WO2013079753A1

WO2013079753A1 - Device for the treatment of vertebral column disorders

Info

Publication number: WO2013079753A1
Application number: PCT/ES2012/070829
Authority: WO
Inventors: Antonio-magin ALONSO ABAJO; Pedro-hector ALONSO ABAJO
Original assignee: Alonso Abajo Antonio-Magin
Priority date: 2011-12-01
Filing date: 2012-11-26
Publication date: 2013-06-06

Abstract

Device for the treatment of vertebral column disorders, comprising an element in the form of a continuous bar extending along a longitudinal axis and having three different parts, namely: a first part which extends through the body of two adjacent vertebrae and the intervertebral disc separating same and remains secured in the distal vertebra; a second part forming a continuation of the first part along the longitudinal axis, which extends through a vertebra and an intervertebral disc, remaining secured in the disc, said second part forming the middle section on the longitudinal axis of the bar-shaped device; and a third part forming a continuation of the second part along the longitudinal axis of the device, which extends through the body of a proximal vertebra and remained secured in same. The device can extend through two adjacent vertebrae and the intervertebral disc separating same, and it provides complete stabilisation of the vertebral segment, as either a rigid system or a dynamic system. The device can be implanted in the vertebral column using a percutaneous surgical procedure.

Description

DEVICE FOR TREATMENT OF PATHOLOGIES IN THE COLUMN

VERTEBRAL

OBJECT OF THE INVENTION

The present invention is a device for treating pathologies in the spine. It is within the field of devices used for instrumentation, fixation and prostheses of the spine.

The present invention comprises a set of pieces that allow two possibilities that are either to stabilize the vertebral segment in a totally rigid way or to stabilize the vertebral segment allowing limited movement of the vertebral segment. In both cases a percutaneous approach is used.

The name of the device (vertebra - intervertebral disc - vertebra or reduced VEDISVER) has its origin in the fact that the device is created with the necessary characteristics to cross two adjacent vertebrae and the intervertebral disc.

It is an invention designed to be implanted by percutaneous surgery and not by open surgery, although the set of pieces can also be implanted by open surgery. STATE OF THE CURRENT TECHNIQUE

Low back pain is the most common cause of casualties and disabilities in the western world behind the common cold. The origin of pain in the vast majority of cases comes from the intervertebral disc when it becomes incompetent.

The spine (CV) is a dynamic system composed of rigid elements (vertebrae) and elastic elements (intervertebral discs, ligaments and muscles). The muscles provide movement by acting on the vertebrae, which can be moved harmoniously if the joint elements work correctly and are not damaged. The set formed by two contiguous vertebrae and all ligament elements that hold them together is called the vertebral segment (SV).

Within the vertebral segment, the intervertebral disc supports 82% of the loads or weights that go down the spine (Panjabi MM. Biomechanical evaluation of spinal fixation devices, Spine, 1988). On the back of the vertebrae are the two posterior joints (apophysis) that transmit the other 18% of the charges, 9% each. (Panjabi MM, 1988).

If there is a failure of the vertebral bone or ligaments, when making movements, the vertebral segment is unable to completely hold the two vertebrae and excessive amplitude will occur in the movements. This amplitude will be greater than what the physiological limits allow. In this case we talk about instability of the spine because the balance of the vertebral segment is lost. In order to restore the mechanical properties of the disc and thereby relieve pain, a multitude of instruments and devices have been developed to implant in the spine.

All these instrumentation systems have been designed to correct pathologies of the spine. Pathologies may have an origin:

■ Traumatic (fractures, dislocations, herniated discs).

^■ Congenital (deformities such as scoliosis, kyphosis, etc.).

^■ Degenerative (arthritis and osteoarthritis of the spine).

^■ Infectious (discitis, spondylitis).

^■ Tumor.

These pathologies can affect the dorsal or lumbar cervical spine.

In the current state of the art, attempts are made to solve spinal injuries by placing devices in two different ways, one through the pedicles of the vertebrae and the other placing the devices between the two vertebrae occupying the disc space. In both cases, the placement in the human body of the different devices is done using three different surgical techniques.

Types of surgical procedure on the spine: 1.- Open surgery. Wide incisions are made and the part of the spine where the device with direct visualization is implanted is exposed. Using this technique, the device is placed directly. The spine can be accessed by different routes: anterior, anterolateral, posterior and posterolateral.

With open surgery you can place almost all devices (disc prostheses, intersomatic fixators, transpedicular fixators, etc.)

2 - Minimally invasive surgery. It is an open surgery that uses small incisions and exposures. It is less aggressive than open surgery. With this type of surgery, many devices (disc prostheses, intersomatic fixators, transpedicular fixators, etc.) that have been specifically designed for placement by this route can also be placed.

When the open surgery technique or minimally invasive technique are used to place these vertebral devices, both techniques have several disadvantages, and some of them are as follows:

❖ Require general or epidural anesthesia. ❖ They require sectioning muscles, ligaments and fascia to reach the spine.

❖ They cause blood loss sometimes abundant.

❖ They need several days of hospitalization and they need several weeks or months of recovery.

To reduce the above problems, percutaneous surgery has been devised.

3.- Percutaneous surgery. To perform a percutaneous surgery, a guide needle with a trocar is inserted, leaving it in the position that the device will then occupy. Dilators are introduced through the needle one over the other, until the dilator is placed with the appropriate diameter to be able to introduce the desired device. Once the appropriate dilator is placed, all the previous dilators and the guide wire are removed. The last dilator that is hollow inside is used as a working channel.

From there, all the surgery is done through that dilator. Using this percutaneous technique, the area being operated cannot be seen directly and therefore X-rays should be used to position and guide the position of the device. The diameter of the pieces to be placed cannot be larger than the working channel (dilator).

At present with percutaneous surgery you can:

- Implement transpedicular fixation systems. These systems require introducing four working channels (dilators) and four skin incisions to place the 4 transpedicular screws that are then joined with two bars one on each side.

- Implement some fixation systems inside the disc (intersomatic screws or intersomatic boxes).

Vertebroplasties, kyphoplasty (introducing cement into a vertebra) or nucleoplasty (puncturing the disc and treating with radiofrequency or injecting some substance into the disc such as ozone, discogel or chymopapain) can be done.

Types of devices used to correct instability in a segment of the spine When an item is injured, the rest of the system has a margin of compensation. Small lesions do not affect the whole because they can be compensated, but if the lesions are large, they cannot be compensated and in the movements excessive displacements occur or outside the limits of normal vertebrae.

This is what is called instability of the spine and is translated by symptoms such as pain in the lumbar region. Since the intervertebral disc contributes 82% in the distribution of loads that pass through the intervertebral column (Panjabi MM. Biomechanical evaluation of spinal fixation devices, Spine, 1988), the intervertebral disc is paramount in maintaining vertebral stability.

If a disc is injured to try to solve the disc problem, there are currently two different methods. One method is to fix the vertebral segment to block the movement of that vertebral segment. Rigid stabilization systems try to achieve this goal.

The other method is to stabilize the vertebral segment but so that a very limited movement is possible. This is intended to be achieved through dynamic stabilization systems.

According to the current state of the art, both the stabilization of the two vertebrae rigidly and the stabilization of the two vertebrates dynamically are generally performed with three types of surgical instrumentation systems:

Or four transpedicular screws are implanted that join with two bars (transpedicular systems).

Or the intervertebral disc is removed and, once removed, some intersomatic screws or boxes (interbody systems) are implanted in the disc space. > Or the two previous systems are used at the same time (circumferential system that is only used in rigid systems).

