Patent Description:
A broken bone must be carefully stabilized and supported until it is strong enough to handle the body's weight and movement. Until the last century, physicians relied on casts and splints to support and stabilize the bone from outside the body. The advent of sterile surgical procedures reduced the risk of infection, allowing doctors to internally set and stabilize fractured bones. During a surgical procedure to set a fracture, the bone fragments are first repositioned (reduced) into their normal alignment. They are held together with special implants, such as plates, screws, nails and wires.

Screws are used for internal fixation more often than any other type of implant. Although the screw is a simple device, there are different designs based on the type of fracture and how the screw will be used. Screws come in different sizes for use with bones of different sizes. Screws can be used alone to hold a fracture, as well as with plates, rods, or nails. After the bone heals, screws may be either left in place or removed.

In many instances, it is desired that the inserted screw provide compression at the bone joint or fracture line to reduce the incidence of nonunion (improper healing) and malunion (healing in improper position) of broken bones.

<CIT> describes a variable length headless compression screw insertion system comprising:.

To meet this and other needs, systems for fixating bone are provided. In particular, bone screws are provided that apply compression to bone fragments or bone portions (for example, fixation of fractures or fusion of joints), are self-tapping and/or self-drilling, minimize or prevent screw toggle and/or back-out, remove bone build-up (for example, from cutting flutes), and the like.

According to the invention it is provided a variable length headless compression screw insertion system having the features outlined in claim <NUM>. Further advantageous aspects of the invention are set forth in the dependent claims.

According to the invention, a variable length headless compression screw insertion system includes a compression screw and a driver assembly for driving the compression screw into a bone. The compression screw has a bone screw and a compression sleeve coupled to the bone screw. The bone screw includes a proximal end having an external threading threadably received in the compression sleeve, and the compression sleeve includes a proximal end having a predefined drive feature and an external threading. The driver assembly includes a sleeve coupler adapted to threadably receive the external threading of the compression sleeve. A ram driver is coupled to the sleeve coupler and has a predetermined length such that its distal end is shaped to contact the proximal end of the bone screw to prevent translation of the bone screw relative to the compression sleeve. The driver assembly further comprises a sleeve driver adapted to be coupled to the sleeve coupler and having a predetermined length such that its distal end has a complementary drive feature that mates with the predefined drive feature of the compression sleeve, the sleeve driver adapted to rotate the compression sleeve relative to the sleeve coupler. The compression sleeve further includes a shaft having a first outer diameter and a drill tip extending from the shaft and having a second outer diameter larger than the first diameter.

The accompanying drawings, which are incorporated herein and constitute part of this specification, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings:.

In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. It should be understood, based on this disclosure, that the invention is not limited by the embodiments described herein, but by the appended claims.

Referring to <FIG> and <FIG>, a compression screw <NUM> in accordance with an embodiment will be described. The compression screw <NUM> generally comprises a bone screw <NUM> and a compression sleeve <NUM>. The bone screw <NUM> and the compression sleeve <NUM> may be constructed from any biocompatible material including, but not limited to, stainless steel alloys, titanium, titanium based alloys, or polymeric materials.

The bone screw <NUM> includes a shaft <NUM> extending from a distal end <NUM> to a proximal end <NUM>. Referring to <FIG> and <FIG>, in the illustrated embodiment, a cannula <NUM> extends from the distal end <NUM> to the proximal end <NUM> such that a guide wire may be used for positioning the compression screw <NUM>. A drive feature <NUM> is defined in the proximal end <NUM> of the shaft <NUM> and is configured and dimensioned to be any shape that corresponds with the end of the driving instrument designed to engage the bone screw <NUM>. As an example, in the illustrated embodiment, the drive feature <NUM> has a hexalobular configuration.

A series of bone engaging threads <NUM> extend radially from the shaft <NUM> at the distal end <NUM> and a series of sleeve engaging threads <NUM> extend radially from the shaft <NUM> at the proximal end <NUM>. In the preferred embodiment, the bone engaging threads <NUM> are dual lead thread type and the sleeve engaging threads <NUM> are a standard machine thread. However, any type of thread for either thread series <NUM>, <NUM> may be used to facilitate the function of the compression screw <NUM>. The bone screw <NUM> preferably also includes at least one cutting flute <NUM> configured to cut into the bone as the bone screw <NUM> is rotated, defining a self-drilling and self-tapping tip. In a preferred embodiment, a slot <NUM> is associated with each cutting flute <NUM> to clear any chips, dust, or debris generated when the compression screw <NUM> is implanted into bone tissue.

The compression sleeve <NUM> includes a tubular body <NUM> extending from a distal end <NUM> to a proximal end <NUM> with an internal passage <NUM> therethrough. The compression sleeve <NUM> includes a series of internal threads <NUM> (see <FIG>) configured to engage the sleeve engaging threads <NUM> of the bone screw <NUM> such that the bone screw <NUM> and the compression sleeve <NUM> are threadably adjustable to one another. The proximal end <NUM> of the compression sleeve <NUM> defines a radially extending head <NUM> which defines a shoulder <NUM> between the tubular body <NUM> and the head <NUM>. A drive feature <NUM> is defined in the head <NUM> of the compression sleeve <NUM> and is configured and dimensioned to be any shape that corresponds with the end of the driving instrument designed to engage the compression sleeve <NUM>. As an example, in the illustrated embodiment, the drive feature <NUM> has a hexalobular configuration.

