AU2018101347A4 - Cervical locking cage - Google Patents

Abstract

A cervical locking cage for placement between adjacent vertebrae of the cervical spine, the cage having a first surface and a second surface for respective engagement with an endplate of adjacent vertebrae, the cage having an opening extending between the first and second surfaces. An engagement member is rotatably mounted to a wall defining the opening, the engagement member being rotatable to extend beyond one or both of the first and second surfaces wherein the engagement member comprises at least one blade angled away from the wall to which the engagement member is rotatably mounted. - IlI Figure la Figure lb

Description

TECHNICAL FIELD [0001] The present invention generally relates to a cervical locking cage for an anterior cervical dissection and fusion procedure.

BACKGROUND [0002] Anterior cervical discectomy and fusion (ACDF) is a surgical procedure where a medical practitioner enters the space between adjacent vertebrae of the cervical spine through an incision in the anterior neck, and removes the intervertebral disc along typically along with any bone spurs. After removal of the disc, an implant termed a cervical locking cage may be placed in the interbody space of the removed disc to stabilize the spine.

[0003] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

BRIEF SUMMARY [0004] The present invention seeks to provide an invention with improved features and properties.

[0005] According to an aspect the present invention provides a cervical locking cage for placement between adjacent vertebrae of the cervical spine, the cage having a first surface and a second surface for respective engagement with an endplate of adjacent vertebrae, the cage having an opening extending between the first and second surfaces.

[0006] In an embodiment at least a portion of the first surface or the second surface is substantially aligned with a plane.

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-2[0007] In an embodiment at least a portion of the first surface is substantially aligned with a plane, and wherein at least a portion of the second surface is substantially aligned with a plane.

[0008] In an embodiment at least a portion of the first and/or second surface is curved.

[0009] In an embodiment the curved portion of the first and/or second surface is configured to substantially correspond to at least a portion of the contour of a vertebral endplate.

[0010] In an embodiment at least a portion of the first surface is angled with respect to at least a portion of the second surface by between about 6° to about 9°.

[0011] In an embodiment an engagement member is rotatably mounted to a wall defining the opening, the engagement member being rotatable to extend beyond one or both of the first and second surfaces.

[0012] In an embodiment the engagement member comprises at least one blade angled away from the wall to which the engagement member is rotatably mounted.

[0013] In an embodiment the engagement member comprises two blades in diametrically opposed relation about an axis of rotation.

[0014] In an embodiment the engagement member comprises at least one blade with a curved cutting surface such that a tip of the blade is rearward to a portion of the blade proximal to the axis of rotation with respect to the direction of rotation.

[0015] In an embodiment the engagement member is configured to rotate in one direction only.

[0016] In an embodiment the engagement member is lockable in a position wherein the engagement member extends beyond one or both of the first and second surfaces.

[0017] In an embodiment the engagement member is rotatable between a first position wherein the engagement member locates within the open and a second position wherein

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-3 the engagement member extends beyond the opening, wherein the required force to rotate the engagement member increases from the from the first position to the second position.

[0018] In an embodiment a progressively increasing force is required to rotate the engagement member from the first position to the second position.

[0019] In an embodiment haptic feedback is provided when the engagement member is rotated into the second position.

[0020] In an embodiment wall defining the opening is provided with a protrusion in the form of a wedge with at least a portion of slope increasing in rise in the direction of rotation of the engagement member from the first position towards the second position.

[0021] In an embodiment the footprint of the cage may be selected from about 15mm wide by about 13mm deep, about 17mm wide by about 14mm deep, about 18mm wide by about 15mm deep and about 20mm wide by about 16mm.

BRIEF DESCRIPTION OF FIGURES [0022] Example embodiments should become apparent from the following description, which is given by way of example only, of at least one preferred but nonlimiting embodiment, described in connection with the accompanying figures.

[0023] Figure la illustrates a top perspective view of an embodiment of a cervical locking cage with an engagement member in an undeployed position;

[0024] Figure lb illustrates a top perspective of an embodiment of a cervical locking cage with an engagement member in a deployed position;

[0025] Figure 2a illustrates a side view of an embodiment of a cervical locking cage with an engagement member in an undeployed position;

[0026] Figure 2b illustrates a side view of an embodiment of a cervical locking cage with an engagement member in a deployed position.

