# Patent

## Title
Instrumentation and methods for inserting an intervertebral disc prosthesis

## Abstract

Embodiments of instrumentation and methods are provided for the insertion of intervertebral disc prosthesis. The instrumentation of the embodiments comprises a guide comprising at least two lateral faces, at least one upper plate, at least one lower plate, at least one retainer, a cage defining an insertion axis for the prosthesis, and an angle adjuster adapted to adjust an angle formed by the insertion axis and an antero-posterior sagittal axis; and at least one separator sized to maintain a gap between the upper vertebra and the lower vertebra. Methods for implanting a prosthesis using the disclosed instrumentation comprise implanting a pin in the median sagittal axis of a vertebrae; measuring the dimensions of the intervertebral space; choosing the prosthesis; choosing the guide; adjusting the angle adjuster; positioning the guide adjacent to the intervertebral space; inserting the prosthesis into the guide; and inserting the prosthesis into the intervertebral space.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority under 35 U.S.C. 119 to French Patent Application No. 05 06652, filed in FRANCE on Jun. 29, 2005.
TECHNICAL FIELD
The present invention relates to instrumentation for inserting intervertebral disc prostheses.
BACKGROUND OF THE INVENTION
Various types of instruments for inserting intervertebral disc prostheses are known, such as those disclosed in the French patent application FR0405899000 filed by the applicant. These instruments only allow insertion by anterior access, along the antero-posterior axis of the prosthesis. Preparation of the vertebrae between which the prosthesis is to be implanted by this type of instrumentation therefore requires opening the tissue covering these vertebrae and pushing aside the blood vessels on the anterior face of the spinal column, which generates a risk for the patient.
The embodiments disclosed herein provide instrumentation and methods that allow insertion of a prosthesis between the vertebrae, laterally or obliquely, while appropriately positioning the prosthesis in relation to the sagittal plane and the coronal plane.
Embodiments of instrumentation for the insertion of intervertebral disc prosthesis between vertebrae in accordance with the present invention comprise a guide and at least one separator. In preferred embodiments, the guide has at least two lateral faces, at least one upper plate, at least one lower plate, at least one retainer, a cage defining an insertion axis for the intervertebral disc prosthesis and having open posterior and anterior faces, and an angle adjuster adapted to adjust the angle formed by the insertion axis and an antero-posterior median sagittal axis of the vertebrae. The separators are sized to maintain a gap between the upper vertebra and the lower vertebra that is sufficient for insertion of the intervertebral disc prosthesis through the guide into the intervertebral space. For the disclosed embodiments, during the insertion of the intervertebral disc prosthesis the upper plate is disposed proximal to a plane substantially coincident with the lower surface of the upper vertebra, and the lower plate is disposed proximal to a plane substantially coincident with the upper surface of the lower vertebra. The upper plate and the lower plate are separated by a distance approximately equal to the height of the intervertebral disc prosthesis. The angle adjuster is adapted to position the guide opposite the intervertebral space between the upper vertebra and the lower vertebra and to adjust an angle formed by the insertion axis and an antero-posterior median sagittal axis defined by the intersection of a midline, substantially vertical, sagittal plane and a transverse, substantially horizontal, plane of the spinal column.
According to another feature in an embodiment, the angle adjuster comprises at least one sighting device configured for visual adjustment of the angle between the insertion axis and the antero-posterior median sagittal axis.
According to another feature in an embodiment, the angle adjuster comprises a sighting device configured for operation with at least one pin implanted into at least one of the upper vertebra and the lower vertebra and approximately oriented with the antero-posterior median sagittal axis of said vertebra to align said sighting device with the antero-posterior median sagittal axis.
According to another feature in an embodiment, the instrumentation further comprises:
at least one pin for implantation into at least one of the upper vertebra and the lower vertebra in approximate orientation with the antero-posterior median sagittal axis of said vertebra;
at least one offset adjuster adjustably linking the angle adjuster to the at least one pin.
According to another feature in an embodiment, the instrumentation further comprises:
at least one contact adjuster disposed approximately parallel to the insertion axis;
a coupling between the at least one contact adjuster and the angle adjuster allowing movement of the angle adjuster with respect to the at least one contact adjuster;
a connector configured to move along the longitudinal axis of the pin and to connect the at least one offset adjuster to the at least one pin.
According to another feature in an embodiment, the at least one pin comprises a sharp point.
According to another feature in an embodiment, the angle adjuster comprises at least one adjustment gauge indicating at least one parameter concerning the position of the guide relative to the vertebrae.
According to another feature in an embodiment, the adjustment gauge comprises a lateral offset gauge comprising a pointer pointing to graduations indicating the lateral offset of the guide from the antero-posterior median sagittal axis of the vertebrae.
According to another feature in an embodiment, the adjustment gauge comprises an angle gauge comprising a pointer pointing to radial graduations indicating the angle between the insertion axis of the intervertebral disc prosthesis and the antero-posterior median sagittal axis of the vertebrae.
According to another feature in an embodiment, the instrumentation further comprises a tightener that selectively allows or prevents rotation of the angle adjuster with respect to the guide, thereby permitting adjustment and fixation of the angle between the insertion axis of the intervertebral disc prosthesis and the antero-posterior median sagittal axis.
According to another feature in an embodiment, the at least one retainer comprises at least one groove permitting the at least one separator to slide within the groove.
According to another feature in an embodiment, the at least one retainer comprises at least one shaft providing at least one axis of rotation for the at least one separator.
According to another feature in an embodiment, the guide further comprises a stop limiting the rotation of the at least one separator about the at least one axis of rotation.
According to another feature in an embodiment, the rotation of an at least one separator is limited by an adjustable stop enabling to set the extent to which the rotation is limited.
According to another feature in an embodiment, the guide comprises at least one channel oriented substantially parallel to the insertion axis of the intervertebral disc prosthesis and configured to guide at least one part protruding from at least one surface of the intervertebral disc prosthesis.
According to another feature in an embodiment, the insertion axis of the intervertebral disc prosthesis through the guide is oriented approximately parallel to a longitudinal centerline of the guide passing through the open anterior and posterior faces of the cage.
According to another feature in an embodiment, the insertion axis of the intervertebral disc prosthesis through the guide is not oriented approximately parallel to a longitudinal centerline of the guide passing through the open anterior and posterior faces of the cage.
According to another feature in an embodiment, the instrumentation further comprises at least one chisel having at least one blade and suitable shape and dimension for engagement with the guide and for cutting at least one notch in a vertebra.
According to another feature in an embodiment, the chisel comprises a shaft, a handle at the end of the shaft opposite the at least one blade, and an adjustable stop limiting the travel of the chisel inside the guide.
According to another feature in an embodiment, the chisel comprises two blades and a spacer of suitable dimension to separate the blades by a distance approximately equal to the height of the intervertebral space.
According to another feature in an embodiment, the instrumentation further comprises an impactor having a shaft, a handle at one end of the shaft for manipulating the impactor, and at the other end of the shaft a pusher having shape and dimensions substantially conforming to at least one edge of the intervertebral disc prosthesis contacted by the pusher during use.
According to another feature in an embodiment, the impactor has an adjustable stop limiting the travel of the impactor inside the guide.
According to another feature in an embodiment, the instrumentation further comprises a holder for the intervertebral disc prosthesis and wherein the guide comprises a recess providing clearance for holder for the intervertebral disc prosthesis sufficient to position the intervertebral disc prosthesis into the guide.
According to another feature in an embodiment, the instrumentation further comprises a holder for the guide engaging at least two notches of the guide.
According to another feature in an embodiment, the holder for the guide is configured to engage the at least two notches of the guide without interfering with engagement of a recess of the guide by tools for accessing the intervertebral space or by the holder for the intervertebral disc prosthesis.
Methods for inserting intervertebral disc prostheses between two vertebrae are also provided.
General steps for preparing the vertebral site for insertion of an intervertebral disc prosthesis between two vertebrae are known, and are not an aspect of the inventive method disclosed herein. In general, such preparatory steps comprise removal of the natural biological intervertebral disc, clearing the intervertebral space, and maintaining a gap between the upper vertebra and lower vertebra with a known instrument.
Methods for inserting an intervertebral disc prosthesis in accordance with the present invention can be performed using instrumentation comprising at least one pin and a guide having at least one upper plate, at least one lower plate, a cage defining an insertion axis for the intervertebral disc prosthesis and having open posterior and anterior faces, and an angle adjuster. In a preferred embodiment, a method according the present invention comprises:

