Patent Description:
Adjacent vertebrae in the spinal column are coupled to each other by a number of ligaments and the intervertebral disc. These anatomic structures hold the adjacent vertebrae together while allowing motion. Among these structures, the intervertebral disc functions as a cushion between the vertebrae whilst allowing for relative movement of the vertebrae. Problems with intervertebral discs arise from one or more of a range of diseases and conditions. A surgical procedure, such as spinal fusion, may be used to address such problems. The goals of spinal fusion include decompressing surrounding neural structures, re-establishing anatomic spinal alignment, and stabilising the motion segment by having one vertebral body fuse, or heal, to the adjacent vertebral body. A typical spinal fusion procedure involves partial or full removal of a problematic intervertebral disc and installation of an intervertebral device in the place of the partially or fully removed intervertebral disc in order to maintain the disc space height and alignment and facilitate the fusion of one vertebra to the next. Examples of articulated insertion instruments used for inserting a modular intervertebral fusion device are disclosed in <CIT>, <CIT>, <CIT> and <CIT>.

The anterior lumbar interbody fusion (ALIF) device is a form of intervertebral device, sometimes referred to as a cage, which is inserted into the intervertebral space by approaching the spine through the abdomen. In a typical ALIF procedure, an incision is made in one side of the abdomen. The abdominal muscles and the abdominal contents are then retracted to gain access to the spine. The disc is then removed, the disc space is properly prepared and the ALIF device is introduced by way of the incision into the thus cleared passage through the abdomen before being inserted into the intervertebral space. Compared with other procedures, such as oblique lumbar interbody fusion and posterior lumbar interbody fusion procedures, the ALIF procedure allows a larger intervertebral device to be inserted into the intervertebral space. The typical ALIF device is therefore larger than other forms of intervertebral device.

Usually, the ALIF device is held by an insertion instrument with the surgeon using the insertion instrument to introduce the ALIF device into the abdomen, guide the ALIF device through the abdomen, and then to insert the ALIF device into the intervertebral space. A known form of insertion instrument has arms which extend from the end of the insertion instrument held by the surgeon with the distal ends of the arms engaging respectively towards the superior and inferior ends of the ALIF device. The arms of the insertion instrument are movable relative to each other. Where the ALIF device is height and/or angle adjustable, the distal ends of the arms are moved by the surgeon to achieve a desired height and/or angle. Where ALIF devices of fixed but respectively different height and/or angle are being used, the distal ends of the arms are moved by the surgeon to engage at different times with ALIF devices of different height and/or angle.

Considering the ALIF procedure further and a modular ALIF implant specifically, upon insertion of an ALIF device in the intervertebral space with the insertion instrument, the ALIF device is positioned in such a manner as to ensure the superior endplate component of the ALIF device is positioned up against the inferior endplate of the superior vertebra and the inferior endplate component of the ALIF device is positioned up against the superior endplate of the inferior vertebra. With the ALIF endplates in position, an appropriately sized core component can be selected and inserted, locking into both the superior and inferior endplate components. By providing the surgeon with a selection of core components with different heights and lordotic angles, the surgeon can use the assembled ALIF device to achieve an anatomic correction of the position of the superior and inferior vertebrae relative to each other, restoring the desired intervertebral height and opening up the intervertebral foramen and thus decompressing any compressed nerve roots. In cases where there has been anterior displacement of one vertebra relative to the other, posterior pedicle screw fixation can be employed. With screws implanted, the spine can be manipulated from the posterior side whereby the superior vertebra slides over the ALIF device until the desired vertebral correction is achieved. When the desired vertebral correction is achieved, the ALIF device can be fixed to the superior vertebra using screws.

The present inventors have recognised known insertion instruments to have shortcomings. When an insertion instrument is being used where a significant lordotic angle is involved, the length of a typical insertion instrument is such that the arms may be spaced apart towards their proximal end to an extent that a larger abdominal incision is needed. A small abdominal incision is generally desirable to minimise trauma for the patient, reduce likelihood of infection and provide for ease of postoperative healing. Aside from this, known insertion instruments may be less readily used when the procedure involves the L5-S1 disc, it being noted that the L5-S1 disc is one of the most commonly fused discs. In an L5-S1 procedure, the inferior arm of the insertion instrument extends generally parallel to the sacral endplate. Where there is significant pelvic inclination, or perhaps even only moderate pelvic inclination, there is a risk of at least one of the arms colliding with the pubic symphysis.

The present invention has been devised in the light of the inventors' appreciation of the above-mentioned shortcomings. It is therefore an object for the present invention to provide an improved insertion instrument for inserting a modular intervertebral fusion device into an intervertebral space.

The present invention provides an insertion instrument for inserting a modular intervertebral fusion device or components thereof into an intervertebral space, as claimed hereafter. Preferred embodiments of the invention are set forth in the dependent claims. While the implantation methods described herein do not form part of the invention, they are disclosed as they represent useful background for understanding the invention. According to a first aspect of the invention, the insertion instrument comprises:.

The insertion instrument is for inserting a modular intervertebral fusion device or components thereof into an intervertebral space, for example, by way of the ALIF procedure described above. The modular intervertebral fusion device may therefore be an anterior lumbar interbody fusion device. A modular intervertebral fusion device typically provides for adjustment of height and angle, such as lordotic angle.

The insertion instrument comprises one superior arm which is mounted on a superior support such that the superior arm extends from the superior support. The insertion instrument also comprises one inferior arm mounted on an inferior support such that the inferior arm extends from the inferior support.

The superior support and the inferior support are mechanically coupled to each other, such as by way of at least one hinge. The superior support and the inferior support are mechanically coupled such that the superior arm and the inferior arm extend in generally a same direction. In use, each of the distal ends of the superior and inferior arms engages at a respective location on a modular intervertebral fusion device or component thereof. More specifically, each of the distal ends of the superior and inferior arms may attach to a respective location on a modular intervertebral fusion device or component thereof. For example, and where the modular intervertebral fusion device has a superior endplate and an inferior endplate that are movable in relation to each other to provide for change in height and/or lordotic angle, the superior arm may be attached at a respective location on a side of the superior endplate and the inferior arm may be attached at a respective location on a side of the inferior endplate. Furthermore, the superior support and the inferior support are mechanically coupled for their relative rotation whereby there is relative rotation of: the superior arm; and the inferior arm. In use, the surgeon may rotate the superior support and the inferior support relative to each other with the surgeon manipulating the superior and inferior supports by hand either directly or by way of a further instrument, such as an instrument for inserting a core component between superior and inferior plates of an ALIF device when the superior and inferior plates are in the intervertebral space.