As will be described in more detail hereinafter, during insertion of the implant, both drive features <NUM>, <NUM> are engaged such that the compression screw <NUM> maintains its full length. After the tip of the bone screw <NUM> is at the desired depth, only the drive feature <NUM> in the compression sleeve <NUM> is actuated. Since the two components are connected via threads, actuation of only the compression sleeve <NUM> will act to move the compression sleeve <NUM> distally toward the tip of the bone screw <NUM>, which shortens the length of the compression screw <NUM> and compresses the bone when the shoulder <NUM> of the compression sleeve <NUM> is on the near cortex.

To facilitate such shortening of the compression screw <NUM>, the distal end <NUM> of the compression sleeve <NUM> is provided with one or more cutting flutes <NUM> configured to cut into the bone as the compression sleeve <NUM> is rotated. The cutting flutes <NUM> simplify the procedure by removing material without the necessity of drilling to the outer diameter of the compression sleeve tubular body <NUM>. This also allows the compression screw <NUM> to be adjusted to any length without the need to predrill to a desired depth to accommodate the compression sleeve <NUM>. In the present embodiment, the cutting flutes <NUM> define a proximal rotary cutting structure.

In the alternative embodiment of the compression sleeve <NUM>' illustrated in <FIG>, a slot <NUM> is associated with each cutting flute <NUM>, with each slot recessed into the surface of the tubular body <NUM> and configured to guide the aforementioned cut bone into the slots <NUM>. The mechanism of action for this technology relies on first the cutting flutes <NUM> to remove material from the substrate that it is being inserted into. This material then follows through the path of the slots <NUM> by one of two mechanisms: (<NUM>) path of least resistance (the material has nowhere else to go) or (<NUM>) the trajectory of the slots <NUM> roughly follows the pitch of the cutting flutes <NUM> as it is advanced into the bone, and thus the cutaway material stays close to its original position as the screw advances axially via the screw's helix.

The slots <NUM> serve two functions: (<NUM>) the cut bone that follows the slots <NUM> acts to enhance the fit between the native bone and the component being inserted into the bone and (<NUM>) allows for bony ingrowth to prevent dislodging of the compression screw <NUM>. The cutting flutes <NUM> act to remove bone and guide said removed bone into the slots <NUM>. This is in effect a self-grafting feature of the compression sleeve <NUM> which enhances purchase. Surgeons will sometimes remove bone and pack it back into the implant to enhance purchase, however, this configuration on the compression sleeve <NUM> does that for them. Enhanced purchase acts to prevent screw toggle and screw axial motion. Even if the slots <NUM> are not filled with bone, they can act to prevent both screw toggle and screw axial motion by providing a surface to catch on the native bone. Additionally, the slots <NUM> provide a surface for bony ingrowth which can also prevent screw toggle and screw axial motion.

While the trajectory of the slots <NUM> is shown in the embodiment of <FIG> to roughly follow the pitch of the cutting flutes <NUM>, the slots may have other configurations. For example, in the compression sleeve <NUM>" illustrated in <FIG>, the slot <NUM>' has a steeper trajectory than the pitch of the cutting flutes. <FIG> illustrates another embodiment of the compression sleeve <NUM>‴ wherein the slot <NUM>" has an even steeper trajectory, being substantially parallel to the axis of the compression sleeve <NUM>‴. In addition to having different trajectories, the slots <NUM>, <NUM>', <NUM>" may have different pitches resulting in the slots being spaced closer together or further apart. Additionally, the slots <NUM>, <NUM>', <NUM>" may have different configurations, for example, semicircular, semi-oval, v-shaped, square, rectangular or the like. Furthermore, while the combination of cutting flutes <NUM> and slots <NUM>, <NUM>', <NUM>" are illustrated in conjunction with the compression sleeve <NUM>, it is recognized that such can be applied to a surface of any type of component that is being inserted into bone.

Having generally described the compression screw <NUM>, an exemplary driver assembly <NUM> for inserting the compression screw <NUM> and an exemplary method of insertion will be described with reference to <FIG> and <FIG>. The insertion method is not part of the scope of the invention.

The driver assembly <NUM> has a bone screw driver <NUM> and a compression sleeve driver <NUM>. The bone screw driver <NUM> includes a driver shaft <NUM> extending from a distal end <NUM> to a proximal end <NUM>. A driver tip <NUM> is defined on the distal end <NUM> of the driver shaft <NUM> and is configured to engage the driver feature <NUM> of the bone screw <NUM>. A connection key <NUM> is defined on the proximal end <NUM> of the driver shaft <NUM> and is configured to facilitate connection of the bone screw driver <NUM> to a manual or powered rotation device or a locking device which prevents rotation (not shown). A series of axial splines <NUM> extend radially from the driver shaft <NUM> and are configured to be selectively engaged by a connector switch <NUM> of the compression sleeve driver <NUM>, as will be described in more detail hereinafter. A series of external threads <NUM> extend from the driver shaft <NUM> distally of the splines <NUM>. The external threads <NUM> are configured to be selectively engaged by a thread engagement member <NUM> of the compression sleeve driver <NUM>, as will be described in more detail hereinafter.

The compression sleeve driver <NUM> extends from a distal end <NUM> to a proximal end <NUM>. The proximal end <NUM> is defined by a tubular body <NUM> with a driver tip <NUM> at the distal most end and an outward housing <NUM> proximally therefrom. The driver tip <NUM> is configured to engage the driver feature <NUM> of the compression sleeve <NUM>. The housing <NUM> defines a radial chamber in which the thread engagement member <NUM> is radially moveable. Upon depression of the thread engagement member <NUM>, internal threads thereof engage the external threads <NUM> of the driver shaft <NUM> such that the driver shaft <NUM> is caused to move axially with the compression sleeve driver <NUM> when they are rotated together as will be described.

