Patent Description:
Fractures such as periprosthetic fractures around implants are often treated using a modular bone plate system including multiple bone plates. Theses bone plate systems allow screws to be inserted into cancellous bone without interfering with an intramedullary canal that may contain a nail or stem of a prosthesis. In some cases, it is necessary to combine or connect two separate bone plates. However, often times when two bone plates are connected, clinical loads are realized within the coupling between the two plates. For example, torsional and shear loads, when applied to the bone plates, may be transmitted to the coupling therebetween, deforming the coupling. More robust coupling designs between two bone plates often require multiple connecting screws or fixation elements to shield the coupling from these clinical loads. However, couplings that require multiple screws are more difficult to install and require a first person to hold the bone plates together while a second person tightens the screws.

A typical bone plate such as described in <CIT>, <CIT> or <CIT>, describes a modular plating system that are interconnected via locking element and secured to the bone with cortical bone screws to lock the plate together.

The present disclosure relates to a bone fixation system, comprising a first plate including a plate body extending from a proximal end to a distal end and including a plurality of bone fixation openings extending therethrough from a first surface of the body which, when the bone plate is in an operative position, faces away from the bone, to a second surface which, when the bone plate is in an operative position, faces the bone. The first plate further includes a connection portion extending distally from the plate body, the connection portion including a positioning tab at a distal end thereof, the connection portion including a first opening extending from the first surface to the second surface, the second surface of the connection portion including a ramped part. A second plate extends from a proximal end to a distal end and includes a coupling aperture along a proximal portion thereof, the coupling aperture configured to receive the positioning tab therein, the coupling aperture including a ramped proximal face configured to abut against the ramped part of the second surface of the positioning tab when the positioning tab is inserted into the coupling aperture. The head portion including a second opening extending therethrough from a first surface of the second plate which, when the second plate is in an operative position, faces away from the bone, to a second surface which, when the bone plate is in an operative position, faces toward the bone. A connection screw is configured to extend through the first opening and the second opening to couple the first and second plates together, wherein tightening the connection screw translates the ramped proximal face along the ramped part, eliminating a connection gap therebetween.

The present disclosure also relates to a bone fixation system, comprising a base plate defined via a first surface which, in an operative position, faces away from the bone, and a second surface which, in the operative position, faces toward the bone, and including a head portion and a shaft portion extending distally from the head portion, the head portion including an engagement portion extending along the first surface of the head portion, the engagement portion including a coupling aperture at a distal end thereof, a ramped face tapering toward the coupling, and an attachment plate defined via a first surface which, in an operative position, faces away from the bone, and a second surface which, in the operative position, faces toward the bone, and including a plate body and a connection portion extending distally therefrom for coupling the attachment plate to the base plate, the connection portion sized and shaped to engage the engagement portion of the base plate and including a positioning tab at a distal end thereof, the positioning tab sized and shaped to be inserted through the coupling aperture so that the positioning tab is engageable with a portion of the second surface of the base plate distal of the coupling aperture, the connection portion including a ramped portion extending along the second surface thereof so that, when the positioning tab is inserted into the coupling aperture, the ramped portion is slidable along the ramped face to eliminate a connection gap between the connection portion and the engagement portion.

The present disclosure may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present embodiments relate to the treatment of a bone and, in particular, relates the treatment of periprosthetic fractures. The embodiments describe a bone fixation system comprising a first bone plate and a second bone plate configured to be coupled to one another via a tabbed connection. The tabbed connection includes a mating feature which promotes self-alignment of one of the bone plates relative to the other prior to fastening the two bone plates together. The design of this mating feature eliminates gaps between the two plates on areas that require resistance to clinical loads. This mating feature also enables a single screw connection between the two plates and resists clinical loads without the screw installed. In one embodiment, as described below, the first bone plate and the second bone plate of the bone fixation system may include a base plate and an attachment plate specifically configured for treatment of a femur. It will be understood by those of skill in the art, however, that the mating features described below may be used to attach any two bone plates for the fixation of any of a variety of bones. It should be noted that the terms "proximal" and "distal," as used herein, are intended to refer to a direction toward (proximal) and away from (distal) a mass of the human body.

