Abstract:
A method of implanting an intervertebral prosthesis in a disc located between a pair of adjacent vertebrae of a patient. Damaged or diseased nucleus pulpous is removed from the disc using minimally invasive techniques. The adjacent vertebrae are positioned in a lordotic condition. A mold adapted to contain a biomaterial is positioned between the adjacent vertebrae. A flowable biomaterial is delivered into the mold using minimally invasive techniques so that the adjacent vertebrae are in the lordotic condition. The flowable biomaterial is allowed to at least partially cure so that the adjacent vertebrae are in a lordotic-neutral position. The step of positioning the pair of adjacent vertebrae in a lordotic condition may include positioning the patient in extension, displacing spinous processes of the adjacent vertebrae to a compressed configuration, suturing spinous processes of the adjacent vertebrae to a compressed configuration, and/or delivering the flowable biomaterial into the mold at sufficient pressure to distraction the adjacent vertebrae to a lordotic position. One or more preformed prostheses can be substituted for, or combined with, the mold.

Description:
[0001]     The present application claims the benefit of U.S. Provisional Application Ser. No. 60/708,244 entitled Multi-Lumen Mold For Intervertebral Prosthesis And Method Of Using Same filed on Aug. 15, 2005; U.S. Provisional Application Ser. No. 60/677,273 entitled Catheter Holder for Spinal Implants filed May 3, 2005; and U.S. Provisional Application Ser. No. 60/708,245 entitled Catheter Holder for Spinal Implants filed Aug. 15, 2005, all of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a method and apparatus for filling an intervertebral disc space with an in situ curable biomaterial to position a pair of adjacent vertebrae in a lordotic condition.  
       BACKGROUND OF THE INVENTION  
       [0003]     The intervertebral discs, which are located between adjacent vertebrae in the spine, provide structural support for the spine as well as the distribution of forces exerted on the spinal column. An intervertebral disc consists of three major components: cartilage endplates, nucleus pulposus, and annulus fibrosus. The central portion, the nucleus pulposus or nucleus, is relatively soft and gelatinous; being composed of about 70 to 90% water. The nucleus pulposus has a high proteoglycan content and contains a significant amount of Type II collagen and chondrocytes. Surrounding the nucleus is the annulus fibrosus, which has a more rigid consistency and contains an organized fibrous network of approximately 40% Type I collagen, 60% Type II collagen, and fibroblasts. The annular portion serves to provide peripheral mechanical support to the disc, afford torsion resistance, and contain the softer nucleus while resisting its hydrostatic pressure.  
         [0004]     Intervertebral discs, however, are susceptible to disease and a number of injuries. Disc herniation occurs when the nucleus begins to extrude through an opening in the annulus, often to the extent that the herniated material impinges on nerve roots in the spine or spinal cord. The posterior and posterolateral portions of the annulus are most susceptible to attenuation or herniation, and therefore, are more vulnerable to hydrostatic pressures exerted by vertical compressive forces on the intervertebral disc. Various injuries and deterioration of the intervertebral disc and annulus fibrosus are discussed by Osti et al., Annular Tears and Disc Degeneration in the Lumbar Spine,  J. Bone and Joint Surgery,  74-B(5), (1982) pp. 678-682; Osti et al., Annulus Tears and Intervertebral Disc Degeneration,  Spine,  15(8) (1990) pp. 762-767; Kamblin et al., Development of Degenerative Spondylosis of the Lumbar Spine after Partial Discectomy,  Spine,  20(5) (1995) pp. 599-607.  
         [0005]     Many treatments for intervertebral disc injury have involved the use of nuclear prostheses or disc spacers. A variety of prosthetic nuclear implants are known in the art. For example, U.S. Pat. No. 5,047,055 (Bao et al.) teaches a swellable hydrogel prosthetic nucleus. Other devices known in the art, such as intervertebral spacers, use wedges between vertebrae to reduce the pressure exerted on the disc by the spine. Intervertebral disc implants for spinal fusion are known in the art as well, such as disclosed in U.S. Pat. No. 5,425,772 (Brantigan) and U.S. Pat. No. 4,834,757 (Brantigan).  
