Patent Description:
First (Big toe) MTPJ fusion is one of the most common procedures performed by foot and ankle surgeons to address osteoarthritis of the big toe (Hallux rigidus) or bunion deformity (Hallux valgus). A solid fusion, in a satisfactory position, is the ultimate goal and can offer pain relief, as well as excellent functional and aesthetic results, with few limitations. The achievement of a successful bony fusion requires surgical preparation of the joint surfaces to expose quality bone, appropriate alignment of the individual bones involved, with satisfactory contact between opposing surfaces, together with stable fixation for a critical period to permit bony healing / consolidation to occur. With successful bone healing the stabilizing construct (hardware) is no longer necessary, but in a majority of cases remains in situ, unless it causes soft tissue irritation.

Numerous techniques have been used to try and secure stable fixation, from wires to screws (headed and headless/threaded), plates, (locking or non-locking) or combined plate and screw configurations. Fusion remains the gold standard for end-stage big toe arthritis. Fusion is also widely used to address severe bunion deformity (hallux valgus) or where a bunion and arthritis co-exist.

To correct a severe valgus deformity, particularly where there is a large intermetatarsal angle, translation of the proximal phalanx may be necessary. This involves lateralizing the proximal phalanx and resecting the medial eminence. Contact between the opposing surfaces may be limited in this situation. This can make positioning of a lag or compression screw difficult or impossible and one may now be dependent on single plane stabilization with a dorsal plate. This may span a defect laterally, and with poorer stability, the risk of pull out or failure is greater.

Problems and deficiencies still exist with all fusion fixation devices due to the large leverage forces or torques generated at the joint and often, poor bone quality (osteopenial/osteoporosis). Increased stresses and limited suboptimal stability can create excessive motion at the fusion site resulting in non-union (where healing does not occur), hardware failure and revision surgery. Larger, bulkier (thicker) implants, always placed dorsally in an attempt to increase stiffness at the joint line, provide the stability necessary for bony healing to occur. These implants unfortunately still do not guarantee healing. They can be prominent, causing irritation to the skin and long extensor tendon, and irritation in closed shoes. Secondary extraction surgeries are often necessary to address these issues.

It is an objective of the invention to overcome at least one of the above-referenced problems.

<CIT> discloses a bone plate comprising a first fastening segment, a second fastening segment, and a central segment, wherein the central segment connects the first and second fastening segment and the first fastening segment and the second fastening segment comprise one or more screw holes, and wherein the first fastening segment is offset from the second fastening segment at a first angle.

<CIT> discloses an implantable medical device for attaching bone parts separated from each other by a fracture, osteotomy or arthrodesis line , with a view to fusing said bone parts.

The present invention relates to a fusion plate as claimed hereafter. Preferred embodiments of the invention are set forth in the dependent claims. Associated methods are also described herein to aid understanding of the invention, but these do not form part of the claimed invention.

The objective is met by the provision of a fusion plate having a low profile (e.g. <NUM> to <NUM> in thickness), a C-shaped profile to allow the plate wrap-around the ends of the bones being fused to provide multiplanar attachment to the each bone, and incorporates one or more holes at each side of each end of the plate that are sufficiently laterally spaced-apart to receive fixing screws in an orthogonal configuration. The C-shaped profile of the plate provides structural rigidity and torsional bending stiffness while maintaining a low profile. In addition, as the plate is pre-contoured, this obviates the requirement for a surgeon to have to modify the shape of the plate prior to attachment. The C-shaped profile also provide laterally opposed surface that are orthogonal (or nearly orthogonal) allowing fixing screws to be applied in or close to a <NUM>°-<NUM>° configuration, which provides stable bone attachment on each side of the joint.

The invention provides a fusion plate to assist fusion of a first and second bone comprising a rigid elongated plate configured to span the joint between the first and second bones having a C-shaped profile (typically along its full length), a thickness of <NUM> to <NUM>, and a plurality of holes to receive bone-fixing screws to fix the plate to the first and second bones, wherein the plurality of holes include at least one proximal hole disposed on each side of a proximal end of the plate configured to receive proximal bone fixing screws in an orthogonal fixing screw configuration and at least one hole disposed on each side of a distal end of the plate configured to receive distal bone fixing screws in an orthogonal fixing screw configuration.