These surgical instrumentation systems are implanted so that the loads or weights that pass through the spine are transmitted from one vertebra to another.

Rigid stabilization systems of the spine

As discussed in the previous section, these surgical instrumentation systems can normally be grouped into the following surgical instrumentation systems:

1. - Transpedicular fixations.

2. - Intersomatic fixations.

3. - Circumferential fixations, which suppose the sum of the two previous fixations (transpedicular and intersomatic) and try to achieve a complete blockade of the segment.

4. - Previous fixings with plate.

1.- Transpedicular fixation systems: In these fixings, for a vertebral segment they need to place 4 screws and two bars with the corresponding connections. They can be placed using percutaneous surgery or using open surgery.

From the point of view of biomechanics, to transmit the weight from one vertebra to the other, the pieces are subjected to torsional forces that multiply the transmitted weight several times. Therefore the necessary thickness of the screws and bars to avoid fatigue and breakage of these screws must be greater than necessary to support only the normal weight of the person. It also requires that the bone be of good quality to prevent the screws from moving inside the vertebrae.

Examples of these devices are patents:

ES 2 011 846 (Surgical Surgical Industries) 02/16/1990

ES 1 039 236 U (Lafitt SA) 12/1/1998

ES 2 191 775 T3 (SYNTHES AG) 09/16/2003 ES 2 336 551 T3 (Interventional Spine, inc) 04/14/2010

To be placed, these transpedicular fixations require in most cases conventional open surgery and have associated the problems of open surgery. A small number of devices are designed to be placed with minimally invasive surgery and in these cases their implantation in the human body requires two 3-4 cm incisions in the back, one on each side of the spine. Although it is called minimally invasive, it is necessary to open and cut muscular and ligamentous structures. Subsequently the tissues that have been cut will have to heal.

At the present time there are transpedicular devices that can be placed percutaneously. For placement they need to make four incisions in the back, two on each side of the spine. In addition its placement requires cutting the dorsal fascia and muscle tissue inside to be able to introduce the bars that join the different screws and assemble the system. For these reasons, although surgery is called percutaneous, it is a rather aggressive surgery that requires cutting many tissues.

2.- Intersomatic fixation systems: In these fixations the devices are placed in the place occupied by the intervertebral disc. First, the surgical removal of the intervertebral disc and part of the vertebral plates of the two vertebrae to be fixed is performed. The device, which can be an intersomatic box, a simple screw or an expansive screw, transmits the weight directly through it, from one vertebra to the other. In this case, the movement of the vertebral segment is not completely eliminated, since they do not block the posterior joints. Once the disc space has completely welded due to bone growth in the disc, then all movement of the vertebral segment is canceled. That takes time, usually from six months to a year, although sometimes that merger is not achieved. To completely block the movement, a wide decortication of the vertebral plates must be performed during surgery. In addition, intersomatic devices must be fully embedded and locked between the two vertebrae to prevent internal movement of these intersomatic fixation systems. Examples of these devices are patents:

US 5,015,247 of Michelson.

US 4,834,757 to Brantigan.

WO 98/48738 Al (DIMSO SA), 1998-11-05.

WO 01/56497 A2 (MICHELSON, Gary K), August 9, 2001.

US 6,368,351 Bl (Bradley J. Glenn et al), April 9, 2002.

WO 99/60956 Al (NUVASIVE INC), December 2, 1999.

The destruction of the plates determines that sometimes the prosthesis is implanted between the vertebrae, reducing the height of the intervertebral disc that has been removed. In cases where the intersomatic device or prosthesis is not properly fitted and locked between the vertebrae, the prosthesis can move and this has serious consequences that sometimes need to be reoperated. So much so that patents have even been developed to hold intersomatic devices within the disc space and prevent this migration: ES 2 177 641 T3 by Gary Karlin Michelson 16.12.2002

The mentioned patents are only a few examples of this type of devices, but there are countless inter-somatic devices to place by conventional or minimally invasive open surgery.

3 - Circumferential fixation systems: It is one more step by which the two systems are added in the same patient; intersomatic and transpedicular. In this case, an intersomatic device and a transpedicular device must be placed, which means a lot of instrumentation and shows that transpedicular systems and intersomatic systems do not solve the problem completely.

These systems use patents of the two previous groups in combination.

4 - Anterior fixation systems with plate: There are devices that implant thick metal plates anteriorly or anterolaterally. These plates are attached to the vertebrae by screws. They are usually used in vertebral trauma when the vertebrae are very damaged.

The implantation of these devices requires an open and very aggressive surgery. Examples of this type of fixation are patents:

ES 2 315 466 T3 (Warsaw Orthopedic, Inc) 01.04.2009.

ES 2 210 372 T3 (Gary Carlin Michelson) 01.07.2004.

After looking at the different types of systems currently in existence, it can be seen that the ideal fixation would be a system that totally blocked the movement between the two vertebrae, which at the same time transmitted most of the weight through it and that did not have risk of fatigue fracture. If we can add that it can be introduced percutaneously, we would be faced with the ideal method of fixation. It would work as a circumferential system, although it would be completely different, and would not require aggressive surgery.

The system described in this patent is a device that completely immobilizes the vertebral segment in the three axes of the space and that can be implanted by percutaneous surgery that in this case will be very little aggressive compared to all current systems.

Dynamic stabilization systems of the spine

During the last 10-15 years, attempts are being made to solve the problem of vertebral instability by placing devices that block movement in part, but do not completely cancel it. These devices allow limited movement of the vertebral segment in order not to reduce spinal movements and, more importantly, avoid long-term instability of adjacent segments, which occurs when fixing a pathological segment with any of the previous systems. In order to stabilize the vertebral segment without completely canceling its movement, we currently have, as in the rigid, intersomatic devices and transpedicular devices.

1 - Dynamic transpedicular systems: Another way of partially conserving the movement of the vertebral segment is by using a transpedicular fixation device that contains in the bars that connect the screws a mobile system that allows small movements of the vertebral segment. These devices are called dynamic transpedicular fixation devices and are usually implanted by open surgery. Examples of such devices are patents:

WO-A-03/094699

ES 2,325,281 T3 of PHUSIS (31.08.2009).

2.- Dynamic intersomatic systems: These systems are called mobile intervertebral disc prostheses. There are a large number of disc prosthesis patents with different characteristics. An anterior or anterolateral disc exposure with open or minimally invasive surgery is required for placement.

Examples of these are patents:

WO 2006/058281 A2 (GLENN BRADLEY J ET AL), 1 Jun 2006.

ES 2 303 045 T3 (Krisna, Manoj and Friesem, Tai), January 15, 2004

ES 2 310 255 T3 (Coppes, Justin K et Al), 25 05 2005.

DESCRIPTION OF THE INVENTION

The invention relates to a device for the treatment of pathologies in the spine that cause instability between two or more vertebrae of the spine or an alteration of the intervertebral disc, these pathologies being of congenital, traumatic, degenerative, infectious or tumor origin .

The proposed device directly fixes the vertebral bodies together with the disc and is totally different from both transpedicular and intersomatic fixation systems that currently exist. By means of the device and by the technique explained in this patent, the vertebral segment is given more stability than the stability offered by the transpedicular systems and by the current intersomatic systems. The device comprises rod-shaped elements that are introduced through the bodies of the two vertebrae to be stabilized and the disc that joins them, to give rise to a stable fixation to a vertebral segment.

