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Methods and apparatus for intervertebral disc prosthesis

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Methods and apparatus for intervertebral disc prosthesis


A method for inserting an intervertebral disc prosthesis into a space between two vertebrae involves inserting the prosthesis partway into the space under constraint to prevent endplates of the prosthesis from articulating, releasing the prosthesis from constraint, and inserting the unconstrained prosthesis farther into the space. In some embodiments, the method involves grasping the prosthesis with a grasping device to insert the prosthesis partway under constraint, loosing the grasping device to release the prosthesis from constraint, and pushing the prosthesis farther into the disc space using the grasping device and/or one or more separate pusher devices. A system includes a grasping device, at least one separate pushing device, and optionally a vertebral spreading device and/or a vertebral midline indicator device.
Related Terms: Prosthesis Vertebra Vertebrae Intervertebral Disc

Browse recent Spinalmotion, Inc. patents - Mountain View, CA, US
Inventors: Malan de Villiers, Ulrich Hahnle, David Hovda
USPTO Applicaton #: #20130013073 - Class: 623 1716 (USPTO) - 01/10/13 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Implantable Prosthesis >Bone >Spine Bone >Including Spinal Disc Spacer Between Adjacent Spine Bones

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The Patent Description & Claims data below is from USPTO Patent Application 20130013073, Methods and apparatus for intervertebral disc prosthesis.

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CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent application Ser. No. 12/044,175 (Attorney Docket No. 29850-706.402), filed Mar. 7, 2008, which is a divisional of U.S. patent application Ser. No. 10/913,780 (Attorney Docket No. 29850-706.201), filed Aug. 6, 2004, the full disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to medical devices and methods. More specifically, the invention relates to intervertebral disc prostheses.

Back pain takes an enormous toll on the health and productivity of people around the world. According to the American Academy of Orthopedic Surgeons, approximately 80 percent of Americans will experience back pain at some time in their life. In just the year 2000, approximately 26 million visits were made to physicians\' offices due to back problems in the United States. On any one day, it is estimated that 5% of the working population in America is disabled by back pain.

One common cause of back pain is injury, degeneration and/or dysfunction of one or more intervertebral discs. Intervertebral discs are the soft tissue structures located between each of the thirty-three vertebral bones that make up the vertebral (spinal) column. Essentially, the discs allow the vertebrae to move relative to one another. The vertebral column and discs are vital anatomical structures, in that they form a central axis that supports the head and torso, allow for movement of the back, and protect the spinal cord, which passes through the vertebrae in proximity to the discs.

Discs often become damaged due to wear and tear or acute injury. For example, discs may bulge (herniate), tear, rupture, degenerate or the like. A bulging disc may press against the spinal cord or a nerve exiting the spinal cord, causing “radicular” pain (pain in one or more extremities caused by impingement of a nerve root). Degeneration or other damage to a disc may cause a loss of “disc height,” meaning that the natural space between two vertebrae decreases. Decreased disc height may cause a disc to bulge, facet loads to increase, two vertebrae to rub together in an unnatural way and/or increased pressure on certain parts of the vertebrae and/or nerve roots, thus causing pain. In general, chronic and acute damage to intervertebral discs is a common source of back related pain and loss of mobility.

When one or more damaged intervertebral discs cause a patient pain and discomfort, surgery is often required. Traditionally, surgical procedures for treating intervertebral discs have involved discectomy (partial or total removal of a disc), with or without fusion of the two vertebrae adjacent to the disc. Fusion of the two vertebrae is achieved by inserting bone graft material between the two vertebrae such that the two vertebrae and the graft material grow together. Oftentimes, pins, rods, screws, cages and/or the like are inserted between the vertebrae to act as support structures to hold the vertebrae and graft material in place while they permanently fuse together. Although fusion often treats the back pain, it reduces the patient\'s ability to move, because the back cannot bend or twist at the fused area. In addition, fusion increases stresses at adjacent levels of the spine, potentially accelerating degeneration of these discs.

