SYSTEM AND METHOD FOR JOINING BONEY STRUCTURES

Disclosed are system and methods that use at least one non-threaded anchor and an implant with at least one aperture to join boney structures, where the interaction of the head of the anchor with the implant aperture causes the anchor to move transversely with respect to an initial trajectory. This movement causes compression or distraction of the boney structures which are coupled to the anchors.

TECHNICAL FIELD

The disclosed invention relates in general to orthopedic and dental surgically implanted devices, and in particular to implantable devices which use a plurality of non-threaded anchors with an implant or plate to compress and join boney structures.

BACKGROUND INFORMATION

Over a hundred years ago surgeons determined that a combination of screws and plates worked as a method of internal fixation of two or more bone structures. In time surgeons empirically learned that placing two or more bones in mechanical compression greatly improved the speed and quality of bone healing. Mechanical compression was then rendered through external devices and internally fixated with the screw plate device.

Many believe that localized bone compression is the orthopaedic standard for bone healing. Current art uses plates with dedicated screw channels or directive apertures that determine the range of screw angulation and the resultant course of the screw's trajectory.

In many orthopedic related procedures, however, such as spinal, sternal chest closure, dental, and numerous orthopedic reconstructions, plates and screws have not been found to follow compressive bone healing principals. Instead, the screw plate configurations stabilize the boney structures, but do not typically compress the bone structures together. Furthermore, threaded anchors such as screws have many disadvantages, including the tendency to back out of a boney structure over time.

Therefore, what is needed is a novel plate anchor system that consistently achieves bone compression or distraction of two boney structures.

SUMMARY

In response to these and other problems, in one embodiment, there is a system that includes non-threaded anchors that follow a trajectory into a boney structure and then a non-threaded head of the anchor interacts with the aperture features in an implant to cause the head of the anchor to move transversely which can cause compression or distraction of boney structures coupled to the anchors.

These and other features, and advantages, will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. It is important to note the drawings are not intended to represent the only aspect of the invention.

DETAILED DESCRIPTION

When directions, such as upper, lower, top, bottom, clockwise, counter-clockwise, are discussed in this disclosure, such directions are meant to only supply reference directions for the illustrated figures and for orientation of components in respect to each other or to illustrate the figures. The directions should not be read to imply actual directions used in any resulting invention or actual use. Under no circumstances, should such directions be read to limit or impart any meaning into the claims.

FIG. 1Ais a proximal perspective view of one aspect of a non-threaded anchor100which can be used with several embodiments of the present invention.FIG. 1Bis a longitudinal section view of the non-threaded anchor100.FIG. 1Cis a top perspective view of the anchor100orientated to illustrate a distal end122. In contrast,FIG. 1Dis a bottom perspective view of the anchor100.

Turning now toFIGS. 1A through 1D, in the illustrative embodiment, the non-threaded anchor100includes a non-threaded proximal end or head portion102which is coupled to a non-threaded elongated body portion104. The non-threaded elongated body104has a longitudinal or center axis106, which in this embodiment, partially defines an initial trajectory into a boney structure as will further be discussed below. In the illustrated embodiment, the head portion102and the elongated body portion104share the central axis106which is curved within the elongated body portion104and straight within the head portion102. In other embodiments, the elongated body portion104may be straight in which the center axis106would also be straight. In yet other embodiments, the head portion102may be curved and likewise, the center axis106within the head portion may also be curved.