The surgical method to place the device is performed with percutaneous surgery, which can be unilateral (making only one incision and entering only on one side of the spine with a single rod-shaped element) or bilateral (making two incisions, entering through both sides of the spine and using two bar-shaped elements). For the placement of the device by surgical instruments, the back or side of the vertebra is accessed with an orientation directed towards the center of the disc to be stabilized. Subsequently, the body of that vertebra, the intervertebral disc and the body of the adjacent vertebra are perforated and the device is implanted without the need for open surgery.

The first tool used during the percutaneous surgery procedure is a cannulated trocar that allows to reach the center of the disc from one side or from both sides in case of using two rod-shaped elements. Through the cannulated trocar, a long metal rod 50-60 cm long is passed through the center of the intervertebral disc. This metal rod serves as a guide in the next steps of the surgery.

On the metal rod they are superimposed (following through its outer part) dilators of progressively larger diameters, until a dilator with the appropriate diameter to the implant is placed. This last dilator will serve as a working channel and will have a diameter of 6 to 14 mm and a length of 200 to 400 mm. The dilator separates the skin and muscles until it reaches the vertebra. Subsequently, the device will be introduced in the form of a bar through this last dilator that should be hollow.

When using a percutaneous route, only one incision point is available and the rest of the surgery is done using X-ray guidance. The configuration of the device in the form of a bar that extends longitudinally is that which allows the insertion of this device between vertebrae and that is introduced through the dilator given the tubular configuration of the latter. Finally, the rod-shaped device will be positioned so that it crosses the two adjacent vertebrae and the intervertebral disc so that the vertebral segment is stable.

The implant will consist of one or several rod-shaped elements that give rise to the device of the invention and which are to be placed between the vertebrae. The rod-shaped elements extend along a longitudinal axis and comprise at one end means of linking with a tool to allow the insertion and manipulation of the device by percutaneous surgery. Using this tool it is possible to push, pull, turn and manipulate the rod-shaped element until it can be positioned in its final position. In the description of the embodiments of the invention particular ways of linking between the tool and the bar-shaped element will be shown.

The device presented in this patent may comprise in some of the exemplary embodiments a second rod-shaped element that extends along a longitudinal axis. This second rod-shaped element, if used, has one of the means of linking with a tool to allow insertion and manipulation between vertebrae by percutaneous surgery.

As with the first rod-shaped element, this second rod-shaped element is introduced through another dilator that has been placed on the other side of the spine by percutaneous surgery. If more than one bar-shaped element is used, it is sometimes possible to couple the two bar-shaped elements.

In the embodiments, different surface finishes are incorporated to facilitate insertion by an axial movement coinciding with the longitudinal axis of the bar element or by a turning movement using an external thread.

The device described in this patent can function as a rigid fixation system or allow a small movement functioning as a dynamic stabilization system or as a mobile prosthesis. If in the central part of the bar-shaped element a joint is placed that allows the appropriate degrees of movement to each vertebral segment, we will have a structure anchored in the two vertebrae and that allows only small movements to be made. In each plane the mobility and the angle of rotation can be limited to between four and ten degrees, depending on the vertebral segment to be fixed.

The device described in this patent offers great advantages when compared to current systems as set forth below. Biomechanical advantages

To stabilize a vertebral segment with the device described in this patent, a rod-shaped element that crosses the two vertebrae and the intervertebral disc is placed. Emulating carpentry work, it would be similar to what is done with a dowel or spike that joins two pieces of wood. If a second block or spike is placed in a different plane from the previous one, the solidity of the system would be complete unless the block or spike is broken. The basis of the device is similar to that described for joining pieces of wood, but in this case it will fix the vertebral elements and the intervertebral disc.

By placing a rod-shaped element that crosses and supports the two vertebrae at an angle of about 45 degrees with the plane of the intervertebral disc, if the rod-shaped element passes near the center of the disc we have a structure in which they balance loads in such a way that there will be a counterweight between the forces on one side and those on the other side of the device. As indicated, the transmission of the charges is done through one or two rod-shaped elements whose longitudinal axis forms about 45 degrees with the plane of the intervertebral disc. Therefore the torsional forces on the rod-shaped element are much smaller than the forces suffered by the screws of the transpedicular systems.

In today's transpedicular systems, horizontal screws are used that are connected with vertical bars. The intervertebral disc is canceled and should not transmit any load. Consequently, the charges go through a horizontal screw, passing to the vertical bar that subsequently transmits the load to the horizontal screw of the adjacent vertebra. The greatest effort in this case occurs in the union between the horizontal screw and the vertical bar and this is the place where many screws are broken with the current systems. The device presented in this patent is a rod-shaped element that forms 45 degrees with the plane of the intervertebral disc and that goes inside the vertebrae and intervertebral disc instead of going outside as in the current systems. Therefore the risk of fracture of the device will be almost negligible if we compare it with current transpedicular systems. In addition, part of the weight will continue to pass through the intervertebral disc from one vertebra to the other with the advantage that the set of vertebrae and the intervertebral disc is fixed and forced to transmit that weight. The advantage of all this is that the section of the bar-shaped element can be reduced without losing load transfer capacity. This is particularly important with the spine in motion since in these situations the weight to be transmitted is multiplied by 3 or 4 times if compared to the rest effort. We can summarize the biomechanical advantages in the following sections:

1.- Load sharing on both sides of the device (already discussed above). This means that the torsional stresses on the screw are compensated both in the anteroposterior (AP) and lateral (L) planes.

2 - Smaller section of the device in the form of a bar due to the direction it has once implanted and because it is implanted through the vertebrae and the center of the intervertebral disc. By forming an angle close to 45 degrees with the plane of the disk intervertebrally, the shear stress is much less than with transpedicular devices. Part of the load passes directly through the device and only a small part will have a torque that acts on the device. A device with a diameter of 5 mm will have more resistance than a transpedicular one of 7 mm.

3 - Minimum risk of displacement: Due to the conservation of the intervertebral disc that, although unstable, is still present and will continue to contribute to the transmission of loads. Using the little aggressive percutaneous surgery used to place the device in the form of a bar it is only necessary to remove 7-8% of the vertebral plate, while the rest of the intervertebral disc will remain intact and will continue to function. When comparing the device introduced in this patent with current intersomatic devices, the enormous advantages can be appreciated. In the existing intersomatic devices it is necessary to destroy almost all the vertebral plates and the intervertebral disc to place these devices, whether these mobile prosthetic devices or intersomatic devices that seek to fix the segment. Likewise and as mentioned in the current state of the art, in some cases the intersomatic devices or prostheses do not fit well between the two vertebrae and move, being necessary to reoperate. With the rod-shaped device of the present invention this is impossible.

4 - Possibility of stabilizing the segment with rigid fixation or dynamic fixation as appropriate for the patient. 4.1. Rigid stabilization can be achieved in several ways:

4.1.1- Using a single bar-shaped element. In this case, which is the preferred, but not exclusive, embodiment, a rod-shaped element would be used that would be placed either by displacement according to the longitudinal axis of the device or by rotation around the longitudinal axis. To provide the vertebral segment with greater fixation, larger diameter screws will be used. Therefore, using a 7 mm bar-shaped element, the elements will be fixed more rigidly than if a 5 mm one is used. Likewise, if the rod-shaped element is not threaded and is introduced by displacement along the longitudinal axis of the element, the fixation will also be greater than in the case of using a threaded rod-shaped element that is introduced by rotation. This is because with the rod-shaped element that has no thread and that has longitudinal striations, a vertebra cannot rotate on it and differently than the other vertebra does, so that the entire vertebral segment will move jointly.