A handle member <NUM> extends proximally from the housing <NUM> to the proximal end <NUM>. The connector switch <NUM> extends transversely through the handle member <NUM> and is moveable between a non-engaged position (see <FIG>) and an engaged position (see <FIG>). In the non-engaged position, an open area <NUM> of the connector switch <NUM> aligns with the splines <NUM> such that the switch <NUM> is not engaged with the splines <NUM> and the compression sleeve driver <NUM> rotates independent of the bone screw driver <NUM>. In the engaged position, a contact portion <NUM> of the connector switch <NUM> engages the splines <NUM> such that rotation of the compression sleeve driver <NUM> causes simultaneous rotation of the bone screw driver <NUM>.

To insert the compression screw <NUM>, the driver assembly <NUM> is positioned such that the driver tip <NUM> of the shaft <NUM> engages with the drive feature <NUM> of the bone screw <NUM> and the driver tip <NUM> of the tubular body <NUM> engages with the drive feature <NUM> of the compression sleeve <NUM>, as shown in <FIG>. During initial insertion, the connector switch <NUM> is moved to the engaged position such that the bone screw driver <NUM> and the compression sleeve driver <NUM> rotate together. The driver assembly <NUM> is rotated with both drivers <NUM>, <NUM> rotating and thus the compression screw <NUM> is advanced as a single unit until the distal end <NUM> of the bone screw <NUM> is at a desired location. The thread engagement member <NUM> may be depressed during such rotation to ensure that the shaft <NUM> advances axially during the simultaneous rotation. If the distal end <NUM> of the compression sleeve <NUM> contacts bone as the compression screw <NUM> is advanced, the proximal rotary cutting structure, i.e. the cutting flutes <NUM>, cut into the bone and the compression screw <NUM> is free to continue to advance as a single unit.

After the distal end <NUM> of the bone screw <NUM> has landed at the desired location, compression may be achieved by advancing the compression sleeve <NUM> while the bone screw <NUM> remains stationary. The bone screw <NUM> remains stationary by holding the bone screw driver <NUM> stationary, for example, by attaching a locking device to the connection key <NUM>, and by disengaging the connector switch <NUM>. With the connector switch <NUM> moved to the disengaged position, the compression sleeve driver <NUM> rotates freely about the bone screw driver <NUM>. Rotation of the compression sleeve driver <NUM> causes the compression sleeve <NUM> to advance. Since the bone screw <NUM> is stationary as the compression sleeve driver <NUM> advances the compression sleeve <NUM>, the compression screw <NUM> shortens in length and the shoulder <NUM> thus applies compression. Again, the cutting flutes <NUM> on the compression sleeve distal end <NUM> allow the compression sleeve <NUM> to cut into and advance into the bone.

Referring to <FIG>, a compression screw <NUM>' in accordance with another exemplary embodiment will be described. The compression screw <NUM>' is substantially the same as the previous embodiment except with the addition of a self-countersinking head <NUM>' on the compression sleeve <NUM>iv. The self-countersinking head <NUM>' has a tapered shoulder <NUM>' and a series of external threads <NUM>. The threads <NUM> are configured to be self-drilling and self-tapping. The self-countersinking head <NUM>' is advantageous in that the head does not protrude from the near cortex, which minimizes soft-tissue irritation and can reduce the reoperation rate. In the present embodiment, the cutting flutes <NUM> and the threads <NUM> each define a proximal rotary cutting structure. In all other aspects, the compression screw <NUM>' is the same as the previously described compression screw <NUM>.

Referring to <FIG>, a driver assembly <NUM>' and method for inserting the compression screw <NUM>' will be described, the method of insertion is not part of the scope of the invention. The driver assembly <NUM>' is substantially the same as in the previous embodiment except for the distal end <NUM>' of tubular body <NUM>' of the compression sleeve driver <NUM>'. Instead of a driver tip, the distal end <NUM>' defines an internally threaded chamber <NUM> which threadably engages the threads <NUM> of the self-countersinking head <NUM>'.

To insert the compression screw <NUM>', the driver assembly <NUM>' is positioned such that the driver tip <NUM> of the shaft <NUM> engages with the drive feature <NUM> of the bone screw <NUM> and the threads <NUM> of the self-countersinking head <NUM>' are threadably received in the threaded chamber <NUM> of the compression sleeve driver <NUM>', as shown in <FIG>. During initial insertion, the connector switch <NUM> is moved to the engaged position such that the bone screw driver <NUM> and the compression sleeve driver <NUM>' rotate together. The driver assembly <NUM>' is rotated with both drivers <NUM>, <NUM>' rotating and thus the compression screw <NUM>' is advanced as a single unit until the distal end <NUM> of the bone screw <NUM> is at a desired location. The thread engagement member <NUM> may be depressed during such rotation to ensure that the shaft <NUM> advances axially during the simultaneous rotation. If the distal end <NUM> of the compression sleeve <NUM>iv contacts bone as the compression screw <NUM>' is advanced, the cutting flutes <NUM> cut into the bone and the compression screw <NUM>' is free to continue to advance as a single unit.

