Surgery – Instruments – Orthopedic instrumentation
Reissue Patent
2001-01-30
2002-04-16
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S075000
Reissue Patent
active
RE037665
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a polyaxial screw and coupling apparatus for use with orthopedic fixation systems. More particularly, the present invention relates to a screw for insertion into spinal bone, and a coupling element polyaxially mounted thereto, via a two-piece interlocking coupling element having a socket portion and a threaded compression member, for coupling the screw to an orthopedic implantation structure, such as a rod, therein enhancing the efficacy of the implant assembly by providing freedom of angulation among the rod, screw and coupling element.
2. Description of the Prior Art
The bones and connective tissue of an adult human spinal column consists of more than 20 discrete bones coupled sequentially to one another by a tri-joint complex which consist of an anterior disc and the two posterior facet joints, the anterior discs of adjacent bones being cushioned by cartilage spacers referred to as intervertebral discs. These more than 20 bones are anatomically categorized as being members of one of four classifications: cervical, thoracic, lumbar, or sacral. The cervical portion of the spine, which comprises the top of the spine, up to the base of the skull, includes the first 7 vertebrae. The intermediate 12 bones are the thoracic vertebrae, and connect to the lower spine comprising the 5 lumbar vertebrae. The base of the spine is the sacral bones (including the coccyx). The component bones of the cervical spine are generally smaller than those of the thoracic and lumbar spine. For the purposes of this disclosure, however, the word spine shall refer only to the cervical region.
Referring now to
FIGS. 1
,
2
, and
3
, top, side, and posterior views of a vertebral body, a pair of adjacent vertebral bodies, and a sequence of vertebral bodies are shown, respectively. The spinal cord is housed in the central canal
10
, protected from the posterior side by a shell of bone called the lamina
12
. The lamina
12
includes a rearwardly and downwardly extending portion called the spinous process
16
, and laterally extending structures which are referred to as the transverse processes
14
. The anterior portion of the spine comprises a set of generally cylindrically shaped bones which are stacked one on top of the other. These portions of the vertebrae are referred to as the vertebral bodies
20
, and are each separated from the other by the intervertebral discs
22
. The pedicles
24
comprise bone bridges which couple the anterior vertebral body
20
to the corresponding lamina
12
.
The spinal column of bones is highly complex in that it includes over twenty bones coupled to one another, housing and protecting critical elements of the nervous system having innumerable peripheral nerves and circulatory bodies in close proximity. In spite of these complexities, the spine is a highly flexible structure, capable of a high degree of curvature and twist in nearly every direction. Genetic or developmental irregularities, trauma, chronic stress, tumors, and disease, however, can result in spinal pathologies which either limit this range of motion, or which threaten the critical elements of the nervous system housed within the spinal column. A variety of systems have been disclosed in the art which achieve this immobilization by implanting artificial assemblies in or on the spinal column. These assemblies may be classified as anterior, posterior, or lateral implants. As the classifications suggest, lateral and anterior assemblies are coupled to the anterior portion of the spine, which is the sequence of vertebral bodies. Posterior implants generally comprise pairs of rods, which are aligned along the axis which the bones are to be disposed, and which are then attached to the spinal column by either hooks which couple to the lamina or attach to the transverse processes, or by screws which are inserted through the pedicles.
“Rod assemblies” generally comprise a plurality of such screws which are implanted through the posterior lateral surfaces of the laminae, through the pedicles, and into their respective vertebral bodies. The screws are provided with upper portions which comprise coupling elements, for receiving and securing an elongate rod therethrough. The rod extends along the axis of the spine, coupling to the plurality of screws via their coupling elements. The rigidity of the rod may be utilized to align the spine in conformance with a more desired shape.
It has been identified, however, that a considerable difficulty is associated with inserting screws along a misaligned curvature and simultaneously exactly positioning the coupling elements such that the rod receiving portions thereof are aligned so that the rod can be passed therethrough without distorting the screws. Attempts at achieving proper alignment with fixed screws is understood to require increased operating time, which is known to enhance many complications associated with surgery. Often surgical efforts with such fixed axes devices cannot be achieved, thereby rendering such instrumentation attempts entirely unsucessful.
The art contains a variety of attempts at providing instrumentation which permit a limited freedom with respect to angulation of the screw and the coupling element. These teachings, however, are generally complex, inadequately reliable, and lack long-term durability. These considerable drawbacks associated with prior art systems also include difficulty properly positioned the rod and coupling elements, and the tedious manipulation of the many small parts in the operative environment.
It is, therefore, the principal object of the present invention to provide a pedicle screw and coupling element assembly which provides a polyaxial freedom of implantation angulation with respect to rod reception.
In addition, it is an object of the present invention to provide such an assembly which comprises a reduced number of elements, and which correspondingly provides for expeditious implantation.
Accordingly it is also an object of the present invention to provide an assembly which is reliable, durable, and provides long term fixation support.
Other objects of the present invention not explicitly stated will be set forth and will be more clearly understood in conjunction with the descriptions of the preferred embodiments disclosed hereafter.
SUMMARY OF THE INVENTION
The preceding objects of the invention are achieved by the present invention which is a polyaxial locking screw and coupling element for use with rod stabilization and immobilization systems in the spine. More particularly, the polyaxial screw and coupling element assembly of the present invention comprises a bone screw having a head which is curvate in shape, for example semi-spherical, and a two-piece interlocking coupling element mounted thereto. This combination is mounted inside the bottom of an internal channel of a cylindrical body member.
More specifically, with respect to the cylindrical body member, the tubular body comprises a rod receiving channel formed in the upper portion thereof, with a threading formed on the remaining upper elements so that a rod securing nut and/or set screw may be threaded thereon once a rod has been placed in the channel. The body further includes an axial bore which includes extends from the rod receiving channel through to the bottom of the cylinder. The portion of the axial bore which is below the channel forms a receiving chamber, the upper portion thereof having a constant diameter, and the lower portion of the chamber being inwardly tapered. The inner surface of the upper portion of the chamber and/or the inner surface of the portion of the axial bore which is above the chamber may further include a threading.
The two-piece interlocking coupling element comprises and socket portion and a cap portion. The socket portion is designed with an interior semi-spherical volume, so that it may receive the semi-spherical head of a corresponding bone screw. The interior volume of the socket portion is open at both axial ends thereof. The exterior
Ralph James D.
Tatar Stephen
Fastenetix LLC
Morrison & Foerster / LLP
Reip David O.
LandOfFree
Polyaxial pedicle screw having a threaded and tapered... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyaxial pedicle screw having a threaded and tapered..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyaxial pedicle screw having a threaded and tapered... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2829437