Bone cage with helically arranged fenestrations

Disclosed herein is a bone cage that includes a shaft extending from a head to a tapered tip and including threads disposed on an external surface of the shaft. The cage also includes a plurality of fenestrations defining a row disposed in at least a first helix along at least a portion of the shaft, each of the plurality of fenestrations extend directly through a natural portion of the thread. The cage also includes a cannula positioned within the shaft and extending from an opening in the head to another opening in the tip. Each of the fenestrations are defined by a wall that extends from the exterior of the shaft to the cannula.

TECHNICAL FIELD

The present invention relates generally to orthopedic surgery. More specifically, techniques associated with a bone cage for joint fusion are described.

BACKGROUND

Stress across joints and in particular the sacroiliac joint generally is a common cause of pain including lower back pain. Various types of sacroiliac joint stress, including sacroiliac joint disruptions (i.e., separations) and degenerative sacroiliitis (i.e., inflammation), can result from lumbar fusion, trauma, postpartum, heavy lifting, arthritis, or unknown causes. Sacroiliac joint fixation or arthrodesis is sometimes recommended for skeletally mature patients with severe, chronic sacroiliac joint pain or acute trauma in the sacroiliac joint.

Conventional solutions for stabilizing joints and relieving pain in joints typically include the insertion of an implant, such as a metal screw, rod or bar, laterally across the joint. Even less invasive procedures have drawbacks. One drawback of conventional solutions for sacroiliac joint fixation is the inability to deliver materials, such as bone regenerative materials, antibiotics, steroids, and other joint treatment materials (i.e., for inflammation or infections), to the bones through implants and an implantation procedures that is minimally invasive. Another drawback of conventional implants for sacroiliac joint fixation is that they do not allow for bone growth into and through the implant for true fusion of the joint. Finally, conventional implantation solutions do not provide methods for delivering such joint stress treatment materials through the implant at a later time (i.e., post-implantation).

SUMMARY

In accordance with various embodiments, a bone cage may include a shaft extending from a head to a tapered tip and including threads disposed on an external surface of the shaft. The cage also includes a plurality of fenestrations defining a row disposed in at least a first helix along at least a portion of the shaft, each of the plurality of fenestrations extend directly through a natural portion of the thread. The cage also includes a cannula positioned within the shaft and extending from an opening in the head to another opening in the tip. Each of the fenestrations are defined by a wall that extends from the exterior of the shaft to the cannula.

In accordance with various embodiments, a bone cage may include a shaft extending from a head to a tapered tip and including threads disposed on an external surface of the shaft. The bone cage can also include cannula positioned within the shaft defined by a wall forming the shaft. The cannula extends from an opening in the head to another opening in the tip. The bone cage can also include a plurality of helical rows of fenestrations with each row having three or more fenestrations, wherein each of the fenestrations extends through deferent portions of the threads on the shaft to the cannula and each of the plurality of helical rows extends more longitudinally than circumferentially.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative examples described in the detailed description, drawings, and claims are not meant to be limiting. Other examples may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are implicitly contemplated herein.

Techniques for joint fusion are described, including systems, apparatuses and processes for fusing a joint. Systems and apparatuses for fusing a joint include a cage (i.e., a cannulated cage), a tissue protector assembly, a guide pin, a depth gauge, a cannulated drill bit (e.g., an adjustable cannulated drill bit that employs a stop collar), a driver, a parallel spacer instrument, and a plunger distance tool. As used herein, the term “cannulated” refers to having a cannula, or a hollow shaft. In some examples, the cage may be inserted or implanted into tissue (e.g., bone, cartilage, or other tissue in the joint). As used herein, the term “implant” or “implantation” refers to inserting or insertion into a part of a body. For example, a bone cage may be implanted into a joint (e.g., a sacroiliac joint). In some examples, the cage may have a cannula and radial fenestrations in which therapeutic materials may be packed. Such therapeutic materials may include osteogenic compounds (e.g., bone morphogenetic protein, or other osteogenic compounds that may ossify tissue in the joint), osteoconductive materials (e.g., demineralized bone, hydroxyapatite, or other material that promotes bone growth), antibiotics, steroids, contrast materials, or other materials that may beneficial to fusing the joint, treating inflammation or other conditions in the joint, or enabling the visualization of the area within and adjacent to an implanted bone cage. In some examples, the bone cage may be a screw or screw type device having threads. In some examples, the screw may have one or more rows or groups of helical fenestrations along the wall (i.e. the shaft of the cage defining the cannula) of its shaft to allow the material packed inside the cannula of the cage to contact (e.g., touch, seep into, affect, communicate with, or otherwise physically contact) tissue adjacent to, surrounding, or even within, the cage. In some examples, various tools may be used to insert a cage into a location on a joint, and to prepare the location for the insertion procedure. Such tools may include an implantation assembly, which may comprise a tissue protector; a guide pin; a depth gauge; a cannulated drill bit; a driver; a parallel spacer instrument; a packing plunger, which may comprise a packing tube, a plunger and a loading port; a plunger distance tool; and other tools.

In some examples, a guide pin may be inserted first into a joint at a desired location, in a lateral position across the joint. In some examples, a tissue protector assembly may be used, along with the guide pin, to guide the preparation (i.e., drilling) of a pilot hole as well as to guide insertion of a cannulated cage or other implant while forming a barrier between the preparation site and the surrounding tissue. In some examples, a cannulated drill bit may be used with the tissue protector and/or guide pin to drill the pilot hole. In some examples, a driver or screw driver may be used to insert the cage into the pilot hole. The terms “driver” and “screwdriver” are used herein interchangeably to refer to a tool with a tip configured to engage the head of a screw or similar device, the tool being useful for rotating a screw or otherwise manipulating the screw, to drive a screw or, in this, case a cage into place in a joint. In some examples, a parallel spacer device may be used to space another guide pin in preparation for insertion of another cage. In some examples, a packing plunger assembly may be used to pack the cage with the above-mentioned materials. The packing plunger may be used to pack materials into the cage either or both pre- and post-insertion of the cage into the joint, and may be used with or without the tissue protector assembly.

