US20110282457A1 - Connectable interbody implant - Google Patents

Abstract

An intersomatic implant (1a,1b) maintains bone graft material in a receiving cavity formed in a disc in order to obtain intervertebral fusion. The implant (1a,1b) includes of a plurality of parts provided with means for in situ connection of two consecutive parts. Instruments (33) are used to connect these implants (1a,1b) and a tool assists in introducing these implants (1a,1b) into the cavity formed in the disc.

Description

BACKGROUND
• The present invention generally concerns the field of interbody implants with which it is possible to obtain fusion of two adjacent vertebrae when the disc separating them has been damaged, and more specifically, but not exclusively, it concerns the implants commonly referred to as “interbody cages” or “intersomatic cages” which are intended to receive a bone graft and to maintain the latter in place during the fusion, after partial excision of the damaged disc.
• When a disc separating two vertebrae has degenerated and interbody fusion is necessary, this can be obtained by implanting interbody cages in cavities formed in the degenerated disc. The interbody cages are often fitted by the anterior route, in which case it is possible only to provide a single cage of this type, implanted in the central region of the disc. However, when the lumbar region is involved, an approach by the posterior route is possible on account of the fact that the nervous system there is less dense than in the other regions of the spine. There is therefore less risk of damaging the nervous system there during the surgical intervention. Nevertheless, the presence of the medullary canal in practice requires the use of two small sized interbody implants that are symmetrically arranged relative to the axis of the spine. These bilateral implants are separate components that are not connected to one another. There is therefore a risk of relative displacement or expulsion of the implants, especially since an implant of small size is less stable, in particular rotationally less stable, than an implant of larger size.
SUMMARY
• One object of the present invention is to provide a unique interbody implant for spinal fusion and corresponding method to facilitate implantation of the implant.
• In the case of intervertebral fusion by a posterior approach performed in the lumbar region, one object of the invention is to provide surgeons with the possibility of using interbody implants having a high degree of stability, while at the same time guaranteeing, as in current practice, a high level of safety during fitting of the implants.
• To this end, the invention relates to an interbody implant for inserting and maintaining a bone graft in place in a receiving seat formed in a disc with a view to obtaining intervertebral fusion, characterized in that it consists of a plurality of parts provided with means for in situ connection of two consecutive parts.
• According to a first variant of the invention, the interbody implant comprises a first part intended to be oriented in the posterior-anterior direction of the spine, and a second part oriented substantially perpendicular to the first part, the parts being connected by a transition portion, the front face of the second part of the implant comprising either a protrusion, making this implant a male implant, or a receiver for inserting and holding the protrusion, making this implant a female implant, in order to achieve and maintain a connection between such a male implant and such a female implant.
• The male interbody implant can comprise, on the front face of its second part, a protrusion which successively comprises starting from the front face:
• • a first substantially cylindrical portion having a given diameter “D1”;
  • a second substantially cylindrical portion having a diameter “D2” greater than “D1”;
  • and a substantially frustoconical portion whose initial diameter is equal to “D2” and decreases as the distance from the front face increases.
• The female interbody implant can comprise, on the front face of its second part, a receiver delimited externally by elastic tongues which finish in a bulge.
• The above-mentioned male interbody implant and female interbody implant may form a unit, the shape and the dimensions of the tongues of the female implant and of their bulges making them able to cooperate with the protrusion of the male implant in order to achieve and maintain a connection of the two implants.
• The male interbody implant can comprise, on the front face of its second part, a protrusion whose general external shape is that of a cylinder portion whose cross section has a circumference which extends over an angle greater than 180° in such a way as to define two receiving seats in the area of its zones of connection with the front face.
• The female interbody implant can comprise, on the front face of its second part, two elastic tabs, which between them define a receiver.
• The above-mentioned male interbody implant and female interbody implant may form a unit, the shape and the dimensions of the elastic tabs of the female implant making them able to permit insertion of the protrusion of the male implant into the receiver, the ends of the elastic tabs being inserted into the receiving seats in order to achieve and maintain a connection of the two implants.
• The invention also relates to an instrument for in situ connection of a male interbody implant and a female interbody implant of the above types, characterized in that it comprises two rods which are each equipped with means for fixing to the front face of the first part of an implant, and means for moving the rods towards one another while holding them in parallel positions.
• The means for moving the rods towards one another can comprise:
• • two tubes in which the rods can be inserted and blocked;
  • a first transverse rod connecting the front end of the first tube to the rear end of the second tube, and a second transverse rod connecting the front end of the second tube to the rear end of the first tube, the transverse rods intersecting in the area of an articulation permitting their rotation about a common hinge pin perpendicular to the plane including the tubes;
  • means for articulating the first transverse rod about a hinge pin perpendicular to the plane including the tubes, situated towards the front end of the first tube and held fixed in translation, and means for articulating the first transverse rod about a hinge pin perpendicular to the plane including the tubes, situated towards the rear end of the second tube and movable in translation in a receiving seat extending along the second tube;
