WO2010070154A1

WO2010070154A1 - Locking device in screw-retained plates for medical use

Info

Publication number: WO2010070154A1
Application number: PCT/ES2008/070234
Authority: WO
Inventors: Germán PÉREZ COSÍAS
Original assignee: Surgival Co., S.A.
Priority date: 2008-12-18
Filing date: 2008-12-18
Publication date: 2010-06-24

Abstract

It uses a lock washer (5) preferably inserted into a slot (6) arranged in a receiving hole (2) of a screw (3) in a plate (1), the lock washer (5) having an internal diameter less than the maximum diameter of a head (4) of the screw (3); such that the lock washer (5) allows the head (4) of the screw (3) to pass through it when the plate (1) is bent transversally. The receiving hole (2) of the plate (1) has a spherical support (7) able to receive a spherical support surface (8) formed by the underside of the head (4) of the screw (3); such that it enables a certain inclination of the screw (3) in respect of the direction transversal to the plate (1). The head (4) of the screw (3) has an upper convex surface (9). Advantageously, the screw (3) has an Allen seat (10) used to insert it, and a threaded locking hole (11) that facilitates its extraction against the stress generated by the lock washer (5).

Description

DMΌSΠIVO DEEK) QIM) IN HACIAS ATOEÍVIIIADASDEIEO MEDICO

The present invention relates to a paia device preventing the accidental release of bone fixation thymes in medical plates, especially, but not exclusively, in anterior vertebral plates intended for spinal stabilization of the spine, provided as an ideal complement for perform a vertebral fusion (arthro of sis) by bone graft or intersomatic cage. These systems are essentially composed of plates and thymes to align and maintain vertebrae in the desired position with respect to each other. At least two adjacent vertebral bodies are stabilized, but configurations can be found to be fixed over several vertebral levels (the range of usual cervical plates stabilize from two to five vertebral bodies). Once the vertebral artery has been achieved over time, the plaque is usually serrated.

In the context of this document, "washer" means a body, generally flat, provided with an opening, and by its "internal diameter" the measurement of the circle inscribed in said opening.

Background of the invention

In the known systems the plates have presented problems of loosening due to the elements used, breakage of the thymes and the plates, and passage of the thymes to the area of the patient's throat. These incidents generally require other surgical interventions to replace the broken parts of plates and thymes, and repair any damage that may have been caused.

Other problems presented are the result of the loosening of the thymes due to the insufficient introduction into the bone, insufficient length of the bone, threaded over inadequate vertebral areas of low trabecular cohesion, etc., causing all this casuistry the disappearance of the filleting in the bone, with the consequent risk of migration of the tumor.

To fight against this problem, a large number of second generation devices have been developed (the first generation consists of basic plate / thyme solutions) with thyme retention systems of greater or lesser effectiveness, which usually lead to certain problems annexed to these problems.

The most notable problem created by these second generation devices is given by the small "watchmaking" parts used to house the bone fixing screws of the plates (extremely small parts or mechanisms, of high precision and high level of demand as far as to manufacturing tolerances and production repeatability), since frequent losses of said parts occur, either during praxis (being able to get lost in the operating room or worse, falling into the surgical field even accidentally and not perceived by the surgeon) or after surgery.

In addition, these small pieces are very fragile and require special tools for handling and insertion. It is also known that improper placement of a thyme in the bone with respect to the hole of the plate can make the thyme locking mechanism impracticable, or it may cause the formation of sharp metal chips when the locking thyme is introduced against a thyme of bone that has been improperly attached. On the other hand, the tendency to manufacture cervical plates of "low profile" (thicknesses less than 3 mm) is being imposed on the market, which explains why these "watchmaking parts", since in these few In millimeters, the blocking solution must be contained, trying to maintain functionality and, above all, the mechanical resistance of the assembly. Porello, finding a novel solution within this "Low Profile Plate" environment, departing from what is currently known, and where the technological requirement for its manufacture is not so high, is an exercise that is not without difficulty.

Eh p articular, the different s dispos sive sde b what or known in prior art can be classified into three main sections: a) With thyme retention system contained in the plate b) With retention system contained in the own thyme c) System block it by interaction of elements contained in both the plate and the thyme.