In an attempt to treat disc related pain without fusion, an alternative approach has been developed, in which a movable, implantable, artificial intervertebral disc (or “disc prosthesis”) is inserted between two vertebrae. A number of different intervertebral disc prostheses are currently being developed. For example, the inventors of the present invention have developed disc prostheses described in U.S. patent application Ser. Nos. 10/855,817 and 10/855,253, previously incorporated by reference. Other examples of intervertebral disc prostheses are the LINK™ SB CHARITTE™ disc prosthesis (provided by DePuy Spine, Inc.) MOBIDISK™ disc prosthesis (provided by LDR Medical), the BRYAN™ cervical disc prosthesis (provided by Medtronic Sofamor Danek, Inc.), the PRODISC™ disc prosthesis or PRODISC-C™ disc prosthesis (from Synthes Stratec, Inc.), and the PCM™ disc prosthesis (provided by Cervitech, Inc.).

To insert an artificial intervertebral disc prosthesis, and indeed for performing most disc-related surgeries, it is typically necessary to gain access to the disc and the intervertebral space from an anterior to posterior direction (i.e., through the front of the patient), to avoid coming in contact with the spinal cord. Thus, surgical procedures on a disc are typically approached anteriorly through the neck or abdomen, depending on which disc (or discs) is being repaired. Methods for inserting a disc prosthesis generally involve removing the damaged disc, preparing the surfaces of the two vertebral bones to receive the prosthesis, spreading the two vertebrae apart using one or more spreading devices, and inserting the prosthesis into the space between the two vertebrae. Examples of such methods are described in U.S. Pat. Nos. 6,478,800, 6,235,030, 6,652,533, 6,689,132, 6,261,296 and 6,666,866, and in U.S. Patent Application Nos. 2001/0031969, 2001/0029377, 2003/0153916, 2002/0198532, 2004/0024407, 2003/0216737, 2003/0204261, 2003/0135220 and 2003/0014114. Due to the invasive nature of such procedures, one important goal is to reduce invasiveness, thus causing as little trauma to tissues surrounding the surgical site as possible.

The main drawback of currently available methods for inserting intervertebral disc prostheses is that they require a larger amount of spreading apart (or “distraction”) of the two vertebrae than is optimal. Over-distraction is necessary when using such methods because it is important to insert the disc prosthesis all the way into the disc space, to position the center of rotation of the prosthesis closer to the posterior portion of the vertebrae than to the anterior portion. This allows the vertebrae to move as they were intended and avoids placing undue strain on the facet joints of the vertebrae or on other structures. To push a prosthesis toward the back of a disc space, however, it is typically necessary to spread the two vertebrae apart widely, since the anterior portion of the disc space is usually wider (or higher) than the posterior portion. In some methods, an artificial disc is placed by placing a first endplate into the space, placing a second endplate into the space, and then spreading the vertebrae wide enough to wedge a core in between the two endplates. In other methods, the vertebrae are spread apart as far as practicable, the whole prosthesis is inserted while one or more spreading devices are in place, and not until the prosthesis is completely inserted is the spreading device removed. In either case, as well as in other currently available methods, the two vertebrae adjacent the prosthesis are typically spread farther apart than would be desirable for a longer amount of time than would be desirable. In some cases, the posterior longitudinal ligament (PLL) is released, or “cut,” to enable sufficient distraction for disc placement.

Distracting vertebrae can damage muscles, ligaments, nerves and/or other tissues in and around the vertebral column. Such damage may actually cause the patient to experience as much, or even more, pain after surgery than was caused by the original disc problem.

Therefore, as the use of intervertebral disc prostheses increases, an increasing need exists for improved methods and apparatus for inserting such prostheses. Ideally, such intervertebral prosthesis insertion methods and devices would provide for insertion of a prosthesis a desired distance into an intervertebral space while reducing the need for intervertebral distraction, thus preventing or at least reducing trauma to surrounding tissues. Also ideally, such insertion methods and devices would be relatively simple and easy to use, thereby reducing the overall invasiveness of the procedure. At least some of these objectives will be met by the present invention.