FIGS. 1A-1Cillustrate a side view, a perspective view, and a cross-section view, respectively, of an exemplary bone cage for joint fusion with end views shown inFIGS. 1D-1E. In accordance with various embodiments, cage100includes head102, tip104, one or more groups of helical fenestrations (e.g., fenestration groups107-110), threads112, and tapered end120. Like-numbered and named elements in these views may describe the same or substantially similar elements. In some examples, cage100may be fabricated, manufactured, or otherwise formed, using various types of medical grade material, including stainless steel, plastic, composite materials, or alloys (e.g., Ti-6Al-4V ELI, another medical grade titanium alloy, or other medical grade alloy) that may be corrosion resistant and biocompatible (i.e., not having a toxic or injurious effect on tissue into which it is implanted). In some examples, threads112may be a helical ridge wrapped around an outer surface of cage100's shaft. In some examples, cage100may be cannulated having a cannulated opening124formed by a hollow shaft that extends from head102to tip104. Cage100may vary in length (e.g., ranging from approximately 25 mm to 50 mm, or longer or shorter) to accommodate size and geometric variance in a joint. Other dimensions of cage100, including major132and minor133diameters of threads112(see, e.g.,FIG. 1B), also may vary to accommodate size and geometric variance in a joint. In one example, head102may be 9.5 mm in diameter and threads112may have a major diameter132of 9 mm and a minor (i.e., root) diameter133of 7.4 mm. In other examples, head102may have a different diameter and threads112may have different major132and minor133diameters. In some examples, an outer surface of cage100's shaft may taper from head102to tapered end120, and thus threads112also may taper (i.e., be a tapered thread) from head102to tapered end120(e.g., having a range of major and minor diameters from head102to tapered end120). In some examples, the tapering of threads112, as well as tapered end120, aids in guiding the cage through a pilot hole. In other examples, head102and threads112may be sized to fit within a tool or instrument, for example, a tissue protector400, as described below.

In some examples, cage100's hollow shaft, or cannula, may be accessed (i.e., for packing material into) through an opening124in head102. In some examples, head102may have a flat or partially flat surface (e.g., pan-shaped with rounded edge, unevenly flat, or other partly flat surface). In other examples, head102may have a different shape (e.g., dome, button, round, truss, mushroom, countersunk, oval, raised, bugle, cheese, fillister, flanged, or other cage head shape). In some examples, the opening in head102may have a receiving apparatus for a torque applying tool such as driver. The driver may be flat head, Phillip's head, square head, hexagonal, head or any similar shape suitable to receive a tool and apply torque therefrom. In one example, the torque applying tool may be a driver having a TORX® or TORX®-like shape (i.e., six-point or six-lobed shape) (seeFIG. 1D) configured to receive the tip of a TORX® or TORX®-like screwdriver (e.g., driver902). For example, cage100may include head grooves118a-118fwhich may start at head102and extend linearly into the cannula of cage100to receive complementary lobes on the end of a screwdriver. For a TORX® or TORX®-like opening there may be six (6) total head grooves, including, for example, head grooves118a-118f, to receive the complementary lobes on the tip of a TORX® or TORX®-like driver. In some examples, as shown inFIG. 1C, the opening in head102may be contiguous with, and form a top end of, cage100's cannula. For example, the opening may provide access to the cannula, for example, to pack material into the cage. The opening may also include a chamfer119providing a lead-in for a tool into the head grooves.

In accordance with various embodiments, the bone cage100has a length and a diameter forming an aspect ratio between the two. In various examples, the aspect ratio of the length to the diameter is greater than or equal to 5 to 1½. In one example, the aspect ratio of the length to the diameter is between 5 to 1½ and 3 to 2½. In one embodiment, the aspect ratio is 25 mm long to 9 mm diameter or about 2.7.

As described herein, the therapeutic materials may include osteogenic compounds (e.g., bone morphogenetic protein, or other osteogenic compounds that may ossify tissue), osteoconductive materials (e.g., demineralized bone, hydroxyapatite, or other material that promotes bone growth), antibiotics, steroids, contrast materials, or other materials that may be beneficial to fusing the joint, treating inflammation or other conditions in the joint, or enabling the visualization of the area within and adjacent to the cage. For example, an osteogenic compound, such as bone morphogenetic protein or other compounds, may be packed into cage100's cannula such that when cage100is inserted into a joint or traverses through a joint (e.g., a sacroiliac joint), the osteogenic compound, for example through fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h), may come into contact with tissue in the joint adjacent to or surrounding cage100, and ossify the tissue to fuse the joint across and through the cage. In some examples, the osteogenic compound may enter the joint and may fill the joint, partially or entirely. In other examples, an osteoconductive material, such as demineralized bone or hydroxyapatite or other materials may be packed into cage100's cannula. When cage100is inserted into a joint (e.g., the joint between ilium I and sacrum S), the osteoconductive material may come into contact with tissue in the joint adjacent to or surrounding cage100, for example through fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h), and promote bone growth into the cage and the joint to fuse the joint across and through the cage. In still other examples, a substance for treating sacroilitis, such as steroids or antibiotics or other substances, may be packed into cage100's cannula such that when cage100is inserted into the joint, the substance may come into contact with tissue in the joint adjacent to or surrounding cage100, for example through fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h), and treat the inflamed joint tissue. In yet other examples, a contrast material may be packed into cage100's cannula such that, when cage100is inserted into the joint, the contrast material within cage100, and in some examples absorbed by tissue adjacent to or surrounding cage100, may be viewed using visualization techniques (e.g., x-ray, fluoroscope, ultrasound, or other visualization technique). In still other examples, different materials may be packed into cage100for different purposes. In yet other examples, the above-described materials may also come into contact with tissue adjacent to, or surrounding, cage100through an opening at tip104. As described herein, cage100may be packed with material prior to being inserted into the joint, and may also be packed after insertion into the joint. Also as described herein, such materials may be packed into cage100using a packing plunger1102(see, e.g.,FIG. 9).