    
    
        implanting at least one pin in the median sagittal axis of one of the two vertebrae;
        measuring the dimensions of the intervertebral space;
        choosing the intervertebral disc prosthesis to be implanted;
        choosing the guide to be used;
        adjusting the angle adjuster based on an antero-posterior median sagittal axis of the spinal column, defined by the intersection of a midline, substantially vertical, sagittal plane and a transverse, substantially horizontal, plane of the spinal column, on the dimensions of the intervertebral space and on the obstacles to access to the intervertebral space, in order to set a desired angle between the insertion axis for the intervertebral disc prosthesis and the antero-posterior median sagittal axis;
        positioning the guide adjacent to the intervertebral space at the desired angle;
        inserting the intervertebral disc prosthesis into the guide through the open posterior face of the cage; and
        inserting the intervertebral disc prosthesis into the intervertebral space through the open anterior face of the cage.
    
    


According to another feature in an embodiment, the method further comprises a step of adjusting an offset adjuster for setting a lateral offset of the guide relative to the antero-posterior median sagittal axis.
According to another feature in an embodiment, the step of inserting the intervertebral disc prosthesis into the intervertebral space is performed using an impactor comprising a shaft and an adjustable stop, said step further comprising adjustment of the stop and the application of a thrust to the impactor.
According to another feature in an embodiment, the step of adjusting the angle adjuster is performed using a sighting device for aligning the guide with the antero-posterior median sagittal axis, said step further comprising placement of the sighting device in contact with the at least one pin.
According to another feature in an embodiment, the method further comprises a step of adjusting an offset adjuster of adjustable length connecting the angle adjuster of the guide to a connector connected to the pin, this adjusting step being implemented thanks to the measurements of the intervertebral space.
According to another feature in an embodiment, the step of positioning the guide adjacent to the intervertebral space further comprises translation of the guide along an axis substantially parallel to the antero-posterior median sagittal axis until the guide is proximal to the vertebrae.
According to another feature in an embodiment, the method further comprises the insertion of one or more separators into the intervertebral space.
According to another feature in an embodiment, the method further comprises the engagement of at least one of the one or more separators with at least one retainer of the guide.
According to another feature in an embodiment, the step of positioning the guide is performed with a holder for the guide.
According to another feature in an embodiment, the step of inserting the intervertebral disc prosthesis into the guide is performed with a holder for the intervertebral disc prosthesis, the guide comprising a recess providing clearance sufficient for the holder for the intervertebral disc prosthesis to position the intervertebral disc prosthesis into the guide.
According to another feature in an embodiment, the step of positioning the guide is performed with a holder for the guide configured to engage at least two notches of the guide to provide clearance for tools for accessing the intervertebral space.
According to another feature in an embodiment, the method further comprises, before inserting the intervertebral disc prosthesis into the intervertebral space, the step of preparing the intervertebral space using a chisel having at least one blade, an adjustable stop and suitable shape and dimension for engagement with the guide and for cutting at least one notch in at least one vertebra.
According to another feature in an embodiment, the method further comprises the step of clearing the intervertebral space of the bone debris generated by cutting the notch.
According to another feature in an embodiment, the method further comprises a step of removing the guide, the one or more separators, and the at least one pin after the step of inserting the intervertebral disc intervertebral disc prosthesis into the intervertebral space.
Other features and advantages of the invention will become clearer upon reading the following description of various embodiments with reference to the attached drawings.



BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 represents a perspective view of the instrumentation according to an embodiment of the invention, with a pin implanted in a vertebra and the guide facing the intervertebral space located above this vertebra.
FIG. 2 represents a top view of the instrumentation represented in FIG. 1.
FIG. 3 represents a side view of the instrumentation in FIG. 1, seen from the posterior face of the guide.
FIGS. 4A and 4B represent, respectively, a perspective view and a top view of the guide according to an embodiment of the invention.
FIGS. 5A and 5B represent perspective views of another embodiment of the guide of the instrumentation, respectively, before and after the introduction of the separating elements in the guide.
FIGS. 6A and 6B represent, respectively, a top view and a side view of the chisel according to an embodiment of the invention.
FIGS. 6C and 6D represent, respectively, a top view and a side view of the impactor on an embodiment of the invention.
FIGS. 7A and 7B represent a perspective view of an embodiment of the invention, when using a chisel.
FIG. 7B presents further details of FIG. 7A.
FIGS. 8A and 8B represent a top view of the instrumentation according to an embodiment of the invention, when using the chisel and, respectively, before and after the penetration of the chisel into the vertebra.
FIG. 9A represents a perspective view of the instrumentation according to an embodiment of the invention, when using the impactor.
FIG. 9B presents further details of FIG. 9A.
FIG. 10A represents a top view of the instrumentation according to an embodiment of the invention, during the insertion of the prosthesis in the guide.
FIG. 10B represents a top view of the instrumentation according to an embodiment of the invention, when using the impactor pushing the prosthesis inside the guide.
FIG. 11A represents a transparent view of the instrumentation according to an embodiment of the invention, when the prosthesis is being pushed into the intervertebral space by the impactor according to an embodiment of the invention.
FIG. 11b represents a prosthesis in place in the intervertebral space after the impactor has been removed.