  • means for articulating the second transverse rod about a hinge pin perpendicular to the plane including the tubes, situated towards the front end of the second tube and held fixed in translation, and means for articulating the second transverse rod about a hinge pin perpendicular to the plane including the tubes, situated towards the rear end of the first tube and movable in translation in a receiving seat extending along the first tube;
  • and means for moving the tubes towards one another in a controlled manner.
• The means for moving the tubes towards one another can comprise a receiver articulated in rotation about a hinge pin perpendicular to the plane including the tubes and passing through the second transverse rod in proximity to the first tube, an externally threaded rod of which one end is inserted in the receiver and the other end is inserted in the internal space of a tube equipped with a thread corresponding to the thread of the rod, and means allowing the surgeon to turn the tube in order to regulate the depth of insertion of the rod in the tube, and a receiving seat traversed by the rod and articulated in rotation about a hinge pin perpendicular to the plane including the tubes and passing through the first transverse rod in proximity to the second tube.
• The instrument can comprise a spring around the threaded rod, bearing on the receiver and the receiving seat.
• According to a second variant of the invention, the interbody implant can comprise a central part and two lateral parts, which can be connected to the central part by connection means.
• The connection means can comprise tapped holes formed in the end faces of the central part, and screws which can be inserted into the tapped holes and whose heads can come to rest on bearing surfaces formed on the lateral parts.
• An instrument set for fitting an implant of the above type in place can comprise:
• • a rod provided with means, at one of its ends, for fixing the central part of the implant;
  • and two tools formed by a sheath provided at one of its ends with means permitting one of the lateral parts of the implant to be maintained there, and a screwdriver arranged inside the sheath and provided with an impression which can cooperate with the screw.
• The instrument set preferably also comprises:
• • a crosspiece with which it is possible to maintain the rod and the tool in determined respective angular positions during fitting of the first of the two lateral parts of the implant,
  • a crosspiece with which it is possible to maintain the two tools in determined respective angular positions during fitting of the second of the lateral parts of the implant.
• A tool to assist in introducing an interbody implant into a receiving seat formed in an intervertebral disc may comprise:
• • a first part including a protector guide of which one end, intended to remain at the inlet of the receiving seat during the introduction, has a width “1” substantially equivalent to the height of the receiving seat and is equipped with stops intended to bear against the outer surfaces of the vertebrae;
  • a second part including a distractor element placed at the end of a rod;
  • a third part including a tubular element into which the rod of the second part can be inserted;
  • and means permitting assembly of the three parts in a position permitting insertion of the end of the protector guide and the distractor element into the receiving seat, then disassembly of the three parts in such a way as to leave only the end of the protector guide in the receiving seat.
• The means permitting assembly and disassembly of the three parts can include:
• • protrusions formed on the sides of the end of the protector guide;
  • receiving seats formed on the upper and lower faces of the distractor element in order to insert the protrusions of the protector guide therein;
  • at least one stud formed on the anterior face of the tubular element and at least one corresponding notch formed on the posterior face of the distractor element;
  • an orifice formed on the rod of the second part, a tapped hole formed on the tubular element of the third part, and a threaded element which can be inserted into the tapped hole and the orifice in such a way as to block the second and third parts relative to one another while at the same time blocking the protrusions of the protector guide in their receiving seats provided on the distractor element.
• As will have been understood, the invention lies in providing a possibility of interconnection between two or more interbody implants while or after they are/have been placed separately in the degenerated disc (in other words in situ) in such a way as to form there a stable and integrated platform. Thus, in functional terms, a single implant is obtained which is made up of a plurality of segments connected to one another, without the disadvantages and risks, which would be involved in implanting a single monoblock implant by a posterior approach.
• Further objects, embodiments, forms, aspects, features, benefits, and/or advantages will be apparent from the description and drawings provided herewith.
BRIEF DESCRIPTION OF DRAWINGS
• The present invention will be better understood on reading the following description in which reference is made to the attached figures:
• FIG. 1 shows, viewed in perspective, of two half-implants, male (FIG. 1A) and female (FIG. 1B), according to one embodiment of the present invention;
• FIG. 2 shows, in a plan view (FIG. 2A) and in aside cross-sectional view along2B-2B, the two half-implants fromFIG. 1 in the connected state;
• FIG. 3 shows, viewed in perspective, a second example of two half-implants, male (FIG. 3A) and female (FIG. 3B), according to the invention;
• FIG. 4 shows, viewed in perspective, the two half-implants fromFIG. 3 in the connected state;
• FIG. 5 shows, viewed in perspective, an instrument designed for the positioning and connection of two half-implants according to the invention;
• FIG. 6 shows, in a plan view and longitudinal section, a variant of the instrument inFIG. 5; and
• FIG. 7 shows, in perspective, an instrument to assist in fitting a half-implant according to the invention, on the one hand in the assembled state (FIG. 7A) and on the other hand in the disassembled state (FIGS. 7B,7C,7D).
• FIG. 9 shows, in perspective, a rod which is used when fitting the implant inFIG. 8;
• FIG. 10 shows a tool which is also used during this fitting; and
• FIGS. 11 and 12 show, in perspective, two stages of this fitting.
DESCRIPTION OF SELECTED EMBODIMENTS
• For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the illustrated device, and further applications of the principles of the invention as illustrated or described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