4.1.2 Using two bar-shaped elements; one is introduced from the right side and the other from the left. With this method, all movements are blocked and two bar-shaped elements of smaller section than in the previous case would be needed. With diameters of 5 mm for each rod-shaped element would be sufficient.

4.1.3 An embodiment that would give a complete and secure fixation is that which uses two rod-shaped elements, but in this case one of the elements is thicker than the other element and has a transversal perforation in the central area. This central perforation allows placement through the another bar-shaped element from the other side of the vertebra. The second rod-shaped element will be thinner and solid, without longitudinal central perforation. 4.2. Dynamic stabilization: it is achieved using a single rod-shaped element with articulation in its central area. This central joint must allow a controlled and limited movement in the three axes of space. It should also allow damping loads vertically in the direction of weight. In the case of using a dynamic joint it is intended to allow a small movement, limited in three to six degrees in any vertical plane. Healthy lumbar vertebral segments have a range of movements between three and six degrees in most levels and this joint aims to achieve the same effect.

Weight damping is achieved by providing the central area with a closed device. For this closed device there are numerous options, for example:

· A crossbow system.

• A system with a spring inside.

• An elastic structure that admits a certain degree of compression.

The limitation in lateral movements is achieved by limiting the amplitude of the angle at which it can be moved by means of stops in the joint. Subsequently, in the section relating to embodiments, embodiments are described for the central area of the bar-shaped element. These embodiments give the device an operation similar to a mobile intervertebral disc prosthesis. As already indicated above, the devices that are currently on the market and that function as prostheses, require for their placement the total removal of the intervertebral disc, in order to place the prosthesis in the hole left by the intervertebral disc. With the device described in this patent it is not necessary to remove the disc that will remain virtually intact after the operation. Therefore the disc ring will continue to function as before. On the other hand, if most of the load passes through the device once implanted, the functioning ring fibers will perform their work in better conditions because they are subjected to lower loads. In this case, the intervertebral disc ring fibers are not going to have to function in situations of extreme elongation because they have limited movement.

5. - By maintaining almost the entire disk, the disc space will continue to maintain its height and the intervertebral space will not be welded. In current systems, the intervertebral space is welded in the case of rigid systems and this is not a problem because it is what is sought. But in the case of dynamic systems the intervertebral space is welded between 10% and 30% of cases in which a mobile prosthesis is placed, and this is a problem, since after years the prosthesis ceases to be mobile, welds and stops working.

6. - To these advantages must be added the most important, which is that no ligament structure of the spine is broken and all the ligaments that join the vertebrae of the vertebral segment continue to fulfill their biomechanical role. This is because the rod-shaped device is introduced by a very aggressive little percutaneous method. At present there is no mechanism that achieves the same results with so little aggression to the patient's tissues. Medical advantages

The bar-shaped device presented in this patent has many medical advantages for patients and also for surgeons when compared to current methods and current devices that are placed by open surgery and minimally invasive surgery. These advantages are mostly given by the fact that this rod-shaped device can be placed using non-aggressive percutaneous surgery. All the following advantages are compared to the current systems where the problems indicated below occur. Among all the advantages of this new system, the following can be named:

1. There is hardly any risk of infection. The skin incisions are smaller, 1.5 to 2 cm. This avoids problems of seromas, keloid scars, wound cures, etc. The risk of wound infection is greatly reduced because the wounds are smaller, because the interventions are shorter and because the tissues are not exposed to the environment.

2. There is no risk of bleeding. By not cutting fascias or muscles there is very little risk of bleeding. Therefore, there is no need for transfusions or risk of bruising in the surgical bed.

3. No tissue is injured. By not cutting tissues, all structures will remain intact, which will not worsen the stability that will be reinforced when the device is placed.

4. Fibrosis does not occur. Inwardly there will be no scarring on nerve structures (epidural fibrosis) that sometimes complicate open and minimally invasive surgeries.

5. Does not require general anesthesia. It can be performed with local anesthesia and sedation, not requiring the postoperative resuscitation care required by general anesthesia.

6. There is no risk of dura lesion or neurological structures. There will be no problem of cerebrospinal fluid fistulas that occurs in case of dura dura rupture. Nor will there be a risk of neurological lesions because the vertebral canal does not open.

7. It is a reversible procedure. With the same percutaneous technique used to place the device, this device can be removed if the objective for which it was placed is not met.

Economic advantages

1) Hospital savings because operating room time is drastically reduced.

The surgery can be done in thirty minutes, compared to the current systems that need at least two or three hours. Therefore, a lot of time is saved in the operating room (it is saved in facilities and personnel).

2) Hospital savings because the patient's hospital stay time is drastically reduced. With the non-aggressive percutaneous surgery that this device needs, the hospitalization time after the intervention will be 12 to 24 hours compared to the one-week stays required by current devices. Therefore there is a very high saving in hospital stay (rooms, staff ...)

) Savings in pharmaceutical products. No drugs such as analgesics, antibiotics, anesthetics, etc. are needed.

) Savings for social security and for private companies during convalescence. Patients can start normal life within 48-72 hours after the operation. Current methods have a period of convalescence that lasts between two and three months. Therefore, saving for social security and for companies in low time would be very important.

) Advantages for the patient. Patients can begin to perform normal activity from 48-72 hours of the operation compared to the two to three months they need with current systems. This will be a great advantage for freelancers, for workers and for athletes who can work or compete much sooner. It also does not need to carry an external immobilization system (corset, girdle, etc., which are used in some of the current systems).

Brief description of the figures

The figures included in this patent are particular embodiments of the device that are set forth for the understanding thereof. These examples do not exclude other embodiments.

The included figures are not made on a real scale, since the figures serve as examples and are only intended to better highlight the particular details that are important in the device. The description of the figures included in this patent can be seen below: o Figure 1. It shows in diagram a representative drawing of an anteroposterior X-ray projection of two vertebrae (VI and V2) that are joined by the intervertebral disc (Di ). Crossing both vertebrae and the intervertebral disc shows an example of embodiment of the device (D).

o Figure 2. It shows in diagram a representative drawing of a lateral X-ray projection of two vertebrae (VI and V2) and the intervertebral disc that joins them (Di). Crossing the two vertebrae and the intervertebral disc can be seen an example of embodiment of the device (D).

o Figure 3. Schematically shows a drawing of the section of two vertebrae (VI and V2) and the intervertebral disc that joins them. Crossing both vertebral bodies and the disc shows an embodiment with two bar-shaped elements (DI and D2). In this particular embodiment, the two rod-shaped elements are coupled in the central part through a central perforation in the device of greater section (DI), so that the device in the form of a bar of smaller section (D2) it crosses the perforation of the device of greater section (DI). The two bar-shaped elements form a cross-shaped structure once placed. In other embodiments, they do not need to be coupled.

o Figure 4. Shows an example of realization of a bar-shaped element in perspective. The rod-shaped device has a circular cross-section and a cone trunk shape, with one of the bases having a diameter slightly smaller than the diameter of the other base. To place or insert this device inside the vertebrae and vertebral disc, it is necessary to perform a rotational movement around the longitudinal axis (screwed), taking advantage of the external thread (4.1.1 and 4.3.1). The element contains three differentiated parts (4.1, 4.2 and 4.3) with different properties. It also has transverse perforations (4.1.2 and 4.3.2), means of linking with the tool that will be used to introduce the rod-shaped element during the surgical operation (4.3.3 and 4.3.4) and a longitudinal central perforation ( 4.3.5).