2. Description of the Background Art.

A number of exemplary intervertebral disc prostheses are listed above. Published US patent applications 2002/0035400A1 and 2002/0128715A1 describe disc implants which comprise opposing plates with a core between them over which the plates can slide. The core receives one or more central posts, which are carried by the plates and which locate in opposite ends of a central opening in the core. Such arrangements limit the load bearing area available between the plates and core.

Other patents related to intervertebral disc prostheses include U.S. Pat. Nos. 4,759,766; 4,863,477; 4,997,432; 5,035,716; 5,071,437; 5,370,697; 5,401,269; 5,507,816; 5,534,030; 5,556,431; 5,674,296; 5,676,702; 5,702,450; 5,824,094; 5,865,846; 5,989,291; 6,001,130; 6,022,376; 6,039,763; 6,139,579; 6,156,067; 6,162,252; 6,315,797; 6,348,071; 6,368,350; 6,416,551; 6,592,624; 6,607,558 and 6,706,068. Other patent applications related to intervertebral disc prostheses include U.S. Patent Application Publication Nos.: 2003/0009224; 2003/0074076; 2003/0191536; 2003/0208271; 2003/0135277; 2003/0199982; 2001/0016773 and 2003/0100951. Other related patents include WO 01/01893A1, EP 1344507, EP 1344506, EP 1250898, EP 1306064, EP 1344508, EP 1344493, EP 1417940, EP 1142544, and EP 0333990.

BRIEF

SUMMARY

OF THE INVENTION

The present invention generally provides methods for inserting an intervertebral disc prosthesis, as well as devices and systems for performing the methods. One advantage of these improved methods is that a disc prosthesis may be inserted with minimal or reduced intervertebral distraction, thus avoiding trauma to tissues in and around the insertion site. Reduced distraction is generally achieved by inserting a prosthesis into an intervertebral space while allowing endplates of the prosthesis to articulate during at least part of the insertion process. For the purposes of this application, to “articulate” means to move relative to another structure. Thus, allowing endplates of an intervertebral prosthesis to articulate means that endplates are free to move relative to each other, relative to a core of the prosthesis, relative to a ball and socket joint of the prosthesis, relative to a mobile or fixed center of rotation of the prosthesis and/or the like. Although the following description often focuses on disc prostheses having two endplates and a core, various embodiments of the insertion method may be applied to any other intervertebral disc prosthesis. Articulation of the endplates during insertion allows the prosthesis to be pushed posteriorly into a disc space without excessive intervertebral distraction or significant forces being applied to the vertebrae, thus achieving desirable positioning of the prosthesis while avoiding trauma to surrounding muscles, ligaments, nerves and the like.

In one aspect of the present invention, a method of inserting an intervertebral prosthesis into a space between two adjacent vertebrae involves inserting the prosthesis partway into the space under constraint to prevent endplates of the prosthesis from articulating, releasing the prosthesis from constraint, and inserting the unconstrained prosthesis farther into the space. As mentioned above, in some embodiments, the endplates of the constrained prosthesis are prevented from articulating about a core of the prosthesis, while the endplates of the unconstrained prosthesis are generally free to articulate about the core to help the prosthesis conform to the space between the two vertebrae. In alternative embodiments, the unconstrained endplates may be free to articulate about a ball and socket joint or other structure.

In one embodiment, inserting the prosthesis partway under constraint involves grasping the endplates with an insertion tool such that they cannot move relative to the core and pushing the prosthesis partway into the space using the insertion tool. In such embodiments, releasing the prosthesis from constraint may involve loosening the insertion tool. In some embodiments, the loosened insertion tool may then be used to insert the unconstrained prosthesis farther into the intervertebral space. Additionally, or alternatively, a separate pusher tool may be used to insert the unconstrained prosthesis farther into the space.

