Headless compression screw having an attachment mechanism

A cannulated headless compression screw is provided with an attachment mechanism that enables coupling various attachments to the headless compression screw. The headless compression screw includes a screw thread on its exterior that is adapted to effect compression between two bone fragments. For instance, the exterior screw thread may have a variable pitch formed to effect such compression. The interior of the headless compression screw's trailing end includes an interface that is adapted to engage with a driving instrument. A surgeon may drive the headless compression screw into bone via the driving instrument and then access the attachment mechanism to couple an attachment to the headless compression screw.

BACKGROUND

To help heal bone fractures, it is desirable to compress the fractures so that the fractured bone surfaces are pressed against one another. Typically, bone screws have been used to draw the fractured bone surfaces together and thereby help the healing process. Some typical bone screws include a head connected to a threaded root portion. Such typical headed screws, however, may have a number of drawbacks including concentrated loads beneath the screw head and the screw head's protrusion away from the bone, particularly around articulating surfaces, once inserted.

Another potential drawback is a bone fragment nearest the screw head is held relative to the far bone fragment purely by compressive forces provided by the screw head. If the cortical bone layer directly under the screw head provides inadequate support either during insertion or subsequently, then compression is lost and the near bone fragment may be free to move relative to the trailing part (e.g., near the head) of the screw. Consequently, relative movement between the bone fragments may occur, which harms the healing process. In addition, a further drawback is bone resorption, which is a physiological response to localized pressure. Bone resorption may occur either directly under the screw head or at the fracture site. When resorption occurs, the screw may loosen which allows relative movement between the bone fragments to occur and harms the healing process.

Headless compression screws offer several advantages as compared to headed compression screws in various instances. Headless compression screws are installed completely within the two bone fragments thereby leaving no part to protrude away from the bone surface as compared to the protruding head of an installed headed screw, which may be beneficial in certain procedures. Additionally, headless compression screws effect and maintain compression between the bone fragments due to variable thread formation, and in no part by compressive forces provided by a head. Accordingly, headless compression screws do not produce the concentrated loads that headed screws produce as described above, which may be beneficial in certain procedures.

Additionally, in some instances, a surgical procedure may involve the installation of suture, anchors, plates, other implants, etc. along with a headed or headless compression screw. For example, a patient may have a soft tissue or ligament injury in addition to a bone fracture. Such a compound injury requires both a compression screw to draw the bone fragments together and suture to secure the injured soft tissue or ligament to bone. Typically, when using a headless compression screw to treat such compound injuries, a surgeon must install a headless compression screw and subsequently use suture to secure the soft tissue, either using a suture anchor into bone or performing other suture attachment techniques. Installing two or more components may contribute to longer surgical procedure times and lengthier patient recovery times.

Accordingly, there exists a need for a headless compression screw that solves the above drawbacks.

SUMMARY

The present disclosure provides new and innovative systems and methods for treating bone fractures with a headless compression screw, such as a compound injury having a bone fracture and a soft tissue or ligament injury. In an example, a system includes a headless compression screw and an attachment. The headless compression screw includes a hollow root portion having a leading end and a trailing end and an interior channel extending from the leading end to the trailing end. An exterior screw thread is formed on at least a portion of the exterior of the hollow root portion between the leading end and the trailing end. An interior screw thread is formed on the interior of the hollow root portion at its trailing end. A portion of the interior of the hollow root portion's trailing end is configured to engage with a driving instrument. The attachment includes a threaded portion configured to engage the hollow root portion's interior screw thread such that when engaged the attachment is coupled to the headless compression screw.

In another example, a system includes a headless compression screw and an attachment. The headless compression screw includes a hollow root portion having a leading end and a trailing end and an interior channel extending from the leading end to the trailing end. An exterior screw thread is formed on at least a portion of the exterior of the hollow root portion between the leading end and the trailing end. A notch is formed into the interior of the hollow root portion at its trailing end. A portion of the interior of the hollow root portion's trailing end is configured to engage with a driving instrument. The attachment includes a portion configured to engage the hollow root portion's notch such that when engaged the attachment is coupled to the headless compression screw.

