Medical device locking mechanisms and related methods and systems

Medical device locking mechanisms and related methods and systems. In some embodiments, the medical device may comprise an outer surface defining one or more fastener openings configured for receiving one or more fasteners. The one or more fasteners may comprise an upper surface configured to be engaged by a component of the locking system to prevent fastener backout. A plurality of petal structures may be configured to be selectively expanded or contracted to engage the head portion and retain the at least one fastener within the fastener opening to prevent the fastener from backing out of the fastener opening. A biasing member may selectively engage the plurality of petal structures to either expand or contract the plurality of petal structures to facilitate locking the fastener(s) in place within the device.

FIELD OF THE INVENTION

Some embodiments disclosed herein relate generally to locking and/or anti-backout mechanisms for various medical devices and/or implants, and related methods. For example, various features and/or components of embodiments disclosed herein may be incorporated into and/or used in conjunction with various implants, including cervical plates, thoracolumbar fixation plates, anterior lumbar fixation plates, standalone interbody devices, bone fracture fixation plates, pedicle screw couplers, such as pedicle screw tulips, and the like.

Some embodiments may comprise one or more novel locking screws and a novel plate that works cooperatively therewith. The locking mechanism, the one or more novel locking screws, and/or a novel plate or other such implants may be used for the fixation/stabilization of the spine, such as the cervical spine. Alternatively, some embodiments may be configured for the fixation/stabilization of the lumbar spine, the sacral spine, and/or the placement of bone grafts, biocompatible inserts, and the like. Still other embodiments may be used for the fixation/stabilization of other anatomical structures and/or non-anatomical structures.

BACKGROUND OF THE INVENTION

The vertebrae of the human spine are generally arranged in a column, with an intervertebral disc disposed between each. These intervertebral discs transmit forces and perform a “cushioning” function. As a result of the stresses and strains continuously applied to the intervertebral discs, as well as disease, degeneration and/or deformity is relatively common. Typically, diseased, degenerated, and/or deformed intervertebral discs are treated by removal and the insertion of an implant, anatomical (i.e., a bone graft) or mechanical (i.e., a biocompatible insert), in the associated intervertebral space. The adjacent vertebrae are preferably immobilized using a plate, such as a cervical plate, during bone graft or biocompatible insert placement and subsequently until they fuse, for example.

Conventional cervical plates typically include a plurality of screw holes and one or more access holes, through which one or more bone grafts or other biocompatible inserts are placed. These cervical plates may span one or multiple levels, with a level defined by the presence of an intervertebral space, and may be secured to the vertebrae of the spine using a plurality of bone screws. Absent some sort of locking mechanism, these bone screws tend to reverse thread, or back out, over time. This reverse threading or backing out is obviously problematic. Various locking mechanisms exist in the art for preventing reverse threading or backing out, and typically involve the use of polymeric bushings, securing caps, securing cover plates, novel thread designs, and the like that prevent the bone screws from disengaging the vertebrae and/or cervical plate subsequent to installation. Many of these locking mechanisms are ineffective, overly complicated, cumbersome to implement, and/or unnecessarily expensive. Thus, what is still needed in the art is a robust, simple, and inexpensive locking mechanism for cervical plates or other medical devices or implants incorporating screws or other fasteners.

SUMMARY

In various exemplary embodiments, the present invention provides such a robust, simple, and inexpensive locking and/or anti-backout mechanism for a screw and/or other fastener of a plate or other medical implant or device. Various embodiments may be elegant in design and effective in performance. Some embodiments may utilize a plate with holes one or more of which may comprise a locking lip structure and/or receiving well, and locking screws that may incorporate a head portion having petal structures that are outwardly biased prior to insertion via an internally-disposed c-ring or another similar biasing member. Advantageously, in some embodiments, the lead-in torque of each of the locking screws is less than the lead-out torque of each of the locking screws. Thus, reverse threading or backing out is prevented.

In a specific example of an embodiment of a fastener locking system for a medical device, such as, for example, a cervical plate, a thoracolumbar fixation plate, an anterior lumbar fixation plate, an intervertebral device, a bone fracture fixation plate, or a pedicle screw coupler, the system may comprise an outer surface defining at least one fastener opening in the outer surface configured for receiving a fastener. The at least one fastener opening may comprise a lip structure positioned adjacent to the outer surface.

The system may further comprise at least one fastener, such as a locking screw, configured to be received in the at least one fastener opening. The at least one fastener may comprise a head portion comprising a plurality of petal structures configured to expand and contract to expand and contract a size of the head portion.