In any embodiment, the fusion plate has a C-shaped profile at dorsal and medial sides of the elongated plate.

In any embodiment, the fusion plate has a C-shaped profile along its length.

In any embodiment, the fusion plate has a C-shaped profile along its full length.

In any example, the first and second bones define a meta-tarsal joint of the foot in a subject. In another example, the first and second bones define an ankle joint in a subject.

In any embodiment, the fusion plate is configured for fusion of a meta-tarsal joint selected from a MetaTarsoPhalangeal joint (MTPJ) and a TarsoMetaTarsal Joint (TMTJ) of the big toe.

In any embodiment, the fusion plate comprises at least three proximal holes disposed on the proximal end of the plate and at least three distal holes disposed on a distal end of the plate (e.g. two holes on one side and one hole on an opposite side of each end of the plate).

In any embodiment, the proximal holes are longitudinally staggered along the proximal end of the plate and the distal holes are longitudinally staggered along the distal end of the plate.

In any embodiment, the plate comprises a hemi-spherical arc shaped profile.

In any embodiment, the plate comprises a curved central section and flat lateral sections. In any embodiment, some or all of the screw-receiving holes are disposed in a periphery of the curved central section. In any embodiment, some or all of the screw-receiving holes are disposed in the flat lateral sections.

In any embodiment, the fusion plate is contoured and dimensioned for dorso-medial attachment to the first and second bones.

In any embodiment, a longitudinal axis of the plate is linear.

In any embodiment, a longitudinal axis of the plate is cranked dorsally towards a distal end thereof for example by up to <NUM>°, preferably <NUM>°-<NUM>°.

In any embodiment, at least two of the proximal holes and/or distal holes are configured to receive fixing screws in a <NUM>°-<NUM>° fixing screw configuration.

In any embodiment, the fusion plate further comprises a bridging intermediate section between the proximal and distal ends.

In any embodiment, the intermediate section comprises an articulatable joint so that the fusion plate can be flexed about the articulatable joint.

In any embodiment, the fusion plate further comprises a grafting access window.

In any embodiment, the grafting access window is defined in the medial side of the fusion plate between the proximal end and the distal end.

In any embodiment, the grafting access window has a generally inverted U-shape.

The fusion plate further comprises a compression mechanism for compressing first and second bones in a longitudinal direction.

The compression mechanism comprises an elongate compression slot for receiving a screw on the dorsal side of the proximal end of the plate.

The compression mechanism further comprises an interfragmentary screw hole for receiving an interfragmentary screw on the distal end of the plate.

The interfragmentary screw hole is located in a guide channel defined in the dorsal side of the proximal end.

In any embodiment, the guide channel is formed by an inclined open bore-like extrusion formed in the dorsal side.

In any embodiment, the plate has a length of <NUM>-<NUM> or <NUM>-<NUM>.

In any embodiment, the plate has a thickness of <NUM> to <NUM> or <NUM> to <NUM>.

In any embodiment, the holes in the plate are counter-sunk holes.

In any embodiment, the fusion plate is a monoblock.

Further, the invention provides a kt comprising a plate of the invention and a plurality of bone-fixing screws.

In any embodiment, the kit comprises a plurality of fusion plates of the invention, including fusion plates of different sizes or different dorsoflexion.

In any embodiment, the screw receiving holes and screws are threaded to allow a screw to engage a hole in a threaded engagement.

The screws are generally dimensioned to extend into and across at least <NUM>%, <NUM>%, <NUM>% or <NUM>% of the target bone.

The screws may be one or more compression screws.

Further, the disclosure provides a not claimed method of fusing a first bone and second bone together in an end-to-end arrangement in a subject in need thereof, comprising the steps of:.

In any example, the first and second bones are bones of the foot.

