Back Pain and Spinal Surgery
One common cause of low lumbar back pain is "degenerative disc disease"
also known as "DDD". The condition may take many different forms
(e.g. a herniated disc or a collapsed disc) and your doctor may also describe
it differently. Any of these conditions can result from a disc that has
lost its proper form and therefore does not function properly, causing
significant pain when you move or attempt to perform normal daily activities.
The purpose, then, of any spinal surgery or disc surgery is to relieve
this recurring back pain.
One common surgical method for relieving this type of back pain is to stop the
movement of the afflicted disc or motion segment by fusing the vertebrae
together in that specific area. This is referred to as "spinal fusion
surgery". There are different methods of spinal fusion surgery, but most
involve placing metal implants (e.g. plates, rods and screws) into the
vertebrae or bones of the spine to hold them still and achieve what is referred
to as a "fusion". This type of procedure may also involve placing
bone or fusion cages into the disc space to assist in fusing the spine bones
together.
Total disc replacement surgery or total disc arthroplasty is a very different
type of degenerative disc surgery utilizing an artificial disc or prosthesis
with significant philosophical advantages over traditional spinal fusion
surgery.
The Concept of a Total Disc Replacement
The theoretical advantages of a total disc replacement over more traditional
surgical treatment (e.g. fusion) of damaged discs or motion segments are
extraordinary. Differing from current spine fusion techniques, total disc
replacement is intended to maintain motion at the operative level once the
damaged disc has been removed. Additionally, total disc replacement
theoretically protects the discs at adjacent levels by sharing or distributing
the stress through the lower back during normal activities such as lifting and
bending (flexion and extension).
Replacement of painful arthritic joints is extremely common. For example,
artificial hip and knee replacements are among the most successful and reliable
operations performed today, with good results typically in over 90% of
patients.
Since artificial hips and knees were introduced in the 1960’s, surgeons
have explored the idea of prosthetic replacements for damaged or degenerated
intervertebral discs. As the intervertebral disc and its biomechanical behavior
are very complex, the engineering a total disc replacement has been
challenging. Total disc replacement with DePuy Spine's CHARITÉ® Artificial Disc has been performed in Europe for over 14 years and has been
used in treating nearly 4,000 patients worldwide.
Theoretical Advantages
The CHARITÉ® implant is designed to mimic the functionality of the
patient’s own disc. The prosthesis is intended to return near normal
movement between the vertebral bodies and to prevent them from collapsing by
maintaining the disc space height between them.
One of the major theoretical advantages of the artificial disc is that it
preserves the mobility of the patient’s adjacent discs and delays the
onset of arthritic changes adjacent to the operative level. For some
indications, the procedure can be a substitute for spinal fusion, which
eliminates the motion from a painful motion segment by fusing the vertebrae
together. Spinal fusion does tend to place increased stress on the adjacent
vertebral segments.
The CHARITÉ® Artificial Disc
The CHARITÉ® Artificial Disc
(also known as an artificial disc
or total
disc replacement) was originally developed at the CHARITÉ University Hospital in Berlin, Germany
in the mid-1980’s by Prof. Karin Büttner-Janz, Prof. Kurt Schellnack,
leading spine specialists. Further refinements to the design were incorporated
with the cooperation of the staff at Waldemar Link GmbH, a leading
European based medical device manufacturer based in Hamburg, Germany.
The CHARITÉ® is a prosthesis system consisting of two endplates made of
high quality cobalt chromium alloy with an ultra high molecular weight
polyethylene sliding core placed between them. Both of these materials are well
tolerated by the body and are the same standardized implant materials that have
been used in artificial hip and knee prostheses for the last 30 years. The
endplates are also coated with a titanium and hydroxyapatite porous coating to
enhance bony fixation to the vertebral bodies.
The endplates are attached to the vertebral bodies by means of anchoring teeth
along their edge. The polyethylene sliding core is placed between these
articulating endplates and is designed to allow near normal physiological
movement. Much like an artificial hip or knee that relies on metal and plastic
bearing surfaces to replicate normal movement of those joints, the
CHARITÉ® Artificial Disc is designed to closely mimic the normal function
of a healthy disc.
The surgical procedure for the CHARITÉ® requires placement of the implant
using an anterior (front) approach with a small incision just below the belly
button. The degenerative disc is removed at the affected level and the
CHARITÉ® Artificial Disc is placed into the disc space.
The CHARITÉ® has received the CE mark and is commercially available
outside of the United States in over 25 countries throughout Europe, Asia,
Canada, Australia, Africa and Latin America.
The CHARITÉ® Artificial Disc is an investigational device limited by US
(Federal) law to investigational use in the USA.
The Surgical Procedure
The goal of the procedure is to restore the intervertebral disc height and
neuroforaminal height while restoring physiologic motion (similar to that of a
healthy disc). The surgery is approached from the front (directly anterior),
with a small incision in the abdomen below the umbilicus (belly button).
Abdominal structures are gently moved to the side so that the surgeon can
visualize the spine while protecting important anatomic structures. The
collapsed degenerated disc is then removed.
The CHARITÉ® is implanted – two endplates and a plastic core in the
middle – using specialized instruments. The two endplates (made of a
cobalt chromium alloy) are pressed into the vertebrae above and below the disc
space, and teeth along the border of the endplate grip the bone. An ultra-high
molecular weight polyethylene (UHMWPE) core is then placed between the
endplates.
The prosthesis stays in place by means of the teeth on the endplates, the
tension in the spinal ligaments as well as the compressive force of the spine.
Bending X rays of patients after the surgery show that the motion of the
artificial disc (flexion, extension, lateral (side) bending, translation and
rotation) can closely approximate the normal motion of a healthy disc or motion
segment.
After surgery, patients can typically expect to return to daily function soon
afterwards without the need for prolonged postoperative bracing. Rehabilitation
typically starts about four days after surgery. Unlike spinal fusion surgery,
bone graft is not used so there is no potential for pain or discomfort from the
donor site.
Potential Risks and Complications
The European data of the CHARITÉ®
show a low rate of postoperative morbidity
(unwanted after effects). No deaths, infections,
major neurological problems or sexual dysfunction
have been reported.
Outcomes Research
A French study published in 1997 by Dr. J.-P. Lemaire and others described
a comprehensive clinical review of 105 patients who received the SB CHARITÉ® III
disc replacement. At an average of 8 years post-operative follow-up,
79% of patients had excellent results and 87% returned to work. For sedentary
workers (e.g. with desk jobs), 81% returned to the same job, 17% remained
employed in a different capacity, and only 2% became unemployed. For
patients
with light and heavy labor, 44% and 45% returned to the same job, respectively,
and 21% and 27%, were unemployed following the surgery, respectively.
Also in 1997, the first independent review was conducted by Dr. Alexis
Shelokov while at The Texas Back Institute in Dallas, Texas and Jeanette
Ahrens,
PhD of the Institutes for Spine and Biomedical Research an affiliate of
the Texas Back Institute Research Foundation. They conducted a retrospective
radiological and clinical assessment of 67 patients who underwent intervertebral
disc replacement with 91 SB CHARITÉ® III devices at one or two lumbar
levels performed in Europe. The patients’ average age was 42 years
(range 24 to 59 years), and postoperative follow-up period averaged 6 years
(range from 16 to 119 months).
Comparing pre- and postoperative analog pain scores, it was noted that
there was significant pain relief among the patients. 70% of the patients
decreased or discontinued their use of pain medication following the procedure
and 46% of patients reported an increase in activity level. 67% of patients
returned to work at the same or a modified physical level. Device related
complications occurred in 7% of patients.
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(Revista di Neuroradiologia)
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