Patent Description:
Spinal fixation devices may be anchored to specific portions of the vertebra. Such spinal fixation devices may include, for example, a shank portion coupleable to a vertebra, and a head portion having a receiving element. A fixation rod may be seated through the receiving element and locked in place by tightening a locking cap to the head portion. While known spinal fixation systems have proven effective, some rod reducers may be difficult, tiresome, and/or time-consuming to use. For example, in minimally invasive surgery (MIS) applications, percutaneous screws are commonplace in thoracolumbar fixation systems but few options exist for cervical spine applications where a patient's musculature is disrupted greatly in open cases. Most systems for MIS screws are either extended tabs of the screwhead itself or an attachable tower which is similar to a cylinder the entire length of the instrument.

<CIT> discloses systems and methods for positioning a connecting member adjacent the spinal column including at least one anchor assembly having an anchor engageable to bony structure and a receiver for receiving the connecting member. An extension member is engaged to the receiver and defines a pathway that extends proximally from the receiver. The connecting member is movable along the extension member to the receiver of the bone anchor. The extension member is removable from the receiver of the bone anchor after the connecting member is positioned in the receiver to provide a low profile anchor and connecting member assembly when finally implanted in the patient.

What is needed and provided herein is a single-use instrument that attaches to existing screws but remain open along the rod slot to allow for screws to intermesh and prevent interference of adjacent screws during screw and rod insertion.

The present invention relates a screw tower for rod insertion according to claim <NUM>. Preferred examples are set forth in the dependent claims. According to some examples of the inventive concepts described herein a screw tower that includes a distal end configured to engage a screw, a proximal end configured to engage instrumentation, a first half and a second half that are connected at the distal end and separately extend to the proximal end, a feature set at the distal end configured to engage a head of a screw. The feature set includes a plurality of chevrons each configured to engage the screw for attachment of the tower to the screw. The feature set further includes a breakpoint configured to allow the first half and the second half to break apart from each other. The screw tower also includes an instrument insertion feature disposed at the proximal end.

Another example that is not part of the present invention, discloses a method of fixating adjacent cervical vertebral bodies. The method includes implanting a screw into a pedicle through an incision, wherein the screw includes a head, and securing a screw tower to the head of the screw. The screw tower includes a distal end configured to engage a screw, a proximal end configured to engage instrumentation, a first half and a second half that are connected at the distal end and separately extend to the proximal end, a feature set at the distal end configured to engage a head of a screw. The feature set includes a plurality of chevrons each configured to engage the screw for attachment of the tower to the screw. The feature set further includes a breakpoint configured to allow the first half and the second half to break apart from each other. The screw tower also includes an instrument insertion feature disposed at the proximal end. The method further includes inserting a rod through the screw tower and into the head of the screw, securing a locking cap to the screw through the screw tower; and breaking the first half and the second half apart at the breakpoint and removing them from the incision.

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate certain non-limiting examples of inventive concepts. In the drawings:.

The drawings, which are not necessarily to scale, depict selected examples and are not intended to limit the scope of the disclosure. Although specific features of various examples of the disclosure may be shown in some drawings and not in others, this is for convenience only. The following detailed description is to be read with reference to the drawings, in which like elements in different figures have like reference characters.

The present disclosure relates to medical devices and, more particularly, to a MIS screw tower. The present disclose allows for percutaneous insertion of spinal screws using standard, already existing screws. The single-use towers allow for more flexibility with screw size selection in-situ and eases logistics of screw size offerings for a case. The towers include reduction features to assist in locating and positioning a rod without requiring an open incision. Taking this MIS approach into, for example, the cervical spine may preserve more posterior support tissue than an open surgery and may alleviate pain and recovery time in posterior cervical fixation surgeries. These towers may be used with navigation systems.

<FIG> illustrates a screw tower <NUM> consistent with the principles of the present disclosure. Screw tower <NUM> includes a distal end <NUM> configured to engage a screw head (e.g., a pedicle screw), a proximal end <NUM> configured to receive a rod to be attached to the screw head and also configured to engage instrumentation to place the rod, facilitate rod reduction, and to lock the rod in place by a locking cap or another manner of fixation. Two halves <NUM> and <NUM> may meet at the distal end and separately extend to the proximal end forming a rod slot <NUM> in between.

Screw tower <NUM> may be used in spinal surgeries where the aim is to fixate adjacent vertebral bodies, and in particular, adjacent cervical vertebral bodies. A surgeon may make an incision in patient for spinal surgery. A pedicle screw may be implanted and screw tower <NUM> may be secured to a head of the screw. A rod may be placed in the pedicle screw, reduction performed, and a locking cap may lock the rod to the pedicle screw. Screw tower <NUM> may be broken or split apart by separating halves <NUM> and <NUM> from each other and removed from the incision leaving the pedicle screw and rod implanted in the patient.

As shown in <FIG>, tower <NUM> has of a feature set <NUM> at distal end <NUM> that matches a screw head to be implanted. Feature set <NUM> includes a partial diameter <NUM> truncated by two larger radii <NUM> which extend to a height to create a tapered/angled conical surface <NUM>.