One of: the superior arm; and the inferior arm is unarticulated between its distal end and the respective one of the superior support and the inferior support. Furthermore, the one of the superior arm and the inferior arm may be substantially straight between its distal end and the respective one of the superior support and the inferior support. The other one of: the superior arm; and the inferior arm comprises a hinge between its distal end and the respective one of the superior support and the inferior support, the hinge rotating the distal end of the other one of the superior arm and the inferior arm towards or away from the one of the superior arm and the inferior arm.

The other one of the superior arm and the inferior arm may comprise a proximal portion which extends from the respective one of the superior support and the inferior support to the hinge and a distal portion which extends from the hinge to the distal end of the arm. Each of the proximal and distal portions may be straight.

The insertion instrument not covered by the present invention may comprise a pair of superior arms which are mounted on a superior support such that the superior arms are spaced apart and extend generally parallel with each other from the superior support. The insertion instrument not covered by the present invention may also comprise a pair of inferior arms mounted on an inferior support such that the inferior arms are spaced apart and extend generally parallel with each other from the inferior support.

At least one of the superior and inferior arms may have the form of a frame.

If the modular intervertebral fusion device has a large angle, a distal portion of the superior arm is at a correspondingly large angle to a distal portion of the inferior arm. Where the superior and inferior arms in a known insertion instrument are long, as is typically required in an insertion instrument for an ALIF device, the separation between the superior arm and the inferior arm at their proximal ends, i.e. at the arm support, may be considerable. The hinge in one arm according to the invention allows there to be a significant angle between the superior and inferior arms at the intervertebral device whilst allowing for reduction in an extent to which there is separation between the superior arm and the inferior arm at their proximal ends. Reduction in extent to which there is separation between the superior arm and the inferior arm at their proximal ends may allow for the abdominal incision to be smaller and less traumatic to the patient.

Where the insertion instrument is being used in the like of an L5-S1 procedure, the presence of a hinge in the inferior arm reduces likelihood of the inferior arm colliding with the pubic symphysis. The hinge may therefore be in each of the inferior arm.

The insertion instrument not covered by the present invention may comprise a pair of superior arms which are spaced apart from each other and extend generally parallel with each other from the superior support. The pair of superior arms may extend substantially parallel with each other from the superior support. Each of the pair of superior arms may be unarticulated between its distal end and the superior support.

According to the invention, the insertion instrument comprises one superior arm. The one superior arm may be unarticulated between its distal end and the superior support.

The insertion instrument not covered by the present invention may comprise a pair of inferior arms which are spaced apart from each other and extend generally parallel with each other from the inferior support. The pair of inferior arms may extend substantially parallel with each other from the inferior support. Each of the pair of inferior arms may comprise a hinge between its distal end and the inferior support, the hinge rotating the distal end of the inferior arm towards or away from the at least one superior arm.

According to the invention, the insertion instrument comprises one inferior arm. The one inferior arm may comprise a hinge between its distal end and the inferior support, the hinge rotating the distal end of the inferior arm towards or away from the superior arm.

As mentioned above, the superior support and the inferior support are mechanically coupled to each other to allow for the superior support and the inferior support to rotate relative to each other. Furthermore, the superior support and the inferior support may be mechanically coupled to each other to allow the superior support and the inferior support to be moved together and apart. Movement involving relative rotation and movement together and apart may be provided by way of the same mechanical coupling arrangement.

The superior support and the inferior support may rotate about a support axis which is substantially orthogonal to a longitudinal axis of the arms and substantially orthogonal to a direction of separation of the superior and inferior supports.

In addition, the superior support and the inferior support may be mechanically coupled to each other to restrict and perhaps even substantially prevent movement of the superior support and the inferior support relative to each other in a transverse direction, i.e. in a direction orthogonal to a direction of extension of arms from superior or inferior support and in a direction orthogonal to a direction of separation of the superior and inferior supports.

Alternatively or in addition, the superior support and the inferior support may be mechanically coupled to each other to restrict and perhaps even substantially prevent movement of the superior support and the inferior support relative to each other in a longitudinal direction, i.e. in the direction of extension of at least one arm from superior or inferior support.

In an alternative embodiment, the superior support and the inferior support may be mechanically coupled to each other to restrict and perhaps even substantially prevent movement of the superior support and the inferior support relative to each other in a direction of separation of the superior and inferior supports.

In addition, the superior support and the inferior support may be mechanically coupled to each other for movement of the superior and inferior supports relative to each other in a longitudinal direction. The inferior support may comprise a spring bias which is operative to drive the superior support relative to the inferior support in the longitudinal direction away from the inferior support. When the proximal and distal portions of the inferior arm are unbent such that a distance between the distal end of the inferior arm and the inferior support is of greatest extent, the spring bias may provide for alignment of the distal ends of the superior and inferior arms. When the proximal and distal portions of the inferior arm are bent, a distance between the inferior support and the distal end of the inferior arm is decreased, and the superior support may be moved relative to the inferior support against the spring bias to maintain alignment of the distal ends of the superior and inferior arms.

Nevertheless, according to the alternative embodiment, the superior support and the inferior support may be mechanically coupled to each other to allow their relative rotation and to restrict and perhaps even substantially prevent movement of the superior support and the inferior support relative to each other in a transverse direction.

The superior support and the inferior support may define inter-engaging profiles which cooperate to provide for rotation of the superior support and the inferior support relative to each other. Furthermore, the inter-engaging profiles may cooperate to provide for movement of the superior support and the inferior support together and apart.