• To implant the connectable interbody implants according to one embodiment of the invention by the posterior route, the surgeon begins, in a conventional manner, by partially resecting the articular facets of the two vertebrae concerned in the operation so as to gain access to the degenerated disc. The surgeon then performs a partial discectomy so as to create fusion beds corresponding to the external shape of each of the half-implants, and the surgeon prepares the vertebral plates so as to permit subsequent fusion of the vertebrae using bone grafts enclosed by the implants which are going to be fitted. The above-described discectomy and vertebral plate preparation techniques are widely known. U.S. Pat. No. 6,174,311 issued on Jan. 16, 2001 to Branch et al., for example, describes such techniques. In one embodiment of the present invention, the two cavities formed during the partial discectomy must communicate with one another in the anterior region of the disc, in such a way as to permit connection of the half-implants in the last stage of their fitting. In one form, this technique can be performed with tools such as those described in the published PCT patent application WO-A-0128469, which is hereby incorporated by reference. Preparing the vertebral plates and maintaining the desired intervertebral distance during fitting of the half-implants can be achieved with the aid of an instrument, which will be described below. After the preparation stage, the half-implants are inserted. Two examples of pairs of such half-implants will be described herein, it being understood that these examples are nonlimiting.
• According to the first of these illustrative embodiments of the invention, the two half-implants represented inFIG. 1, namely a male half-implant1aand a female half-implant1b,each include aninterbody cage2 intended to enclose a bone graft or bone graft material. Eachcage2 comprises afirst part3 intended to be oriented in the posterior-anterior direction of the spine, and asecond part4 oriented substantially perpendicular to thefirst part3, and being connected to thefirst part3 via atransition portion5. In one embodiment, the walls of thecage2 at thetransition portion5 have a curvilinear shape, that is to say without sharp corners which could damage the surrounding organs during and after fitting of the half-implants1a,1b.In the illustrated embodiment, thecage2 has a set offirst holes6,7 which pass right through it between itsupper surface202 and itslower surface204, and a set ofsecond holes8,9 which pass right through thecage2 between itsside surfaces206 and208. Theseholes6,7,8,9 make it possible to insert bone graft material into thecage2, prior to the half-implants1a,1bbeing fitted. Once implanted, the bone graft material in thecage2 will come into contact with the vertebral plates and the remaining part of the disc. Upon hone ingrowth into thecage2, the bone graft material aids in fusing the vertebrae together. Front face or tool engagement face10 of thefirst part3 of each half-implant1a,1bhas ahole11 that allows the half-implant1a,1bto be connected to an implantation tool, such as the ones which will be described below with reference toFIGS. 5 and 6. Theholes11 in one form are threaded so as to engage with screws on the implantation tool. As depicted in the illustrated embodiment, eachhole11 has a pair ofalignment notches209 formed on opposite sides of thehole11, which are used to orient the half-implants1a,1bwith the implantation tool.
• As shown, the two half-implants1a,1bin the first illustrated embodiment havesecond parts4 with different front or connection faces12,17. The connection face12 of thesecond part4 of the male half-implant1aincludes aprotrusion13. Theprotrusion13 comprises successively, starting from connection face12:
• • a first substantiallycylindrical portion14 having a given diameter “D1”;
  • a second substantiallycylindrical portion15 having a diameter “D2” that is greater than “D1”;
  • and a substantiallyfrustoconical portion16 whose initial diameter is equal to “D2” and decreases as the distance from connection face12 increases.
• The connection face17 of thesecond part4 of the female half-implant1bincludes a socket orreceiver18 for theprotrusion13 of the male half-implant1a.Thesocket18 is delimited externally by a series ofelastic tongues19. Each of thetongues19 ends in abulge20 having abeveled part21 which cooperates with thefrustoconical portion16 upon engagement of theprotrusion13 in thesocket18, in such a way as to spread thetongues19 apart. Thetongues19 return to their initial position after complete engagement of theprotrusion13 in thesocket18. Thebulges20 then cooperate with theconnection face12 of the male half-implant1band thecylindrical portions14,15 of theprotrusion13 so as to maintain engagement between theprotrusion13 and thesocket18. The two half-implants1a,1bare thus connected to form the functional equivalent of a single implant, such as is represented inFIG. 2, and they can only be disconnected by a deliberate action exerted upon their means of connection.
• In the example shown, thehalf implants1a,1b,once connected together, have a horseshoe or U-shape. The height of eachhalf implant1a,1btapers or decreases progressively fromsecond part4 to thefirst part3. In one embodiment, eachhalf implant1a,1btapers in a manners that generally matches the lordotic angle of the vertebrae. It is contemplated, however, that in other embodiments the upper202 and lower204 surfaces of thefirst part3 can extend generally in a parallel relationship and/or can be substantially cylindrical in shape. Thesecond parts4 of thehalf implants1a,1btoo can have various shapes, and the one shown inFIGS. 1 and 2 are only examples.
• According to a second illustrated embodiment of the invention, two half-implants22a,22brepresented inFIG. 3 are similar, in their general design, to those of the first embodiment shown inFIGS. 1 and 2. It should be noted that their common elements have been designated by the same reference numbers. As shown inFIG. 3A, the male half-implant22aincludes, onconnection face12 of itssecond part4, aprotrusion23 which this time has an external shape that is generally cylindrical and, as is shown, defines a centrally located recess orcavity210. In one form, bone graft material can be packed intocavity210 in order to promote fusion. The cylindrical-shapedprotrusion23 has a cross section whose circumference extends over an angle that is at least greater than 180° so as to define two receiving seats orgrooves24,25 proximal theconnection face12.