As shown in <FIG>, within feature set <NUM> there are components that protrude and interface with components of the screw head <NUM>, shown partly in <FIG>. For example, pins or chevrons <NUM> connect to the chevrons of the screw. A relief cut <NUM> is configured to allow for chevrons <NUM> to flex out while a screw is attached. Chevrons <NUM> return to their interfacing position once the screw is fully inserted into the tower. <FIG> illustrates tower <NUM> engaged with a head of a pedicle screw <NUM>. The bottom of feature set <NUM> may be trimmed laterally to reduce the profile of tower <NUM> and better match any bottom-taper the screw may have as shown in <FIG>. Tower <NUM> then extends a distance away from the top of the screw head <NUM> mating feature clearing out of the incision/wound of the patient being treated. Tower <NUM> reduces in diameter once it clears the screw head interface to reduce profile and potential interference with adjacent instrumentation. Tower has an instrument insertion feature <NUM> at proximal end <NUM> for instruments to attach to and facilitate the reduction of the rod and insertion of a locking cap or set screw. The entire length of tower <NUM> includes a rod slot <NUM> slightly larger than a rod slot of the screw head. Tower <NUM> includes a break point <NUM> at distal end <NUM> to facilitate breaking tower <NUM> into two halves so it may be removed once the rod is inserted and secured into the screw as shown in <FIG>. Tower <NUM> may be manufactured as one piece or may be made as two halves that are welded together along or next to the break point feature. <FIG> illustrates a screw tower that has been injection molded and welded together at a breakpoint <NUM>. In this design, there is no window in a chevron <NUM>.

Turning to <FIG>, is illustrated a tower <NUM> that is not part of the present invention. Tower <NUM> is designed to be injection molded with a polymer <NUM> over a metallic insert <NUM>, which includes screw attachment mechanism <NUM>. Insert <NUM> may be bonded or contained within polymer <NUM> using through holes or a 3D printed lattice structure that polymer <NUM> can be injected through. A tip <NUM> of insert <NUM> is free and can be pushed away by the screw as it is inserted into tower <NUM> before returning to its nominal, capturing state. Tower <NUM> have flats <NUM> along the lateral edges to facilitate the molding process and reduce profile. They may include additional through holes <NUM> to facilitate the location of the insert during the molding process. <FIG> illustrate three insert <NUM> designs <NUM>, <NUM>, and <NUM> which could be stamped, laser cut, milled, or 3D printed.

Turning to <FIG> and <FIG>, a tower <NUM> is illustrated that is consistent with the principles of the present disclosure. Tower <NUM> contains two segments. A shorter segment <NUM> (or mini-tower) is a single-use, break away component of tower <NUM> that attaches to a larger segment <NUM> via reusable tabs <NUM>. These two segments attach to each other prior to screw attachment. During use, a user would assemble tabs <NUM> onto shorter segment <NUM>. Tabs <NUM> attach via a track <NUM> (t-slot or dovetail) and are retained to segment <NUM> using a flexible arm <NUM> which contains a pin <NUM> that fits into a matching hole <NUM> of shorter segment <NUM>. With tabs <NUM> attached, the screw can then be loaded into segment or mini-tower <NUM> and the screw is retained flexible arms <NUM> with pins/chevrons <NUM> that are attached to reusable tabs <NUM>. The most distal chevrons <NUM> may attach to the screw and the more proximal chevrons <NUM> may attach segment <NUM> to segment <NUM>. Segment <NUM> allows for a cheaper manufacturing process and may be machined or possibly 3D printed. Reusable tabs <NUM> may have threads <NUM> intended for a reduction driver instead of a dedicated reduction instrument attachment feature at the end of tower <NUM>.

This written description uses examples to disclose aspects of the disclosure and also to enable a person skilled in the art to practice the aspects, including making or using the above-described systems.

Having described aspects of the disclosure in terms of various examples with their associated operations, it will be apparent that modifications and variations are possible without departing from the scope of the disclosure as defined in the appended claims. That is, aspects of the disclosure are not limited to the specific examples described herein, and all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is to be understood that the present disclosure is not limited in its application to the details of construction and/or the arrangement of components set forth in the description herein or illustrated in the drawings. For example, in accordance with the principles of the disclosure, any feature described herein and/or shown in the drawings may be referenced and/or claimed in combination with any other feature described herein and/or shown in the drawings.

When introducing aspects of the disclosure or the examples thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements, unless the context clearly indicates otherwise. References to an "embodiment" or an "example" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments or examples that also incorporate the recited features. The phrase "one or more of the following: A, B, and C" means "at least one of A and/or at least one of B and/or at least one of C. " The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that although ordinal terms (e.g., "first," "second," "third," etc.) may be used herein to describe various elements/operations, these elements/operations should not be limited by these terms.

Claim 1:
A screw tower (<NUM>) for minimal invasive surgery, comprising:
a distal end (<NUM>) configured to engage a screw;
a proximal end (<NUM>) configured to engage instrumentation;
a first half and (<NUM>) a second half (<NUM>) that are connected at the distal end and separately extend to the proximal end (<NUM>);
an instrument insertion feature disposed at the proximal end;
a feature set at the distal end (<NUM>) configured to engage a head of a screw, wherein the screw tower (<NUM>) contains a larger segment (<NUM>) and a shorter segment (<NUM>) removably connectable to the larger segment (<NUM>) by means of reusable tabs (<NUM>),
and wherein the reusable tabs (<NUM>) comprise flexible arms (<NUM>) which contains chevrons (<NUM>) configured to engage the screw for attachment of the tower to the screw, the feature set further including a breakpoint configured to allow the first half and the second half to break apart from each other.