The inter-engaging profiles may comprise a protrusion extending from one of the superior and inferior supports and a recess or perhaps even an aperture defined in the other of the superior and inferior supports, the protrusion being received in the recess or aperture to allow for at least one of: rotation; and movement of the superior support and the inferior support together and apart. In addition, the recess may have the form of a channel with the protrusion travelling along the channel to provide for movement of the superior support and the inferior support together and apart. Where an aperture is present, the aperture may have the form of a slot with the protrusion travelling along the slot to provide for movement of the superior support and the inferior support together and apart as well as relative rotation.

A first set of inter-engaging profiles may be on a first side of the superior and inferior supports and a second set of inter-engaging profiles be on a second side of the superior and inferior supports, the first and second sides facing in opposite directions. The first and second sides may be spaced apart in the transverse direction.

The superior and inferior supports may not be attached to each other by other than at least one set of inter-engaging profiles.

The inter-engaging profiles may be configured to allow for disengagement of the superior and inferior supports from each other and for separation of the superior and inferior supports from each other. A first part of the inter-engaging profiles may be movable away from a second part of the inter-engaging profiles to allow for such disengagement and separation. More specifically, the first and second parts may be comprised in one of the superior and inferior supports, such as the inferior support. Furthermore, the first and second parts may be shaped to accommodate and engage with a third part comprised in the other of the superior and inferior supports, such as the superior support. Engagement of the third part with the first and second parts may present a barrier to separation of the superior and inferior supports, such as by each of the first and second parts fitting around the third part. When the first part is moved away from the second part, such as against a spring bias, the relative disposition of the first and second parts may allow for release of the third part from the first and second parts. More specifically, a user may withdraw the third part from between the first and second parts by moving the superior and inferior supports apart from each other.

At least one arm may be mounted, and more specifically mounted at its proximal end, on each of the superior and inferior supports. The arm may be mounted such that the arm is substantially immovably relative to its respective superior or inferior support with the exception of rotation of the arm relative to the respective superior or inferior support and about the longitudinal axis of the arm. As described below, rotation of the arm relative to the support about the longitudinal axis of the arm may allow for the distal end of the arm to lock to the modular intervertebral fusion device.

Alternatively, and in particular where the insertion instrument comprises one superior arm, the superior arm may be immovably mounted on the superior support and more specifically may be integrally formed with the superior support.

Alternatively or in addition, and in particular where the insertion instrument comprises one inferior arm, the inferior arm may be immovably mounted on the inferior support and more specifically may be integrally formed with the inferior support.

Where the insertion instrument comprises a pair of each of superior and inferior arms as described above, a first superior arm and a first inferior arm may lie in substantially a first plane and a second superior arm and a second inferior arm may lie in substantially a second plane, the first and second planes being substantially parallel. As described above, the hinge rotates the distal end of one of the superior arm and the inferior arm towards or away from the other one of the superior arm and the inferior arm. The hinge may therefore rotate about a hinge axis and more specifically a transverse axis which extends between the first and second planes and more specifically extends substantially orthogonally to the first and second planes.

Where the superior and inferior supports rotate relative to each other about a support axis, the support axis may be substantially parallel to the hinge axis.

The hinge may be free to rotate about its axis whereby the hinge lacks the like of a lock for holding a distal portion of the arm at a set angle to a proximal portion of the arm.

The hinge may be located closer to the distal end of the arm than to the respective one of the superior and inferior supports. More specifically, the hinge may be <NUM> to <NUM> from the distal end of the arm. Having the hinge between <NUM> and <NUM> from the distal end of the arm has been found to provide for effective reduction in risk of collision with the pubic symphysis for a typical patient. Where the hinge is thus spaced from the distal end of the arm, the arm may be of a length of <NUM> to <NUM> and typically <NUM>. The superior and inferior arms may be of substantially the same length.

The distal end of an arm may be tapered. Alternatively or in addition, the distal end of an arm may be shaped to be snugly received in a recess defined in the intervertebral device. Each of the superior and inferior arms may thus be attached to a different location on the intervertebral device. More specifically, the superior arm may be received in a recess defined in a superior endplate of the intervertebral device and the inferior arm may be received in a recess defined an inferior endplate of the intervertebral device.

The distal end of an arm may be configured to resist detachment from the intervertebral device. Where the distal end of the arm is received in a recess, resistance to detachment may be by way of profiles which releasably engage with each other when the distal end is received in the recess. As described above, rotation of the arm relative to the support about the longitudinal axis of the arm may allow for the distal end of the arm to lock to the modular intervertebral fusion device. Further to this, the distal end of the arm and the recess may define cooperating profiles which allow for insertion of the distal end of the arm into the recess and which present resistance to withdrawal of the distal end of the arm from the recess after the arm has been rotated relative to the support about the longitudinal axis of the arm when the distal end of the arm is in the recess.

In an alternative embodiment, the insertion instrument comprises one superior arm only; and one inferior arm only. In view of the insertion instrument lacking two arms mounted on at least one of the superior support and the inferior support, the one superior arm may be configured to grip oppositely directed sides of a superior endplate component instead of engaging with the superior endplate component by rotation of each of two arms. Alternatively or in addition, the one inferior arm may be configured to grip oppositely directed sides of an inferior endplate component.

Oppositely directed sides of the endplate component may be gripped by a gripping arrangement. The gripping arrangement may comprise first and second sprung fingers which extend from a distal end of a respective arm, the first and second sprung fingers spaced apart to sufficient extent to receive an endplate component therebetween. The first and second fingers may be sprung, for example by way of the material from which they are formed such that they are inherently sprung, to increase an extent of separation therebetween towards distal ends of the first and second fingers. An endplate component may be received readily between the first and second fingers in such disposition.

The gripping arrangement may further comprise a compression mechanism which releasably engages with the first and second fingers to compress the first and second fingers together towards their distal ends and against the spring bias. The endplate component may be gripped by the first and second fingers when the compression mechanism has engaged with the first and second fingers.

The compression mechanism may comprise a compression body which is movably attached to its respective arm, the compression body mounted on the arm for movement along the arm. Movement of the compression body along the arm may provide for compression and release from compression of the first and second fingers. When the compression body is moved away from the respective one of the superior and inferior supports, the compression body may bear against the first and second fingers to compress the first and second fingers together. Each of the first and second fingers may define a shoulder against which the compression body bears to effect deflection of the respective finger. Movement of the compression body towards the respective one of the superior and inferior supports may release the first and second fingers from compression.