The system may further comprise a biasing member, such as a c-ring, configured to be positioned within the plurality of petal structures to expand a size of the head portion. The at least one fastener may be configured to contract to extend past the lip structure and then be expanded by the biasing member within the head portion such that the petal structures engage the lip structure to inhibit the at least one fastener from being removed from the at least one fastener opening.

In some embodiments, an upper portion of the lip structure may be angled inward towards a central axis of the at least one fastener opening such that the plurality of petal structures contracts as the head portion is inserted into the at least one fastener opening.

In another specific example of an embodiment of a fastener locking system for a medical device, the system may comprise a medical device comprising an outer surface defining at least one fastener opening in the outer surface configured for receiving a fastener. The at least one fastener opening may be defined at least in part by a plurality of petal structures configured to expand and contract.

The system may comprise a biasing member configured to be positioned around the plurality of petal structures to provide an inward bias to the plurality of petal structures and contract a size of the at least one fastener opening.

The system may further comprise at least one fastener configured to be received in the at least one fastener opening. The at least one fastener may comprise a head portion configured to be retained in the at least one fastener opening by the plurality of petal structures and the biasing member.

In some embodiments, the head portion may comprise an upper surface, and the plurality of petal structures may be configured to engage the upper surface after the biasing member has been positioned around the plurality of petal structures with the at least one fastener in the at least one fastener opening.

In some embodiments, the biasing member may be configured to be positioned concentrically around the plurality of petal structures.

In still another specific example of a fastener locking system for a medical device, the system may comprise a medical device comprising an outer surface defining one or more fastener openings configured for receiving a fastener. The system may comprise at least one fastener configured to be received in the at least one fastener opening. The at least one fastener may comprise a head portion comprising an upper surface.

The system may further comprise a plurality of petal structures configured to be selectively expanded or contracted to engage the head portion and retain the at least one fastener within the at least one fastener opening to inhibit the fastener from backing out of the at least one fastener opening. A biasing member may be configured to selectively engage the plurality of petal structures to either expand or contract the plurality of petal structures between an open configuration in which the at least one fastener is able to be removed from the at least one fastener opening and a closed configuration in which the at least one fastener is at least inhibited from being removed from the at least one fastener opening. The plurality of petal structures may be configured to engage the upper surface of the at least one fastener in the closed configuration.

In some embodiments, the plurality of petal structures may be part (in some embodiments an integral part) of the head portion. In some such embodiments, the biasing member may be configured to be positioned within the plurality of petal structures to expand a size of the head portion.

In some embodiments, the plurality of petal structures may together define a central driver bore configured to be engaged by a keyed tool. In some such embodiments, the central driver bore may comprise a polygonal shape.

In some embodiments, at least a subset of the plurality of petal structures may comprise an inner groove configured to receive the biasing member therein. In some such embodiments, each of the plurality of petal structures may comprise an inner groove configured to receive the biasing member therein.

In some embodiments, the plurality of petal structures may at least partially define the at least one fastener opening, and the biasing member may be configured to be positioned around the plurality of petal structures to provide an inward bias to the plurality of petal structures.

In some embodiments, the at least one fastener opening may comprise a lip structure positioned adjacent to the outer surface. As mentioned elsewhere herein, in some such embodiments, the petal structures may be configured to retain the fastener within the fastener opening beneath the lip structure such that the lip structure contacts an upper surface of a head portion of the fastener.

The features, structures, steps, or characteristics disclosed herein in connection with one embodiment may be combined in any suitable manner in one or more alternative embodiments.

DETAILED DESCRIPTION OF THE INVENTION

As described above, in various exemplary embodiments, the present invention provides a robust, simple, and inexpensive locking and/or anti-backout mechanism. Some embodiments may be elegant in design and effective in performance, and may utilize a plate with holes that each incorporate a locking lip structure and/or receiving well. Associated locking screws may each incorporate a head portion having petal structures that are outwardly biased prior to insertion via an internally-disposed c-ring or the like. Advantageously, in some embodiments, the lead-in torque of each of the locking screws is less than the lead-out torque of each of the locking screws. Thus, reverse threading or backing out may be prevented.

FIG. 1is an exploded perspective view of one exemplary embodiment of a cervical plate locking mechanism10of the present invention (being installed using a keyed tool, such as a keyed screwdriver18or the like), the cervical plate locking mechanism10including both novel plate and novel locking screw designs, as are described in greater detail herein below. Specifically, the cervical plate locking mechanism10comprises a plate12that is configured to be securely fixed to adjacent vertebrae of the cervical spine or the like via one or more locking screws14and one or more c-rings16. The keyed screwdriver18may be used to drive the one or more locking screws14through the plate12and into the adjacent vertebrae.