In an example, a method for drawing two bones segments together and securing tissue to at least one of the two bone segments includes drilling a bone hole through the two bone segments. A headless compression screw is then inserted into the bone hole via a driving instrument such that the headless compression screw secures the two bones together. The headless compression screw includes a hollow root portion having a leading end and a trailing end and an interior channel extending from the leading end to the trailing end. An exterior screw thread is formed on at least a portion of the exterior of the hollow root portion between the leading end and the trailing end. An interior screw thread is formed on the interior of the hollow root portion at its trailing end. The driving instrument engages a portion of the interior of the hollow root portion's trailing end. After the headless compression screw is inserted into the bone hole, the method may include inserting a threaded portion of an attachment into the hollow root portion's interior screw thread such that the attachment couples to the headless compression screw. Suture may be secured to the attachment. Tissue may be secured to at least one of the two bone segments via the suture.

DETAILED DESCRIPTION

The present disclosure provides a cannulated headless compression screw with an attachment mechanism that enables coupling various attachments to the headless compression screw. The provided headless compression screw includes a leading end and a trailing end. The leading end is driven into bone. The interior of the headless compression screw's trailing end includes an interface that is adapted to engage with a driving instrument. For example, the trailing end may be adapted to engage with a hexagon-shaped driving instrument. A surgeon may therefore drive the headless compression screw into bone via the driving instrument. The headless compression screw includes a screw thread on its exterior that is adapted to effect compression between two bone fragments when the headless compression screw is installed across a fracture. For instance, the exterior screw thread may have a variable pitch formed to effect such compression.

The headless compression screw's attachment mechanism is within the interior of the headless compression screw. In some instances, the attachment mechanism may include an interior thread such that an attachment may be coupled to the headless compression screw by threaded engagement. In other instances, the attachment mechanism may include a notch such that an attachment may be coupled to the headless compression screw by snapping into or engaging with the notch. In some examples, the attachment mechanism may be closer to the leading end than the driver instrument interface. Such examples may help a surgeon engage a driving instrument with the headless compression screw's interface without interference from the attachment mechanism. For instance, once the surgeon installs the headless compression screw into bone and removes the driving instrument, the surgeon may then couple an attachment to the headless compression screw.

The attachment may be any suitable implant that adds utility to a surgical procedure utilizing the provided headless compression screw. For example, a patient may have a compound injury including a bone fracture and a soft tissue or ligament injury. A surgeon may install the provided compression screw across the fracture to help heal the bone fracture. Typically, to help heal the soft tissue or ligament injury, the surgeon may install a suture anchor into bone (e.g., one of the bone fragments of the fracture) so that the surgeon may secure the soft tissue or ligament to the bone with suture via the suture anchor. The provided headless compression screw, however, enables the surgeon to instead couple a suture anchor to the headless compression screw itself. By eliminating the need to install a separate suture anchor into bone, the provided headless compression screw helps contribute to shorter surgical procedure times and may aid in shorter patient recovery times. Other example attachments will be described in more detail below.

FIGS.1A and1Billustrate a perspective and cross-sectional view respectively of an example headless compression screw100. The example headless compression screw100includes a root portion102. The root portion102extends from a leading end108to a trailing end110. The root portion102is cannulated or hollow such that it includes a channel106that extends from the leading end108to the trailing end110. The channel106is configured such that the headless compression screw100may be positioned over a guide wire.

An exterior thread104is formed on at least a portion of the root portion102between the leading end108and the trailing end110. For instance, the exterior thread104may be formed such that it is a continuous thread extending from the leading end108to the trailing end110. In another instance, the exterior thread104may be that of a differential pitch or Herbert screw, as will be appreciated by one having skill in the art. The exterior thread104is particularly adapted to effect compression between two bone fragments as a surgeon drives the headless compression screw100into bone and across a fracture. For example, the pitch of the exterior thread104may be larger near the leading end108as compared to the trailing end110. The pitch of the exterior thread104is measured between corresponding points on consecutive thread crests. In another example, the crest radius of the exterior thread104may be larger near the trailing end110as compared to the leading end108. The crest radius of the exterior thread104is measured from a central axis114to an outermost point on the exterior thread104. In at least one example, the exterior thread104may be formed with a variable pitch as described in U.S. Pat. No. 5,871,486, which is herein incorporated by reference.