The arm may comprise a compression mechanism driving arrangement which is supported on its respective arm for movement relative to the arm. The compression mechanism driving arrangement may comprise a first driving member and a second driving member which are hingedly coupled to each other. The first driving member may be coupled at its proximal end to the respective one of the superior support and the inferior support and may be hingedly coupled at its distal end to a proximal end of the second driving member. The second driving member may be attached to the compression mechanism whereby the compression mechanism moves with the second driving member. Movement of the first driving member may cause the second driving member to move back and forth along the arm whereby the compression body moves between a first and second finger compressing position and a first and second finger releasing position.

As described above, the insertion instrument is for inserting an intervertebral device or components thereof. Therefore, and according to a second aspect of the present invention, there is provided an intervertebral device insertion assembly comprising an insertion instrument according to the first aspect and an intervertebral device or components thereof, the intervertebral device being configured for attachment of each of the superior and inferior arms at respective spaced apart locations on the intervertebral device or on components thereof.

The intervertebral device may be configured for attachment by way of a recess defined in the intervertebral device or in components thereof for each arm of the insertion instrument. The intervertebral device may comprise a superior endplate and an inferior endplate, the superior endplate defining a respective recess for the superior arm, and the inferior endplate defining a respective recess for the inferior arm. Where the insertion instrument comprises a pair of each of superior and inferior arms, each of the superior endplate and the inferior endplate may define a pair of recesses, the recesses in a pair of recesses being spaced apart in the transverse direction. Alternatively, and where the insertion instrument comprises one superior arm and one inferior arm, the one superior arm may grip the superior endplate as described above and the one inferior arm may grip the inferior endplate as described above.

Further embodiments of the second aspect of the present invention may comprise one or more features of the first aspect of the present invention.

According to a third aspect of the present invention, there is provided a method of inserting a modular intervertebral fusion device into an intervertebral space (not claimed) by way of an insertion instrument, the insertion instrument comprising at least one superior arm mounted on a superior support such that the at least one superior arm extends from the superior support, and at least one inferior arm mounted on an inferior support such that the at least one inferior arm extends from the inferior support, the superior support and the inferior support mechanically coupled to each other whereby the at least one superior arm and the at least one inferior arm extend in generally a same direction, the method comprising:.

Embodiments of the third aspect of the present invention may comprise one or more features of the first or second aspect of the present invention.

Further features and advantages of the present invention will become apparent from the following specific description, which is given by way of example only and with reference to the accompanying drawings, in which:.

A perspective view of an insertion instrument <NUM> according to a first example is shown in <FIG>. The insertion instrument <NUM> comprises a superior support <NUM>, an inferior support <NUM>, a pair of superior arms consisting of a first superior arm <NUM> and a second superior arm <NUM>, and a pair of inferior arms consisting of a first inferior arm <NUM> and a second inferior arm <NUM>. The pair of superior arms <NUM>, <NUM> are mounted on the superior support <NUM> such that they extend from spaced apart locations on the superior support and such that the superior arms are substantially parallel. The pair of inferior arms <NUM>, <NUM> are mounted on the inferior support <NUM> such that they extend from spaced apart locations on the inferior support <NUM> and such that the inferior arms are substantially parallel. Each of the four arms <NUM>, <NUM>, <NUM>, <NUM> is mounted on its respective support for rotation of the arm relative to the support and about the longitudinal axis of the arm; otherwise, the arm is immovable in relation to the support. The superior support <NUM> and the inferior support <NUM> are mechanically coupled to each other by a first hinge mechanism <NUM> and a second hinge mechanism <NUM>. The first hinge mechanism <NUM> is at a first side of the superior and inferior supports <NUM>, <NUM> and the second hinge mechanism <NUM> is at a second side of the superior and inferior supports, the first and second sides facing in opposite directions. The first and second hinge mechanisms <NUM>, <NUM> are described further below with reference to <FIG>.

The first and second hinge mechanisms <NUM>, <NUM> allow the superior support <NUM> and the inferior support <NUM> to rotate relative to each other and for the superior and inferior supports to be moved together and apart whilst restricting other relative movement of superior and inferior supports such as in the longitudinal direction of the arms, or in the direction of separation of the superior arms or of the inferior arms. The superior support <NUM> and the inferior support <NUM> thus rotate about a support axis which is substantially orthogonal to a longitudinal axis of the arms <NUM>, <NUM>, <NUM>, <NUM> and substantially orthogonal to a direction of separation of the superior and inferior supports. The pair of superior arms <NUM>, <NUM> moves with the superior support <NUM> and the pair of inferior arms <NUM>, <NUM> moves with the inferior support <NUM>. Relative rotation of the superior and inferior supports <NUM>, <NUM> therefore causes the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM> to rotate relative each other. Also, movement of the superior and inferior supports <NUM>, <NUM> together and apart moves the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM> together and apart. As will become clear from the description provided below with reference to <FIG>, the first and second hinge mechanisms <NUM>, <NUM> allow for relative rotation of superior and inferior supports <NUM>, <NUM> at the same time as movement of the superior and inferior supports <NUM>, <NUM> together and apart.

Mechanical coupling of the superior and inferior supports <NUM>, <NUM> by way of the first and second hinge mechanisms <NUM>, <NUM> is such that the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM> extend generally in the same direction. Although <FIG> shows the pair of superior arms <NUM>, <NUM> as parallel to the pair of inferior arms <NUM>, <NUM>, increased separation of the superior and inferior supports <NUM>, <NUM> accompanied by relative rotation of the superior and inferior supports causes the pair of superior arms and the pair of inferior arms to be angled to each other. Nevertheless, the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM> extend generally in the same direction despite the angulation.

