Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-02-15
2002-09-17
Robert, Eduardo C. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06451021
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to screws and coupling element assemblies for use with orthopedic fixation systems. More particularly, the invention relates to a screw and coupling element assembly, for use with an orthopedic rod implantation apparatus, that includes a locking element that simultaneously locks a head of the screw within a seat of the coupling element so that a shaft of the screw is fixed at an angle relative to the coupling element and a rod, of the orthopedic rod implantation apparatus, disposed within a rod-receiving channel of the locking element is fixed relative to the coupling element.
BACKGROUND OF THE INVENTION
The bones and connective tissue of an adult human spinal column consists of more than twenty 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 twenty 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 seven vertebrae. The intermediate twelve bones are the thoracic vertebrae, and connect to the lower spine comprising the five 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.
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 unsuccessful.
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 in properly positioning the rod and coupling elements, and the tedious manipulation of the many parts that are used in the prior art to lock the rod, the screw, and the coupling element in position once they are properly positioned. It is not unusual for displacement to occur as these parts are manipulated to lock the elements, which is clinically unacceptable, and repeated attempts at locking the elements in proper position must be made to remedy this displacement.
There is, therefore, a need for a screw and coupling element assembly which provides a polyaxial freedom of implantation angulation with respect to rod reception. There is also a need for such an assembly which comprises a reduced number of elements, and which correspondingly provides for expeditious implantation. There is also a need for such an assembly that provides reduced difficulty in locking steps to prevent unwanted displacement of the elements prior to locking. There is also a need for an assembly which is reliable, durable, and provides long term fixation support.
SUMMARY OF THE INVENTION
The invention provides a screw and coupling element assembly for use with an orthopedic rod implantation apparatus. The assembly includes a securing element such as, for example, a screw, that has a head and a shaft that extends from the head. Preferably, the head has an engagement surface that can be engaged by a screwdriving tool. Preferably, the head also has a curvate proximal portion from which the shaft extends.
The screw and coupling element assembly further includes a coupling element and a locking element. The coupling element has a seat within which the head of the screw can be seated such that the shaft of the screw protrudes from the coupling element. The locking element can be mated with the coupling element and thereafter can be selectively moved through a plurality of positions including an unlocked position and a locked position. When the locking element is in the unlocked position, the locking element presents a rod-receiving channel and the head of the screw is movable in the seat of the coupling element, such that the shaft of the screw can be directed in a plurality of angles relative to the coupling element. When the locking element is in the locked position, a rod disposed within the rod-receiving channel is fixed relative to the coupling element, and the head of the screw is immovable in the seat of the coupling element, such that the shaft of the screw is fixed at an angle relative to the coupling element. More particularly, when the locking element is in the locked position, the locking element is compression locked within the coupling element, the head of the screw is compress
Ralph James D.
Tatar Stephen
Bortree Timothy J.
Errico Joseph P.
Robert Eduardo C.
Third Millennium Engineering LLC
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