With respect to the first group, systems based on screw caps that cover the bone thymes are very frequent, preventing their exit, as is the case in EB 2253809, US 6,306,136, US 2005177161, WO 00126567, ES 2228616 or WO 9801653ER Efete type of "screw cap" solutions really aggravates the existing problem, because if the screw plug is lost (much smaller than the bone thyme), it will be free in the middle and in turn will not prevent the exit of the thymes bone, in case they become loose. In addition, this locking system represents an additional step to screwing the bone thymes themselves, adding complication to the surgical technique, since elements of a tiny size must be handled, thus increasing the possibility of their loss in the middle along with the risk added a bad move. Other solutions of the first group, in which the plates contain the retention system, are based on longitudinally sliding elements (ES 2216500T3) or rotating elements (US 2008021470) that cover the heads of the bone thymes once installed. Efete type of solutions are of a difficult industrialization, since both the machining of these elements and that of their housings in the plates, require exquisite precision. In addition, there are cases in which the bone thyme must be introduced with a certain inclination, which can cause its head to interfere with the sliding retaining element. Finally, as in the previous case, this blockage requires a final additional step within the surgical technique. With respect to the devices corresponding to the second group, in which the system of rete nc io ne this content in the own thyme, these are solutions that use expander or retainer elements that are introduced in a subsequent step the placement of the thyme, as described in US 200102220, EP 1285632 or ES 1050573 U. It goes without saying that the retention pieces are of tiny size, difficult to manipulate and great fragility that, once loosened, are part of the problem, getting lost in the middle and allowing the thyme to exit osseous. In addition, the bone thyme is very weakened by having to hold the retention pieces inside, so it can be cut. easily by plate when compressed. Also within this second group can be seen the tapping systems of the thyme in which the head of the thyme has protuberances that grip the support surface of the plate at the end of its introduction. Its effectiveness is doubtful. Finally, the third group is constituted by mechanisms contained in the plate that interact with specific elements of the thyme. These types of mechanisms, which "catch" the thyme, demand such precision that they can fail due to the simple operation of bending the plate to correct its curvature, so that its main problem is the lack of security. Accordingly, it is an objective of the present invention to have a locking device incorporated into the plate prior to surgery, and to act automatically.

Another objective of the present invention is to have a locking device specially adapted to perfquence plates. Another objective of the present invention is to dispose of a device of which what is required, which is not guaranteed.

Another objective of the present invention is to have a blocking device that is not affected by the inclination of the bone thymes.

And, finally, it is another objective of the present invention to have a locking device insensitive to plate deformations.

Description of the invention

To achieve the proposed objective, a locking device is designed that is based on the bending of a washer, transverse to the plate, during its passage through the head of the bone thyme.

More specifically, in one embodiment, the plate has, in the receiving hole of the thyme, a slot in which a flexible washer is inserted. Efeta washer has an inner diameter slightly smaller than the maximum diameter of the bone bone head, which allows the washer to flex during the introduction of the bone, whose accidental rear exit is thus prevented.

The bone thyme is equipped with a tool housing, advantageously of the ALLEN type, which allows its introduction and extraction later, if desired. Since the extraction effort can be considerable, the thyme can also have a threaded extraction hole against the rose, which facilitates the operation.

To allow the inclined introduction of the thymes while maintaining the blocking capacity of the device of the invention, the receiving hole of the thyme in the plate has a spherical support with which a supporting surface, also spherical, of the thyme head cooperates. Since the top surface of the head of the screw must be convex to ensure its retention by the lock washer at any inclination, the head of the thyme finally has a bevelled appearance, with a maximum diameter at half height clearly located below the lock washer.

The realization of the lock washer can be carried out in multiple alternative ways. Thus, it can have a simple circular crown shape, adjusting its flexibility by choosing the interference between its inner diameter and the maximum diameter of the head of the spindle, the material, and the thickness of the circular crown. You can also incorporate a cut, radíalo no, that will facilitate the insertion of the lock washer in the slot provided on the plate. When performing the radial cut, it may be necessary to remove material, so that its angular disengagement reaches 360 ^s . This facilitates its introduction, since otherwise the sides of the cut are mounted one on top of the other due to the angle of angular development by reducing its diameter so that it can be inserted into the groove. Obviously this precaution is not necessary if you are inclined. The realization of the lock washer as a circular crown crenelled internally in the same plane, allows to reduce the introduction effort without excessively reducing the thickness, facilitating the achievement of an elastic and non-plastic deformation. In any case, the outer diameter of the lock washer adjusts to that of the groove of the plate, even in the cut executions, so that, during the passage through the head of the thyme, the deformation occurs essentially from Transverse form the plate.