• The female half-implant22bincludes, on theconnection face17 of itssecond part4, twoelastic tabs26,27 which between them define aninternal space28 forming a receiver or socket for accommodating theprotrusion23 of the male half-implant22aand for holding it there. In one form,notches29,30 are defined in thetabs26,27 proximal theconnection face17 of the female-half implant22b,which facilitate the spreading of thetabs26,27 when theprotrusion23 comes into contact with them. Ends31,32 of thetabs26,27 are shaped in such a way as to be inserted in the receivingseats24,25 of the zones of connection of theprotrusion23 with theconnection face12 of the male half-implant22awhen theprotrusion23 is entirely engaged in theinternal space28 defined by thetabs26,27. In this way theprotrusion23 is firmly held in thisinternal space28 and can be dislodged therefrom only by a deliberate action exerted upon the half-implants22a,22b.FIG. 4 shows the two half-implants22a,22bin the assembled position forming the functional equivalent of a single implant. As should be appreciated, the half-implants22a,22billustrated inFIG. 4 allow for greater tolerance with respect to possible discrepancies in height between the two half-implants22a,22bwhen they are connected. A slight discrepancy in height between the two half-implants22a,22bdoes not compromise their connection or the maintenance of their connection.
• Techniques and instrumentation for implanting the half-implants1a,1b,22aand22bwill be described below with reference toFIGS. 5 and 6. Although the technique and instrumentation for inserting the half-implants1a,1b,22aand22bwill be described below with reference to half-implants1aand2b,it should be understood that the below described techniques and instrumentation can be used with half-implants22aand22bas well as other types of half-implants. Before the half-implants1a,1bare inserted, the disc space is prepared in the manner as described above. The insertion of the of the half-implants1a,1bis then performed by attaching the half-implants1a,1bto the end of rods that are inserted in theholes11 of the front faces10 of theirfirst parts3, and by connecting the half-implants1a,1btogether by manipulation of these rods. The ends of thesecond parts4 of the half-implants1a,1bare then moved towards one another in order to connect them to one another in situ.Instrument33 and33′ (implantation tool) allow for the connection of the half-implants1a,1bin such a manner. Theinstrument33,33′ allows the half-implants1a,1bto be moved towards each other in a gradual and controlled manner while constantly keeping them in a parallel orientation. This improves the chance that the insertion of theprotrusion13,23 of themale element1a,22ain the corresponding receivingseat18,28 of thefemale element1b,22bis effected under optimum conditions.
• FIG. 5 illustrates one embodiment for theinstrumentation33 that is used to implant the half-implants1a,1b,andFIG. 6 illustratesinstrumentation33′ according to another embodiment. It should be noted thatinstrumentation33 and33′ share a number of common features. For the sake of brevity and clarity,instrumentation33 and33′ will be discussed together below with particular reference toinstrumentation33. Althoughinstrumentation33 will be referenced below, it should be understood that the same description forinstrumentation33 applies as well as toinstrumentation33, with any notable distinctions between the two embodiments being highlighted. With reference to the embodiment illustrated inFIG. 5, theinstrumentation33 includes tworods34,35 composed of several parts that are connected together by systems which, for example, can include slots or holes and fixed or detachable indexing pins. In theFIG. 5 embodiment, the parts of therods34,35 are connected together with detachable indexing pins36,37. It is contemplated, however, that therods34,35 can each be made from a single part. For example, in the embodiment illustrated inFIG. 6, theinstrumentation33′ includes tworods34′,35′, each having a unitary construction.
• Therods34,35 are intended to support the half-implants1a,1b,when thehalf implants1a,1bare connected together. However, therods34,35 can also be used alone and independently by the surgeon for manipulating the half-implants1a,1bduring insertion of the half-implants1a,1bin the receiving cavities (or scats) hollowed out in the degenerated disc. To fix the half-implants1a,1bin the illustrated embodiment, therods34,35 each have abent end part38,39 that defines anorifice40,41 in which ascrew42,43 is received. In the embodiment illustrated inFIG. 5, thesebent parts38,39 have a skewed shape in which thebent parts38,39 bend away from a plane defined by therods34,35. By skewingbent parts38 and39 in such a manner, the area around theorifices40,41 is freed so that thescrews42,43 can be easily accessed. However, it should be appreciated that thebent parts38,39 can have a planar arrangement. For instance, in the embodiment illustrated inFIG. 6,bent parts38′ and39′ are oriented in the same plane as the rest of therods34′,35′. At the extremity of theend part38,39, eachrod34,35 hastabs44,45,46,47 intended to be inserted in receiving seats oralignment notches209 formed on the sides of theholes11 provided on the front faces10 of the half-implants1a,1b,or in separate receiving seats specially designed for this purpose. Thesetabs44,45,46,47 make it possible to fix the half-implants1a,1bon therods34,35 in defined orientations. Thescrews42,43, cooperating with the threads formed on the surfaces delimiting theholes11 in the half-implants1a,1b,permit this fixation. Thebent portions38,39 of therods34,35 permit access toheads212 of thescrews42,43 so that these can be tightened and loosened. It goes without saying that the device for fixing the half-implants1a,1bwhich has just been described is but one example and that the skilled person can imagine other examples which would satisfy the same functions.
• After the half-implants1a,1bhave been secured to therods34,35, therods34,35 are introduced into apositioning device214 that allows them to be held in a position in which therods34,35 are oriented parallel with respect to one another. Thepositioning device214 also makes it possible to regulate the spacing of therods34,35 from each other so that the surgeon can bring the half-implants1a,1btowards each other and connect the half-implants1a,1b,after the half-implants1a,1bhave been fitted in the receiving cavities hollowed out in the disc. In the example shown inFIGS. 5 and 6, thepositioning device214 in the first instance includes twotubes48,49 in which therods34,35 are inserted. Therods34,35 are secured in thetubes48,49 by stop members orbearings50,51 (or any other functionally equivalent device) formed on therods34,35 on which thetubes48,49 come into abutment, and by internally threadedrings52,53 which, by cooperating withcorresponding threads216 formed on the ends of therods34,35, press thestop members50,51 against thetubes48,49.
