Patent Description:
A fusion bone plate implant may be utilized in conjunction with one or more fasteners so as to generate compression and stability at a bone interface. An implant coupled with fasteners generally serves to stabilize bones, or bone parts, relative to one another so as to promote bone fusion. In many applications, bone plates and fasteners are used to fuse bones, or bone parts, of the human body, such as bones in the foot, the ankle, the hand, the wrist, as well as various other portions of the body. Furthermore, during the course of certain medical procedures, a surgeon may immobilize one or more bones or the bone fragments by stabilizing the bones together in a configuration which approximates the natural anatomy. To this end, the surgeon may use fasteners to attach the bones to a bone plate implant so as to hold the bones in alignment with one another while they fuse together.

In some instances, however, a bone plate may be impractical for implantation in a portion of the body that requires treatment. What is needed, therefore, is a compression bone screw that is configured to fuse bones in absence of a fusion bone plate.

A bone screw is disclosed in <CIT>. Document <CIT> discloses a bone screw according to the preamble of claim <NUM>.

A compression bone screw is provided as defined by claim <NUM>.

The drawings refer to embodiments of the present disclosure in which:.

While the present disclosure is subject to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. The invention should be understood to not be limited to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, and alternatives falling within the scope of the invention as defined by the claims.

It will be apparent, however, to one of ordinary skill in the art that the invention disclosed herein may be practiced without these specific details. In other instances, specific numeric references such as "first screw," may be made. However, the specific numeric reference should not be interpreted as a literal sequential order but rather interpreted that the "first screw" is different than a "second screw. " Thus, the specific details set forth are merely exemplary. The specific details may be varied from and still be contemplated to be within the scope of the invention as claimed. The term "coupled" is defined as meaning connected either directly to the component or indirectly to the component through another component. Further, as used herein, the terms "about," "approximately," or "substantially" for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein.

In general, the present disclosure describes an apparatus and a method for a differential compression bone screw for compressing two adjacent bone portions together, including compressing bone fractures, fixating osteotomies, and joining fusions. The compression bone screw is comprised of a head portion and a distally extending shank. A center hole extends from the head portion to a distal end of the shank. The head portion is comprised of a superior end and an inferior end. The superior end includes a shaped opening that is substantially concentric with the center hole and configured to engagedly receive a tool for driving the compression bone screw into a hole drilled in a patient's bone. The inferior end includes a plurality of barbs that are disposed around the circumference of the inferior end and are configured to fixedly engage with surrounding bone tissue. Proximal threads and distal threads are disposed on the shank and configured to rotatably engage within the hole in the patient's bone, such that the compression bone screw advances into the hole upon being turned by way of the tool. A thread pitch of the distal threads preferably is greater than a thread pitch of the proximal threads, such that the compression bone screw comprises a differential pitch configured to compress the two adjacent bone portions, thereby closing a fracture there between.

<FIG> illustrate an exemplary embodiment of a compression bone screw <NUM> that may be used for repairing bone fractures, fixating osteotomies, joining fusions of the skeletal system, and the like. It should be understood that the terms "bone screw," "fastener," "fixator," "elongate member," and "screw" may be used interchangeably herein as they essentially describe the same type of device. The compression bone screw <NUM> generally is an elongate member comprised of a head portion <NUM> and a shank <NUM>. As best shown in <FIG>, a cannulation or center hole <NUM> extends longitudinally from the head portion <NUM> to a distal end <NUM> of the shank <NUM>. The center hole <NUM> is configured to receive any of various guidewires, trocars, and other similar instruments for directing the bone screw to a hole drilled in the patient's bone,.

The head portion <NUM> is comprised of a superior end <NUM> and an inferior end <NUM>. As best illustrated in <FIG>, the superior end <NUM> may include a shaped opening <NUM> that is substantially concentric with the center hole <NUM>. The shaped opening <NUM> generally is configured to engagedly receive a tool suitable for driving the bone screw <NUM> into the hole drilled in the patient's bone. Although in the illustrated embodiment, the shaped opening <NUM> is comprised of a hexalobe shape, any of various multi-lobe shapes, as well as other polygonal shapes, are also contemplated.

The inferior end <NUM> preferably is configured to countersink within the hole in the bone. Thus, the superior end <NUM> is not left protruding above the exterior surface of the bone once the compression bone screw <NUM> is fully engaged with the patient's bone. Further, a plurality of barbs <NUM> disposed around the circumference of the inferior end <NUM> are configured to engage with the surrounding bone tissue so as to prevent the bone screw from backing out of the hole in the patient's bone. In some embodiments, however, the inferior end <NUM> may be configured to be received within an opening of a bone fusion plate, such that the superior end <NUM> countersinks within the opening of the bone fusion plate and presses the plate against the surface of the patient's bone.

