod to be locked by means of a pinching between the branches 43a and 43b.

Thus, the device described above makes it possible, by means of simple means of manufacture and handling, to fix an intervertebral ligament rod in a disoriented and possibly height-shifted manner, compared with a conventional type implant as described in particular in FR-A-2 659 546, with very large adjustment possibilities obtained on the one hand by choosing the position of the ring 50 on the rod 41 before locking with the stopper 20 and on the other hand by choosing the angular orientation of this same rod 41, also before locking with the stopper 20.

Thus Figure 3 of the drawings illustrates the case where the intersection between pedicular screw 10 and the connecting rod has a certain value L1, while the angle □ between the axis of the pedicular screw 10 and the plane perpendicular to the axis of the rod 41 is non-zero.

In the case of Figure 4, the above-mentioned entrance has been reduced to a value L2 less than L1, while the axis of the pedicular screw 10 is in the plane perpendicular to the axis of the rod 41 (□ = 0□).

In addition, the position of element 40 in relation to the intervertebral ligament can be adjusted if necessary before locking by means of screw 60.

With reference to Figures 6 to 11, an osteosynthesis device for the spine has been illustrated in a second embodiment of the invention, in which elements or parts identical or similar to those of the previous embodiment are designated as far as possible by the same reference marks.

This device consists of a screw 10, especially for anchoring in the sacrum, which consists of a threaded rod 11 topped by a spherical head 13 in which a hollow print 131 for screwing is formed on the side opposite the threaded rod 11.

The device comprises an intermediate element 140 of which part 141 is shaped as a generally hollow spherical body 141 The cavity 1410 defined in this body has a cylindrical part with a tapered 1411 and, below this taper, a concave spherical seat 1412 of the same diameter as the spherical head 13 of the sacred fastening screw 10.

This cavity 1410 opens upwards at the level of the screw and downwards through an opening at the bottom of the spherical seat, which is considerably larger than the section of threaded rod 11 of screw 10.

The inside of the hole 1410 can be bolted from the top by screwing a stopper 20 with an external thread 21 suitable for cooperation with the screw 1411 and, on its upper face, a cross-section 23 for tool tightening.

The element 140 also has, protruding laterally from body 141, an extension forming clamp 143 similar to clamp 43 in Figures 1 to 4.

Specifically, two branches 143a, 143b extend along each other, defining in the vicinity of their root two essentially semi-cylindrical recesses 144a, 144b defining a passage through 145 for an intervertebral ligament rod 70, partially illustrated in Figure 10.

Between this passage and their free ends, branches 143a and 143b are separated by an interstice 143c and crossed respectively by a smooth groove 1431 and a rough groove 1432 to receive a clamping screw 60 identical to that in Figures 1 to 4.

The device is mounted: by inserting the sacral fastening screw 10 into the cavity 1410 of body 141 of part 140 so that its head 13 completes its course in that cavity, the threaded part 11 then protruding below body 141 and capable of being screwed into the sacrum by means of a tool engaged in the print 131;by screwing the stopper 20 into cavity 141 above head 13 without tightening it, then giving the clip 143, receiving the connecting rod 70, the desired inclination relative to the axis of the screw 10, and then sawing, using a tool engaged in the print 23; the head 13 may then be locked firmly relative to the desired position 140; the locking of the clip 145 may also be performed in the previous step 60 (with the help of the clip 70).

This form of construction, for example, allows, with the help of a single piece 140, to make an eccentric connection between a sacral fastening screw and an intervertebral connecting rod, connected by other means, classic in themselves, to vertebrae adjacent to the sacrum.

It will be noted here that the generally rounded shape of the contours of the 140 part (as well as the part forming the 43 clip in the previous form) allows damage to the adjacent tissues to be minimized.

Of course, the various components of the two osteosynthetic devices described above are made of a biocompatible material such as stainless steel or titanium alloy.

Claims (9)

1. An osteosynthesis device for the spine, the device comprising:

   a bone anchor element (10),

   an intervertebral link rod (70) suitable for connecting said bone anchor element to other anchor elements,

   an intermediate element (40; 140),

   a ball-and-socket link (122, 50; 1412, 13) between a first portion (41; 141) of the intermediate element and the bone anchor element (10),

   a clamping link (43; 143) between a second portion of the intermediate element and the intervertebral link rod, and

   locking means (20, 60) for locking the ball-and-socket link and the clamping link,

   which device is characterized in that said clamping link is constituted by a clamp (43; 143) having two branches (43a, 43b; 143a, 143b) extending laterally from the ball-and-socket link, open away therefrom, and holding the intervertebral link rod captive therebetween, and in that first locking means are provided acting on the clamp in the end region of said branches situated, relative to the rod, on the opposite side to the ball-and-socket link, so as to urge said branches towards each other.
2. A device according to claim 1, characterized in that the ball-and-socket link comprises a generally spherical seat (122) provided in a head (12) of the bone anchor element and an essentially complementary compressible ring (50) received in said seat, and in that said first portion of the intermediate element comprises a cylindrical appendix (41) received in said ring (50).
3. A device according to claim 2, characterized in that said cylindrical appendix (41) is of circular section.
4. A device according to claim 2 or 3, characterized in that said cylindrical appendix (41) is of a length such that prior to locking, it is capable of sliding relative to the ring (50) to vary the axial offset between the bone anchor element (10) and the intervertebral link rod (70).
5. A device according to claim 4, characterized in that said cylindrical appendix (41), in the region of its free end, presents an enlargement (42) for preventing said appendix from escaping freely from the ring (50) prior to locking.
6. A device according to claim 5, characterized in that the ring (50) is a split ring and in that the enlargement (42) has a diameter such that the appendix can be engaged by force through the ring with temporary elastic deformation thereof.
7. A device according to claim 1, characterized in that said first portion of the intermediate element has a housing (141) for a head (13) of a bone anchor element, and in that the ball-and-socket link has a generally spherical seat (1412) defined in said housing and an essential complementary spherical wall formed on said head (13).
8. A device according to claim 7, characterized in that the means for locking the ball-and-socket link comprise a threaded plug (20) screwed into an opening of said housing remote from its seat (1412).
9. A device according to any one of claims 1 to 8, characterized in that said branches (43a, 43b; 143a, 143b) of the clamp define an empty passage (45; 145) between them suitable for receiving the intervertebral link rod (70), and in that said clamping member is constituted by a screw (60).