o Figure 5. Shows in perspective another particular embodiment with cylindrical shape (instead of cone-shaped) and circular section. It is implanted with a rotation displacement around the longitudinal axis. The last thread pitch of the end that attaches to the manipulation tool has a diameter greater than the diameter of the rest of the thread (5.3.6). Threading is discontinuous for prevent the movement of the device inside the vertebrae (5.1.1 and 5.3.1). The element contains three differentiated parts (5.1, 5.2 and 5.3) with different properties. It also has transverse perforations (5.1.2 and 5.3.2), means of linking with the tool that will be used to introduce the rod-shaped element during the surgical operation (5.3.3 and 5.3.4) and a longitudinal central perforation ( 5.3.5).

o Figure 6. It shows another example of perspective embodiment of a rod-shaped element with a cylindrical shape but whose highlights are the vertices of a regular hexagon that has been taken as the basis for the embodiment. The projections have a longitudinal direction (6.1.1 and 6.3.1). In this exemplary embodiment, the rod-shaped device is positioned by a displacement in the direction of the longitudinal axis. The element contains three differentiated parts (6.1, 6.2 and 6.3) with different properties. It also has transverse perforations (6.1.2 and 6.3.2), means of linking with the tool that will be used to introduce the bar-shaped element during the surgical operation (6.3.4) and longitudinal central perforations, one on each side ( 6.1.5 and 6.3.5).

o Figure 7. Shows, in perspective, another embodiment of a rod-shaped device that is introduced by a displacement in the direction of the longitudinal axis (pressing inwards). This bar-shaped device has along its outer surface ridges or projections that go in the direction of the longitudinal axis and which are continuous (7.1.1 and 7.3.1). The section of this exemplary embodiment of the rod-shaped device is hexagonal. The element has means of linking with the tool that will be used to introduce the rod-shaped element during the surgical operation (7.3.4) and longitudinal central perforations on both sides (7.1.5 and 7.3.5).

or Figure 8. Shows a particular example of embodiment, in perspective, of a cylindrical device. This rod-shaped device has an external thread to be introduced by a rotational movement around the longitudinal axis (8.1.1 and 8.3.1). The particular feature of this exemplary embodiment is that the bar-shaped element has a through hole (8.2.1) in the central area that crosses the bar-shaped element in its entire thickness to thus allow the passage of another device in bar shape of smaller diameter across it.

o Figure 9. Shows an exemplary embodiment, in perspective, of a bar-shaped element with a square section at the ends and circular in the middle. This rectangular bar-shaped element is introduced during percutaneous surgery by a displacement along the longitudinal axis of the element. The projections in the longitudinal direction (9.1.1 and 9.3.1) will help to fix the element once it has been introduced. In this exemplary embodiment, the rod-shaped device is positioned by a displacement in the direction of the longitudinal axis. The element contains three differentiated parts (9.1, 9.2 and 9.3) with different properties. It also has transverse perforations (9.1.2 and 9.3.2) and means of linking with the tool that will be used to introduce the rod-shaped element during the surgical operation (9.3.4).

or Figure 10. This particular embodiment shows a diagram of the central area of a rod-shaped element that is articulated to allow a Limited movement of the vertebral segment once the device is placed and crosses the two vertebrae and the intervertebral disc. This exemplary embodiment would be used to achieve dynamic stabilization of the vertebral segment and uses a bolt (10.2.2) and bowl (10.2.3) system as a joint.

Figure 11. This particular embodiment shows a diagram of the central area of a rod-shaped element that is articulated to allow limited movement of the vertebral segment once the device is placed through the two vertebrae and the intervertebral disc. This embodiment would be used to achieve dynamic stabilization of the vertebral segment and uses a spring system as a joint (11.2.1). This example of realization of the central zone differs from the previous one in that it allows to absorb loads.

Figure 12. This particular embodiment shows a diagram of the central area of a rod-shaped element that is articulated to allow limited movement of the vertebral segment once the device is placed through the two vertebrae and the intervertebral disc. This exemplary embodiment would be used to achieve dynamic stabilization of the vertebral segment and uses an internal elastomer to absorb the loads (12.2.1).

DETAILED DESCRIPTION OF THE INVENTION

The device described in this patent has a basic conformation consisting of a rod-shaped element. This bar-shaped element is a continuous element, but for a detailed explanation of the device three different parts or zones of the bar-shaped element are described. These parts of the device will be referred to hereinafter:

^■ Part one: once placed, part one of the rod-shaped device will be inside the body of vertebra one. This part will be the first part of the element introduced during percutaneous surgery.

^■ Part two: once placed, part two of the bar-shaped device will be inside the intervertebral disc. This part will be the central part of the element.

^■ Part three: once placed, part three of the rod-shaped device will be inside the body of vertebra two. This part will be the last part of the element introduced during percutaneous surgery. In addition this part has means of linking with the tool that is used for the insertion of the element. The rod-shaped element will have the appropriate and necessary length to cross the vertebral segment formed by two adjacent vertebrae and the intervertebral disc that joins them. In general, the rod-shaped element will measure 70 to 100 mm in length, but other different measures may be possible depending on the patient. The section of the bar-shaped element may be any section, although it will generally be a circular or polygonal section to facilitate the construction and handling of these bar-shaped elements. This patent will explain two particular models of realization; a circular section model (fig. 4, 5 and 8) to be introduced by rotation (by screwing) and a square section (fig. 9) or hexagonal (fig. 6 and 7) model to be introduced by a movement of pressure along the longitudinal axis. These examples of realization models do not exclude any other type of polygonal or curvilinear section.

The diameters of the bar-shaped device section will be appropriate for each patient. In the case of placing a rigid device, bar-shaped elements with a minimum diameter of 3 mm can be placed, while the maximum diameter will be limited by the working channel used. In the case of placing a dynamic device, the diameter should be slightly larger than in the case of rigid fixation devices since the bar-shaped elements with a central joint have a greater risk of breakage.

The embodiments shown in the figures do not have the actual dimensions. In addition, in the figures of the embodiments the length does not keep the proper proportion with the section of the element. In the real bar-shaped element the proportion between length and section will be much greater because in the figures presented in this patent the section is enlarged in relation to length. This has been done in order to better visualize the details. Bar-shaped elements can be made of metal alloys. The most appropriate are those of titanium due to osseointegration capacity and magnetic resonance compatibility (RJVIN). Titanium also has other mechanical resistance properties. Bar-shaped elements can also be made of steel and other metal alloys (chrome, cobalt ...). Another type of materials that are appropriate are polymers. The most commonly used is polyether ether ketone (for example, PEEK) as it has elasticity and strength properties that are very similar to bone. If polymers are used for manufacturing, small aligned metal elements must be introduced inside the polymer (at different levels) that will allow us to check the position of the implant in the future and check its physical integrity and that it has not been broken. Other materials that can be used may be ceramics, composites or polyethylenes.

The surface of the materials in the areas of contact with the bone may be laser treated in order to provide a rough surface or a porous surface that facilitates the adhesion with the bone. The surface of the parts of the rod-shaped element that are in contact with the bone of the vertebrae (part one and part three) can be treated with a layer of osteoconductive and / or osteoinductive material in order to accelerate the integration process of the device with the bone tissue of the vertebrae.

Examples of embodiment for insertion by rotation movement around the longitudinal axis (fig. 4, 5 and 8)

These embodiments have a circular section and are introduced into the vertebral segment formed by the vertebrae and the intervertebral disc by means of a rotation movement around the longitudinal axis that bolts the device into the vertebral segment.

