Fixing device for a surgical anchor member

A fixing device is for a surgical anchor member. The fixing device may include a control component joined to a connecting portion, which is in turn connected to a shaft provided at one end with coupling units for connecting the fixing device to a fastening element suitable to couple with a respective fastening seat of a surgical anchor element. The fixing device may include a centering component for the coupling of the fastening member with the respective fastening seat of the surgical anchor member.

RELATED APPLICATION

This application is based upon prior filed copending International Application No. PCT/IB2015/052459 filed Apr. 3, 2015, which claims priority to Italian Application No. MI2014A000649, filed Apr. 8, 2014, the entire subject matter of these applications is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is directed to a medical device, and more particularly, to a device for operating on spine disorders and related methods.

BACKGROUND

Operations on these types of characteristic problems of the spine frequently require the stabilization of a portion of the spinal tract so as to facilitate the fusion of two or more vertebrae into a single bone structure. This type of operation is frequently used for the correction of many pathological conditions of the vertebral column such as, for example, degenerative disc diseases, scoliosis, spinal stenosis or the like.

The stabilization of the vertebral column allows bone tissue to be created in the intervertebral area. In this way, part of the vertebral column is fused into a single bone structure. The stabilization of the vertebral column has been studied in the past and various methods and devices have been developed for the correction of many characteristic diseases of this part of the body, in order to stabilize its configuration, facilitating vertebral fusion at various levels.

One of these known systems envisions a corrective bar being arranged longitudinally along the spinal tract that requires surgery. This corrective bar is conformed so as to restore the correct anatomical shape, which is peculiar to that specific tract of a healthy vertebral column.

Therefore, with this method, the corrective bar is positioned along the vertebral column to engage various vertebrae, according to requirements. It should be noted that, typically, in this type of surgery two parallel corrective bars are arranged to the rear of the sides of the central area of the patient's vertebral column. Therefore, during the surgery, the pair of corrective bars is fixed to the vertebral column through various anchoring means including, for example, screws. The screws are fixed to the bone structure, typically to the vertebral peduncle.

The inclination of the corrective bar and, consequently, the positioning of the set screws, vary according to the type of correction to be made and, naturally, vary from vertebra to vertebra. One type of screws known in the state of the art that are widely used in the application are polyaxial screws. Here, the head of the screw can vary its angulation with respect to the threaded stem for better adaptation to the surgical requirements until a set screw is coupled to it.

It appears clear how it is fundamental, for a successful operation, to correctly fix both the corrective bar and the screws to which it will be fixed. In fact, the corrective bar is inserted into a head of the polyaxial screw and secured thereto through the fixing of a set screw, coupled by means of a helical coupling so that, once the coupling is complete, the set screw is locked in the desired position and the corrective bar is fixed into the housing provided in the screw head. Therefore, until the set screw is correctly coupled, the head of the polyaxial screw is free to move.

In typical approaches, instruments are known for the coupling of a set screw with a head of a polyaxial screw. The fixing instruments can be likened to screwdrivers through which it is possible to act on the set screw to create the threaded coupling between it and the head of the polyaxial screw. In fact, through the coupling, the set screw drops into the head of the polyaxial screw until it presses against a corrective bar and stops against it. In this way, the corrective bar is controlled to press against the spherical end of the threaded stem of the polyaxial screw, which is also contained in the head of the screw. In this way, the spherical end of the stem of the polyaxial screw and the bar are locked in the desired position.

SUMMARY

Generally speaking, a fixing device is for a surgical anchor member. The fixing device may include a control component joined to a connecting portion, which is in turn connected to a shaft provided at one end with coupling units for connecting the fixing device to a fastening element suitable to couple with a respective fastening seat of a surgical anchor element. The fixing device may include a centering component for the coupling of the fastening member with the respective fastening seat of the surgical anchor member.

DETAILED DESCRIPTION

Hence, it appears clear how it is necessary for the set screw to be located correctly within its housing provided in the head of the polyaxial screw, so as to guarantee the correct relative positioning of the bar with respect to the threaded stem of the polyaxial screw. Screwdrivers of the prior art, however, are not able to provide for the required functions satisfactorily and have some drawbacks.