A side view of the distal ends of the arms of the insertion instrument <NUM> of <FIG> is shown in <FIG>. The first superior arm <NUM> and the first inferior arm <NUM> can be seen in <FIG> to be slightly spaced apart and extending in parallel. As described above, the superior and inferior supports <NUM>, <NUM> can be manipulated by the surgeon to increase their separation and to angle the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM> relative to each other. Considering <FIG> further, each of the four arms tapers towards its distal end with a distal portion <NUM> having the form of a cylinder. With reference to the superior endplate <NUM> and the inferior endplate <NUM> shown in <FIG>, each distal portion <NUM> is sized and shaped to be a snug fit in a respective recess <NUM>, <NUM>, <NUM>, <NUM> proved in the superior and inferior endplates <NUM>, <NUM> of an anterior lumbar interbody fusion (ALIF) device whereby the superior and inferior endplates are supported by the four arms. The superior and inferior endplates can therefore be manipulated by the surgeon by movement of the superior and inferior supports <NUM>, <NUM> while the superior and inferior endplates <NUM>, <NUM> are supported properly by the four arms. Returning to <FIG>, a protrusion <NUM> extends from the surrounding surface of each distal portion <NUM>. Each of the superior and inferior endplates of the ALIF device defines a pair of recesses <NUM>, <NUM> and <NUM>, <NUM> in the anterior side of the endplate with the recesses in each pair spaced apart in the transverse direction. Each surface of the endplate that defines the recess <NUM>, <NUM>, <NUM>, <NUM> has a linear channel in the wall of the recess which extends from the mouth of the recess into the depth of the recess. Furthermore, the furthest most reach of the linear channel is terminated by a circumferentially extending portion of channel in the wall of the recess. When the distal portion <NUM> is inserted into a corresponding recess <NUM>, <NUM>, <NUM>, <NUM> in an endplate, the protrusion <NUM> is received in the linear channel in the wall of the recess and travels along the linear channel as the distal portion <NUM> is progressively further received in the recess. When the distal portion <NUM> is fully received in the recess <NUM>, <NUM>, <NUM>, <NUM>, the protrusion <NUM> is at the furthest most reach of the linear channel. The surgeon then rotates each arm around its longitudinal axis within the support whereby the protrusion <NUM> travels along the circumferentially extending portion of channel at the end of the linear channel. Reception of the protrusion <NUM> in the circumferentially extending portion of channel presents resistance to withdrawal of the distal portion <NUM> of the arm from the recess <NUM>, <NUM>, <NUM>, <NUM> in the endplate. The four arms are thus securely attached to respective locations on the endplates.

Considering <FIG> further, each of the first and second inferior arms <NUM>, <NUM> has a hinge <NUM> between <NUM> and <NUM> from the distal end of the arm. The hinge <NUM> allows for a distal portion <NUM> between the distal end and the hinge and a proximal portion <NUM> between the hinge and the inferior support to rotate relative to each other. The hinge <NUM> rotates about a hinge axis which is substantially parallel to the support axis whereby the distal portion <NUM> of the first inferior arm <NUM> rotates towards and away from the first superior arm <NUM> and the distal portion <NUM> of the second inferior arm <NUM> rotates towards and away from the second superior arm <NUM>. In contrast, the first and second superior arms <NUM>, <NUM> are unarticulated.

The insertion instrument is formed from a standard surgical instrument metal, such as stainless steel. Alternatively, the insertion instrument is formed from a plastics material, such as polycarbonate or nylon. An insertion instrument formed from a plastics material is typically for single use before disposal.

<FIG> shows a perspective view of the insertion instrument <NUM> of <FIG> looking from distal ends of the arms towards the superior and inferior supports <NUM>, <NUM>. As can be seen from <FIG>, the pair of superior arms <NUM>, <NUM> are mounted on the superior support <NUM> such that they move with the superior support and the pair of inferior arms <NUM>, <NUM> are mounted on the inferior support <NUM> such that they move with the inferior support. The four arms are mounted on the superior and inferior supports <NUM>, <NUM> such that the four arms extend between the first and second hinge mechanisms <NUM>, <NUM>.

The perspective view of <FIG> with the arms removed is shown in <FIG>. A superior support lug <NUM> extends from one side of a main body of the superior support <NUM> in the direction of the arms and an inferior support lug <NUM> extends from the same one side of a main body of the inferior support <NUM> in a direction of the arms. The superior support lug <NUM> and the inferior support lug <NUM> overlap. The same structure of superior and inferior support lugs is provided at the other side of the superior and inferior supports. The second hinge mechanism <NUM> is constituted by a cylindrical protrusion <NUM> which extends towards the arms from the superior support lug <NUM> and a slot <NUM> defined in the inferior support lug <NUM>. The slot <NUM> extends in a direction of separation of the pair of superior arms and the pair of inferior arms from each other. The protrusion <NUM> is received in the slot <NUM> whereby the protrusion can rotate in the slot and also travel along the slot. The first hinge mechanism <NUM> is constituted in the same way with the exception that it is the mirror image of the second hinge mechanism <NUM> such that, for example, the slots are in registration with each other and the protrusions are aligned and extend towards each other. The first hinge and second hinge mechanisms <NUM>, <NUM> thus allow the superior and inferior supports <NUM>, <NUM> to be rotated relative to each other and for the superior and inferior supports to be moved together and apart.

As described above, the superior and inferior endplates <NUM>, <NUM> are attached to their respective pair of arms <NUM>, <NUM>, <NUM>, <NUM> by insertion into and locking in of each arm in its respective recess <NUM>, <NUM>, <NUM>, <NUM>. When the superior and inferior endplates <NUM>, <NUM> have thus been attached to the insertion instrument <NUM>, the surgeon uses the insertion instrument to introduce the superior and inferior endplates to the patient's intervertebral space. When the superior and inferior endplates are in the intervertebral space, the surgeon manipulates the superior and inferior supports <NUM>, <NUM> of the insertion instrument <NUM> to achieve a desired separation between the superior and inferior endplates and hence height of intervertebral device and a desired angle between the superior and inferior endplates, whether the angle is lordotic and/or transverse. As described above, the hinges <NUM> in the inferior arms <NUM>, <NUM> reduce extent to which there is separation between the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM> at their proximal ends to thereby allow for the abdominal incision, by which the superior and inferior endplates are admitted, to be smaller. Where the insertion instrument <NUM> is being used in the like of an L5-S1 procedure, the disposition of the arms by virtue of the hinges reduces likelihood of the pair of inferior arms colliding with the pubic symphysis.

