Artificial Disc Replacement
Artificial Disc Replacement (ADR)
Much like the replacement of other joints in the body with mechanical devices, the artificial disc replaces the main soft tissue component of the spine's intervertebral joints, that is, the spinal disc. The spinal disc is situated between the vertebrae forming the center of the intervertebral joint and gives flexibility to the spine. Unlike the replacements of other joints in the body, the artificial disc replacement will last much longer.
Moveable mechanical intervetebral joint replacements are more desirable for patient quality of life than rigid fusion of the bones at the joints. They also appear to reduce complications with other spinal structures over time. If done properly, artificial disc replacement also has a reduced healing time and higher success rate than fusion.
The modern artificial disc replacement began in the late 1980’s in the Charite Hospital in Berlin, Germany. The research, devices and surgical techniques have evolved since then, following the normal course of medical innovations.
Initially only the lumbar spine was considered for the artificial disc replacement, but since 2003 the cervical spine has also been treated with ADR. The thoracic spine, except for rare occasions at T1 and T2, is considered too rigid and inaccessible to benefit from ADR surgery.
The primary indications for artificial disc replacement are a combination of pain and degenerative disc disease, although pain does not always have to be present, as in the case of insidious spinal myelopathy. Very often these conditions are accompanied with a disc herniation as shown in the image.
The chief contraindications for artificial disc replacement surgery are :
- Spondylolisthesis > than grade 1
- Pars defects
- Bone Cancer
Mild to moderate facet arthrosis is no longer considered to be a contraindication, due to long term studies of these patients. Severe facet arthrosis can be managed with a facetomy and DSS.
Osteoporosis and Osteopenia are not considered problematic in the cervical spine and in the lumbar spine the AMP vertebroplasty procedure makes ADR possible. AMP vetebroplasty is the injection of bone ceramics into the affected vertebrae.
Degenerative Disc Disease
Degenerative disc disease is a step-child of spondylosis, which is the general degenerative disease of the spine. This disease represents a decrease in the production of proteins, which protect the bones of the spine and give strength to the outer covering of the discs, the annulus. It is also known, the nutrients from the bones, which are transmitted through endlplates to the disc, decreases. This is viewable in MRIs and is known as Modic changes. As a part of aging, DDD occurs in most everyone and is usually not a problem, but in some people this aging occurs more rapidly than others. Environmental contributors have not been fully identified.