WO2001050967A1

WO2001050967A1 - Improved pedicular screw

Info

Publication number: WO2001050967A1
Application number: PCT/BR2001/000004
Authority: WO
Inventors: Vera Lúcia CAMARGO PAES
Original assignee: Camargo Paes Vera Lucia
Priority date: 2000-01-13
Filing date: 2001-01-11
Publication date: 2001-07-19
Also published as: BR0000275C1; BR0000275A

Abstract

'IMPROVED PEDICULAR SCREW', comprising a principal body (1), that is provided of a spindle (4), being this latter by its turn susceptible of being threaded in an expansible element (10), that is previously positioned in an orifice (18) produced in a vertebral body (20), that defines the bed (21) for the same; the principal body (1) has a fixing head (3), that through a threaded pin (16) promotes the immobilization of a rigid bar (2) that is positioned against a wall (6) that integrates a lateral opening (5) provided in said fixing head (3).

Description

"IMPROVED PEDICULAR SCREW" This report refers to an improved pedicular screw, of the type that is utilized in the composition of prosthesis intended to use in the vertebral column.

The vertebral column is classically subdivided in three segments, namely, a) anterior segment - composed by the anterior half of the vertebral body, anterior half of the intervertebral disk and longitudinal ligament; b) medium segment - composed by the posterior half of the vertebral body, posterior half of the intervertebral disk and posterior longitudinal ligament; and c) posterior segment - composed by the articular facets, yellow ligament, interspine ligament and supraspine ligament.

In some pathological situations, whether congenital or acquired, the combined lesion of two or more segments leads to the situation of segmental instability of the vertebral column. It is understood as segmental instability of the vertebral column the situation in which the column, under load or strain within physiological limits presents displacements that produce in the patient a clinical status of pain, sensitive alterations and/or lesion of nervous structure or of its wrappings.

Aiming to reach a situation of stability in the affected segment, a series of mechanical devices, utilizing several types of materials as steel, titanium, cobalt-chrome alloy, and other different metallic alloys, as well as materials denominated biomaterials , have been utilized in the composition of prosthesis that put in contact with different anatomical structures of the vertebral column try to promote the stabilization of the affected segment.

Among the different types of existing prosthesis, the professionals of the area as system of fixing (or stabilization) know one of the most utilized ones by pedicular screws.

Such systems, composed of sets of screws of different diameters and of different lengths, through the particular surgical technique, are surgically inserted in the vertebral pediculum (from where arises its denomination of pedicular screw) , until one reaching the medium and anterior segments of the vertebral body.

The systems of segmental stabilization of column with pedicular screws, use a minimum number of four screws, that united through bars, generally with circular cross section, promote the fixing of the segmental portion (s) in which they were utilized.

Thus, the immobilization with the reestablishing of the height between the different anatomical structures as well as the mechanical help arisen of the resistance of the materials utilized in the prosthesis, try to transform an unstable segment to a situation of an stable column segment. However, the systems currently available and pertaining to the state of the art, feature a series of inconveniences and/or limitations, among which may be mentioned: a) necessity of the previous preparation of the bone (milling) in the bone wall that will receive the pedicular screw; b) difficulty in the correct anatomical positioning of the pedicular screw, represented by the placing of the same in incorrect angling relative to the anatomic structure of the vertebral pediculum and its relations with the anterior and medium segments of the vertebral bodies and of the nervous structures; c) due to the characteristics of the type of thread of the currently used screws, the grip to the bone structures surrounding the screw, when submitted to the traction forces, show a tendency to get loose; d) the upper part of the existing screws, specially designed to receive the stabilizing bar, due to its design, determine difficulty in the surgical handling of fixing of the bar in the different screws in which the same must be fixed, as not always it is possible to obtain the desired angling of the bar relative to the mentioned screws, which are previously fixed in the different vertebral bodies.

More generically, the inconveniences verified in the constructivity adopted by the conventional pedicular screws, are also in the fact that the orifice to be made in the vertebral body of the patient must be elaborated very meticulously, under penalty of not obtaining a perfect anchoring of said screw in the structure of the vertebra.

Another inconvenience verified in the conventional constructivity is concerning to the fact that the pedicular screws (utilized in pairs) must be mounted in a perfect manner, namely, within the best possible alignment, what in the practice not always is easily attained.