         [0006]     Further approaches are directed toward fusion of the adjacent vertebrate, e.g., using a cage in the manner provided by Sulzer. Sulzer&#39;s BAK® Interbody Fusion System involves the use of hollow, threaded cylinders that are implanted between two or more vertebrae. The implants are packed with bone graft to facilitate the growth of vertebral bone. Fusion is achieved when adjoining vertebrae grow together through and around the implants, resulting in stabilization.  
         [0007]     Prosthetic implants formed of biomaterials that can be delivered and cured in situ, using minimally invasive techniques to form a prosthetic nucleus within an intervertebral disc have been described in U.S. Pat. No. 5,556,429 (Felt) and U.S. Pat. No. 5,888,220 (Felt et al.), and U.S. Patent Publication No. US 2003/0195628 (Felt et al.), the disclosures of which are incorporated herein by reference. The disclosed method includes, for instance, the steps of inserting a collapsed mold apparatus (which in a preferred embodiment is described as a “mold”) through an opening within the annulus, and filling the mold to the point that the mold material expands with a flowable biomaterial that is adapted to cure in situ and provide a permanent disc replacement. Related methods are disclosed in U.S. Pat. No. 6,224,630 (Bao et al.), entitled “Implantable Tissue Repair Device” and U.S. Pat. No. 6,079,868 (Rydell), entitled “Static Mixer”, the disclosures of which are incorporated herein by reference. See also, for instance, French Patent Appl. No. FR 2 639 823 (Garcia) and U.S. Pat. No. 6,187,048 (Milner et al.). Both references differ in several significant respects from each other and from the apparatus and method described below.  
         [0008]     Nucleoplasty or partial disc replacement performed from posterior entry points have a high rate of dislocation, often due to the fact that the posterior wall of the annulus is thinner than the other walls, and may be diseased or damaged. While anterior entry points are often appropriate for many patients, the posterior approach is the most desirable for a large segment of the patient population.  
         [0009]     As illustrated in  FIGS. 1 and 2 , dislocation of intervertebral disc prostheses  20  can occur due to expulsion forces  22 ,  24  generated during flexion or rotation of the adjacent vertebrae  28 ,  30 . The expulsion forces  22 ,  24  are created by opposing end plates  42 ,  44  of the adjacent vertebrae  28 ,  30  acting on the prosthesis  20  at angle  26 . The greater the angle  26 , the greater the expulsion forces  22 ,  24 .  
         [0010]     The posterior wall  32  of the annulus  34  is typically thinner than the other walls, and may include damaged or diseased portions  46 . Damage to the posterior wall  32  can be aggravated during the surgical removal of the nucleus pulposus  36 . For example, each annulotomy  40  through the annulus  34  further weakens the posterior wall  32 , unless the annulotomy is positioned through a herniation site. Also, in situations where the size of the prosthesis  20  is small relative to the size of the annulotomy  40 , the prosthesis  20  can extrude posteriorly  38  from the annulus  34 . If dislocation occurs, the prosthesis  20  and/or portions of the annulus  34  can impinge on the spinal cord or nerve root, causing pain and other complications.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The present invention relates to a method and apparatus for positioning a pair of adjacent vertebrae in a lordotic condition. The lordotic condition is primarily anterior distraction of a pair of adjacent vertebrae that does not cause symptomatic impingement of the spinal cord by the posterior portion of the intervertebral disc. In the preferred embodiment, the method includes delivering an in situ curable biomaterial to the intervertebral disc space.  
         [0012]     The present method and apparatus can be used, for example, to implant a prosthetic total disc, or a prosthetic disc nucleus, using minimally invasive techniques that leave the surrounding disc tissue substantially intact. The phrase intervertebral disc prosthesis is used generically to refer to both of these variations.  
         [0013]     Minimally invasive refers to a surgical mechanism, such as microsurgical, percutaneous, or endoscopic or arthroscopic surgical mechanism, that can be accomplished with minimal disruption of the pertinent musculature, for instance, without the need for open access to the tissue injury site or through minimal incisions (e.g., incisions of less than about 4 cm and preferably less than about 2 cm). Such surgical mechanism are typically accomplished by the use of visualization such as fiber optic or microscopic visualization, and provide a post-operative recovery time that is substantially less than the recovery time that accompanies the corresponding open surgical approach.  