In any example, the first and second bones define a joint selected from a MetaTarsoPhalangeal joint (MTPJ) and a TarsoMetaTarsal Joint (TMTJ) of the big toe.

In any example, the method comprises fixing the fusion plate to the bones in a dorsal-medial orientation in which the proximal end of the plate is fixed to a dorsal surface of the first bone by at least one proximal fixing screw and is fixed to a medial surface of the first bone by at least one proximal fixing screw, and the distal end of the plate is fixed to a dorsal surface of the second bone by at least one distal fixing screw and is fixed to a medial surface of the second bone by at least one distal fixing screw,.

In any example, the method comprises a step of resection of an end of one or both bones prior to fixing the fusion plate to the bones.

In any example, the method is a method of MetaTarsoPhalangeal joint (MTPJ) or TarsoMetaTarsal Joint (TMTJ) fusion in a subject.

In any example, the subject has a valgus deviation in the MPTJ.

In any example, the method comprises one or both of resection of the prominent medial eminence and lateralizing the proximal phalanx prior to fixing the fusion plate to the bones.

In any example, the subject has osteoarthritis of the big toe.

In any example, the method comprises a step of adjusting the first and second bones into a dorsoflexion orientation and fixing the plate to the bones, wherein a longitudinal axis of the plate is cranked dorsally towards a distal end thereof.

In any example, the plate is cranked dorsally by <NUM>° to <NUM>°.

The plate of the invention is an orthopaedic implant, generally comprising a plate and screw construct, designed specifically for stabilization of a big toe/first MTPJ fusion.

In any example, the method further includes the step of placing a bone graft between the bones after fixing the fusion plate to the bones.

The C cross-section and wrap around configuration implies that the plate is reinforced along a central axis which can resist greater bending moments than conventional uniplanar plates.

The plate may be configured to be applied dorso-medially to resist the bending lever/torque at the first MTPJ. The saggital component of the plate significantly increases the bending resistance, conferring stability.

The plate of the invention offers multiplanar fixation.

Screw hole orientation on the plate allows for a <NUM>-<NUM> degree locking screw configuration.

Lag screws may complement the construct, but are not necessary where good bone contact is secured.

The plate of the invention is pre-contoured to be straight or offer up to <NUM> degrees of dorsiflexion.

The plate of the invention is low profile (<NUM> to <NUM>), which reduces soft tissue and extensor tendon irritation, and obviates the need for removal.

Other aspects and preferred embodiments of the invention are defined and described in the other claims set out below.

As used herein, the term "comprise," or variations thereof such as "comprises" or "comprising," are to be read to indicate the inclusion of any recited integer (e.g. a feature, element, characteristic, property, method/process step or limitation) or group of integers (e.g. features, element, characteristics, properties, method/process steps or limitations) but not the exclusion of any other integer or group of integers. Thus, as used herein the term "comprising" is inclusive or openended and does not exclude additional, unrecited integers or method/process steps.

In the context of treatment and effective amounts as defined above, the term subject (which is to be read to include "individual", "animal", "patient" or "mammal" where context permits) defines any subject, particularly a mammalian subject, for whom treatment is indicated. Mammalian subjects include, but are not limited to, humans, domestic animals, farm animals, zoo animals, sport animals, pet animals such as dogs, cats, guinea pigs, rabbits, rats, mice, horses, cattle, cows; primates such as apes, monkeys, orangutans, and chimpanzees; canids such as dogs and wolves; felids such as cats, lions, and tigers; equids such as horses, donkeys, and zebras; food animals such as cows, pigs, and sheep; ungulates such as deer and giraffes; and rodents such as mice, rats, hamsters and guinea pigs. In preferred embodiments, the subject is a human.