• Thetubes48,49 are connected to one another by means of an articulateddevice218. The articulateddevice218 in the first instance includes twotransverse rods54,55, which are pivotally coupled to one another to permit their rotation about acommon hinge pin56, which extends perpendicular to the plane that includes thetubes48,49. The firsttransverse rod54 is pivotally coupled to the distal or front end of the first tube48 (that is to say the end nearest the half-implant1a) about ahinge pin57 that extends parallel to thecommon hinge pin56 of thetransverse rods54,55.Hinge pin57 is held in a receivingseat58 which is fixed to thefirst tube48 and which prohibits any movement thereof in translation relative to thefirst tube48. The pivoting of the firsttransverse rod54 about thehinge pin57 is ensured by astirrup59. As shown, thestirrup54 of the firsttransverse rod54 extends around opposite sides oftube48. The firsttransverse rod54 is also coupled to the proximal or rear end of the second tube49 (that is to say the end farthest from the half-implant1b) about a hinge pin60. Aknurled wheel61 is threadedly coupled to hinge pin60. Hinge pin60 extends in parallel relationship with respect to thecommon hinge pin56 of thetransverse rods54,55. Hinge pin60 is coupled with the firsttransverse rod54 by astirrup62, which can pivot about hinge pin60. Hinge pin60 is able translationally move in a receiving seat or slot63 that extends along thesecond tube49. The secondtransverse rod55 is similarly pivotally coupled to the front end of thesecond tube49 about ahinge pin64.Hinge pin64 is held in a receivingseat65 fixed to thesecond tube49. As shown,rod55 has astirrup66 that is received aroundtube49, and thestirrup66 is coupled to hingepin64. The secondtransverse rod55 is also pivotally coupled to the rear end of thefirst tube48 with ahinge pin67. Aknurled wheel68 is threadedly coupled to thehinge pin67.Hinge pin67 is coupled to the secondtransverse rod55 by astirrup69, which can pivot abouthinge pin67.Hinge pin67 is able to translationally move in a receiving seat or slot70 that extends along thefirst tube48. The use ofknurled wheels61,68 and the threaded hinge pins60,67 cooperating with corresponding threads formed in thestirrups62,69 ensures simple assembly and disassembly of thedevice214.
• Device214 includes areceiver71 that rotates about ahinge pin72 that extends parallel to the other axes of rotation for hinge pins56,57,60,64 and67, which were mentioned above.Hinge pin72 passes through the secondtransverse rod55 in proximity to thefirst tube48. One end of an externally threadedrod73 is inserted and fixed inreceiver71. The other end of the threadedrod73 is inserted in the internal space of atube74 equipped with a thread corresponding to the thread of therod73.Tube74 is equipped with aknurled wheel75 that allows the surgeon to turn it and thereby regulate the position of therod73 relative to thetube74. As shown, a receivingseat76 is rotatably coupled ahinge pin77 that passes through the firsttransverse rod54 in proximity to thesecond tube49. Receivingseat76 is able to rotate about an axis that is extends parallel to the axes of rotation of hinge pins56,57,60,54,67 and72, which were mentioned above. The threadedrod73 passes through receivingseat76.
• After thewhole instrument214 has been assembled, the surgeon is able to move the tworods34,35 supporting the half-implants1a,1btowards or away from each other by turning theknurled wheel75 in such a way as to regulate the penetration depth of therod73 in thetube74, which determines the spacing of therods34,35. Also, the ability of thetransverse rods54,55 to rotate about the various hinge pins56,57,60,64,67,72,77, and the ability of translational movement of hinge pins60 and67 in receivingslots63 and70, mean that this movement of therods34,35 towards or away from each other is effected while ensuring permanent parallel positioning of therods34,35. The half-implants1a,1bcan therefore be moved towards each other in the direction most favourable to their proper connection.
• Aspring78 is provided about the threadedrod73 and bears onreceiver71 and receivingseat76. Thespring78 makes it possible to increase the rigidity of the assembled instrument because thespring78 tends to space therods34,35 apart from one another in order to reduce the play which may exist between the different components controlling the spacing of therods34,35. Reduction of this play can make use of theinstrument214 easier.
• One should appreciate that variations can be made to the design of thepositioning device214 for controlling the movement of the tworods34,35. For example, it would be conceivable to move therods34,35 together using an elastic device which can be controlled by a clamp or by simple manual pressure. The threaded-tube and threaded-rod device which has been described has the advantage of allowing easily controlled progressive clamping of therods34,35, and permanent holding of a selected relative position of therods34,35, permitting, if necessary, the half-implants1a,1bto move towards each other in several stages without requiring the surgeon to manually holds therods34,35 in order to keep the spacing of therods34,35 constant.
• Once the half-implants1a,1bhave been connected to one another, therings52,53 are removed so as to allow disconnection of therods34,35 from the rest of thepositioning device214. Thescrews42,43 are then loosened so as to disconnect therods34,35 from the half-implants1a,1bwhose implantation is then complete.
• According to another variation of the present invention, the interbody implant no longer comprises two parts, but three parts, namely a central part and two lateral parts which are fixed together more or less rigidly depending on the wishes of the user. An illustrative embodiment of this variation is shown inFIGS. 8A and 8B. Inimplant assembly224, acentral part106 of theimplant224 is in the form of a cage, which hasapertures107 through its upper and lower faces andapertures108 through its lateral faces, in such a way as to permit a bone graft material to be inserted into thecentral part106 prior to its fitting. Thecentral part106 has a general shape that is slightly arched in order to match the shape of the receiving cavity that has been formed in the disc. The ends of thecentral part106 include end faces109,110 oriented obliquely in relation to the general direction of thecentral part106, so as to be easily accessible from the outside when thecentral part106 is in place in its receiving cavity. Theimplant224 also includes twolateral parts111,112 in the form of cages, which haveapertures113,114,115 and116 for receiving bone graft material. Thelateral parts111,112 are connected to thecentral part106 by way ofscrews117,118, which can be inserted into tappedholes119 formed in the end faces109,110 of thecentral part106, and the heads of which engage bearingsurfaces120 formed on thelateral parts111,112. This assembling ofimplant224 by means ofscrews117,118 gives it great rigidity.
