Prosthetic Disc Nucleus (PDN)

Overview
A prosthetic disc nucleus replacement procedure is one that replaces the interior of a damaged vertebral disc. The spine is divided into different sections including cervical, thoracic, and lumbar portions of the spinal column, each of which contain a specific number of vertebra, or  the bony profusions felt along the ridge of the spine. The nucleus is the center of something and in this procedure, the center or nucleus of a damaged disc is replaced with a prosthetic device.

Prosthetic disc nucleus replacement procedures are also known as a PDN procedure. Prosthetic disc and implant materials can be made of ceramics, hydrogels, elastic coils, injectable fluids, and other materials. Different laboratories in the United States and around the world create their own nucleus replacements, providing a number of manufacturers and options for surgeons.

Who Benefits from Prosthetic Disc Nucleus Replacement?
Individuals who have experienced damage to the cushioning or shock absorber-type substance found in the vertebrae may benefit from a disc nucleus replacement procedure. The most common areas for damage to the spine include the neck or cervical area or the lumbar or lower back area of the spinal column. Disc nucleus replacement may help restore mobility, range of motion, and reduce pain in patients undergoing the procedure.

Prosthetic Disc Nucleus Replacement Models
Several common prosthetic disc replacement prototypes are under development today by manufactures and laboratories such as:

• Raymedica
• Newcleus
• Aquarelle Hydrogelle
• Interpore Cross
• Disc Dynamics

One of the most common types of PDN (prosthetic disc nucleus), is known as the Raymedica PDN.  This disc replacement prosthesis is used commonly outside of the United States, though its use in the United States is currently undergoing additional clinical trials. The interior of this PDN is filled with hydrogel, which is contained in a flexible polyethylene structure.

Other manufacturers and laboratories are performing experiments with a variety of components including polycarbonate urethane, elongated elastic, polyvinyl alcohol materials and ceramic or metal implant materials. The type of implant used in a replacement procedure is determined by the location of the damage disc, the country the surgery takes place, and the severity of the condition the patient is experiencing. Surgeons will determine the best type of nucleus prosthetic to be used in individual case scenarios.

Prosthetic Disc Nucleus Replacement Procedure
Because the procedure development and results are still relatively new in the United States, disc nucleus replacement surgery has not yet been approved by the FDA.  However, the procedure is often performed outside of the United States with positive benefits and results, most commonly in Europe and Asia.

Prosthetic disc nucleus replacement differs from total disc replacement procedures in that the bulk or outer portion of the vertebrae is left intact. The inside of the disc is replaced with the prosthetic device, not the entire disc. The prosthetic disc nucleus replacement procedure is designed to reestablish the original structure, form and height of the damaged disc, helping to reestablish even loads across the vertebral spaces without removing portions of the vertebral spine or necessity of extensive insertion of braces, plates and screws.

During the procedure, an incision is made in the skin over the damaged portion of the spine or damaged vertebral disc. The interior of the disc is accessed and the damaged nucleus or inner portion of the disc is removed. After the open space is flushed with cleansing and sterilizing solutions, the prosthetic device is then slipped into that space.

In contrast to total disc replacement, only very small (5 to 6 mm) holes are required to access the nucleus of the disc, resulting in less damage to overall strength and support of the vertebral disc as well as pressure on discs above and below the damaged disc.

Surgical technology and tools continue to design percutaneous approaches for the procedure, enabling extremely minimal invasive technology, resulting in less damage to the overall structure of the spine. Performing the procedure through a 5 to 6 mm cannula device ensures less tissue damage, reduced chance of blood vessel and nerve damage, as well as reduced healing and hospital stay time for patients.

How Much Does Disc Nucleus Replacement Cost?
In the United States, a total disc replacement is extremely expensive, ranging between $75,000 to $110,000. Costs for a prosthetic disc nucleus replacement procedure in the U.S. have not been determined. Foreign locations such as those in Europe and Asia may save patients tens of thousands of dollars in costs, including hospital stay. Individuals seeking disc replacement surgeries in Thailand may save even more, depending on the location and type of prosthesis or implant utilized.

Who Performs Total Disc Replacement Surgeries?
Disc replacement, partial disc replacement and disc nucleus replacement surgical procedures are generally performed by an orthopedic surgeon specializing in spine care or neurosurgeon as well as a vascular or general surgeon. Surgeons should be chosen according to their expertise and experience in related fields. Physicians and surgeons should be certified in their field, and show membership in national or regional boards or associations in his or her country of origin.