"DEVICE FOR IMPLANTING A SURGICAL SCREW"

The present invention relates to a device for implanting a surgical screw. In the state of the art a variety of systems and techniques are known to intervene on specific problems of the spine, such as abnormal curvature of the spine, injuries to the same, etc.

The intervention on these types of spine-specific problems frequently requires the stabilization of a portion of the spine portion so as to facilitate the fusion of two or more vertebrae together in a single bone agglomeration.

This type of intervention is frequently employed for the correction of many pathological conditions of the spine such as, for example, degenerative diseases of the discal elements, scoliosis, spinal stenosis, or the like.

Not infrequently, these corrective measures require the use of implants, such as, for example, bone grafts. The stabilization of the spine allows the creation of a bone tissue in the intervertebral part; in this way a part of the spine is fused into a single bone body.

The stabilization of the spine has been studied for a long time in the past and a variety of methods and devices have been developed for the correction of many pathologies that affect characteristically this body part in order to stabilize the its configuration, facilitating the vertebral fusion at various levels.

One of these known systems provides that a bar is arranged longitudinally along the portion of the spine which needs the intervention. This bar is shaped in such a way as to represent the correct anatomical shape which is characteristic of that specific portion of a healthy spine.

With this method, therefore, the bar is positioned along the spine to engage various vertebrae, as needed. It should be noted that, typically, in this type of surgery two parallel bars are used that are arranged at the sides of the central area of the spine. Therefore, during said surgery, the pair of bars is fixed to the spine by means of various fixing means, including, for example, screws. These screws are attached to the bone structure, typically to the vertebral pedicle.

The inclination of the bar and, consequently, the positioning of the fixing screws varies depending on the type of correction to be done and, of course, from vertebra to vertebra. It seems clear that it is essential for a successful surgery to properly fix both the corrective bar and the screws to which the bar will be fixed.

In order to obtain a correct positioning of said elements, according to the needs of the patient, polyaxial screws are utilized.

The implant of said polyaxial screws, bars and any necessary fixing means, requires typically somewhat invasive interventions resulting in injuries to the skin and muscle tissues of the patient. This surgery usually requires rather long hospitalization and rehabilitation times.

In order to reduce the invasiveness of the surgery, the operative technique was directed toward minimally invasive techniques able to significantly reduce the trauma to the tissues, with benefits for the patient including, for example, shorter hospitalization times, lower postoperative pain, less rehabilitation, and with benefits for the the hospitals, including shorter hospitalization times, fewer costs, and fewer resources for the rehabilitation. To address the needs of this type of minimally invasive interventions, instruments capable of allowing the surgeon to secure said polyaxial screws in the desired position have been developed, also through an incision of limited size on the patient's body, along with the possibility of implanting said bars in the desired position through said instruments.

An example of this type of surgery instruments is illustrated in the U.S. patent application No. US2013/0144349 by Lanx Inc., Broomfield, CO (USA).

From this document it is known a instrument to facilitate minimally invasive surgery procedures, the instrument comprises: an outer sleeve, in turn comprising a first and a second elongated sleeve, each having a distal end and a proximal end, the inner sleeve having a first and a second channel extending between the first and the second elongated sleeve, starting from the distal end; said first and said second channel having a length greater than the half of the total length of the first and second elongated sleeve. The outer sleeve includes a third and fourth elongated sleeve, each having a proximal and a distal end, said outer sleeve also comprises a third and a fourth channel extending between the third and the fourth elongated sleeve, starting from the distal end. The third and fourth channel each have a length greater than the half of the length of the third and fourth elongated sleeve. In that instrument the inner sleeve is dimensioned in such a way as to be housed inside the outer sleeve. Said instrument comprises a connecting element adapted to couple the two proximal ends of the first and second elongated sleeve with the proximal ends of the third and fourth elongated sleeve. It is also provided an alignment element to align the first channel with the third channel and the second channel with the fourth channel, when the inner sleeve is housed inside the outer sleeve. Additionally, the device has coupling means with an implant, these being adapted to secure the first and the second sleeve to the implant in a demountable manner.

