ITAR20120035A1 - INTERVERTEBRAL PROSTHESIS, PARTICULARLY FOR MINOR-INVASIVE SURGERY PERCUTANEOUS INTERVENTIONS. - Google Patents

Description

"INTERVERTEBRAL PROSTHESIS, PARTICULARLY FOR PERCUTANEOUS MINIMALLY INVASIVE SURGERY"

DESCRIPTION

The present invention relates to an intervertebral prosthesis, particularly for percutaneous minimally invasive surgery.

Numerous pathologies affecting the vertebral column and, in particular, affecting the intervertebral discs are currently known in the medical field.

Some of these pathologies produce a degeneration of the fibrous capsule of the intervertebral disc, which reduces its elasticity and is damaged by letting out part of the nucleus pulposus. This phenomenon is commonly known as a "hernia".

There are also other pathologies, of a progressive type, which involve the thinning, over time, of the intervertebral disc due to the loss of its ability to keep water inside. This thinning often also produces thinning of the facet capsules resulting in pain. In some cases, this thinning can lead to the reduction of the medullary canal with a high risk of chronic claudication.

In many cases, the progressive deterioration of the intervertebral disc requires the implantation of an intervertebral prosthesis which essentially replaces the disc itself.

Two basic types of intervertebral prostheses are currently available.

A first type of prosthesis has the main function of favoring the fusion of two adjacent vertebrae. Such prostheses generally comprise one or two bodies made of osteoconductive material which are positioned, by means of a surgical intervention, in opposite positions between two adjacent vertebrae. The materials used for the construction of the two bodies favor the growth and adhesion of the bone tissue so as to cause the fusion of the two vertebrae which can no longer move relative to each other. This type of prosthesis is generally applied to the lumbar vertebrae, which are those subjected to the greatest load given by body weight.

A second, more modern type of intervertebral prosthesis, on the other hand, has the function of replacing a deteriorated disc while maintaining relative mobility between the two adjacent vertebrae. These prostheses comprise two plates, structured to be fixed on the opposite faces of two adjacent vertebrae, between which an articulated structure is interposed that allows the relative physiological movements between the two adjacent vertebrae. The articulated structure can be constituted for example by a spherical joint structured to allow coplanar sliding between the two plates. This allows you to maintain the natural mobility of the vertebrae while simultaneously relieving pain due to contact between the vertebrae.

However, the prostheses of this second type have some serious drawbacks.

One of the main functions of the intervertebral disc is to cushion the loads to which the vertebrae themselves are subjected. However, the aforementioned prostheses are normally manufactured in titanium and polyethylene, and therefore the primary function of cushioning the loads is canceled, with consequent iatrogenic damage localized at the level of the articular facets, such as for example arthrosis. Since these are substantially prismatic or cylindrical bodies whose section is comparable to that of an intervertebral disc, they can be implanted only by accessing the vertebral column from an anterior direction. Access from a posterior direction is in fact prevented by the presence of the vertebral canal and the dura mater, which enclose the spinal cord, as well as by the articular facets, and by numerous bone structures. The implantation of a prosthesis of this type therefore requires to operate the patient in the anterior part and to move the internal organs, as well as the aorta, to expose the vertebral column, incising the anterior ligament of the vertebral column. These are therefore extremely traumatic and risk-free interventions, also in consideration of the fact that they expose the aorta to possible trauma and lacerations.

Furthermore, the anterior surgical approach carries serious risks of urinary incontinence and retrograde ejaculation.

It is also evident that in case of failure of the procedure, the removal of these prostheses is very complicated and often requires two surgical accesses, the first to remove the prosthesis and the second to stabilize the adjacent vertebrae.

Document W02 006/051547 concerns an implantable intervertebral prosthesis to replace a damaged intervertebral disc, through a minimally invasive surgery. In particular, this prosthesis is made up of parts, separated from each other, which can be assembled directly "in situ" to form a discoid structure. These parts are inserted, one by one, by means of a suitable insertion device, between the two vertebrae of interest, so as to fit 1 <1> with each other to form the discoid structure.

However, this known type prosthesis is not free from drawbacks, including the fact that its implant requires anterior surgical access, involving the known problems of displacement of the internal organs previously described and that a posterior surgical access is in any case severely limited. by the presence of bony structures, such as the joint facets, and of the vertebral canal.