In some examples, fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h) may provide therapeutic openings in cage100's shaft to enable material packed inside cage100to come into contact with surrounding or adjacent tissue (e.g., bone, cartilage, or other tissue in the joint) when cage100is implanted. In various examples, the fenestration opening is 1 mm to 4 mm. In another example, the fenestration opening is 2 mm to 3 mm. In a preferred example, the fenestration opening is about 2½ mm. Additionally or alternatively, in various examples, the fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h) may be shaped to provide additional cutting edges or edges suitable to clean threads formed by the tip120. In various examples, fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h) are substantially circular. In other examples, the fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h) are oblong (e.g., substantially oval, substantially elliptical, or other suitable shapes). In other examples, fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h) are shaped differently (e.g., rectangular, rounded rectangular, squared, triangular, or other suitable shapes).

In accordance with some embodiments, the bone cage100is manufactured by drilling fenestrations through the exterior of the device prior to cutting threads into the device. In this way, the location of the threads does not bias or effect the location of the fenestration in the bone cage100. Additionally, the device can be free of other features such as grooves, slots or the like, that locate the fenestrations and tend to weaken the strength of the cage. In some examples, the fenestrations are consistently spaced with an omni-directional orientation or a generally omni-directional orientation that strengthens the cage100.

In accordance with various embodiments, each cage may have an omni-directional orientation of the fenestrations along the cage length or across an individual section of the cage. An omni-directional orientation is one in which, along a fenestrated segment of a cage, a portion of the opening of the fenestrations are located across all radial directions of the cage. With the various openings of the fenestrations located in all radial directions, the cage can be implanted into the bone without regard to rotational alignment with the portion of the bone that is targeted for therapeutic treatment. Thus, in embodiments incorporating omni-directional orientation, a doctor does not need to orient the cage in the bone in order to optimize bone growth. The specific position of the holes can be located, in one example, in an organized manner (e.g., a pattern) or, in another example, they can be random. In various embodiments discussed in more detail below, the embodiments can include an omni-directional orientation. In other embodiments, the embodiments discussed herein can be formed without an omni-directional orientation. For example, along a set length of the fenestrated portion of the cage (i.e., the omni-directional segment length), e.g., 9 mm length of the cage, there is a portion of a fenestration opening in every radial direction. In various examples, a limited number of fenestrations are longitudinally aligned. For example, as shown inFIGS. 1A-C, fewer than three fenestrations have the same radial direction along the length of the cage or the segment. In one example, the cage has an omni-directional segment length that is approximately the same as the diameter of the cage. In another example, the omni-directional segment length is approximately the same as half the diameter of the cage. In another example, the omni-directional segment length is approximately the same as two times the diameter of the cage. In various examples, the omni-directional segment length is from about ½ the diameter of the cage to two times the diameter of the cage.

In accordance with various embodiments, each cage may have a generally omni-directional orientation of the fenestrations along the cage length or across an individual section of the cage. A generally omni-directional orientation is one in which, along a fenestrated segment of a cage, a portion of the opening of the fenestrations are located across substantially all radial directions of the cage. With the various openings of the fenestrations located in substantially all radial directions, the cage can be implanted into the bone with minimal regard to rotational alignment with the portion of the bone that is targeted for therapeutic treatment. Thus, in embodiments incorporating generally omni-directional orientation, a doctor has limited need to orient the cage in the bone in order to optimize bone growth. The specific position of the holes can be located, in one example, in an organized manner (e.g., a pattern) or, in another example, they can be random. In various examples, along a set length of the fenestrated portion of the cage (i.e., the generally omni-directional segment length), e.g., 9 mm length of the cage, there is a portion of a fenestration opening in substantially every radial direction. In various embodiments, the segment lengths for generally omni-directional orientation can be similar to the omni-directional orientation discussed above. Openings located in substantially all radial directions of the cage correspond to those that allow a doctor to place the screw without regard to the rotational orientation or alignment of the cage. Meaning, the therapeutic material is adequately delivered in each radial direction from the cage to the bone to achieve the goals of treatment regardless of the rotational orientation of the screw. In one example, fenestrations provide openings around 75-100% percent of the radial directions of the shaft but are distributed throughout the longitudinal length of the segment. In another example, the shaft includes longitudinal continuous strips of un-fenestrated portions that are present along the segment. The strips may have radial angles of less than 10°. In another example, the strips may have radial angles of less than 5°.

In accordance with some embodiments, the bone cage100is manufactured by drilling fenestrations through the exterior of the device prior to cutting threads into the device. In this way, the location of the threads does not bias or effect the location of the fenestration in the bone cage100. Additionally, the device can be free of other features such as grooves, slots or the like, that locate the fenestrations and tend to weaken the strength of the cage. In some examples, the fenestrations are consistently spaced with an omni-directional orientation or a generally omni-directional orientation that strengthens the cage100. The consistently spaced fenestrations allow for delivery of the therapeutic materials through the fenestrations to the bone in generally evenly distributed intervals. Generally evenly distributed intervals corresponds to intervals that allow sufficient therapeutic materials distribution to adequately treat the bone.

In accordance with various embodiments, each cage may have one or more helical rows of fenestrations. For example, second, third and fourth sets of fenestrations (e.g., fenestrations107,108,109,110) are disposed along a portion of the shaft from head102to tapered end220, along the wall of cannula224. In one example, these helical arrangements are omni-directional. Each different set of helical fenestrations is considered a new helical start. In one example, the starts can be tightly grouped together (e.g., two starts can be on the same half of the cylinder of the shaft) or alternatively, the starts can be uniformly spaced around the cylinder (e.g., two starts would be approximately 180° apart or four starts would be approximately 90° apart). In still other examples, each set of helically disposed fenestrations may include more or fewer fenestrations. In yet other examples, each set of fenestrations may be disposed at greater or lesser intervals. As illustrated inFIGS. 1A-1Eand in some examples, cage100may include four helixes of fenestrations (e.g., fenestrations107-110) disposed helically (i.e., in a helical row along a portion of the cage from head102to tapered end120). For example, fenestrations107may be disposed helically along the cage100, and fenestrations108may start along another side approximately 90° from fenestrations107.