A drawback of what is known in the state of the art is the possible off-axis insertion of the set screw with respect to the axis of the screw head in which the female screw thread is present. This incorrect insertion is not detected by the surgeon until a sticking phenomenon occurs, which stops the relative movement of the set screw with respect to the female screw thread of the polyaxial screw. The surgeon must then free the set screw and proceed to insert it again with the consequent wasted time and the possibility of misalignment of the polyaxial screw head with respect to its threaded stem.

Another drawback of what is known in the state of the art is the lack of alignment means for aligning the set screw with respect to the screw head so as to provide for the insertion of the set screw in a secure way. Another drawback of what is known in the state of the art is the need to operate manually on the screw head in order to achieve the perfect positioning of the corrective bar and to, still manually, maintain the chosen position for the screw head, during the set screw assembly operations.

The present invention, starting from the notion of these disadvantages, intends to provide a remedy for them. An object of the present invention is to provide a fixing device for a surgical anchor member able to guarantee the perfect automatic alignment between a set screw and a head of the anchoring device. Another object of the present invention is to provide a fixing device for a surgical anchor member able to allow a user to easily handle the device in situ, during the surgical operation, for the purpose of the correct fixing of the anchor member.

A further object of the present invention is to provide a device as specified that is able to allow the user to act on it using one hand only. Another object of the present invention is to provide a fixing device for a surgical anchor member able to be detachably coupled with the set screw, allowing its insertion into the screw head quickly, simply and easily. It will also be an object of the present invention to provide a device as illustrated in the following description that has a contained weight, reduced dimensions and is easy and comfortable to use.

In the drawing,100indicates the fixing device (i.e. a fixation device) for a surgical anchor member according to the present invention, as a whole. The fixing device100includes (FIG. 1): a control device6, for example, a handle, coated in plastic/rubber material and having characteristic dimensions such as to make it easy and comfortable for the user to use; and a metal connecting portion5, integral with the handle6and adapted to make the handle6solidly joined to a shaft4, made of rigid material such as, for example, metal, metal alloys, polymeric and/or composite materials, having a circular section with a central area4.3with a constant section and a substantially cylindrical shape, an end4.2with a larger section and an end4.1with a variable section; an elastic means, for example, a spring3, entirely fitted on to a part of the end4.1of the shaft4and engaged to strike a contact area4.11with a larger section than the end4.1, on one of its sides proximal to the handle6, and engaged to strike a centering means1, for example, a fork, on one of its distal sides to the handle6.

The fork1is fitted onto the free end portion4.12of the end4.1. Integral with the free portion4.12and protruding from it, there is a stop means, for example, a pin2having a transversal axis with respect to the axis of the shaft4. Furthermore, the free portion4.12has a through channel4.13(FIG. 4), extending for a substantial part of the free portion4.12, U-shaped and such as to divide the free end portion4.12into two coupling units4.14and4.15.

The fork1substantially has two parts: a first area, known as the engagement area1.1and a second area, known as the coupling area1.2. This coupling area1.2has a substantially hollow circular section and is fitted and free to slide on the free end4.1of the shaft4, interacting with the shaft4through the spring3. In fact, the spring3is engaged, on one side, striking the back1.21of the coupling area1.2and on the other striking the increased section area4.11of the shaft4. Thus, by keeping the fork1still and pressing on the handle6, the spring3is compressed, bringing the free end4.12to slide freely into the fork1, hence allowing a relative translation between the fork1and the shaft4. By removing the pressure on the handle6, the spring3regains its neutral position (also known as the rest position) and the position of the fork1, in relation to the free end4.12of the shaft4, returns to the initial one. It is to be noted that the spring3can be assembled on the end4.1of the shaft4in the pre-load configuration; however, for the purpose of the present description, the term “neutral position” or “rest position” will be used for the spring3which has no loads acting on it imposed by the user. On the coupling area1.2of the fork1and extending for a substantial part of it, there is an aperture1.22, with a substantially rectangular shape and having, on its proximal side to the handle6, a seat, for example, a notch1.23, centered with respect to the axis of the shaft4and adapted to be engaged with the pin2, when the spring3is in neutral position.