As shown in <FIG> a bone fixation system <NUM> according to an embodiment of the present disclosure comprises a base plate <NUM> and an attachment plate such as, for example, a ring plate <NUM>, along with a connection screw <NUM>. Although the embodiments show and describe the attachment plate as a ring plate <NUM>, it will be understood by those of skill in the art that the bone fixation system <NUM> may include any of a variety of attachment plates configured to treat any of a variety of bones. Turning to <FIG>, the base plate <NUM> generally comprises a head portion <NUM> and a shaft portion <NUM> configured to be mounted over portion of a long bone such as, for example, a femur. In an embodiment, the base plate <NUM> is implanted in a target position with the shaft portion <NUM> extending over, for example, a shaft of the femur with the head portion <NUM> positioned over a vastus ridge of the femur.

The base plate <NUM> extends along a longitudinal axis from a proximal end <NUM> to a distal end <NUM> and is defined via a first surface <NUM> which, when the base plate <NUM> is in an operative position along a bone, faces away from a lateral aspect of the femur, and a second surface <NUM> which, when the base plate <NUM> is in the operative position, faces the bone. The base plate <NUM> may be any preferred length such as, for example, between <NUM>-<NUM>. However, it will be understood that this range is only exemplary. Longitudinal sides <NUM>, <NUM> extend longitudinally between the first and second surfaces <NUM>, <NUM> from the proximal end <NUM> to the distal end <NUM>. The second surface <NUM>, in an embodiment, is contoured to match the contour of a target portion of a surface of the portion of bone over which it is to be positioned. In this embodiment, the second surface <NUM> is contoured to generally match the shape of the portion of the femur over which it is to be mounted. The base plate <NUM> also includes a proximal face <NUM> connecting the first surface <NUM> to the second surface <NUM> between the two longitudinal sides <NUM>, <NUM>, at the proximal end <NUM>. The proximal face <NUM> is configured to interface with a bone-facing surface of the ring plate <NUM>, as will be described in further detail below. The head portion <NUM>, in this embodiment, has a width (i.e., a distance between the longitudinal sides <NUM>, <NUM>) greater than a width of the shaft portion <NUM>. However, it will be understood that the head and shaft portions <NUM>, <NUM> may have any dimension depending on the procedure to be performed or the bone surface on which the base plate <NUM> is to be implanted and, for example, any implant that has previously been inserted into the bone.

The head portion <NUM> includes a coupling aperture <NUM> at a distal portion thereof configured to receive a positioning tab <NUM> of the ring plate <NUM>. The aperture <NUM>, as shown in <FIG>, extends from the first surface <NUM> to the second surface <NUM> and includes a ramped proximal face <NUM> and a distal face <NUM>. The coupling aperture <NUM>, in this embodiment, is in communication with a longitudinal grooved or indented bone plate engagement portion <NUM> extending to the proximal end <NUM> of the plate and configured to receive a proximal connecting portion <NUM> of the ring plate <NUM>. As can be seen in <FIG> and <FIG>, the ramped proximal face <NUM> of the coupling aperture <NUM> extends from the second surface <NUM> to the indented portion <NUM>. The ramped proximal face <NUM>, in this embodiment, has an angle α, the angle α being for example, between <NUM> and <NUM> degrees and, more particularly, approximately <NUM> degrees relative to the second surface <NUM>.

However, it will be understood that the proximal face <NUM> may be angled at any preferred degree depending on the application or procedure in which the system <NUM> is used. The indented bone plate portion <NUM> includes a central opening <NUM> extending through the base plate <NUM> to the second surface <NUM> sized and shaped to receive the connection screw <NUM>. The central opening <NUM>, in this embodiment, includes an internal threading on an inner surface thereof configured to mate with an external threading on the outer surface of the connection screw <NUM>. Although the central opening <NUM>, in this embodiment, is shown and described as extending through a central portion of the indented plate portion <NUM>, it will be understood by those of skill in the art that the central opening <NUM> may extend through any portion of the indented plate portion <NUM> so long as the central opening <NUM> is configured to receive the connecting screw <NUM> therein. The head portion <NUM> also includes a plurality of bone fixation openings <NUM> extending therethrough from the first surface <NUM> to the second surface <NUM>. In the embodiment of <FIG>, the head portion <NUM> includes six bone fixation openings <NUM>. However, it will be understood that the head portion <NUM> may have any number of bone fixation openings in any desired configuration, depending on the procedure in which the bone fixation system <NUM> is being used.