The guarantee of grip on the bone of the bone, caused by the possibility of introduction with a certain inclination, is enhanced by the use of a high thread depth along its entire length, and because the diameter of the delto millo nucleus is increasing from the tip to the head, which allows a lateral bone compaction and results in a safer and more resistant fixation to the start, reducing the risk of thread pasting of the firing in 1 hole. The advantages of the locking device of the invention are numerous:

• The locking element is incorporated into the plate during its manufacture. The blockage occurs automatically during the introduction of the thyme, so no additional operation is necessary during the surgical procedure. • There are no moving elements to handle, nor can they get lost in the middle.

• The locking device of the invention has a low height, which together with the bevelled head delto millo allows the market to offer a very low profile plate • The device operates by elastic flexion. The chances of failure are minimal.

• It is ro b usto and e c o nó mic o.

• The device allows the inclined introduction of the thyme, which greatly facilitates its use. • The device is not sensitive to plate deformations.

Revé description of the drawings

To complement the above description, and in order to help a better omprehension of the features of the invention, a detailed description of a preferred embodiment will be carried out, based on a set of drawings that accompanies this specification by going nde, with orientation and not limitation, the following has been represented:

Figure 1 shows a perspective view of the locking device of the invention, corresponding to a cervical plate covering two vertebrae. Figure 2 shows an elevational view of the plate with only two screws inserted, one of them inclined.

Figure 3 shows a section of the plate through the receiving hole of the thyme Figure 4 shows an elevation view of the delto millo.

Figure 5 shows a mule diametraldelto section

Figure 6 shows a plan view of the lock washer in its execution of a circular battlement ring inside in the same plane. Figure 7 shows an elevation view of the lock washer of Figure 6.

Figure 8a shows a plan view of the lock washer in its radially short circular crown execution.

Figure 8b shows a plan view of the lock washer in its circular crown execution with an inclined cut.

Figure 9 shows an elevation view of the lock washer of Figure 8a.

Figure 10 shows a sectional detail of the thyme head locked in its housing. Figure 11 shows a sectional detail of the locked head of an inclined thyme.

Figure 12 shows a sectional detail of the blocked head of a defectively inserted thyme.

In the previous figures, the numerical references correspond to the following parts and elements:

1. Plate

2. Reception holes

3. Thyme

4. Head 5. Lock washer

6. Slot

7. Spherical support

8. Spherical support surface

9. Convex upper surface 10. ALIEN accommodation

11. Threaded threaded hole

12. Inspection window Detailed description of a preferred embodiment

Eh Figures 1 and 2 show an embodiment of the device of the invention consisting of a cervical plate for stabilization of two vertebrae. It will easily be understood that the design can be extrapolated without further increasing the length of the plate and the number of holes.

As can be seen in the figures, it is a low profile plate (1), provided with receiving holes (2) of thymes (3) intended to be introduced into the vertebrae (not shown). Two of the receiving holes (2) are shown with the heads (4) of the thymes (3) retained by lock washers (5), while the other two have not shown the thymes or the lock washers, in order to power the grooves (6) in which they are inserted. In this case, they are lock washers (5) in their execution as a circular crown crenelled internally in the same plane, as shown in Figures 6 and 7. In Figure 3, groove improvement (6) can be seen, circular, executed in the receiving hole (2) of the plate (1), as well as the spherical support (7) for the head (4) of 1 mm (3).

The thyme (3) has a nucleus of increasing diameter from the tip to the head (4). This, of low height, is delimited inferiorly by a spherical support surface (8) intended to collaborate with the spherical support (7) of the receiving hole (2) of the plate (1), and poruna convex upper surface

(9) intended to interfere with the lock washer (5). Ui ATTFN hosting

(10) allows the introduction of the thyme (3) into the bone, and a threaded hole with counter-thread (11) facilitates its extraction against the effort of the lock washer (5). See figures 4 and 5.

With respect to the lock washer (5), in figures 6 and 7 the execution can be seen as a circular crown crenelled internally in the same plane, while figures 8a and 9 show the execution as a radially cut circular crown, having been represented by strokes in this last figure the elastic deformation of the cut that will allow its easy insertion in the groove (6) of the receiving hole (2) of the plate (1). Note that in the oblique cutting washer of Figure 8b it is not necessary to remove cutting material, which is necessary in the radial cutting washer of Figure 8a. In the case of crenellated washer of figure 6, the reduction of the circular crown width in a certain point increases its radius flexibility and facilitates its introduction.

