1. Technical Field
This invention relates generally to treatments for back pain. More particularly, this invention relates to a treatment for degenerated, herniated or ruptured intervertebral discs. Specifically, this invention is directed to an apparatus and method for replacing the nucleus pulposus of a damaged intervertebral disc which includes removing the original nucleus pulposus, inserting an implant receptacle into the void in the disc created by the removal of the nucleus pulposus, injecting an implant substance into the implant receptacle, and applying electromagnetic radiation, particularly infra-red or near infra-red radiation, to the implant substance in the receptacle to harden it into a viscoelastic state so that it is able to perform in much the same manner as the original nucleus pulposus.
2. Background Information
The human spine is made up of a series of vertebrae that are separated from each other by intervertebral discs. The spine also includes other components such as ligaments, tendons, and the spinal cord. A network of nerves originates in the spinal cord and spreads outwardly into the body from the spine.
If one looks at the spine from the side, each intervertebral disc extends from the bottom of one vertebra to the top of the vertebra below it. The intervertebral discs are closed hydraulic systems that act as shock absorbers in the spine and they aid in absorbing the axial loads on the body. The discs act to bind the vertebrae together and also aid in helping the spine to twist and turn as the person moves.
Each intervertebral disc is made up two components, namely, the nucleus pulposus and the annulus fibrosus. The annulus fibrosus is a series of concentric lamellae or membranes formed from collagen in combination with proteoglycan and water. The lamellae are arranged in a special configuration to form a strong sac which surrounds and contains the nucleus pulposus. The annulus fibrosus is strengthened toward its posterior or back region by a ligament. A cartilaginous end plate is also a boundary for the top and bottom regions of the lamella and these plates contact the vertebrae above and below the intervertebral disc.
The nucleus pulposus is a semi-fluid, gelatinous substance which is essentially the material that absorbs shocks and allows the spine to pivot. The nucleus pulposus is under extremely high pressure and pushes outwardly on the lamellae and it is the job of the lamellae to contain this pressurized material.
As people age, the lamellae may become desiccated i.e., dehydrated, and degenerate to the point that they are no longer able to adequately contain the nucleus pulposus under pressure. A weakened area may develop in the annulus fibrosus and a small bulge or hernia can develop in this weakened area and extend outwardly beyond the outer perimeter of the annulus fibrosus. This bulge will tend to apply pressure to the nerves that are disposed adjacent the posterior region of the intervertebral disc, causing much pain and discomfort.
If the weakened area continues to deteriorate, the annulus fibrosus may rupture, spilling some of the nucleus pulposus material onto the surrounding nerves and tissues. This jelly-like substance contains chemicals that may cause inflammation and damage to the surrounding tissues and nerves and may therefore lead to an increase in pain. Additionally, with a ruptured disc, much of the shock absorbing property of the disc are lost, resulting in increased difficulty of movement for the patient and, again, a possible increase in the level of pain that they experience. The herniation or rupture of intervertebral discs is thought to be responsible for chronic back pain in around fifty percent of patients who suffer from back pain. It will be understood that traumatic injuries may also result in damage to intervertebral discs with the same consequences.
Another problem with aging is that the nucleus pulposus may itself become desiccated over time. As the nucleus pulposus shrinks, the intervertebral disc tends to collapse inwardly because there is no longer any outward pressure on the annulus fibrosus. As the disc collapses, the vertebrae may contact each other or may pinch nerves between them, thereby leading to much pain.
A number of solutions have been proposed in the art for treating patients with degenerated, ruptured, herniated or collapsing discs. In the case of ruptured or herniated discs, it has been proposed to make a small puncture in the annulus fibrosus to allow some of the nucleus pulposus to flow out of the disc. The puncture may be made in a variety of ways such as by way of a needle or a laser. Some have suggested that this type of treatment could suck the herniated portion of the nucleus pulposus back into the interior of the disc. Others have proposed partially or completely removing the nucleus pulposus from ruptured discs to reduce the pressure therein and to prevent leakage thereof into the surrounding nervous tissue. The removal or decrease in the quantity of nucleus pulposus within a disc has been accomplished through various means including application of heat, chemical treatments or treatment with radiofrequency energy, for example. Yet others have proposed entirely removing the intervertebral disc and then fusing the vertebrae together to prevent collapse of the spine. Such fusion may be accomplished by introducing a small piece of bone or titanium between those vertebrae which flank the removed disc. In other instances, parts of the adjacent vertebrae are surgically removed along with the disc and a bone graft and/or metal plate may be joined to those adjacent vertebrae to stabilize the spine. Still further, the intervertebral disc may be removed and an artificial disc may be surgically implanted into the spine. Finally, it has been proposed that the intervertebral disc be heated to a particular temperature (such as 90°) for a particular length of time (such as 15 minutes) in order to try and seal the ruptured lamellae.
While many of these procedures have helped patients, there is still a need in the art for a less invasive method of treating degenerated, herniated, ruptured or collapsed intervertebral discs that may restore much of the shock absorbing quality of the disc and may lead to a possible reduction in the levels of chronic back pain experienced by the patient.