In accordance with various embodiments, the wall of the cage includes three or more helically positioned fenestrations or openings (e.g., at least three of any of fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h). The helix is defined by the position of the fenestrations relative to one another as the different fenestrations are variously located down some portion of the cage shaft from head102to tapered end120, as shown by example inFIGS. 1A-1C. It should be noted that the helix is not defined by some abstraction in which various fenestrations can be connected by some envisioned abstract helix, but instead the fenestrations themselves clearly define the helix, as a person of ordinary skill in the art would recognize the various groupings of fenestrations as defining the shape and form of a helix.

The shape of the helix can be defined by the relative location and progression of each of the fenestrations along the shaft of the cage. These relative locations can be defined according to the longitudinal separation L and the angular separation A. The angular separation A between two adjacent fenestrations also corresponds to the circumferential gap between the two adjacent fenestrations. The overall helix can also be defined by the helix angle HA (seeFIG. 1C) as measured from a plane or line perpendicular to the axis SA of the bone cage to the direction of the helix defined by the position of the fenestrations running along the bone cage. In some examples the helix angle is sufficiently large that the helix does not pass through the same fenestration twice. In accordance with various examples, the helix angle is greater than 15° and less than 90°. In one embodiment, the helix angle is steep being between about 45° and about 85° (see e.g. HA1). This angle allows for multiple helixes along the cage. In other embodiment, the helix angle is shallow being between about 15° and 45° (See e.g. HA2). In a preferred example, a single helix angle is about 28°. In another example, a cage has a double helix with helix angles that are about 40°. As used herein and illustrated inFIGS. 1A and 1B, the longitudinal separation L corresponds to the axial separation or distance between adjacent fenestrations in a helix along the axis SA of the cage100. For example, the longitudinal separation of one fenestration relative to another is the axial distance between the centers (i.e., individual axes) of each of the fenestrations. As used herein and illustrated inFIGS. 1B and 1E, the angular separation A corresponds to the angle measured in the plane that is perpendicular to axis SA. For example, the angular separation A of one fenestration relative to another is the angle measured between a radius extending from axis SA through the center of one fenestration and a radius extending from axis SA through the center of an adjacent fenestration.FIG. 1Eillustrates a particular example of the angular separation of fenestration108hrelative to fenestration108g. Here fenestration108hhas an angular separation A relative to fenestration108g. As shown in this example, angular separation A is measured between the axes108A1and108A2with the axes108A1and108A2being different axis R intersecting with axis SA. As used herein and illustrated inFIGS. 1B and 1E, the circumferential gap C corresponds to the circumferential separation that a first fenestration passes through the cage wall relative to the distance around the cage wall in which the adjacent fenestration in the helix passes through the cage wall. This is measured along the arc of the wall in a plane that is perpendicular to the axis SA. For example, the wall measured for the circumferential separation C may be the interior surface of the shaft that defines the cage cannula.

In accordance with various embodiments, there is cage shaft material that extends between adjacent fenestrations. As illustrated by way of example inFIG. 1A, bridges111connects fenestrations109(e.g., bridge111aconnects fenestration109ato109b), bridges106connects fenestrations108, and bridge105connects fenestrations107. While the bridges form part of the shaft as a whole, the bridge itself is in reference to the material directly between adjacent fenestrations. In accordance with various embodiments, the group of bridges (e.g., bridges111a-111f) forming the shortest connection between adjacent fenestrations (e.g.,109a-109g) defines the helix (e.g., helix start109).

In accordance with various embodiments, a helix on cage100is defined by a row of fenestrations (e.g., rows107,108,109, or110) in which adjacent fenestrations are separated from one another by a longitudinal separation L and an angular separation A. In various examples, each helix of fenestrations has a constant pattern where the longitudinal separation L and the angular separation A between adjacent fenestrations are constant along the length of the helix. In other examples the pattern is not constant but instead one or both of the angular separation A and the longitudinal separation L varies (increases or decreases) at a constant rate.

In accordance with various examples, the angular separation between adjacent fenestrations in a helix is greater than 0° such that a row of fenestration defines a helix as opposed to an axial line along the length of the cage100. In one example, the angular separation is less than 120°. In one example, the angular separation is less than 90°. In one example, the angular separation is less than 60°. In one example, the angular separation is less than 45°. In one example, the angular separation is less than 20°. In one example, the angular separation is less than 10°. In a preferred example, the angular separation is between about 5° and 15°. In various examples, the angular separation from a first fenestration (e.g.,110a) proximal to the head102to a second fenestration (e.g., fenestration110b) closer to the tip104is such that the helix defined by the fenestration wraps around the exterior of the cage100in the same direction as the threads112. In some examples, the angular separation A between adjacent fenestrations is sized such that the lead (i.e., the axial advance of a helix during one complete turn around the circumference of the cage) of the fenestration helix is greater than the length of the cage.

In accordance with various embodiments, an angular segment of the cage100is an angle swept from a radial direction extending from the center line SA. This angular segment of the cage100may be considered a pie region of the cage100. Each pie region may have about the same number of holes (e.g., within plus or minus one hole). For example, a 90° angular segment of the cage100can have 8-9 full fenestrations. In a preferred embodiment, the cage100includes 5 or more substantially equal angular segments with each of the angular segments having approximately the same number of fenestrations such that the cage100is operable to deliver therapeutic material in each direction of the angular segments in approximately the same amount or rate. In another embodiment, each angular segment has approximately the same cross sectional area of fenestrations such that the cage100is operable to deliver therapeutic material in approximately the same amount or rate.