After the distal end <NUM> of the bone screw <NUM> has landed at the desired location, compression may be achieved by advancing the compression sleeve <NUM>iv while the bone screw <NUM> remains stationary. The bone screw <NUM> remains stationary by holding the bone screw driver <NUM> stationary, for example, by attaching a locking device to the connection key <NUM>, and by disengaging the connector switch <NUM>. With the connector switch <NUM> moved to the disengaged position, the compression sleeve driver <NUM>' rotates freely about the bone screw driver <NUM>. Rotation of the compression sleeve driver <NUM>' causes the compression sleeve <NUM>iv to advance. Since the bone screw <NUM> is stationary as the compression sleeve driver <NUM>' advances the compression sleeve <NUM>iv, the compression screw <NUM>' shortens in length and the shoulder <NUM>' and distal end <NUM>' of the compression sleeve driver <NUM>' thus apply compression. Again, the cutting flutes <NUM> on the compression sleeve distal end <NUM> allow the compression sleeve <NUM> to cut into and advance into the bone.

After the desired amount of compression has been reached, the head <NUM>' may be countersunk. Countersinking is done by a third driver component (not shown) that mates with the compression sleeve driver feature <NUM>. For example, the driver assembly <NUM> may be exchanged for the driver assembly <NUM>' such that the driver tip <NUM> can be used to rotate the compression sleeve <NUM>iv while the bone screw <NUM> is maintained stationary. As the compression sleeve <NUM>iv advances over the bone screw <NUM>, the threads <NUM> cut into the bone and advance the head <NUM>' into a countersunk position within the bone.

Referring to <FIG>, a compression screw <NUM> in accordance with another embodiment will be described. The compression screw <NUM> includes a shaft <NUM> extending from a distal end <NUM> to a proximal end <NUM>. A series of bone engaging threads <NUM> extend radially from the shaft <NUM> at the distal end <NUM>. In the preferred embodiment, the bone engaging threads <NUM> are dual lead thread type, however, any type of thread may be used to facilitate the function of the compression screw <NUM>. The distal end <NUM> preferably also includes at least one cutting flute <NUM> configured to cut into the bone as the compression screw <NUM> is rotated, defining a self-drilling and self-tapping tip. In a preferred embodiment, a slot <NUM> is associated with each cutting flute <NUM> to clear any chips, dust, or debris generated when the compression screw <NUM> is implanted into bone tissue.

The proximal end <NUM> of the shaft <NUM> includes a self-countersinking head <NUM>. The self-countersinking head <NUM> has a tapered shoulder <NUM> and a series of external threads <NUM>. The threads <NUM> may include one or more cutting flutes <NUM> such that the threads <NUM> are self-drilling and self-tapping. In the present embodiment, the threads <NUM> define a proximal rotary cutting structure. A drive feature <NUM> is defined in the proximal end <NUM> of the shaft <NUM> and is configured and dimensioned to be any shape that corresponds with the end of the driving instrument designed to engage the compression screw <NUM>. As an example, in the illustrated embodiment, the drive feature <NUM> has a hexalobular configuration.

The shaft <NUM> between the bone engaging threads <NUM> and the head <NUM> is preferably free of threads. With this configuration, a difference in pitch between the bone engaging threads <NUM> and the threads <NUM> of the head <NUM> can provide additional compression control as the compression screw <NUM> is inserted. That is, if the pitch of the bone engaging threads <NUM> is larger than the pitch of the threads <NUM> of the head <NUM>, and the fracture or joint line lies somewhere in the shaft <NUM> section of the screw <NUM>, this configuration will provide compression between the two bones as the distal end <NUM> tries to advance faster than the head <NUM> of the screw <NUM>.

Referring to <FIG>, a driver assembly <NUM> which allows the surgeon to further control how much compression is achieved will be described. The driver assembly <NUM> includes an inner driver member <NUM> and an outer driver member <NUM>. The inner driver member <NUM> extends from a distal end <NUM> to a proximal end <NUM>. A driver tip <NUM> is defined on the distal end <NUM> and is configured to engage the driver feature <NUM> of the compression screw <NUM>.

The outer driver member <NUM> includes a tubular body extending from a distal end <NUM> to a proximal end <NUM>. The distal end <NUM> defines a threaded chamber <NUM> configured to threadeably receive the threads <NUM> of the compression screw head <NUM>.

To insert the compression screw <NUM>, the driver assembly <NUM> is positioned with the driver tip <NUM> engaged with the driver feature <NUM> and the threads <NUM> of the head <NUM> threadably received in the threaded chamber <NUM>. The inner and outer driver members <NUM>, <NUM> are rotated such that the compression screw <NUM> is advanced. As the compression screw <NUM> advances, the distal end <NUM> of the outer driver member <NUM> will hit the near cortex and compress the fracture line as the screw <NUM> is continued to be inserted.

After the desired amount of compression has been reached, the inner driver member <NUM> is rotated, independent of the outer driver member <NUM>, such that the compression screw <NUM> continues to advance with the outer driver member distal end <NUM> maintaining the compression. As the compression screw <NUM> advances, the threads <NUM> of the head <NUM> will enter the bone and begin to countersink the head <NUM>. As the head <NUM> advances and countersinks, it simultaneously threads out of the threaded chamber <NUM>. As explained before, the pitch of the bone engaging threads <NUM> and the threads <NUM> of the head <NUM> may be configured such that countersinking of the head <NUM> causes additional compression.

<FIG> is a cross-sectional view of a sleeve coupler attached to a compression screw and a ram driver according to an aspect of the present invention.