As mentioned, the bar-shaped element described in this exemplary embodiment is a unique and continuous element, but for a better understanding of the device, the bar element has been divided into the three parts described in the previous section. Each part of the rod-shaped device can have different perforations and interior and exterior surfaces. In the following embodiments the vertebra one (VI) and the vertebra (V2) will be indicated, and in the figures shown the vertebra one appears above and the vertebra two below, but this can be the other way around and the vertebra one (VI) it may be below vertebra two (V2) depending on whether it is decided to introduce the rod-shaped element from top to bottom as in the embodiment examples or from bottom to top.

Part one (4.1, 5.1 and 8.1). This part, once the device is placed, will be housed in the body of one of the vertebrae (VI) that will be stabilized. The structure of this part presents particularities that are aimed at facilitating the integration of this part with the bone and its fusion with the bone tissue of both the cortex of the vertebra and the spongy. The outer surface has an external thread (4.1.1; 5.1.1 and 8.1.1) that facilitates the insertion of the device by turning the element. The external threading can be continuous as in the case of Figures 4 and 8 of the exemplary embodiments or it can be discontinuous as in the case of Figure 5 where the discontinuous threading forms ridges or projections in a transverse direction to facilitate grip and avoid the movement once bone growth occurs.

Part one may have a hole or central perforation (similar to that seen in Figures 6.1.5 and 7.1.5) that extends along the longitudinal axis. This inner perforation can be threaded or smooth.

Part one may have perforations (4.1.2, 5.1.2 and 8.1.2), which cross in the transverse direction and communicate with the central perforation (similar to that of Figures 6.1.5 and 7.1.5). These transversal perforations are distributed over the surface and have two purposes:

1. Facilitate bone growth through it, allowing the formation of bone bridges between the bone tissue of the vertebra and the bone tissue that grows within the central perforation of the rod-shaped element.

2. Once the device is placed, cement can be introduced through the central perforation, and this cement leaves from the central perforation to the outside through the transverse perforations and extends through the body of the vertebra, thus facilitating a solid union of the piece to the bone once the cement has solidified. This is useful in patients with vertebrae with low bone density.

The shape of this part one can be cylindrical or cone-shaped, with the base continuing with part two slightly larger than the other base to facilitate insertion.

The dimensions of this part one of the rod-shaped element will be those necessary to cover the entire vertebral body between two cortices, the average dimensions of part one of the device will be around 40 mm in length and the diameter may be between 3 to 12 mm depending on the patient and the vertebral level to be fixed.

This part one of the rod-shaped element has two ends, one free end that once placed will be in contact with the anterior or lateral cortex of the vertebra (VI), and the other end that continues with part two. The free end may be a little thinner or sharp to better pierce during percutaneous surgery. In the case of carrying a central perforation, the free end may have this central part plugged or closed.

Part 2 (4.2, 5.2 and 8.2). It is the central part of the bar-shaped element. Once the device is placed in its final position, part two will be inside the intervertebral disc (Di) that joins the two vertebrae, through this intervertebral disc. This part two will continue at each of its ends with parts one and three respectively. This central part presents different embodiments that are what will give the device the different properties and possibilities.

According to the general embodiment, this part two of the device is of circular section and lacks projections and perforations although other configurations are possible. In this case, the outer surface of this part two of the rod-shaped element does not carry perforations. This prevents bone formation at the disc level.

This part can be perforated by means of a longitudinal central perforation or it can be solid to give more robustness to the device. In the case of being perforated in the longitudinal direction, the perforation may cross the entire rod-shaped element along the longitudinal axis, in which case the perforation will also pass through parts one and three, or it may only be partially perforated.

The dimensions of part two vary according to the patient and according to the area of the spine, since the length of this part of the device will depend on the height of the intervertebral disc where this part will be located once it has been implanted. Usually, this part two will have a length of about 20 mm and a diameter that will be the same as the diameter of the rest of the rod-shaped element. There are two embodiments of this part two that give new properties to the bar-shaped element:

• In a specific embodiment, part two of the device has a transverse through hole that crosses it from one side to the other (8.2.1). This transverse through hole can be circular or have any other section. For example, it may have an oval shape with a major axis along the longitudinal axis of the bar-shaped element. This perforation will allow, in some embodiments, to introduce a second rod-shaped element therethrough. This second bar-shaped element will have a smaller section since it can pass through the transverse through-hole of the first bar-shaped element. In this way, the two rod-shaped elements can be coupled and, once placed in the patient, obtain a cross-shaped structure that completely fixes the two vertebrae to stabilize. In this specific embodiment, the second rod-shaped element can pass through the first element and these will be coupled. In other embodiments it is not necessary for the second element to pass through the first and both elements could simply cross. If we want the rod-shaped elements to be coupled, we can provide these specific coupling elements.

• In other embodiments, this part two may have a joint (fig.

10, 11 and 12) in its central part that will allow the rod-shaped element to function as a mobile device, as a disc prosthesis and with advantageous properties as set forth in the background of the invention, in relation to the current disc prostheses. Figures 10, 11 and 12 show only the central part of the bar-shaped element, so to get an idea of the complete element it is necessary to replace in parts 4, 5, 6, 7 and 9, parts 4.2, 5.2 , 6.2,

7.2 and 9.2 by one of the possible embodiments, be it the form of Figure 10, 11 or 12. In the event that this part two of the device was provided with the articulated mechanism to allow certain movements, this part two would not be perforated longitudinally (as in figure 8), since in the central area of this part the dynamic device would be located. In the case of placing an element in the form of an articulated bar, we can choose different embodiments of the dynamic system.

The embodiment shown in Figure 10 shows a spherical joint that allows the movement of flexion-extension, lateral inclination and rotation. The operation will be that of a bolt and the limitation of movement may be given by the bolt clearance. The bolt (10.2.2) would have a spherical outer surface in contact with a bowl (10.2.3) with a spherical inner surface, which would allow the sliding of one over the other. The sliding surfaces between bolt and bowl (10.2.1) may be ceramic coated, including zirconia, to reduce friction.

Another embodiment of part two (fig. 11) allows movement in flexion-extension, lateral inclination, rotation and also has a spring mechanism (11.2.1) that can also be a crossbow that allows compression of 2 -4 mm in the direction of loading thanks to the internal device. The other movements are determined by the clearance between the outer bowl (11.2.2) and the internal pivot (11.2.4). The internal pivot (11.2.4) serves to keep the spring fixed within the mechanism and to allow maximum movement, since when the spring is compressed due to pressure forces, the internal pivot will collide against the external bowl preventing the spring from compress more. Figure 11.2.6 shows a cross section of this part 11.2, this cross section having been made in the place indicated by the dashed line, so that the cross section shows a section of the spring (11.2.1) and the internal pivot (11.2 .4). The figure also shows a pin (1 1.2.3) that is used to fix the position of the device at the time of insertion. When the rod-shaped element is introduced by a rotating movement around the axis, in the event that this internal pin did not exist, a part of the rod-shaped element would rotate while the other part would not rotate due to the element of the part central (11.2). For this reason it is necessary the existence of the internal pin (11.2.3) that prevents the rotation of one part over the other, allowing the rotation to be only a few degrees. In the cross-sectional cut (11.2.5) it can be best seen how the internal pin does not let the element rotate. This cross section (11.2.5) is made at the height of the internal pin as indicated by the dashed line. This pin can be an accessory screw threaded on one of the sides of the bowl, the rest of its surface being smooth.