A medial portion <NUM> (between the two longitudinal sides) of the proximal face <NUM> of the head portion <NUM>, as noted above, is configured to interface with a bone-facing second surface <NUM> of the ring plate <NUM>. That is, when the ring plate <NUM> is positioned with the positioning tab <NUM> within the coupling aperture <NUM>, the medial portion <NUM> of the proximal face <NUM> abuts a wall or ledge on the bone-facing second surface <NUM> of the ring plate <NUM> that has a shape or profile corresponding to a profile of the medial portion <NUM>, as will be described in further detail below. In an embodiment shown in <FIG>, the medial portion <NUM> includes a first part <NUM> extending perpendicularly relative to the second surface <NUM> and a second part <NUM> extending at a non-perpendicular angle from the first part <NUM> to the first surface <NUM>, as best seen in <FIG>. The second part <NUM> may be angled at approximately <NUM>-<NUM> degrees relative to the first surface <NUM>.

The shaft portion <NUM> of the base plate <NUM>, in this embodiment, includes a plurality of bone fixation openings <NUM> extending therethrough from the first surface <NUM> to the second surface <NUM>, as shown in <FIG>. It will be understood by those of skill in the art, however, that the number of bone fixation element openings <NUM> shown in the present embodiment is exemplary only and that the shaft portion <NUM> may have any number of bone fixation openings <NUM> extending therethrough in any of a variety of spacings and configurations. For example, in some embodiments, the bone fixation openings <NUM> may be aligned along the longitudinal axis of the base plate <NUM> or may be staggered relative to the longitudinal axis of the base plate <NUM>. In this embodiment, the bone fixation openings <NUM> are variable angle locking holes through which a bone fixation element such as, for example, a variable angle locking screw, may be inserted at any user selected angle (within a supported range of angulation) relative to central axes thereof as would be understood by those skilled in the art. Thus, the angle of the locking screws can be chosen by the physician depending on the patient's anatomy and the location of the base plate <NUM> relative to a fracture.

The ring plate <NUM>, as shown in <FIG>, is a plate including a substantially circular central body <NUM> with, in this embodiment, five projections <NUM> extending radially outward from the central body <NUM>. However, it will be understood that while the current embodiment includes five projections, any number of projections may be used. The central body <NUM> may be shaped as a ring defined via a first surface <NUM> which, when the ring plate <NUM> is in an operative position along a bone, faces away from the bone, a second surface <NUM> which, when the ring plate <NUM> is in the operative position, faces the bone, and substantially annular inner and outer surfaces <NUM>, <NUM> extending therebetween. The second surface <NUM>, in an embodiment, is contoured to correspond to an external surface of the portion of bone on which it is to be positioned. In this embodiment, the second surface <NUM> is contoured to generally match the shape of the portion of the femur on which it is to be mounted.

The central body <NUM> may include bone fixation openings <NUM> positioned thereabout between the annular inner and outer surfaces <NUM>, <NUM>. The bone fixation openings <NUM> extend through the ring plate <NUM> from the first surface <NUM> to the second surface <NUM>. Each projection <NUM> also includes a bone fixation opening <NUM> at a radial tip thereof. In this embodiment, the bone fixation openings <NUM> are variable angle locking holes through which a bone fixation element such as, for example, a variable angle locking screw, may be inserted at any user selected angle (within a supported range of angulation) relative to central axes thereof.

However, it will be understood that the bone fixation openings <NUM> may be any preferred type of opening.

The ring plate <NUM> includes a distal connecting portion <NUM> extending distally from the central body <NUM> and configured to be seated in the engagement portion <NUM> of the base plate <NUM>. The connecting portion <NUM> includes the positioning tab <NUM> at a distal end thereof which, as noted above, is configured to be received within the coupling aperture <NUM> of the base plate <NUM>. The geometry of the positioning tab <NUM> conforms to the geometry of the coupling aperture <NUM> with a flat surface <NUM> extending parallel to a longitudinal plane of the connecting portion <NUM> and is configured to be received distally through the coupling aperture <NUM> to be positioned substantially adjacent to the second surface <NUM> of the base plate <NUM>. The second surface <NUM> of the connection portion <NUM> has a geometry that conforms with the first surface <NUM> of the engagement portion <NUM> of the base plate <NUM>. For example, as best illustrated in <FIG>, a proximal part <NUM> of the second surface <NUM> of the connection portion <NUM> includes the wall <NUM> formed to mate with the medial portion <NUM> of the proximal face <NUM> of the base plate <NUM>. In an embodiment, the wall <NUM> includes an angled portion <NUM> that is slanted at the same angle as the second portion <NUM> of the medial portion <NUM> of the proximal face <NUM> so that any connection gap occurring between the base plate <NUM> and the ring plate <NUM> is minimized/eliminated.