FIG. 1Bis a section view of the anchor100with the addition of dotted lines108. For purposes of illustration, the dotted lines108are boundary lines that represent the portion of the anchor100that is generally equal distance with respect to the center axis106in a direction110that is generally normal or transverse to the direction of the center axis106. For purposes of this disclosure, any portion of the head portion102that is outside of the dotted lines108is defined as “offset” or eccentric to the center axis106. As can be seen most clearly inFIG. 1B, the non-threaded head portion102includes a first or symmetrical head portion112that is substantially within the boundary lines108and a second portion or “offset” portion114of the head portion102that is outside of the boundary lines108. Looking from the perspective ofFIG. 1B, the boundary lines108are generally symmetrical or equal distance from the center axis106in a direction110which is normal to the center axis. Thus, for purposes of this disclosure, the second or offset portion114of the head portion102that is outside of the boundary lines108is defined as an offset portion114from the center axis. In other words, an unsymmetrical mass or structure beyond an equal distance line from the center axis is considered to be an “offset” portion114of the head portion102for purposes of this disclosure. In this embodiment, a transition or blended surface117allows for the smooth transition between the surface of the elongated body portion104and the offset anchor head portion114.

In certain embodiments, a proximal end116of the anchor100contains an engagement surface118that is angled with respect to the normal direction110of center axis106. In certain embodiments, the engagement surface118may have engagement features, such as aperture120for engaging with various embodiments of insertion instruments. In the illustrative embodiment, the longitudinal axis of the aperture120may be parallel with respect to the center axis106.

As can be best seen inFIGS. 1C and 1D, a distal end122of the anchor100is designed to penetrate and be pushed through a boney structure. Consequently, at the distal end122the cross-sectional area of the body portion104is significantly reduced which also reduces the force necessary to push the distal end122through the boney structure (not shown). In the illustrative embodiment as best seen inFIG. 1C, the distal end122has a generally semi-circular or horseshoe shaped cross-sectional area. For instance,FIG. 1Eis a partial perspective section view where the body portion104has been cut close to the distal end122. The cut inFIG. 1Eis in a vertical direction and illustrates the horseshoe shape of cross-section of the body portion104when the section is cut close to the distal end122. In contrast,FIG. 1Fis a partial perspective section view where the body portion104has been cut at a point between the distal end122and a midsection point124(seeFIG. 1B). The cut inFIG. 1Fis in a vertical direction and illustrates a substantial thickening of the horseshoe shape of cross-section of the body portion104of the anchor100.

FIG. 1Gis a partial perspective view where the body portion104has been cut at the midsection point124(seeFIG. 1B). The cut inFIG. 1Gis in a vertical direction and illustrates a cross-sectional shape of a solid partially elliptical segment. As illustrated, the body portion104has a vertical thickness or height of h1at this cut point. In contrast,FIG. 1His a partial perspective view where the head portion102has been cut around a point126(seeFIG. 1B). As illustrated, the head portion102has a vertical thickness or height of h2at this cut point. Note the difference in between the height h1inFIG. 1Gand the height h2inFIG. 1His created by the offset portion114of the head portion102as discussed above.

Although the anchor100as illustrated and discussed above uses a tapering horseshoe cross-sectional shape for the body portion104, any cross-sectional shape could be used and still be within the inventive aspects of the present invention. Such shapes include triangular, diamond, rectangular, circular or equilateral polygon cross-sectional shapes or a combination thereof. For instance, a triangular cross-sectional shape could be used on the body portion104while the head portion102may be largely circular in cross-sectional shape. If such shapes are used, generally the body portion will taper down from the head portion102to the distal end122. In other words, the cross sectional areas of the body portion104will decrease as the distal end is approached.

In certain embodiments, the anchors discussed above may be fabricated from any number of biocompatible implantable materials, including but not limited to Titanium Alloys (Ti 6AI4V ELI, for example), commercially pure titanium, Chromium Cobalt (Cr—Co) and/or stainless steels. In yet other embodiments, the anchors may also be manufactured from polymer, including Carbon Fiber Reinforced Polymer (“CFRP”) with a high carbon mass percentage. Furthermore in some embodiments, as explained below, the anchors may be formed using a shape memory alloy, such as Nitinol®.

