Patent ID: 12201324

All illustrations shown in the figures are schematic and are not intended to show actual dimensions or proportions.

DETAILED DESCRIPTION

This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top,” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

Disclosed is a novel method for fusing a joint between two bones using a nested screw assembly. An example of an application of the disclosed novel method is fusing the first tarsometatarsal (TMT) joint in a Lapidus procedure.

Referring toFIGS.1A-6, a nested screw assembly100according to an embodiment is disclosed. The nested screw assembly100comprises a cannulated outer screw110and an inner screw120that is threaded into the cannulated outer screw110.

Referring toFIG.3, in some embodiments, the outer screw110comprises a body that is a tubular structure having a first end111and a second end112defining a length between the two ends, and a canal114extending through the length of the outer screw110. At least a portion of the length of the outer screw is externally threaded with threading116and at least a portion119of the length of the canal114is internally threaded with threading118near the first end111. In the illustrated example inFIG.3, the whole length of the exterior surface of the outer screw110is threaded.

Referring toFIG.2A, the inner screw120comprises a body, a substantial portion125of which is externally threaded with threading126. The internal thread118of the outer screw and the external thread126of the inner screw have the same thread pitch so that the inner screw120can be threaded into the first end111of the canal114of the outer screw110to form the nested screw assembly100. The external thread116of the outer screw110is also configured to have the same thread pitch and handedness as the internal thread118of the outer screw and the external thread126of the inner screw.

Referring toFIGS.2A and4, in some embodiments of the nested screw assembly, the inner screw120comprises an oval head122. The head122can be provided with a socket125for receiving a driver tool bit for screwing/unscrewing the inner screw120.

Referring toFIGS.5and6, in another embodiment, the inner screw120′ is a headless type and comprises a threaded head portion122′ with a thread pitch that is different from the thread pitch of the external thread116of the outer screw, the internal thread118of the outer screw, and the external thread126of the inner screw120′. In some embodiments, the thread pitch on the threaded head portion122′ is smaller than the thread pitch of the other threads.

In some embodiments, the outer screw110further comprises a driving feature115provided inside the canal114near the second end112. The driving feature115can be a socket, such as a hex socket, star drive socket, etc. The driving feature115enables the outer screw110to be screwed into a bone using an appropriate drive bit inserted into the second end opening113(seeFIGS.3-4).

In the embodiment of the nested screw assembly100where the inner screw120′ has the threaded head portion122′, a compression sleeve200can be used to drive the inner screw120′ into the outer screw110. The longitudinal cross-sectional view inFIG.6shows the nested screw assembly100and the compression sleeve200engaging the threaded head portion122′ of the inner screw120′. The compression sleeve200comprises an internally threaded opening206at one end for engaging the threaded head portion122′ of the inner screw120′. The compression sleeve200can also be provided with a tool receiving socket225on the opposite end for receiving a driver tool for turning the compression sleeve200.

Referring to the flowchart10inFIG.7and theFIGS.8A-8D, a method for fusing a joint between two bones using the nested screw100will be described. A method for fusing a joint between a first bone B1and a second bone B2using the nested screw assembly100comprises the following procedures. First, (a) a hole is pre-drilled into the first bone B1and the second bone B2through the joint. The joint is indicated by the line J inFIG.8A. Then, referring toFIG.8A, (b) the outer screw110is screwed/threaded into the hole in the first bone B1up to the joint J. The direction of the outer screw's advancement into the first bone B1is indicated by the arrow A1. Referring toFIG.8B, next, (c) the inner screw120′ is screwed/threaded into the hole in the second bone B2from the opposite side until the inner screw120′ engages with the internally threaded portion119of the outer screw110from the first end111of the outer screw and form a nested screw assembly. The direction of the inner screw's advancement here is indicated by the arrow A2inFIG.8B. Then, to compress the two bones B1, B2together at the joint, the inner screw120′ is tightened while holding the outer screw110from turning. The outer screw110can be held in place from turning using a driver tool that is inserted into the second end112of the outer screw to engage the driving feature115in the canal114. The inner screw120can be driven using the compression sleeve200. As illustrated inFIG.8B, with the compression sleeve200engaged to the threaded head portion122′ of the inner screw120′, because the compression sleeve200has a larger diameter than the inner screw120and the hole in the second bone B2, as the inner screw120′ is threaded into the outer screw110and advanced in the direction of the arrow A2with respect to the first bone B1and the outer screw110, the compression sleeve200comes in contact with the second bone B2and compresses the second bone B2toward and against the first bone B1. Once the desired compression of the two bones B1, B2is achieved, the compression sleeve200is removed. SeeFIG.8C.

If an embodiment of the nested screw assembly100that comprises the oval headed inner screw120(seeFIG.2A) is used, as the inner screw120is threaded into the outer screw110and advance in the direction of the arrow A2with respect to the first bone B1and the outer screw110, the head122of the inner screw120, rather than the compression sleeve200, will come into contact with the second bone B2and compress the second bone B2toward and against the first bone B1. Thus, when the oval headed inner screw120is used, the compression sleeve200is not needed as a standard screwdriver can be used with the oval headed inner screw120.

Referring toFIG.8D, after the compression of the two bones B1, B2is achieved, (d) the outer screw110is screwed further into the hole in the first bone B1in the direction A1, toward and across the joint J to maintain the compression of the joint. This procedure is carried out while the inner screw120is held in place using a driver bit inserted into the tool socket125of the inner screw. This procedure is possible because the external thread116of the outer screw110has the same thread pitch and handedness as the internal thread118of the outer screw and the external thread126of the inner screw. With the inner screw120in place, the outer screw can be driven across the joint because the outer screw threads across the bone at the same rate it threads over the inner screw120.

For the embodiment where the headless inner screw120′ with the threaded head portion122′ is used, after the step (c), the threaded head portion122′ of the inner screw120′ is buried into the second bone B2, so that the head portion122′ is not protruding from the bone B2, by driving the inner screw120′ out of the compression sleeve200. This is illustrated inFIG.8C. This step of burying the head portion122′ of the inner screw120′ into the second bone B2can be done either before or after the outer screw110is advanced across the joint J.FIG.8Dshows the position of the headless inner screw120′ after the head portion122′ is buried into the second bone B2.

FIG.9is an illustration showing the nested screw assembly embodiment where the oval headed inner screw120is used rather than the headless inner screw120′ after the compression of the bones B1, B2is completed.

Referring toFIG.6, in some embodiments, the outer screw110comprises a driving feature115provided inside the canal114near the second end112, and the outer screw is threaded into the hole in the procedure (b) by engaging the driving feature115with a driving tool.

Although the devices, kits, systems, and methods have been described in terms of exemplary embodiments, they are not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the devices, kits, systems, and methods, which may be made by those skilled in the art without departing from the scope and range of equivalents of the claimed devices, kits, systems, and methods.