The plate12may comprise one or more screw-receiving holes13and, optionally, one or more access holes15for the placement of one or more bone grafts, biocompatible inserts, or the like. Preferably, the plate12is manufactured from a biocompatible material and is sized such that it achieves its intended purpose. Material, shape, and size selection may be selected according to the knowledge of those of ordinary skill in the art. Each of the one or more locking screws14may comprise a threaded portion17and a head portion19. The threaded portion17of each of the one or more locking screws14may be configured to pass through the one or more screw-receiving holes13of the plate12and securely fix the plate12to the adjacent vertebrae. Thread selection is well known to those of ordinary skill in the art.

The head portion19of each of the one or more locking screws14may be configured to securely engage each of the one or more locking screws14with the plate12. As described in greater detail herein below, the head portion19of each of the one or more locking screws14may be outwardly biased by the c-ring16, or by another similar biasing member or other mechanism or feature. Such mechanism or feature may be inserted and/or compressed into the head portion19of a given locking screw14. In some embodiments, the head portion19may expand automatically upon insertion of the c-ring16.

The c-ring16, or another comparable mechanism, and the head portion19of the given locking screw14may be again compressed and subsequently allowed to expand as they are inserted into a given screw-receiving hole13of the plate12. More specifically, in some embodiments, the head portion19of a given locking screw14may be allowed to expand in the receiving well of the given screw-receiving hole13. This insertion may be accomplished using, for example, a matching flat, triangle, square, star, hexagon, octagon, or other keyed screwdriver18, as appropriate. Preferably, the shape of the outside of the head portion19of each of the locking screws14substantially corresponds to the shape of the inside of the associated receiving well, although this is not a requirement.

FIG. 2is an exploded perspective view of one exemplary embodiment of the novel locking screw design ofFIG. 1, the locking screw14including a head portion19that incorporates a plurality of petal structures20that are outwardly biased by the internally-disposed c-ring16or the like. Locking screw14and/or its accompanying locking features may be incorporated into and/or used in conjunction with various implants, such as cervical plates, thoracolumbar fixation plates, anterior lumbar fixation plates, standalone interbody devices, bone fracture fixation plates, pedicle screw couplers, such as pedicle screw tulips, and the like.

As described above, c-ring16, or other comparable mechanism, may be selectively inserted and/or compressed into the head portion19of a given locking screw14, and then allowed to expand. The c-ring16, or other comparable mechanism, and the head portion19of the given locking screw14may then be compressed again and subsequently allowed to expand as they are inserted into a given screw-receiving hole13(FIG. 1) of plate12(FIG. 1), or of another screw-receiving hole of another plate or other implant or medical device.

More specifically, the head portion19of the given locking screw14may be allowed to expand in a receiving well of the given screw-receiving hole13. This insertion may be accomplished using a matching flat, triangle, square, star, hexagon, octagon, or other keyed screwdriver18(as shown inFIG. 1), as appropriate.

Preferably, the shape of the outside of the head portion19of each of the locking screws14at least substantially corresponds to the shape of the inside of the associated receiving well, although this is not a requirement. Accordingly, the head portion19of each of the locking screws14may comprise a plurality of concentrically-arranged petal structures20that are disposed around a central driver bore21, which may have a shape corresponding to that of the keyed screwdriver18. In one exemplary embodiment, the plurality of petal structures20may be formed by cutting concentrically-arranged slots into the head portion19of the locking screw14. Thus, the plurality of petal structures20may, in some embodiments and implementations, be integrally formed with the head portion19of the locking screw14. Alternatively, the plurality of petal structures20may be formed separately and then joined to the head portion19of the locking screw14.

The material characteristics and/or configuration of the plurality of petal structures20may, in some embodiments, impart the plurality of petal structures20with an inherent outward bias, which bias in some embodiments may be independent of the c-ring16or other comparable mechanism, although this is not required.