An Embodiment of an Implant

FIG. 2Ais an isometric illustration of a supra bone implant or supra implant (also known in the art as a fixation plate, insert plate, or insert).FIG. 2Bis a top view of the supra implant200andFIG. 2Cis a sectional perspective view of the supra implant200. The implants disclosed herein, such as supra implant200, may be manufactured from any number of implant grade materials, including, but not limited to Titanium and Titanium Alloys, as well as Carbon Fiber Reinforced Polymer (CFRP) and shape memory alloys as explained below.

In the illustrated embodiment ofFIGS. 2A, 2B and 2C, the supra implant200has an elongated main body portion202with end portions204aand204bon each side of the main body portion. In certain embodiments, the main body portion202and the end portions204aand204bare all aligned along a longitudinal axis201(FIG. 2B). The supra implant200has a proximal surface206and a distal surface208for engaging or for placement next to one or more boney structures.

In certain embodiments, the end portions204aand204bhave apertures210aand210bdefined therethrough for accepting a non-threaded anchor, such as anchor100described above. In certain embodiments, the apertures210aand210bhave curved engaging surfaces212aand212bdefined therein which are sized to receive and engage a surface of the non-threaded anchor100. In certain embodiments, the interaction of the inwardly sloped engaging surfaces212aand212bwith the longitudinal shape or geometry of the elongated body portion104of non-threaded anchor100defines an initial insertion trajectory for the non-threaded anchor. For purposes of this disclosure the “initial trajectory” is the path of movement of the elongated body portion104of an anchor100starting when the elongated body portion104is first introduced into the aperture (e.g. either aperture210aor210bofFIG. 3A) and ending when the head portion102of the anchor100first comes into contact with the engaging surfaces212aand212bforming a portion of the inside of the aperture (seeFIG. 3Cbelow).

A Method of Use:

FIGS. 3A through 3Edemonstrate a method of using at least two anchors100aand100bwith the supra implant200to compress two boney structures250aand250btogether. For purposes of this disclosure, a boney structure many be an entire human bone or a portion of a bone that has been fragmented or otherwise separated.FIGS. 3A through 3Eare cross-sectional views of the implant200, the boney structures250aand250b, and two anchors100aand100bshowing different stages of interaction between these elements. Anchors100aand100bare similar to anchor100discussed above with the subscribe reference letters added to distinguish the anchors from one another. For brevity and clarity, a description of those parts which are identical or similar to those described in connection with the implant200or the anchor100will not be repeated here.

InFIG. 3A, the implant200is positioned adjacent to the boney structure250aand the second boney structure250b. For purposes of explaining the illustrated embodiment, a gap224(not drawn to scale) is illustrated between the boney structure250aand the boney structure250b. Additionally, for purposes of illustration, an initial trajectory of elongated body portion104aof anchor100acan be visualized as arrow216a. Similarly, an initial trajectory of elongated body portion104bof anchor100bcan be visualized as arrow216b. InFIG. 3A, a distal end122aof the non-threaded elongated body portion104ais illustrated as having been introduced into the aperture210a. Similarly, a distal end122bof the non-threaded elongated body portion104bis illustrated as having been introduced into the aperture210b.

FIG. 3Billustrates the system and boney structures ofFIG. 3A, but with the elongated body portions104aand104bdriven partially into the boney structures250aand250b, respectively. In certain embodiments, a smooth non-torsional force may be applied onto the proximal end116aof the head portion102ato drive the elongated body portion104athrough the aperture210aand into the boney structure250aalong the trajectory illustrated as arrow216a. Additionally, a smooth non-torsional force may be applied onto the proximal end116bof the head portion102bto drive the elongated body portion104bthrough the aperture210band into the boney structure250balong the trajectory illustrated as arrow216b. In certain embodiments this non-torsional force may be a “smooth” non-torsional force as opposed to a series of impact forces. In yet other embodiments, an impact force or a rotating force may be applied to drive the elongated body portions104aand104binto the boney structures250aand250b, respectively.