When the superior and inferior endplates <NUM>, <NUM> are held by the insertion instrument <NUM> in the intervertebral space, sizing trials are carried out to determine desired height and angle for the intervertebral device. Such sizing trials are carried out in accordance with a known approach and are therefore described no further. When desired height and angle have been determined, a core of appropriate height and angle is selected and inserted between the superior and inferior endplates <NUM>, <NUM> being held by the insertion instrument <NUM> in the intervertebral space. Core insertion is described below with reference to <FIG>. When the core has been inserted, the surgeon rotates each of the four arms <NUM>, <NUM>, <NUM>, <NUM> in the opposite direction to the direction to achieve locking of the arms in their recesses <NUM>, <NUM>, <NUM>, <NUM>. Upon such rotation of an arm, the protrusion <NUM> on the arm travels back along the circumferentially extending portion of channel until the protrusion reaches the linear channel defined in the wall of the recess. The protrusion <NUM> is thus positioned so that it may travel back along the linear channel to thereby allow for the distal end of the arm bearing the protrusion to be withdrawn from the recess. The insertion instrument <NUM> is thus detached from the superior and inferior endplates <NUM>, <NUM> leaving the superior and inferior endplates with core in place in the intervertebral space. The insertion instrument <NUM> is then withdrawn from the patient's body through the incision that admitted the insertion instrument at the start of the surgical procedure.

As mentioned above, a selected core is inserted between the superior and inferior endplates <NUM>, <NUM> while they are held by the insertion instrument <NUM> in the intervertebral space. <FIG> shows a core <NUM> to be inserted and a core inserter <NUM> which is used in conjunction with the insertion instrument <NUM> to insert the core. The core <NUM> has an elongate protrusion <NUM> at each transverse side at the superior surface of the core with each elongate protrusion <NUM> extending in the anteriorposterior direction. The core inserter <NUM> comprises a core inserter support <NUM> and an elongate cylindrical member <NUM>. A core inserter knob <NUM> is rotatably mounted on the core inserter support <NUM>. The elongate cylindrical member <NUM> threadedly engages with the core inserter knob <NUM> whereby the cylindrical member moves through the core inserter support upon rotation of the core inserter knob <NUM> on the core inserter support <NUM>. The core inserter support <NUM> comprises an attachment mechanism <NUM> which enables the core inserter support <NUM> to be removably and threadedly attached to the superior or inferior support <NUM>, <NUM> of the insertion instrument <NUM> and such that the cylindrical member <NUM> is directed between the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM> of the insertion instrument <NUM>. Considering the attachment mechanism <NUM> further it comprises a screw member <NUM> which threadedly engages with a bore defined in the anterior face of the superior or inferior support <NUM>, <NUM>.

As a first step during the core insertion process, the core <NUM> is positioned between the superior and inferior supports <NUM>, <NUM> of the insertion instrument <NUM> and such that the elongate protrusions <NUM> are received in respective channels defined by the superior support <NUM>. Next the core inserter <NUM> is attached by way of the attachment mechanism <NUM> to the superior or inferior support <NUM>, <NUM> and such that the operative end <NUM> of the cylindrical member <NUM> is directed between the pair of superior arms <NUM>, <NUM> and the pair of inferior arms <NUM>, <NUM>. The operative end <NUM> of the cylindrical member <NUM> therefore abuts against the core <NUM> supported by the superior support <NUM>. The surgeon rotates the core inserter knob <NUM> to increase the reach of the operative end <NUM> of the cylindrical member <NUM> between the pairs of arms to thereby push the supported core <NUM> towards the distal ends of the arms of the insertion instrument. Facing surfaces of the superior pair of arms each define a channel with each channel in registration with a respective one of two core supporting channels defined by the superior support. The core <NUM> is therefore supported by the superior pair of arms as the core is driven by the core inserter <NUM> towards the distal ends of the arms. When the core <NUM> reaches the superior and inferior endplates <NUM>, <NUM> held by the insertion instrument <NUM>, the surgeon continues to rotate the core inserter knob <NUM> to push the core between the superior and inferior endplates <NUM>, <NUM>. As the core is received between superior and inferior endplates <NUM>, <NUM>, surface profiles on the core inter-engage with cooperating surface profiles on the superior and inferior endplates to lock the superior and inferior endplates together and such that the desired height and angle, as determined by the core, are achieved.

A perspective view of an insertion instrument <NUM> according to the present invention is shown in <FIG>. The insertion instrument <NUM> comprises a superior support <NUM>, an inferior support <NUM>, one superior arm <NUM> and one inferior arm <NUM>. Each of the superior arm <NUM> and the inferior arm <NUM> is generally rectangular when viewed in plan and is of the form of a frame. The superior arm <NUM> is integrally formed with and such that it extends from the superior support <NUM>. The inferior arm <NUM> is integrally formed with and such that it extends from the inferior support <NUM>. The superior support <NUM> and the inferior support <NUM> are mechanically coupled to each other by a first hinge mechanism <NUM> and a second hinge mechanism <NUM>. The first hinge mechanism <NUM> is at a first side of the superior and inferior supports <NUM>, <NUM> and the second hinge mechanism <NUM> is at a second side of the superior and inferior supports, the first and second sides facing in opposite directions.

The first and second hinge mechanisms <NUM>, <NUM> allow the superior support <NUM> and the inferior support <NUM> to rotate relative to each other while restricting their movement together and apart and in the transverse direction. The first and second hinge mechanisms <NUM>, <NUM> also allow for movement of the superior support <NUM> and the inferior support <NUM> relative to each other in the longitudinal direction, albeit with such movement impeded by spring bias as described further below. The superior support <NUM> and the inferior support <NUM> thus rotate about a support axis which is substantially orthogonal to a longitudinal axis of the first and second arms <NUM>, <NUM>, and substantially orthogonal to a direction of separation of the superior and inferior supports. The superior arm <NUM> moves with the superior support <NUM> and the inferior arm <NUM> moves with the inferior support <NUM>. Relative rotation of the superior and inferior supports <NUM>, <NUM> therefore causes the superior arm <NUM> and the inferior arm <NUM> to rotate relative each other. Also, movement of the superior and inferior supports <NUM>, <NUM> relative to each other in the longitudinal direction moves the superior arm <NUM> and the inferior arm <NUM> relative to each other in the longitudinal direction.