It is further another inconvenience verified in the state of the art, the fact that the conventional constructivity relative to the pedicular screws belonging to the state of the art is excessively complex, requiring the employment of a great number of parts, which comprise, for example, nuts and lock nuts among others. Thus, it is characterized as one of the objectives of this patent of invention to provide an improved pedicular screw that features a simpler and functional constructivity.

Another objective of this patent of invention is in providing an improved pedicular screw that, in function of its particular constructivity, is not subject to the negative points verified in the state of the art .

More particularly, it is characterized as one of the objectives of this patent of invention to provide an improved pedicular screw, that has the following characteristics; a) to include in its constructivity a configuration that features a self-cutting thread, that dispenses the need of previous preparation (milling) of the bone wall that will be utilized as a bed for the same, said self-cutting thread, further features the advantage of not contributing (because of the fact of making unnecessary the previous preparation of the bone bed) to not have loss of bone substance; b) to be said screw now proposed provided of an internal orifice that permits that the same be fixed with the help of guiding string/wire, facilitating in this manner its correct placing relative to the different related anatomical structures; c) to have part of its structure provided with expansible means, what allows the obtainment of a substantially high fixing level, of what results, for example, that in being submitted to the forces of traction, load and moments of strain, the screw herein proposed do not present a tendency to get loose; and d) the cap of the screw is not part of the body of the same.

In face of the inconveniences and/or limitations verified in the state of the art pertaining to this subject, and aiming the proposed objectives, it was developed the improved pedicular screw herein commented, which will be detailedly described with reference to the below listed drawings, in which: the figure 1 illustrates a lateral and exploded view of the herein-proposed screw, which view demonstrates its main components; the figure 2 illustrates an orthogonal view taken of the figure 1, that demonstrates other details of the improved pedicular screw herein mentioned; the figure 3 illustrates a view in schematic cut that is taken of the figure 1, such as the one indicated by the "A" arrow; the figure 4 illustrates of view of the threaded pin that is utilized to promote the immobilization of the metallic stem near to the head of fixing of this improved pedicular screw, said view being taken pursuant to the indication of the arrow "B" of figure 2; the figure 5 illustrates a view of the vertebral column, more particularly of its lumbar region, where it is exemplified the use of a pair of the present improved pedicular screw; the figure 6 illustrates a cutting of the vertebral column, cutting which is taken as indicated by the line of the "C" - "C" cutting of said figure 5, and will serve to demonstrate the positioning of this pedicular screw when duly fixed to the vertebral body of the patient; the figure 7 illustrates a constructive variant of the expansible element that integrates this improved pedicular screw; and the figures 8 and 9 show two views, one is an exploded perspective view and the other is a lateral partially cut view of another embodiment of the present pedicular screw.

According to the illustrations of the above listed figures, the improved pedicular screw is characterized by a principal body 1, that serves as a place for the anchoring of a stem or rigid bar 2, that may be better observed through the figure 5, where due to a merely illustrative matter is demonstrated only one of the two sets normally utilized and that are formed by a pair of the subject screws, and, of course, of the corresponding bar 2.

The principal body 1 of the improved pedicular screw is composed by a fixing head 3, that is developed into a spindle 4, said fixing head 3 features an arched lateral opening 5, that finishes in a rounded wall 6, place where one of the extremities of the rigid bar 2 will rest, such as demonstrated in the figures 1 and 6.

The fixing head 3, in its lower extremity 7, incorporates a thread string 8, that jointly with the thread 9 of the spindle 4, guarantee the immobilization of the principal body 1 near to the structure of an expansible element 10. The expansible element 10 features an essentially tubular shape, incorporating in its external face 11 a thread string/wire 12 with self-cutting characteristics, namely, being said thread string/wire 12 constructively defined so that the expansible element 10, when being threaded in the orifice 18 produced in the vertebral body 20, opens a way into the bone mass that constitutes its laying bed 21, such as schematically demonstrated in the figure 6.

The expansible element 10 features at least a pair of longitudinal slits 13, that guarantee the expansible effect of the same.

The expansible element 10, features a central orifice 14, that relies on an internal thread 15, that originating in the extremity of the same, extends itself by approximately two thirds of its total length.