A medial part <NUM> of the connecting portion <NUM>, which is distal to the proximal part <NUM>, is sized, shaped and configured to fit over a correspondingly sized, shaped and configured engagement portion <NUM> of the base plate <NUM>. The connecting portion <NUM> has a width (a dimension between two longitudinal sides of the connecting portion <NUM>) that matches the width of the engagement portion <NUM> of the base plate <NUM> so that the ring plate <NUM> can be easily fitted over the base plate <NUM> in the correct orientation. Similarly, a distal part <NUM> of the connecting portion <NUM>, extending toward the positioning tab <NUM>, has a second surface geometry that conforms to the geometry of the proximal face <NUM> of the coupling aperture <NUM>. Specifically, the distal part <NUM> is ramped at the same angle α as the proximal face <NUM> (i.e., approximately <NUM> degrees relative to the longitudinal axis of the connecting portion <NUM>), as shown in <FIG>. Again, this matching geometry provides a close fit between the base plate <NUM> and the ring plate <NUM> when the two plates are coupled together.

As can be seen in <FIG>, the connecting portion <NUM> includes a central hole <NUM> extending therethrough from the first surface <NUM> to the second surface <NUM>, the central hole <NUM> being sized and shaped to receive the connection screw <NUM>. Although the central hole <NUM> is shown and described as extending through a central portion of the connection portion <NUM>, it will be understood by those of skill in the art that the central hole <NUM> may extend through any portion of the connecting portion <NUM> so long as the central hole <NUM> is configured to receive a portion of the connecting screw <NUM> therethrough, when the base plate <NUM> and the ring plate <NUM> are coupled to one another as described below. To couple the base plate <NUM> and the ring plate <NUM> together, the central hole <NUM> may be positioned over the central opening <NUM> of the base plate <NUM>. The central hole <NUM> and the central opening <NUM> are not required to be axially aligned. Rather, the central hole <NUM> "floats" over the central opening <NUM> so that the central hole <NUM> may be shifted over the central opening <NUM>.

In one embodiment, the central hole <NUM> may have a slightly larger diameter than the central opening <NUM> to facilitating shifting of the central hole <NUM> over the central opening <NUM> as the ramped distal part <NUM> slides along the ramped proximal face <NUM> when the base plate <NUM> and the ring plate <NUM> are coupled together, as will be described in further detail below. In this embodiment, a central axis of the central hole <NUM> and a central axis of the central opening <NUM> may be coplanar, the central axes of the central hole <NUM> and the central opening <NUM> extending along a plane, for example, that extends substantially perpendicular to the first surfaces <NUM>, <NUM> and/or the second surfaces <NUM>, <NUM> of the base plate <NUM> and the ring plate <NUM>, respectively, and through longitudinal axes of the base and ring plates <NUM>, <NUM>. The central hole <NUM>, in this embodiment, may have a smooth inner surface which acts as a through-hole through which the connection screw <NUM> extends. It will be understood by those of skill in the art, however, that the central hole <NUM>, in another embodiment, may have an internal threading along an inner surface thereof for mating with an external threading on an outer surface of the connection screw <NUM>.

The connection screw <NUM>, as one skilled in the art would understand, may be any regular screw including a head portion <NUM> and a shaft portion <NUM>, as depicted in <FIG>. The shaft portion <NUM>, in this embodiment, includes threading along an outer surface thereof configured to mate with a threading on the inner surfaces of the central opening <NUM> and/or the central hole <NUM>. The head portion <NUM> may be large enough to be grasped by the physician for initial manual tightening of the connection screw <NUM>. However, the head portion <NUM> may include a driver receiving portion <NUM> so as to be engaged by a driver for final tightening of the connection screw <NUM>. It is noted, however, that the connection between the base plate <NUM> and the ring plate <NUM> is configured such that the bone plates <NUM>, <NUM> still resist clinical loads even prior to insertion of the connection screw <NUM> therein.

As would be understood by those skilled in the art, the matching geometries of the connecting portion <NUM> and positioning tab <NUM> of the ring plate <NUM> and the engagement portion <NUM> and coupling aperture <NUM> of the base plate <NUM> are configured to maximize the amount of surface area that is contact between the two plates. Thus, once the connection screw <NUM> is inserted into the bone plate system <NUM> and tightened, any gaps between the two plates <NUM>, <NUM> are eliminated by the fit of the ramped proximal face <NUM> with the ramped distal part <NUM> of the connection portion <NUM> such that any torsional or sheer loads that the bone plates bear is not seen by the screw or the connection between the plates <NUM>, <NUM> but rather, is born along the lengths of the plates themselves. Furthermore, the tongue and groove connection of the positioning tab <NUM> within the coupling aperture <NUM> allows the bone plates <NUM>, <NUM> to be easily self-aligned such that only a single connection screw <NUM> is needed to keep the plates <NUM>, <NUM> from rotating relative to one another.