Considering <FIG> further, the inferior arm <NUM> has a hinge <NUM> between <NUM> and <NUM> from the distal end of the arm. The hinge <NUM> allows for a distal portion <NUM> between the distal end and the hinge <NUM> and a proximal portion <NUM> between the hinge <NUM> and the inferior support to rotate relative to each other. The hinge <NUM> rotates about a hinge axis which is substantially parallel to the support axis whereby the distal portion <NUM> of the inferior arm <NUM> rotates towards and away from the superior arm <NUM>. In contrast, the superior arm <NUM> is unarticulated.

As described above, mechanical coupling of the superior and inferior supports <NUM>, <NUM> by way of the first and second hinge mechanisms <NUM>, <NUM> is such that the superior arm <NUM> and the inferior arm <NUM> extend generally in the same direction. The first and second hinge mechanisms <NUM>, <NUM> are of the same form and function. Each hinge mechanism <NUM>, <NUM> comprises first and second parts <NUM>, <NUM>, with the first part <NUM> integrally formed with the inferior support <NUM> whereby the first part <NUM> is immovably mounted on the inferior support. The second part <NUM> is mounted the inferior support <NUM> for movement relative to the inferior support in the longitudinal direction. The disposition of the first and second parts <NUM>, <NUM> is such that movement of the second part <NUM> moves the second part towards or away from the first part <NUM>. Each hinge mechanism <NUM>, <NUM> further comprises a spring <NUM> which is mounted in the inferior support <NUM> such that its spring bias urges the second part <NUM> towards the first part <NUM>. The opposing faces of the first and second parts <NUM>, <NUM> each define a recess. Each hinge mechanism <NUM>, <NUM> further comprises a third part in the form of a cylindrical protrusion <NUM> which is integrally formed with the superior support <NUM>. Each cylindrical protrusion <NUM> is mounted on an integrally formed lug which extends from the superior support <NUM>. The cylindrical protrusions <NUM> of the first and second hinge mechanisms <NUM>, <NUM> extend towards each other on the inferior support facing side of the superior support and such that they are in registration with each other. Relative rotation of the superior and inferior supports <NUM>, <NUM> is about the two cylindrical protrusions <NUM>. Each cylindrical protrusion <NUM> is received between a respective pair of first and second parts <NUM>, <NUM>. The bias exerted by the spring <NUM> urges the second part <NUM> towards the first part <NUM> such that the recesses defined by the opposing faces of the first and second parts <NUM>, <NUM> fit around the cylindrical protrusion <NUM>. Each cylindrical protrusion <NUM> is thus held between its respective pair of first and second parts <NUM>, <NUM>.

When the lower arm <NUM> is unbent the lower arm is at maximum reach. When the second part <NUM> is urged to greatest extent towards the first part <NUM>, the superior support <NUM> and superior arm <NUM> are thrust forward to maximum extent relative to the inferior support <NUM> and inferior arm <NUM> whereby the distal end of the superior arm <NUM> is aligned with the distal end of the inferior arm <NUM>. When the lower arm <NUM> is bent, the reach of the lower arm is reduced whereby the distal ends of the superior and inferior arms <NUM>, <NUM> are misaligned. The superior and inferior arms <NUM>, <NUM> are brought back into alignment by pulling the superior support <NUM> back against the sprung biased second parts <NUM> whereby the superior support <NUM> and superior arm <NUM> are pulled backwards relative to the inferior support <NUM> and inferior arm <NUM>. Despite the first and second parts <NUM>, <NUM> being now spaced apart from each other and such that the cylindrical protrusion <NUM> is no longer in contact with the first part (as shown in <FIG>), the recess defined in the face of the second part <NUM> presents resistance to separation of the superior and inferior supports from each other. Should the user wish to separate the superior and inferior supports from each other, the second parts <NUM> are held against the spring bias in their pulled back position and the superior support <NUM> is moved such that the cylindrical protrusions <NUM> are moved away from the second parts <NUM> while being spaced apart from the first parts <NUM>. The cylindrical protrusions <NUM> may then be withdrawn from between the pairs of first and second parts <NUM>, <NUM> to allow for separation of the superior and inferior supports from each other.

A view of a superior part of the insertion instrument of <FIG> is shown in <FIG>. The superior part comprises the previously described superior support <NUM> and superior arm <NUM>, amongst other components. The superior part further comprises an endplate gripping arrangement <NUM>. The endplate gripping arrangement <NUM> comprises first and second sprung fingers <NUM> which extend from a distal end of the superior arm <NUM>. The first and second sprung fingers <NUM> are mounted such that they are spaced apart to sufficient extent to receive an endplate component therebetween. The first and second fingers <NUM> are sprung by virtue of the material from which they are formed such that they are inherently sprung and such that the spring bias urges the distal ends of the first and second fingers apart. A superior endplate component can be received readily between the first and second fingers in this condition. The gripping arrangement <NUM> further comprise a compression mechanism which releasably engages with the first and second fingers <NUM> to compress the first and second fingers together towards their distal ends and against their spring bias. The superior endplate component is gripped by the first and second fingers <NUM> when the compression mechanism has engaged with the first and second fingers.

The compression mechanism comprises a compression body <NUM> which is movably attached to the superior arm <NUM> for movement along the superior arm. Furthermore, the compression body <NUM> is disposed on the superior arm such that movement of the compression body away from the superior support <NUM> causes the compression body to bear against a shoulder defined by each of the first and second fingers <NUM>. Bearing of the compression body <NUM> against the shoulders defined by the first and second fingers <NUM> causes the first and second fingers to deflect towards each other against their spring bias. When the compression body <NUM> is operating in this fashion, the first and second fingers <NUM> grip the superior endplate component between oppositely directed sides of the superior endplate component. When the compression body <NUM> is moved back towards the superior support <NUM>, the compression body no longer bears against the shoulders defined by the first and second fingers <NUM> to allow the first and second fingers to move apart under their spring bias and to thereby release their grip on the superior endplate component.