DESCRIPTION OF EMBODIMENTS
The invention relates to an instrumentation and methods for inserting intervertebral disc prostheses (P) between vertebrae (Vi, Vs). The invention complements general surgical instruments and methods. The following description presents different, non-restrictive, embodiments of devices and methods according to various features of the invention. The different structures and steps in the various embodiments can be incorporated in the other embodiments in various combinations.
In a preferred embodiment, the instrumentation comprises a guide (1) in the shape of an open cage that can slide, by use of a movable connector (22), on at least one pin (2) implanted into a vertebra. Two pins (2), one implanted in upper vertebra (Vs) and the other implanted in the lower vertebra (Vs), and two movable connectors (22), can also be used.
Various elements of the embodiments described herein involve an antero-posterior reference axis (S). The determination of this antero-posterior reference axis will be apparent to the surgeon using the embodiments of the instrumentation and methods described. In general, the antero-posterior reference axis will lie along the intersection of a plane substantially coincident with a median sagittal (a substantially vertical plane along the midline of the spine) and a plane substantially coincident with a horizontal plane (a transverse plane, along the antero-posterior axis of the vertebrae and substantially horizontal), although other orientations may be appropriate depending on the particular characteristics of the spine and vertebrae and/or on the choice of the surgeon. For example, the antero-posterior reference axis (S) may not lie along the midline sagittal plane of the spine and may thus be Para-Sagittal and it can be inclined leftward or rightward in the antero-posterior direction of the vertebrae. The antero-posterior reference axis (S) may also not be aligned along the horizontal plane of the vertebrae and may thus be inclined upward or downward in the antero-posterior direction of the vertebrae.
A holder (not represented) for the guide can be used to place the guide (1) over the pin (2) and to make it slide until it is proximal with the vertebrae. In a preferred embodiment, the guide (1) comprises two lateral faces, at least one upper plate (17) and at least one lower plate (18) which together form a cage intended to receive the prosthesis (P) through its open posterior face and allow the insertion through its open anterior face of the prosthesis (P) between the lower (Vi) and upper (Vs) vertebrae. In use of the instrumentation, separators (10), comprising, for example, substantially rectangular plates having dimensions adapted to the height of the prosthesis (P) (generally without regard to any osteal anchors), are placed approximately parallel to the lateral faces of the guide (1) and in proximity to the lateral faces. Separators (10) maintain a sufficient gap between the vertebrae and, co-operating with the guide (1), allow the insertion of the prosthesis (P) between the vertebrae. A holder (not represented) of the prosthesis (P) allows placement of the prosthesis (P) inside the guide (1). An impactor (4) is provided for pushing the prosthesis (P) through the open cage of the guide into the intervertebral space.
Various embodiments of the invention will now further be described in detail in reference to the drawings. As shown in FIGS. 1 and 3, the guide (1) has a cage through which the prosthesis will be inserted until it reaches the intervertebral space. The cage is open on its anterior and posterior faces. The guide (1) comprises lateral faces, at least one upper plate (17) and at least one lower plate (18). In the embodiments represented in the drawings, the guide (1) has a shape substantially of a parallelepiped, with its upper plate (17) and lower plate (18) approximately parallel to each other. In an alternative embodiment (not represented), the upper plate (17) and lower plate (18) are not approximately parallel to each other and the guide (1) has, in coronal (frontal) section, a substantially trapezoidal shape. In this alternative embodiment, the separators (10) could, according to the insertion angle (A1) of the prosthesis (P), comprise non-rectangular plates such as trapezoidal plates, and/or could have different dimensions from one lateral face of the guide (1) to the other. A trapezoidal embodiment is especially suitable for implanting a prosthesis having upper and lower surfaces form an angle, thus imposing an inclination on the vertebrae between which they are intended to be implanted.
In the embodiment represented in FIGS. 5A and 5B, the guide (1) has solid lateral faces comprising substantially rectangular plates, whereas in the embodiments represented in the other figures, the lateral faces of the guide are open and comprise rods linking the upper plate (17) and lower plate (18). However, as mentioned above, the different structures described for the various embodiments of the instruments of the invention can be adapted to other instruments and/or other embodiments. Thus, the guide (1) could have open lateral faces in the embodiment represented in FIGS. 5A and 5B or even have solid lateral faces in the embodiments represented in the other figures.
The guide (1) comprises, proximate to its lateral faces, retainer (100) allowing it to co-operate with separators (10) used to maintain a gap between the vertebrae before and during the insertion of the prosthesis. The separators (10) have a shape and dimensions adapted to the height of the prosthesis (P) (generally without regard to any osteal anchors), allowing for maintenance of a sufficient gap between the vertebrae (Vi, Vs) for the introduction of the prosthesis (P) into the intervertebral space. The height of the cage of the guide (1) is adapted to the height of the prosthesis (generally without regard to any osteal anchors). Guides of different heights generally will be used for prostheses of different heights. The width of the cage of the guide (1), however, can be configured to allow the same guide to be used for the implanting of prostheses of substantially different widths, as for the two prostheses represented in FIGS. 11A and 11B. When a guide (1) is used for prostheses of substantially different widths, preferred embodiments use guiding channels (11) engaging osteal anchors on the prostheses to guide the prostheses during insertion. A surgeon, however, will preferably use a guide (1) having a size most suitable to the dimensions of and the encumbrances of access to the intervertebral space, and will implant a prosthesis having a size most suitable to the dimensions of the guide (1) and the intervertebral space.
In the embodiments represented in FIGS. 5A and 5B, the retainer (100) of the guide (1) comprises grooves on each of the lateral edges of each of the lower (18) and upper (17) plates of the guide (1). The grooves receive the separators (10), and permit the separators (10) to co-operate with the guide (1) by sliding in the grooves (100). The sliding of the separators (10) in relation to these retainers (100) allows a translation of the guide (1) in relation to the separators (10). Thus, the separators (10) could be inserted between the vertebrae (Vs, Vi) before or after the positioning of the guide (1). For example, this embodiment also allows to remove the guide (1) once the prosthesis has been implanted, while leaving the separators (10) in place between the vertebrae (Vs, Vi) to allow proper positioning of the prosthesis.
In the embodiments represented in FIGS. 1 to 4 and 7 to 11, the retainer (100) of the guide comprises shafts located proximally to the lateral faces of the guide (1). These shafts provide axes of rotation about which the separators (10) may rotate. In these embodiments of retainer (100), as seen in FIGS. 1 and 2 stops limiting the rotation can be disposed proximal to the lateral faces, towards the exterior of the guide, limiting rotation of the separators (10) about their respective axis of rotation (100). In a preferred embodiment, these stops comprise a rod (13a) having a distance to the anterior face of the guide (1) that is less than the distance of the axis of rotation (100) of the separators (10) to the anterior face of the guide (1). In another embodiment, the stops are adjustable and comprise, for example, at least one conical part (13b) screwed into at least the upper (17) or lower (18) plates of the guide. The depth of the adjustable stop can be set using the screw threads, and will adjust the limit on the rotation of the separators (10) about their axis of rotation (100). The stops limiting the rotation of the separators (10) about their axis of rotation can also comprise, as in the embodiment represented in FIGS. 4A and 4B, studs (13a) attached to the separators (10) and projecting into an opening or recess made in at least one of the lower plate (18) and upper plate (17). In this embodiment of stops (13a), the relative sizes of these studs and the opening or recess can be used to establish the limit on the rotational freedom of the separators (10).