         [0014]     Mold generally refers to the portion or portions of the present invention used to receive, constrain, shape and/or retain a flowable biomaterial in the course of delivering and curing the biomaterial in situ. A mold may include or rely upon natural tissues (such as the annular shell of an intervertebral disc) for at least a portion of its structure, conformation or function. The mold, in turn, is responsible, at least in part, for determining the position and final dimensions of the cured prosthetic implant. As such, its dimensions and other physical characteristics can be predetermined to provide an optimal combination of such properties as the ability to be delivered to a site using minimally invasive means, filled with biomaterial, prevent moisture contact, and optionally, then remain in place as or at the interface between cured biomaterial and natural tissue. In a particularly preferred embodiment the mold material can itself become integral to the body of the cured biomaterial.  
         [0015]     The present mold preferably includes both a cavity for the receipt of biomaterial and two or more conduits to that cavity, although a single conduit is suitable for some applications. Some or all of the material used to form the mold will generally be retained in situ, in combination with the cured biomaterial, while some or all of the conduit will generally be removed upon completion of the method. Alternatively, the mold can be biodegradable or bioresorbable.  
         [0016]     Biomaterial generally refers to a material that is capable of being introduced to the site of a joint and cured to provide desired physical-chemical properties in vivo. In a preferred embodiment the term will refer to a material that is capable of being introduced to a site within the body using minimally invasive means, and cured or otherwise modified in order to cause it to be retained in a desired position and configuration. Generally such biomaterials are flowable in their uncured form, meaning they are of sufficient viscosity to allow their delivery through a cannula of on the order of about 1 mm to about 6 mm inner diameter, and preferably of about 2 mm to about 3 mm inner diameter. Such biomaterials are also curable, meaning that they can be cured or otherwise modified, in situ, at the tissue site, in order to undergo a phase or chemical change sufficient to retain a desired position and configuration.  
         [0017]     The present invention includes a method of implanting an intervertebral prosthesis in a disc located between a pair of adjacent vertebrae of a patient. Damaged or diseased nucleus pulpous is removed from the disc using minimally invasive techniques. The adjacent vertebrae are positioned in a lordotic condition. A mold adapted to contain a biomaterial is positioned between the adjacent vertebrae. A flowable biomaterial is delivered into the mold using minimally invasive techniques so that the adjacent vertebrae are in the lordotic condition. The flowable biomaterial is allowed to at least partially cure so that the adjacent vertebrae are in a lordotic-neutral position.  
         [0018]     The step of positioning the pair of adjacent vertebrae in a lordotic condition may include positioning the patient in extension, displacing spinous processes of the adjacent vertebrae to a compressed configuration, suturing spinous processes of the adjacent vertebrae to a compressed configuration, and/or delivering the flowable biomaterial into the mold at sufficient pressure to distraction the adjacent vertebrae to a lordotic position.  
         [0019]     In another embodiment, the step of positioning the pair of adjacent vertebrae in a lordotic condition includes providing the mold with an anterior portion and a posterior portion and delivering the flowable biomaterial to the anterior portion of the mold at a higher pressure than the pressure of the biomaterial in the posterior portion of the mold.  
         [0020]     In another embodiment, the lordotic condition can be achieved by pressurizing the anterior chamber with a liquid and relaxing the tissue surrounding the intervertebral disc space. The biomaterial can then be delivered to the anterior portion of the mold at generally the same pressure as the posterior portion of the mold.  
         [0021]     The step of providing the mold with an anterior portion and a posterior portion can be achieved by locating a partition inside the mold or providing a discrete anterior mold and a discrete posterior mold. In one embodiment, the discrete anterior and posterior molds can optionally be restrained relative to each other by mechanical fastener, a mesh bag, or a variety of other methods.  
         [0022]     In another embodiment, the flowable biomaterial is delivered to the anterior and posterior portions of the mold at a pressure of about 5 atmospheres to about 10 atmospheres for anywhere between a few seconds and a few minutes. Thereafter, the pressure in the anterior portion is reduced and maintained at about 0.5 atmospheres to about 3 atmospheres, while the pressure in the posterior portion of the mold is reduced and maintained at about 0.5 atmospheres to about 2 atmospheres until the biomaterials are at least partially cured. The pressure can be reduced in the anterior and posterior portions of the mold simultaneously or at different times.  