The VL (variable length) screw <NUM> of <FIG> is very similar to the VL screw <NUM> as shown in <FIG> and similar elements will have the same reference numbers. The screw <NUM> allows for continuously controlled compression during and after screw placement as well as the ability to control the final length of the screw during implantation. Once the VL screw <NUM> is placed, continuous compression of the bone fragments is controlled by a surgeon using the compression sleeve <NUM> and/or a driver as will be explained below in more detail.

As shown in <FIG>, the locking VL screw <NUM> functions by "locking" the bone screw <NUM> and compression sleeve <NUM> at a fixed length during insertion with a "ram" driver <NUM> that butts up against the back of the bone screw and prevents the rotation of the two screw components, thereby preventing translation of the bone screw into the compression sleeve. In other words, the ram driver <NUM> fixes the length or at least the minimum length of the compression screw <NUM>.

After the locked compression screw <NUM> is inserted to the appropriate position in the bone, the screw is then "unlocked" by removing the ram driver <NUM>. <FIG> shows the compression screw <NUM> in which the ram driver <NUM> has been removed to create the space <NUM> inside the compressions sleeve <NUM> and the compression sleeve can be advanced relative to the bone screw <NUM> to provide compression of the bone fragments. As the compression sleeve <NUM> is advanced, the proximal end <NUM> of the bone screw <NUM> translates proximally into the space <NUM> previously occupied by the ram driver <NUM> as shown in <FIG>. This solution reduces the overall size of the implant and simplifies the instrumentation used to insert the implant.

Also having external threads <NUM> on the compression sleeve <NUM> allows the compression sleeve to be buried below the surface of the bone to prevent irritation to the patient. The threads <NUM> gain purchase into the bone to prevent backout and maintain compression achieved by the screw <NUM>. Instead of the compression sleeve <NUM> being a buttress, an instrument used to insert the screw <NUM> has a flat bottom which compresses the bone fragments together.

<FIG> is a perspective view of a compression screw and a fully assembled driver assembly comprising a sleeve coupler and a ram driver. <FIG> is a perspective view of a ram driver. <FIG> is a perspective view of a sleeve driver.

The sleeve coupler <NUM> is similar to the sleeve driver <NUM> as shown in <FIG>. As such, only the different components will be discussed herein. The sleeve coupler <NUM> threadably receives the external threading <NUM> of the compression sleeve <NUM>. A button <NUM> is similar to the switch <NUM> of <FIG>. However, the button <NUM> is biased in a radial direction with a spring load. When the ram driver <NUM> is inserted into the sleeve coupler <NUM>, a conically shaped annular rib/retaining feature <NUM> on its shaft <NUM> mates with the button <NUM> and is automatically locked. A handle <NUM> inserted into the connection key <NUM> provides leverage when turning the compression locked screw <NUM>. Pushing of the button <NUM> disengages the lock and the ram driver <NUM> can then be removed from the sleeve coupler <NUM>.

In the embodiment shown in <FIG>, a distal surface of the shaft <NUM> is flat/planar without any mating or drive feature such that it only butts up against the proximal end of the bone screw <NUM> without mating with the bone screw. In the embodiment shown, the flat surface is perpendicular to the longitudinal axis of the shaft <NUM>.

<FIG> illustrates a countersink driver <NUM> that can be coupled to the sleeve coupler <NUM>. The countersink driver <NUM> has the same retaining feature/conical annular rib <NUM> on its shaft <NUM> as that <NUM> of the ram driver. The distal end of the shaft <NUM> has a drive feature <NUM> such as a hexalobular configuration which is complementary to the drive feature <NUM> of the compression sleeve <NUM>.

By relying on the ram driver <NUM> to lock the bone screw <NUM> and compression sleeve <NUM> together during insertion rather than a drive feature, the overall size and profile of the VL screw <NUM> can be significantly reduced to a desirable level. The present design also simplifies the instrumentation used to insert the implant.

It is described a method of implanting that it is not part of the scope of the invention. A method of implanting a compression screw has three main steps: (<NUM>) insertion, (<NUM>) compression and (<NUM>) countersink. In the insertion step, the ram driver <NUM> is inserted into and is locked to the sleeve coupler <NUM>. Then, the sleeve coupler <NUM> is threaded onto the compression sleeve <NUM> of the compression screw <NUM>. The bone screw <NUM> is then rotated until the proximal end makes contact with the distal end of the ram driver shaft <NUM>. The compression screw <NUM> is now ready for insertion into a bone. Clockwise turning of the handle <NUM> drives the locked compression screw <NUM> into the bone. When a desired depth has been reached, the insertion step is completed.

In the compression step, the compression sleeve <NUM> is translated relative to the bone screw <NUM> to shorten the overall length of the compression screw <NUM>. In the embodiment shown, a ram lock <NUM> is unlocked by sliding such that the ram shaft <NUM> is free to translate. Continued turning of the handle in the same direction rotates the compression sleeve <NUM> relative to the bone screw <NUM> which compresses fragmented bones together. Once final compression is achieved, the ram driver <NUM> is removed from the sleeve coupler <NUM>.

In an alternative compression method, not part of the invention, the ram driver <NUM> may be removed and then the sleeve coupler <NUM> may be turned clockwise to rotate the compression sleeve <NUM> relative to the bone screw <NUM>.