In a preferred embodiment, instrumentation according to the invention comprises at least a pin (2) having a sharp point (21) intended to be implanted into an antero-posterior reference axis (S) of one of the vertebrae (Vi, Vs) between which the prosthesis (P) is to be implanted. Implanting the pin (2) into a vertebra provides a reference that, in conjunction with other structure of the guide (1), permits targeting the point (C) onto which the prosthesis (P) is to be centred in the intervertebral space. The guide (1) comprises at least one angle adjuster (12) allowing adjustment of the insertion axis (X) of the prosthesis (P) in relation to the antero-posterior reference axis (S) of the vertebrae, and thus the angle (A1) between the insertion axis (X) and the antero-posterior reference axis (S). The intersection between the insertion axis (X) and the antero-posterior reference axis (S) defines a point which can be set to coincide with the point (C) onto which the prosthesis (P) is to be centred in the intervertebral space. The antero-posterior reference axis (S) may lie along the intersection of a plane substantially coincident with a median sagittal plane and a plane substantially coincident with a horizontal plane, although other orientations may be appropriate depending on the particular characteristics of the spine and vertebrae and/or depending on the choice of the surgeon.
In the embodiments represented in FIGS. 4A, 4B, 5A and 5B, the angle adjuster (12) comprises a sighting device having, for instance, a back sight intended to cooperate with at least one pin (2) implanted in the median sagittal axis of at least one vertebra. The back sight preferably has a suitable shape and dimension to cooperate with the pin (2) to allow the back sight to be placed against the pin and to slide the guide (1) along the pin, thereby permitting a suitable positioning of the guide (1) along the antero-posterior reference axis (S). By providing stable placement of the guide (1) with reference to the antero-posterior reference axis (S), the sighting device (12) also facilitates adjustment (either visually or by use of a gauge or other device) of the angle (A1) between the insertion axis (X) of the prosthesis (P) and the antero-posterior reference axis (S) of the vertebrae (Vi, Vs).
In the embodiments represented in FIGS. 1 to 3 and 7 to 11, an offset adjuster (120) of adjustable length links the angle adjuster (12) to a connector (22) that can slide on pin (2). For one embodiment, the offset adjuster (120) comprises a rod with one end fixed to the connector (22) and the opposite end threaded to mate with a treaded hole in the angle adjuster (12). In another of the various alternative embodiments, the offset adjuster (120) comprises a rod attached to connector (22) but freely rotatable with respect to connector (22). In such alternative embodiment, offset adjuster (120) can be screwed in the threaded hole in angle adjuster (12) even when connector (22) is in place on pin (2). For example, a six-sided hole can be formed in the threaded end of offset adjuster (120) and used to rotate offset adjuster (120) with known tools.
The guide (1) can also comprise at least one contact adjuster (110). In various embodiments of contact adjusters (110), the contact adjuster (110) is disposed approximately parallel to the insertion axis (X) of the prosthesis (P). The angle adjuster (12) is configured to slide along the contact adjuster (110), although other adjustable couplings between the angle adjuster (12) and the contact adjuster (110) are readily apparent. In this arrangement, angle adjuster (12) can be set to the desired angle (A1) between the insertion axis (X) of the prosthesis (P) and the antero-posterior reference axis (S), and by adjusting the distance between angle adjuster (12) and connector (22) using offset adjuster (120), the intersection point between the insertion axis (X) of the prosthesis (P) and the antero-posterior reference axis (S) of the vertebrae can be made to coincide with the point (C) on which the prosthesis (P) is to be centered. By moving the angle adjuster (12) along the contact adjuster (110), the guide (1) can be brought proximal to the vertebrae (Vi, Vs) while maintaining the connector (22) in the desired proximity to the adjacent vertebra.
In various embodiments, the angle adjuster (12) of the guide (1) comprises an adjustment gauge. The adjustment gauge can be configured to indicate one or more adjustment of the guide (1), including, for example, the angle (A1) between the insertion axis (X) of the prosthesis (P) and the antero-posterior reference axis (S) and/or the length of the offset distance between angle adjuster (12) and connector (22).
The adjustment gauge embodiment illustrated in FIG. 2 comprises a lateral offset gauge. In this embodiment, the lateral offset gauge indicates the length of the offset distance between angle adjuster (12) and connector (22), indirectly measuring the offset of the guide (1) laterally from the antero-posterior reference axis (S). The lateral offset gauge comprises a pointer (1211) attached to the angle adjuster (12) and located proximal to graduations (1212) made in a surface of the offset adjuster (120). The position of the pointer (1211) in relation to the graduations (1212) indicates the length of the offset distance between angle adjuster (12) and connector (22) and therefore the lateral offset of the guide (1) in relation to the pin (2).
The adjustment gauge embodiment illustrated in FIG. 2 further comprises an angle gauge indicating the angle (A1) between the insertion axis (X) of the prosthesis (P) and the antero-posterior reference axis (S). In this embodiment, the angle gauge comprises a pointer (1221) attached to the angle adjuster (12) and located proximal to radial graduations (1222) made in the surface of the guide (1). The position of the pointer (1221) in relation to the graduations (1222) indicates the angle (A1) along which the prosthesis (P) will be implanted in relation to the antero-posterior reference axis (S) of the vertebrae (Vs, Vi).
In an alternative embodiment, a tightener is provided that selectively allows or prevents rotation of the angle adjuster (12) with respect to the cage of the guide (1). The tightener permits adjustment of the angle (A1) between the insertion axis (X) of the prosthesis (P) and the antero-posterior reference axis (S) by allowing rotation of the angle adjuster (12), and permits fixation of that angle (A1) in proper adjustment by preventing rotation of the angle adjuster (12).
In the disclosed embodiments, the pin (2) is intended to be implanted in a horizontal transverse plane of the vertebrae. Two pins (2) can also be used, along with two angle adjuster (12), for example, placed one on one of the upper plate (17) and one on the lower plate (18) as shown in FIG. 3. However, the instrumentation also may use a pin (2) to be implanted other than in a horizontal transverse plane of the vertebrae. For example, the pin (2) may be implanted in an inclined manner in the sagittal plane with its point (21) oriented towards the bottom of the spinal column. In that configuration, the guide (1) could be provided with a single angle adjuster (12) on one of the upper plate (17) or lower plate (18), but still be held in the suitable horizontal position by using to the adjustable offset adjuster (120) and the angle adjuster (12).