As best shown in <FIG>, the shank <NUM> is comprised of proximal threads <NUM> and distal threads <NUM> that share an intervening smooth portion <NUM>. The proximal threads <NUM> have a diameter <NUM>, and the distal threads <NUM> have a diameter <NUM>. A tapered diameter <NUM> extends from the distal threads <NUM> to a rounded portion <NUM> that comprises the distal end <NUM>. The smooth portion <NUM> is comprised of a diameter <NUM> that is less than the diameters <NUM> and <NUM> so as to facilitate passing the smooth portion <NUM> through the bone with relatively little resistance. Further, in the illustrated embodiment, the threads <NUM> and <NUM> share substantially similar exterior diameters, <NUM> and <NUM>, respectively, as shown in <FIG>. In some embodiments, however, the diameter <NUM> of the proximal threads <NUM> may be greater than the diameter <NUM> of the distal threads <NUM>. Various diameters of the proximal threads <NUM> and the distal threads <NUM>, as well as the diameter <NUM>, are contemplated, without limitation.

The threads <NUM> and <NUM> are configured to rotatably engage within a suitably sized hole drilled in the patient's bone. Thus, turning the bone screw <NUM> in an appropriate direction by way of a tool coupled with the shaped opening <NUM>, drives the distal threads <NUM> to engage with bone tissue surrounding the hole, and thus advancing the bone screw <NUM> deeper into the hole in the bone. The proximal threads <NUM> engage the bone once a majority of the bone screw <NUM> is already disposed within the hole in the bone. Continued turning of the bone screw <NUM> then countersinks the inferior end <NUM> into an upper-most portion of the hole in the bone, and draws the superior end <NUM> beneath the exterior surface of the patient's bone.

Moreover, the illustrated embodiment of the compression bone screw <NUM> comprises a differential pitch wherein the distal threads <NUM> have a thread pitch that is greater than the thread pitch of the proximal threads <NUM>. In operation, the greater thread pitch of the distal threads <NUM> pushes the bone portion near the distal threads toward the bone portion near the proximal threads <NUM>. The diameter <NUM> of the smooth portion <NUM> allows the fracture to close as the bone portions are compressed together. In some embodiments, the thread pitch of the distal threads <NUM> may range between substantially <NUM>-<NUM> times greater than the thread pitch of the proximal threads <NUM>. Preferably, however, the thread pitch of the distal threads <NUM> is substantially <NUM>-times greater than the thread pitch of the proximal threads <NUM>. A wide variety of differential pitch configurations are contemplated within the scope of the present disclosure.

It is contemplated that the differential pitch of the compression bone screw <NUM> is particularly well suited for compressing bone fractures, fixating osteotomies, joining fusions, as well as any other surgical procedure wherein compressing two adjacent bone portions is desired, without limitation. It is further contemplated that the compression bone screw <NUM> may be advantageously oriented longitudinally with respect to a patient's bone. <FIG> illustrates an exemplary use environment <NUM> wherein the compression bone screw <NUM> is longitudinally disposed within substantially the center of a repaired bone <NUM>. The proximal threads <NUM> and the distal threads <NUM> are engaged with healthy bone tissue, while a repaired fracture <NUM> is disposed along the smooth portion <NUM>. Further, the head portion <NUM> is countersunk within an entry hole <NUM> that was drilled into the repaired bone <NUM> by a surgeon. As will be appreciated, the compression bone screw <NUM> may be implemented in any of various lengths and diameters so as to advantageously repair a wide variety of differently sized and shaped bones within the human body. Furthermore, it is envisioned that the compression bone screw <NUM> may be configured for use in a veterinary capacity, and thus the bone screw <NUM> may be implemented with various shapes and sizes that are suitable for use in different types of animals.

As will be appreciated, the rounded portion <NUM> and the tapered diameter <NUM> are configured to minimize resistance to forward movement of the compression bone screw <NUM> advancing within the interior of a bone hole. As best shown in <FIG>, the distal end <NUM> and the tapered diameter <NUM> of the bone screw <NUM> are further comprised of one or more flutes <NUM> that extend from adjacent of the center hole <NUM> and spiral along the tapered diameter <NUM>. A pair of cutting edges <NUM> borders each of the flutes <NUM>. Although the illustrated embodiment of the bone screw <NUM> comprises three flutes <NUM>, and thus six cutting edges <NUM>, more than or less than three flutes <NUM> and six cutting edges <NUM> may be incorporated into different implementations of the bone screw <NUM> without limitation. As will be appreciated, the cutting edges <NUM> advantageously clean the interior of the bone hole and increase the diameter of the hole to accept the distal threads <NUM> of the advancing bone screw <NUM>. As will be appreciated, the spiral, or a rate of twist, of the flutes <NUM> generally controls the rate of bone debris removal from the interior of the bone hole during rotation of the bone screw <NUM>. It is contemplated that the flutes <NUM> may be implemented with any of various spirals without deviating beyond the scope of the claims.