• To fitimplant224 in place, the following described techniques can be used. Thecentral part106 is fixed with the aid of a screw121 (which, as is shown, can be identical to one of thescrews117,118 which will be used for assembling the implant224) to the end of arod122 which is designed, for example, in a manner similar to one of therods34,35 of the instrument set shown inFIGS. 5 and 6, as can be seen fromFIG. 9. The surgeon then introduces thecentral part106 into the receiving cavity that was formed beforehand in the damaged disc. Of course, it should be appreciated that other means of fixing other than thescrew121 are conceivable.
• In the following stage, the surgeon uses atool123, shown inFIG. 10, which is made up of two main parts:
• • asheath124 provided at one of its ends with means permitting one of thelateral parts111,112 of the implant to be maintained there, for example comprising two studs ortabs125 which cooperate with twocorresponding notches126,127 formed on theanterior face128 of each of thelateral parts111,112; and
  • ascrewdriver129 extending inside and through thesheath124; one of its ends is provided with an impression orhead130 which can engage with thescrew117, and the other end is provided with agrip handle131 that allows the surgeon to turn thescrewdriver129.
• In the example shown, atube132 is positioned inside thesheath124 such that there is only a slight clearance between thetube132 and thesheath124 so that thetube132 is able to move inside thesheath124. As depicted inFIG. 10, thetube132 in thesheath124 has externally threadedend226, and thetube132 can be rotated through aknurled wheel132′, which is attached to thetube132. When rotated, the threadedend226 of thetube132 is used to engage with a corresponding threading formed in abore137 of theanterior face128 of alateral part111,112 of theimplant224. One could of course conceive of other means for maintaining thelateral part111,112 of theimplant224 connected to thesheath124. As shown, thescrewdriver129 is slidably received insidetube132 such that thescrewdriver129 is able to rotate insidetube132 and tightenscrew117.
• Referring toFIG. 11,lateral part111 of theimplant224 is secured to the threadedend226 of thetube132 intool123, and thescrew117 is placed at the end of thescrewdriver129 of thetool123.Lateral part111 of theimplant224 is then inserted into the receiving cavity formed in the disc in order to move it to thecentral part106, which is still fixed to therod122.Lateral part111 is positioned to bring thescrew117 in alignment with the tappedhole119 formed in theface109 of thecentral part106. To facilitate this positioning, in one embodiment, a calibratedcrosspiece133 is used to maintain therod122 and thetool123 in a suitable angular orientation. Thecrosspiece133 also makes it possible to obtain a precise placement of thecentral part106 of the implant in its receiving cavity. When the desired positioning is obtained, the surgeon turns thescrewdriver129 in order to tighten thescrew117 so as to secure thecentral part106 and thelateral part111.FIG. 11 illustrates the configuration of theimplant assembly224 at the end of this stage (the disc and its surrounding area have not been shown for the sake of clarity).
• After thelateral part117 is attached to thecentral part106, therod122 is then disconnected from thecentral part106 of theimplant224 by loosening thescrew121. The otherlateral part112 of theimplant224 is attached at the threadedend226 of atool123′, which is identical to theprevious tool123.Screw118 is placed at the end of thescrewdriver129′ in thetool123′. Withtool123′,lateral part112 is moved to engage theend face110 of thecentral part106 that was disengaged fromrod122. The otherlateral part112 is then secured to thecentral part106 withscrew118 in the same manner as described above. In one embodiment, acrosspiece134 is used to maintain the angular positioning of the twotools123,123′.FIG. 12 shows theassembly224 at the end of this stage. Once the otherlateral part112 has been fixed, the twotools123,123′ are withdrawn by rotation of theknurled wheels132′ making it possible to detach thetubes132 from thebores137 of the anterior faces128 of thelateral parts111,112.
• When the twotools123,123′ are removed, the insertion of theimplant224 is thus completed. In one embodiment, to make it easier to align thescrews117,118 with the tappedholes119 of thecentral part106, a metal wire is passed through a central aperture135 (FIG. 8B) in thescrew121 that connectsrod122 to theend face109 of thecentral part106. The wire is further passed through the tappedhole119 of the other end face110 of thecentral part106. Thescrews117,118 and thescrewdrivers129,129′ are themselves provided withcentral apertures135,136,136′ in which the wire can be passed through. With the wire passing through thescrews117,118 and thescrewdrivers129,129′, the end of the portion of the wire extends from tappedhole119 so that thescrews117,118 are correctly guided towards the tapped holes119. After therod122 has been withdrawn, the other end of the wire emerging from thecentral part106 becomes accessible, and thescrew118 carried by thescrewdriver129′ of thetool123′ can be engaged on this end of the wire. After theimplant224 has been fitted, the wire is removed.
• The above-described embodiment in which the implant includes three parts has at least the following advantages:
• • at each operation, only a component of relatively small dimensions is inserted into the body of the patient; this entails a less invasive approach; it is no longer necessary to remove as many stabilizing elements like the articular facets of the vertebrae, and it is possible to dispense with sectioning the muscles, and instead they need only be moved aside: recovery is therefore quicker; and
  • the connection operations take place closer to the openings of the cavity formed in the disc, thus in a zone which is visible to the surgeon, making it easier to fit the implant; moreover, this permits a connection by screws, thus one which is rigid, reliable and relatively easy to effect.
• The connection means which have been described and shown for this illustrative embodiment of the invention are not exclusive, and the person skilled in the art will be able to adopt other connection means analogous, for example, to those described for the previously described implant variants made up of two parts. The degree of rigidity sought for the assembled implant will be a criterion in choosing the method of connecting the different parts. The person skilled in the art will be readily able to adapt the configurations of the different parts of the implant to this effect, and of the tools used to fit them, by drawing inspiration from what has been set out in this description.