Some prostheses have osteal anchors (51) on the surfaces that contact adjacent vertebrae. For example, winglets on the prosthesis can be provided to engage notches made in the surfaces of the vertebrae. The surfaces of the vertebrae engaged by the osteal anchors (51) of this type of prosthesis therefore must be prepared before insertion of the prosthesis. Accordingly, in a preferred embodiment the instrumentation comprises a chisel (3) used to prepare intervertebral space. The chisel (3) has suitable shape and dimension to penetrate into the open cage of the guide (1) and pass through the guide (1) to make cuttings on the vertebrae that will be engaged by an osteal anchor (51). In a preferred embodiment, at least one plate among the upper (17) and lower (18) plates of the guide (1) comprises a guiding channel (11) oriented along the insertion axis (X) of the prosthesis (P). This guiding channel (11) has a shape and dimensions adapted to the shape and dimensions of an osteal anchor (51) of the prosthesis (P). The notch made in the vertebra using the chisel (3) assists centering of the prosthesis in relation to the point (C). In the embodiments represented in the drawings, the guiding channel (11) defining the insertion axis (X) of the prosthesis is not approximately parallel to the longitudinal centerline (L) passing through the anterior and posterior open faces of the guide (1), but the guiding channel (11) can obviously be made so as to define an insertion axis (X) of the prosthesis approximately parallel to the longitudinal centerline passing through the anterior and posterior faces of the guide (1).
In a preferred embodiment, the chisel (3) comprises a shaft (30) having, at one of its ends, at least one blade (32) of suitable shape and dimension for engagement with the guiding channel (11) of the guide (1) and for cutting a notch in a vertebra complementary with the shape and dimension of an osteal anchor (51). The shaft has, at its other end, a handle (35) allowing positioning of the blade (32) into the guiding channel (11) manipulating of the chisel to make a notch in the vertebra for the osteal anchor (51) of the prosthesis (P). An adjustable stop (31) on the shaft (30) can limit the travel of the chisel (3) in the axis (X) of the guide (1) and therefore limit the length of the notch, which can correspond to length of the osteal anchor (51). In the embodiment in FIGS. 6A and 6B, the chisel (3) comprises two blades (32) held apart from each other by a spacer (33) of suitable dimension to separate the blades (32) by a distance approximately equal to the height of the intervertebral disc prosthesis (P) (generally without regard to any osteal anchors). Using two guiding channels (11), the chisel (3) can be used to simultaneously form two notches of suitable dimensions and positions to receive the osteal anchors (51) assembled on the upper and lower surfaces of the prosthesis (P).
In an embodiment of the invention, the instrumentation comprises an impactor (4) as shown in FIGS. 6C and 6D used to move the prosthesis (P) through the cage of the guide (1) into the intervertebral space. The impactor (4) comprises a shaft (40), a handle (45) at one end of the shaft for manipulating the impactor, and at the other end of the shaft a pusher (42) having shape and dimensions substantially conforming to the edges of the intervertebral disc prosthesis (P) contacted by the pusher (42) during use. The height and width of the pusher (42) can be substantially equal, respectively, to the height (generally without regard to any osteal anchors) and the width of the prosthesis. (P). An adjustable stop (41) on the shaft (40) of the impactor (4) can limit the travel of the impactor (4) in the insertion axis (X) of the prosthesis (P) and therefore control the depth to which the prosthesis (P) will be inserted into the intervertebral space. The stop (41) therefore can assist centring the prosthesis (P) in relation to the point (C).
In an embodiment of the invention, the instrumentation can comprise a holder (not shown) for the prosthesis (P). As shown in the drawings, at least one of the upper plate (17) and the lower plate (18) comprises a recess (111) providing clearance of the holder for the prosthesis (P) and allowing the prosthesis (P) to be placed in the guide (1) with the holder. Such holder for the prosthesis (P) may consist, for example, of forceps or pliers or tweezers of a known type, with shape and dimensions adapted to insert the prosthesis (P) in the guide (1) by engaging the recess (111).
In an embodiment of the invention, the instrumentation can comprise a holder (not shown) for the guide (1). The holder can assist positioning the guide (1) in suitable position in contact with the vertebrae (Vi, Vs). The holder co-operates with at least two notches (112) made on at least one of the upper plate (17) and the lower plate (18). As represented in drawings, the notches (112) are located in the recess (111) of the guide (1). Such holder for the guide (1) may consist, for example, of dilating forceps or opening pliers, or opening tweezers of a known type, with shape and dimensions adapted to co-operate with the notches (112) while leaving the recess (111) accessible to forceps or pliers or suitable tools for accessing the intervertebral space. For example, the holder for the guide (1) may consist of opening pliers having opening ends curved in a direction approximately orthogonal to the direction of the opening of the pliers. These curved ends thus co-operate with the notches (112) in the recess (111) and may have dimensions adapted so that, when they co-operate with the notches (112), they do not substantially protrude from the notches (112) inside the recess (111). Such holder will thus hold the guide (1) while leaving a recess (111) accessible for the clearance of pliers or small tweezers or any suitable tools for accessing the intervertebral space through the guide (1). The recess (111) may also be accessible for the clearance of the holder for the prosthesis (P) and for the positioning of the prosthesis (P) into the guide (1), if the holder has still not been removed at this step.
The various embodiments of the invention described above provide instrumentation for implanting an intervertebral disc prosthesis (P) between the vertebrae (Vs, Vi). The use of the instrumentation will now be described, providing detail of the steps taken to implant the prosthesis.
As aforementioned, the invention compliments general surgical instruments and methods, which are not an aspect of the inventive method disclosed herein and will not be described. In addition, the prerequisite steps for preparing the patient and access to the vertebrae, for example from the anterior face, will not be described in detail. Prior to the implanting itself of the prosthesis (P), the surgeon creates an access to the vertebrae and removes the fibro-cartilaginous tissue of the natural biological intervertebral disc. Generally, separators (tweezers, according to a commonly used designation) of a known type maintain a gap between the vertebrae during the removal of the natural biological disc by the surgeon. The natural gap of the vertebrae will have been measured beforehand to determine the height (generally without regard to any osteal anchors) of the prosthesis (P) to be implanted in the intervertebral space and, consequently, the height of the guide (1) that is to be chosen for implantation. Measuring the height of the intervertebral space also allows determination of the height of the separators (10), which is chosen to maintain the gap required for inserting the prosthesis (P) between the vertebrae. The guide (1) will thus be chosen according to the height of these separators (10) and the dimensions of the prosthesis (P) in the horizontal plane, which will depend on the dimensions of the vertebrae and the encumbrances to accessing the intervertebral space.
During the removal of the natural biological disc by the surgeon, separators (tweezers) commonly used are too cumbersome for the rest of the operation and are thus replaced by a wedge (called “spacer” or “bougie”, according to a commonly used designation in English or French, respectively) whose height will have been chosen so as to preserve the natural gap of the vertebrae and to correspond to the height of the prosthesis (P) (generally without regard to any osteal anchors).