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-42018101347 13 Sep 2018 [0027] Figure 3a illustrates a top view of an embodiment of a cervical locking cage with an engagement member in an undeployed position;

[0028] Figure 3b illustrates a top view of an embodiment of a cervical locking cage with an engagement member in a deployed position;

[0029] Figure 4a illustrates an anterior view of an embodiment of a cervical locking cage with an engagement member in an undeployed position;

[0030] Figure 4b illustrates an anterior view of an embodiment of a cervical locking cage with an engagement member in a deployed position;

[0031] Figure 5 a illustrates a posterior view of an embodiment of a cervical locking cage with an engagement member in an undeployed position;

[0032] Figure 5b illustrates a posterior view of an embodiment of a cervical locking cage with an engagement member in a deployed position.

[0033] Figure 6 illustrates a front view of the engagement member in the form a double ended blade.

[0034] Figure 7 illustrates a top view of the engagement member in the form a double ended blade.

[0035] Figure 8 illustrates a perspective view of the engagement member in the form a double ended blade.

[0036] Figure 9 illustrates a side view of the engagement member in the form a double ended blade.

PARTS LIST [0037] cervical locking cage;

first surface;

second surface;

surface texturing/serrations;

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-52018101347 13 Sep 2018 opening;

anterior wall;

posterior wall;

side wall;

engagement member/blade;

curved cutting surface;

tip of cutting surface actuator/key

PREFERRED EMBODIMENTS [0038] The following modes, given by way of example only, are described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments.

[0039] In the Figures, incorporated to illustrate features of an example embodiment, like reference numerals are used to identify like parts throughout the figures.

[0040] Referring to Figure 1, shown is a cervical locking cage 1 adapted for placement in the interbody space between adjacent vertebrae of the cervical spine that would be occupied by an intervertebral disc in a healthy spine. The cage 1 is adapted to promote fusion between two adjacent vertebrae. The cage 1 has a first surface 2 and an opposing second surface 3 adapted for respective engagement with adjacent vertebrae. The first surface 2 may be adapted for engagement with the lower endplate of a superior vertebrae and the second surface 3 may be adapted for engagement with the upper endplate of an inferior vertebrae. The first surface 2 and second surface 3 may be textured to increase engagement with endplate of a vertebrae to resist movement of the cage 1 when positioned in the interbody space. In the depicted embodiment, the first surface 2 and second surface 3 are adapted with serrations 4 in the form of a saw-tooth texture 4, though other forms are possible.

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-6[0041] The cage 1 may be configured with an opening 5 extending from the first surface 2 to the second surface 3. The opening 5 may be defined by walls that border the opening 5. In the depicted embodiment, the walls may be termed the anterior wall 6, the posterior wall 7 and the side walls 8. The anterior wall 6 and the posterior wall 7 may be in opposed relation and the two side walls 8 may be adjacent to both the anterior wall 6 and the posterior wall 7 and in opposed relation to each other. The anterior wall 6 and posterior wall 7 are so-called owing to their proximity to the posterior and anterior anatomy of a patient fitted with the cage 1. In use, bone grafting material may be placed in the opening 5 to facilitate and hasten fusion of the adjacent vertebrae.

[0042] The cage 1 may include an engagement member 9 to engage with the adjacent vertebrae to resist movement of the cage 1 positioned in the interbody space. In the depicted embodiment the engagement member 9 is in the form of a blade 9 rotatably mounted to the anterior wall 6 that borders and defines in part the opening 5. The engagement member 9 may have two ends, such as two blades 9 that extend from the axis of rotation in a diametric relation. In the depiction of Figure la, the blades 9 are in an undeployed position wherein both blades 9 locate within the opening 5. While in this undeployed position, the cage 1 may be inserted into the interbody space between two adjacent vertebrae without the engagement member 9 causing an obstruction to insertion. Once the cage 1 is inserted into the interbody space, the blades 9 may be rotated into a deployed position such that at least the end portions of the blades 9 locate outside of the opening 5 and thus embed into the adjacent vertebrae thereby aiding to fix the cage 1 in position, as shown in Figure lb. As the depicted engagement member 9 has two opposing ends, one end may embed into the superior vertebrae and the other end may embed into the inferior vertebrae. In embodiments other than that shown, the engagement member 9 may have a single end, such as a single blade.

[0043] The shape of the blade 9 may include a curved cutting surface 10 on one side of the blade 9 (similar in form to a shark fin) adapted to contact with a vertebrae and cut into the vertebrae when the blade 9 is rotated, thereby embedding the blade 9 into the vertebrae. By this arrangement, the initial portion of the blade 9 to contact with a vertebrae may be offset from the tip 11 of the blade 9, which may act to ease the rotational

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-7force require to embed the blade 9 into the vertebrae. Otherwise stated, the shape of the blade 9 may be swept away from the direction of rotation so that as the blade 9 is rotated, initial contact between the blade 9 and the vertebrae occurs at a point along the axis of the blade 9 distal from the tip 11 of the blade 9, and more proximal to the axis of rotation, which may reduce the torque required to embed the blade 9.