In accordance with various examples, the longitudinal separation L between adjacent fenestrations in a helix is a distance greater than zero (0) such that a row of fenestration defines a helix as opposed to a circumferential line along the circumference of the cage100. In one example, as illustrated inFIGS. 1A and 2B, the longitudinal separation L between adjacent fenestrations is greater than the pitch of the threads. In one example, the longitudinal separation L between adjacent fenestrations is less than the pitch of the threads. In one example, the longitudinal separation L between adjacent fenestrations is approximately the same as the pitch of the threads. In one example, as illustrated inFIG. 1A, the longitudinal separation L between adjacent fenestrations is approximately the same as or smaller than two times the diameter of the fenestration (e.g., the longitudinal separation of fenestration110arelative to110bis less than two times the diameter of fenestration110a). In some examples, the longitudinal separation L between adjacent fenestrations is less than the diameter of the fenestration, but in such examples, the angular separation would be large enough as to form a bridge between fenestrations. In some examples, as illustrated inFIG. 2B, the longitudinal separation L between adjacent fenestrations is larger than two times the diameter of the fenestration. In some examples, the longitudinal separation L between adjacent fenestrations is large enough such that the lead (i.e., the axial advance of a helix during one complete turn around the circumference of the cage) of the fenestration helix is greater than the length of the cage.

The circumferential separation C of adjacent fenestrations is related to the angular separation A of the adjacent fenestrations based on the radius of the cage100. For example, on two cages having different diameters but with adjacent fenestrations having the same angular separation A, the larger cage will have a larger circumferential separation C proportional with the increase in radius size of the cage compared to the smaller diameter cage. In accordance with various examples, the circumferential separation between adjacent fenestrations in a helix is greater than zero (0) such that a row of fenestration defines a helix as opposed to an axial line along the length of the cage100. In accordance with various examples, the circumferential separation C between adjacent fenestrations in a helix is less than the diameter of the fenestration. In various examples, the circumferential separation C between adjacent fenestrations in a helix is less than half the diameter of the fenestration. In a preferred example, the circumferential separation C between adjacent fenestrations in a helix is between about one-tenth ( 1/10) and one-third (⅓) of the diameter of the fenestration. In some examples, the circumferential separation C between adjacent fenestrations in a helix is greater than the diameter of the fenestration and less than half the circumference of the cage100.

In accordance with various embodiments, each adjacent fenestration may have a helically extending bridge of material extending therebetween, as discussed above. In some embodiments, the length of the bridge is greater than the thread pitch. In other embodiments, the length of the bridge is less than the thread pitch. In other embodiments, the length of the bridge is less than the diameter of the fenestration. In other examples, the length of the bridge is greater than the diameter of the fenestration. In various examples, the length of the bridge wraps less than a third of the way around the cage. In various examples, the length of the bridge wraps less than a quarter of the way around the cage. In accordance with a preferred embodiment, as illustrated inFIG. 1C, the length of the bridge wraps between one-sixty-fourth ( 1/64) and one-sixteenth ( 1/16) of the way around the cage100.

In accordance with various embodiments, the helix of fenestration on cage100may include any suitable combination of the examples of the longitudinal separation, the circumferential separation, the angular separation and/or the bridge configurations discussed herein. As discussed herein, each cage100can include multiple helixes (i.e., multiple starts to each helix). Each helix can include any suitable combination of the examples of the longitudinal separation, the circumferential separation, the angular separation and/or the bridge configurations discussed herein. In some embodiments, each helix is parallel to the adjacent helixes. In other embodiments, one or more of the helixes has a different profile or characteristics as opposed to the other helixes of fenestrations on the cage100. In various examples, the fenestrations in adjacent helixes do not align longitudinally (i.e., axially) with the fenestrations of the next helix. Such a configuration can allow for a fenestration opening to be located along the entire length of the cage100with each opening located at a different point around the circumference of the cage.

In accordance with the various embodiments, some or all of the fenestrations form openings from the profile of the thread into the cannula. The fenestration openings from the exterior of the cage100to the interior cannula124are defined by generally radially extending passages. In one embodiment the passages are formed as a steep bore with straight cross sectional walls that extend from the thread profile to the cannula. The surface defining the bore from the thread profile to the cannula extends in the generally radial direction. For example, the fenestration may avoid any surfaces or features other than the thread profile that is not radially extending from the cannula to the exterior of the cage100. Meaning the fenestration avoids any surfaces tangential to the circumference of the cage and/or is generally absent a surface that faces in a generally outward direction from the cage. In accordance with the various embodiments, some or all of the fenestrations form openings directly through a natural portion of the thread. As used herein, the natural portion of the thread112includes an uninterrupted profile of the thread. Examples of interruptions in the thread include grooves, slots, flats, shelves or other features machined, molded, cut, or otherwise formed into the threads, that are not actually part of the thread itself but serve another purpose than advancing the cage through the bone. Stated another way, at least some of the fenestrations in each helix discussed above, avoid extending through any grooves, slots, flats, shelves or other features machined, molded, cut, or otherwise formed into the threads, that are not actually part of the thread itself but serve another purpose than advancing the cage through the bone. While in some embodiments, some of the fenestrations may intersect thread interruptions or similar features, in such embodiments, some of the fenestrations can still avoid such intersections allowing the helix to still be defined by those fenestrations that avoid such intersections. By having the fenestrations intersect the threads directly, injected material is permitted to flow around and through the outside of the bone screw, and not just into areas contacting the minor diameter of the screw. In some embodiments, the cage may have multiple leads (e.g. dual starts). As such, the injected material can create two discrete helical sections as it escapes the threads through the fenestrations. By having the fenestrations break through the thread profile, it enables adjacent thread areas (e.g. the two separate thread helixes) to be contacted by a continuum of the injected media. Additionally, by forming the threads such that the fenestrations pass directly through the threads forming a self-tapping feature having sharp edges that cut into the bone while being threaded into place. In accordance with various embodiments, the threads have a crest that is rounded or peaked (e.g. having a point comparable to the root of the thread). In other embodiments, the thread may have a flattened crest.

By having the fenestrations open directly through the otherwise uninterrupted thread profile, the exterior fenestration openings open directly to the bone that supports the threads112inside of the ilium I, sacrum S, or the joint there between. Thus, when therapeutic material is delivered to the bones through the fenestrations (e.g., fenestrations107-110) along the cage100, it is delivered at discrete locations directly to the bone helically along the length of the cage, thus avoiding flow of material into thread interruptions and away from the targeted discrete locations. Also this maintains the cage thread profile along the length of the cage except in the discrete locations of the fenestrations.