The removal of the natural biological intervertebral disc can be preceded or followed by a step of implanting at least one pin (2) of the instrumentation in at least one of the vertebrae (Vi, Vs) between which the prosthesis is to be implanted. So that the pin (2) provides a symmetrical reference in relation to the vertebrae, the implanting of the pin (2) is performed by placing it, preferably horizontally, along the antero-posterior reference axis (S) of the vertebra. The dimensions of the guide (1) chosen for implanting the prosthesis will affect the height in the vertebra for implantation of pin (2), which should enable the angle adjuster (12) to place the guide (1) opposite the intervertebral space with its upper plate (17) and lower plate (18) in contact with the respectively upper and lower surfaces of the respectively upper and lower vertebrae. In a known manner, the surgeon measures the exact dimensions of the vertebrae, using a known measuring device. The measuring of the vertebrae, notably along the antero-posterior axis, informs the surgeon of the depth of the intervertebral space and allows the surgeon to determine the ideal dimensions of the prosthesis (P) in the horizontal plane and to calculate, as a function of the dimensions of the measured vertebrae and of the chosen prosthesis, the position of the point (C) on which the prosthesis (P) is to be centered. By taking a radiograph of the vertebra in which the pin (2) was implanted, for example using a known image intensifier, the surgeon can also control the proper positioning of the point (21) of the pin in the vertebra, for example its alignment on the median sagittal axis. The pins (2) are short and comprise, for example, small diameter rods. The small dimensions of the pins allow the surgeon to possibly recommence the step of implanting the pin (2) into the vertebra if he considers that the position of the point (21) is unsatisfactory.
Once these measurements have been made, the surgeon has all the information necessary to choose the most appropriate guide (1) and prosthesis (P). According to the embodiment of the guide (1) chosen by the surgeon, the surgeon adjusts, according to the gathered measurements, the angle adjuster (12) to accurately target the point (C) on which the prosthesis (P) is to be centered in the intervertebral space.
The positioning of the guide (1) opposite the intervertebral space can be performed using a holder for the guide or without the use of such a holder. Among other embodiments of the invention, the surgeon can choose between separators (10) that slide in the grooves of the retainer (100) or separators (10) that rotate about their axes of rotation on shafts (100). For separators (10) that slide in the grooves of the retainer (100), the surgeon inserts separators (10) in the intervertebral space, removes the known wedge (bougie or spacer), and slides the guide (1) on the separators (10) to bring the guide (1) proximal to the vertebrae. For separators (10) that rotate about their axes of rotation on shafts (100), the surgeon inserts the separators (10) assembled on shafts (100), removes the known wedge (bougie or spacer), and drives the separators (10) into the intervertebral space until the guide is proximal with the vertebrae.
The surgeon may choose different embodiments of the angle adjuster (12) to more readily facilitate placement of the prosthesis (P) centered at point (C). According to the encumbrance of the surgeon's access to the vertebrae, the surgeon will choose one of the embodiments described below so as to insert the prosthesis along the antero-posterior sagittal axis or along an inclined axis.
In the embodiment of the instrument described above in which the angle adjuster (12) comprise a sighting device created by a back sight, and preferably in the case where the prosthesis can be implanted straight on and does not require an oblique insertion, the surgeon targets the point (C) by placing the sighting device in the median sagittal axis of the vertebrae marked by at least one pin (2) implanted in at least one vertebra. The back sight preferably has a suitable shape and dimension to co-operate with the pin (2), so as to allow the back sight to be placed against the pin and to slide the guide (1) along the pin, thereby ensuring suitable positioning of the guide in relation to the vertebrae. The surgeon inserts the prosthesis (P) it into the cage of the guide (1) though the cage's open posterior face. A holder for the prosthesis can be used that allows, as mentioned above, insertion of the prosthesis (P) into the cage of the guide while the holder for the guide is still in its place and holding the guide in contact with the vertebrae. The impactor (4) allows the surgeon to implant the prosthesis between the vertebrae by pushing on the handle (45) of the impactor (4) or by hitting, for example with a hammer, on this handle (45). The adjustable position of the stop (41) on the shaft (40) of the impactor (4) will have already been set according to the distance of point (C) on which the prosthesis is to be centred between the vertebrae, in relation to the anterior face of the vertebrae. The adjusting of the position of the stop naturally takes into account the size of the pusher (42) of the impactor (4) and the diameter of the prosthesis (P).
According to the vertebrae (Vi, Vs) between which the prosthesis (P) is to be implanted, implanting of the prosthesis (P) along the antero-posterior sagittal axis may not necessarily be the easiest or least risky solution. For example, the vena cava and the aorta, which are major life-supporting blood vessels, pass in front of the lumbar vertebrae and considerably encumber the access to the anterior face of such vertebrae. The surgeon may therefore prefer to implant the intervertebral disc prosthesis (P) along an oblique axis of insertion, such as an antero-lateral axis in the case of access to the vertebrae from the anterior face. Some of the embodiments of the invention facilitate insertion of the prosthesis (P) obliquely, for example, by use of an angle adjuster (12) to set an angle (A1) between the insertion axis (X) of the prosthesis and the antero-posterior reference axis (S).
The small diameter pins (2) can be implanted in the median sagittal plane of the vertebrae without having to shift to any great extent the tissue and/or the organs passing over the anterior face of the vertebrae. The angle (A1) created between the insertion axis (X) of the prosthesis and the antero-posterior reference axis (S), as well as the magnitude of the offset of the guide (1) on one side of the vertebrae, will already have been determined according to the encumbrances to access to the vertebrae (Vi, Vs), the size of the vertebrae (Vi, Vs), and the size of the prosthesis (P). Thus, adjusting the angle (A1) and the offset of guide (1) from the antero-posterior reference axis (S) permits the intersection the axis of insertion (X) and of the antero-posterior reference axis (S) to coincide with the point (C) on which the prosthesis is to be centred.
Offset adjuster (120) can be used to establish the offset of guide (1) from the antero-posterior reference axis (S), for example, by screwing to a greater or lesser degree a threaded end of offset adjuster (120) into a threaded hole made in the angle adjuster (12). As mentioned above, adjustment of the length of the offset adjuster (120) can be performed before or after the connector (22) is placed on the pin (2), depending on the chosen embodiment. The sliding of the connector (22) over the pin (2) allows the guide (1) to be brought proximal to the vertebrae, with its anterior face opposite the intervertebral space. Other steps for implanting can be identical to those previously described, for example by using the impactor (4) of which the position of the stop (41) on the shaft (40) of the impactor (4) will already have been set according to the distance of the point (C) in relation to the anterior face of the vertebrae and according to the size of the prosthesis (P).
If the prosthesis comprises osteal anchors (51) fixed to the surfaces of the prosthesis (P), the chisel (3) is used to make notches in the vertebrae of shape and dimension complementary with the shape and dimension of the osteal anchors (51). The handle (35) of the chisel (3) can be used to push, or perhaps use strikes of a hammer, and pull the chisel (3) to make such notches. As mentioned above, the shape and dimension of the different embodiments of the chisel (3) are adapted to the type of prosthesis (P) to be implanted and to the type of osteal anchors (51). After preparing the intervertebral space with the chisel (3), the surgeon removes the chisel (3) from the inside of the guide (1) and removes the fragments of bone generated by making the notches. The prosthesis is implanted between the vertebrae using the impactor (4).
Once the prosthesis has been properly placed in the intervertebral space, the surgeon removes the guide (1), the separators (10) and the pin(s) (2).
Although the present invention has been described in detail, it will be apparent to those skilled in the art that many embodiments taking a variety of specific forms and reflecting changes, substitutions and alterations can be made without departing from the spirit and scope of the invention. Therefore, the described embodiments illustrate but do not restrict the scope of the claims.