In the countersink step, after the final compression is achieved, the countersink driver <NUM> is inserted into the sleeve coupler until the retaining feature <NUM> travels past the lock <NUM>. The shaft <NUM> is dimension such that when the countersink driver <NUM> is locked, the drive feature <NUM> is mated with the complementary drive feature <NUM> of the compression sleeve <NUM>. Clockwise rotation of the handle <NUM> while holding the sleeve coupler <NUM> rotates and pushes the compression sleeve <NUM> into the bone. Once the distal end of the compression sleeve is at or below the bone surface, the sleeve coupler <NUM> and the locked countersink driver <NUM> are removed as a single unit.

<FIG> illustrates cross-sectional front view of a side loading washer according to one aspect of the present invention.

Washers are often used with headed screws to provide a greater surface area for contact when compressing a fracture with the head of a screw. However, they can also be used for headless screws such as the compression screw <NUM>. The larger surface spreads out the load over a greater surface area. A standard washer should be loaded onto the screw prior to insertion. If a washer is needed and was not assembled prior to insertion, the entire screw should be removed in order to assemble a washer onto the screw. This compromises the thread purchase and may result in the surgeon needing to move up to the next screw size to achieve fixation, adding operative time, frustration and ultimately, cost.

The side-loading retaining washer <NUM> can be assembled to the screw prior to or during insertion. The inner diameter W1 and slot of the washer is equal to or greater than the diameter of the mating screw shaft <NUM>. There are two small retention bumps <NUM> near the end of the slot. The distance between these two retention bumps is smaller than the diameter of the screw shaft.

These retention bumps <NUM> splay open when pressed onto the screw shaft <NUM> and then collapse once the washer has been assembled. Once assembled to the screw <NUM>, the washer <NUM> stays retained because the retention bumps <NUM> prevent disassembly as shown in <FIG>.

<FIG> is a perspective view of a headed screw <NUM> and the side-loading retaining washer <NUM> assembled on to the screw.

Instead of a standard closed washer that should be assembled to the screw prior to insertion, the side-loading washer can be assembled to the headed screw at any time during insertion. This improves intra-operative versatility and reduces the risk of compromising thread purchase during the procedure.

<FIG> is a perspective view of a jamming screw for locking the compression sleeve and bone screw according to another aspect of the present invention.

A jamming screw <NUM> is a small set screw that is inserted into the proximal end of the compression sleeve <NUM> and is bottomed out on the proximal end of the bone screw <NUM> post. This binds the two components of the compression screw <NUM> together to prevent disassembly. This jam screw <NUM> can have the same thread as the thread on the bone screw <NUM> post, a different pitch than the thread on the bone screw post, or a left-hand thread (vs. right-hand thread) to create this binding effect.

Adding a blind hole in the distal end of the compression sleeve <NUM> instead of a thru hole, paired with the jamming screw, limits the travel of the sleeve. The jamming screw <NUM> has a conventional drive feature and can be inserted and removed with a conventional screw driver having a complementary drive feature.

<FIG> is a perspective view of a jamming screw having a suture <NUM> going through a through hole (not shown) and side grooves that interrupt the threading of the screw (see <FIG> for a similar feature). The suture <NUM> can be tied down to the surrounding anatomy. The suture <NUM> may be useful for fixing loose ligaments near the injury.

<FIG> is a perspective view of a breakaway jam screw <NUM>. The breakaway jam screw <NUM> has a shaft <NUM>, proximal end having a drive feature <NUM> and a jam screw <NUM>. A breakaway region <NUM> is located just above the jam screw <NUM> and a distal end of the shaft <NUM>, and has the smallest cross-sectional area for the entire screw <NUM>.

By attaching the jam screw <NUM> to a larger protrusion, it will be easier to locate and use during surgery. There will be less concerns about losing the small jam screw <NUM> within the patient. The diameter of the breakaway region <NUM> is dimensioned in such a way that it always fails at a set torque value. This torque value is calculated using the polar moment of inertia. No undercut is necessary for the breakaway region because the jam screw is always contained within the sleeve once broken off. Having a breakaway region <NUM> allows the implant design to control the amount of torque applied to the jam screw <NUM> during final tightening of the implant. This will prevent overtightening or insufficient tightening of the implant components during locking.

Once the present compression screw <NUM> has been placed and it is time to lock the bone screw <NUM> post and compression sleeve <NUM> together, a driver is inserted into the drive feature <NUM> in the top of the breakaway screw270. The screw is then inserted into the sleeve and tightened until a set torque is reached. Once the failure torque is reached, the breakaway section shears in torsion and leaves the jam screw within the sleeve, binding the post <NUM> to the sleeve <NUM>.

<FIG> is a perspective view of a suture breakaway jam screw <NUM> having a shaft <NUM>, jamming screw <NUM>, and breakaway region <NUM>. The suture jam screw <NUM> is the same as the breakaway jam screw <NUM>, except that it has a distal side through-hole <NUM> and a pair of side grooves/channels <NUM> which interrupt the threading of the jamming screw <NUM>. The through-hole <NUM> and side grooves <NUM> allow a suture to be attached to the jam screw <NUM> prior to insertion. After the jam screw <NUM> is broken off within the present compression screw <NUM>, the suture <NUM> falls out the back of the compression sleeve <NUM> and can be tied down to the surrounding anatomy. This will allow the present compression screw <NUM> to be used as a type of suture button and will provide additional fixation to the screw head after placement.

<FIG> are top view and perspective view of a bone screw, respectively, according to another aspect of the present invention. <FIG> are top view and perspective view of a compression sleeve that mates with the bone screw of <FIG>.