         [0023]     In another embodiment, the anterior portion of the mold is constructed with a first elasticity and the posterior portion of the mold with a second elasticity, wherein the first elasticity is greater than the second elasticity.  
         [0024]     In one embodiment, the lordotic condition comprises about 25 degrees to about 30 degrees of lordosis, and more preferably about 10 degrees to about 15 degrees of lordosis, and most preferably about 15 degrees to about 20 degrees of lordosis. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0025]      FIG. 1  is a schematic illustration of the forces that act on an intervertebral prosthesis during flexion of the spinal column.  
         [0026]      FIG. 2  is a sectional view of the intervertebral prosthesis of  FIG. 1 .  
         [0027]      FIG. 3  is a schematic illustration of an intervertebral prosthesis in accordance with the present invention.  
         [0028]      FIG. 4  is a sectional view of the intervertebral prosthesis of  FIG. 3  during the implant procedure.  
         [0029]      FIG. 5  is a schematic illustration of a multi-chamber intervertebral prosthesis in accordance with the present invention.  
         [0030]      FIG. 6  is a sectional view of the intervertebral prosthesis of  FIG. 5  during the implant procedure.  
         [0031]      FIG. 7  is a schematic illustration of an alternate multi-chamber intervertebral prosthesis in accordance with the present invention.  
         [0032]      FIG. 8  is a sectional view of the intervertebral prosthesis of  FIG. 7  during the implant procedure.  
         [0033]      FIG. 9  is a schematic illustration of an alternate intervertebral prosthesis in accordance with the present invention.  
         [0034]      FIG. 10  is a sectional view of the intervertebral prosthesis of  FIG. 9  during the implant procedure.  
         [0035]      FIG. 11  is a sectional view of an intervertebral disc with a preformed prosthesis in the posterior region and an inflatable prosthesis in the anterior region in accordance with the present invention.  
         [0036]      FIG. 12  is a sectional view of an intervertebral disc with a preformed prosthesis in the anterior region and an inflatable prosthesis in the posterior region in accordance with the present invention.  
         [0037]      FIG. 13  is a sectional view of an intervertebral disc with preformed prostheses in the anterior and posterior region in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]      FIG. 3  is a schematic illustration of an intervertebral prosthesis  50  in accordance with the present invention. Anterior portion  52  of the intervertebral prosthesis  50  has a vertical height  54  greater than posterior portion  56  so that the adjacent vertebrae  58 ,  60  are maintained in lordotic condition  78  in accordance with the present invention.  
         [0039]     The resting position of the lumbar spine at the L3-L4, L4-L5 and S1 vertebrae is normally in a lordotic position. In flexion, the lordosis is decreased or eliminated. In extension, the lordosis is increased. It is also possible to create lordosis by compressing the posterior portion  56  of annulus  70 . This type of lordosis is undesirable because the posterior wall  68  may protrude into the spinal canal  74 , and compressing the spinal cord or otherwise aggravating the patient&#39;s condition.  
         [0040]     In the illustrated embodiment, the intervertebral prosthesis  50  creates a lordotic condition  78  in accordance with the present invention by applying a permanent anterior distraction  62 . The anterior distraction  62  typically applies tension  64  to the anterior longitudinal ligament  66 . The posterior wall  68  of the annulus  70  and the posterior longitudinal ligament  72  are preferably maintained in a neutral or undistracted condition. In an alternate embodiment, the posterior wall  68  and posterior longitudinal ligament  72  may be subject to some distraction or some compression.  
         [0041]     As used herein, “lordotic condition” refers to primarily anterior distraction of a pair of adjacent vertebrae that does not cause symptomatic impingement of the spinal cord by the posterior portion of the intervertebral disc. The posterior wall  68  and posterior longitudinal ligament  72  of the intermediate intervertebral disc may be subject to some compression in the present lordotic configuration, as long as the patient is asymptomatic. The present lordotic condition is such that at least some lordosis is preferably maintained even during flexion of the intervertebral joint.  
         [0042]     After implanting the present prosthesis, the lordotic condition becomes the neutral or resting position of the adjacent vertebrae. As used herein, “lordotic-neutral position” refers to an orientation of the effected adjacent vertebrae in a lordosis when the operative musculature is in a resting state.  
