Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2002-06-28
2003-09-30
Robert, Eduardo C. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S070000, C606S071000, C606S075000
Reexamination Certificate
active
06626909
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for spine fixation, and more particularly to a spine fixation assembly utilizing plates.
BACKGROUND OF THE INVENTION
The human spine
29
comprises individual vertebrae
30
that interlock with each other to form a spinal column, shown in FIG.
1
A. Referring to
FIGS. 1B and 1C
, each vertebra
30
has a cylindrical bony body (vertebral body)
32
, three winglike projections (two transverse processes
33
,
35
and one spinous process
34
), and a bony arch (neural arch)
36
. The bodies of the vertebrae
32
are stacked one on top of the other and form the strong but flexible spinal column. The neural arches
36
are positioned so that the space they enclose forms a tube, i.e., the spinal canal
37
. The spinal canal
37
houses and protects the spinal cord and other neural elements. A fluid filled protective membrane, the dura
38
, covers the contents of the spinal canal. The spinal column is flexible enough to allow the body to twist and bend, but sturdy enough to support and protect the spinal cord and the other neural elements.
The vertebrae
30
are separated and cushioned by thin pads of tough, resilient fiber known as inter-vertebral discs
40
. Inter-vertebral discs
40
provide flexibility to the spine and act as shock absorbers during activity. There is a small opening (foramen)
42
between each vertebra
30
, through which nerves
44
pass and go to different body parts. When the vertebrae are properly aligned the nerves
44
pass through without a problem. However, when the vertebrae are misaligned or a constriction
45
is formed in the spinal canal, the nerves get compressed
44
a
and may cause back pain, leg pain or other neurological disorders. Disorders of the spine that may cause misalignment of the vertebrae or constriction of the spinal canal include spinal injuries, infections, tumor formation, herniation of the inter-vertebral discs (i.e., slippage or protrusion), arthritic disorders, and scoliosis. In these pathologic circumstances, surgery may be tried to either decompress the neural elements and/or fuse adjacent vertebral segments. Decompression may involve laminectomy, discectomy, or corpectomy. Laminectomy involves the removal of part of the lamina
47
, i.e., the bony roof of the spinal canal. Discectomy involves removal of the inter-vertebral discs
40
. Corpectomy involves removal of the vertebral body
32
as well as the adjacent disc spaces
40
. Laminectomy and corpectomy result in central exposure of the dura
38
and its contents. An exposed dura
38
puts the neural elements and spinal cord at risk from direct mechanical injury or scarring from overlying soft tissues. After laminectomy and corpectomy the surgeon needs to stabilize the spine with a fusion. Fusion involves the fixation of two or more vertebrae. Fusion works well because it stops pain due to movement of the intervertebral discs
40
or facets
46
, immobilizes the spine, and prevents instability and or deformity of the spine after laminectomy or corpectomy. Finally a bone graft (
202
shown in FIG.
6
), i.e., a solid piece of bone (1-2 inches) or bone chips, is inserted between laterally adjacent transverse processes and/or pars.
Several spinal fixation systems exist for stabilizing the spine so that bony fusion is achieved. The majority of these fixation systems use either plates or rods that attach to screws inserted into the vertebral body or the pedicles
48
, shown in FIG.
1
C. Plate fixation systems are more commonly used in the anterior part of the spine, i.e., vertebral bodies, while rods are the accepted standard for posterior fixation. In some cases plate fixation systems are also used to fuse two adjacent vertebral segments. This construction usually consists of two longitudinal plates that are each placed laterally to connect two adjacent pedicles of the segments to be fused. This system can be extended along the sides of the spine by connecting two adjacent pedicles at a time similar to the concept of a bicycle chain. Current plate fixation systems are basically designed to function in place of rods with the advantage of allowing intersegmental fixation without the need to contour a long rod across multiple segments.
Single or multilevel segmental posterior fusions are most commonly achieved by contouring a solid ¼inch cylindrical rod and attaching it to adjacent pedicle screws on each side of the spine using various connecting assemblies. This longitudinal construction can be made more rigid by connecting the rods to each other to form an “H” configuration.
The rod system requires contouring of each rod across several vertebras in many cases. The contouring of each rod depends on the configuration of the pedicle screws and varies from side to side in the same patient and among patients. This may add considerable time to an operation. Recent generations of pedicle screws and rod connectors seek to diminish this drawback by allowing variable axes of movements in the pedicle screw recess for the rod or in the rod connectors. However, in most cases this adds another level of complexity to the operation and often further increases the operative time. This increase in operative time and the complexity of the connectors put substantial stress on the surgeon and the supporting staff. Even in the hands of the best spine surgeon, the rod is often not perfectly contoured to align with the pedicle screws. Hence the surgeon has to use substantial force at multiple points along a rod to hold the rod to the screws or connectors while counteracting the adjacent soft tissues. This maneuver risks soft tissue damage and also puts the dura and the neural contents at risk for dural tears or spinal cord or nerve damage if a holding instrument slips. The added bulk of the rods and connectors along the lateral aspect of the spine limits access to the pars and transverse processes for decortication and placement of bone graft. Some of the current plating systems have the same limited access to the pars and/or transverse processes. In order to avoid this limitation many surgeons decorticate before placing the rods, thereby increasing the amount of blood loss and making it more difficult to maintain a clear operative field. Placing rods or plates lateral to the spine leaves the center of the spinal canal that contains the dura, spinal cords and nerves completely exposed. In situations where problems develop at the junction above or below the fused segments necessitating additional fusion, the rod fixation system is difficult to extend to higher or lower levels that need to be fused. Although there are connectors and techniques to lengthen the fixation, they tend to be difficult to use and time consuming.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention features a spine fixation assembly connecting a first and second vertebra. The spine fixation assembly includes a first elongated plate having a first and second end and a second elongated plate having a first and second end. The first and second ends of the first plate are adapted to be attached to a first location of the first vertebra and to a second location of the second vertebra, respectively. The first and second ends of the second plate are adapted to be attached to a second location of the first vertebra and to a first location of the second vertebra, respectively. The first and second elongated plates form an X-shaped structure and may be cross-coupled. The locations where the ends of the plates may be attached include a pedicle, transverse processes, pars, lamina, vertebral body, sacrum, lateral mass, and occiput.
Implementations of this aspect of the invention may include one or more of the following features. The first and second elongated plates are cross-coupled and attached to each other via a screw. The spine fixation assembly may further include a third elongated plate having a first and second end. The first and second ends of the third plate are adapted to be attached to the first and second locations of the fi
AKC Patents
Collins Aliki K.
Ramana Anuradha
Robert Eduardo C.
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