The interior of the trailing end110of the headless compression screw100may be configured to include a driver interface (e.g., driver interface200inFIG.2). A surgeon may position a driving instrument within the driver interface to engage the driving instrument to the headless compression screw100and drive the headless compression screw100into bone. When engaged, the driving instrument is positioned and maintained fully within the channel106of the headless compression screw100. Such a configuration that maintains the driving instrument fully within the channel106helps maximize engagement between the driving instrument and the headless compression screw100. It also may help limit the driving instrument's contact with the bone hole during insertion of the headless compression screw100. The leading end108of the headless compression screw100is configured to drive into bone to advance the headless compression screw100through bone.

The interior of the trailing end110of the example headless compression screw100also includes a threaded attachment mechanism112. The threaded attachment mechanism112enables a surgeon to couple an attachment to the headless compression screw100by threaded engagement. The threaded attachment mechanism112may be closer to the leading end108than the driver interface, as illustrated. Such positioning enables a driving instrument to engage the headless compression screw100without interference from the threaded attachment mechanism112. Once a surgeon drives the headless compression screw100into bone and removes the driving instrument, the threaded attachment mechanism112may be accessed so that a surgeon may couple an attachment to the headless compression screw100. Additionally, if an attachment is not needed, a surgeon may simply not add an attachment. The threaded attachment mechanism112is within the interior of the headless compression screw100and does not affect insertion of the headless compression screw100. Further, the headless compression screw100provides the same fracture compression benefits with or without an attachment added. Thus, an attachment is an optional add-on to provide an additional feature.

In some aspects, the threaded attachment mechanism112is threaded opposite of the exterior thread104. Stated differently, the exterior thread104may be configured such that threaded engagement is advanced clockwise whereas the threaded attachment mechanism112may be configured such that threaded engagement is advanced counter-clockwise, or vice versa. In such aspects, a surgeon may thread a driving instrument into the threaded attachment mechanism112to remove the headless compression screw100from bone. This feature is beneficial if the driver interface becomes damaged and therefore cannot be used to remove the headless compression screw100from bone.

FIG.1Cillustrates a cross-sectional view of an example headless compression screw120. The headless compression screw120may be similar to the headless compression screw100, except that the driver interface (e.g., driver interface200inFIG.2) is oriented opposite of the threaded attachment mechanism112. As shown, in such an example, the threaded attachment mechanism112is wider than the driver interface so that a drive mechanism fits within the minor diameter of the threads in the threaded attachment mechanism112. The wider threaded attachment mechanism112enables the drive mechanism to engage the headless compression screw120without interference from the threaded attachment mechanism112.

FIG.2illustrates a view of the trailing end110along a long axis of the headless compression screw100showing an example driver interface200. As illustrated, the driver interface200may have a larger cross sectional area than the threaded mechanism112and the remaining portion of the channel106. Such a configuration prevents a driving instrument from being inserted past the threaded attachment mechanism112and into the remaining portion of the channel106. The example driver interface200is adapted for use with a hexagon-shaped driving instrument. In other examples, the driver interface200may be adapted for use with driving instruments having other shapes, such as hexalobe, square, Phillips, Pozidriv, Torx, Security T, etc.

The headless compression screw100may be constructed of any suitable biocompatible material. For example, stainless steel, a cobalt-chromium alloy, titanium, a titanium alloy, magnesium, or polyether ether ketone (PEEK) are suitable biocompatible materials.

One example of an attachment that may be coupled to the headless compression screw100is a suture anchor.FIGS.3A and3Billustrate cross sectional views of an example system300that includes the headless compression screw100and an example suture anchor attachment302. The suture anchor attachment302may attach to the headless compression screw100and couple suture to the headless compression screw100. In some instances, the example suture anchor attachment302may have a fully closed eyelet304through which suture may be passed, such as the illustrated example. In other instances, the suture anchor attachment302may have an eyelet304that is not fully closed such that it is a hook that secures suture.

