Patent Application
20050277921
The present disclosure relates generally to artificial replacement devices and supplements, and more particularly, to prosthetic joints and nucleus supplementation.
Facet joints are also called zygapophyseal joints. They are located in the posterior column of the spine and on the tips of the articular processes. They are formed by the articular processes of adjacent vertebrae—the inferior articular process of a vertebra articulates with the superior articular process of the vertebra below. Facet joints are synovial gliding joints because the articular surfaces glide over each other. They are important in stabilizing the spine, and carry approximately 20% of the compressive load on the spine. Accordingly, their anatomic position and orientation affect the mobility of each spinal region. For example, in the cervical region, facet joints are oriented in the coronal plane and are capable of a significant range of motion in the six degrees of freedom. In the lumbar area, the facet joints are oriented in the sagittal plane.
Major trauma, repetitive minor trauma, or many other factors may cause a facet joint to degenerate. As a result, the hyaline cartilage that lines the joint will lose its water content, and eventually becomes worn out completely. Then, the articular processes begin to override each other as the joint capsules become stretched, resulting in the malalignment of the joints and abnormal biomechanical function of the motion segment.
Since facet joints work with discs to support spinal loads, an injured or traumatized disc may also cause the joints to degenerate. As a person ages, discs often experience anatomical changes. By the age of fifty, over 95% of the people will exhibit evidence of disc degeneration. The most significant alterations to the disc include the decrement of water and proteoglycan content of its nucleus pulposus. As a result, the disc begins to lose its normal height, and becomes less resistant and resilient to loading forces. In particular, the nucleus pulposus looses the ability to sustain hydrostatic pressure. In essence, the disc no longer fully acts like a shock absorber between the vertebral bodies. To cope with the degraded disc, load is transferred from the central nucleus to the peripheral annulus, resulting in loading changes to the vertebral facets and damages to joints. For example, a decreased disc height results in overriding of the facets, causing loss of cartilage and a hypertrophic process on the articular surfaces. Given time, the natural adaptive processes may significantly re-model the facet joint anatomy.
Previous treatments of degenerated joints possess many problems. For example, in many instances, treatments emphasize the anterior, but not the posterior column of the spine. Also, spinal fusion has been widely used to repair damaged discs. However, fusion decreases joint functions by limiting the range of motions in flexion, extension, rotation, and lateral bending at the affected level. At the levels adjacent to a fused level, the disc is exposed to abnormal stresses and hypermobility.
Previous treatments of degenerated nucleus pulposus also possess a number of problems. For example, nucleus replacements have been utilized to treat degenerated nucleus pulposus. However, those replacements cause damages to discs by violating the annulus fibrosus.
In one embodiment, a prosthetic joint comprises: a tip adapted for mating against a superior articular process of an inferior vertebra wherein the tip acts as a spacer between the superior articular process and an inferior articular process of a superior vertebra; and an elongated body for mating against a hole in the superior vertebra wherein the body comprises a surface that is uneven along its length.
In another embodiment, a method for restoring motions of a joint comprise: providing a body for a prosthetic joint; threading a surface of the body wherein the threading extends an entire length of the body; and creating an internal cavity in the prosthetic joint.
In a third embodiment, a method for spacing intervertebral facets to prevent bone-on-bone grinding comprises: applying a material between a superior facet of an inferior vertebra and an inferior facet of a superior vertebra wherein the material provides articulation.
In a fourth embodiment, a method for pressurizing nucleus pulposus, comprise: providing a device for delivering a substance into a disc space wherein the substance pressurizes nucleus pulposus of a disc without violating annulus fibrosus of the disc.
For the purposes of promoting an understanding of the principles of the invention, references will now be made to the embodiments, or examples, illustrated in the drawings and specific languages will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
The present disclosure provides improved prosthetic joints for an animal subject. The present disclosure further provides a nucleus supplement device for a spinal disc without violating its annulus fibrosus.
Referring now to
The tip 22 may be partially cylindrical, and is adapted for mating against a superior articular process of an inferior vertebra. It acts as a spacer between the superior articular process and an adjacent inferior articular process of a superior vertebra. By providing a spacer between the superior and inferior articular processes, bone grinding is eliminated, and natural spatial relationship is restored. In addition, under this posterior approach, burdens on a disc will be better shared by a posterior column of the vertebrae. As a result, the disc will become less overburdened, and its degeneration will be slowed.