The compression mechanism further comprises a compression mechanism driving arrangement which is supported on the superior arm <NUM> for movement relative to the superior arm. The compression mechanism driving arrangement comprises a first driving member <NUM> and a second driving member <NUM> which are hingedly coupled to each other by a first compression mechanism hinge <NUM>. The first driving member <NUM> is coupled at its proximal end to the superior support <NUM> and is hingedly coupled at its distal end to a proximal end of the second driving member <NUM>. The second driving member <NUM> is attached to the compression body <NUM> whereby the compression body moves with the second driving member <NUM>. Movement of the first driving member <NUM> causes the second driving member <NUM> to move back and forth along the superior arm <NUM> whereby the compression body <NUM> moves between a first and second finger <NUM> compressing position and a first and second finger releasing position. The first driving member <NUM> is moved by way of a lever <NUM> which is rotatably mounted on the superior support <NUM>. The lever <NUM> defines a cam profile that is operative to lock the position of the first driving member <NUM> and hence the position of the second driving member <NUM> when the second driving member is at its greatest reach. The lock thus provided by the lever <NUM> therefore locks the grip exerted on the superior endplate component by the first and second fingers <NUM>. The first driving member <NUM> is structured to allow it to flex slightly when the lever <NUM> is moved to reduce likelihood of jamming of the compression mechanism driving arrangement.

A view of an inferior part of the insertion instrument of <FIG> is shown in <FIG>. The inferior part comprises the previously described inferior support <NUM> and inferior arm <NUM>, amongst other components. The inferior part further comprises an endplate gripping arrangement <NUM>. Form and function of the endplate gripping arrangement <NUM> of the inferior part is common to the form and function of the endplate gripping arrangement <NUM> of the superior part except as will now be described. The reader's attention is directed to the previous description of the endplate gripping arrangement <NUM> of the superior part in respect of common form and function.

The compression mechanism driving arrangement of the inferior part comprises a first driving member <NUM> and a second driving member <NUM> which are hingedly coupled to each other by a second compression mechanism hinge <NUM>. The first driving member <NUM> is coupled at its proximal end to the inferior support <NUM> and is hingedly coupled at its distal end to a proximal end of the second driving member <NUM>. The second driving member <NUM> is attached to the compression body <NUM> whereby the compression body moves with the second driving member <NUM>. Movement of the first driving member <NUM> causes the second driving member <NUM> to move back and forth along the inferior arm <NUM> whereby the compression body <NUM> moves between a first and second finger <NUM> compressing position and a first and second finger releasing position. The first driving member <NUM> is urged away from the inferior support <NUM> by a spring (not shown) mounted at the proximal end of the first driving member <NUM> which maintains by virtue of its spring bias the compression body <NUM> in the inferior endplate component gripping condition. A release button <NUM> at the proximal end of the first driving member <NUM> compresses the spring when the release button is pressed by a user. Compression of the spring releases the first driving member from the bias of the spring to in turn release the compression body <NUM> from its locked condition and thereby release the inferior endplate component from the grip exerted by the first and second fingers <NUM>. The second compression mechanism hinge <NUM> differs from the first compression mechanism hinge <NUM> as will now be described. The distal end of the first driving member <NUM> defines a slot which extends generally in a direction of separation of the superior and inferior supports <NUM>, <NUM>. The hinge pin of the second compression mechanism hinge <NUM> is received in and travels along the slot in the distal end of the first driving member <NUM> to accommodate change in relative disposition of the proximal and distal portions <NUM>, <NUM> of the inferior arm <NUM> as their extent of relative angulation changes. Furthermore, the axis of rotation of the second compression mechanism hinge <NUM> is slightly further away from the superior arm <NUM> than the axis of rotation of the hinge <NUM> between the proximal and distal portions of the inferior arm <NUM>. Having the axis of rotation of the second compression mechanism hinge <NUM> offset in this fashion causes the compression mechanism driving arrangement to increase the extent of relative angulation of the inferior arm <NUM> and such that the distal portion <NUM> of the inferior arm is urged towards the superior arm <NUM>.

The insertion instrument according to an embodiment is formed from a standard surgical instrument metal, such as stainless steel. Alternatively, the insertion instrument according to an embodiment is formed from a plastics material, such as polycarbonate or nylon. An insertion instrument formed from a plastics material is typically for single use before disposal.

Claim 1:
An insertion instrument (<NUM>) for inserting a modular intervertebral fusion device or components thereof (<NUM>, <NUM>) into an intervertebral space, the insertion instrument comprising:
a superior arm (<NUM>) mounted on a superior support (<NUM>) such that the superior arm extends from the superior support; and
an inferior arm (<NUM>) mounted on an inferior support such (<NUM>) that the inferior arm extends from the inferior support,
wherein the superior support and the inferior support are mechanically coupled to each other whereby: the superior arm and the inferior arm extend in generally a same direction such that, in use, each of the distal ends of the superior and inferior arms engage at a respective location on a modular intervertebral fusion device or component thereof; and the superior and inferior supports rotate relative to each other to provide relative rotation of the superior arm and the inferior arm, whereby there is movement together and apart of the superior arm and the inferior arm at their distal ends,
wherein one of the superior arm and the inferior arm is unarticulated between its distal end and the respective one of the superior support and the inferior support, and wherein the other one of the superior arm and the inferior arm comprises a hinge (<NUM>) between its distal end (<NUM>) and the respective one of the superior support and the inferior support, the hinge rotating the distal end of the other one of the superior arm and the inferior arm towards or away from the one of the superior arm and the inferior arm, and
wherein the insertion instrument comprises only one superior arm (<NUM>) and only one inferior arm (<NUM>), the unarticulated one of the superior arm and the inferior arm immovably mounted on the respective one of the superior and inferior supports, the articulated one of the superior arm and the inferior arm comprises proximal and distal portions with the hinge therebetween, and the proximal portion is immovably mounted on the respective one of the superior and inferior supports (<NUM>, <NUM>).