The suture anchor attachment302may include a threaded portion306. The eyelet304may be connected to the threaded portion306by an arm310. The threaded portion306is adapted to engage the threaded attachment mechanism112. A surgeon may translate the suture anchor attachment302in the direction of the arrow308as shown inFIG.3Aand rotate it to engage the suture anchor attachment302with the threaded attachment mechanism112, thereby coupling the suture anchor attachment302to the headless compression screw100as shown inFIG.3B. In the illustrated example, the eyelet304is fully within the channel106when the threaded portion306of the suture anchor attachment302is fully engaged with the threaded attachment mechanism112. In other examples, the arm310may be longer such that a portion or all of the eyelet304extends outside of the channel106.

In an example, as described above, a surgeon may install the headless compression screw100across a fracture to help the fracture heal and may couple suture to the suture anchor attachment302to secure an injured soft tissue or ligament to one of the bone fragments, which helps the soft tissue or ligament heal. The suture may be passed through the eyelet304before the suture anchor attachment302is coupled to the headless compression screw100or after the suture anchor attachment302is coupled to the headless compression screw100. The example system300including a headless compression screw100and a coupled suture anchor attachment302may be used with a standard suture technique or a knotless suture construct.

Another example of an attachment that may be coupled to the headless compression screw100is a surgical plate. For example, the surgical plate may be an avulsion hook plate, though other suitable surgical plates may be coupled to the headless compression screw100, such as a buttress plate, small fragment plates, pre-contoured bone plates, one-third tubular plate, or t-plates. Avulsion hook plates are typically used to treat an avulsion fracture, which is an injury to the bone in a location where a tendon or ligament attaches to the bone. When an avulsion fracture occurs, the tendon or ligament pulls a fragment of the bone away from the main part of the bone. An avulsion hook plate may be used to secure the bone fragment to the main part of the bone. Typically, an avulsion hook plate is coupled to the head of a screw that is installed in the main part of the bone.FIG.4Aillustrates a perspective view of an example system400that includes the headless compression screw100and a one-sided avulsion hook plate attachment402. In some instances, the one-sided avulsion hook plate attachment402may include an opening though which a screw passes to couple the one-sided avulsion hook plate attachment402to the headless compression screw100(e.g., see the system410inFIG.4Bhaving a screw414). In other instances, the one-sided avulsion hook plate attachment402includes a threaded part (not illustrated) that is engaged with the threaded attachment mechanism112(not illustrated) to couple the one-sided avulsion hook plate attachment402to the headless compression screw100. The example system400enables a surgeon to treat a bone fracture as well as an avulsion fracture with a single tool. While the one-sided avulsion hook plate attachment402protrudes from a bone surface when coupled to an installed headless compression screw100, the system400provides the other benefits of a headless compression screw described above.

FIG.4Billustrates an example system410that includes the headless compression screw100and a two-sided avulsion hook plate attachment412. In some instances, the two-sided avulsion hook plate attachment412may include an opening though which a screw414passes to couple the two-sided avulsion hook plate attachment412to the headless compression screw100. The screw414engages the threaded attachment mechanism112(not illustrated). In other instances, the two-sided avulsion hook plate attachment412may include a threaded part that is engaged with the threaded attachment mechanism112(not illustrated) to couple the two-sided avulsion hook plate attachment412to the headless compression screw100. The example system410enables a surgeon to treat complex fractures around an entry site for the headless compression screw100using a single tool. For example, the system410may enable a surgeon to treat a bone fracture as well as two separate avulsion fractures with a single tool. While the two-sided avulsion hook plate attachment412protrudes from a bone surface when coupled to an installed headless compression screw100, the system410provides the other benefits of a headless compression screw described above.

It should be appreciated that the one-sided and two-sided avulsion hook plate attachments402and412are illustrated merely as example plates. The aspects described in connection with the one-sided and two-sided avulsion hook plate attachments402and412may be applied to other suitable surgical plates. For example, other suitable surgical plates may include buttress plates, small fragment plates, pre-contoured bone plates, one-third tubular plate, or t-plates.