Portions 18 and 28 of the tip 22 may be tapered or otherwise modified to articulate against cartilage of the vertebrae, so that during movements, the tip 22 will maintain its proper position. It is contemplated that the tip 22 may comprise a variety of shapes, such as a cylinder, sphere, partial sphere, partial cone, or partial pyramid. It is also contemplated that the tip 22 may comprise any suitable biocompatible material, such as, but without limitation, metal, plastics, ceramics, polymers, carbon fiber, shape memory alloys, composites, allograft or porous material.
The body 24 may be substantially cylindrical. Its surface 32 is uneven, and may be created by threading, roughening, or machining, so that the body 24 may engage a hole in the superior vertebra. In this illustration, the surface 32 is threaded, and the threads are substantially even. It is also contemplated that the threads may be uneven. It is further contemplated that the surface 32 may be modified in other ways to engage the superior vertebra.
The body 24 may comprise any suitable biocompatible material, such as, but without limitation, metal, plastics, ceramics, polymers, carbon fiber, shape memory alloys, composites, allograft or porous material. It may be adapted for osseo-integration to facilitate its bonding with the superior vertebra. For example, it may comprise a hydroxyapatite or collagen coating. In another example, it may comprise carbon fiber or biomimetic bone, or may be anodized.
The opening 26 may comprise any shape, such as a hexagon or cross, to allow any suitable tool or instrument (not shown), which may be a screw driver, to drive the prosthetic joint 20.
In one embodiment, the prosthetic joint 20 is created from a single object, which comprises any suitable biocompatible material, such as stainless steel, polymers, carbon fiber, shape memory alloys, or porous material. The opening 26 may be produced by cutting off unwanted portions of the single object. As a result, movement of the tip 22 relative to the body 24 may be constrained, and the wear and tear of the contact surface between the tip 22 and the body 24 may be limited. It is also contemplated that the tip 22 and the body 24 may be created from separate objects. It is contemplated that an allograft plug with a demineralized tip may be used to form the prosthetic joint 20.
Utilization of the present disclosure will now be briefly described. It will be understood that access to a facet joint space and vertebrae preparation are known in the art and will be described only briefly herein. It will also be understood that a medial/dorsal approach is known in the art, and will not be described in details herein. Referring now to
It is contemplated that other approaches, such as a lateral approach, bilateral approach, and optionally, with visualization approach may also be utilized to insert the prosthetic joint.
Insertion preparation may be tailored to the condition of a diseased joint. For example, all or a part of cartilage may be removed. Alternatively, cartilage may simply be left for mating against a prosthetic joint. In one embodiment, insertion preparation may comprise drilling the hole 62 in the superior vertebra V1, and removing materials from the vertebrae V1 and V2 for mating against the tip 22 of the prosthetic joint 20. The hole 62 may be threaded, roughened or machined in its surface to engage the surface 32 of the prosthetic joint 20. It is also contemplated that the tip 22 may be adapted to an existing superior articular process of the inferior vertebra V2, so that preparation of the inferior vertebra V2 may be limited.
In one embodiment, a portion of the superior articular process of the inferior vertebra V2 has been prepared to create a partial cylindrical area to receive the partially cylindrical tip 22, so that the tip 22 will substantially abut the prepared inferior vertebra V2.
In another embodiment, the prepared portion of the superior articular process of the inferior vertebra V2 may be limited to the area necessary to receive the prosthetic joint 20, and the rest of the superior articular process remains unprepared. The unprepared portions of the superior articular process may engage the tip 22 to resist expulsion of the prosthetic joint 20 from its proper position.
Referring now to
Referring now to
The tip 34 is otherwise partially cylindrical, but interrupted by the cavity 36. It includes tapered portions 44 and 46, which may be adapted for mating against cartilage of vertebrae. The tapered portions 44 and 46 may also ease the insertion of the prosthetic joint 30 into an animal body.
The cavity 36 may be used for delivering a substance, which may comprise any suitable biocompatible substance, such as hydrogel, silicone, polyurethane, collagen, or bone morphogenic protein into an articular capsule and/or joint space. The cavity 36 may reside inside the body 38, and has a length L1 that may extend the entire combined lengths of the body 38 and the tip 34. Prior to implanting the prosthetic joint 30, the cavity 36 may be loaded with a rod 48, which may extend a length L2. The length L2 may be smaller than or equal to the length L1. It is contemplated that the rod 48 may comprise any suitable biocompatible materials, such as hydrogel, silicone, polyurethane, collagen, allograft cartilage, or other natural or synthetic materials. A conventional driver device 52, which may be a set screw, may be used to advance the rod 48 to force hydrogel into an articular capsule and/or a joint space.
In another embodiment, the outer surface of the rod 48 may be roughened, machined, or threaded along its entire length L2. Likewise, a surface of the cavity 36 may be roughed, machined, or threaded to engage the rod 48.