According to a method (not claimed) of assembling the plates <NUM>, <NUM>, the positioning tab <NUM> of the ring plate <NUM> is inserted into the coupling aperture <NUM> of the base plate <NUM> from a non-bone-facing side of the base plate <NUM> at an oblique angle, as best shown in <FIG>. In the course of inserting the positioning tab <NUM> into the coupling aperture <NUM>, the ring plate <NUM> is rotated downwardly, or toward the plane of the base plate <NUM>, by the self-aligning geometries of the positioning tab <NUM> and coupling aperture <NUM> until the ring plate <NUM> is seated over the base plate <NUM>. When the ring plate <NUM> is seated over the base plate <NUM>, the connection portion <NUM> is positioned within the engagement portion <NUM> and the positioning tab <NUM> is fully inserted through the coupling aperture <NUM> so that there is little to no space between the two plates <NUM>, <NUM>. At this point, as noted previously, the connection between the two plates <NUM>, <NUM> is able to resist clinical loads without any screw connection therebetween. Furthermore, the connection between the positioning tab <NUM> and the coupling aperture <NUM> does not require the use of any screws or fasteners and can be made while the base plate <NUM> is mounted to a target bone, while the base plate <NUM> is detached from the target bone or while the base plate <NUM> is coupled with other bone plates.

Once the base plate <NUM> and the ring plate <NUM> have been mated together, the connection screw <NUM> is inserted first through the central hole <NUM> and then through the central opening <NUM>. The connection screw <NUM> may be initially tightened by hand with final tightening completed using a driver. In another embodiment, the connection screw <NUM> may be tightened only using a driver. During final tightening of the connection screw <NUM> and the ring plate <NUM>, the ramped proximal face <NUM> and the distal part <NUM> of the connection portion <NUM> force the ring plate <NUM> to translate along the ramp, eliminating any initial connection gap <NUM> that may have been present. As the ramped distal part <NUM> and the ramped proximal face <NUM> slide along one another to eliminate the connection gap, the shaft portion <NUM> of the connection screw <NUM> is coaxially aligned with the central axis of the central opening <NUM> of the base plate <NUM> and coplanar with the central hole <NUM> of the ring plate <NUM>.

Claim 1:
A bone fixation system (<NUM>), comprising:
a first plate including a plate body extending from a proximal end (<NUM>) to a distal end (<NUM>) and including a plurality of bone fixation openings (<NUM>) extending therethrough from a first surface (<NUM>) of the body which, when the bone plate is in an operative position, faces away from the bone, to a second surface (<NUM>) which, when the bone plate is in an operative position, faces the bone, the first plate further including a connection portion (<NUM>) extending distally from the plate body, the connection portion (<NUM>) including a first opening extending from a first surface to a second surface,;
a second plate extending from a proximal end (<NUM>) to a distal end (<NUM>) and comprising a head portion (<NUM>);
the head portion (<NUM>) including a second opening extending therethrough from a first surface (<NUM>) of the second plate which, when the second plate is in an operative position, faces away from the bone, to a second surface (<NUM>) which, when the bone plate is in an operative position, faces toward the bone; and
a connection screw (<NUM>) configured to extend through the first opening (<NUM>) and the second opening (<NUM>) to couple the first and second plates together, wherein tightening the connection screw (<NUM>) translates the ramped proximal face (<NUM>) along the ramped distal part (<NUM>), eliminating a connection gap (<NUM>) therebetween,
characterized in that
the connection portion (<NUM>) includes a positioning tab (<NUM>) at a distal end thereof, and the second surface of the connection portion (<NUM>) includes a ramped distal part (<NUM>), wherein the head portion (<NUM>) of the second plate includes a coupling aperture (<NUM>) along a proximal portion thereof, the coupling aperture (<NUM>) configured to receive the positioning tab (<NUM>) therein, the coupling aperture (<NUM>) including a ramped proximal face (<NUM>) configured to abut against the ramped distal part (<NUM>) of the second surface of the positioning tab (<NUM>) when the positioning tab (<NUM>) is inserted into the coupling aperture (<NUM>).