General Disc Degeneration
Introduction 
Discs are the cartilage that lies between the bony vertebral bodies
of the spine.
Since motion occurs in this area, these are considered a joint.
As a natural phenomenon of the aging process, discs lose their water
content and degenerate. Concurrently, tears occur in the outer lining
of the disc (the annulus).
In adults, the annulus has nerve fibers while the center of a disc
does not. A tear in this outer annulus can be quite painful. Although
these degenerative processes are part of the natural aging of the
spine, the discs of some people degenerate much more quickly than
others. Also, for reasons as yet unknown, some individuals experience
much more pain from these degenerative changes than others (See
section under imaging studies about results of MRI).
The symptoms of DDD typically follow one of three courses:
- a significant injury followed by sudden and unexpected back
pain;
- a trivial injury accompanied by significant back pain; and
- a gradual onset and worsening of midline low back pain;
What treatment options are available for degenerative disc disease?
Surgical
Artificial Disc Replacement
  Dr. Regan performs ADR procedures and previously preformed them as part of an Federal
Drug Administration clinical trial. When performing artificial
disc replacement (ADR) for degenerative disc disease, the doctor
inserts a small prosthetic (artificial) disc comprising a polyethylene
core that slides between two metal end plates. The end plates
are attached to the vertebral body with anchoring teeth built
along the rim of the end plates.
The prosthetic discs replace the injured discs, helping to relieve
chronic back pain. The polyethylene core allows movement of the
spine, unlike fusions which prevent normal movement.
The disc is made of the same material used in artificial hips and
knees.
BMP
Pinpointed bone growth and formation is vital to the supporting
structures of the spine. Bone morphogenic protein (BMP) is a substance
that stimulates bone growth and can be based on and matched to properly
identified material from the patient. Material such as BMP can be
used to produce a spinal fusion without the additional pain of using
the patient's own bone for this purpose. BMP can be implanted to
allow support for the structure of the spine in a way that bone
grafts have difficulty doing. BMP relies on the patient's own genetic
makeup to provide safe, effective bone growth for the patient.
Replacement of nucleus pulposus
If you imagine the disk as a jelly doughnut, the annulus fibrosis
(a ring of cartilage between the vertebrae) is the doughnut and
the nucleus pulposus (a gel-like material inside the annulus) is
the jelly. If you have a herniated disk, it's as if the jelly is
squeezed out of the doughnut. Research is currently underway to
create an artificial replacement materials, such as hydrogels and
various polymers, for the nucleus pulposus when all or part of it
is removed. The objective of implanting replacement material is
to maintain or restore the physiologic (normal functional) height
of the intervertebral disc space, as well as the mobility and the
mechanical function of the spine.
Repair of annulus fibrosis
 Minimally
invasive surgery is available for annular tears. Microdiscectomy
is a procedure in which a small incision is made in the back
and part of the nucleus that is putting pressure on the nerve
is removed. Annular tears can also be treated with intradiscal
electrothermal therapy (IDET). IDET applies heat to the fibers
in the annulus, which puts a "seal" on the tissue
and allows it to heal.
Gene therapy
Current treatments for many spine problems require bone grafts.
Unfortunately, up to 40 percent of spinal fusions may fail to
form adequate bone. In 1997 a gene was discovered that induces
bone growth. Cell culture and early animal studies suggest the
gene is key to the body's ability to build new bone. The technology
to grow new bone has enormous potential. Although not available
yet, local gene therapy for spine fusion is poised to move from
bench research to the operating room. l used in artificial hips
and knees.
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John
J. Regan, M.D.