• When the implants (1a,1b), (22a,22b), (106,111,112) are being put in place, it is possible for the surgeon to usespacer tool78, which aids in introducing the parts of the implants (1a,1b), (22a,22b), (106,111,112) into their respective receiving cavities.Tool78 maintains the space between the vertebrae concerned, while at the same time protects the surrounding area, in particular the spinal nerves, which is very important in the posterior lumbar region where the implants (1a,1b), (22a,22b), (106,111,112), according to one embodiment, are intended to be implanted.
• Thistool78 is made up of three parts. The first part is aprotector guide79 of which oneend80 is intended to be positioned at the inlet of one of the receiving cavities formed in the vertebrae for the half-implants (1a,1b), (22a,22b), (106,111,112) during their introduction. The rest oftool78 is designed to protect the surrounding area of the work zone and to permit easy manipulation by the surgeon, for example, as is shown, in the form of a straight part finishing in abent part82 set outwards from the operating site. As shown inFIG. 7B, end80 oftool78 has a width “1” largely equivalent to the height of the receiving cavities formed in the disc for fitting of the implants (1a,1b), (22a,22b), (106,111,112). It is equipped withstops81,82 that are configured to bear against the outer surfaces of the vertebrae upon introduction of the instrument into the receiving cavity, so as to limit its penetration to the necessary length.End80 of theprotector guide79 is also equipped on its sides with twoprotrusions83,84 that have a generally triangular shape and are equipped withposterior notches85,86 whose function will be explained below.
• The second part oftool78 is adistractor element87, which is configured to support theend80 of theprotector guide79 upon its insertion into the receiving cavity formed in the vertebrae for the implant (1a,1b), (22a,22b), (106,111,112). Thedistractor element87 is tapered at itsfront end88 to facilitate its introduction into the receiving cavity formed in the vertebrae. Thedistractor element87 is placed at the end of arod89 which has, on its cylindrical lateral wall, anorifice90 whose function will be explained below. Engagement seats are formed in theupper face91 andlower face220 of thedistractor element87 for theprotrusions83,84 of theprotector guide79. These engagement seats are each delimited on the one hand by astud92 which is received in one of theposterior notches85,86 in theprotrusions83,84 of the and on the other hand by a hollowed-out portion93 which receives thefree corner94,95 of one of theprotrusions83,84 by blocking its movements towards the front of thedistractor element87. Thedistractor element87 also has, on its rear face, twonotches96 whose function will be explained below.
• The third part oftool78 is atubular element97, with rectangular cross-section in the example shown, and provided with a receivingcavity98 permitting insertion of therod89 of the second part of thetool78. One of thelateral surfaces222 of thetubular element97 has a tappedhole99 in which a threadedelement100 with aknurled wheel101 is threaded.End102 of the threaded element is configured to penetrate into theorifice90 of therod89 of thedistractor element87 whentool78 is assembled. The position of the tappedhole99 is determined accordingly.Anterior face103 of thetubular element97 hasstuds104,105 that are configured to be inserted in thenotches94 of the posterior face of thedistractor element87. Thestuds104,105 and thenotches94 make it possible to regulate the relative positions of thedistractor element87 and thetubular element97 in such a way that orifice90 in thedistractor element87 and the tappedhole99 in thetubular element97 are automatically aligned with one another upon assembly of thetool78. It would of course be possible to provide just onestud102,103 and asingle notch94 or any other means of establishing suitable relative positions of thedistractor element87 and thetubular element97 when assembling thetool78.
• Tool78 is assembled as follows. In a first stage, theprotector guide79 and thedistractor element87 are placed one on top of the other, with thetriangular protrusions83,84 of theprotector guide79 inserted in the corresponding receiving seats of thedistractor element87. In a second stage, therod89 of thedistractor element87 is inserted in the receivingcavity98 of thetubular element97 and secured inside the receivingcavity98 with the threadedelement100, which is made to penetrate intoorifice90. Thetriangular protrusions83,84 are thus secured in their respective receiving seats on thedistractor element87 by theanterior face103 of thetubular element97, and the whole tool is thus stabilized, with theprotector guide79 held along thetubular element97. Thedistractor element87 and theend80 of theprotector guide79 are then inserted in a receiving cavity previously hollowed out in the degenerated disc, in such a way as to establish the exact interdiscal distance necessary for introducing the corresponding implant (1a,1b), (22a,22b), (106,11),112), which distance is substantially equal to “1”, and to complete the preparation of the receiving seat surfaces. The threadedelement100 is then loosened, which allows the third part of the tool to be withdrawn, then the second part, so that only theend80 of theprotector guide79 is left remaining in the receiving cavity. A part of implant (1a,1b), (22a,22b), (106,111,112) is then inserted in the receiving cavity. With theend80, it is possible to maintain the desired interdiscal space during this introduction, while the rest of theprotector guide79, which extends outside the receiving cavity for the implant (1a,1b), (22a,22b), (106,111,112), makes it possible to move aside and protect the organs of the patient which are situated on the path of insertion of the implant (1a,1b), (22a,22b), (106,111,112).
• It goes without saying that detailed modifications can be made to the various parts of the tool78 (in particular as regards the means of joining its various parts), provided that the essential functions of its various elements are retained. This tool can also be used to assist in placing interbody implants having a configuration different than that of the implants (1a,1b), (22a,22b), (106,111,112) described herein.
• While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes, modifications, and equivalents that come within the spirit of the inventions described herein and/or defined by the following claims are desired to he protected.

