Tissue Engineered Intervertebral Discs
There exists a wide array of treatments available for disc degeneration and/or disc herniation. Diagnosis of these problems is usually performed by imaging the spinal cord using MRI or CT scans [3]. The majority of cases do not require extensive treatment. A simple regimen of pain killers, bed rest, and physical therapy will alleviate the majority of symptoms associated with intervertebral disc problems.
However, in a number of cases (roughly 10%) these simpler treatments do not prove successful [3]. This is when surgery can play a vital role to treat these patients. The goal of spinal surgery is to stabilize the spinal cord and to relieve pressure from the nerves so they are no longer being pinched by a prolapsed or extruded disc.
Spinal surgery involving intervertebral discs is almost always used to treat patients with herniated discs. In these cases, the most common type of surgery is a discectomy, in which the effected disc is completely removed [1, 2, 3]. These surgeries can be performed non-invasively with little need for extensive post-op recovery. Other less common procedures involve removing sections of the vertebrae or just removing the fluid of the nucleus pulposus [3]. Once the degenerated and/or herniated disc is removed, something must be done to fill in the gap and stabilize the spinal cord.
Spinal fusion surgeries are the most common method of stabilizing the spinal cord after a diseconomy. Spinal fusion involves binding the two surrounding vertebrae together while filling in the remaining gap with either a bone graft or artificial material [3].
Screws are often used to secure the two vertebrae after the appropriate filler material has been inserted. Spinal fusion surgeries then often rely on new bone growing into the area after the surgery so that the connection can become more secure, stable, and natural [3]. The surgery is complete once the herniated disc has been removed, the filler material added, and the vertebrae fused. This type of procedure, however, greatly reduces the patient’s mobility and range of motion post-operatively. Because the two vertebrae are solidly fused together, rotation and bending around that area of the spine are greatly restricted [3]. Thus, the patient does not have the same ease and range of motion  they had before the operation. A promising alternative to this problem is to avoid using the spinal fusion surgery and use artificial intervertebral discs in place of the herniated disc.
Several types of artificial intervertebral discs exist that are made of strong metals and plastics, and are meant to functionally fill in for the removed intervertebral disc. These types of devices often consist of two metal pieces that are seeded and cemented into the upper and lower vertebrae surrounding the removed disc. The metal pieces consist of strong, corrosion-resistant alloys of metals such as cobalt, chromium, and/or titanium. Then, a piece of high-density polyethylene plastic is sandwiched in between the metal pieces to act as a point of movement so that the spine may slide, bend, and flex around the artificial disc [3].
This provides several advantages over the spinal fusion method, namely that the range of motion is almost completely restored, allowing the patient to move normally after the surgery. There are, however, still many problems with the artificial disc method. The most prevalent problem is wear of the parts. As time goes on, the polyethylene plastic, and in some cases the metal, begin to wear out and emit debris, know as particle wear. When this occurs, the immune system of the body responds to these particles by attacking them, and a side effect of this response is that local bone is also attacked. This can results in the metal parts breaking away from the vertebrae, rendering the device useless [3]. Another drawback of these devices is that they result in highly unstable spines in patients that have had more than one discectomy. Although useful in some cases, there is still a need for a better alternative to dealing with intervertebral disc problems. This is where tissue engineering approaches to solving this problem may prove very useful.
Current Solutions & Treatments
Current Solutions
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