As used herein, the term "C-shaped profile" means that the plate has a curved profile configured to curve around at least two surfaces of a bone, for example a dorsal and medial side/surface, and provides peripheral laterally-opposed surfaces for screw-receiving holes that are sufficiently laterally spaced apart across the plate to allow fixing screws fix the plate to the bone at or close to an orthogonal configuration (for example the screws may be at <NUM>° to <NUM>° to each other when fixed to the bone, but preferably are disposed at a <NUM>°-<NUM>° orientation. The C-shaped profile can extend along the full length of the fusion plate and particularly along the full length of the dorsal and medial sides. The C-shaped profile may be an arc shape configured to extend from <NUM>° to <NUM>° around a bone, <NUM>° to <NUM>°. The plate may include a hemi-spherical arc section. The plate may include lateral sections that are not curved in profile.

As used herein, the term "orthogonal fixing screw configuration" means that the at least two holes at each end of the plate are sufficiently laterally spaced apart such that the fixing screws engage the bone at or close to an orthogonal configuration (at about <NUM>° to about <NUM>°). Ideally the at least two holes are positioned to provide the fixing screws at a <NUM>°-<NUM>° orientation.

As used herein, the term "monoblock" as applied to a plate means that the plate is formed in one piece, generally by casting or moulding. It is distinct from plates that are formed in multiple parts and assembled or contoured after formation.

The invention will now be described with reference to specific Examples. These are merely exemplary and for illustrative purposes only: they are not intended to be limiting in any way to the scope of the monopoly claimed or to the invention described. These examples constitute the best mode currently contemplated for practicing the invention.

Referring to the drawings, and initially to <FIG>, there is illustrated a fusion plate of the invention, indicated generally by the reference numeral <NUM>, and in this case a fusion plate for MetaTarsoPhalangeal joint (MTPJ) of the big toe. The plate <NUM> is shown attached to a first bone (metatarsal) <NUM> and a second bone (proximal phalanx) <NUM> and spanning the MTPJ <NUM>. The plate has a thickness of <NUM> and a length of <NUM> and comprises a proximal end <NUM>, distal end <NUM>, and a C-shaped cross-sectional profile along its length providing a dorsal side or surface <NUM> and medial side or surface <NUM>. Holes <NUM> for fixing screws <NUM> are provided along the dorsal surface <NUM> of the plate (<FIG>) and along the medial surface <NUM> of the plate (<FIG>). The C-shaped profile of the plate allows the holes on the dorsal and medial sides <NUM>,<NUM> of the plate <NUM> to be sufficiently laterally spaced apart such that when fixing screws <NUM> are applied to fix the plate <NUM> to the bone, the screws on each side <NUM>,<NUM> of the plate <NUM> engage the bone at approximately <NUM>° to each other. This provides significant stability. In addition, the dorsal and medial holes <NUM> are longitudinally staggered, which allows the use of screws <NUM> that extend almost fully into and across the bone. This is illustrated in the sectional views of <FIG> which show a sectional view of the fusion plate in-situ and a fixing screw 12A attaching the dorsal surface <NUM> of the plate <NUM> to the dorsal surface of the metatarsal (<FIG>) and a fixing screw 12B attaching the medial surface <NUM> of the plate <NUM> to the medial surface of the metatarsal. The holes <NUM> on the dorsal and medial surface <NUM>,<NUM> of the plate <NUM> do not need to be staggered, but providing staggered holes <NUM> allows the use of screws <NUM> that are sufficiently long to extend into across most of the bone.

The plate of <FIG> is shown attached to a MetaTarsoPhalangeal joint (MTPJ) of the big toe of a right foot, and in <FIG> it is shown attached to the same joint of a left foot. In this embodiment, the fusion plate <NUM> is cranked intermediate its ends by about <NUM>°, providing for <NUM>° of dorsoflexion. The plate <NUM> does not have to be cranked, and may be neutral or provide a different degree of dorsoflexion, depending on the patient. Generally, a surgeon will know in advance of the surgery whether a dorsoflexion fusion plate <NUM> is required, and the degree of dorsoflexion that is required.

In the embodiment shown, the fusion plate <NUM> has seven dorsal holes <NUM> and seven proximal holes <NUM>, but it will be appreciated that fewer holes <NUM> may be required depending on the joint being treated and the health of the joint. Generally each end of the plate <NUM> requires at least two or three holes <NUM>, including at least one on each laterally opposed surface of the plate <NUM>.