In this embodiment we can replace the spring or the internal crossbow with an elastomer that will allow to absorb loads (fig. 12.2.1). This elastomer can also be observed in a cross-sectional cut (12.2.3). With this type of embodiment, all movements will also be preserved, compression loads will be absorbed and there will be lateral tilting movement in all directions. The lateral inclination should be limited to 2-3 ° in each direction so as not to exceed the physiological limits in all dynamic embodiments. The figure also shows an internal pin (12.2.2) that is used to fix the position of the device at the time of insertion. When the element in the form of bar is introduced by a rotating movement around the axis, in the event that this internal pin did not exist, a part of the bar-shaped element would rotate while the other part would not rotate due to the element of the central part (12.2). For this reason it is necessary the existence of the internal pin (12.2.2) that prevents the rotation of one part over the other, allowing the rotation to be only a few degrees. In the cross-sectional cut (11.2.4) it can be best seen how the internal pin does not let the element rotate.

The placement of a device capable of absorbing loads is very important, since it maintains part of the elasticity of the segment we are treating and eliminates stiffness. Rigid fixation systems can lead to long-term problems in vertebrae close to the set level since they will change the distribution of loads. If the system is not totally rigid, you don't have that problem. Part three (4.3, 5.3 and 8.3). This part, once the device is placed, will be housed in the body of the second vertebra (V2) that will be stabilized. This second vertebra is adjacent to the vertebra where once the operation is performed, part one of the device is in the form of a bar. Like part one of the device, this part two extends between two cortices.

In this case and like part one, part three may have a continuous (4.3.1 and 8.3.1) or discontinuous (5.3.1) threading on its outer surface. This part may have transverse perforations (4.3.2, 5.3.2 and 8.3.2). The function of these transverse perforations is to communicate the exterior with the central longitudinal perforation (4.3.5, 5.3.5 and 8.3.5) in the same way and with the same objective that has been exposed in the transversal perforations existing in part one Of the device.

This part may have its own characteristics and different from the characteristics of part one. These characteristics of part three can be:

1) The central internal duct can be threaded (4.3.4; 5.3.4 and 8.3.4). This thread serves to thread a rod inside. The rod will serve as a gripping element with the tool used to manipulate the rod-shaped element during its insertion, extraction and manipulation.

2) It also has a crenellated crown (4.3.3, 5.3.3 and 8.3.3) at the end used to be in contact with the handling tool. This end of the rod-shaped element may have any other shape (star, center groove, etc.) that facilitates the connection of the device with the used manipulation and introduction tools. The objective is to be able to attach a tool that can be used to manipulate the piece during the insertion of the device like a screw.

3) If the shape of the device is cylindrical, the last thread pitch, (the closest to the central part of the device), may be 0.5-1 mm more in diameter (5.3.6, 8.3.6) than the rest of the threaded to completely avoid the possibility of migration of the device in the direction of the free end of part one, that is to say to prevent the migration of the device inwards. This migration of the device is practically impossible in the general embodiment of the device in the form of a bar, so that if the last thread pitch is of a greater thickness, any possibility of migration of the device is eliminated. 4) Part three can carry on the free end a polymer cap, to prevent the formation of bone tissue on that end.

Part three may have a cone trunk shape, with a slightly larger diameter at the base corresponding to the grip area with the manipulation tool, that is to one end. The cone trunk shape of parts one and three is another way to prevent the migration of the device.

Embodiment example for movement insertion of

translation along the longitudinal axis (fig. 6, 7 and 9)

This embodiment example generally has a polygonal section although it can have any other section. The rod-shaped element is introduced in this case into the vertebrae and through the intervertebral disc by means of an axial displacement movement along the longitudinal axis or, what is the same, by means of an inward pressure movement. Therefore, instead of using a rotating movement, the device is pressed into the intervertebral segment.

The bar-shaped element described in this exemplary embodiment is a unique and continuous element, but for a better understanding of the device the bar-shaped element has been divided into three parts that can have different perforations and interior and exterior surfaces, as well As different functions.

The bar-shaped elements, which are introduced by displacement along the longitudinal axis and not by rotation around the longitudinal axis, consist of three distinct zones as in the embodiments of the previous section; part one, part two and part three.

Part one (6.1, 7.1 and 9.1): it can be shaped like a prism, cylinder or trunk of a pyramid or cone with a polygonal or circular base and with the diameter of the base of the free end that can be a little smaller than the diameter of the base from the end that continues with the rest of the bar-shaped element (part two). This part one will have a free end that will be housed inside the first vertebra (VI), while the other end will continue with part two, being also housed inside the vertebra.

On the outer surface it has ridges or projections (6.1.1, 7.1.1 and 9.1.1) that follow the direction of the longitudinal axis. These projections can be continuous (7.1.1) or discontinuous (6.1.1 and 9.1.1). Its purpose is to leave part one inside the vertebral body of the first vertebra (VI) in a fixed position. The longitudinal direction of the ridges or projections is necessary because the insertion of the rod-shaped element is done by displacement along the longitudinal axis of the device. The device will be inserted through the vertebrae and the disc following a conduit with grooves. The conduit will be made at the beginning of the intervention with a cylindrical drill whose diameter is equal to the outside diameter of the element without the ridges.

The grooves can be pre-carved with a chisel that has a section the same as the device section. Once the device is placed, part one will remain inside vertebra VI, part two will remain inside the intervertebral disc (Di) and part three it will remain inside the body of the second vertebra (V2), as can be seen in figures one and two.

Part one may have a central perforation, along the longitudinal axis, (6.1.5, 7.1.5 and 9.1.5) and transverse perforations (6.1.2, 7.1.2 and 9.1.2), which communicate the outer surface with central drilling These transverse perforations serve to allow the growth of bone through it or to allow the introduction of cement into the vertebra if necessary.

Part two: in the bar-shaped elements that are introduced by longitudinal displacement is similar to part two of the devices that are introduced by rotation or rotation movement. The description is similar since this part two can be manufactured in combination with any of the embodiments of the other two parts. Part three: the rod-shaped elements that are introduced by axial displacement or by pressure along the longitudinal axis, can be in the form of a prism, cylinder or pyramid or cone trunk, and may have the base of the end that comes into contact with the manipulation instrument of a section slightly larger than the other base, which is the one that continues with part two of the element. It has on its outer surface ridges or projections oriented along the longitudinal axis (6.3.1, 7.3.1 and 9.3.1). These ridges and projections allow the insertion of the device and stabilize part three with the V2 vertebra.

Part three may have a longitudinal central perforation (6.3.5, 7.3.5 and 9.3.5). This perforation can be threaded (6.3.4, 7.3.4, 9.3.4) to allow the grip with a similar thread that the handling tool could carry. You can also carry other types of irregularities other than threading to adapt it to the handling tool. On its outer surface it can have transversal perforations that communicate the exterior with the central perforation. The meaning of these perforations is similar to the perforations in part one.

Part three has two ends, one end is continued with part two and the other end is free. The free end has means of linking with the manipulation tool for the insertion of the device. This end can be smooth (6.3.3 and 7.3.3) or it can be crenellated (9.3.3) to achieve greater grip with the insertion tool.

In the event that the general shape is prismatic, in order to avoid a very unlikely migration of the device in the direction of the free end of part one, additional crests may be added along the last centimeter of the free end of part three Of the device.

Part three may carry at the free end a cover of polymeric material to cover this end. In this way, bone formation on that free end will be avoided and in the unlikely event that the element needs to be removed, this will be possible since the lid of polymeric material can be removed and the element can be removed using the manipulation tool .

Claims

Claim 1 Device for the treatment of pathologies in the spine characterized in that it comprises a continuous bar-shaped element, which extends along a longitudinal axis and consists of three distinct parts:

• A part called part one that has been designed to pass through the body of two vertebrae (VI and V2) and the intervertebral disc during the surgical procedure and be fixed in the vertebra (VI) when the surgical intervention is completed.

