EP1748747A2 - Prothèse d'unité rachidienne fonctionnelle - Google Patents

Prothèse d'unité rachidienne fonctionnelle

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Publication number
EP1748747A2
EP1748747A2 EP05748919A EP05748919A EP1748747A2 EP 1748747 A2 EP1748747 A2 EP 1748747A2 EP 05748919 A EP05748919 A EP 05748919A EP 05748919 A EP05748919 A EP 05748919A EP 1748747 A2 EP1748747 A2 EP 1748747A2
Authority
EP
European Patent Office
Prior art keywords
facet joint
component
fastener
facet
ligament
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05748919A
Other languages
German (de)
English (en)
Inventor
Hassan A. Serhan
Robert Labrom
John Riley Hawkins
William Dunbar
Amie Borgstrom
Seungkyu Daniel Kwak
Andrew Dooris
Michael A. Slivka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DePuy Spine LLC
Original Assignee
DePuy Spine LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US10/850,280 external-priority patent/US20050055096A1/en
Application filed by DePuy Spine LLC filed Critical DePuy Spine LLC
Publication of EP1748747A2 publication Critical patent/EP1748747A2/fr
Withdrawn legal-status Critical Current

Links

Definitions

  • spine fusion generally helps to eliminate certain types of pain, it has also been shown to decrease function by limiting the range of motion for patients' in flexion, extension, rotation and lateral bending. Furthermore, it is believed that spine fusion creates increased stresses on (and, therefore, ..accelerated degeneration of) adjacent non- fused motion segments. Additionally, pseudoarthrosis, resulting from an incomplete or ineffective fusion, may reduce or even totally eliminate the desired pain relief for the , patient. Also, the fusion device(s) used to effect fusion, whether artificial or biological, may migrate out of the fusion site, thereby creating significant new problems for the patient.
  • the facet's articular surfaces contact in extension, limiting rotation and increasing compressive load.
  • the articular surfaces also contact on one side of the spine in lateral bending and axial rotation, also limiting rotation and transferring load.
  • the facet joints can also be a significant source of spinal disorders and, in many cases, debilitating pain.
  • the articular cartilaginous surfaces can degenerate due to mechanical or biological factors . and cause pain as with other joint osteoarthritis, or enlarge and produce stenosis.
  • a patient may suffer from arthritic facet joints, severe facet joint tropism or otherwise deformed facet joints, facet joint injuries, etc. There is currently a lack of suitable intervention procedures for facet joint disorders.
  • Facetectomy or the removal of the facet joints, may provide some relief, but is also believed to significantly decrease the stiffness of the spinal column (i.e., hypermobility) in all planes of motion: flexion and extension, lateral bending, and rotation.
  • problems with the facet joints can also complicate treatments associated with other .portions of the spine.
  • contraindications for artificial discs include arthritic facet joints, absent facet joints, severe facet joint tropism or otherwise deformed ' facet joints. Accordingly, there is a need for a facet joint replacement that addresses these concerns.
  • 36,758 discloses an artificial facet joint where the inferior facet, the mating superior facet, or both, are simply covered with a cap. Because placement of the cap requires no preparation of the bone or articular surfaces; it covers and, therefore, preserves the bony and articular structures.
  • simple capping of the facet has several potential disadvantages. If the facet joint is osteoarthritic, a cap will not remove the source of the pain. Additionally, at least in the case of surface replacements for osteoarthritic femoral heads, the capping of articular bone ends has proven to lead to clinical failure due to mechanical loosening.
  • Graf ligamentoplasty essentially immobilizes the facet, joint. Gardner does not disclose a mobile ligament that traverses a facet joint.
  • WrPO PCT Published Patent Application No. WO 00/53126 (“Ogun") discloses a memory metal implant for fixing an articulated joint, including a facet joint.
  • the Dynesys system is generally used as a replacement for the natural posterior longitudinal ligament.
  • the system includes a cable housed inside a plastic sheath, and is attached to superior and inferior pedicles.
  • the ligament of the Dynesys system does not traverse a facet joint.
  • , US Published Patent Application No. 2003/0004572 (“Goble") discloses a prosthesis comprising an intervertebral disc prosthesis and a fact joint prosthesis. Goble does not disclose a facet joint ligament.
  • FIG. 12 of Goble discloses a facet joint replacement system wherein each of the superior and inferior components are fixed
  • the superior component of the Goble system has no adjustability (i.e., the screw-articulation surface distance is fixed).
  • the articulation surface appears to be set higher than the pedicle screw securing the inferior component. In such a case, long term bearing may cause twirling of the inferior component about the lower pedicle screw axis.
  • SUMMARY OF THE INVENTION The present inventors have appreciated that natural facet joints are true articulating joints in which the facet joint capsule and surrounding ligaments play a very important role. While the articular surface of the joint transfers compression, the facet joint capsule transfers tension. In flexion, the joint opens and the facet joint capsule and the supraspinous ligament (SSL) is stretched.
  • SSL supraspinous ligament
  • the present invention in'a first part, replaces the natural but diseased disc with an artificial motion disc that more fully provides the natural mechanical relationship provided by a natural healthy intervertebral disc. Accordingly, the disc component of the present invention more closely simulates physiological contributions of the intervertebral disc and so more closely approximates a full natural disc. Also, the present invention, in a second part, replaces the natural facet joint capsule with an artificial construct that more fully provides the natural mechanical relationship provided, by a natural healthy facet joint. In particular ' , by providing a ligament that stretches while resisting tension, thus increasing joint stability, the present invention more closely simulates physiological contributions of the facet joint capsule and so more closely approximates a full natural facet joint.