The compression screw <NUM> has a drive feature in both the proximal end of the bone screw <NUM> and compression sleeve <NUM>. Both of these drive features needed to be engaged by a driver to insert the screw <NUM> in a locked state. Having a drive feature in the proximal end of the bone screw post required a larger outer diameter for the proximal end to account for the drive feature. This in turn led to a larger compression sleeve which mates to the bone screw post.

The two drive feature requirement made the screw size relatively large and needed to be decreased significantly. One aspect of the design as shown in <FIG> is a novel method, that is not within the scope of the invention, for insertion of a two-piece screw without the use of a traditional drive feature. This method relies on the interruption of the thread form between mating components to bind the screw at a fixed length for insertion.

To reduce the size of the compression sleeve <NUM>, the drive feature in the bone screw <NUM> was replaced with three small cutouts <NUM> in the top of the bone screw threading <NUM>. The cutouts <NUM> look like a cruciform drive, but with three cutouts instead of four.

The interruption of the threading <NUM> on the bone screw <NUM> can be seen in <FIG>.

Three grooves <NUM> were then added to the distal end of the mating compression sleeve <NUM> which interrupt the internal threading of the compression sleeve. These grooves <NUM> are equivalent in size to the three cutouts <NUM> present on the bone screw <NUM> post. The depth of these grooves <NUM> is equivalent to the major diameter of the female thread present within the sleeve <NUM>. These grooves <NUM> can be seen in <FIG>.

As seen in <FIG>, the compression screw <NUM> is then assembled such that the three cutouts <NUM> in the bone screw <NUM> post and the three grooves <NUM> in the compression sleeve <NUM> are circumferentially aligned with alignment markings <NUM>. Prior to alignment, typically, the bone screw <NUM> would be rotated all the way. e.g., clockwise, until the screw bottoms out in the internal threading of the sleeve <NUM> such that the compressions screw <NUM> would be at its maximum length. Laser marking symbols <NUM> on either component can be used to aid alignment of the two components <NUM>,<NUM>.

Although three cutouts <NUM> are shown, any number of cutouts could be used. For example, in one embodiment, the prongs <NUM> can be one to four in numbers, which means there will be corresponding number of cut outs to interrupt the threading.

Once the three cutouts <NUM> and the three grooves <NUM> are circumferentially aligned, a single-piece driver <NUM> as shown in <FIG> is inserted into the screw <NUM>. As shown in <FIG>, the driver <NUM> shaft has two separate drive features: a hex feature <NUM> which mates to the hex drive feature <NUM> in the head of the compression sleeve <NUM>, and three prongs <NUM> which mate to the aligned features <NUM>,<NUM> between the bone screw <NUM> post and compression sleeve <NUM>. The prongs <NUM> are positioned distally of the hex drive feature of <NUM> such that when the driver <NUM> is inserted into the compression screw <NUM>, the two drive features mate with the respective drive features <NUM> and <NUM>,<NUM> to lock the compression sleeve <NUM> and bone screw <NUM> together.

Once the final position of the screw tip is achieved, a second driver such as the countersink driver <NUM> of <FIG> which only has the hex drive feature <NUM> that mates with the hex drive feature <NUM> of the compression sleeve <NUM>, is used to countersink and compress the length of the screw <NUM>.

By using the design that interrupts the thread form between the bone screw <NUM> post and compression sleeve <NUM>, the relative size of the screw <NUM> was significantly reduced. This may improve surgical outcomes and use because the screw <NUM> could be used in more areas where a smaller size implant is very important. This method of insertion, not within the scope of the invention, also simplifies the surgical procedure and instrumentation. The mating driver also does not use any complex mechanisms for insertion.

Although not shown in <FIG>, the driver <NUM> may be used with the sleeve coupler <NUM> through its own retaining feature <NUM> that locks into the sleeve coupler lock <NUM> for locking the driver relative to the compression screw <NUM> to prevent the driver from inadvertently backing out of the screw.

<FIG> is a perspective view of a compression screw having a pair of retaining clips according to another aspect of the present invention. <FIG> shows cross-sectional views of the retaining c-clip <NUM> and mating groove of the bone screw in a disassembled state and assembled state.

The bone screw <NUM> has an external threading <NUM> which is threaded into an internal threading of the compression sleeve <NUM>. The external threading <NUM> has a pair of mating grooves <NUM> that receive corresponding c-clips <NUM>,<NUM>.

After threading the compression sleeve <NUM> onto the bone screw <NUM> post, the c-clip <NUM> is assembled into the groove <NUM> in the proximal end of the bone screw post. If the screw <NUM> is attempted to be disassembled, the c-clip <NUM> interrupts the thread form in the compression sleeve <NUM> and prevents the disassembly of the two components.

The outer diameter of each c-clip <NUM>,<NUM> is equal to or greater than the major diameter of the threads <NUM> on the proximal end of the bone screw <NUM> post and less than the minor diameter of the blind hole in the distal end of the compression sleeve <NUM>.

A second c-clip <NUM> may be placed in a groove <NUM> further distal of the threaded shaft of the bone screw <NUM> post to limit the travel of the sleeve <NUM>. The c-clips <NUM>,<NUM> are designed in such a way that they do not expand or collapse into the mating grooves <NUM>.

The second c-clip <NUM> and even the first c-clip <NUM> may be laser welded to prevent disassembly. The c-clip is designed in such a way that it does not expand or collapse into the groove. The minor diameter of the c-clip is equivalent to or greater than the mating groove diameter.

The c-clips <NUM>,<NUM> advantageously prevent disassembly of the screw <NUM> prior to use, during use, or after implantation within the patient. There are numerous risks associated with utilizing a device that has the potential to disassemble during a surgical procedure. Addressing these risks will reduce the risk to an acceptable level.