In some embodiments, inserting the constrained prosthesis partway into the space between the vertebrae involves inserting the prosthesis less than halfway into the space. In one embodiment, for example, the constrained prosthesis is inserted about one third of the way into the space and then subsequently inserted farther into the space. In alternative embodiments, the constrained prosthesis may be pushed more than halfway into the space, less than one third of the way into the space, or any other suitable distance into the space. The unconstrained prosthesis is then inserted any desired distance farther into the intervertebral space. In some embodiments, for example, the prosthesis is inserted sufficiently far into the space that a center of rotation of the prosthesis is closer to the posterior edges of the vertebrae than to the anterior edges of the vertebrae.

In some embodiments, the prosthesis is inserted in approximately an anterior to posterior direction. In alternative embodiments, the prosthesis may be inserted in an anterolateral-to-posterior direction, lateral-to-lateral direction or posterior-to-anterior direction. Typically, inserting the unconstrained prosthesis farther into the space involves pushing the prosthesis into the space. In other embodiments, however, techniques other than pushing may be used to insert the prosthesis, such as pulling. In some embodiments, pushing the prosthesis farther into the space involves individually pushing upper and lower endplates of the prosthesis. Alternatively, or additionally, the upper and lower endplates of the prosthesis may be simultaneously pushed into the intervertebral space. In various embodiments, individual and simultaneous endplate pushing may be performed using the grasping device, a separate pusher device, or both.

In some embodiments, the method also includes inserting a vertebral spacing device at least partway into the space and manipulating the spacing device to increase a height of the space. An example of such a spacing device is described by the assignees of the present application in PCT Patent Application Number 2004/000171, filed Jan. 26, 2004 (Attorney Docket Number currently being updated with International Bureau to 022031-001100PC), the full disclosure of which is hereby incorporated by reference. The spacing step is typically performed before inserting the constrained prosthesis partway into the intervertebral space. In some embodiments, inserting the constrained prosthesis partway into the intervertebral space comprises sliding the prosthesis between two opposing jaws of the spacing device. In such an embodiment, inserting the constrained prosthesis partway into the space may optionally further involve sliding at least one fin on at least one outer surface of the endplates through at least one corresponding slot in the opposing jaws. In one embodiment, such a fin (or fins) may then be slid into a corresponding slot formed in one of the vertebrae.

Some embodiments also involve using a vertebral midpoint indicator device to locate a midpoint of at least one of the two vertebrae, and marking the midpoint on one or both of the two vertebrae. An example of a midline indicator device is described by the assignees of the present application in PCT Patent Application Number 2004/000170, filed Jan. 26, 2004 (Attorney Docket Number currently being updated with International Bureau to 022031-000900PC), the full disclosure of which is hereby incorporated by reference. Midline finding and marking are typically performed before inserting the constrained prosthesis partway into the intervertebral space. In some embodiments, locating the midpoint involves inserting the vertebral midpoint indicator device into the space between the vertebrae and imaging the midpoint indicator device using a radiographic imaging device.

In another aspect of the present invention, a method of inserting an intervertebral prosthesis into a space between two adjacent vertebrae involves sliding the prosthesis partway into the space between the vertebrae between two opposing jaws of a spacing device, removing the spacing device from the space to release the prosthesis from constraint, and pushing the unconstrained prosthesis farther into the space while allowing endplates of the prosthesis to articulate. In this method, the endplates of the prosthesis are constrained from articulating when the prosthesis is disposed between the jaws. Again, in some embodiments, the unconstrained endplates articulate about a core of the prosthesis, while in alternative embodiments they may articulate about a ball and socket joint or other structure. Such a method may optionally further include inserting the spacing device at least partway into the space and manipulating the spacing device to increase a height of the space. Any of the additional or alternative features described above may also be applied in various embodiments.



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Previous Patent Application:
Intervertebral prosthetic disc
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Osteoimplants and methods for their manufacture
Industry Class:
Prosthesis (i.e., artificial body members), parts thereof, or aids and accessories therefor
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stats Patent Info
Application #
US 20130013073 A1
Publish Date
01/10/2013
Document #
13619352
File Date
09/14/2012
USPTO Class
623 1716
Other USPTO Classes
International Class
61F2/44
Drawings
8


Prosthesis
Vertebra
Vertebrae
Intervertebral Disc


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