Claims (21)

1.-25. (canceled)

26. An interbody implant for implantation between adjacent vertebrae, comprising:

a first interbody cage having a protrusion extending therefrom;

a second interbody cage defining a socket; and

wherein said first and second interbody cages each define a substantially open hollow interior and include upper and lower vertebral engaging surfaces that each define an opening in communication with said hollow interior to facilitate fusion with the adjacent vertebrae; and

wherein said protrusion extending from said first interbody cage is engaged in said socket defined by said second interbody cage to interconnect said first and second interbody cages.

27. The interbody implant ofclaim 26, wherein the interbody implant comprises two lateral portions and a central portion extending transversely between said lateral portions.

28. The interbody implant ofclaim 27, wherein said lateral portions and said central portion cooperate with one another to provide the interbody implant with a horseshoe-shaped or U-shaped implant configuration.

29. The interbody implant ofclaim 27, wherein said lateral portions each have a generally linear configuration and extend substantially parallel to one another in an anterior-posterior direction.

30. The interbody implant ofclaim 27, wherein said central portion has a generally semi-circular configuration extending between said lateral portions.

31. The interbody implant ofclaim 26, further comprising bone graft material positioned within said hollow interior of said first and second interbody cages to further facilitate fusion with the adjacent vertebrae.

32. The interbody implant ofclaim 26, wherein each of said first and second interbody cages includes opposite side surfaces each defining an opening passing therethrough in communication with said hollow interior.

33. The interbody implant ofclaim 26, wherein each of said first and second interbody cages includes a lateral portion oriented in a posterior-anterior direction and an arc-shaped portion extending along approximately one-quarter of a circle, said arc-shaped portion of said first interbody cage connected to said arc-shaped portion of said second interbody cage by engagement of said protrusion in said socket.

34. The interbody implant ofclaim 33, wherein said first and second interbody cages are interconnected to define a U-shaped implant configuration.

35. The interbody implant ofclaim 26, wherein each of said first and second interbody cages includes one of said lateral portions of said implant assembly and also includes an arc-shaped portion extending along approximately one-quarter of a circle, said arc-shaped portions of said first and second interbody cages interconnected to one another by engagement of said protrusion in said socket.

36. The interbody implant ofclaim 26, further comprising a third interbody cage defining a substantially open hollow interior and upper and lower vertebral engaging surfaces that each define an opening in communication with said hollow interior to facilitate fusion with the adjacent vertebrae; and

wherein said third interbody cage includes one of said protrusion and said socket engaged with a corresponding one of said protrusion and said socket defined by an adjacent one of said first and second interbody cages.

37. The interbody implant ofclaim 36, wherein said first, second and third interbody cages are interconnected with one another to define a U-shaped implant configuration.

38. The interbody implant ofclaim 36, wherein said protrusion comprises a threaded shank portion of a screw; and

wherein said socket comprises an internally threaded aperture configured for threading engagement with said threaded shank portion of said screw.

39. The interbody implant ofclaim 26, wherein said socket is defined by a plurality of elastic members that flex apart to receive said protrusion within said socket and which flexibly return toward an initial position to retain said protrusion within said socket.

40. The interbody implant ofclaim 39, wherein said plurality of elastic members cooperate with one another to provide said socket with a cylindrical configuration.

41. The interbody implant ofclaim 26, wherein said protrusion and said socket each have a generally cylindrical configuration.

42. The interbody implant ofclaim 26, wherein said protrusion comprises a threaded shank portion of a screw; and

wherein said socket comprises an internally threaded aperture configured for threading engagement with said threaded shank portion of said screw.

43. The interbody implant ofclaim 26, wherein said first and second interbody cages each have a height between said upper and lower surfaces that progressively tapers to generally match a lordotic angle between the adjacent vertebrae.

44. The interbody implant ofclaim 26, wherein each of said first and second interbody cages includes a front face defining a hole for connection with an implantation tool.

45. The interbody implant ofclaim 26, wherein said protrusion engaged in said socket comprises means for in situ connection of said first and second interbody cages within an intervertebral space between the adjacent vertebrae.

Images