  • a kit for providing therapy to a functional spinal unit comprising an upper vertebra Vu having an upper vertebral body VBu and an upper facet Fu, a lower vertebra having a lower vertebral body VBL and a lower facet F , the vertebral bodies defining a disc space therebetween, the upper and lower facets defining a facet joint FJ, the kit comprising: a) a motion disc adapted for insertion into the disc space, b) a facet joint replacement (“FJR”) adapted to replace at least a portion of a natural facetjoint comprising first and second facets, and c) a ligament adapted to constrain relative movement between the facets.
  • FJR facet joint replacement
  • FIG. 1 is a'side view of the present invention implanted in a human spine. I
  • FIG. 2 is a posterior view of the present invention implanted in a human spine. I ' ' I
  • FIG. 3 is a 3-piece motion disc component of the present invention. ' (
  • FIG. 4 is a 2-piece motion disc component of the present invention.
  • FIG. 5 is a generic articulating facet joint replacement component of the present invention.
  • FIG. 6 is a preferred articulating facet joint replacement component of the present invention.
  • FIG. 7 is cushion-type facet joint replacement component of the present invention including.
  • FIG. 8a, 8b and 8d are generic ligament components of the present invention.
  • FIG. 8c is a fastener component of the generic ligament component of the present invention.
  • FIG. 9 is a preferred ligament component of the present invention.
  • FIGS. 10a and 10b are depictions of a functional spinal unit (FSU) of a human spine.
  • FSU functional spinal unit
  • FIGS 11 a-11 e are posterior views of a minimally invasive facet joint replacement system.
  • FIG. 12 is a side view of a ball-and-socket type facet joint replacement system.
  • an anatomic "functional spinal unit” or FSU comprising an upper vertebrae having an upper vertebral body Vu and an upper facet Fu, a lower vertebra having a lower vertebral body V L having a lower facet FL.
  • the vertebral bodies lies in. the anterior A portion of the FSU, while the facets lie in the posterior portion P of the FSU.
  • Disposed between the vertebral bodies is a disc, space DISC.
  • Disposed between the facets is an "facet joint",
  • the supraspinous ligament SSL lies posterior to the spinous processes.
  • the Posterior longitudinal ligament PLL lies posterior to the vertebral bodies.
  • the FSU comprising an upper vertebra having an upper vertebral body Vu and an upper facet Fu, a lower vertebra having a lower vertebral body VB L and a lower facet F L , the vertebral bodies defining a disc space therebetween, the upper and lower facets defining a facet joint FJ, the kit comprising: a) a motion disc 101 adapted for ' insertion into the disc space, b) a facet joint replacement system 103 comprising superior 105 and inferior 107 components, the system adapted to replace at least a portion of a natural facet joint comprising first and second facets, and c) a ligament 109 adapted to constrain relative movement between the facets.
  • the motion disc component of the present invention can be any prosthetic capable of at least partially restoring the natural motions of the intervertebral disc.
  • the motion disc is selected from the group consisting of an articulating disc, a cushion disc and a spring-based disc.
  • Various motion discs are described by Stefee et al. in U.S. Pat. No. 5,071 ,437; Gill et al. in U.S. Pat. No. 6,113,637; Bryan et al. in U.S. Pat. No. 6,001,130; Hed an et al. in U.S. Pat. No. 4,759,769; Ray in U.S. Pat. No. 5,527,312; Ray et al.
  • the articulating motion disc is a three-piece design comprising two endplates and a core. Now referring to FIG.
  • the articulating three-piece motion disc comprises: a) a first prosthetic, vertebral endplate 371 comprising: , i) an outer surface 373 adapted to mate with a first vertebral body, ii) an inner surface 375 having a first articulation surface 377, iii) a body portion 379 connecting the inner and outer surfaces, b) a second prosthetic vertebral endplate 381 comprising: i) an outer surface 383 adapted to mate with a second vertebral body, and ii) an inner surface 385 comprising a first articulation surface 387, c) a core member ' 391 .comprising: » . .
  • the articulating motion disc is a two-piece design comprising two endplates.
  • the articulating two-piece motion disc 401 comprises: a) a first prosthetic vertebral endplate 431 comprising: i) an outer surface 433 adapted to mate with a first vertebral body, ii) an inner surface 435 having a first articulation surface 441, ' ' iii) a body portion 443 connecting the inner and outer surfaces, b) a second.
  • prosthetic vertebral endplate 411 comprising: i) an outer surface 413 adapted to mate with a second vertebral body, and ii) an inner' surface 415 comprising a second articulation surface 417, wherein the first and second articulation surfaces are oriented produce an articulation interface.
  • the FJR component of the present invention can be any prosthetic capable of at least partially replacing a natural function of a natural facet joint.
  • the ' facet joints are diarthroidal joints that provide both sliding articulation and load transmission features.
  • the facet's articular surfaces contact in extension, limiting rotation and increasing compressive load.
  • the superior 511 and 'inferior 521 facet joint components of the prosthesis are independent bodies.
  • the superior facet joint component 511 forms a fixation portion 513 having an outer surface 515 adapted to attach to a first facet and aninner articulation surface 517
  • the inferior facet joint component 521 forms a fixation portion 523 having an outer surface 525 adapted to attach to an inferior facet and an inner articulation surface 527.
  • the inner articulation surfaces are adapted to form an articulation interface.
  • this embodiment is called an "articulation prosthesis”.
  • Throughholes 531 are provided in each fixation portion for facilitating the reception of a bone screw to provide bony fixation.
  • the first inner articulation surface is convex shaped, while the second inner articulation surface is concave shaped. This creates a ball and socket joint well known in the art.
  • each of the first inner articulation surface and second inner articulation surface is cylinder-shaped.
  • each of the first inner articulation surface and second inner articulation surface is plane-shaped.
  • the first and second articulation surfaces are conforming. In others, the first and second articulation surfaces are non-conforming. Now referring to FIG.