Similarly,FIG. 3Cillustrates the system and boney structures ofFIG. 3B, but with the elongated body portions104aand104bdriven farther into the boney structures250aand250b, respectively. As can be seen inFIG. 3C, the elongated body portions104aand104bhave been almost completely driven through the apertures210aand210b, respectively and each elongated body portion104aand104bare still following their respective initial trajectories as represented by arrows216aand216b.

FIG. 3Calso illustrates the situation where the non-torsional force continues to be applied onto the proximal end116aas the transition surface117aof head portion102abegins to interact with the engaging surface212aof the aperture210a. The interaction between the engaging surface212aof the aperture210aand the transition surface117aof the head portion102aforces the head to in a direction that is generally transverse to the center axis106of the anchor100a(seeFIG. 1Babove). The transition surface117aallows for a smooth transition and kinematic transverse movement. The direction of this transverse movement is represented by the arrow218a. The transverse movement of the head portion102aalso causes movement of the elongated body portion104a. Because the boney structure250ais now attached to the elongated body portion104a, the boney structure250ais also forced to move in the transverse direction represented by arrow218a. Thus, causing the boney structure250ato move closer to the boney structure250b.

Simultaneously, a second non-torsional force continues to be applied onto the proximal end116bas the transition surface117bof head portion102bbegins to interact with the engaging surface212bof the aperture210b. The interaction between the aperture210band the transition surface117bof the head portion102bforces the head to move in a direction that is generally transverse to the center axis106of the anchor100a(seeFIG. 1Babove). The direction of this transverse movement is represented by the arrow218bwhich is in a direction that is opposite from the direction represented by arrow218adiscussed above. The transverse movement of the head portion102balso causes movement of the elongated body portion104b. Because the boney structure250bis now attached to the elongated body portion104b, the boney structure250bis also forced to move in the transverse direction represented by arrow218b. Thus, causing the boney structure250bto move closer to the boney structure250b. Thus, the gap224narrows as the head portions102aand102bapproach their respective apertures210aand210b.

FIG. 3Dillustrates the situation where the non-torsional force continues to be applied onto the proximal end116aof the head portion102aas the first head portion is pushed farther into the first aperture210a. The interaction between the inwardly sloped surface212aof the aperture210aand the offset portion114aof the head portion102aforces the head portion to keep moving in the transverse direction ad indicated by arrow218a. As discussed above, the transverse movement of the head portion102aalso causes additional transverse movement of the elongated body portion104a, which causes the boney structure250ato also move in the direction of arrow218atowards the boney structure250b.

Simultaneously, a second non-torsional force continues to be applied onto the proximal end116bof the head portion102bas the head portion is pushed farther into the first aperture210a. The interaction between the inwardly sloped surface212bof the aperture210band the offset portion114bof the head portion102bforces the head portion to keep moving in the transverse direction as indicated by arrow218b. As discussed above, the transverse movement of the head portion102balso causes additional transverse movement of the elongated body portion104a, which causes the boney structure250bto also move in the direction of arrow218aand towards the boney structure250a. The relative movement between the boney structure250aand the boney structure250bcauses the gap224to significantly narrow.

FIG. 3Eillustrates the situation where the head portion102ahas been pushed completely into the aperture210a. As explained above, the interaction between the inwardly sloped surface212aof the aperture210aand the offset portion114aof the head portion102ahas forced the head portion to continue to move transversely in the direction of the arrow218a. The transverse movement of the head portion102aalso cause transverse movement of the elongated body portion104a, which caused the boney structure250ato compress against the boney structure250b.

Similarly, the head portion102bhas been pushed completely into the aperture210b. As explained above, the interaction between the inwardly sloped surface212bof the aperture210band the offset portion114bof the head portion102bhas forced the head portion to move transversely in the direction of the arrow218b. The transverse movement of the head portion102balso caused the transverse movement of the elongated body portion104b, which caused the boney structure250bto compress against the boney structure250a. The gap224is now closed as the boney structure250ais pressed against the boney structure250b. The magnitude or height of the offset of the anchor head portions102a-102band the angle of slope of the engagement surfaces212aand212bdetermine the amount of compression achieved.