However, the prior art suffers from a number of drawbacks.

As known in the art, in fact, the polyaxial screw is first sidely engaged by the outer sleeve and only thereafter by the inner sleeve. This asynchrony just described results in a lack of stability of the connections between the device known in the art and the polyaxial screw, with consequent problems during the phases of surgery.

In addition, the length of the channels present in the device as fond in US2013/0144349 makes said device poorly resistant to the bending stresses. In fact, if said device is in the closed configuration and is coupled with a polyaxial screw, for example during minimally invasive surgery, it is possible that the user, for example the surgeon engaged in said surgery procedure, may inadvertently apply a bending stress by simply tilting the distal part of the device with respect to its central axis. In this case, the proximal part of the internal and external sleeves, both of which are integral with the polyaxial screw, undergoes a bending resulting in a risk that the proximal part of the outer sleeve will decouple from the proximal part of the inner sleeve of the device, thus leading to the accidental opening of the known device and to the decoupling of the same from the polyaxial screw. This accidental decoupling can, in certain cases, leads to the undesired injury of the patient and the incorrect positioning of the surgical screw, with also relevant consequences for the success of the procedure.

A further drawback of the known state of the art is the laboriousness needed to put in place the devices known in the art.

Having in mind these drawbacks, the present invention intends to solve them.

An object of this invention is to provide a device for implanting a surgical screw that is capable of couple with said screw in a simple and quick way. Another object of the present invention is to provide a device for implanting a surgical screw that is able to withstand the bending, torsion and traction stresses, without being disunited or decouple from the surgical screw.

Further object of this invention is to provide a device as specified which is easy to use, fast to use, robust, and that has a low cost.

In view of these objects, the present invention provides a device for implanting a surgical screw, whose feature is the subject matter of claim 1 . Further advantageous features are described in the dependent claims. All claims are considered as fully described.

The present invention will be more apparent from the detailed description which follows, with reference to the accompanying drawings provided solely by way of example, in which: Figure 1 is an elevational side front view of the device for implanting a surgical screw in the closed configuration with an assembled polyaxial screw of the present invention;

Figure 1 bis is a side front elevational view of the device for implanting a surgical screw in the open configuration with an assembled polyaxial screw of the present invention;

Figure 2 is an side front elevational view of the device for implanting a surgical screw in the disassembled configuration;

Figures 3, 3 bis and 4 are partial side front elevational views of the present invention in the open configuration;

Figure 5 is a partial view of the present invention in combination with polyaxial screw in the open configuration shown as a partial section;

Figures 6 and 7 are partial views of the present invention in combination with a polyaxial screw in the closed configuration;

Figure 7 A is a sectional view along the line A-A shown in Figure 7;

Figure 8 is a partial side elevational view of the present invention in the open configuration;

Figure 8A is a cross-sectional view taken along the line B-B in Figure 8; With reference to the figures listed above, with 100 is indicated the device for implanting a surgical screw, object of the present invention, as a whole. Figure 1 is an overall view of the device 100 for implanting a surgical screw in the closed configuration. It has a substantially cylindrical shape with vertical axis, a hollow interior, having a greater dimension extending in the axial direction. Again in the axial direction it is possible to identify two end parts: a first end part 101 , said proximal part, has a substantially circular hollow section with a open bottom sleeve and communicating with the internal cavity of the device body 100, and is adapted, by coupling means, to be coupled to a surgical screw, for example, a polyaxial screw 2, while a second end part 102, said distal part, has a circular hollow section with an open top 1 10, is configured for a comfortable grip by the user and has, in a part thereof, a command, for example a button 420. Along substantial part of the device 100 for implanting a surgical screw 2, there are two channels 104 (Fig. 1 ) and 105 (Fig. 6) passing through and extending from the proximal end 101 for a substantial part of the axial dimension of said device 100.

In Figure 2 is shown an exploded view of the device 100 for implanting a surgical screw 2 disassembled into its main parts. It includes an outer sleeve 3, having a substantially cylindrical shape, with a hollow interior, having a hollow outer central body 303 and two end parts, in turn with a hollow interior, and integrally connected to it: a first part of the outer end 301 , said proximal outer, which has a substantially circular section and and the open bottom, in communication with the internal cavity of the outer central body 303 and an outer distal part 302, said outer distal part 302 having circular hollow section and the open top, in communication with the internal cavity of the outer central body 303. With reference to Figure 3 it is possible to identify two windows 306 and 307 located in part in the part of outer distal end 302 (hereinafter outer distal part) and in part in the upper part of the outer central body 303. Again with reference to said Figure 3, starting from the first part of outer proximal end 301 (hereinafter outer proximal part), there are two passing through external channels 304 and 305, which extend throughout the length of the outer proximal part 301 and for substantial part of the outer central body 303, in axial opposition to each other. Additionally, the outer proximal part 301 has, in its terminal part, a coupling edge 308. Said coupling edge 308 of the outer proximal part 301 has provided with retaining elements, for example two pairs of passing through, axial channels 308.1 and 308.2, 308.3 and 308.4 (fig. 2 and the subsequent figures), arranged along the circumference of the coupling edge 308. The first pair of channels 308.1 and 30.2 is divided from the second pair of channels 308.3 and 308.4 by the two external channels 304 and 305, which, as mentioned, branch off from the coupling edge 308 dividing it into two equal circular rings on which lie the two said pairs of channels 308.1 and 308.2, 308.3 and 308.4. Again with reference to Figure 2, the device 100 for implanting a surgical screw 2 also comprises an inner sleeve 4 having a cylindrical shape, a vertical axis and an axial cavity, extending in the axial direction and having axial dimensions greater than the outer sleeve 3 and a lower diameter of said outer sleeve 3; said dimensions being such as to allow the outer sleeve 3 to accommodate, in its axial cavity, a substantial part of the inner sleeve 4. Said inner sleeve 4 essentially comprises: an inner central body 403, having a substantially cylindrical shape, a hollow interior and shaped so as to be received in the axial cavity of the outer sleeve 3 and to be mated with the structural features. To said inner central body 403 are integrally connected two end parts with a hollow interior: a first inner proximal end part 401 , said inner proximal part, and an inner distal end part 402, said inner distal part, being said inner proximal and inner distal part 401 and 402 integrally connected to the inner central body 403 so that the respective hollow interiors are in communication to each other.

The central body 403 has two internal inner channels 404 and 405 passing through and extending axially for a substantial part of the inner central body 403 and for the total inner proximal part 401 . Said two inner channels 404 and 405, mutually axially positioned, have position and shape such as to overlap with the above external channels 304 and 305 on the outer sleeve 3 so that, when the device 100 is in the assembled configuration, the overlap of the outer channel 304 with the inner channel 404 and the overlap of the outer channel 305 with the inner channel 405 are in the channels 104 and 105 of Figures 1 and 6.

The inner proximal part 401 is divided into two end portions 41 1 and 421 from said two inner channels 404 and 405. Said two end portions 41 1 and 421 , as can be seen in the attached drawing, have the same structural and functional characteristics, and therefore only one (41 1 ) of the two (41 1 , 421 ) portions will be described. The first end portion 41 1 has, on its outer surface, a lateral engagement device 412 and two stop elements, for example a pair of outer side coupling pins 413 and 414 projecting from an outer surface of the substantially mushroom-shaped inner proximal part 401 . Said two pairs of outer side pins 413, 414 and 415, 416 perform both a stop function during the sliding of the outer sleeve along the inner sleeve, during the transition from the closed configuration to the open configuration, and a retaining function when the device is in the closed configuration with respect to any bending stresses that could misalign the outer sleeve 3 with respect to the inner sleeve 4, resulting in the accidental and unintended opening of the device 100, thereby causing the loss of grip of said device 100 on the polyaxial screw 2. The lateral engagement device 412 is formed from the inner proximal part 401 by, for example, cutting and bending towards the outside of a part of the outer surface of the portion 41 1 . Said lateral engagement device 412 is configured in the peninsula as respect to the end portion 41 1 and is integrally connected to it by means of its upper side only 412.3, while for the remaining three sides it protrudes from said end portion 41 1 radially and for a substantial part of its length. Due to the shape just described, the lateral engagement device 412 is able to move between a free configuration (Fig. 2), in which said lateral engagement device 412 protrudes radially from the inner proximal part 401 , and a engagement configuration (Fig. 6 ), wherein said lateral engagement device 412 is aligned with the outer surface of the inner proximal part 401 .

At the sides of the lateral engagement device 412 is located the pair of outer side coupling pins 413 and 414, one for each side of the said lateral engagement device 412, also projecting from the outer surface of the inner proximal part 401 .

On the inner face of the lateral engagement device 412 facing towards the axial cavity of the inner sleeve 4, coupling elements are provided, for example two radial pins 412.1 and 412.2, integral with respect to said lateral engagement device 412 and projecting towards the axial cavity of the inner sleeve 4. These two inner radial pins 412.1 and 412.2 are located at the side of the lateral engagement device 412 distal to the upper side 412.3 of said lateral engagement device 412.

As can be appreciated from Figures 5 and 7, in the inner portion of the inner sleeve 4, there are the axial engagement elements, for example two pairs of axial pins 417.1 , 417.2 and 417.3, 417.4. Said pairs of inner axial pins 417.1 , 417.2 and 417.3, 417.4 have an axis normal to the central axis of the inner sleeve 4 and extend longitudinally in the axial direction.

Close to the entrance of the two end portions 41 1 and 421 (Fig. 4), on each of them there is an alignment element, for example a respective alignment protrusion 418. Said alignment protrusion 418 is shaped so as to be received in a respective cavity 218 made in the head part 200 of the polyaxial screw 2. When, during the coupling between the polyaxial screw 2 and the present invention 100, said polyaxial screw 2 is received within the proximal part 401 of the inner sleeve 4, said pair of alignment protrusions 418 (one for each end portion 41 1 and 421 ), fitting down in the respective cavity 218, ensures the proper alignment between the inner sleeve 4 and said polyaxial screw 2.

The outer distal part 402 has, in its part adjacent to the inner central body 403, a passing through opening 406, which overlooks the inner axial cavity. Jutting cantilevered on said window 406 is a button 420 supported by a bridge 431 which branches off from the inner central body 403 and overlooking the window 406. Said button 420 is elastically movable between a neutral position, coplanar to the outer surface of the inner central body 403, and a retracted position, in which the said button 420 engages the central axial cavity of the inner sleeve 4.

In the opened assembled configuration, as can be seen in Fig. 1 bis, the device 100 for implanting a surgical screw 2 has the outer sleeve 3 fitted on the inner sleeve 4; the inner proximal part 401 of the inner sleeve 4 comes out, for almost all of its length, from the outer proximal part 301 of the outer sleeve 3. Moreover, the lateral engagement devices 412 and 422 are in the free configuration, i.e. both projecting from the outer surface of the inner proximal part 401 ; the button 420 occupies the window 306 while the window 307 is empty.