<FIG> shows a perspective view of a fusion plate <NUM> according to the invention showing the C-shaped profile of the plate and a central hemi-spherical section <NUM> and lateral flat sections <NUM>.

<FIG> show the use of the plate to fuse a MetaTarsoPhalangeal joint (MTPJ) of the big toe in patients with different clinical requirements. In <FIG>, the plate has <NUM>° of dorsoflexion. In <FIG> and <FIG>, the plate <NUM> is neutral (no dorsoflexion) and is affixed to bone that has been surgically resected due to the patient presenting with a bunion deformity (Hallux valgus). The bunion deformity in <FIG> is less severe, meaning that only a small part 25A of the medial eminence of the metatarsal has had to be resected, whereas in <FIG> a larger section of the medial eminence 25B has had to be resected. In both cases, resection is performed prior to the plating procedure, and the medial eminence is resected so as to conform to the shape of the proximal end of the C-shaped profile of the fusion plate.

<FIG> show a third embodiment of a meta-tarsal joint fusion plate of the invention generally indicated by the reference numeral <NUM> which is broadly similar to the embodiments described in <FIG> and like numerals indicate like parts. Accordingly, the fusion plate <NUM> is made up of an elongate plate <NUM> with a generally C-shaped cross-sectional profile having a proximal end <NUM> and a distal end <NUM> together defining a dorsal side <NUM> and a medial side <NUM>. The C-shaped profile is pronounced at and particularly extends along the full length of the dorsal and medial sides <NUM>,<NUM> so that the fusion plate <NUM> effectively curves around at least two surfaces of a bone <NUM>,<NUM>. The dorsal and medial sides <NUM>,<NUM> of the proximal and distal ends <NUM>,<NUM> are provided with holes <NUM> for receiving screws which have been omitted for clarity.

However, in the present embodiment, elongate plate <NUM> is shaped and contoured to define a bridging intermediate section <NUM> between the proximal end <NUM> and the distal end <NUM> at the location of the meta-tarsal joint <NUM>. The intermediate section <NUM> is contiguous with the proximal end <NUM> and the distal end <NUM> and serves as an articulatable joint or bridge <NUM> between the proximal end <NUM> and the distal end <NUM> so that the fusion plate <NUM> can be cranked or flexed about the articulatable joint <NUM> as desired by a surgeon in accordance with dorsoflexional requirements.

The elongate plate <NUM> is further shaped and configured to define a grafting recess or access window <NUM> for facilitating post- fusion plate attachment bone grafting. In the present embodiment, the grafting access window <NUM> is located in the medial side <NUM> of the fusion plate <NUM> between the proximal end <NUM> and the distal end <NUM>. More particularly, the grafting access window <NUM> is a three sided grafting access window <NUM> defined by the proximal end <NUM>, the distal end <NUM> and the intermediate section <NUM> so that grafting access window <NUM> is positioned at the meta-tarsal joint <NUM> in use (see in particular <FIG>, <FIG>). In the present embodiment, the articulatable bridge <NUM> is shaped to be raised or convex as indicated by the reference numeral <NUM> with respect to the elongate plate <NUM> so that the grafting access window has a generally inverted U-shape and the articulatable bridge <NUM> meets the proximal end <NUM> and the distal end <NUM> at angles of about <NUM>°. The access window <NUM> also facilitates ease of access to and prevents obstruction of the bones <NUM>,<NUM> during hallux valgus fusion procedures.

The proximal end <NUM> of the fusion plate <NUM> of the invention is further provided with a compression mechanism <NUM> for compressing first and second bones <NUM>,<NUM> to be fused in a longitudinal direction (see in particular <FIG>, <FIG> and <FIG>). In the present embodiment, the compression mechanism <NUM> is made up of an elongate compression slot <NUM> for receiving a screw on the dorsal side <NUM> of the proximal end <NUM> of the elongate plate <NUM> and an interfragmentary screw hole <NUM> for receiving an interfragmentary screw on the distal end <NUM> of the elongate plate <NUM>. The interfragmentary screw hole <NUM> is located in a downwardly inclined guide channel <NUM> defined in the dorsal side <NUM> of the proximal end so that the interfragmentary screw is correctly guided into bone at an offset angle as shown particularly in <FIG>. In the present embodiment, the guide channel <NUM> is formed by an inclined open bore-like extrusion <NUM> formed on the dorsal side <NUM>.