<FIG> illustrate an exemplary embodiment of a compression bone screw <NUM> that may be used for repairing bones of a patient. The compression bone screw <NUM> is substantially similar to the compression bone screw <NUM>, illustrated in <FIG>, with the exception that the compression bone screw <NUM> is comprised of intermediate threads <NUM> in lieu of the smooth portion <NUM>. As best shown in <FIG>, the intermediate threads <NUM> extend from the distal threads <NUM> to the proximal threads <NUM>, such that a continuous series of threads are disposed along substantially an entirety of the shank <NUM>. Further, a tapered diameter <NUM> extends from the distal threads <NUM> to the distal end <NUM>. The tapered diameter <NUM> and the distal end <NUM> are configured to minimize resistance to forward movement of the compression bone screw <NUM> advancing within the interior of a bone hole. It is contemplated that, in some embodiments, the tapered diameter <NUM> may be further comprised of one or more flutes <NUM> and cutting edges <NUM> that extend from the distal end <NUM> to the distal threads <NUM>, as described herein.

The intermediate threads <NUM> may have a thread pitch that generally changes along the length of the shank <NUM>. In the illustrated embodiment of <FIG>, the intermediate threads <NUM> have a thread pitch that continuously decreases from the thread pitch of the distal threads <NUM> to the relatively smaller thread pitch of the proximal threads <NUM>. In some embodiments, the intermediate threads <NUM> may be comprised of a thread pitch near the distal threads <NUM> that ranges between substantially <NUM>-<NUM> times greater than the thread pitch of the intermediate threads that are near the proximal threads <NUM>. In some embodiments, the intermediate threads <NUM> may be comprised of a thread pitch near the distal threads <NUM> that decreases from substantially <NUM>-times greater than the thread pitch near the proximal threads <NUM>. During operation of the compression bone screw <NUM>, the greater thread pitch of the distal threads <NUM> and nearby intermediate threads <NUM> pushes the bone portion near the distal threads toward the bone portion near the proximal threads <NUM>. As will be appreciated, during operation of the compression bone screw <NUM>, the decreasing thread pitch of the intermediate threads <NUM> contributes to compressing the bone portion near the distal threads <NUM> toward the bone portion near the proximal threads <NUM>. A wide variety of differential pitch configurations are contemplated within the scope of the present disclosure.

Moreover, in some embodiments, wherein the proximal threads <NUM> have a larger diameter than the distal threads <NUM>, the intermediate threads <NUM> may be comprised of a diameter that continuously increases from the diameter of the distal threads <NUM> to the diameter of the proximal threads <NUM>. In some embodiments, the intermediate threads <NUM> may have a diameter that is larger than the diameter of the distal threads <NUM> and is smaller than the diameter of the proximal threads <NUM>. In still some embodiments, the diameter of the intermediate threads <NUM> may be substantially the same as the diameter of the distal threads <NUM> along a majority of the intermediate threads and then abruptly increase to match the diameter of the proximal threads <NUM>. It should be understood, therefore, that a wide variety of relationships between the shapes and sizes of the distal threads <NUM>, the intermediate threads <NUM>, and the proximal threads <NUM> are contemplate and may be implemented within the scope of the claims.

Claim 1:
A compression bone screw for compressing adjacent bone portions together, comprising:
a head portion (<NUM>) comprised of a superior end (<NUM>) and an inferior end (<NUM>);
a shank (<NUM>) extending distally from the inferior end to a distal end (<NUM>); and
proximal threads (<NUM>) and distal threads (<NUM>) disposed along the shank, the proximal threads comprised of a first thread pitch and the distal threads comprised of a second thread pitch, such that the shank comprises a differential pitch; wherein
the superior end includes a shaped opening (<NUM>) that is substantially concentric with the head portion and configured to engagedly receive a tool for driving the compression bone screw into the hole drilled in the bone, and wherein the inferior end comprises a plurality of barbs disposed around the circumference of the inferior end and configured to fixedly engage with surrounding bone tissue; and wherein the shaped opening (<NUM>) comprises a multi-lobe shape;
wherein a center hole (<NUM>) extends from the head portion to the distal end and is configured to receive any of various guidewires, trocars, and other similar instruments configured to direct the compression bone screw to a target opening of a hole drilled in a bone;
characterised in that:
a tapered diameter (<NUM>) extends from the distal threads (<NUM>) to a rounded portion (<NUM>) that comprises the distal end; and in that the distal end (<NUM>) and the tapered diameter (<NUM>) of the bone screw (<NUM>) are further comprised of one or more flutes (<NUM>) that extend from adjacent of the center hole (<NUM>) and spiral along the tapered diameter (<NUM>); wherein a pair of cutting edges (<NUM>) borders each of the flutes (<NUM>).