Operation

When the device 100 for implanting a surgical screw 2 is in the open configuration of Fig. 1 bis, the operation provides the insertion of the polyaxial screw 2 within the portion of the axial cavity included in the inner proximal part 401 . The polyaxial screw 2 is known in the art and is described herein only in the substantial aspects in order to better illustrate the operation of the device 100 subject matter of the present invention. Said polyaxial screw 2 comprises essentially a head part 200 and a threaded shank 230. At the top 201 of the head part 200 of the polyaxial screw 2 (Fig. 3), there are two pairs of axial channels 217.1 , 217.2 and 217.3, 217.4. Also, in the head part 200, sidely with respect to the axis of the threaded shank 230 of said polyaxial screw 2 (Figs. 2, 3, 4), there are the coupling parts, for example two pairs of side channels 212.1 , 212.2 and 212.3, 212.4. When the polyaxial screw 2 is coupled with the device 100 for implanting a surgical screw 2, the head part 200 of said polyaxial screw 2 is, as mentioned, partially received within the proximal internal part 401 of the inner sleeve 4, thus allowing two pairs of inner axial pins 417.1 , 417.2 and 417.3, 417.4 to engage the two pairs of axial channels 217.1 , 217.2 and 217.3, 217.4, respectively. This coupling makes the polyaxial screw 2 and the device 100 for implanting a surgical screw integral with respect to a possible rotation along the central axis of the device 100 itself.

Then, by pressing the button 420 in the direction normal to the central axis of said device 100, said button 420 moves inward to engage the axial cavity of the inner sleeve 4 freeing the window 306. This translational movement of the button 420 towards the inside of the device 100 allows the user to slide the outer sleeve 3 axially along the inner sleeve 4 in the direction of the polyaxial screw 2. Through this sliding, the button 420, shifted towards the inside of the device 100, passes under the divider section 310 to engage the window 307 once the sliding is complete. During said sliding of the outer sleeve 3 with respect to the inner sleeve 4 in the direction of the polyaxial screw 2, the outer proximal part 301 descends along the inner proximal part 401 until the two pairs of outer side coupling pins 413, 414 and 415, 416 not engage the channels 308.3, 308.4 and 308.1 , 308.2, as shown in Fig. 6, respectively.

As can be appreciated from Figures 5 and 6, the lateral engagement devices 412 and 422, precisely because of the action exerted by the outer proximal part 301 on them, vary their position from a projecting position with respect to the outer surface of said inner proximal part 401 (Fig. 5) to a longitudinally aligned position with respect to said outer surface of the inner proximal part 401 . In this way, the two pairs of inner radial pins 412.1 , 412.2 and 412.3, 412.4 engage the two pairs of side channels 212.1 , 212.2 and 212.3, 212.4. In this way, the polyaxial screw 2 becomes integral with respect to the device 100 for implanting a surgical screw 2, reaching the closed configuration of said device 100 for implanting a surgical screw 2.

In this configuration, reached at a complete sliding of the outer sleeve 3 on the inner sleeve 4, the button 420 regains neutral position engaging the window 307, thus blocking the device 100 of the present invention in the closed configuration and being coupled to the polyaxial screw 2.

When the top 1 10 at the distal end part 102 is open, it is possible to access the internal cavity of the device 100 until reaching the polyaxial screw 2. In this way one can act on it in order to secure it in a suitable location or to perform necessary procedures during an implantation.

Furthermore, the channels 104 and 105 (FIGS. 1 and 6), made by the overlapping of the pairs of through outer 304, 305 and inner channels 404, 405, respectively, are available for the insertion of a bar (not shown) adapted to be secured to the head of the polyaxial screw 2 according to a technology known in the art and not further illustrated. After completing the necessary procedures for implanting the polyaxial screw 2, by pressing the button 420 and by moving it from its neutral position, one can slide the outer sleeve 3 along the inner sleeve 4 bringing the device 100 in the open configuration and freeing so the polyaxial screw 2 just implanted.

As is immediately appreciated by those skilled in the art, the present invention advantageously achieves the objectives listed above by solving the drawbacks of the known state of the art.

Of course, numerous variations may be made in practice with respect to those described and illustrated by way of non-limiting example, without thereby departing from the scope of the present invention and, therefore, from the domain of the present industrial property right.