The aim of the present invention is to provide an intervertebral prosthesis, particularly for percutaneous interventions of minimally invasive surgery, which obviates the drawbacks and overcomes the limits of the prior art, allowing it to be implanted with posterolateral access to the vertebral column, while also preserving the external fibrous anolus. of the disc and the posterior ligament and, in cases that require it, to be able to remove it with a simple procedure.

Within this aim, an object of the present invention is to provide an intervertebral prosthesis which can be implanted in a much faster and less traumatic manner than conventional prostheses, using the operating technique used daily for positioning intervertebral spacers. suitable for vertebral fusion.

Another object of the present invention is to provide an intervertebral prosthesis which allows to maintain physiological mobility between two adjacent vertebrae.

A further object of the invention is to provide an intervertebral prosthesis which is capable of giving the greatest guarantees of reliability and safety in use.

The aforementioned task, as well as the aforementioned purposes and others which will appear better later, are achieved by an intervertebral prosthesis, particularly for percutaneous interventions of minimally invasive surgery, characterized by the fact that it comprises a plurality of mutually articulated segments, said segments being movable from an operative configuration, in which said segments are arranged together in such a way as to form a discoidal body, to an insertion / extraction configuration, in which said segments are substantially aligned with each other, and vice versa.

Further characteristics and advantages will become clearer from the description of a preferred but not exclusive embodiment of an intervertebral prosthesis, illustrated by way of non-limiting indication with the aid of the attached drawings in which:

- figure 1 is a perspective view of an intervertebral prosthesis, particularly for percutaneous operations of minimally invasive surgery, according to the present invention, in its operative configuration;

Figure 2 is a perspective view of the prosthesis shown in Figure 1 in its insertion / extraction configuration;

figure 2a is a detail on an enlarged scale of a portion of the prosthesis shown in figure 2;

- Figures 3 to 10 show a sequence of phases of implantation of the prosthesis between two adjacent vertebrae.

With reference to the aforementioned figures, the intervertebral prosthesis, particularly for percutaneous operations of minimally invasive surgery, globally indicated with the reference number 1, comprises a plurality of segments, indicated in the figures cited by the numbers from 21 to 28 articulated in such a way to be movable from an operating configuration, in which they are arranged together in such a way as to form a discoidal body 2, as illustrated in Figure 1, to an insertion / extraction configuration, in which the segments 21 to 28 are substantially aligned with each other, as shown in figure 2, and vice versa.

As will be further described below, in their insertion / extraction configuration, the segments 21 to 28 form a succession of articulated and flexible linked elements.

Advantageously, each segment from 21 to 18 is made of an elastomeric material, such as for example silicone.

It should be emphasized that the use of an elastomeric material, in particular silicone, allows to simulate the elastic behavior of an intervertebral disc, both as regards the absorption of compressive stresses and as regards the rotations around three axes. perpendicular, both as regards the relative sliding movements between two adjacent vertebrae between which it is interposed.

More specifically, each segment 21 to 28 has a prismatic conformation, with a substantially triangular or rectangular base, in such a way as to develop between two planes substantially parallel and perpendicular to the longitudinal axis of the discoidal body 2 which they define in their operating configuration.

However, in order to improve the ergonomics of the intervertebral prosthesis 1, the upper and lower faces of each single segment from 21 to 18 are such as to define, in their operative configuration, a discoidal body 2 having an upper surface 2b and a lower surface 2c inclined to each other according to an angle substantially coinciding with the angle formed by the lower articular surface (I) with the upper articular surface (S) of two adjacent vertebrae. This angle varies according to the level of the spinal column to be treated.

Conveniently, the upper surface 2b of the disc-shaped body 2 is formed by the upper faces of the segments 21 to 28 which, in the closed configuration of the disc-shaped body 2, are mutually contiguous and coplanar. Similarly, the lower surface 2c of the discoidal body 2 is formed by the lower faces of the segments 21 to 28 which, in the closed configuration of the discoidal body 2, are contiguous and coplanar with each other.

In the proposed embodiment of the intervertebral prosthesis 1, the discoid body 2 comprises eight segments 21 to 28.

As can be clearly seen from Figure 1, in the proposed embodiment, the discoidal body 2 advantageously has an elongated shape with a front section and a rear section having a greater length than the two lateral sections. A first segment 21 and a fifth segment 25 are therefore intended to define, in the operating configuration, the anterior portion and the posterior portion of the discoidal body 2. A third segment 23 and a seventh segment 27 are intended to define, again in the operating configuration , the lateral portions of the discoidal body 2. Finally, a second segment 22, a fourth segment 24, a sixth segment 26 and an eighth segment 28 are intended to define portions, rounded on their lateral surface, which connect the other segments together. 21, 23, 25 and 27, being substantially triangular based unlike the other segments which have a rectangular base.

With the exception of the two end segments 21 and 28, which are disjoint from each other, the segments 21 to 28 are separated from each other by partial notches made in the thickness of the discoidal body 2. These notches are made according to substantially vertical planes, ie substantially orthogonal to the upper surface 2b or lower surface 2c of the discoidal body 2. The partial notches do not completely separate the segments 21 to 28 from each other, but leave intact intermediate portions, indicated in the figures cited with the numbers from 21a to 28a, connecting each pair of segments from 21 to 28.

More specifically, these intermediate portions 21a to 28a are defined in correspondence with the external side faces of the segments 21 to 28 defining the external lateral surface 2a of the discoidal body 2 in such a way as to define a hinge constraint between each pair of segments 21 a 28 allowing their reciprocal rotations around an axis of rotation substantially parallel to the longitudinal axis of the discoidal body 2.

Advantageously, the intermediate portions 21a to 28a just mentioned, being a single piece with the segments 21 to 28, are made of the same elastomeric material, in such a way as to maintain, in the absence of external stresses, the segments 21 to 28 in the operative configuration due to the elastic properties of the elastomeric material.

In fact, the elastomeric material tends, in rest conditions, to make the segments 21 to 28 assume their operative configuration, defining the discoidal body 2.

Consequently, in the insertion / extraction configuration of the segments 21 to 28, the elastomeric material of the intermediate portions 21a to 28a is elastically deformed. Therefore, in order for the segments 21 to 28 to be kept in the open insertion / extraction configuration, it is necessary to apply a spreading force, for example in correspondence with the two extreme segments 21 and 28.

The intervertebral prosthesis 1 according to the present invention also comprises a plurality of upper and lower plate-like bodies, indicated in the figures cited respectively with numbers from 31 to 38 and from 41 to 48, advantageously made of osteoconductive material.

Said upper plate-like bodies 31 to 38 and said lower plate-like bodies 41 to 48 are associated, respectively, to the upper and lower surfaces of the segments 21 to 28.

In the operative configuration of the segments 21 to 28, the upper and lower plate-like elements are mutually contiguous and coplanar, forming a continuous upper surface 1b and a continuous lower surface 1b of the intervertebral prosthesis 1.

More specifically, the upper plate-like bodies 31 to 38 and the lower plate-like bodies 41 to 48 are independent from each other in such a way as to be released from each other.

In this way the segments 21 to 28 remain free to assume their own operational or insertion / extraction configurations, without being hindered by the presence of the plate-like bodies.

Conveniently, the osteoconductive material of which the plate-like bodies are made preferably has a trabecular structure and allows in a short time to obtain an optimal anchoring of the same to the lower articular surface (I) and to the upper articular surface (S) of two adjacent vertebrae.

Furthermore, it is possible to provide the same upper 31-38 and lower 41-48 plate-like bodies, in correspondence with their faces opposite to those associated with the segments 21 to 28, with a surface provided with a plurality of protruding bodies 50, suitably shaped like a cone, pyramid or other pointed structure, suitable for facilitating the attachment of the intervertebral prosthesis 1 to the bony surfaces of the adjacent vertebrae.

In this way, once the intervertebral prosthesis 1 has been implanted and the correct space is restored, the protruding portions, or the tips, of these protruding bodies 50 go to stick into the vertebral body giving primary stability while waiting for the bone to invade the trabecular structure plate-like bodies, thanks to the os teoconductive properties of the material that composes them.

Furthermore, the intervertebral prosthesis 1 is equipped with means for positioning the segments 21 to 28 able to allow the passage of the segments 21 to 28 from the insertion / extraction configuration to the operative configuration and vice versa, precisely during implantation or removal. of the intervertebral prosthesis 1 in or by the patient.

More specifically, these positioning means comprise an external thread 60, connecting all the segments 21 to 28, associated with the external lateral surface 2a of the discoidal body 2 in such a way as to protrude, respectively, from the first segment 21 and from the last segment 28 with two end portions 61 adapted to be manipulated for the passage of segments 21a to 28 from the operative configuration to the insertion / extraction configuration and vice versa.

In the proposed embodiment, the outer connecting wire 60 is perimeter embedded in the segments 21 to 28 in proximity to the outer lateral surface 2a, more precisely through the intermediate portions 21a to 28a. The relative rotation between the segments 21 to 28 is favored by the presence of the external connecting wire 60: pulling the end portions 61 of the wire favors the rotation of the segments 21 to 28 with respect to the respective intermediate portions 21a to 28a, realizing the operational configuration.

In fact, the simultaneous traction of both the two end portions 61 is able to bring the segments 21 to 28 into their operating configuration, while the traction of only one of the two end portions 61 allows the segments 21 to be unwound. 28 to bring it into its open insertion / extraction configuration starting from the closed operating configuration.

Preferably, the discoidal body 2 has an annular conformation. The annular conformation in fact favors the elastic return of the segments 21 to 28 to the operative configuration.

Advantageously, the segments 21 to 28 can be divided, transversely to the thickness direction, into at least two portions made of elastomeric material of different hardness. In other words, the discoidal body 2 can be constituted by the superposition of two or more layers of elastomeric materials with different characteristics. In this way it is possible to give the prosthesis differentiated and progressive elastic properties. By using, for example, two layers of different hardness, it is possible to obtain a prosthesis that opposes an increasing resistance to the displacement between the two adjacent vertebrae as the extension of the displacement increases. In the same way, the elastomeric insert can be adapted to the necessary space both in height and at different angles.

With reference to Figures 3 to 10, in which a vertebra is shown above which a prosthesis according to the present invention is inserted, the implantation of the intervertebral prosthesis 1 is described below.

Before proceeding with the description of the implant above, it should be emphasized that the upper vertebra of the intervertebral prosthesis 1 has not been represented for greater clarity of the figures.

The intervertebral prosthesis 1, according to the present invention, thanks to the possibility of assuming an insertion / extraction configuration, can be implanted in an absolutely simpler and less traumatic manner than conventional prostheses.

In fact, the intervertebral prosthesis 1, in the insertion / extraction configuration, can be introduced between two adjacent vertebrae from a posterior and lateral zone to the vertebrae themselves.

The insertion between the two adjacent vertebrae can be carried out with the aid of a tubular element, not shown, shaped so as to contain the prosthesis in its open configuration. This tubular element has a trapezoidal-shaped section, which facilitates the insertion of the same between two contiguous vertebrae, also allowing, through a lever effect, the spreading of the same. In this way, a sufficient operating space is created for the positioning of the intervertebral prosthesis 1 between two contiguous vertebrae.

More specifically, the intervertebral prosthesis 1 can be inserted, while it is inside the tubular element, behind the two adjacent vertebrae, on the same side of the two adjacent vertebrae. By progressively advancing the prosthesis out of the tubular element, the segments 21 to 28, as they protrude from the tubular element, move elastically into the closed configuration, gradually approaching the adjacent segment. The prosthesis is then progressively arranged in its closed configuration, shown in the final form in figure 10. The implantation of the intervertebral prosthesis 1 therefore requires only the creation of a reduced access route for the tubular element from a posterior and / or lateral area to the affected vertebrae, and a slight spread of the affected vertebrae to allow the intervertebral prosthesis 1 to freely arrange itself in its closed configuration.

Furthermore, once the segments 21 to 28 are close to being arranged according to the operating configuration, it is possible to grasp the end portions 61 of the external connecting thread 60 and put them in traction to ensure that the same segments 21 to 28 assume the desired operating configuration. In this way, it is avoided that the presence of any residues of biological material between the vertebral bodies, and in particular between the segments 21 to 28, can hinder the correct complete closure, by elastic recall between the segments 21 to 28, of the discoid body 2.

Furthermore, as already mentioned, the external connecting thread 60 can be advantageously used also for the eventual recovery / removal of the intervertebral prosthesis 1.

In fact, by grasping and pulling an end portion 61 of the connecting wire 60, possibly through the tubular element described above, the segments 21 to 28 unwind, passing from the closed operating configuration to the open insertion / extraction configuration, substantially along a reverse the steps for inserting the intervertebral prosthesis 1 illustrated in figures 3 to 10.

In practice it has been found that the intervertebral prosthesis, particularly for percutaneous operations of minimally invasive surgery, according to the present invention, fulfills the intended aim and purposes as it allows it to be implanted through percutaneous operations of minimally invasive surgery.

Another advantage of the intervertebral prosthesis, according to the invention, consists in the fact that it can be implanted percutaneously through posterior, lateral or postero / lateral surgical access.

A further advantage of the intervertebral prosthesis, according to the invention, consists in ensuring both good stability and good mobility of the vertebral joint.

Another advantage of the intervertebral prosthesis, according to the invention, consists in being adaptable to the different characteristics of the implantation site.

A further advantage of the intervertebral prosthesis, according to the invention, consists in the fact that it can be easily removed, with single-access minimally invasive surgery.

The intervertebral prosthesis, particularly for minimally invasive percutaneous surgery, thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

Furthermore, all the details can be replaced by other technically equivalent elements.

In practice, the materials employed, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to requirements.

Claims (11)

R IV E N D I C A Z I O N I 1. Intervertebral prosthesis (1), particularly for percutaneous interventions of minimally invasive surgery, characterized by the fact of comprising a plurality of segments (21-28) articulated together, said segments (21-28) being movable from an operative configuration, in which said segments (21-28) are arranged together in such a way as to form a discoidal body (2), with an insertion / extraction configuration, in which said segments (21-28) are substantially aligned with each other, and vice versa. 2. Intervertebral prosthesis (1) according to the preceding claim, characterized in that said segments (21-28) are made of an elastic material. 3. Intervertebral prosthesis (1) according to claims 1 or 2, characterized in that said discoidal body (2) has an annular conformation able to favor the elastic return of said segments (21-28) to said operative configuration. 4. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that said segments (21-28) are divided, transversely to the thickness direction, into at least two portions made of elastomeric material of different hardness in such a way as to giving the prosthesis differentiated and progressive elastic properties. 5. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that it comprises a plurality of upper plate-like bodies (31-38) and a plurality of lower plate-like bodies (41-48), respectively associated with the upper and lower of said segments (21-28), said upper plate-like bodies (31-38) and said lower plate-like bodies (41-48) being independent from each other in such a way as to be released from each other. 6. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that said upper plate-like bodies (31-38) and said lower plate-like bodies (41-48) have, in correspondence with their faces opposite to those associated with said segments (21-28), a surface provided with a plurality of protruding bodies (50) adapted to favor the attachment of said intervertebral prosthesis (1) to the bony surfaces of the adjacent abutment vertebrae. 7. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that said upper plate-like bodies (31-38) and said lower plate-like bodies (41-48) have a trabecular structure made of osteoconductive material. 8. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that it comprises intermediate portions (21a-28a) for connecting said segments (21-28) defined in correspondence with the external lateral faces of said segments (21- 28) defining the external lateral surface (2a) of said discoidal body (2) in such a way as to define a hinge constraint between each pair of said segments (21-28) allowing their reciprocal rotations around an axis of rotation substantially parallel to the longitudinal axis of said discoidal body (2). 9. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that said intermediate portions (21a-28a) are made of said elastomeric material in such a way as to maintain, in the absence of external stresses, said segments (21- 28) in said operative configuration due to the elastic properties of said elastomeric material. 10. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that it comprises positioning means for said segments (21-28) adapted to allow the passage of said segments (21-28) from said operative configuration to said insertion / extraction configuration and vice versa. 11. Intervertebral prosthesis (1) according to one or more of the preceding claims, characterized in that said positioning means of said segments (21-28) comprise at least one external connecting wire (60) associated with said external lateral surface (2a) in such a way as to protrude, respectively, from the first and from the last of said segments (21-28) with two end portions (61) adapted to be manipulated for the passage of said segments (21-28) from said operative configuration to said insertion / extraction configuration and vice versa.