  • the facet joint replacement component comprises: a) a superior facet joint component 601 comprising: • i) ,a longitudinal body 603 having a superior end portion 605 and an inferior end portion 607, the inferior end portion forming an inner surface 6,09, and " ⁇ ii) a fastener 621 having a. distal threadform adapted to fasten to bone and a proximal groove 623 adapted to receive the superior end portion of the longitudinal body, and , . iii) a set screw 625 received within the proximal groove of the fastener, b) an inferior facet joint component 631 comprising: i) a body portion 633, • ' ii) , .
  • outer portion 635 adapted to attach to bone and having a threaded,. throughhole 637, • iii) an inner portion having an inner surface 639 adapted to articulate with the inner surface 609 of the superior facet joint component, and iv) a fastener 641 received with the threaded throughhole 637.
  • the superior component 601 of the FJR includes a fastener 623 adapted to fasten to the pedicle portion of the superior vertebral body.
  • the pedicle has been selected as the attachment location because of its clinical proven ability to accept pedicle screws under load, its long term viability and surgical familiarity.
  • the superior end portion is designed to extend from facet region to the upper pedicle, and has a diameter designed to fit approximately within the threadform of the fastener, thereby allowing its fixation.
  • the inferior end portion has an inner surface 609 adapted for bearing against the lower FJR component.
  • the lower component 631 of the FJR includes a fastener 641 adapted to fasten to the pedicle portion of the lower vertebral body.
  • the pedicle has again been selected as the attachment location.
  • The. fastener in this case is a pedicle screw.
  • conventional FJR systems do not appear to allow the surgeon to adjust the distance from the pedicle screw component to the articulation surface component.
  • the FJR system of FIG. 6 has special advantage because it allows for intra- operative adjustability of this distance.
  • the upper component of the FJR of FIG. 6 comprises a pedicle screw having a groove adapted to receive the superior end portion of the longitudinal body.
  • the pedicle screw is first inserted into the bone, and the superior end portion of the longitudinal body (which in this case, is rod-shaped) is laid into the groove. The surgeon can then slide the longitudinal body relative to the groove until the appropriate position of the inner surface 609 is set. The " surgeon can then insert set screw 625 into the groove on top of the superior end portion of the longitudinal body in order to lock the position of the inner surface.
  • a facet joint replacement component comprising: a) a body having an elongate first end portion and a second end portion forming an articulation surface, b) a fastener having a shank having distal threadform thereon adapted to fasten to a bone, and a proximal end having a transverse groove adapted to receive the elongate first end portion of the longitudinal body, wherein a portion of the elongate first end portion of the longitudinal body is slidably received in the groove of the fastener.
  • the FJR system of FIG. 6 also has special advantage because it allows for intra- operative adjustability of the orientation.
  • the pedicle screw is a polyaxial screw having a substantially groove adapted to receive the superior end portion of the longitudinal body.
  • the polyaxial nature of this screw allows the surgeon to adjust the orientation of the. groove component of the screw, thereby allowing for adjustment of the orientation of the articulation surface. Therefore, in accordance with the present invention, there is provided a facet joint replacement component comprising: a) ' a body having an elongate first end portion and a second end portion forming an articulation surface, and b) a polyaxial screw adapted for adjustable fixation to the longitudinal body.
  • a facet joint replacement component comprises: a) a first facet joint component comprising: i) a longitudinal body having a first end portion and an second end portion, the inferior end portion forming a first inner articulation surface, and ii) means for attaching the longitudinal body to bone, and b) an second facet joint component comprising: i) a body portion, ii) outer portion adapted to attach to bone and having a throughhole, iii) an inner portion having a second inner articulation surface adapted to articulate with the inner articulation surface of the first facet joint component, and iv) a fastener received with the threaded throughhole, wherein the first and second inner articulation surfaces are adapted to form an articulation interface defining an articulation force vector, and wherein the articulation force vector passes through the fastener.
  • the FJR system of FIG. 6 also has special advantage in that both the superior and inferior components may attach to or abut against another bony structure (e.g., a lamina, pedicle, transverse prpcess or spinous process).
  • the second attachment point may reduce or eliminate a moment upon the pedicle screw.
  • the superior and inferior facet joint components do not have inner articulation surfaces, but rather are joined by an elastic cushion core.
  • the "cushion-type" prosthesis comprises: a) a superior facet joint component 201 forming a superior endplate having an outer surface 203 adapted to attach to a superior facet and an inner surface 205, b) an inferior facet joint component 211 forming an inferior endplate having an outer surface 213 adapted to attach to an inferior 'facet and an inner surface.. 215, .. ' _ • ( c) an elastic core 221 having a superior surface 223 adapted to attach to the inner surface of. the superior facet joint component and an inferior surface 225 adapted to attach to the inner surface of the inferior facet joint component.
  • this embodiment is called a "cushion prosthesis".
  • the device comprises an elastomer adapted to elastically compress during axial loading and relax when the load is lifted.
  • the fixation portions thereof may comprise an attachment feature.
  • Preferred attachment features are selected from the group consisting of teeth, keels, spikes, pins, holes, and combinations thereof.
  • the facet joint replacement comprises: " a) a superior facet joint component 511 having a superior fixation portion 513 having an outer surface 515 adapted to attach to a superior facet, and b) an inferior facet joint component 52.1 having an inferior fixation portion 523 having an outer. surface 525 adapted to attach to an inferior facet.
  • the attachment surfaces of the FJR are adapted to attach to the spinous process.
  • the attachment surface of the FJR are adapted to attach and/or bear against a lamina.
  • the attachment surface of . the FJR are adapted to attach to a pedicle.
  • the attachment surface of the FJR are adapted to attach to a transverse process.
  • the 10 attachment surface of the FJR are adapted to attach to a native facet.
  • bony attachment of the attachment surface of the FJR is enhanced by the use of an adhesive, such as fibrin glue or bone cement.