In the present embodiment, the fusion plate <NUM> is described as being provided with the intermediate section <NUM>, the grafting access window <NUM> and the compression mechanism <NUM>. However, as will be appreciated by those skilled in the art, in other embodiments of the invention, the fusion plate <NUM> can be provided with these features singly or in any combination as required e.g. a fusion plate <NUM> with a compression mechanism <NUM> only, an intermediate section <NUM> only or a grafting access window <NUM> only or any combination of the aforementioned features as required.

In use, the fusion plate <NUM> is placed at a meta-tarsal joint <NUM> as previously described with the intermediate section <NUM> and the grafting access window <NUM> positioned at the meta-tarsal joint <NUM> as shown in the drawings. If required, the fusion plate <NUM> can be flexed as required by the surgeon about the articulatable bride <NUM> in accordance with the degree of dorsoflexion required. It should be noted that prior to placement of the fusion plate <NUM>, it may be necessary to remove bone material from the second bone <NUM> to receive the extrusion <NUM>.

Prior to fully tightening screws in the holes <NUM> on the proximal and distal ends <NUM>,<NUM> and a compression screw inserted through the compression slot <NUM>, an interfragmentary screw is inserted through the guide channel <NUM> to extend between and compress the first and second bones <NUM>,<NUM> during which the compression screw can slide in the compression slot <NUM> in accordance with bone movement. The screws are then tightened to hold the fusion plate <NUM> in position.

If bone grafting (whether paste or segmental) is being performed, the dorsal and medial sides <NUM>,<NUM> hold the bones <NUM>,<NUM> in position while the bone graft can be placed between the bones <NUM>,<NUM> as required. Accordingly, in contradistinction with the prior art where bone graft must be placed between bones prior to placing a fusion plate at the joint, the access window <NUM> of the fusion plate <NUM> of the invention facilitates placement of the bone graft post- fusion plate attachment thus providing for a more anatomic graft and osteotomy.

Claim 1:
A fusion plate (<NUM>,<NUM>,<NUM>) to assist fusion of a first bone (<NUM>) and second bone (<NUM>) comprising:
a rigid elongated plate configured to span the joint between the first and second bones having a C-shaped profile, and a plurality of holes (<NUM>) to receive bone-fixing screws (<NUM>) to fix the plate to the first and second bones, wherein the plurality of holes include at least one proximal hole disposed on each side (<NUM>, <NUM>) of a proximal end (<NUM>) of the plate configured to receive proximal bone fixing screws (<NUM>) in an orthogonal fixing screw configuration and at least one hole disposed on each side (<NUM>, <NUM>) of a distal end (<NUM>) of the plate configured to receive distal bone fixing screws in an orthogonal fixing screw configuration;
characterised in that the rigid elongated plate has a thickness of <NUM> to <NUM> and the fusion plate (<NUM>,<NUM>,<NUM>) comprises:
a compression mechanism (<NUM>) for compressing first and second bones (<NUM>,<NUM>) in a longitudinal direction;
wherein the compression mechanism (<NUM>) comprises an elongate compression slot (<NUM>) for receiving a screw on the dorsal side (<NUM>) of the proximal end (<NUM>) of the plate (<NUM>,<NUM>,<NUM>);
wherein the compression mechanism (<NUM>) further comprises an interfragmentary screw hole (<NUM>) for receiving an interfragmentary screw on the distal end (<NUM>) of the plate (<NUM>,<NUM>,<NUM>); and
wherein the interfragmentary screw hole (<NUM>) is located in a guide channel (<NUM>) defined in a dorsal side (<NUM>) of the proximal end (<NUM>).