Limiting the travel of the sleeve <NUM> along the length of the bone screw <NUM> post (reducing the overall length of the screw <NUM>) also improves the ability of the implant to consistently countersink below the surface of the bone and achieve its final targeted length. If no method was applied to limit the amount of travel, the proximal end of the sleeve <NUM> could fall below the proximal end of the bone screw <NUM> post, which could potentially force the driver off of the screw preventing further countersinking or removal due to lack of a drive feature.

<FIG> is a perspective view of a compression screw with a pin for limiting travel. <FIG> is a cross-sectional view of the compression screw <NUM> and the pin of <FIG>.

After threading the compression sleeve <NUM> onto the bone screw <NUM> post, a pin <NUM> is pressed through a thru hole <NUM> (normal to the axis of the screw) in the proximal end of the bone screw post. The length of the pin is equal to the major diameter of the threads on the proximal end of the bone screw post and less than the minor diameter of the blind hole in the distal end of the compression sleeve. The pin <NUM> interrupts the thread form and prevents disassembly of the two components. Although not shown, a second pin <NUM> can also be placed in a second thru hole down the threaded shaft of the bone screw <NUM> post to limit the travel of the sleeve <NUM>. Thus, instead of the mating grooves <NUM> as shown in <FIG>, there would be two through holes and instead of the c-clips <NUM>,<NUM>, there would be two pins <NUM>.

<FIG> shows a perspective view of a compression screw with deformed threading.

After threading the compression sleeve <NUM> onto the bone screw <NUM> post, a proximal portion <NUM> of the threads <NUM> is deformed utilizing a variety of methods (swaging, end-forming, knurling, and the like). The deformation of the threads prevents the disassembly of the components <NUM>,<NUM>. An additional deformed portion <NUM> distal of the proximal portion <NUM> may be formed on the threading <NUM> of the bone screw <NUM> post to limit the travel of the sleeve <NUM>.

<FIG> show a side view and perspective view of a compression sleeve having a distal drill tip according to yet another aspect of the present invention. <FIG> is a side view of the compression sleeve of <FIG>.

A drill tip <NUM> geometry of the sleeve <NUM> optimizes the cutting ability of the sleeve and improve insertion of the screw <NUM>. By optimizing the cutting ability, the screw <NUM> gains better purchase and achieve greater compression.

The drill tip <NUM> geometry includes a drill margin (e.g., 3x margin), cutting flutes <NUM> which define slots through which cut bone is evacuated proximally, and lip relief (e.g., <NUM>-<NUM> degrees) <NUM> located on the tip of the compression sleeve <NUM> which mates to the bone screw <NUM> post.

This drill tip geometry improves the cutting ability of the compression sleeve <NUM> and evacuates the bone centrifugal to the sleeve (like a drill) instead of pushing it forward. The bone fills in the space behind the drill tip <NUM> to provide better thread purchase for the threads on the compression sleeve <NUM>.

The outer diameter of the drill tip is equal to or less than the minor diameter of the threads on the compression sleeve. The rake angle is the angle between the flute <NUM> and longitudinal axis of the sleeve <NUM>. The rake angle on the drill point sleeve can be between <NUM>° (parallel) and <NUM>° (positive), but more particularly <NUM>-<NUM> degrees. The margin is the trailing edge of the cutting surface. The drill tip <NUM> has three margins to allow for better self-centering of the compression sleeve <NUM> during insertion than a single or double margin drill geometry. The compression sleeve <NUM> tapers to a smaller diameter behind the drill tip geometry (see taper portion <NUM> in FIG. <NUM>) to provide clearance and reduce friction. Thus, the diameter of the drill tip <NUM> is large than that of the shaft of the compression sleeve <NUM>.

Claim 1:
A variable length headless compression screw insertion system comprising:
- a compression screw (<NUM>) having a bone screw (<NUM>) and a compression sleeve (<NUM>) coupled to the bone screw (<NUM>), wherein: the bone screw (<NUM>) including a proximal end (<NUM>) having an external threading (<NUM>, <NUM>) threadably received in the compression sleeve (<NUM>), and the compression sleeve (<NUM>) includes a proximal end (<NUM>) having a predefined drive feature (<NUM>, <NUM>) and an external threading;
- a driver assembly (<NUM>) for driving the compression screw (<NUM>) into a bone and including: a sleeve coupler (<NUM>) adapted to threadably receive the external threading (<NUM>) of the compression sleeve (<NUM>); a ram driver (<NUM>) adapted to be coupled to the sleeve coupler (<NUM>) and having a predetermined length such that its distal end is shaped to contact the proximal end of the bone screw (<NUM>) to prevent translation of the bone screw (<NUM>) relative to the compression sleeve (<NUM>);
- wherein the driver assembly (<NUM>) further comprises a sleeve driver (<NUM>; <NUM>) adapted to be coupled to the sleeve coupler (<NUM>) and having a predetermined length such that its distal end (<NUM>) has a complementary drive feature (<NUM>) that mates with the predefined drive feature (<NUM>) of the compression sleeve (<NUM>), the sleeve driver (<NUM>; <NUM>) adapted to rotate the compression sleeve (<NUM>) relative to the sleeve coupler (<NUM>); and characterised in that
- the compression sleeve (<NUM>) includes a shaft having a first outer diameter and a drill tip (<NUM>) extending from the shaft and having a second outer diameter larger than the first diameter.