In some embodiments, the plurality of petal structures20may define an inner groove22extending around an inner perimeter of head portion19, such as around an exterior perimeter of central driver bore21, as shown inFIG. 2. Inner groove22may be configured to receive and retain the c-ring16or other comparable mechanism within the head portion19of the locking screw14.FIG. 2illustrates the head portion19of the locking screw14in an “unlocked” configuration, with the plurality of petal structures20being “open,” either due to the eventual insertion of the c-ring16or other comparable mechanism, or inherently.FIG. 3illustrates the head portion19of the locking screw14in a “locked” configuration, with the plurality of petal structures20being “closed,” either inherently or due to the eventual insertion of the head portion19of the locking screw14into a receiving well. Thus, in some embodiments, the plurality of petal structures20may be configured to be flexibly biased towards a locked/closed configuration such that the petals20can be flexed open to an unlocked/open configuration to receive c-ring16and then automatically revert to a locked/closed configuration with c-ring16therein. In some embodiments, the presence of c-ring16within head portion19may partially flex petals20towards an unlocked/open configuration (but not fully) so as to enlarge the diameter of head portion19and retain head portion19within a locking hole of a device, such as cervical plate12.

It can also be seen inFIGS. 2 and 3that petal structures20each partially defines an upper surface of head portion19of locking screw14. In the depicted embodiment, this upper surface is flat. In this manner, the upper surface of head portion19may be engaged with a lip structure of a locking hole of a device, such as cervical plate12, as discussed in greater detail below.FIGS. 2 and 3further depict that petal structures20together define central driver bore21(as shown inFIG. 3) comprising a polygonal opening, and can be expanded by flexing petal structures20(as shown inFIG. 2) such that petal structures20no longer define the same bore opening. In this manner, a keyed tool, such as keyed screwdriver18, may be used to expand central driver bore21by inserting the keyed tool and rotating it. This may allow for the c-ring16to be inserted into inner groove22.FIG. 3also illustrates that, in a closed configuration, petal structures20at least substantially enclose c-ring16within head portion19to prevent inadvertent removal of c-ring16after a locking screw14has been fully engaged within a corresponding receiving hole13.

FIG. 4is a partial cross-sectional view of the cervical plate locking mechanism10ofFIG. 1, the novel locking screw14ofFIGS. 1-3in the process of being inserted into the novel plate12ofFIG. 1. It should be noted that the head portion19of the locking screw14, and specifically the lower, outer portion of each of the plurality of petal structures20, optionally incorporates a recessed or otherwise weakened area24, or flexure, in order to facilitate the flexibility and/or outward biasing of the plurality of petal structures20by the c-ring16or other comparable mechanism, after it is inserted into the inner groove22that is manufactured into the middle, inner portion of each of the plurality of petal structures20.

One or more of the one or more screw-receiving holes13of the plate12or other such device may comprise an annular lip structure26through which the head portions19of the locking screws14may be inserted (with a compression/expansion action). This annular lip structure26may serve to retain the head portion19of the given locking screw14once it is fully inserted and expanded, thereby preventing the reverse threading or backing out of the locking screw14.

Optionally, the inner annular surface28of each of the screw-receiving holes13of the plate12may be curved in a generally concave manner, as shown inFIGS. 4-6, but shaped such that the lead-in torque of a given locking screw14is less than the lead-out torque or the locking screw14, i.e., the inner annular surface angles adjacent to the outer surface29of the plate12(at the “top” and “bottom” of the lip structure26) vary as experienced by an inserted locking screw14versus a removed locking screw14, with the “top” angle being greater (more vertical or steep) and the “bottom” angle being smaller (more horizontal or shallow), for example.

As also shown inFIGS. 4-6, the portion of the lip structure26immediately adjacent to the upper surface of petal structures20is preferably angled slightly inward towards a center axis of central driver bore21to facilitate desirable feel and function of head portion19of the locking screw14fitting into screw-receiving hole13and preventing backout of locking screw14thereafter.

FIG. 5is a partial cross-sectional view of the cervical plate locking mechanism10ofFIGS. 1 and 4, the novel locking screw14ofFIGS. 1-4being fully inserted into the novel plate12ofFIGS. 1 and 4. Again, it should be noted that the head portion19of the locking screw14, and specifically the lower, outer portion of each of the plurality of petal structures20, optionally incorporates a recessed or otherwise weakened area24, or flexure, in order to facilitate the flexibility and/or outward biasing of the plurality of petal structures20by the c-ring16or other comparable mechanism, after it is inserted into the inner groove22that is manufactured into the middle, inner portion of each of the plurality of petal structures20. Each of the one or more screw-receiving holes13of the plate12may comprise an annular lip structure26through which the head portions19of the locking screws14are inserted (with a compression-expansion action).