The engagement area1.1has two engagement means, for example, two prongs1.11and1.12, having a tapered section towards the free ends and adapted to be coupled with a respective retaining area, for example, two centering grooves22, provided in a fastening seat21.1of a head21of a surgical anchor member20. Note that, between the two prongs1.11and1.12, in a substantially centered position, the free end4.12of the shaft4protrudes. As mentioned, the free end4.12of the shaft4is split into two coupling units4.14and4.15by the through channel4.13. The two coupling units4.14and4.15have a reduced section for a substantial part of the section protruding between the two prongs1.11and1.12, so as to form an abutment4.17(FIG. 4).

The fixing device100for a surgical anchor member20according to the present invention, as illustrated in the appended drawing purely by way of example, is configured for the coupling of a fastening element10, for example, a set screw, within a fastening seat21.1of the head21of a surgical anchor member20, for example, a polyaxial screw as illustrated in FIGS. from8to13, an anchoring hook50as illustrated inFIG. 14, a monoaxial screw60as illustrated inFIG. 15, or a lateral connector70as illustrated inFIG. 16.

Gripping the fixing device100by the handle6, the user positions the set screw10on a support surface (not shown) and the prongs1.11and1.12in proximity to the side of the set screw10. By exerting pressure on the handle6, through the rigid structure formed by the handle, the connecting portion5, the shaft4and its increased section area4.11, the spring is compressed and allows the relative translation of the free portion4.12of the end4.1of the shaft4with respect to the fork1. The translation makes the two coupling units4.14and4.15be forced first against the upper part11of the set screw10and then to approach one another until they close the channel4.13and penetrate into the relevant blind coupling cavity (known and not illustrated) provided in the set screw10, hence performing the solid coupling between the set screw10and the fixing device100.

It is to be noted that the shape of the coupling units4.14and4.15is such that, once they are forced to touch one another closing the channel4.13as described above, they assume a complementary conformation to the blind coupling channel provided in the set screw10, so as to be able to rotate integrally therewith. Please also note that the coupling units4.14and4.15penetrate into the blind cavity until the surface11of the set screw10strikes against the abutment4.17. In this way, an optimal coupling between the two coupling units4.14and4.15and the set screw10is guaranteed, preventing the set screw10being able to return along the free end4.12during the helical coupling operations with the head of a surgical anchor member, for example, the head21of the polyaxial screw20as illustrated inFIGS. 8-13. Furthermore, the coupling provides a certain resistance to tensile strain aiming to separate the set screw10from the fixing device100, without this making the voluntary decoupling of the set screw10from the fixing device100difficult.

Once the coupling has been performed, as described above, it is possible to bring the two prongs1.11and1.12to engage the respective retaining areas, for example, the grooves22, provided in the head21of the polyaxial screw20, as illustrated inFIG. 8. This operation is facilitated by the presence of the pin2in the coupling position with the notch1.23of the aperture1.22, when the spring3is in neutral position. In fact, when the pin is in the coupled position with the notch1.23, it prevents, within certain limits, the fork1turning idly with respect to the free end4.12, hence guaranteeing a quick and easy coupling of the prongs1.11and1.12with the respective grooves, for example, those envisaged on the head21of the surgical anchor member20, in the reference figure, a polyaxial screw.

Advantageously, at this point, it is possible to act on the handle6of the fixing device100in order to choose the correct alignment of the head21of the polyaxial screw20with respect to its threaded stem25, as illustrated inFIG. 10. This is possible thanks to the engagement of the notch1.23by the pin2. In fact, when the spring3is in the neutral position, the pin2, assembled transversally to the axis of the shaft4and solidly joined thereto, is engaged within the notch1.23. This coupling ensures that the fork1is forced to rotate integrally with the shaft4when the torque imposed on the handle6by the user falls within certain limits, the limits being set by the shape of the notch1.23.