In accordance with various embodiments, the fenestrations extend from the cannula124to the exterior of the cage100with groups of fenestrations forming helical paths (e.g.,107,108,109, and110.) The various fenestrations are positioned on the cage and as the cage threads contact the bone structure directly when implanted, the various openings of each of the individual fenestrations open directly onto the bone structure in both major diameters (the peaks) and minor diameters (the valleys of bone structure formed by the threads of the cage. The various openings forming the fenestrations also open directly onto the bone and form helical patterns along the length of the cage such that therapeutic material is delivered to the bone structure directly from the fenestration openings and to the bone in helically arranged discrete locations corresponding to the locations of the various fenestrations.

In various embodiments, the fenestration helixes do not follow the thread helix. In some examples of this, the thread helix has a period that is different and also not a multiple of the fenestration helixes such that the fenestration helixes vary in how they pass through the thread profile, sometimes passing through and centered on the minor diameter of the thread, sometimes passing through and centered on the major diameter, and sometimes centered in between the major and minor diameters.

FIGS. 2A-2Billustrates side views of alternative exemplary cages for joint fusion. Here, cage100includes head102, tip104, fenestrations, threads112, shaft grooves114and tapered end120. Like-numbered and named elements in these views may describe the same or substantially similar elements above. For example, like-named elements inFIGS. 2A-2Bmay describe the same or substantially similar elements at those inFIGS. 1A-1E. Elements with different numerical identifies refer to elements that are substantially different from the embodiments ofFIGS. 1A-1E(e.g., the fenestrations). In various embodiments, the various elements (e.g., threads, fenestrations, cannula, etc.) of the cage100may have one or more of the various characteristics or combinations of characteristics discussed above with regards toFIGS. 1A-1E.FIG. 2Ashows an example of a cage having groups of fenestrations. For example, helix208of fenestrations208a,208b, and208c(with bridges206aand206bthere between) occupy less than half the length of the cage100. In another example, helix109of fenestrations209a,209b,209c, and209d, illustrate a variation in the spacing of the fenestrations as discussed in more detail below.FIG. 2B, as discussed above, illustrates, an alternative example of fenestrations (e.g., fenestrations260a,259a-259c, and258a-258dalong with bridges266a-266band256a-256c)) on the same respective helixes (260,259, and258) with a lower frequency than shown inFIGS. 1A-1E.

As shown in the examples illustrated inFIGS. 1A-1E, the respective angular separation between adjacent fenestration is constant along the length of the cage and/or the length of the helix. Similarly,FIG. 2Billustrates helixes in which the respective angular separation between adjacent fenestration is constant.FIG. 2Aon the other hand illustrates an example having helixes (e.g.,209) in which the respective angular separation between adjacent fenestration is not constant. A variable angular separation is one in which, the angular separation between two adjacent fenestrations in a helix is different that the angular separation between two other adjacent fenestrations in the helix. For example, fenestrations209a,209b,209c, and209dare all in the same helix. However, the angular separation between fenestrations209band209cis different than the angular separation between fenestrations209cand209d. The variations in the angular separations may form a pattern. The variations may be progressively larger. In some embodiments, they may be progressively smaller. In other embodiments, they may increase and then decrease. In other embodiments, they may be irregular in the way they change along the helix(es). In some embodiments, there may be a single variation, and in other there may be multiple variations.

As shown in the examples illustrated inFIGS. 1A-1E, the longitudinal separation between adjacent fenestration is constant along the length of the cage and/or the length of the helix. Similarly,FIG. 2Billustrates helixes in which the longitudinal separation between adjacent fenestration is constant.FIG. 2A, on the other hand, illustrates an embodiment having helixes (e.g., fenestrations209) in which the respective circumferential separation, longitudinal separation, or combined helical separation between adjacent fenestrations is not constant. A variable longitudinal separation is one in which the longitudinal separation between two adjacent fenestrations in a helix is different that the longitudinal separation between two other adjacent fenestrations in the helix. For example, fenestrations209a,209b,209c, and209dare all in the same helix. However, the longitudinal separation between fenestrations209band209cis different than the longitudinal separation between fenestrations209cand209d. The variations in the longitudinal separations may form a pattern. The variations may be progressively larger. They may be progressively smaller. They may increase and then decrease. They may be random in the way they change. In some examples there may be a single variation, in other examples there may be multiple variations. Such variations are selected so that they still result in the adjacent fenestrations remaining on the same helix, because as the longitudinal separation may change, the angular or circumferential separation may proportionally change to maintain a helical relationship between fenestrations.

In accordance with various embodiments, each adjacent fenestration may have a bridge of material extending there between, as discussed above. In various examples the length of the bridge can change. For example, as shown inFIG. 2A, the bridge211bis a smaller length than the next adjacent bridge down the length of the cage bridge211c. In accordance with various embodiments, the helix of fenestration on cage100may include any suitable combination of the elements or characteristics of the longitudinal separation, the circumferential separation, the angular separation and/or the bridge configurations in the various examples discussed herein (e.g., examples shown inFIGS. 1A-1E or 2A-2Bor any discussed above).

In some examples, tip104may be disposed on tapered end120. In some examples, tip104may provide another opening for material packed inside the shaft to come into contact with surrounding or adjacent tissue. In some examples, this opening may be circular, with the same or similar diameter as the cannula of cage100. In other examples, the opening may be smaller in diameter than the cannula of cage100. In some examples, the opening in tip104may be contiguous with, and form an end of, cage100's cannula. In some examples, tapered end120may aid in guiding cage100into a pilot hole. In various embodiments the tip begins to form threads (i.e., tap threads) into the predrilled hole. The tip includes one or more flutes (e.g., flutes117a-c) extending through the threads. The flutes cut through the threads but not the wall defining the cannula124.

In some examples, openings in cage100, including fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h), and tip104, may enable cage100to deliver materials to bone and other joint tissue adjacent to, or surrounding, cage100, for example, to regenerate bone or treat inflammation, infection, or other ailments, in the joint. For example, cage100may have a cannula in which such materials may be packed, as described herein. After being packed, cage100may be implanted (i.e., inserted) into or across a joint, and such therapeutic materials may be delivered from cage100through fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h) or other openings (e.g., in head102or tip104of cage100) and to a joint. In some examples, the above-described materials may fill a joint, partially or entirely, after entering the joint through fenestrations (e.g., fenestrations107a-107h,108a-108h,109a-109h, and/or110a-110h).