         [0043]     The anterior longitudinal ligament  66  runs in the front (anterior) and vertically (longitudinal) attaching to the front of each vertebra  58 ,  60 . The posterior longitudinal ligament  72  runs vertically behind (posterior) the vertebrae  58 ,  60  from the brain to the tailbone and inside the spinal canal  74 . The ligamentum flavum (not shown) connects under the facet joints and forms a little curtain over the posterior opening between the vertebrae. This curtain can be pushed aside during surgery to allow the physician access to the spinal canal  74 . Smaller ligaments that attach to the vertebral bodies  58 ,  60  to further safeguard the spine against bending too far in any direction join the three ligament systems.  
         [0044]     As illustrated in  FIG. 4 , the preferred method includes one or more annulotomies  80 ,  82  in the annulus  70  laterally enough to avoid damage to the posterior longitudinal ligament  72  and the posterior wall  68  of the annulus  70 . The present method preferably includes an MRI and a discogram preoperative assessment of the intervertebral disc. Interoperatively, a total nucleus removal (“TNR”) is performed. The annulus  70  is preferably preserved as much as possible.  
         [0045]     After the central portion or nucleus pulpous  112  is substantially removed from the annulus  70 , multi-lumen mold  100  is threaded through the annulotomies  80 ,  82  so that mold  104  is positioned within the annular cavity  114 . First lumen  102  is fluidly coupled to mold  104  at location  106 . Optional second lumen  108  is fluidly coupled to the mold  104  at location  110 .  
         [0046]     In a first embodiment in accordance with the present invention, the patient&#39;s body is configured in extension to create the lordotic condition  78  illustrated in  FIG. 3 . The patient may be restrained to the operating table to maintain the spine in extension.  
         [0047]     The mold  104  is substantially filled with biomaterial  120 . The biomaterial  120  can be delivered to the mold  104  through the first lumen  102 , the second lumen  108 , or some combination thereof. In one embodiment, the biomaterial  120  is delivered through the first lumen  102  while a vacuum or reduced pressure condition is applied to the second lumen  108 . In an alternate embodiment, the mold  104  only has a single lumen  102 . In the illustrated embodiment, a portion of the biomaterial  120  is drawn into the second lumen  108  once the mold  104  is fully inflated. After the biomaterial  120  is at least partially cured, the first and second lumens  102 ,  108  are cut, preferably flush with inner surface  122  of the annulus  70 .  
         [0048]     By maintaining the vertebrae  58 ,  60  in the lordotic condition  78 , a greater quantity of the biomaterial  120  flows into the anterior portion  52  than in the posterior portion  56 . The biomaterial  120  cures with a greater vertical height  54  in the anterior portion  52  than in the posterior portion  56 , resulting in a permanent anterior distraction  62  that maintains the vertebrae  58 ,  60  in the lordotic condition  78  of the present invention.  
         [0049]     In a second embodiment, forces  130 ,  132  are applied to the spinous processes  134   136  to create a compressed configuration. As used herein, “compressed configuration” refers to displacing spinous processes of adjacent vertebrae toward each other. The compressed configuration creates the lordotic condition  78  of the present invention.  
         [0050]     The forces  130 ,  132  can optionally be created by wrapping suture material  124  around the spinous processes  134 ,  136 . In one embodiment, the ends of the spinous processes  134 ,  136  are sutured together to create the lordotic condition  78  of  FIG. 3 . In one embodiment, the sutures  124  are cut following at least partial curing of the biomaterial  120 . In another embodiment, the sutures  124  are bioresorbable so that by the time the patient recovers from the surgery, full motion is restored. In another embodiment, reference numeral  124  refers to an elastic material used to maintain tension and to allow flexion motion to occur. In one embodiment, the material  124  is easily removed following at least partial curing of the biomaterial  120 , or at some later time after the surgical procedure.  
         [0051]     Maintaining the vertebrae  58 ,  60  in the lordotic condition  78  causes forces  90 ,  92  to act against the prosthesis  50 , thereby resisting extrusion towards the posterior wall  68 . The angle of the end plates  42 ,  44  tends to urge the prosthesis  50  toward the anterior longitudinal ligament  66 . During flexion the vertebrae  58 ,  60  are preferably still in the lordotic condition  78 , such that the end plates  42 ,  44  still act to retain the intervertebral prosthesis  50  in the intervertebral disc space  76 .  
