Patent Description:
The integrity of the spine, including its subcomponents like the vertebral bodies and intervertebral discs that are well known structural body parts forming the spine, are key to a patient's health. These parts may become crushed or damaged as a result of trauma or injury, or damaged by disease (e.g., by tumor, autoimmune disease) or as a result of wear over time or degeneration caused by the normal aging process.

In many instances, one or more damaged structural body parts can be repaired or replaced with a prosthesis or implant. For example, specific to the spine, one method of repair is to remove the damaged vertebra (in whole or in part) and/or the damaged disc (in whole or in part) and replace it with an implant or prosthesis. In some cases, it is necessary to stabilize a weakened or damaged spinal region by reducing or inhibiting mobility in the area to avoid further progression of the damage and/or to reduce or alleviate pain caused by the damage or injury. In other cases, it is desirable to join together the damaged vertebrae and/or induce healing of the vertebrae. Accordingly, an implant or prosthesis may be configured to facilitate fusion between two adjacent vertebrae. The implant or prosthesis may be placed without attachment means or fastened in position between adjacent structural body parts (e.g., adjacent vertebral bodies).

Typically, an implant or prosthesis is secured directly to a bone structure by mechanical or biological means. One manner of spine repair involves attaching a fusion implant or prosthesis to adjacent vertebral bodies using a fixation element, such as a screw. Most implants and their attachment means are configured to provide an immediate, rigid fixation of the implant to the implantation site. Unfortunately, after implantation the implants tend to subside, or settle, into the surrounding environment as the patient's weight is exerted upon the implant. In some cases, this subsidence may cause the rigidly fixed attachment means to either loosen, dislodge or potentially damage one or more of the vertebral bodies.

Several known surgical techniques can be used to implant a spinal prosthesis. The suitability of any particular technique may depend upon the amount of access available to the implant site. For instance, a surgeon may elect a particular entry pathway depending on the size of the patient or the condition of the patient's spine such as where a tumor, scar tissue, or other obstacle is present. Other times, it may be desirable to minimize intrusion into the patient's musculature and associated ligamentous tissue. In some patients who have had prior surgeries, implants or fixation elements may have already been inserted into the patient's spine, and as such, an implant introduction pathway may have to account for these prior existing conditions.

Thus, it is desirable to provide an implant that can be easily inserted in accordance with a specific pathway or approach. <CIT>, <CIT> and <CIT> disclose examples of insertion tools for spinal implants. For example, in certain situations, it is desirable to provide a an instrument for insertion of a spinal implant using a midline approach. In addition, it is desirable to provide an implant (not claimed) and associated fixation elements (not claimed) that can account for subsidence that occurs with the implant subsequent to implantation while also providing rigid fixation.

The present invention relates to an spinal implant insertion instrument as claimed hereafter. Preferred embodiments of the invention are set forth in the dependent claims. The embodiments of the invention are illustrated in <FIG>. The examples of spinal implant embodiments (<NUM>; <FIG>), fixation devices (<NUM>, <FIG>), screwdriver (<NUM>, <FIG>) and angled owl instrument (<NUM>; <FIG> and <FIG>) shown in the other figures and the implantation methods described in the disclosure do not form part of the invention but represent background art that is useful for understanding the invention.

An example of implant is discosed that is configured for midline insertion into a patient's intervertebral disc space. The spinal implant may have a body including one or more apertures. The apertures are configured to receive fixation elements, such as bone screws and the like. The fixation element may comprise one or more anti-backout features, such as a split ring. The spinal implant may include structural guidance features to facilitate the angular approach of the fixation element into the apertures. The spinal implant may also be a configured with a tactile or visual feedback response feature to allow the user to know when the fixation elements are fully seated within the apertures.

The present disclosure describes a spinal implant that is configured for midline insertion into a patient's intervertebral disc space. In accordance with one example, a spinal implant is provided having an upper surface, a lower surface, an anterior portion, a posterior portion and one or more apertures within the anterior portion for receiving at least one fixation element wherein the implant is configured for midline insertion. All or some of the apertures may be configured to permit a predetermined amount of nutation by a fixation element, thus allowing the fixation element to toggle from one position to another. The spinal implant may additionally include anti-migration features.

In another exemplary embodiment, a spinal implant comprises a body and one or more apertures. The body may comprise an upper surface, a lower surface, an anterior portion, and a posterior portion, wherein the body is configured for midline insertion between vertebral bodies of a patient's spine. The one or more apertures may be provided within the anterior portion of the body and can receive at least one fixation element. At least one of the apertures is configured with either a tactile or visual feedback response feature to allow the user to know when the at least one fixation element is fully seated. In one example, the at least one aperture comprises a countersink with a center that is offset to the axis of the aperture.

In still another example, a spinal implant comprises a body and one or more apertures.

The body may comprise an upper surface, a lower surface, an anterior portion, and a posterior portion, wherein the body is configured for midline insertion between vertebral bodies of a patient's spine. The one or more apertures may be provided within the anterior portion of the body and can receive at least one fixation element. At least one of the apertures is configured with a structural guidance feature to facilitate approach of the at least one fixation element into the opening. In one example, the structural guidance feature comprises a reverse chamfer over the at least one aperture.

In yet another example, a method of treating (not forming part of the invention) a patient's spine comprises accessing at least a portion of a patient's spine via a posterior, midline approach. A spinal implant is then inserted between vertebral bodies of the patient's spine, wherein the spinal implant comprises a body having an upper surface, a lower surface, an anterior portion, a posterior portion, wherein the body is configured for midline insertion between vertebral bodies of a patient's spine, the implant further including one or more apertures within the anterior portion of the body for receiving at least one fixation element. The spinal implant is attached with the at least one fixation element to the vertebral bodies and a predetermined amount of toggling of the fixation element is permitted based on nutation of the fixation element during subsidence of the spinal implant.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. Additional features of the disclosure will be set forth in part in the description which follows or may be learned by practice of the disclosure.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure. <FIG> show perspective views of an example of a spinal implant of the present disclosure, in which:.

Referring now to <FIG>, a spinal implant <NUM> of the present disclosure is shown. The spinal implant is configured for midline insertion into a patient's intervertebral disc space. The spinal implant <NUM> may be employed in the lumbar or thoracic regions. Alternatively, the spinal implant <NUM> may be employed in the cervical region of the spine. A cervical version may be provided so long as it is appropriately sized and configured, and the surgical approach takes into account this specific cervical design as well as size.

The spinal implant <NUM> may include anterior and posterior portions <NUM>, <NUM> and upper and lower surfaces <NUM>, <NUM> profiled to correspond with the intervertebral space to which they are to be secured. The upper and lower surfaces <NUM>, <NUM> may further include surface enhancements <NUM>, such as for example, teeth, ridges, protrusions, ribs, or fins, to enhance bone attachment, prevent migration and provide more stability. In one example, the enhancements <NUM> may be formed at about a <NUM> degree angle with respect to the upper or lower surfaces <NUM>, <NUM> of the implant <NUM>. In other examples, the enhancements can have an angle between about <NUM> to about <NUM> degrees. It is understood, however, that alternative surface modifications, such as surface roughenings, barbs, spikes, bumps, etc., may also be employed. Further, biological agents, such as bone growth factors may be employed to enhance bone attachment, either alone or in combination with the mechanical enhancements described above.

In one example, as shown in <FIG>, the spinal implant <NUM> defines a generally wedge shaped structure or arrowhead profile for ease of insertion and to be suitable for a posterior midline insertion approach. As can be seen in <FIG> and <FIG>, the implant <NUM> may have rounded edges. The anterior portion <NUM> extends into curved sidewalls <NUM> that intersect with proximal portion <NUM> at posterolateral corners <NUM>. The posterolateral corners may be rounded, as shown, to provide overall smoothness to the implant profile and prevent undesirable damage to surrounding tissue. The spinal implant <NUM>, however, may have other shapes depending on the desired implantation site. Furthermore, edges of the implant <NUM> may be shaped so as to cooperate with insertion tools to minimize unintended distraction of the vertebral bodies between which the implant <NUM> is being positioned during implantation.

In one example, projections <NUM> on the upper surface <NUM> of the implant <NUM> may be provided to facilitate insertion. For instance, these projections <NUM> may be used to direct a tool or instrument. As shown in <FIG>, in one example a pair of projections 52a, 52b may be centrally provided on the upper surface <NUM> of the implant <NUM>. The projections 52a, 52b form a key way K for directing an inserter / distractor instrument's blade, and serves as a guide for such instruments.

The spinal implant <NUM> and its components may be formed of any suitable medical grade material, such as biocompatible metals like stainless steel, titanium, titanium alloys, etc. or a medical grade plastic, such as polyetheretherketone (PEEK) or another radiolucent material, ultra high molecular weight polyethylene (UHMWPE), etc. If so desired, the implant <NUM> may also be formed of a bioresorbable material. The bioresorbable material may be osteoconductive or osteoinductive (or both).

As shown, the spinal implant <NUM> may include a central opening or lumen <NUM> extending between the upper and lower surfaces <NUM>, <NUM> to facilitate bony ingrowth or fusion between adjacent bone segments, such as vertebral bodies. If so desired, the opening <NUM> may be used to receive and hold bone graft material, or other biologically active materials like bone cement, bone void filler, bone substitute material, bone chips, demineralized bone matrix, and other similar materials. The spinal implant <NUM> may be configured in a way that optimizes the opening <NUM> such that the ratio of the cage or implant structure to the load bearing area is as large as possible.

The spinal implant <NUM> may include holes <NUM> for placement of fixation screws <NUM> therethrough to secure the spinal implant <NUM> to adjacent bone tissue. In the example shown, the implant <NUM> includes three holes <NUM>, such as one hole being centrally located (i.e., along the center line), and two laterally located (i.e., beside the center line. ) Without compromising stability, the lateral holes <NUM> should be located in a manner that avoids the need to retract vessels during surgery. It has been postulated that extended retraction of vessels during surgery may lead to greater chances for complications to the patient. The lateral holes <NUM> should also be positioned so as to provide easier visibility of the surrounding implantation site for the surgeon. In the present example shown in <FIG>, the screw holes <NUM> are closely packed for easier access around vessels.

<FIG> illustrates an exemplary fixation device such as a bone screw <NUM> that may be used with the implants <NUM> of the present disclosure. The bone screw <NUM> can have a head portion <NUM> and a tip <NUM> with a threaded shaft <NUM> in between. The bone screw <NUM> may also be used with an anti-backout ring <NUM>. The screw <NUM> may also include a visual marker <NUM> comprising a groove, band, laser etching, or other similar physical indicator that disappears from view when the screw is fully seated, in order to assist with the insertion process. For example, during use, a groove or band <NUM> laser marked on the screw head <NUM> disappears from view when the screw <NUM> is fully seated within the screw hole <NUM> of the implant <NUM>. As shown in greater detail in <FIG> and <FIG>, the holes <NUM> may also include visual cues or markers to provide visual feedback to the surgeon that a screw <NUM> inserted therein is properly seated. For example, in one example, the visual cue may comprise a groove <NUM> around the screw hole <NUM>, or an indicator arrow <NUM> that can be seen when the screw <NUM> is seated fully. In one aspect of the example, the visual groove <NUM> may include an etching or a colored band. The visual groove <NUM> can be utilized to indicate that the screw <NUM> positioned therein is fully seated or implanted, thereby allowing the screw head <NUM> to clear the way for the user to view the groove <NUM>. Similarly, the indicator arrows <NUM> may be utilized as visual checks by the user that the screws <NUM> are fully seated, as the arrows <NUM> would only be viewed upon fully seating the screws <NUM> after they have been placed into the screw holes <NUM>. Accordingly, each of the screw holes <NUM> may be provided with one or more of these visual markers (i.e., a visual groove <NUM> or an indicator arrow <NUM>, or both).

One skilled in the art will appreciate that the implant <NUM> may comprise any number of holes in any location on the implant <NUM>. For instance, one example of the spinal implant <NUM> may employ two of holes <NUM> that are located on either side of the center of implant <NUM>. Optionally, the implant <NUM> may comprise other holes for receiving features like a radiologic marker or other imaging marker.

As shown in <FIG>, the spinal implant <NUM> may include bores <NUM> near the posterolateral corners <NUM> for receiving an imaging marker (not shown). The imaging marker may be formed of tantalum or a radiopaque material. The imaging marker may be configured as a rod or other appropriate shape. These imaging markers can assist with placement of the implant <NUM> by providing visual cues for the surgeon intraoperatively. A suitable imaging marker is disclosed in co-pending and co-owned <CIT>.

The holes <NUM> provide a path through which securing means (e.g., fixation elements such as bone screws) may be inserted so as to secure the implant <NUM> to respective superior and inferior vertebral bodies (not shown). The holes <NUM> may be configured to accommodate a variety of securing mechanisms, such as screws, pins, staples, or any other suitable fastening device.

The holes <NUM> of the spinal implant <NUM> may be configured to permit a predetermined amount of screw toggle (i.e., angular skew) and enable a lag effect when the fixation screw is inserted and resides inside the hole or lumen <NUM>. In other words, the holes <NUM> may be designed to permit a certain degree of nutation by the screw, and thus, the screws may toggle from one position to one or more different positions, for instance, during subsidence. It also is believed that the predetermined screw toggle (permitted by the clearance between the lumen, or hole <NUM> and the screw) promotes locking of the screw to the implant <NUM> after subsidence subsequent to implantation. In one example, the predetermined amount of screw toggle may be about <NUM> to <NUM> degrees, or about <NUM> to <NUM> degrees.

As shown in detail in <FIG>, each of the holes <NUM> may have an opening with a reverse chamfer or overhang feature. This overhang feature enable the surgeon to better guide the insertion and general approach of the fixation screw <NUM> into the screw hole <NUM>. In addition the apertures <NUM> are configured not to break out onto the upper surface <NUM> of the implant <NUM>, and as shown in <FIG> the anterior portion <NUM> has a flat face profile to better match the vertebral anatomy and which contacts bony endplates. As further shown in <FIG>, the openings <NUM> may also include a relief <NUM>, or cutaway portion, to promote visibility and ease of screw tip access. Moreover, the screw holes <NUM> may be provided on a flat face profile <NUM> of the implant <NUM>, in order to better match the vertebral anatomy of the patient.

In one example, the openings <NUM> may each include a countersink <NUM>. The countersink feature's center is offset to the center axis of the hole <NUM>, represented by lines C-C in <FIG>. This offset, represented by the arrows of <FIG>, allows a countervailing force when the surgeon applies pressure on the fixation screw <NUM> during insertion, and provides a tactile feedback response to let the surgeon know when the fixation screw's head <NUM> is properly seated. In other words, this offset causes the screw head <NUM> to become loaded (i.e., provide feedback) on final positioning.

As further shown, a portion of the countersink <NUM> may have a spherical surface <NUM>. The position of the spherical surface may be defined by the spherical radius center (represented by arrowed line SR). In other example, the openings or apertures <NUM> may be configured to provide a visual feedback response to the surgeon. Of course, the quality and strength of the feedback response also depends on the quality of the bone tissue at the area of treatment. Healthy normal bone tissue will obviously provide the best feedback, as unhealthy, diseased or damaged bone tissue would not have sufficient strength to provide the necessary countervailing force.

In one exemplary method of inserting (not forming part of the claimed invention) the spinal implant <NUM>, the surgeon prepares the implantation site by removing some disc material from the disc space between two adjacent vertebrae. The spinal implant <NUM> may be provided to the surgeon with the screws pre-attached, or separately, as desired. Using a posterior midline approach, the surgeon then places the implant <NUM> in the desired location of a patient's spine. Once in the correct location, the surgeon can tighten the screws into the surrounding bone tissue, thereby securing the implant <NUM>.

As noted, the implant <NUM> may be configured to permit a predetermined amount of screw toggle and enable a lag effect when the fixation screw is inserted and resides inside the hole or lumen <NUM>. Upon tightening, the lag effect may be observed whereby the implant <NUM> draws bone tissue towards itself, which may promote better fusion.

As further noted, the predetermined screw toggle promotes locking of the screw <NUM> to the implant <NUM> after subsidence subsequent to implantation. For example, after surgery, the patient's natural movement will result in settling and subsidence of bone tissue and the implant <NUM> in situ. It is believed that during this process, the weight exerted upon the implant <NUM> causes the fixation screws <NUM> to toggle and consequently lock against one or more surfaces of the holes <NUM> of the implant <NUM>.

Some practitioners prefer to allow some degree of movement between the implant and the adjacent vertebral body after implantation. In that case the screw heads may be provided with contours on its underside as previously discussed that allow the screws to nutate and toggle with respect to the contoured holes <NUM> of the implant <NUM>. Other practitioners may prefer a more rigid implant that is firmly locked to the adjacent vertebral body. The examples of implant <NUM> allow either preference.

In a rigidly fixed version, the screws may be provided without the contour on its underside (i.e., a relatively flat underside) while the opening <NUM> of the implant <NUM> would likewise not include a contoured seat or countersink <NUM>. Thus, when secured together, the screws and implant <NUM> may form a rigidly locked construct. Where rigid fixation is desired (i.e., no toggle), the underside of the screws may also include surfaces features as well in order to provide secure attachment to the implant <NUM>.

While a toggle and a rigidly fixed version of the implant <NUM> and screws <NUM> are described, it is understood that a combination of toggling and rigid fixation may be accomplished in a single implant <NUM> and attachment system. For example, it is possible to provide an implant <NUM> that allows toggling of one or more screws <NUM>, while also allowing rigid fixation of the other of the screws.

It will also be appreciated that the angular positioning of the various holes, as described above, allows the present implant <NUM> to be of a relatively small size and therefore insertable from a midline approach within the intervertebral spaces of the spine. Thus, it will be appreciated that the angular positioning of the holes can assist effective operation of the implant <NUM> and the ability to "stack" implants in adjacent multilevel procedures without the securing means interfering with each other. Such a feature can be of major significance in some situations and applications.

As further noted, the predetermined screw toggle promotes locking of the screw to the implant <NUM> after subsidence subsequent to implantation. For example, after surgery, the patient's natural movement will result in settling and subsidence of bone tissue and the implant <NUM> in situ. It is believed that during this process, the weight exerted upon the implant <NUM> causes the fixation screws to nutate and/or toggle and eventually lock against one or more surfaces of the holes <NUM> of the implant <NUM>.

The present disclosure also provides instruments that are useful for implanting the spinal implant <NUM> and for practicing the methods previously described. <FIG> shows an example of a fixed angle screwdriver <NUM> of the present disclosure, and the inner shaft <NUM>. <FIG> show other perspective views of the inner shaft <NUM> of the screwdriver <NUM>. As shown, the screwdriver <NUM> may have an angled neck portion <NUM> that has a fixed angle. <FIG> shows an enlarged and exploded view of the universal joint assembly <NUM> used with the inner shaft <NUM> within the screwdriver <NUM>.

<FIG> illustrate other views of the fixed angle screwdriver <NUM> that may be use in the lumbar region during the implantation process. As shown, the neck <NUM> of the screwdriver <NUM> may also be pre-bent and rigidly fixed. The universal joint assembly <NUM> promotes a more narrow diameter construct, without compromising strength, thereby providing the benefits of a single piece instrument that is minimally invasive. Moreover, the single piece instrument can be easily ported for cleanability.

<FIG> and <FIG> illustrate examples of an angled guided awl <NUM> with punch <NUM> of the present disclosure. The punch <NUM> may extend in a handle or knob <NUM> to push the punch through the awl instrument <NUM>, as shown in cross-section in <FIG>. The angled guided awl <NUM> can comprise a resected window <NUM> at an elbow of the instrument <NUM> to reduce drag and improve cleanability, as shown in <FIG>. Further, various wire or punch patterns and shapes may be employed to lower the force requirements for extension and retraction. These reduced surface area wires, or punches 122A, 122B, 122C, may have various configurations such as the ones shown in <FIG>. The patterns of the exemplary punches / wires shown are configured to maintain flexibility and strength while reducing drag within the awl instrument <NUM>.

Both the fixed angle screwdriver <NUM> and angled guided awl instrument <NUM> are configured to allow easy insertion of the implant <NUM> in the confined intervertebral space being treated. The slim profile and angularity of the instruments helps the surgeon navigate around the anatomy to properly position the implant <NUM> in a minimally invasive manner, without causing unneeded damage to the surrounding tissues.

<FIG> illustrates an exemplary embodiment of a spinal implant insertion instrument <NUM> of the present disclosure. The instrument <NUM> may comprise an elongate shaft <NUM> that extends between a gripping end <NUM> and a handle end <NUM>. As shown in detail in <FIG>, the handle end <NUM> comprises a hand-controlled actuator or wheel <NUM> that controls movement at the gripping end <NUM>. As <FIG> shows, the gripping end <NUM> comprises at least one fixed arm <NUM> for grabbing an opening <NUM> of the spinal implant <NUM>. A movable arm <NUM> is also provided, which allows the user to securely hold the implant <NUM> during insertion. This movable arm <NUM> may be controlled by the actuator wheel <NUM>, which can be turned left or right to effect movement of the movable arm <NUM> up and down, to engage with the central opening or hole <NUM> of the implant <NUM>. One advantage of the actuator wheel <NUM> being positioned away from the terminal end of the handle end <NUM> is that the actuator wheel <NUM> is not in the way of the impaction end, which is the terminal end of the handle end <NUM>.

Although the following discussion focuses on spinal implants or prostheses, it will be appreciated that many of the principles may equally be applied to other structural body parts within a human or animal body.

Claim 1:
A spinal implant insertion instrument (<NUM>) comprising:
a gripping end (<NUM>);
a handle end (<NUM>); and
an elongate shaft (<NUM>) extending between said gripping end (<NUM>) and said handle end (<NUM>),
wherein the gripping end (<NUM>) comprises a first fixed arm (<NUM>) for engaging with a first screw hole (<NUM>) in a spinal implant (<NUM>) and a moveable arm (<NUM>) for securely holding the spinal implant (<NUM>) during insertion;
wherein the handle end (<NUM>) comprises an actuator wheel (<NUM>) for controlling movement at the gripping end (<NUM>); and
wherein rotation of the actuator wheel (<NUM>) moves the moveable arm (<NUM>) up and down to engage with a second, central screw hole (<NUM>) in the spinal implant (<NUM>).