[0044] Figure 2a shows a side view of cage 1, with the Figure 2a showing the blade 9 in an undeployed position, and Figure 2b showing the blade 9 in a deployed position. As may be noted by Figure 2b, each blade 9 of the engagement member 9 may be configured to angle away from the anterior wall 6 to which it is rotatably mounted. Otherwise stated, the tip 11 of the blade 9 is nearer to the posterior wall 7 that the portion of the blade 9 nearest to the rotatable mounting. By this arrangement, the angled blade 9 may embed into the adjacent vertebrae at a location further from the concave anterior surface of that vertebrae than an equivalent blade 9 that is not angled towards the posterior wall 7. Embedding the blade 9 further from the anterior surface of a vertebrae may reduce the risk of the blade 9 cutting into the concavity of the anterior vertebral surface, and may also ensure that a greater bone mass is present anterior to the embedded blade 9 to resist forward migration of the cage 1. In some embodiments the angle between a long axis of the blade 9 and a plane normal to the rotational axis of the blade 9 is between about 1 to 15°. In other embodiments, the angle may be between about 5 to 10°. In the depicted embodiments, the angle is about 5°.

[0045] Still referring to Figure 2, the first surface 2 may be configured as substantially flat, notwithstanding texturing of the surface as hereinbefore described. Otherwise stated the overall profile of the first surface 2 is substantially aligned with a plane, rather than being curved or taking some other shaped profile. As depicted in Figure 2, a dotted line drawn to contact with the peaks of the saw-toothed texture 4 of the first surface 2 is demonstrates that the overall profile of the first surface 2 is planar. Similarly, the profile of the second surface 3 may be configured to substantially align with a plane, again, notwithstanding the saw-toothed texture 4 of the depicted embodiment. Configuring the profile of the first and second surface 3 to be substantially flat may be beneficial in

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-8locating the cage 1 in the interbody space of a patients with vertebral endplates that have become flattened due to age.

[0046] In other embodiments, at least a portion of the first and/or second surfaces 2, 3 may be substantially aligned with a plane. In yet other embodiments, one or both of the first and second surfaces 2, 3 may be configured in full or in part with a curvature. Such a curvature may, for example, generally correspond to the contour of a vertical endplate to which that surface would contact when in use.

[0047] In the depicted embodiments, the planar profiles of the first surface 2 and second surface 3 may be angled with respect to each other, with the height of the anterior wall 6 being greater than the height of the posterior wall 7. The angle between the substantially planar first surface 2 and second surface 3 may be between about 6° to about 9° to account for patients with varying degrees of lordosis.

[0048] Figure 3 shows a top view of the cage 1 with Figure 3a showing the engagement member 9 in an undeployed position, and Figure 3b showing the engagement member 9 in a deployed position. The engagement may be rotatably coupled to a shaft extending through the anterior wall 6, thereby defining the rotational axis of the blade 9. The shaft may be connected to an actuator 12 in the form of a key 12 located on a surface of the anterior wall 6 external to the opening 5. By this arrangement, when the cage 1 is inserted into an interbody space, a medical practitioner performing an ACDF procedure may use a tool to actuate the key 12 mounted to the accessible external surface of the anterior wall 6, thereby rotating the engagement member 9.

[0049] The rotating engagement member 9 may be configured to rotate in a single direction, such that the blades 9 will resist returning to the undeployed position when deployed and embedded in a vertebrae. The rotating engagement member 9 may also be adapted to lock into the deployed position to further resist returning to the undeployed position. The engagement member may also be held in a partially locked position when in the deployed position. In this partially locked position, the engagement member requires an increased amount of tactile force in a clockwise direction to be removed from its position. This assists to further resist the engagement member returning to the first or

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-9undeployed position. In an embodiment, a ratchet arrangement (not shown) may be used to restrict the rotational direction of the engagement member 9 and to lock the engagement member 9 in the deployed position, though other methods are equally permissible.

[0050] In a preferred embodiment, the engagement member may be configured such that the force required to rotate the engagement member progressively increases from the undeployed position towards the deployed position. Such an embodiment may further include the a substantial reduction in the resistance to rotation of the engagement member when the engagement member reaches the deployed position. By this arrangement, tactile feedback may be experienced when the moving the engagement member from the undeployed position to the employed position, with resistance loading increasing as the engagement member is rotated from the undeployed to the deployed position, and with a sudden decrease in resistance experienced as the engagement member rotates into the deployed position.