In certain embodiments, the oversized geometry of the offset portion114causes a light press fit between the anchor head portion114and an aperture of an implant. Thus, in some embodiments, the offset portion114may be an oversized geometric volume which contacts a surface of the aperture of an implant. These are cylindrical surfaces which will largely be concentric in the final position, and in the offset portion114they may have an incrementally larger radius than the underside of the surface in the aperture resulting in being wedged together in the final position—which assists in preventing the anchor from “backing out” of the respective aperture. In yet other embodiments, other anti-back methods and techniques may also be employed, such as blocker plates, retaining rings, and locking screws.

OTHER EMBODIMENTS

For purposes of simplification, the implant embodiments discussed above have illustrated and described with an implant and two anchors. However, the present invention contemplates the use of implant embodiment systems using more than two anchors.

In alternative embodiments, one or more anchors may be a traditional anchor without an offset head portion. For instance inFIGS. 3A through 3E, the anchor100bmay be replaced with a traditional anchor (either threaded or non-threaded) having a symmetrical head portion. Similarly, the aperture210bmay be replaced with a traditional concentric aperture designed to accommodate a traditional anchor with a concentric or symmetrical head. In this alternative embodiment, the symmetrical head and concentric aperture would not cause a transverse shift as explained above. Consequently, significant compression due to movement would not occur on the side of the implant having a traditional anchor. For example inFIG. 3C, if the anchor100bis replaced with a traditional anchor and the aperture210bis replaced with a symmetrical aperture, then only the boney structure250awould move toward the boney structure250b. The boney structure250bwould remain relatively stationary in this alternative embodiment.

Although the above discussion focuses on compressing boney structures together or compressing a boney structure against an implant, the above anchors and methods could also be used to cause distraction between a first boney structure and a second boney structure via a modification of the anchors and implants. By reversing or flipping the head geometry (i.e. offset portions114) of the anchors100a-100band reversing or flipping the engagement surfaces and geometries of the respective apertures210a-210bof the implants200, distraction of boney structures can be achieved by using the methods described above.

While the above example uses anchors100with the two aperture implants200, implants may have two, four, six or more apertures and the corresponding number of anchors and still be within the scope of this invention.

For instance,FIG. 4depicts a perspective view of a six anchor implant400joining a divided and re-aligned sternum450. The implant400and the associated six anchors fixes and holds the sternum450together following a cardiac procedure.

In yet other embodiments, various components, for example the anchors100may be made from nickel titanium (also known as Nitinol®) or another shape memory alloy. The anchor would have a very specific shape at a cooler temperature, such as room temperature. Once inserted into a human body, the metal would rise to a body temperature which will cause the anchor to change shape to enhance compression.

For instance, at or below room temperature a straight anchor might be inserted. At body temperature, the straight anchor turns into a curved anchor and applies additional compression or distraction. Similarly, a curved anchor could turn into a straight anchor at body temperature to enhance either compression or distraction.

In yet other embodiments, the implant or parts of the implant may be formed of a shape memory alloy. For example inFIG. 4, the joining members402aand402bmay be made of Nitinol® and be straight at a cooler temperature, such as room temperature. Once inserted into a human body and the surgical procedure completed, the temperature of the joining members402aand402bwould rise to a body temperature which will cause the joining members to curve. As joining members402a-402bcurve (either inwards or outwards), the joining members will begin to pull on the rest of the implant, which will cause additional compression.

The abstract of the disclosure is provided for the sole reason of complying with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many combinations, modifications and variations are possible in light of the above teaching. For instance, in certain embodiments, each of the above described components and features may be individually or sequentially combined with other components or features and still be within the scope of the present invention. Undescribed embodiments which have interchanged components are still within the scope of the present invention. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims.