Patent Description:
Spinal disorders oftentimes requires removal of a vertebral body or bodies from the spine of a patient. An intervertebral space between the remaining vertebral bodies is typically bridged by instrumentation to stabilize the spine. Various spinal implants such as, for example, corpectomy devices, whether unexpandable or expandable, typically have been used as the instrumentation to stabilize the spine. Such corpectomy devices can have end portions for engaging endplates of the vertebral bodies bordering the intervertebral space. However, oftentimes there is a need for flexibility in providing additional height and/or angularity of the ultimate construct for implantation in the intervertebral space. The present invention is directed to one or more end caps that can be attached to a corpectomy device to provide such additional height to facilitate bridging of the intervertebral space, and/or to provide angular surfaces for engaging the endplates of the vertebral bodies to, for example, facilitate lordotic and/or kyphotic restoration. The increased height, the angular surfaces, and/or other anti-migration features of the end caps can increase the stability and anti-migration strength of the resulting combination with the corpectomy device.

From e.g. <CIT> an end cap is known, the end cap comprising: A first end and a second end opposite from one another, a first side and a second side opposite from one another, and a mid-longitudinal axis extending through the first end and the second end; a body portion extending between the first end, the second end, the first side, and the second side, the body portion including an exterior surface for contacting an end plate of a vertebral body; an interior cavity formed in the end cap opposite from the exterior surface, the interior cavity being defined by an interior surface of the body portion and various side surfaces defining a perimeter of the interior cavity.

A further end cap is known from e.g. <CIT>.

A combination of an end cap and a bone screw is known from e.g. <CIT>.

The present invention provides a combination of an end cap and a threaded bone screw with the features according to claim <NUM>. Further preferred embodiments are described in the dependent claims.

The techniques of this disclosure generally relate to an end cap and a bone screw for use therewith.

An end cap according to one embodiment of the present disclosure is generally indicated by the numeral <NUM> in <FIG>. One or more of the end caps <NUM> can be used with spinal implants disclosed, for example, in <CIT>, <CIT>, and <CIT>. The spinal implants disclosed in the above-referenced patents can be used as vertebral body replacements for replacing a vertebral body after a corpectomy has been performed on that vertebral body. A spinal implant similar to those disclosed in the above-referenced patents is generally indicated by the numeral <NUM> in <FIG>, <FIG>, and <FIG>.

One of more of the end caps <NUM> can be attached to the spinal implant <NUM> to, for example, increase the height, angularity, stability and anti-migration strength of the resulting combination. To that end, each of the end caps <NUM>, for example, can include one or more anti-migration surface features for engaging endplates of vertebral bodies, can provide one or more apertures for receiving threaded bone screws <NUM> that are insertable therethrough and into the endplates of the vertebral bodies, and/or can provide angled surfaces for engaging the endplates of the vertebral bodies to facilitate lordotic and/or kyphotic restoration. Additionally, as discussed below, the threaded bone screws <NUM> can be configured, upon receipt in the apertures in the end caps <NUM>, to lock in place relative thereto.

As depicted in <FIG>, the spinal implant <NUM> is expandable, and includes a first flange portion <NUM> at an upper first end thereof and a second flange portion <NUM> at a lower second end thereof. The expansion of the spinal implant <NUM> serves to increase the distance between the first flange portion <NUM> and the second flange portion <NUM>. Furthermore, a first recess <NUM> is provided adjacent the first flange portion <NUM> and a second recess <NUM> is provided adjacent the second flange portion <NUM>. As discussed below, a first one of the end caps <NUM> can be attached to the first flange portion <NUM> and a second one of the end caps <NUM> can be attached to the second flange portion <NUM>.

As depicted in <FIG>, the end cap <NUM> includes a first end <NUM>, a second end <NUM>, a first side <NUM>, a second side <NUM>, and a mid-longitudinal axis <NUM> extending through the first end <NUM> and the second end <NUM>. Furthermore, as depicted in <FIG>, the end cap <NUM> can include first endwall <NUM> at and adjacent the first end <NUM>, a second endwall <NUM> at and adjacent the second end <NUM>, a first sidewall <NUM> adjacent the first side <NUM>, a second sidewall <NUM> adjacent the second side <NUM>, and a body portion <NUM> (<FIG> and <FIG>) extending between the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and the second sidewall <NUM>.

An exterior surface <NUM>, as depicted in <FIG>, is formed on the body portion <NUM>. The exterior surface can extend between the first end <NUM>, the second end <NUM>, the first side <NUM>, and the second side <NUM>. The exterior surface <NUM> can be shaped to conform or substantially conform to the endplate of a vertebral body, and/or can include one or more projections P formed thereon for penetrating into the endplate. As such, when engaged to the endplate of the vertebral body, the shape of the exterior surface <NUM> and the projections P serve as the anti-migration features inhibiting movement of the end cap <NUM> (and the spinal implant <NUM> attached thereto) relative to the vertebral body.

As depicted in <FIG>, an interior cavity <NUM> is formed on an opposite side of the exterior surface <NUM>, and the interior cavity <NUM> is defined at least in part by an interior surface <NUM> of the body portion <NUM> opposite the exterior surface <NUM>, and side surfaces <NUM> defining a perimeter of the interior cavity <NUM>. The perimeter defined by the side surfaces <NUM> can be sized to correspond to the shapes of the first flange portion <NUM> and the second flange portion <NUM> to facilitate receipt of one of the first flange portion <NUM> and the second flange portion <NUM> in the interior cavity <NUM>.

To facilitate attachment of the end cap <NUM> to the first flange portion <NUM> or the second flange portion <NUM>, the interior cavity <NUM>, as depicted in <FIG>, can include a lip portion <NUM> and a flexible detent portion <NUM> (with a nub <NUM>) provided therein that are used to facilitate attachment of either of the first flange portion <NUM> and the second flange portion <NUM> to end cap <NUM>. The lip portion <NUM> can extend inwardly from one of the side surfaces <NUM>, and the flexible detent portion <NUM> can extend downwardly from the interior surface <NUM> across from the lip portion <NUM>.

To attach the end cap <NUM> to one of the first flange portion <NUM> and the second flange portion <NUM> of the spinal implant <NUM>, a first portion of the first flange portion <NUM> or the second flange portion <NUM> can be received between the lip portion <NUM> and the interior surface <NUM> with a portion of the lip portion being received in a corresponding one of the first recess <NUM> and the second recess <NUM>. Thereafter, a second portion of the first flange portion <NUM> or the second flange portion <NUM> can be pushed past the nub <NUM> of the flexible detent portion <NUM>, so that the second portion of the first flange portion <NUM> or the second flange portion <NUM> is received between the nub <NUM> and the interior surface <NUM> with a portion of the nub <NUM> being received in a corresponding one of the first recess <NUM> and the second recess <NUM>. By capturing a portion of the first flange portion <NUM> or the second flange portion <NUM> between the lip portion <NUM> and the interior surface <NUM> and another portion of the first flange portion <NUM> or the second flange portion <NUM> between the nub <NUM> and the interior surface <NUM>, the end cap <NUM> can be attached to the spinal implant <NUM>.

An aperture <NUM> with a sidewall <NUM>, as depicted in <FIG> and <FIG>, can be provided in the end cap <NUM> between the exterior surface <NUM> and the interior surface <NUM>. The aperture <NUM> can afford access to the spinal implant <NUM>, and/or to afford bone growth from the endplate of the vertebral body therethrough and into the spinal implant <NUM>. Additionally, as depicted in <FIG>, bone screw holes <NUM> can extend through the end cap <NUM> between first openings <NUM> formed in the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and/or the second sidewall <NUM>, and second openings <NUM> formed in the sidewall <NUM> of the aperture <NUM>. The second openings <NUM> can also be formed all or in part in the exterior surface <NUM>. The locations of the bone screw holes <NUM> can afford multiple surgical approaches including, for example, posterior, lateral, or postero-lateral approaches.

The bone screws holes <NUM> can be threaded to engage the threaded bone screws <NUM> therein. When the end cap <NUM> is positioned adjacent the endplate of the vertebral body, the threaded bone screws <NUM> can be inserted through the bone screw holes <NUM> and into the endplate to prevent migration of the end cap <NUM> (and the spinal implant <NUM> attached thereto) relative to the vertebral body.

Additionally, the end cap <NUM> can be configured to have an angled exterior surface <NUM> to create a lordotic angle or a kyphotic angle for engaging the endplate of the vertebral body. To illustrate, a rim surface <NUM>, as depicted in <FIG>, can be formed on the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and the second sidewall <NUM> adjacent the interior cavity <NUM> and/or around the perimeter thereof. At least portions of the rim surface <NUM> can reside in a first plane, and at least portions of the exterior surface <NUM> can reside in a second plane angled with respect to the first plane. The exterior surface <NUM> can be angled so that the first plane and the second plane are parallel or substantially parallel to one another, or the exterior surface <NUM> can be angled so that the first plane is oriented at an acute angle with respect to the second plane. The endplate can be configured to provide a desired lordotic angle or kyphotic angle by providing a corresponding acute angle of the first plane relative to the second plane. Instead of or in addition to the desired lordotic angle or kyphotic angle, the exterior surface <NUM> could also be convex in planes aligned with or transverse to the mid-longitudinal axis <NUM>.

Additional embodiments of the end cap of the present disclosure are generally indicated by the numeral <NUM> in <FIG> and by the numeral <NUM> in <FIG>. Like the end caps, one or more of the end caps <NUM> and/or one or more of the end caps <NUM> can be attached to the spinal implant <NUM> to, for example, increase the height, angularity, stability and anti-migration strength of the resulting combination. The end caps <NUM> and <NUM> can include many of the features of the end cap <NUM>. For example, each of the end caps <NUM> and <NUM> can include interior cavities similar to the interior cavity <NUM> that afford attachment of a first one of the end caps <NUM> and <NUM> to the first flange portion <NUM> of the spinal implant <NUM>, and attachment of a second one of the end caps <NUM> and <NUM> to the second flange portion <NUM> of the spinal implant <NUM>. As depicted in <FIG>, the end cap <NUM> includes a first end <NUM>, a second end <NUM>, a first side <NUM>, a second side <NUM>, and a mid-longitudinal axis <NUM> extending through the first end <NUM> and the second end <NUM>. Furthermore, as depicted in <FIG>, the end cap <NUM> can include first endwall <NUM> at and adjacent the first end <NUM>, a second endwall <NUM> at and adjacent the second end <NUM>, a first sidewall <NUM> adjacent the first side <NUM>, a second sidewall <NUM> adjacent the second side <NUM>, and a body portion <NUM> extending between the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and the second sidewall <NUM>.

The end cap <NUM> includes an exterior surface <NUM> formed on the body portion <NUM> formed between the first end <NUM>, the second end <NUM>, the first side <NUM>, and the second side <NUM>. The exterior surface <NUM> can be angled and/or shaped to conform or substantially conform to the endplate of a vertebral body, and/or can include one or more projections P formed thereon for penetrating into the endplate. As such, when engaged to the endplate of the vertebral body, the angle and/or shape of the exterior surface <NUM> and the projections P serve as the anti-migration features inhibiting movement of the end cap <NUM> (and the spinal implant <NUM> attached thereto) relative to the vertebral body.

An interior cavity of the end cap <NUM> can be formed opposite from the exterior surface <NUM>, and can be similar in configuration and function to the interior cavity <NUM> of the end cap <NUM>. Like the interior cavity <NUM>, the interior cavity of the end cap <NUM> can include a lip portion similar to the lip portion <NUM>, as well as a flexible detent portion and a nub similar to the flexible detent portion <NUM> and the nub <NUM> that are used to facilitate attachment of either of the first flange portion <NUM> and the second flange portion <NUM> to end cap <NUM>. In addition to the interior cavity, the end cap <NUM> can include a rim surface <NUM> formed on the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and the second sidewall <NUM> adjacent the interior cavity and/or around the perimeter thereof, and at least a portion of the exterior surface <NUM> resides in a third plane and at least a portion of the rim surface <NUM> resides in a fourth plane, where the third plane and the fourth plane can be angled with respect to one another to be parallel, substantially parallel, and/or to provide a desired lordotic or kyphotic angle. As depicted in <FIG>, the exterior surface <NUM> and the rim surface <NUM> are angled so that the third plane and the fourth plane are parallel to one another. The exterior surface <NUM> could also be convex in planes aligned with or transverse to the mid-longitudinal axis <NUM>.

An aperture <NUM> with a sidewall <NUM>, as depicted in <FIG>, can be provided in the end cap <NUM> between the exterior surface <NUM> and an interior surface formed in the interior cavity opposite from the exterior surface <NUM>. The aperture <NUM> can afford access to the spinal implant <NUM>, and/or to afford bone growth from the endplate of the vertebral body therethrough and into the spinal implant <NUM>. Additionally, the end cap <NUM> can include an end surface <NUM> formed on at least one of the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and/or the second sidewall <NUM> that can be angled at an acute angle with respect to the exterior surface <NUM>. As depicted in <FIG>, the end surface <NUM> is formed on the first endwall <NUM>. Bone screw holes <NUM> can be formed through the end cap <NUM>, and extend from first openings <NUM> formed in the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and/or the second sidewall <NUM> to second openings <NUM> formed in the exterior surface <NUM> and/or the sidewall <NUM>. The end surface <NUM> can accommodate engagement of the threaded bone screws <NUM> received in the bone screw holes <NUM>.

As depicted in <FIG>, the end cap <NUM> includes a first end <NUM>, a second end <NUM>, a first side <NUM>, a second side <NUM>, and a mid-longitudinal axis <NUM> extending through the first end <NUM> and the second end <NUM>. Furthermore, as depicted in <FIG>, the end cap <NUM> can include first endwall <NUM> at and adjacent the first end <NUM>, a second endwall <NUM> at and adjacent the second end <NUM>, a first sidewall <NUM> adjacent the first side <NUM>, a second sidewall <NUM> adjacent the second side <NUM>, and a body portion <NUM> extending between the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and the second sidewall <NUM>.

An interior cavity of the end cap <NUM> can be formed opposite from the exterior surface <NUM>, and can be similar in configuration and function to the interior cavity <NUM> of the end cap <NUM>. Like the interior cavity <NUM>, the interior cavity of the end cap <NUM> can include a lip portion similar to the lip portion <NUM>, as well as a flexible detent portion <NUM> and a nub <NUM> (<FIG>) similar to the flexible detent portion <NUM> and the nub <NUM> that are used to facilitate attachment of either of the first flange portion <NUM> and the second flange portion <NUM> to end cap <NUM>. In addition to the interior cavity, the end cap <NUM> can include a rim surface <NUM> formed on the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and the second sidewall <NUM> adjacent the interior cavity and/or around the perimeter thereof, and at least a portion of the exterior surface <NUM> can reside in a fifth plane and at least a portion of the rim surface <NUM> can reside in a sixth plane, where the fifth plane and the sixth plane can be angled with respect to one another to be parallel, substantially parallel, and/or to provide a desired lordotic or kyphotic angle. As depicted in <NUM>, a first portion of the exterior surface <NUM> adjacent the first end <NUM> is angled at a first acute angle relative to central portions of the rim surface <NUM>, a second portion of the exterior surface <NUM> adjacent the second end <NUM> is angled at a second acute angle relative to the central portions of the rim surface <NUM>, and a third portion of the exterior surface <NUM> between the first portion and the second portion thereof is angled to be parallel to the central portions of the rim surface. As such, the exterior surface <NUM> is generally convex in planes aligned with the mid-longitudinal axis <NUM>. The exterior surface <NUM> could also be convex in planes transverse to the mid-longitudinal axis <NUM>.

An aperture <NUM> with a sidewall <NUM>, as depicted in <FIG>, can be provided in the end cap <NUM> between the exterior surface <NUM> and an interior surface formed in the interior cavity opposite from the exterior surface <NUM>. The aperture <NUM> can afford access to the spinal implant <NUM>, and/or to afford bone growth from the endplate of the vertebral body therethrough and into the spinal implant <NUM>. Additional apertures <NUM> for access to the spinal implant <NUM>, and/or to afford bone ingrowth can be provided on either side of the aperture <NUM>. Additionally, the end cap <NUM> can include an end surface <NUM> formed on at least one of the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and/or the second sidewall <NUM> that can be angled at a perpendicular or a substantially perpendicular angle with respect to the exterior surface <NUM>. As depicted in <FIG>, the end surface <NUM> is formed on the first endwall <NUM>. Bone screw holes <NUM> can be formed through the end cap <NUM>, and extend from first openings <NUM> formed in the first endwall <NUM>, the second endwall <NUM>, the first sidewall <NUM>, and/or the second sidewall <NUM> to second openings <NUM> formed in the exterior surface <NUM> and/or the sidewall <NUM>. The end surface <NUM> can accommodate engagement of the threaded bone screws <NUM> received in the bone screw holes <NUM>.

Whereas, as depicted in <FIG>, the maximum dimensions of the end cap <NUM> between the first end <NUM> and a second end <NUM>, and between the first side <NUM> and a second side <NUM> are substantially equal, the corresponding maximum dimensions of the end cap <NUM>, as depicted in <FIG>, can be substantially different. The end cap <NUM> is configured to a have a greater maximum dimension between the first end <NUM> and the second end <NUM> than between a first side <NUM> and second side <NUM>. As depicted in <FIG>, the maximum dimension between the first end <NUM> and the second end <NUM> is approximately double the maximum dimension between the first side <NUM> and the second side <NUM>. As such, the greater dimensions between the first end <NUM> and the second end <NUM> can allow the end cap <NUM> to span significant portions of, for example, the anterior-to-posterior dimension or the lateral-to-lateral dimension of the endplate.

