Intervertebral disc device employing looped probe

Details Intervertebral disc device employing looped probe Intervertebral disc device employing looped probe

2001-06-06

2004-04-27

Dvorak, Linda C. M. (Department: 3739)

Surgery

Instruments

Electrical application

C606S014000, C606S033000

Reexamination Certificate

active

06726685

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods and apparatuses for accessing and modifying intervertebral disc tissue and more particularly to accessing and modifying intervertebral disc tissue using percutaneous techniques that avoid major surgical intervention.
2. Description of Related Art
Intervertebral disc abnormalities have a high incidence in the population and may result in pain and discomfort if they impinge on or irritate nerves. Disc abnormalities may be the result of trauma, repetitive use, metabolic disorders and the aging process and include such disorders but are not limited to degenerative discs (i) localized tears or fissures in the annulus fibrosus, (ii) localized disc herniations with contained or escaped extrusions, and (iii) chronic, circumferential bulging disc.
Disc fissures occur rather easily after structural degeneration (a part of the aging process that may be accelerated by trauma) of fibrous components of the annulus fibrosus. Sneezing, bending or just attrition can tear these degenerated annulus fibers, creating a fissure. The fissure may or may not be accompanied by extrusion of nucleus pulposus material into or beyond the annulus fibrosus. The fissure itself may be the sole morphological change, above and beyond generalized degenerative changes in the connective tissue of the disc. Even if there is no visible extrusion, biochemicals within the disc may still irritate surrounding structures. Disc fissures can be debilitatingly painful. Initial treatment is symptomatic, including bed rest, pain killers and muscle relaxants. More recently, spinal fusion with cages have been performed when conservative treatment did not relieve the pain. The fissure may also be associated with a herniation of that portion of the annulus.
With a contained disc herniation, there are no free nucleus fragments in the spinal canal. Nevertheless, even a contained disc herniation is problematic because the outward protrusion can press on the spinal nerves or irritate other structures. In addition to nerve root compression, escaped nucleus pulposus contents may chemically irritate neural structures. Current treatment methods include reduction of pressure on the annulus by removing some of the interior nucleus pulposus material by percutaneous nuclectomy. However, complications include disc space infection, nerve root injury, hematoma formation, instability of the adjacent vertebrae and collapse of the disc from decrease in height.
Another disc problem occurs when the disc bulges outward circumferentially in all directions and not just in one location. Over time, the disc weakens and takes on a “roll” shape or circumferential bulge. Mechanical stiffness of the joint is reduced and the joint may become unstable. One vertebra may settle on top of another. This problem continues as the body ages and accounts for shortened stature in old age. With the increasing life expectancy of the population, such degenerative disc disease and impairment of nerve function are becoming major public health problems. As the disc “roll” extends beyond the normal circumference, the disc height may be compromised, foramina with nerve roots are compressed. In addition, osteophytes may form on the outer surface of the disc roll and further encroach on the spinal canal and foramina through which nerves pass. The condition is called lumbar spondylosis.
It has been thought that such disc degeneration creates segmental instability which disturbs sensitive structures which in turn register pain. Traditional, conservative methods of treatment include bed rest, pain medication, physical therapy or steroid injection. Upon failure of conservative therapy, spinal pain (assumed to be due to instability) has been treated by spinal fusion, with or without instrumentation, which causes the vertebrae above and below the disc to grow solidly together and form a single, solid piece of bone. The procedure is carried out with or without discectomy. Other treatment include discectomy alone or disc decompression with or without fusion. Nuclectomy can be performed by removing some of the nucleus to reduce pressure on the annulus. However, complications include disc space infection, nerve root injury, hematoma formation, and instability of adjacent vertebrae.
These interventions have been problematic in that alleviation of back pain is unpredictable even if surgery appears successful. In attempts to overcome these difficulties, new fixation devices have been introduced to the market, including but not limited to pedicle screws and interbody fusion cages. Although pedicle screws provide a high fusion success rate, there is still no direct correlation between fusion success and patient improvement in function and pain. Studies on fusion have demonstrated success rate of between 50% and 67% for pain improvement, and a significant number of patients have more pain postoperatively. Therefore, different methods of helping patients with degenerative disc problems need to be explored.
One of the challenges associated with treating intervertebral discs is accessing them via percutaneous methods. To appreciate the difficulty presented, the anatomical structure of the spine and an intervertebral disc is illustrated and described below.
FIGS. 1A and 1B
illustrate a cross-sectional anatomical view of a vertebra and associated disc and a lateral view of a portion of a lumbar and thoracic spine, respectively. Structures of a typical cervical vertebra (superior aspect) are shown in FIG.
1
A:
104
—lamina;
106
—spinal cord;
108
—dorsal root of spinal nerve;
114
—ventral root of spinal nerve;
115
—posterior longitudinal ligament;
118
—intervertebral disc;
120
—nucleus pulposus;
122
—annulus fibrosus;
124
—anterior longitudinal ligament;
126
—vertebral body;
128
—pedicle;
130
—vertebral artery;
132
—vertebral veins;
134
—superior articular facet;
136
—posterial lateral portion of the annulus;
138
—posterior medial portion of the annulus; and
142
—spinous process. In
FIG. 1A
, one side of the intervertebral disc
118
is not shown so that the anterior vertebral body
126
can be seen.
FIG. 1B
is a lateral aspect of the lower portion of a typical spinal column showing the entire lumbar region and part of the thoracic region and displaying the following structures:
162
—intervertebral disc;
142
—spinous process;
168
—inferior articular process;
170
—inferior vertebral notch;
174
—superior articular process;
176
—lumbar curvature; and
180
—sacrum.
The presence of the spinal cord and the posterior portion of the vertebral body, including the spinous process, and superior and inferior articular processes, prohibit introduction of a needle or trocar from a directly posterior position. This is important because the posterior disc wall is the site of symptomatic annulus tears and disc protrusions/extrusions that compress or irritate spinal nerves for most degenerative disc syndromes.
FIG. 1C
provides a posterior-lateral anatomical view of two lumbar vertebrae and illustration of the triangular working zone. The inferior articular process
168
, along with the pedicle
128
and the lumbar spinal nerve
110
, form a small “triangular” window through which introduction of an instrument can be achieved from the posterior lateral approach.
FIG. 1D
illustrates an instrument (an introducer
169
) introduced into an intervertebral disc by the posterior lateral approach.
FIG. 1E
illustrates the anatomy of an intervertebral disc in greater detail and shows an introducer
169
inserted into the disc. Structures of the disc are identified and described by these anatomical designations: the posterior lateral inner annulus
136
, posterior medial inner annulus
138
, annulus fibrosus
122

ucleus pulposus
120
interface, the annulus/dural interface
146
, annulus/posterior longitudinal ligament interface
148
, anterior lateral inner annulus
150
, and the anterior medial inner annulus
152
.
The annulus fibrosus
122
is comprised primarily of tough fibrous material, while the nucleus pu

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