The internal thread 15 is dimensioned and defined so as to establish the connection with the thread 9 of the spindle 4 of the principal body 1, being that referred thread 15, in the extreme region of the expansible element 10 develops itself into an other segment of thread 15a, that is specifically intended to be connected with the thread 8 located in the interior extremity 7 of the fixing head 3, supplementally reinforcing the mechanical resistance of the present improved pedicular screw, after this being entirely mounted, such as the one illustrated in figure 6. The herein treated improved pedicular screw is formed further by a threaded pin 16, that is utilized to proceed the immobilization of the rigid stem 2, being this latter duly positioned in the desired point near the wall 6 of the lateral opening 5 of the fixing head 3, said threaded pin 16 may be positioned in a threaded orifice 17 that is incorporated in the upper region of the fixing head 3 and reaches the mentioned lateral opening 5, such as illustrated in figures 1 and 2.

The subject pedicular screw proves itself more efficient than those pertaining to the state of the art.

In this case, the improved pedicular screw is effectively mounted through a preliminary stage that is represented by the elaboration of an orifice 18, that crosses the pediculum 19 of the vertebral body 20, thus defining the bed 21, that reaches the vicinities of its central region 22.

Made the orifice 18, it is effected the positioning of the expansible element 10, what occurs through the rotation of the same, and due to the action of its thread 12, that being of the self-cutting type, opens way in the bed 21 and threads itself along the wall of said orifice 18. Once the expansible element being positioned 10, it is effected the mounting of the principal body 1, that is then threaded in the expansible element 10, being that, as the spindle 4 advances along the orifice 14, one determines as consequence the expansion of the element 10, which factor further guarantees the rigidity of the mounting of this improved pedicular screw near to the vertebral body 20.

Having been positioned a pair of the improved pedicular screws configured according to the herein proposed constructivity, it may be, then, mounted the rigid bar 2, that is introduced in the corresponding lateral openings 5 of each one of the fixing heads 3. The determination of the best location for the stem 2 is made in a manner more simple than that verified in the conventional system, as the lateral openings 5 of each fixing head 3 are projected so as to allow a greater liberty in the positioning of said stem 2, before its actual immobilization through the threaded pin 16.

The bar 2 having been mounted, this may be then firmly trapped and immobilized through the already mentioned threaded pin 16, of each one of the fixing heads 3.

This constructivity, as must have been effectively clarified by the above description, presents three main advantages relative to the conventional system, being the first of them represented by the greater efficiency in the anchoring of the thread near to the structure of the vertebral body 20, particularity that is obtained by the utilization of the expansible element 10; the second advantage concerns that fact that due to the anticipation and use of said expansible element 10, the strictness in the elaboration of the orifice 18 becomes less necessary and dispenses the stage of milling, that is, it is admitted a greater tolerance in the execution of said orifice 18, since the final anchoring effect is provided by the expansion of the element 10 after this latter being entirely positioned in said orifice 18; and the third main advantage of this constructivity is in the greater freedom for the positioning of the fixed stem 2, which freedom is resulting of the configuration of the fixing head 3 and more particularly is arisen of the provision and configuration of said lateral opening 5 of said fixing head

3.

The figure 7 illustrates in a partially cut manner a construction variant of the expansible element 10 that in this case is specially indicated by the reference 10a.

The said expansible element 10a is characterized by the fact of featuring an essentially tubular shape, incorporating in its external face 11a a thread string/wire 12a with self-cutting characteristics, such as the one presented by the expansible element 10. The expansible element 10a, in a manner similar to that verified in the expansible element 10, relies on at least a pair of longitudinal slits 13a, that guarantee the expansible effect of the same.

The expansible element 10a also features a central orifice 14a that has an internal thread 15a, that starting in the extremity of the same extends itself by roughly two thirds of its total length.

The internal thread 15a is dimensioned and defined so as to establish the connection with the thread 9 of the spindle 4 of the principal body 1, such as it occurs with the expansible element 10, being that said thread 15a, in the extreme region of the expansible element 10a develops in another segment of thread 15a¹, that is specifically intended to be connected to the thread 8 located in the lower extremity 7 of the fixing head 3.

Contrariwise as it occurs with the expansible element 10, in the expansible element 10a the corresponding slits 13a start from the vicinities of the region where internally the threads 15a and 15a' interconnect themselves, being that said slits 13a reach the anterior extremity of the element 10a, which, as a consequence, is configured in an open manner.

Figures 8 and 9 show another embodiment of the present pedicular screw which is characterized by the fact the use of the expansible element 10 is no more required.