• A part called part two which is the continuation of part one along the longitudinal axis of the device, since the rod-shaped element is a continuous element, and which has been designed to pass through a vertebra (V2) and an intervertebral disc (Di) during the surgical procedure and be fixed in the intervertebral disc (Di) when the surgical intervention is completed. This part referred to as part two of the device will refer to the middle area in the longitudinal axis of the device in the form of a bar.

• A part called part three that is the continuation of part two or central part along the longitudinal axis of the device, since the rod-shaped element is a continuous element, and which has been designed to pass through the body of a vertebra ( V2) during the surgical procedure and remain fixed in the vertebra (V2) when the surgical intervention is completed. The vertebra (V2) will be contiguous with the vertebra VI from which it will be separated by the intervertebral disc (Di).

Claim 2

Device according to claim 1 characterized in that the part called part three of the device has linking means (4.3.3, 4.3.4, 5.3.3, 5.3 at the free end (end that does not continue in the part called part two of the device) .4, 6.3.4, 7.3.4, 8.3.3, 8.3.4 and 9.3.4) with a tool to allow the insertion and manipulation of the device in the form of a bar through the two vertebrae (VI and V2) and of the intervertebral disc (Di) by percutaneous surgery. The design of the device in the form of a bar and of the manipulation tools will allow percutaneous surgery to be carried out through a working channel using the posteroanterior and lateral X-ray projections as references. The means of linking with the insertion tool can be shaped by a crenellated crown, by a threading of the central perforation, by a star configuration, by a hexagonal configuration or by any other form they are usually used in screws.

Claim 3

Device according to claims 1 and 2 characterized in that the rod-shaped element contains in the part called part one of the device and in the part called part three of the device a threaded outer surface that can be a continuous thread (4.1.1, 4.3. 1, 8.1.1 and 8.3.1) or discontinuous (5.1.1 and 5.3.1) and which will be in contact with the bone tissue of the vertebrae (VI and V2) to facilitate the insertion of the device through the vertebrae during the surgical procedure by means of an axial rotation or rotation movement. Claim 4

Device according to claims 1 and 2, characterized in that the outer surface of the bar-shaped element in the part referred to as part one and in the part referred to as part three has projections or ridges in the longitudinal direction of the bar-shaped element (6.1 .1, 6.3.1, 7.1.1, 7.3.1, 9.1.1 and 9.3.1). This stretching, which can be continuous or discontinuous, will facilitate the implantation of the device by displacement along the longitudinal axis during the surgical procedure and will help stabilize the device within the vertebrae (VI and V2). Claim 5

Device according to claims 1, 2 and 3 or according to claims 1, 2 and 4, characterized in that it has a central perforation that follows the longitudinal axis of the rod-shaped element (4.3.5, 5.3.5, 6.1.5, 6.3 .5, 7.1.5, 7.3.5, 8.3.5) and which may extend to its full length, only to the parts designated as part one and part three of the device or only a part of the device in the form of a bar.

Claim 6 Device according to claims 1 and 2 and according to any of the other preceding claims, characterized in that it has transverse perforations along the surface (4.1.2, 4.3.2, 5.1.2, 5.3.2, 6.1.2, 6.3.2, 8.1.2, 8.3.2, 9.1.2, 9.3.2). These transverse perforations, in the event that the rod-shaped element also has a central perforation, communicate the outer surface with the longitudinal central perforation. The purpose of these perforations is that, when the bone tissue begins to grow after the operation, they allow the passage of this bone tissue from the vertebra through those perforations and connect it with tissue that will grow in the central perforation so that the element in the form of a bar it is completely stable. The perforations may extend over all or part of the surface of parts one and three of the rod-shaped device.

Claim 7

Device according to claims 1 and 2 and according to any of the other claims 3-6, characterized in that the part referred to as part two of the rod-shaped device is solid and lacks holes in the outer surface (4.2, 5.2, 6.2 and 9.2 ). This part called part two of the device is intended to be in contact with the intervertebral disc and therefore a solid structure without holes in the surface will facilitate the grip. The section of the bar-shaped device in this part two can be circular or have any polygonal shape. Claim 8

Device according to claims 1, 2 and according to any of claims 3-7, characterized in that the part referred to as part two of the rod-shaped device has a transverse through hole (8.2.1). This perforation will allow the passage through a second bar-shaped element of smaller section. The rest of the part called part two of the rod-shaped element is solid and lacks the central longitudinal perforation.

Claim 9

Device according to claims 1 and 2 and according to any of claims 3-6, characterized by having the articulated part two (figures 10, 11 and 12), with a device that can allow movement in the three axes of space. The internal device may be provided with a spring mechanism (figure 11), crossbow or have an elastomer (figure 12) capable of damping the loads and allowing limited tilt movement to either side. The internal device may be provided with a bolt mechanism (figure 10) allowing the movement of inclination to any side.

Claim 10

Device according to claims 1 and 2 and according to any of claims 3-9, characterized in that the rod-shaped element has a geometric shape similar to a cone trunk or a pyramid trunk, therefore having two bases with diameters slightly different; a slightly larger base located at the end of the part called part three of the bar-shaped element and a slightly smaller base located at the end of the part called as part one of the bar-shaped element. At the end located in the part referred to as part three is where there are means of linking with the insertion and manipulation tool. The section in the parts referred to as part one, two and three may be circular, polygonal or have any other form of a closed curve. Claim 11

Device according to claims 1 and 2 and according to any of claims 3-9, characterized in that the rod-shaped device is shaped like a cylinder or prismatic shape.

Claim 12

Device according to claims 1, 2 and 11 characterized in that the free end of the part referred to as part three of the bar-shaped device has an area in which the diameter of the section is greater than the diameter of the section of the rest of the device in the form of a bar (5.3.6 and 8.3.6). The part called part three of the device in the form of a bar will be that which has one of the ends of the means of linking with the insertion and manipulation tool and which is also the last part to be introduced in the patient's body during surgical procedure.

Claim 13

Device according to claims 1, 2, 5 and any of claims 3, 4, 6-12, characterized in that the hollow or central perforation that extends totally or partially along its length is threaded (4.3.4, 5.3.4 , 6.3.4, 7.3.4, 8.3.4 and 9.3.4).

Claim 14

Device according to any of the preceding claims characterized in that the means of linking between the rod-shaped element and the tool that allows the insertion and manipulation of the element through the vertebrae (VI and V2) by percutaneous surgery comprises a double system formed by an external crenellated crown (4.3.3, 5.3.3 and 8.3.3) and an internal thread that allows the introduction / removal tool to be held with the rod-shaped element (4.3.4, 5.3.4 and 8.3.4) .

Claim 15

Device according to any of claims 1-14 for use in the treatment of a pathology of the spine.

Claim 16

Device according to claim 15 wherein the pathology is an instability between two vertebrae of the spine or an alteration of the intervertebral disc, these pathologies being of congenital, traumatic, degenerative, infectious or tumor origin.

Claim 17

Use of a device according to any of claims 1 to 14 for the preparation of a medicament for the treatment of a pathology in the spine.

Claim 18

Use according to claim 17 wherein the pathology is an instability between two or more vertebrae of the spine or an alteration of the intervertebral disc, these pathologies being of congenital, traumatic, degenerative, infectious or tumor origin.

Claim 19

Method for treating a pathology of the spine in a patient, comprising the implantation of a device according to claims 1 to 14.