FIG. 1Dillustrates a top view of an exemplary cage for joint fusion. In accordance with various examples, such as those illustrated inFIG. 1D, end122includes head102, shaft124, openings126,128, head grooves118a-118fand head diameter130. Like-numbered and named elements in these views may describe the same or substantially similar elements above. In some examples, head102may be circular with head diameter130. In some examples, head diameter130corresponds to the diameter of a cannula of a tissue protector (e.g., tissue protector404). In other embodiments, head102may be shaped differently (e.g., triangular, hexagonal, or other shapes not shown). In some examples, opening126may be disposed at head102, and opening128may be disposed at tip104(see e.g.,FIG. 1E). In some examples, the diameters of openings126and128may be the same or similar. In other examples, the diameter of openings126may be different from the diameter of opening128.

In some examples, cannula124may extend uninterrupted from head102to tip104. In some examples, cannula124may be configured to fit over a guide pin, as described herein. In some examples, cannula124also may be configured to receive and hold material (e.g., osteogenic compounds, osteoconductive materials, antibiotics, steroids, contrast materials, or other materials that may beneficial to fusing the joint, treating inflammation or other conditions in the joint, or enabling the visualization of the area within and adjacent to the cage, as described herein).

FIG. 1Eillustrates a bottom view of an exemplary cage for joint fusion. In accordance with various embodiments, bottom end includes tip104, fenestrations (e.g., one or more of107h,108h,109h,110h) tapered end120, cannula124, opening128, head diameter130and major diameter132. Like-numbered and named elements in these views may describe the same or substantially similar elements above. In some examples, opening128are disposed at tip104and the end of cannula124. In some examples, head diameter130may be larger than major diameter132. In various examples, major diameter132in turn may be larger than a minor133(i.e., root) diameter.

In some examples, cages100(e.g., shown inFIGS. 1A-1EorFIGS. 2A-2B) can be configured to fit or slide within a tissue protector (e.g., tissue protector404) and/or over a guide pin (e.g., guide pin418) into a joint. In other examples, cages100may be formed differently and are not limited to the examples described.

FIG. 3illustrates an exemplary guide pin418. In some examples, guide pin418may be a medical grade sterile metal pin (e.g., Kirschner wire, Steinmann pin, or other metal pin) suitable for use in medical procedures. In some examples, guide pin418may be used for alignment and guidance of a tissue protector (e.g., tissue protector404), an implant (e.g., a cage or other implant), and other tools into the ilium I, the sacrum S or the joint there between. The guide pin418can be set into the patient via twisting, hammering, pressure or any other suitable method. In a particular example, mallet417drives the guide pin418into the ilium and/or the sacrum. In some examples, guide pin tip410may form a trocar for introducing tissue protector assembly400into a bone.

FIG. 4Aillustrates an embodiment of a depth gauge602for determining the depth of a guide pin to be inserted into the ilium I and/or sacrum S. In various embodiments, depth gauge602includes depth markings604, channel606, and distal contact surface607. In various examples, the channel606is formed along an exposed wall609of the depth gage. The channel606transitions into an enclosed channel through a lower body portion611. The contact surface607is located on the distal end of the lower body portion611and is suitable to contact the ilium I. The guide pin418may then be slid into the depth gauge602to the desired depth as measured on the depth markings604. In some examples, depth gauge602may be configured to determine the depth in which guide pin418is inserted into a bone and/or joint. In some examples, depth gauge602may include depth markings604, which can measure the depth in which the guide pin418is driven into the ilium. In some examples, depth markings604may indicate a range of 25-65 mm depths. In other examples, depth gauge602may have different depth markings, and thus indicate a different range of depths. The number in depth markings604that corresponds to the location of the end of guide pin418may indicate the depth of guide pin418. In other examples, depth markings604can indicate a different depth that may correspond and be calibrated to the depth of guide pin418(e.g., depth markings604may indicate a desired drilling depth for a pilot hole, a depth of a cage to be implanted, or other depth that is associated with the depth of guide pin418, and may thus be measured against the depth of guide pin418). In still other examples, depth gauge602may include more or fewer elements and is not limited to the examples described.

FIGS. 5A and 5Billustrate a tissue protector assembly400. The tissue protector assembly may include sleeve404and handle412. In some examples, tissue protector sleeve404may include a tissue protector head414, and tissue protector tip416. In some examples, sleeve404has a hollow shaft415having a close fit to one or more of the depth gauge602, the cage100, and or a drill700. In some embodiments, the guide pin481may be utilized with a guide pin sleeve. The guide pin sleeve can receive into the guide pin sleeve. The guide pin sleeve can then be inserted into the tissue protector. In various embodiments, the guide pin sleeve includes a close tolerance to the interior of the channel415of the tissue protector so that the guide pin is accurately positioned in the tissue protector404. In some embodiments, the guide pin418is centered in the tissue protector400. In other embodiments, the depth gauge602functions as the guide sleeve. In some examples, the outer diameter of pin sleeve (e.g., depth gauge602) shaft is shaped to fit inside the cannula of tissue protector400, which has an internal diameter that may be configured to accommodate tools and implants (e.g., cages100, and the like) having a larger diameter than a guide pin. For example, the diameter of tissue protector404's cannula415may correspond to (i.e., be sized to fit) the head or outer diameter on an implant (e.g., cages100). In some examples, the internal surface of tissue protector400may be configured to guide an implant (e.g., cage100) inserted into tissue protector400from tissue protector head414and through to tissue protector tip416.

In some examples, tissue protector tip416may have spikes, teeth, wedges, or other structures, to engage a bone. As shown, tissue protector tip416is engaged with an ilium (i.e., its spikes, teeth, wedges or other structure for engaging a bone, are embedded in the ilium). In some embodiments, the tissue protector tip416does not embed into the bone but merely increases friction such that the tissue protector tip416does not slip on the exterior of the bone. In other examples, tissue protector assembly400may be formed differently and is not limited to the examples described.