That is the reason why the related thread 9 of the embodiment of Figures 8 and 9 shows an embodiment which can be fixed to the bony mass of the pedicular structure which is to received the present screw.

Another novelty aspect which is better depicted in Figure 9 is the fact that the body of the present screw shows an inner channel C which turns the screw into a cannular piece .

Claims

1. "IMPROVED PEDICULAR SCREW", of the type that may be utilized to promote the fixing of elements intended to guarantee the reestablishing of the condition of stability between vertebral bodies (20) of a vertebral column, characterized by the fact of comprising a principal body (1) , that serves as a location for the anchoring of a stem or rigid bar (2) , being the mentioned principal body (1) of the improved pedicular screw composed by a fixing head (3) , that develops into a spindle (4) , said fixing head (3) features an arched lateral opening

(5) , that terminates in a rounded wall (6) , place where will rest one of the extremities of the rigid bar (2) ; the fixing head (3), in its lower extremity (7), incorporates a thread string/wire (8) , that jointly with the thread (9) of the spindle (4) guarantee the immobilization of the principal body (1) near to the structure of the expansible element (10) .

2. "IMPROVED PEDICULAR SCREW", as claimed in 1, characterized by the fact that the expansible element (10) features an essentially tubular shape, incorporating in its external face (11) a thread string/wire (12) .

3. "IMPROVED PEDICULAR SCREW", as claimed in 2, characterized by the fact that the thread string/wire (12) features self-cutting characteristics.

4." IMPROVED PEDICULAR SCREW", as claimed in 2 and 3, characterized by the fact that the thread string/wire (12) is constructively defined so that the expansible element (10) , when being threaded in the orifice (18) , produced in the vertebral body (20) , opens way through the bone mass that constitutes its laying bed (21) .

5. " IMPROVED PEDICULAR SCREW" , as claimed in 1, characterized by the fact that the expansible element (10) features at least a pair of longitudinal slits (13), that guarantee the expansible effect of the same, said expansible element (10) , features a central orifice (14), that has an internal thread (15), that starting from its extremity, extends itself by roughly two thirds of its total length; the internal thread (15) is dimensioned and defined so as to establish the connection with the thread (9) , of the spindle (4) of the principal body (1) , said thread (15) , in the extreme region of the expansible element (10) develops into another segment of thread (15a) , that is intended to be connected with the thread (8) located in the lower extremity (7) of the fixing head (3) of the principal body (1) .

6. "IMPROVED PEDICULAR SCREW", as claimed in 1, characterized by the fact of having a threaded pin (16) , that is utilized to effect the immobilization of the rigid stem (2) , said threaded pin (16) may be positioned in a threaded orifice (17) that is incorporated in the upper region of the fixing head (3) .

7. "IMPROVED PEDICULAR SCREW", as claimed in 1, characterized by the fact that the expansible element (10) features a construction variant indicated by the reference (10a) , which features an essentially tubular shape, incorporating in its external face (11a) a thread string/wire (12a) with self-cutting characteristics; the expansible element (10a), in a manner similar to that verified in the expansible element (10) , relies on at least a pair of longitudinal slits (13a) , which guarantee the expansible effect of the same, said expansible element (10a) also features a central orifice (14a) , that has an internal thread (15a) , that starting from the extremity of the same, extends by roughly two thirds of its total length.

8. " IMPROVED PEDICULAR SCREW" , as claimed in 7, characterized by the fact that the internal thread (15a) is dimensioned and defined so as to establish the connection with the thread (9) of the spindle

(4) of the principal body (1) , being that said thread

(15a) , in the extreme region of the expansible element

(10a) develops into another segment of thread (15a¹), that is specifically intended to be connected with the thread

(8) located in the lower extremity (7) of the fixing head

(3) ; contrariwise to what occurs with the expansible element (10) , in the expansible element (10a) the corresponding slits (13a) depart from the vicinities of the region where internally the threads (15a) and (15a¹) interconnect, being that said slits (13a) reach the anterior extremity of the element (10a) , which, by way of consequence is configured in an open way. 9 "IMPROVED PEDICULAR SCREW", characterized by the fact that it comprises an embodiment in which the thread (9) shows such an embodiment so as to permit that the screw be directly fixed to the bony structure which is to receive it; said embodiment also comprises an inner longitudinal channel (C) which turns the screw into a cannular piece.