[0051] In one form, the wall defining the opening adjacent the engagement member may feature a protrusion in the form of a wedge or ramp, which may be of a curved shape arranged about the axis of rotation of the engagement member. This protrusion feature may locate between the wall and the area swept by the rotation of the engagement member, and adapted such that as the engagement member rotated from the undeployed to the deployed position, the a portion of the engagement member facing the nearest wall defining the opening with contact with an increasingly protruding section of the wedge shaped protrusion, thereby increasing the force required to rotate the engagement member. The wall protrusion may be further configured with a fall in height corresponding with the point at which the engagement member is rotated into the deployed position, such that the resistance to further rotation decreases thus offering feedback that the engagement member is in the deployed position. Accordingly, the wall protrusion may function like a linear cam that increases resistance to rotation of the engagement member acting as a follower until the deployed state is reached, wherein resistance to rotation tacitly decreases. Further several such wall protrusions may be arranged about the axis of rotation of the engagement member, such that if rotation of the engagement member continues past the deployed position, resistance to turning may increase until the engagement member rotates another

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-1090 degrees into an undeployed position. In an embodiment the engagement member may include a feature, for example a protrusion or tab, that is configured to act as a cam follower, and thus contact with the wall protrusion in order to provide the resistance loading to rotation as hereinbefore described.

[0052] In an alternative embodiment to the above, a groove of variable depth may be formed into the wall, with a feature of the engagement member, for example a protrusion or a tab, configured to trace the groove as the engagement member is rotated. The depth of the grove may progressively decrease, such that the tab on the engagement member traces a progressively less deep portion of the groove as the engagement member is rotated toward the deployed position. Further, the depth of the groove in contact with the tab may be configured to increase substantially at a point where the engagement member rotates into the engagement position. By this arrangement, the groove may act as a cam and the tab may act as a follower tracing along the groove as the engagement member is rotated in a many analogous to the embodiment above, such that the force loading increases as the engagement member rotates towards the deployed position, with a tacit decrease in force experienced as the deployed position is reached.

[0053] In an embodiment, the engagement member may include a feature, such as a tab protruding from the engagement member towards the adjacent wall, said tab contacting the wall protrusion. In such an embodiment, as the engagement member is rotated from the undeployed position to the deployed position, the tab may contact with an increasingly protruding portion of the wall protrusion, thereby progressively loading the force required to turn the engagement member. The wall protrusion may be further configured to feature a fall in height as the [0054] Figure 4 shows an anterior view of the cage 1 with Figure 4a showing the engagement member 9 in an undeployed position and Figure 4b showing the engagement member 9 in a deployed position extending from the confines of the opening 5. Figure 4 also shows the actuator 12 located on the external surface of the anterior wall 6 opposite the opening 5, which would be accessible to a medical practitioner performing an ACDF procedure with the cage 1 correctly positioned in the interbody space.

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- 11 [0055] Figure 5 shows a posterior view of the cage 1 with Figure 5 a showing the engagement member 9 in an undeployed position and Figure 5b showing the engagement member 9 in a deployed position extending from the confines of the opening 5. Evident from Figure 5 is the smaller height of the posterior wall compared to the anterior wall 6.

[0056] Figure 6 provides front view of the engagement member 9 in the form of a double ended blade 9 detached from the cage 1, with the direction of rotation from the undeployed to the deployed position indicated. As hereinbefore described, the each of the blades 9 may have a curved cutting surface 10 that curves away from the direction of rotation such that as the blade 9 rotates, the tip 11 of the blade 9 is rearward to portions of the blade 9 more proximal to the axis of rotation. In the depicted embodiment, the curvature of the blade 9 takes the general form of a circular arc, which may be described as fin shaped, though blades 9 with other shaped curvature are equally permissible.

[0057] Figure 7 shows a top view of the engagement member 9. Notable from Figure 7 is that each blade 9 is angled with respect to the rotational axis as herein before described. Figure 8 shows a perspective view of the engagement member 9 whereas Figure 9 shows a side view. Figures 8 and 9 indicate example detail of the cutting surface of the engagement member 9 in the form of a double blade 9.