FIG. 5Billustrates an exemplary tissue protector assembly placed over a guide pin. Here, diagram420may include tissue protector sleeve404, handle412, tissue protector head414, tissue protector tip416and guide pin418and depth gage602(functioning as a guide pin sleeve). Like-numbered and named elements in this view may describe the same or substantially similar elements as in previous views (e.g.,FIG. 4A).

FIGS. 6A and 6Billustrates a side view of an exemplary cannulated drill bit and for drilling a pilot hole for insertion of a cage for joint fusion. Here, cannulated drill bit700may include cutting tip702, body704, and shank709. As used herein, “drill bit” refers to any cutting tool configured to create substantially cylindrical holes, and “shank” refers to an end of the drill bit, usually the end opposite the cutting tip, configured to be grasped by a chuck of a drill, handle or other torque applying device. In some examples, cannulated drill bit700may be configured to drill a pilot hole to a predetermined depth. For example, cutting tip702may be configured to cut cylindrical holes into a bone and/or joint when torque and axial force is applied to rotate cutting tip702(i.e., by a drill). In some examples, cannulated drill bit700may be adjustable, and thereby configured to drill a range of depths using depth markings. The outside diameter of cannulated drill bit700may be configured to fit within a tissue protector (e.g., tissue protector400). In some examples, the outside diameter may be significantly smaller than the tissue protector400, such that the tissue protector does not provide significant support to the drill bit700or function as the primary locating tool for the drill bit700. In other examples, the tissue protector400may function as the drill guide, providing significant support and locating functionality to the drill bit700by having an inner diameter that is substantially the same size as the outer diameter of the drill bit700. The variance in sizes being sufficient to allow the drill bit700to slide and rotate within the tissue protector.

In some examples, a desired drilling depth (i.e., depth of a pilot hole) may be the same or similar to the depth of a guide pin that has been inserted into a bone and/or joint. In other examples, the desired drilling depth may be offset (i.e., less deep) by a predetermined amount (e.g., a few millimeters or other offset amount). For example, if a guide pin has been inserted 40 mm deep into the sacroiliac joint, a corresponding desired drilling depth for the pilot hole may be 40 mm, or it may be 40 mm minus the predetermined offset may be selected (i.e., if the predetermined offset is 3 mm, then the desired drilling depth in this example would be 37 mm).

The cannulated drill bit700includes cannula714. In some examples, cannula714are sized to fit over a guide pin (e.g., guide pin418). A driver handle906may receive the shank709allowing a user to apply a torque to the drill bit700. The drill bit700may be slid down over the guide wire418thereby accurately locating the drill bit700based on the insertion location of the guide wire418into the bone. Tissue protector400, particularly the sleeve404thereof protects the tissue surrounding the drill site from being damaged by the drilling action. The drill may than form hole through one or more bones (e.g., ilium I and/or Sacrum S).

FIGS. 7A and 7Billustrate an exemplary driver902for inserting a cage100for joint fusion. Driver assembly900includes driver902, mating tip904, driver handle906, tissue protector404, handle412, and tissue protector head414. In some examples, driver902may be configured to drive a cage (e.g., cages100) into a bone and/or joint. In some examples, driver902may have a shaft configured to fit or slide within tissue protector404. In some examples, mating tip904may be shaped to engage (i.e., fit) a head of a cage (e.g., head102). For example, driver902may be a TORX® driver and mating tip904may be shaped to fit a TORX® head cage (e.g., with a six-point or six-lobed shape). In other examples, mating tip904may be shaped differently to engage suitable types of cages (e.g., PHILLIPS™ (i.e., having a cruciform or cross shape with four lobes), slot, flat, Robertson, hex, or other type of cages). In some examples, driver handle906may be used to turn driver902, and consequently turn a cage engaged by mating tip904. In some examples, driver902may be a manual driver. In other examples, driver902may be powered (i.e., electrically). In some examples, driver902also may be ratcheting or torque-limited. In some examples, driver handle906may be formed separately from driver902's shaft and driver tip904. In some examples, handle906may be configured to be removably coupled with various types of drivers (e.g., TORX®, PHILLIPS™, slot, flat, Robertson, hex, or other types of cage drivers). In other examples, driver902and driver handle906may be formed differently, and are not limited to the examples shown and described. The cage100includes a cannula that slides over the guide wire418and into tissue protector sleeve404. The driver902forces the cage100down sleeve404until contact is made with the bone. Then a torque is applied to cage100by the handle906causing the cage to twist into the bone.

FIG. 8illustrates a side view of an exemplary parallel spacer instrument300for placement of another guide pin418b.FIG. 9illustrates a second pin placed parallel to the first setup. This is accomplished by running the additional pin418bthrough the spacer block as shown inFIG. 8. In some examples, guide pin418may still be in place within tissue protector400. Once the parallel spacer instrument300is placed on tissue protector400, a next guide pin418bis inserted through the parallel spacer reaching down to engage the bone (e.g., an ilium).

FIG. 9illustrates a perspective view of an exemplary packing plunger500placed in a dispensing tube502. In some examples, dispensing tube502and plunger500work together to dispense therapeutic material into the cage located in the bone (e.g., ilium and/or sacrum). The plunger and the dispensing tube dispense various therapeutic materials (e.g., liquids, gases, gels, or other materials. As described herein, such therapeutic materials include osteogenic compounds (e.g., bone morphogenetic protein, or other osteogenic compounds that may ossify tissue in the joint), osteoconductive materials (e.g., demineralized bone, hydroxyapatite, or other material that promotes bone growth), antibiotics, steroids, contrast materials, or other materials that may beneficial to fusing the joint, treating inflammation or other conditions in the joint, or enabling the visualization of the area within and adjacent to the cage. In some examples, plunger500may be depressed to dispense material from dispensing tube502, for example, into a cannulated cage (e.g., cages100), which may in turn deliver said material into a joint, as described above, through the fenestrations discussed above.