  • the fastener and/or the bony attachment surface of an FJR component comprises a material having osteobiologic properties. This material will help ⁇ 15 the osteointegrative process needed for secure attachment of the fastener and/or the attachment surface to the bone.
  • the fastener ' 'and/or the attachment surface comprises an orthoconductive portion.
  • the orthoconductive portion typically has a porosity (preferably ' between about 20 ⁇ m and 250 ⁇ m) that is adapted to allow the ingress of the 20 osteoconductive cells and an internal surface defined by the porosity that is adapted to attach these cells.
  • the fastener has an outer surface adapted for bony ingrowth. This, outer surface may have an osteoconductive coating thereon, such as a TCP coating or a hydroxyapatite coating.
  • the fastener and/or the attachment surface comprises an 25 orthoinductive portion.
  • the orthoinductive portion is preferably a protein, and is more preferably a growth factor. Preferred growth factors include factors from the TGF-beta, IGF-, BMP- and CDMP- families.
  • the fastener and/or attachment surface comprises an orthogenetic portion.
  • the orthogenetic portion preferably comprises mesenchymal stem 30 cells. More preferably, the MSCs are present in a concentration greater than that present in the patient's natural bone marrow.
  • the fastener and/or the attachment surfaces may also be coated with other desired agents such as antithrombic or antimicrobial coatings, and pain relievers such as NSAIDS.
  • the fastener component of the FJR system is a pedicle screw.
  • the pedicle screw comprises a longitudinal shank having an integral nut thereon. , Distal to the nut,.
  • the shank has a first, distal threadform thereon and a distal tapered end. Proximal to the integral nut, the shank has a second , proximal threadform thereon and a proximal attachment, end having a slot.
  • the pedicle screw is a polyaxial screw.
  • the fastener has a cannulated shank defining a bore that allows for bony ingrowth into the bore. In some embodiments, this bore defines an inner surface adapted for bony ingrowth. This inner surface may have an osteoconductive coating thereon, such as a TCP coating or a hydroxyapatite coating.
  • the superior and inferior facet joint components of the present invention may be made from any material appropriate for human surgical implantation, including but not limited to all' surgically appropriate metals including titanium, titanium alloy, chrome. alloys and stainless steel, and hon-metallic r materials such as carbon fiber ' materials, resins, plastics and ceramics.
  • the elastic core if selected, may comprise polyurethanes, foamed polyethylene, silicones, rubbers, copolymers or hydrogels.
  • the FJR component is unilateral. A unilateral FJR at least partially replaces the function of a single facet joint.
  • the FJR component is bilateral. A bilateral FJR at least partially replaces the function of both facet joints of an FSU.
  • the FJR component replaces a single articular process of a facet joint. This replacement process is adapted to articulate with the natural articular process that remains. In some embodiments thereof, the superior process is replaced, while in other the inferior process is replaced. In other embodiments, the FJR component replaces both articular processes of the facet joint, and these replacement process articulate with each other. In some embodiments, substantially the entire articular process is replaced with a prosthetic FJR. In others, substantially only the articular surface of the object process is replaced, thereby preserving the underlying bony structure. This replacement surface is adapted to articulate with the natural articular process surface that remains; In some embodiments, the replacement surface comprises a cap.
  • the FJR component is a single level FJR.
  • a single level FJR at least partially replaces the function of a single level FSU.
  • the FJR component is a multi-level FJR.
  • a multi-level FJR at least partially replaces the function of facet joints in at least two levels of FSU.
  • the FJR is adapted to replace the natural arch, and so comprises a transverse arch component.
  • the FJR is adapted to replace a natural process, and so comprises a spinous process component.
  • the FJR is adapted to replace at least one natural transverse process, and so comprises a transverse process component.
  • the FJR is adapted to , replace at least one pedicle, and so comprises a pedicle component.
  • a generic ligament 3 of the present invention i) an intermediate portion 5, ii) first and second end portions 7,9, and iii) first and second conformable portions 1 1 , 13, wherein the first conformable portion is disposed between the intermediate portion and the first end portion, and the second conformable portion is disposed between the intermediate portion and the second end portion, and iv) first and second fasteners 15,17, and wherein the first end portion 7 is shaped to cooperatively connect to the first fastener 15, and the second end portion 9 is shaped to cooperatively connect to the second fastener 17.
  • the fasteners are selected from the group consisting of bone screws,, hooks, wires, and pins.
  • the intermediate portion of the ligament is selected from the' group consisting of a cable, a wires, an interconnected face, and a soft polymer bonded to the fastener and stretching between the superior and inferior fastener.
  • the facet, joint is stabilized in both compression and tension by a prosthetic ligament having fasteners fixated either in the superior and inferior vertebrae or . in superior and , inferior prosthetic facet joint components.
  • the fasteners are selected from the group qonsisting of bone screws, hooks, wires, and pins.
  • the intermediate portion of the ligament is selected from the group consisting of a cable, a wires, an interconnected face, and a soft polymer bonded to the fastener and stretching between the superior and inferior fastener.
  • the ligament is shaped as a sheath that can prevent debris produced by the facet articulation from spreading to the surrounding tissues, in particular to various neural structures.
  • Previous facet joint replacement inventions describe resurfacing techniques that replace the contacting faces of the facet joint wit metals or polymers. Due to unique variation in motions of the facet.. joint, these resurfaced contacting faces will r inevitably produce wear debris, which is likely to irritate tissues.
  • a membrane or sheath that surrounds the contacting faces and captures generated particles can reduce tissue irritation and inflammation.
  • the membrane or sheath may also have structural integrity in itself and resist over- stretching and thereby supply resistance to tension.
  • the width of the sheath is much greater.
  • the sheath is sized to substantially enclose the facet joint.
  • the sheath is fluid permeable. This feature permits the ingress of fluids that help lubricate the joint, while preventing the egress of wear debris from the facet joint articulation surfaces.
  • the sheath contains a lubricating fluid, thereby imitating a natural facet joint capsule.
  • the sheath may be pre-assembled prior to implantation, or it may be attached via glues, sutres, wires, thermally activated coagulation or in situ polymer embedding.
  • this prosthetic facet joint ligament can be attached to anchoring points on, opposing sides of a natural or prosthetic facet joint to provide a constraint'against relative movement of the facet joints.
  • the ligament of the present invention can be made of any biocompatible material adapted for constraining but not totally eliminating relative movement between facet joints.
  • the facet joint ligament of the present invention mimics the natural facet joint capsule.
  • the ligament of the present invention comprises three features. First it must be adapted to traverse a facet joint.
  • the ligament comprises a pair of attachment end portions and an intermediate portion.
  • the intermediate portion of the ligament may be adapted to have desirable mechanical qualities found in ligaments, such as elasticity, flexibility, tensionability, and extensibility. Combinations of these qualities allows some displacement of the articular surfaces, but resists excessive displacement.
  • the intermediate portion of the facet joint ligament comprises a,.
  • nonbioresorbable material including polyesters, (particularly aromatic esters such' as polyalkylene terephthalates, polyamides; polyalkenes; poly(vinyl fluoride); polyurethanes; polytetrafluoroethylene (PTFE); carbon fibres; silk; rubber, hydrogels, and glass, and mixtures thereof.
  • the intermediate portion of the facet joint ligament is provided as a fabric.
  • the fabric may be formed by a flat or circular weaving, knitting, braiding, crocheting or embroidery.
  • the fabric is braided in order to provide a high tensile strength.
  • Preferred materials suitable for use as fabrics include polyester, polypropylene, polyethylene, carbon fiber, glass, glass fiber, polyurethane, polyaramide, metals, polymers, copolymers, polyactic acid (PLA), polyglycolic acid (PGA), silk, cellusoseic acid, and polycaprolactone fibers.
  • PPA polyactic acid
  • PGA polyglycolic acid
  • silk cellusoseic acid
  • polycaprolactone fibers It is anticipated that, in use, the intermediate portion of the facet joint ligament may rub against soft tissue structures and damage not only those structures but itself as well. Therefore, in some embodiments, the intermediate portion of the facet joint ligament is lubricated. The lubricants lowers the friction coefficient between the ligament and the soft tissue, thereby lowering the wear.
  • the ligament comprises a material having orthobiologic properties. This material will help the body's regenerative processes regrow a natural ligament to replace the prosthetic ligament of the present invention.
  • the ligament comprises a material having pain relief properties, such as an NSAID.
  • the ligament comprises an orthoconductive portion.
  • the orthoconductive portion typically has a porosity (preferably between about 20 ⁇ m and 250 ⁇ m) that is adapted to allow the ingress of the osteoconductive cells and an internal surface defined by the porosity that is adapted to attach these cells.
  • the orthoconductive portion comprises subintestinal submucosa (SIS).
  • the ligament comprises an orthoinductive portion.
  • the orthoinductive portion is preferably a protein, and is more preferably a growth factor. Preferred growth factors include factors from the TGF-beta and IGF- families.
  • the ligament comprises an orthogenetic portion.
  • the orthogenetic portion preferably comprises mesenchymal stem cells. More preferably, the . MSCs are present in a concentration greater than that present in the patient's natural bone marrow.
  • only the intermediate portion of the ligament comprises an orthobiologic material.
  • only the attachment end portion of the ligament comprises an orthobiologic material.
  • each of the intermediate and attachment end portions of the ligament comprises an orthobiologic material.
  • the ligament is provided in a sterile form.
  • the ligment is sterilized, and then placed in a package.
  • the inside surface of the package is also sterile.
  • the intermediate portion of the ligament is tensionable.
  • a tensionable ligament sags when the ends of the ligaments are moved sufficiently closed to one another so that length of the ligament is less the distance between its ends. This quality allows the opposing facets to move closer to each other under loads without resistance from the ligament.
  • a tensionable ligament also becomes taut when its ends are moved sufficiently away 'from one another so that length of the ligament is about equal to the distance between its ends. This quality constrains relative movement between the opposing facets.
  • the tensibility of the ligament is between 5 and 50 N/mm. , ⁇ , In some embodiments, at least a portion of the intermediate portion of the ligament is extensible.
  • An extensible ligament has a first at-rest length when its ends are not loaded, and a second larger length when the ligament is subjected to tensioning. This quality allows the ligament to "give' a predetermined amount under tension. This quality is advantageous because the natural facet joint ligament is also extensible.
  • the ligament has an extensibility of between 10% and 30% of the at-rest length of the ligament when subjected to a load of about 250 N. In some embodiments, the extensibility of the ligament is between 5 and 50 N/mm.
  • the ligament is not extensible., ; In some embodiments, at least a portion of the intermediate portion of the ligament is flexible.
  • a flexible, ligament bows under axial ' loading/easily bends under ⁇ physiologic flexural loading and easily regains its shape when the loading is ceased. This quality allows the ligament to "give' a predetermined amount while transferring stress under axial loading. This quality is advantageous because the natural facet joint ligament is also flexible.
  • the flexible portion of the ligament comprises a curved portion.
  • the ligament is adapted to allow restricted motion of the FSU throughout the life of the patient.
  • the ligament is designed to have time-variable properties.
  • the ligament is adapted to provide a stiffness that decreases over time. In this condition, the ligament can provide a desirably high stiffness in the immediate post-operative period, thereby stabilizing the region and promoting tissue repair and osteointegration.
  • the ligament stiffness decreases, thereby allowing for a desirable range of motion of the FSU.
  • the ligament has a final (6-month) stiffness such that the stiffness of the FSU at that time is in the range of about 1-2 Nrn/degree of flexion.
  • the ligament preferably has a final (6-month) stiffness such that the stiffness of the FSU at that time is in the range of about 2-3 Nm/degree of extension.
  • the ligament has an initial stiffness that is between about 2-4 times its final (i.eembroidered 6-month) stiffness. Without wishing to be tied to a theory, it is believed that if the initial stiffness were over about 4 times the final stiffness, fusion would result. These values provide both the desired high stiffness required for initial stabilization of the region, and long-term flexibility for the FSU.
  • the variability in the stiffness of the ligament is accomplished by providing a ligament that experiences . significant creep over time. In
  • the creeping ligament comprises a polymer, preferably selected from the group consisting of a polyester, a polyolefin and PTFE.
  • the variability in the stiffness of the ligament is accomplished by providing a resorbable material in the ligament.
  • the ligament comprises both non-resorbable and resorbable materials. After implantation, each of the non-resorbable and resorbable materials conribute to the initial high stiffness of the ligament. Over time, the resorbable materials degrades away, thereby lowering the ligament stiffness.
  • the intermediate portion of the ligament comprises non-resorbable fibers and resorbable fibers.
  • the intermediate portion of the ligament comprises a non-resorbable fiber and a resorbable fiber selected from the group consisting PLA, PGA, . PLGA, and mixtures thereof.
  • Each attachment end portion of the ligament is adapted to attach to an anchoring surface on opposite sides of the facet joint.
  • the attachment end portion comprises a fastener.
  • attachment may be provided by sutres or biologically compatible . glues.
  • an attachment end portion can simply be terminus being identical in design to the intermediate portion. In such a case, the terminus is inserted into a port located on the anchoring surface, such as a port on a prosthetic.
  • the attachment end 'portions of the facet joint ligament comprise a pair of fasteners.
  • the function of the fastener is to join to attachment surfaces located on either side of the facet joint in order to securely fasten the intermediate portion of the facet joint ligament across the facet joint.
  • the fastener may.be adapte to fasten the facet joint ligament to attachment surfaces located upon either: a) a facet joint prosthetic component, or b) a bony surface located adjacent the facet joint prosthetic component.
  • the attachment end portions of the prosthetic ligament of the present invention may be attached to any two anchoring surfaces on opposite sides of the facet joint, provided the ligament traverses the facet joint .
  • the first attachment end portion of the ligament is adapted to attach to a first load-bearing portion of a facet joint prosthesis. This embodiment is surgeon friendly in that the attachment can be made by the manufacturer prior to surgery, thereby providing ease of use and repeatability.
  • at least one end of the. ligament includes a loop having a diameter slightly larger than the shaft diameter of a pedicle screw.
  • first attachment end portion of the ligament is adapted to attach to a portion of the natural vertebra.
  • the vertebral body is used as the anchoring surface.
  • the pedicle portion of the vertebral body is used as the anchoring surface.
  • the facet portion of the vertebra is the anchoring surface.
  • a side wall of a spinous process is used as an anchoring surface.
  • each of the upper and lower fasteners 901 of the ligament 903 are respectively attached to the respective side walls, 905 of upper and lower spinous processes.
  • the first , end portion of the ligament is adapted to attach to the transverse process.
  • the first end portion of the ligament is adapted to attach to the pedicle.
  • the ligament is wrapped around the facet joint.
  • the fastener is a barbed anchor, as it prevents pullout and is easily inserted.
  • the fastener may be a bone fastener.
  • the fastener 19 comprises a longitudinal shank 21, an insertion end 23 comprising protrusions 25 laterally extending from the ,. shank, and an attachment end 27 having an upper surface 31 for connecting to the ligament.
  • the lateral protrusions have leading edges 28 which define an angle ' or of no more than 45 degrees relative to the axis of the shank. In such embodiments, the bearing of the leading edge against the vertebral body surface will not substantially , impede the progress, of the bone fastener into the bone.
  • the leading edges define an angle of no more than 30 degrees, and more preferably between about 20 degrees and 30 degrees.
  • the angle ⁇ is between 20 and 30 degrees, the angle is sufficiently small to not impede the progress of the bone fastener, and yet sufficiently . large to insure its secure fit.
  • the height H of the protrusions on the bone fastener is no more than 70% of the diameter D of the longitudinal shank. When this condition is selected, the risk that any protrusion will act as a shoulder and stop further entry of the bone fastener into the vertebra is minimized.
  • the H/D ratio is no more than 40%, more preferably between about 20% and 40%.
  • the protrusion height is sufficiently small to not impede the progress of the bone fastener, and yet sufficiently large to insure its secure fit.
  • the outer diameter, (2H+D) of the bone fastener is preferably between about 3 — 9 mm, more preferably about 4 - 6 mm.
  • the length L B F of the bone fastener is preferably between about 3 - 45 mm, more preferably between about 15 - 25 mm.
  • the attachment end of the bone fastener is made of a ceramic material. When the bone fastener is ceramic, it can withstand the high impact of the driver without failing. In some embodiments, at least the end portions of the intermediate portion and the attachment end of the bone fastener are made of the same material.
  • the attachment end 27 of the fastener is configured to accept a driver element.
  • the bone fastener may be driven into the bone by simply providing axial force, to the upper surface 31 of the fastener through the driver. Therefore, in accordance with the present invention, there is provided a facet joint ligament comprising:
  • a ligament comprising first and second end portions, and b) first and second fasteners, wherein the first bone fastener is connected to the first end portion of the ligament, and the second bone fastener is connected to the second end portion of the ligament, and wherein the first bone fastener is configured to accept a driver.
  • the .configuration defines a recess 29 upon the upper surface 31 of the attachment end 27 of the fastener. This recess 29 is configured to accept the driver (not shown).
  • the recess 29 of the bone fastener may be configured to allow insertion of a rescue screw, thereby allowing retrieval of the bone fastener.
  • the fastener comprises a material having orthobiologic properties.
  • the fastener surface comprises an orthoconductive portion.
  • the orthoconductive portion typically has a porosity (preferably between about 20 ⁇ m and 250 ⁇ m) that is adapted to allow the- ingress of the osteoconductive cells and an internal surface defined by the porosity that is adapted to attach these cells.
  • the fastener comprises an orthoinductive portion.
  • the orthoinductive portion is preferably a protein, and is more preferably a growth factor.
  • Preferred growth factors include factors from the TGF-beta, IGF-, BMP- and CDMP- families.
  • MP52 is selected as the CDMP. .
  • the fastener comprises an orthogenetic portion.
  • the orthogenetic portion preferably, comprises mesenchymal stem cells. More preferably, the MSCs are present in a concentration greater than that present in the patient's natural bone marrow.
  • the ligament and fastener components are pre-connected. That is, the components are physically attached prior to their placement upon the spine. Pre- connected components are advantageous because their secured attachment to each other are guaranteed, and the surgeon need not waste time in making the attachment. Components may be pre-connected by physical locking, physical connection, or bonding, or by making ' the, components from the same material and integrally connecting them.,.
  • a facet joint ligament comprising: a) a ligament comprising first and second end portions, and b) first and second fasteners, wherein the first fastener is pre-connected to the first end portion of the ligament, and the second fastener is pre-connected to the second end portion of the ligament.
  • at least a portion of the ligament comprises a spring.
  • the spring quality allows the ligament to initially yield to and eventually resist an axial compressive or tension load.
  • the spring is an expansion spring.
  • the spring is a compression spring.
  • the invention limits the natural spinal extension.
  • extension is limited to no more than 7 degrees, preferably no. more thah 5 degrees.
  • the device produces a spine stiffness is at least 2 Nm/degrees in order to so limit the extension.
  • the invention resists flexion.
  • flexion is limited to no more than 15 degrees, and preferably is no more than 12 degrees.
  • the tensile strength of the prosthetic capsule is between 50 and 300 N, is preferably at least 100 N, and is more preferably at least 200 N.
  • the invention resists axial rotation.
  • a pair of devices of the present invention are preferably used so that each facet joint of a functional spine unit has a device, whereby a first device limits the axial rotation while, the ligament of the second device is put in tension. This motion tends to produce coupled motion with flexion and lateral bending.
  • the prosthetic articulating surfaces of the first device are sufficiently strong, to withstand compressive forces of at least 100N, and more preferably at least 150N, and more preferably at least 200N.
  • the invention resists at least anterior-posterior shear.
  • the prosthetic articulating surfaces contact and the prosthetic articulating surfaces are sufficiently strong to withstand anterior-posterior contact shear forces of at least 500N, and more preferably at least 750N, and more preferably at least 1000N.
  • anterior-posterior contact shear forces of at least 500N, and more preferably at least 750N, and more preferably at least 1000N.
  • the patient's superspinous ligament is often damaged.
  • the SSL is important to the stability of an FSU due to its significant role in restraining patient flexion.
  • the ligament of the present invention is adapted to at least partially replace the function of the SSL.
  • the ligament of the present invention has high flexibility and a high ultimate tensile strength.
  • the prosthetic SSL has a tensile strength of at least 50 N, preferably at least 100 N, more preferably at least 150 N, most preferably at least 200 N.. .. . .
  • the ligament of the , ⁇ resent invention is adapted to at.least partially replace the function of the interspinous ligament (ISL).
  • the ligament of the present invention is adapted 'to at least partially replace ,the function of the facet joint capsule (FC).
  • the ligament of the present invention is adapted to at least partially replace the function of the ligamentum flavum (LF). This embodiment may be selected when the posterior arch is removed.
  • the present invention comprises two ligaments adapted to at least partially replace the functions of at least two ligaments selected from the group consisting of the superspinous ligament (SSL), the interspinous ligament (ISL), the facet joint capsule (FC), and the ligamentum flavum.
  • the present invention comprises three ligaments adapted to at least partially, replace the functions of at least three ligaments selected from the group consisting of the superspinous ligament (SSL), the interspinous ligament (ISL), the,, facet joint capsule (FC) , and the ligamentum flavum. ' .
  • the present invention comprises three ligaments adapted to at least partially replace the functions of each of the superspinous ligament (SSL), the interspinous ligament (ISL), the facet joint capsule (FC) , and the ligamentum flavum.
  • the present invention may be used in therapeutic procedures designed to alleviate facet arthritis, stenosis, , spondylolysthesis, post-laminectomy kyphosis, and scoliosis.
  • the present invention may also be used in conjunction with the following surgical procedures: decompressive laminectomy, facet resection, lamina resection, and vertebroplasty.
  • the. motion disc is implanted in substantial accordance with the methods described in US Provisional Application USSN 60/459,280, Hawkins et al., filed March 31, 2004, entitled “Method and Apparatus for Disc Insertion", Attorney Docket No. 3518.100-001, the specification of which is incorporated by reference in its entirety
  • the surgeon uses a standard posterior approach (either bilateral or unilateral) to uncover the facet joint.
  • the surgeon resects (excises) the facet processes, using standard resection instruments, such as a rongeur or a curette.
  • the surgeon prepares the surface of each pedicle for insertion of a pedicle screw. This entails locating the appropriate trajectory, probing the pilot hole, and preparing the pedicle surface to receiving the screw.
  • the surgeon implants the, superior pedicle screw into the superior pedicle, and places a looped end of a ligament around the screw head.
  • the surgeon places the longitudinal portion of the superior component into , the groove of the screw head, and then places a set screw on top of that longitudinal portion, effectively securing the longitudinal portion.
  • the length of the superior component should be such that one surface abuts the natural superior arch. If the surgeon decides to adjust the length of the superior ' component, the surgeon need only untighten the superior screw and readjust the length as desired.
  • the superior component can be used as a template for fixing the location of the inferior component.
  • the articulation surfaces of the two components are aligned in the desired positions (typically producing a gap therebetween).
  • the alignment should be such that the inferior articulating force travels through the axis of the lower pedicle screw.
  • the location of the screw hole is marked, and a pilot hole is drilled.
  • a looped end of a ligament is placed around the pilot hole and the inferior body is oriented to align the pilot hole with the hole in the inferior component.
  • a pedicle screw is inserted through the inferior component and into the pilot hole, thereby fixing the location of the inferior component.
  • the facet joint replacement constructs identified above provide the necessary limitations on flexion, extension and. rotation of the functional spinal unit, the large size of these constructs may also require that , they be implanted through relatively invasive open procedures. In addition, these constructs tend to require complete removal of the facet joint capsule. ' . ' , ' Accordingly, in some embodiments of the present invention, the facet joint replacement constructed is designed to allow for its implantation via a surgical technique causing minimal trauma to the facet joint .capsule and surrounding soft tissues to the extent possible. Therefore, in some embodiments, these goals are achieved by replacing the natural facet joint with a construct comprising a bone screw having a head adapted for facet-type articulation. Now referring to FIG.
  • the surgeon selects a posterior approach with slight lateral-inferior angulation and makes a small incision to access the targeted facet joint. Once access is attained, the surgeon removes the superior facet and the surface of the.. ' inferior facet to produce an -attachment surface 801 on the remaining portion of the inferior facet.
  • the surgeon inserts the inferior facet replacement • component into the facet joint by passing the screw through the pedicle and into the vertebral body.
  • the inferior facet replacement component comprises a bone screw having a threaded shaft 803 and a proximal head 805 adapted for articulation. This approach provides both minimal invasion and a high fixation strength.
  • a superior facet replacement 807 is implanted (preferably through the same incision used to implant the inferior component) and is then secured to a surface of the superior lamina. In this case, securement is accomplished by passing a bone screw 809 through the superior component.
  • this superior component comprises a hook (not shown) on its anterior side.
  • the superior component has a general U-shape to enhance its security to the lamina •Now referring to FIG. Hd, in other minimally invasive embodiments, the MIS superior and inferior components shown above can be connected by at least one ligament 811 to form a pre-assembled facet joint.
  • this pre-assembled facet joint is inserted as a whole and fixed as previously described. In other embodiments, this pre-assembled facet joint is inserted piecemeal and assembled in-situ.
  • the superior facet replacement component may be secured to the spine via attachment to a translaminar bolt 813 inserted into the lamina through a second small incision. As above, the anterior side of the superior facet replacement preferably has a hook to grab onto the lamina.
  • facet-derived pain is eliminated by denervation and the facet joint replacement component is replaced with a facet joint augmentation component. ' . '
  • a primary therapy is first applied to the medial branches and dorsal ra i to denervate the nerves in these regions.
  • the therapy is selected from the group consisting of an energy source (such as pulsed radiofrequency (RF) waves, ultrasound, and microwave), chemical treatment, and freezing.
  • RF radiofrequency
  • the patient Upon the completion of the primary therapy, the patient will be positioned to offload the facet joints and an injectable material (such as a silicone, a polymethsiloxane, a polyurethanes, a hydrogel, and hyaluronic acid) is injected from a syringe into the facet joint to produce a facet joint augmentation within the facet joint, in some embodiments, the injectable material is loaded with at least one therapeutic agent including but not limited: to preservative-free morphine, bupivacaine, tetracaine, opioids, tramadol, ziconotide, betamethasone, clonidine, amitriptyline, fluoxetine, anticonvulsants (such as topiramate), carbamezapine, gabapentin, methlprednisolone acetate morphine3, aminocaproic acid, anti-TNFc molecules,growth factors (such as TGF-b3, TGF-bl, GDF-
  • a method of treating a facet joint comprising, the steps of: a) injecting an augmentation material into the facet joint.
  • other therapeutic agents such as methlprednisolone acetate morphine3, aminocaproic acid or Anti-TNF ⁇ molecules, and/or growth factors such as TGF-b3, TGF-bl, GDF-5 could be injected into the facet joint when the augmentation material is not used.
  • FIG. 12 there is provided another embodiment of the present invention in which a portion of the elongate first end portion of the longitudinal body is slidably received in the groove of the fastener (as in FIGS.l and 2).
  • FIG. 12 there is provided
  • ⁇ provided a prosthetic facet joint based upon a ball and socket articulation.
  • Pedicle screws are placed superior and inferirorly of the involved level,, and. hardware connected to the

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Abstract

Système de remplacement de facette possédant une tige allongée et une vis polyaxiale dotée d'une gorge, dans lequel la tige est reçue de façon coulissante dans la gorge de la vis polyaxiale.
EP05748919A 2004-05-20 2005-05-18 Prothèse d'unité rachidienne fonctionnelle Withdrawn EP1748747A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US10/850,280 US20050055096A1 (en) 2002-12-31 2004-05-20 Functional spinal unit prosthetic
PCT/US2005/017346 WO2005112835A2 (fr) 2002-12-31 2005-05-18 Prothèse d'unité rachidienne fonctionnelle

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EP1748747A2 true EP1748747A2 (fr) 2007-02-07

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JP (1) JP2007537834A (fr)
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CA (1) CA2566645A1 (fr)

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JP2010530780A (ja) * 2007-06-22 2010-09-16 シンピライカ スパイン， インコーポレイテッド 脊髄分節の制御された屈曲制限のための方法およびデバイス
EP2346425A4 (fr) * 2008-11-12 2012-04-18 Simpirica Spine Inc Appareil de contrainte modulée et procédés d'utilisation
JP4995978B2 (ja) * 2011-03-15 2012-08-08 宏美 林 人体を除く生体の治療方法

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AU2005244913A1 (en) 2005-12-01
CA2566645A1 (fr) 2005-12-01

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