This annular lip structure26serves to retain the head portion19of the given locking screw14once it is fully inserted and expanded, as illustrated, thereby preventing the reverse threading or backing out of the locking screw14. As described above, optionally, the inner annular surface28of each of the screw-receiving holes13of the plate12is curved in a generally concave manner, but shaped such that the lead-in torque of a given locking screw14is less than the lead-out torque or the locking screw14, i.e. the inner annular surface angles adjacent to the outer surface29of the plate12(at the “top” and “bottom” of the lip structure26) vary as experienced by an inserted locking screw14versus a removed locking screw14, with the “top” angle being greater (more vertical or steep) and the “bottom” angle being smaller (more horizontal or shallow), for example.

FIG. 6depicts head portion19of locking screw14after it has been allowed to expand within receiving hole13by the expansion of c-ring16. As depicted in this figure, once this expansion takes place, an upper surface of head portion19of locking screw14contacts a lower surface of lip structure26to retain locking screw14in place and prevent, or at least reduce the possibility of, backup.

Thus, some embodiments may be configured to have a first, fully open configuration in which the petal structures20are fully open to receive c-ring16, a second, partially open configuration in which c-ring16flexes petal structures20partially open, and a third, fully-closed configuration in which c-ring16is absent and petal structures20are able to fully compress together.

FIG. 7is a partial cross-sectional view of the cervical plate locking mechanism10ofFIGS. 1, 4, 5, and 6the novel locking screws14ofFIGS. 1-5being inserted into the novel plate12ofFIGS. 1, 4, 5, and 6at various exemplary angles relative to both the plate12and the underlying vertebrae. In this embodiment, each of the receiving wells may be asymmetrical in shape such that the head portion19of each of the locking screws14snugly and securely engages the receiving well, although this is not necessarily illustrated. In other words, each of the receiving wells may be appropriately angled in the plate12in order to receive each of the angled locking screws14.

Referring toFIGS. 8-13, in another exemplary embodiment of a locking mechanism100of the present invention, the locking mechanism100again comprises both novel locking plate and novel screw designs, as are described in greater detail herein below. Locking mechanism100also comprises a cervical plate locking mechanism although, as mentioned above, this locking mechanism may be applied to a wide variety of other devices and implants, such as thoracolumbar fixation plates, anterior lumbar fixation plates, standalone interbody devices, bone fracture fixation plates, pedicle screw couplers, such as pedicle screw tulips, and the like.

More specifically, the cervical plate locking mechanism100comprises a locking plate102that is configured to be securely fixed to adjacent vertebrae of the cervical spine or the like via one or more screws104and one or more c-rings106. The keyed screwdriver (not illustrated) is used to drive the one or more screws104through the locking plate102and into the adjacent vertebrae. The locking plate102comprises one or more screw-receiving holes103and, optionally, one or more access holes105for the placement of one or more bone grafts, biocompatible inserts, or the like.

In some embodiments, the locking plate102may be manufactured from a biocompatible material and may be sized such that it achieves its intended purpose. Material, shape, and size selection may be selected by those of ordinary skill in the art. Each of the one or more screws104may comprise a threaded portion107and a head portion109. The threaded portion107of each of the one or more screws104may be configured to pass through the one or more screw-receiving holes103of the locking plate102and securely fix the locking plate102to the adjacent vertebrae. Thread selection may be as desired to those of ordinary skill in the art.

The head portion109of each of the one or more screws104is configured to securely engage each of the one or more screws104with the locking plate102. As described in greater detail herein below, a plurality of petal structures120disposed about each of the screw-receiving holes103may be inwardly biased by the c-ring106. Petal structures120may be incorporated into plate102, or into another implant or device comprising screw-receiving holes. A c-ring106, or another comparable mechanism may be expanded and subsequently allowed to contract around the petal structures120as the head portion109of a screw104is disposed in the receiving well of the given screw-receiving hole103. This insertion may be accomplished using a matching flat, triangle, square, star, hexagon, octagon, or other keyed screwdriver, as appropriate. Preferably, the shape of the outside of the head portion109of each of the screws104substantially corresponds to the shape of the inside of the associated receiving well, although this is not a requirement. Thus, in this exemplary embodiment, the plurality of petal structures120and the c-ring106have been shifted from the one or more screws104to the locking plate102, accomplishing the same purposes.

It can be best seen inFIG. 13that, once screw104is positioned in the receiving well/hole103and c-ring106has been positioned about the plurality of petal structures120, at least a portion of the locking mechanism (namely, a portion of the petal structures120) extends above a top surface of screw104to secure screw104within hole103and prevent, or at least inhibit, backout of screw104.