Once the desired position has been reached, through pressure on the handle6, the consequent compression of the spring3and relative translation of the end4.12with respect to the fork1, the pin2is disengaged from the notch1.23. At this point, thanks to a torque applied by the user on the handle6, the shaft4can be rotated and, consequently, also its end4.12with which the set screw10is integral, while the fork1remains coupled to the head21of the polyaxial screw20without rotating. In this way, thanks to the rotation, the set screw10is coupled in the fastening seat21.1of the head21of the polyaxial screw20until the head21of the polyaxial screw20is fixed in the desired position with respect to the stem25of the polyaxial screw20and the consequent locking of the set formed by the corrective bar30and the insert40.

It is clear from the above that the presence of the prongs1.11and1.12in coupling with the grooves, for example, those provided on the head21of the polyaxial screw20, guarantee the perfect alignment between the set screws10and the head21of the surgical anchor member, for example, the polyaxial screw20, preventing sticking phenomena between the thread of the set screw10and the relative female screw thread provided in the fastening seat21.1of the head21of the polyaxial screw20.

It is easy to understand, for a person skilled in the art, how the present invention could be functional to the coupling of a set screw10, potentially with a different shape from that illustrated in the drawings appended hereto, purely by way of non-limiting example, but with similar functions, with other types of anchor members used in surgical practice. Some brief descriptions follow of possible uses of the present invention in combination with anchor members typically used in the surgical field. Where not specified otherwise, all the advantageous characteristics described above illustrating the preferred embodiment remain valid also for the variations to the uses illustrated below.

An example of the use of the present invention with an anchor member of a different type with respect to what is described above is illustrated inFIG. 15. In theFIG. 15, instead of a polyaxial screw20, as illustrated inFIGS. 2 and 8-13, the fixing device100is used in cooperation with a monoaxial screw60. In this case, the alignment function of the head61of the monoaxial screw60with its threaded stem is not required, since the monoaxial screw60has a fixed head61. However, the presence of prongs1.11and1.12received in the retaining areas62provided in the head61of the monoaxial screw60allow the perfect positioning of the set screw10with respect to its respective seat61.1provided in the head61of the monoaxial screw60, guaranteeing the correct fastening of the bar30to the monoaxial screw60.

Another example of the use of the fixing device100according to the present invention is illustrated inFIG. 14. In theFIG. 14, the fixing device100is used for the threaded coupling between a set screw10and another anchor member50, for example, an anchoring hook. The anchoring hook50has a fastening seat51.1, internally threaded, in the head51of the anchoring hook50. Also in this case, there are retaining areas52, provided on the head51of the anchoring hook50adapted to receive the prongs1.11and1.12of the fixing device. As described for the preceding methods of use, the use of prongs1.11and1.12of the respective retaining areas52creates the perfect alignment between the set screw10and the head51of the anchoring hook50, allowing the correct placement of the set screw10and implementing the fastening of the bar30solidly to the anchoring hook50.

Finally, a further use of the fixing device100according to the present invention is illustrated inFIG. 16. In theFIG. 16, a further anchor member70is illustrated, for example, a lateral connector, able to be anchored to a second anchor member, for example, a polyaxial screw like those described above (not illustrated), and able to receive a bar30in a housing71.1within its head71. Also in this case, the head71of the anchor member70is adapted to house a set screw10and has retaining areas72adapted to receive prongs1.11and1.12of the fixing device100. As described above, the coupling of the prongs1.11and1.12with the respective retaining areas72makes the perfect alignment between the set screw10and the head71of the lateral connector70possible so as to make the threaded coupling between the set screw10and the head71of the anchor member70secure, quick and simple. By creating this coupling the bar30is locked in the desired position within the head71.

As appears clearly from the above description, the present invention advantageously achieves the objects described above. Naturally, numerous variants can be made to what is described and illustrated merely by way of non-limiting example, without for this reason departing from the protective scope of the present invention and therefore from the domain of the present industrial patent.