         [0052]     It is estimated that by maintaining the lordotic condition  78  of about 25 degrees to about 30 degrees, the expulsion force on the prosthesis  50 , even during flexure, is not sufficient to extrude the prosthesis  50  through the posterior wall  68 . For some patients the lordotic condition  78  is preferably about 10 degrees to about 15 degrees, and more preferably about 15 degrees to about 20 degrees, and most preferably about 20 degrees to about 30 degrees, depending on a number of factors such as for example the condition of the annulus, the size of the prosthesis required, the location of the annulotomy, and a variety of other factors.  
         [0053]     In another embodiment, the mold  104  is formed so that inflation of the posterior portion  56  by the biomaterial  120  is constrained relative to the anterior portion  54 . For example, the elasticity of the anterior portion  54  may be greater than the posterior portion. In one embodiment, the posterior portion is constructed from an inelastic material or is optionally surround by an inelastic material. In another embodiment, the anterior longitudinal ligament  66  can be relaxed, as discussed herein.  
         [0054]      FIGS. 5 and 6  illustrate an alternate embodiment of the present method and apparatus. Mold  150  includes an anterior chamber  152  and a posterior chamber  154 . The mold  150  is positioned in the annular cavity  114  as discussed above. In the illustrated embodiment, the mold  150  includes a partition  156  that separates the anterior chamber  152  from the posterior chamber  154 . In the illustrated embodiment, the partition  156  is preferably a rigid or semi-rigid material so that the pressure of the biomaterial  172  in the anterior chamber  152  can be greater than the pressure of the biomaterial  174  in the posterior chamber  154 .  
         [0055]     The anterior chamber  152  includes first and second lumens  160 ,  162  while the posterior chamber  154  includes first and second lumens  164 ,  166 . Although the embodiment of  FIG. 6  illustrate two lumens for each chamber  152 ,  154 , it is possible for the mold  150  to include a single lumen with each chamber.  
         [0056]     The pressure and quantity of biomaterials  172 ,  174  in the respective chambers  152 ,  154  can be independently controlled to permit the vertebrae  58 ,  60  to be positioned in lordotic condition  176 .  
         [0057]     In one embodiment, the biomaterials  172 ,  174  are the same materials. In another embodiment, the biomaterials  172 ,  174  are different materials. The biomaterials  172 ,  174  can be delivered simultaneously or sequentially. In one embodiment, the biomaterial  172  is delivered first. After the biomaterial  172  is at least partially cured, the biomaterial  174  is delivered. In another embodiment, the biomaterial  174  is delivered first. After the biomaterial  174  is at least partially cured, the biomaterial  172  is delivered.  
         [0058]     In another embodiment, the wall  168  of the posterior chamber  154  has a greater wall thickness than wall thickness of the wall  170  of the anterior chamber  152 . The greater thickness of the wall  168  restricts expansion of the posterior chamber  154 , while the lesser thickness of the wall  170  permits the anterior chamber  152  to achieve the greater vertical height  54 .  
         [0059]     In anther embodiment, the wall  168  proximate posterior chamber  154  is constructed from a material with less elasticity than the wall  170  proximate the anterior chamber  152 . In yet another embodiment, tension members can be wrapped around or embedded in the wall  168  to constrain expansion of the posterior chamber  154 .  
         [0060]     In another embodiment, the chambers  152 ,  154  are filled with biomaterials  172 ,  174 , respectively at a pressure of about 5 atmospheres to about 10 atmospheres for anywhere between a few seconds and a few minutes. Thereafter, the pressure in the anterior chamber  152  is reduced and maintained at about 0.5 atmospheres to about 3 atmospheres, while the pressure in the posterior chamber  154  is reduced and maintained at about 0.5 atmospheres to about 2 atmospheres until the biomaterials  172 ,  174  are at least partially cured. The pressure can be reduced in the anterior and posterior chambers  152 ,  154  simultaneously or at different times. For example, the pressure in the anterior chamber  152  may be maintained for a longer period than the posterior chamber  154 . As discussed in connection with  FIG. 3 , the greater vertical height  54  of the anterior chamber  152  applies a permanent anterior distraction  62  that creates the desired lordotic condition  176 .  