The threaded bone screw <NUM> is also depicted in <FIG>. As depicted in <FIG>, the threaded bone screw <NUM> used with the end caps <NUM>, <NUM>, and <NUM> can include a proximal end <NUM>, a distal end <NUM>, and an axis of rotation <NUM> extending through the proximal end <NUM> and the distal end <NUM>. Furthermore, the threaded bone screw <NUM> includes a head portion <NUM> and can include a shaft portion <NUM>, and a tip portion <NUM>. The head portion <NUM> can extend from the proximal end <NUM> to the shaft portion <NUM>, the shaft portion <NUM> can extend from the head portion <NUM> to the tip portion <NUM>, and the tip portion <NUM> can extend from the shaft portion <NUM> to the distal end <NUM>.

The head portion <NUM> can include a tool-engaging recess <NUM> (<FIG>) provided at the proximal end <NUM>, the shaft portion <NUM> can include threads <NUM> (<FIG>) for retention in the endplates of the vertebral bodies, and the tip portion <NUM> can be configured for self-drilling through the endplates of the vertebral bodies. Additionally, as depicted in <FIG>, the head portion <NUM> includes one or more aperture(s) <NUM> and corresponding spring tab portion(s) <NUM> extending from the head portion <NUM> and/or the shaft portion <NUM> into the aperture(s) <NUM>. The spring tab portion(s) <NUM> being biased in a first position, but can be flexible inwardly with respect to the corresponding aperture(s) <NUM>. Each of the spring tab portion(s) <NUM> includes a nub <NUM> formed thereon.

Claim 1:
An end cap (<NUM>; <NUM>; <NUM>) for use with a spinal implant (<NUM>) used to replace portions of a vertebral body after a corpectomy thereof in combination with a threaded bone screw (<NUM>),
the end cap (<NUM>; <NUM>; <NUM>) comprising:
a first end (<NUM>; <NUM>; <NUM>) and a second end (<NUM>; <NUM>; <NUM>) opposite from one another, a first side (<NUM>; <NUM>; <NUM>) and a second side (<NUM>; <NUM>; <NUM>) opposite from one another, and a mid-longitudinal axis (<NUM>; <NUM>; <NUM>) extending through the first end (<NUM>; <NUM>; <NUM>) and the second end (<NUM>; <NUM>; <NUM>);
a body portion (<NUM>; <NUM>; <NUM>) extending between the first end (<NUM>; <NUM>; <NUM>), the second end (<NUM>; <NUM>; <NUM>), the first side (<NUM>; <NUM>; <NUM>), and the second side (<NUM>; <NUM>; <NUM>), the body portion (<NUM>; <NUM>; <NUM>) including an exterior surface (<NUM>; <NUM>; <NUM>) for contacting an end plate of a vertebral body;
an interior cavity (<NUM>) formed in the end cap (<NUM>; <NUM>; <NUM>) opposite from the exterior surface (<NUM>; <NUM>; <NUM>), the interior cavity (<NUM>) being defined by an interior surface (<NUM>) of the body portion (<NUM>; <NUM>; <NUM>) and various side surfaces defining a perimeter of the interior cavity (<NUM>); and
a bone screw hole (<NUM>; <NUM>; <NUM>) formed therein for receiving the threaded bone screw (<NUM>), and the bone screw hole (<NUM>; <NUM>; <NUM>) includes a recess (<NUM>) formed therein,
wherein the interior cavity (<NUM>) is sized to receive a flange portion (<NUM>, <NUM>) of the spinal implant (<NUM>), and includes at least one attachment structure provided in the interior cavity (<NUM>) facilitating attachment of the end cap (<NUM>; <NUM>; <NUM>) to the flange portion (<NUM>, <NUM>) of the spinal implant (<NUM>); and
the threaded bone screw (<NUM>) including:
a head portion (<NUM>) with an aperture (<NUM>) formed therein and a spring tab portion (<NUM>) extending into the aperture (<NUM>), the spring tab portion (<NUM>) being biased in a first position and being flexible inwardly relative to the aperture (<NUM>), and the head portion (<NUM>) can being insertable through the bone screw hole (<NUM>; <NUM>; <NUM>) until bias of the spring tab portion (<NUM>) forces a nub (<NUM>) formed thereon into the recess (<NUM>).