Utilization of the prosthetic joint 30 will now be briefly described. In one embodiment, the prosthetic joint 30 may be loaded into a delivery tube or sleeve, and then placed adjacent to a hole in a superior vertebra. It may be inserted through the hole, and advanced until its tapered portions 44 and 46 mate against cartilage of vertebrae. At that point, a conventional tool, which may be a screw driver, may be used with the driver device 52 to advance the rod 48 toward the tip 34, forcing a portion of the rod 48 into an articular capsule. The rod 48 may be advanced until it contacts the articular capsule, or further than the contacting point, so that the rod 48 pushes against the articular capsule. After the hydrogel settles into the articular capsule, it will grow in size and pressurize the articular capsule. Thereafter, the screw driver and the driver device 52 may be removed from the animal body. Alternatively, they may be left inside the animal body. In that case, each of them may comprise a suitable biocompatible material, which may be stainless steel or carbon fiber.
The hydrogel in the articular capsule and/or joint space may function as a spacer between an inferior articular process of a superior vertebra and a superior articular process of an inferior vertebra. It may pressurize an articular capsule, and provide articulation. As a result, bone-on-bone grinding of the adjacent facets may be eliminated. After a certain period of time, which may be six months, one year, or based on clinical diagnosis, the hydrogel may creep into other areas, or deform severely. At that point, the driver device 52 may be advanced further toward the tip 34, forcing another portion of the rod 48 into the articular capsule to replace the deformed hydrogel. Such procedure may be repeated a plurality of times, if necessary, each time advancing an additional portion of the rod 48 into the articular capsule.
Insertion preparation may be made by drilling the hole in the superior vertebra and removing materials from the vertebrae for mating against the tip 34 of the prosthetic joint 30. Further, the hole may be threaded along its surface to engage the roughened surface of the prosthetic joint 30. It is contemplated that the tip 34 may be adapted to an existing superior articular process of the inferior vertebra, so that the preparation for the inferior vertebra may be limited.
In one embodiment, a portion of the superior articular process of the inferior vertebra has been prepared to create a partial cylindrical area to receive the tapered potions 44 and 46, so they may substantially abut the prepared inferior vertebra.
In another embodiment, the prepared portion of the superior articular process of the inferior vertebra may be limited to the area necessary to receive the prosthetic joint 30, and the rest of the superior articular process remains unprepared. The unprepared portions of the superior articular process may engage the tip 34 to resist expulsion of the prosthetic joint 30 from its proper position.
The rod 48 may be advanced into an articular capsule and/or joint space through many means. For example, it can be advanced via any conventional mechanical means, which may employ a biocompatible screw driver (not shown). The screw driver may be left inside an animal subject between treatments. Alternatively, it may be inserted each time to further advance the rod 48 into the articular capsule and/or joint space.
In another embodiment, non-invasive methods may be employed to advance the rod 48. In one example, an infusion pump is utilized. Upon receiving an external signal, which may be a radio frequency signal or an ultrasound excitation, the infusion pump will advance the rod 48 by conventional means, such as an electronic motor or a pressure system. It will be understood that the infusion pump is known in the art, and will not be described further herein.
Referring generally to
In another embodiment, an infusion pump, which is connected through a valve to an osmotic balloon, may be combined with the osmotic balloon to drive the rod 48 into an articular capsule. As the infusion pump receives a control signal, it may release additional osmotically active electrolyte into the balloon, resulting in an increased pressure. The increased pressure may drive the rod 48 further into an articular capsule, so that the pressures on both sides of the osmotic balloon may be equalized. The infusion pump may be made of any biocompatible material, and may be left inside an animal body between repeated advancements of the rod 48.
Referring now to
To provide sufficient volume of hydrogel for the disc 74, it is contemplated that the prosthetic device 50 may be replicated, and a plurality of the prosthetic device 50 may be used to repressurize the nucleus pulposus of the disc 74.
Similar to the descriptions with respect to the rod 48, the rod 72 may be advanced into the disc space 68 through many methods. In one embodiment, non-invasive methods may be employed to advance the rod 72. For example, an infusion pump may be utilized. Upon receiving an external signal, such as a radio frequency signal or an ultrasound excitation, the infusion pump may advance the rod 72 by any conventional means, such as an electronic motor or a pressure system. In another example, a combination of an infusion pump and an osmotic balloon may be utilized to advance the rod 72.
Referring now to
Although only a few exemplary embodiments of this invention have been described in details above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. For example, prosthetic joints disclosed herein may be utilized in combination with disc replacement(s). Also, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. Accordingly, all such modifications are intended to be included within the scope of this invention.