         [0061]     In one embodiment, the lordotic condition  176  of the vertebrae  58 ,  60  can be created simply by controlling the flow of biomaterials  172 ,  174  to the chambers  152 ,  154  of the mold  150 . In an alternate embodiment, the method may include positioning the patient in a lordotic condition  176  and/or applying forces  130 ,  132  to the spinous processes  134 ,  136 , such as discussed above.  
         [0062]     In another embodiment, the anterior chamber  152  can be pressurized with a fixed volume of saline or a liquid contrast medium to the level anticipated during delivery of the biomaterial  172 . Images of the intervertebral disc space are optionally taken at various pressures to measure the distraction of the adjacent vertebrate. After a period of time, such as about a few seconds to about five minutes, the tissue surrounding the intervertebral disc space, in particular the anterior longitudinal ligament  66  (see  FIG. 3 ), relaxes causing the pressure measured in the anterior chamber  152  to drop. Additional saline or contrast medium is then introduced into the anterior chamber  152  to increase the pressure in the intervertebral disc space to the prior level. The tissue surrounding the intervertebral disc space again relaxes.  
         [0063]     By repeating this procedure several times, the lordotic position  176  is more easily achieved. In one embodiment, the lordotic position  176  can be achieved by delivering the biomaterials  172 ,  174  at generally the same pressure. The method of relaxing the tissue surrounding the intervertebral disc space can be used with any of the embodiments disclosed herein. In another embodiment, a separate evaluation mold is used to perform the relaxation cycles of the tissue surrounding the intervertebral disc space. Once the relaxation cycles are completed, the evaluation mold is removed and the mold  150  is inserted.  
         [0064]      FIGS. 7 and 8  illustrate an alternate apparatus comprising a discrete anterior mold  200  and a discrete posterior mold  202 . The anterior mold  200  and posterior mold  202  can be securely connected to each other using a variety of techniques. In one embodiment, the anterior mold  200  is securely connected to the posterior mold  202  by one or more mechanical fasteners  204 . In an alternate embodiment, a mesh bag  206  or other containment vessel surrounds both the anterior mold  200  and posterior mold  202 .  
         [0065]     As illustrated in  FIG. 8 , lumen  210  is fluidly coupled to the anterior mold  200  and lumen  212  is fluidly coupled to the posterior mold  202 . In an alternate embodiment, one or more of the molds  200 ,  202  may include secondary lumens, such as illustrated in  FIGS. 4 and 6 .  
         [0066]     In one embodiment, mold  200  is an evaluation mold used to perform the relaxation cycles of the tissue surrounding the intervertebral disc space discussed above. Once the relaxation cycles are completed, the evaluation mold  200  is removed and the molds  200 ,  202  are inserted.  
         [0067]     In one embodiment, the mold  200  is constructed of a material and/or thickness having greater elasticity than the mold  202 . In another embodiment, the mold  200  is configured to create the greater vertical height  54  along the anterior side of the vertebrae  58 ,  60 , and hence, the permanent anterior distraction  62  of the present lordotic condition. In another embodiment, different biomaterials  220 ,  222  are delivered to the molds  200 ,  202 , respectively. The discrete molds  200 ,  202  permit the respective biomaterials  220 ,  222  to be different or the same and/or to be delivered at different pressures.  
         [0068]     As discussed in connection with  FIGS. 5 and 6 , the patient can also be positioned in a lordotic condition and/or forces  130 ,  132  can be applied to the spinous processes  134 ,  136  in order to achieve the illustrated lordotic condition of the vertebrae  58 ,  60  during delivery of the biomaterial  220 ,  222 .  
         [0069]      FIGS. 9 and 10  illustrate another embodiment of the present method and apparatus. Mold  250  is located in anterior portion  252  of the annular cavity  114 . Biomaterial  254  is delivered to the mold  250  through lumen  256 . Biomaterial  258  is delivered through lumen  260  directly into posterior region  262  of the annular chamber  114 , without the use of a mold. The annulus  70  serves as the mold for the biomaterial  258 .  