A further example of an attachment that may be coupled to the headless compression screw100is a solid core.FIG.5Aillustrates a cross sectional view of an example system500that includes the headless compression screw100and a solid core attachment502A. The solid core attachment502A reinforces the cannulated headless compression screw100to increase the strength of the headless compression screw100. For instance, the strength of the cannulated headless compression screw100may be increased to a strength comparable to a solid core compression screw. The solid core attachment502A is configured to shape fit within the channel106. Stated differently, there is very little to no space between the surface of the solid core attachment502A and the interior surface of the headless compression screw100within the channel106. The solid core attachment502A may fill the entire length of the channel106or a portion of it. For example, the solid core attachment502A may fill a substantial portion of the length of the channel106as illustrated. The solid core attachment502A includes a threaded portion504such that the threaded portion504engages the threaded attachment mechanism112to couple the solid core attachment502A to the headless compression screw100.

The solid core attachment502A may include a driver interface506adapted to engage with a driving instrument. In some aspects, the solid core attachment502A may be coupled to the headless compression screw100prior to a surgeon installing the headless compression screw100. The surgeon may then install the headless compression screw100into bone via engaging a driving instrument with the driver interface506. In other aspects, the solid core attachment502A may be coupled to the headless compression screw100after the surgeon installs the headless compression screw100into bone.

In some aspects, the solid core attachment502A may be the same material as the headless compression screw100. In other aspects, the solid core attachment502A may be a different material than the headless compression screw100. For example, the headless compression screw100may be constructed of titanium while the solid core attachment502A is constructed of a cobalt-chromium alloy.

Additionally, in some aspects, the solid core attachment may be constructed such that its stiffness or strength is reduced as compared to the uniformly solid example solid core attachment502A illustrated inFIG.5A. For instance,FIG.5Billustrates a solid core attachment502B having a reduced portion510. The reduction of material at the reduced portion510reduces the stiffness or strength of the solid core attachment502B as compared to the solid core attachment502A. In another instance,FIG.5Cillustrates a solid core attachment502C having multiple holes512A,512B,512C. The reduction of material by the holes512A,512B,512C reduces the stiffness or strength of the solid core attachment502C as compared to the solid core attachment502A. The solid core attachment502C may have any suitable quantity or shape of holes512A,512B,512C. Various configurations may enable varying levels of stiffness or strength of the solid core attachment502A,502B,502C. A surgeon may choose a solid core attachment502A,502B,502C that has a desired level of stiffness or strength for a given procedure.

While the preceding examples of the provided headless compression screw are described as having a threaded attachment mechanism, other adaptations of the attachment mechanism are contemplated for coupling an attachment to the headless compression screw. For example,FIG.6illustrates a system600including an example headless compression screw602having a snap attachment mechanism604. The system600also includes an example suture anchor attachment610. The snap attachment mechanism604includes a notch formed into the interior surface of the headless compression screw602. The suture anchor attachment610includes a snap portion614. The snap portion614is configured to deform such that it snaps into the notch, thereby coupling the suture anchor attachment610to the headless compression screw100. The suture anchor attachment610may have a fully closed eyelet612, such as the illustrated example. In other instances, the suture anchor attachment610may have an eyelet612that is not fully closed such that it is a hook that secures suture. It should be understood that any of the attachments described herein may be configured with a snap portion instead of a threaded portion such that they engage with a provided headless compression screw having a snap attachment mechanism.

Without further elaboration, it is believed that one skilled in the art can use the preceding description to utilize the claimed inventions to their fullest extent. The examples and aspects disclosed herein are to be construed as merely illustrative and not a limitation of the scope of the present disclosure in any way. It will be apparent to those having skill in the art that changes may be made to the details of the above-described examples without departing from the underlying principles discussed. In other words, various modifications and improvements of the examples specifically disclosed in the description above are within the scope of the appended claims. For instance, any suitable combination of features of the various examples described is contemplated.