[0058] The cage 1 may be provided in various sizes to cover the range of anatomical requirements of different patients. The ideal cage 1 size selected aims to cover the majority of the interbody space cleared of the intervertebral disc in order to provide the greatest possible fusion area. Provision of a cage 1 with a size/footprint that may locate further towards the boundaries of the vertebral endplates that the cage 1 can contact may increase the strength of the bone on which it sits. Accordingly, this may lessen the incidence of cage 1 subsidence whereby the cage 1 sinks into the bone and lessens the intended height restoration of the cage 1. Otherwise stated, provision of the cage 1 in a range of sizes may allow a medical practitioner to select an appropriate size in order to facilitate greater disc-space coverage and potentially greater fusion area. In example embodiments, the cage 1 may be provided in the following sizes: about 15mm wide by about 13mm deep, about 17mm wide by about 14mm deep, about 18mm wide by about

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- 1215mm deep and about 20mm wide by about 16mm, wherein width is taken as the greatest distance between the side walls 8 and depth is taken as the distance between the exterior surface of the posterior wall 7 to the extremity of the actuator 12 on the external surface of the anterior wall 6. Furthermore, cages 1 of the aforementioned sizes may be provided with between about 6° and about 9° angles between the first surface 2 and the second surface 3 as hereinbefore described. It has been found that the provision of cages 1 in these dimensions may provide an optimal selection for a medical practitioner to restore the correct anatomical alignment of the cervical spine during an anterior cervical dissection and fusion procedure.

[0059] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

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Claims (7)

The claims defining the invention are as follows:
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   Figure lb

   1. A cervical locking cage for placement between adjacent vertebrae of the cervical spine, the cage having a first surface and a second surface for respective engagement with an endplate of adjacent vertebrae, the cage having an opening extending between the first and second surfaces.
2. -2/71

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   Figure 2b

   2. A cervical locking cage, according to claim 1 wherein at least a portion of the first surface or the second surface is substantially aligned with a plane.
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   Figure 3b

   3. The cervical locking cage according to claim 2, where at least a portion of the first surface is substantially aligned with a plane, and wherein at least a portion of the second surface is substantially aligned with a plane.
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   Figure 4B

   4. The cervical locking cage according to claim 1 or claim 2, wherein at least a portion of the first and/or second surface is curved.
5. -5/7 1

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   Figure 5b

   5. The cervical locking cage according to claim 4, wherein the curved portion of the first and/or second surface is configured to substantially correspond to at least a portion of the contour of a vertebral endplate.
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   Figure 7

   6. The cervical locking cage according to any one of the preceding claims, wherein at least a portion of the first surface is angled with respect to at least a portion of the second surface by between about 6° to about 9°.

   7. The cervical locking cage according to any one of the preceding claims, wherein an engagement member is rotatably mounted to a wall defining the opening, the engagement member being rotatable to extend beyond one or both of the first and second surfaces.

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   - 148. The cervical locking cage according to any one of the preceding claims, wherein the engagement member comprises at least one blade angled away from the wall to which the engagement member is rotatably mounted.

   9. The cervical locking cage according to claim 8, wherein the engagement member comprises two blades in diametrically opposed relation about an axis of rotation.

   10. The cervical locking cage according to any one of the preceding claims, wherein the engagement member comprises at least one blade with a curved cutting surface such that a tip of the blade is rearward to a portion of the blade proximal to the axis of rotation with respect to the direction of rotation.

   11. The cervical locking cage according to any one of the preceding claims, wherein the engagement member is configured to rotate in one direction only.

   12. The cervical locking cage according to claim 11, wherein the engagement member is lockable in a position wherein the engagement member extends beyond one or both of the first and second surfaces.

   13. The cervical locking cage according to any one of claims 1 to 10, wherein the engagement member is rotatable between a first position wherein the engagement member locates within the open and a second position wherein the engagement member extends beyond the opening, wherein the required force to rotate the engagement member increases from the from the first position to the second position.

   14. The cervical locking cage according to claim 13, wherein a progressively increasing force is required to rotate the engagement member from the first position to the second position.

   15. The cervical locking cage according to claims 13 or 14, wherein haptic feedback is provided when the engagement member is rotated into the second position.

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   - 15

   16. The cervical locking cage according to any one of claim 13 to 15, wherein the a wall defining the opening is provided with a protrusion in the form of a wedge with at least a portion of slope increasing in rise in the direction of rotation of the engagement member from the first position towards the second position.

   17. The cervical locking cage according to any one of the preceding claims wherein the footprint of the cage may be selected from about 15mm wide by about 13mm deep, about 17mm wide by about 14mm deep, about 18mm wide by about 15mm deep and about 20mm wide by about 16mm.
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   Figure 8

   Figure 9