         [0070]     The mold  250  provides the anterior distraction  62  necessary to achieve the vertical height  54 . The biomaterial  258  helps to secure the mold  250  in the anterior portion  252  of the annulus  70 . The biomaterials  254 ,  258  can be the same or different material.  
         [0071]     In an alternate embodiment illustrated in  FIG. 11 , a preformed prosthesis  280  is delivered through lumen  260  directly into posterior region  262  of the annular chamber  114 . The preformed prosthesis  280  can optionally be constructed from two or more sections that are assembled in situ. The position of the prosthesis  280  within the annular chamber  114  relative to the mold  250  is shown schematically in  FIG. 9  without the interlocking relationship. In the illustrated embodiment, the prosthesis  280  includes one or more structures  282  that engage with the mold  250 . In the preferred embodiment, the biomaterial  254  forces a portion of the mold  250  into recess  282  in the prosthesis  280  to form an interlocking relationship.  
         [0072]     As discussed in connection with  FIGS. 5 and 6 , the patient can also be positioned in a lordotic condition and/or forces  130 ,  132  can be applied to the spinous processes  134 ,  136  in order to achieve the illustrated a lordotic condition of the vertebrae  58 ,  60  during delivery of the biomaterials  254 ,  258 .  
         [0073]      FIG. 12  illustrates preformed prosthesis  290  delivered through lumen  260  directly into anterior region  292  of the annular chamber  114 . The mold  250  is located in the posterior region  262 . The size and shape of the prosthesis  290  relative to the mold  250  creates the lordotic condition. In the illustrated embodiment, the prosthesis  290  includes one or more structures  294  that engage with the mold  250 . In the preferred embodiment, the biomaterial  254  forces a portion of the mold  250  into recess  294  in the prosthesis  290  to form an interlocking relationship.  
         [0074]      FIG. 13  illustrates two or more preformed prostheses  300 ,  302  delivered through lumen  260  into the annular chamber  114 . The prosthesis  300  is located in the anterior region  292 , while the prosthesis  302  is located in the posterior region  262 . In the illustrated embodiment, the prostheses  300 ,  302  preferably have features  304 ,  306  that form an interlocking relationship within the annular chamber  114 . The size and shape of the prosthesis  300  relative to the prosthesis  302  creates the lordotic condition.  
         [0075]     The molds of the present invention can also be used for evaluating the nuclectomy or the annulus and for imaging the annulus prior to delivery of the biomaterial(s). Disclosure related to evaluating the nuclectomy or the annulus, use of an evaluation mold, and delivering the biomaterial are found in U.S. patent application Ser. No. 10/984,493, entitled “Multi-Sage Biomaterial Injection System for Spinal Implants, which is incorporated by reference. Various implant procedures and biomaterials related to intervertebral disc replacement suitable for use with the present method and apparatus are disclosed in U.S. Pat. No. 5,556,429 (Felt); U.S. Pat. No. 6,306,177 (Felt, et al.); U.S. Pat. No. 6,248,131 (Felt, et al.); U.S. Pat. No. 5,795,353 (Felt); U.S. Pat. No. 6,079,868 (Rydell); U.S. Pat. No. 6,443,988 (Felt, et al.); U.S. Pat. No. 6,140,452 (Felt, et al.); U.S. Pat. No. 5,888,220 (Felt, et al.); U.S. Pat. No. 6,224,630 (Bao, et al.), and U.S. patent application Ser. Nos. 10/365,868 and 10/365,842, all of which are hereby incorporated by reference.  
         [0076]     Various delivery catheters and catheter holders suitable for performing the present method are disclosed in commonly assigned U.S. patent application Ser. No. ______, entitled Catheter Holder for Spinal Implants, filed on the same date herewith (Attorney Docket No. 321296), which is hereby incorporated by reference. The molds of the present invention can also be secured to the annulus using any of the methods and devices disclosed in commonly assigned U.S. Patent application Serial No. entitled Multi-Lumen Mold For Intervertebral Prosthesis And Method Of Using Same, filed on the same date herewith (Attorney Docket No. 321297), which is hereby incorporated by reference.  
         [0077]     Patents and patent applications disclosed herein, including those cited in the Background of the Invention, are hereby incorporated by reference. Other embodiments of the invention are possible. Many of the features of the various embodiments can be combined with features from other embodiments. It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.