Figures 10 to 12 illustrate the operation of the locking device of the invention. Thus, Figure 10 shows a thyme (3) resting on the spherical support (7) of the receiving hole (2) of the plate (1). Note that, when the thyme (3) is centered, the interference "e" with the lock washer (5) is symmetrical on each side. Due to the bevelled appearance of the head (4) of the thyme (3), its maximum diameter is substantially below the lock washer (5). This is convenient, since the purpose of the locking device of the invention is to prevent accidental removal of the spindle (3) from the receiving hole (2) and not to keep it pressed against the plate (1). It is precisely this vertical distance between the maximum diameter of the head (4) of the thyme (3) and the lock washer (5) elque, attached to the upper convex surface (9) of the head (4) of the thyme (3) ) allows to keep the lock when the screw (3) is introduced with a certain inclination, as shown in figure 11. Finally, in figure 12 it is shown how, even in the case of a bad introduction of the thyme (3), and Depending on its lack of penetration, the locking device can continue to function.

With respect to the industrial realization, obviously bio compatible materials will be used that will be well known for the expert in the field. It is only noteworthy that among the numerous tests carried out with lock washers (5), it has been shown as especially advantageous the use of power tile not in the execution of the crenellated circular crown of Figures 6 and 7. M adjustment of the retention force It is easy to vary the thickness and number and separation of the battlements and, since the width of the circulating crown reduces, it allows its introduction into the groove (6) without the need to carry out any, due to its high radial flexibility.

M locking device of the invention allows plates (1) to be made with a thickness of 2 mm, which increases up to 2.5 mm around the receiving holes (2). The device allows an inclination of the thyme (3) of up to 10 ^s , allowing it to be oriented at the discretion of the doctor towards the most appropriate screwing area. The incorporation of an inspection window (12) between the receiving holes (2) allows to appreciate the location and condition of the disk intervertebraL This inspection window (12) is replaced by a receiving hole (2) similar to those described to receive bone thymes (3), can be used to support a bone graft, an interbody fusion cage, or any other convenient element. The plate (1) in the execution just described biconcave by its lower part; that is, length ina and transverse Im curved entity to adapt to the spine geometry. The plates can be treated to provide greater hardness, resistance, or even to provide colors that are suitable for people. Said surface may be smooth to avoid this or this or integration of the plaque into the vertebra in the event that it must be removed in time, or textured and / or treated with any superficial finish osteoinductory / o or this or conductor, in the case that its arthrodesis The upper part can be smooth or present any type of surface treatment that is ticking.

Claims

1. Locking device on bolted plates for medical use of those of the type consisting of a plate (1) provided with receiving holes (2) through which fixing screws (3) pass, characterized by comprising a lock washer (5) joined by means of fixing to the plate (1), the lock washer (5) having an internal diameter smaller than the maximum diameter of a head (4) delto millo (3); in such a way that the lock washer (5) lets its head (4) pass from the thyme (3) to the transverse thread Im to the plate (1).

2. Device for locking in bolted plates for medical use, according to claim 1, characterized in that the fixing means comprise a groove (6), arranged in the receiving hole (2), into which the washer of lock (5).

3. Device for locking in bolted plates for medical use according to claim 1, characterized in that the receiving hole (2) of the plate (1) has a spherical support (7) capable of receiving a spherical support surface ( 8) which defines the head (4) of the thyme (3); in such a way that it allows a certain inclination of the thyme (3) with respect to the transverse direction of the plate (1).

4. Device for locking in bolted plates for medical use, according to claim 3, characterized in that the head (4) of the mule (3) has a convex upper surface (9), intended to interfere with the lock washer (5) .

5. Device for locking in bolted plates for medical use, according to claim 1, characterized in that the nose (3) has an ATTFN housing (10).

6. Device for locking screwed plates for medical use according to claim 1, characterized in that the thyme (3) has a threaded hole against rose a (11).

7. Device for locking in bolted plates for medical use, according to claim 1, characterized in that the core of the thyme (3) has an increasing diameter from the tip to the head (4).

8. Device for locking in bolted plates for medical use according to claim 2, characterized in that the lock washer (5) has the shape of a circular crown.

9. Device for locking screwed plates for medical use according to claim 8, characterized in that the circular crown has a cut.

10. Device for locking in bolted plates for medical use according to claim 9, characterized in that the cut is radial.

11. Device for locking in bolted plates for medical use, according to claim 2, characterized in that the lock washer (5) has the shape of a circular crown crenelled internally in its own plane.