## Claims

1. Instrumentation for inserting an intervertebral disc prosthesis having a height, the instrumentation comprising:
a guide comprising
at least two lateral faces,
at least one upper plate,
at least one lower plate separated from the at least one upper plate by a distance at least equal to the height of the intervertebral disc prosthesis,
at least one retainer,
a cage defining an insertion axis for the intervertebral disc prosthesis and having open posterior and anterior faces, the cage being configured to receive the prosthesis through the open posterior face and to allow the insertion of the intervertebral disc prosthesis through the open anterior face into an intervertebral space between an upper vertebra and a lower vertebra, and
an angle adjuster adapted to position the guide opposite the intervertebral space and to adjust an angle formed by the insertion axis and an antero-posterior reference axis;

at least one separator sized to maintain a gap between the upper vertebra and the lower vertebra, the gap being sufficient for insertion of the intervertebral disc prosthesis through the guide into the intervertebral space between the upper vertebra and the lower vertebra;
at least one pin for implantation into at least one of the upper vertebra and the lower vertebra in approximate orientation with the antero-posterior reference axis of said vertebra;
at least one offset adjuster adjustably linking the angle adjuster to the at least one pin;
at least one contact adjuster disposed approximately parallel to the insertion axis;
a coupling between the at least one contact adjuster and the angle adjuster allowing movement of the angle adjuster with respect to the at least one contact adjuster; and
a connector configured to move along the longitudinal axis of the pin and to connect the at least one offset adjuster to the at least one pin.

2. Instrumentation of claim 1 in which the angle adjuster comprises at least one sighting device configured for visual adjustment of the angle between the insertion axis and the antero-posterior reference axis.

3. Instrumentation of claim 1 in which the angle adjuster comprises a sighting device configured for operation with the at least one pin for implantation into at least one of the upper vertebra and the lower vertebra and approximately oriented with the antero-posterior reference axis of said vertebra to align said sighting device with the antero-posterior reference axis.

4. Instrumentation of claim 1 in which the at least one pin comprises a sharp point.

5. Instrumentation of claim 1 further comprising a tightener that selectively allows or prevents rotation of the angle adjuster with respect to the guide, thereby permitting adjustment and fixation of the angle between the insertion axis of the intervertebral disc prosthesis and the antero-posterior reference axis.

6. Instrumentation of claim 1 in which the at least one retainer comprises at least one shaft providing at least one axis of rotation for the at least one separator.

7. Instrumentation of claim 6 in which the guide further comprises a stop limiting the rotation of the at least one separator about the at least one axis of rotation.

8. Instrumentation of claim 6 in which the rotation of an at least one separator is limited by an adjustable stop enabling to set the extent to which the rotation is limited.

9. Instrumentation of claim 1 in which the guide comprises at least one channel oriented substantially parallel to the insertion axis of the intervertebral disc prosthesis and configured to guide at least one part protruding from at least one surface of the intervertebral disc prosthesis.

10. Instrumentation of claim 1 in which the insertion axis of the intervertebral disc prosthesis through the guide is oriented approximately parallel to a longitudinal centerline of the guide passing through the open anterior and posterior faces of the cage.

11. Instrumentation of claim 1 in which the insertion axis of the intervertebral disc prosthesis through the guide is not oriented approximately parallel to a longitudinal centerline of the guide passing through the open anterior and posterior faces of the cage.

12. Instrumentation of claim 1 further comprising a holder for the intervertebral disc prosthesis and wherein the guide comprises a recess providing clearance for holder for the intervertebral disc prosthesis sufficient to position the intervertebral disc prosthesis into the guide.

13. Instrumentation of claim 1 further comprising a holder for the guide engaging at least two notches of the guide.

14. Instrumentation of claim 13 in which the holder for the guide is configured to engage the at least two notches of the guide without interfering with engagement of a recess of the guide by tools for accessing the intervertebral space or by the holder for the intervertebral disc prosthesis.

15. Instrumentation for inserting an intervertebral disc prosthesis having a height, the instrumentation comprising:
a guide comprising
at least two lateral faces,
at least one upper plate,
at least one lower plate separated from the at least one upper plate by a distance at least equal to the height of the intervertebral disc prosthesis,
at least one retainer,
a cage defining an insertion axis for the intervertebral disc prosthesis and having open posterior and anterior faces, the cage being configured to receive the prosthesis through the open posterior face and to allow the insertion of the intervertebral disc prosthesis through the open anterior face into an intervertebral space between an upper vertebra and a lower vertebra, and
an angle adjuster adapted to position the guide opposite the intervertebral space and to adjust an angle formed by the insertion axis and an antero-posterior reference axis, the angle adjuster comprising at least one adjustment gauge indicating at least one parameter concerning the position of the guide relative to the vertebrae, the adjustment gauge comprising a lateral offset gauge comprising a pointer pointing to graduations indicating the lateral offset of the guide from the antero-posterior reference axis of the vertebrae; and

at least one separator sized to maintain a gap between the upper vertebra and the lower vertebra, the gap being sufficient for insertion of the intervertebral disc prosthesis through the guide into the intervertebral space between the upper vertebra and the lower vertebra.

16. Instrumentation for inserting an intervertebral disc prosthesis having a height, the instrumentation comprising:
a guide comprising
at least two lateral faces,
at least one upper plate,
at least one lower plate separated from the at least one upper elate by a distance at least equal to the height of the intervertebral disc prosthesis,
at least one retainer,
a cage defining an insertion axis for the intervertebral disc prosthesis and having open posterior and anterior faces, the cage being configured to receive the prosthesis through the open posterior face and to allow the insertion of the intervertebral disc prosthesis through the open anterior face into an intervertebral space between an upper vertebra and a lower vertebra, and
an angle adjuster adapted to position the guide opposite the intervertebral space and to adjust an angle formed by the insertion axis and an antero-posterior reference axis, the angle adjuster comprising at least one adjustment gauge indicating at least one parameter concerning the position of the guide relative to the vertebrae, the adjustment gauge comprising an angle gauge comprising a pointer pointing to radial graduations indicating the angle between the insertion axis of the intervertebral disc prosthesis and the antero-posterior reference axis of the vertebrae; and

at least one separator sized to maintain a gap between the upper vertebra and the lower vertebra, the gap being sufficient for insertion of the intervertebral disc prosthesis through the guide into the intervertebral space between the upper vertebra and the lower vertebra.