Anatomy

The spine consists of 33 individual interlocking bones known as vertebrae. The vertebrae are categorized into five regions:

  • Cervical
  • Thoracic
  • Lumbar
  • Sacrum
  • Coccyx

The primary function of the vertebrae in the lumbar region of the spine is to bear the weight of the body. To support all that weight, they are larger as compared to the other vertebrae.

Intervertebral discs sit between the vertebrae and act as shock absorbers for the spine. They are flat, round and about half an inch thick. They are made up of two components—the nucleus pulposus and the annulus fibrosus. The nucleus has a jelly-like consistency and is found in the center of the disc. The “jelly” allows the disc to be flexible and strong. The annulus is the flexible outer ring of the disc and consists of several layers.

When moving or standing, weight is put on the nucleus, causing it to expand while the annulus holds it in place. Together, the nucleus and annulus allow for movement to take place while simultaneously maintaining the strength of the spine. Many nerve endings surround the annulus and, as a result, an injured annulus can cause pain.

About

Artificial disc replacement (ADR) is a procedure that helps improve lower back pain. During the procedure, the worn or damaged disc material between the small bones in vertebrae in the spine is removed and replaced with a synthetic or “artificial” disc. The goal of the procedure is to relieve back pain while maintaining a normal motion than allowed with some other procedures, such as spinal fusion.

Spinal fusion is a surgical technique that physically joins two or more vertebrae. While many patients are helped by this procedure, the results can vary. It is believed that poor spinal fusion results occur because the procedure prevents normal spine movement. ADR improves on this failure by maintaining a more normal spinal motion, which has been proven to cause better post-surgery results.

Diagnosis

ADR is not meant for everyone. Your Florida Orthopaedic Institute physician will analyze your symptoms, looking for the following:

  • Back pain caused by one or two problematic intervertebral discs in the lumbar spine
  • No significant facet joint disease or bony compression on spinal nerves
  • Body size that is not excessively overweight
  • No prior major surgery on the lumbar spine
  • No deformity of the spine (scoliosis)

Your physician may need a few tests to further decide if ADR is right for you. These tests include:

  • MRI (magnetic resonance imaging) scans
  • Diskography
  • CT (computed tomography) scans
  • X-rays

Treatment

Before your procedure, your Florida Orthopaedic Institute physician will discuss the best disc design for you, as there are many different designs to choose from. In most cases, the disc replacement substitutes for both the annulus and nucleus, with a mechanical device that will simulate spinal function. Discs can be made of metal (medical grade cobalt, chromium or titanium alloy) or a combination of metal and medical grade plastic (polyethylene). Each design, while all different, maintains a similar goal – to reproduce the size and function of a healthy intervertebral disc.

During the procedure, an incision will be made in your lower back. This incision location means that the organs and blood vessels must be moved to the side, allowing your surgeon to access your spine without moving the nerves. The disc space is then opened and exposed, the problematic disc is removed, and the artificial disc is implanted in its place.

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