When spinal conditions require surgery to correct them, knowing how they work is important.
Artificial disc replacement surgery involves replacing a damaged spinal disc with an artificial one. These artificial discs are designed to mimic the form and function of the spine’s natural disc, with the goal of eliminating back pain and maintaining range of motion and movement. In a normal healthy spine, there are plump and flexible spinal discs located between each vertebra. They work to cushion these small but powerful bones and allow the spine to twist and bend without any pain. Age, genetics and everyday wear-and-tear from routine activities can eventually contribute to damage and degeneration of these discs, as well as disc herniation where the disc slips out from its usual position. When these damages begin to occur to the discs, the cushion between the vertebrae is compromised and no longer able to provide the optimal protection to the spine, often leading to acute or chronic back pain and a reduced range of spinal motion.
The first line of treatment for damaged spinal discs (and any other problems with the spine) involves conservative or non-invasive methods. This could include physical therapy, anti-inflammatory medications or steroid injections, or chiropractic therapy. If these non-invasive options fail to resolve the patient’s pain or other symptoms, surgery may then be considered. Typically, surgery is not considered for disc-related pain unless the pain has been severe for a prolonged period of usually over six months, and the patient has attempted non-operative treatments first.
Traditionally, the operative treatment for disc pain has been spinal fusion. This type of procedure removes the damaged disc material from between the vertebrae, and instead of replacing it with a healthy disc, fuses the two vertebrae together so that there can be no movement between them. Spine surgeons perform this procedure with the reasoning that if the vertebrae cannot move, there will be no pain in that area. The downfall to this procedure, however, is just that – there is no movement between the vertebrae, which will reduce the patient’s ability to move naturally. Artificial disc replacement on the other hand, replaces the disc and allows the patient to maintain the natural movement of the back which is preferable by spine surgeons, as our goal is to return the spine to as natural a state as possible.
In addition, after a spinal fusion, the fused part of the spine often causes extra stress to be placed on the vertebrae and discs directly above and below it, as they are forced to carry a larger load and endure more wear and tear. Artificial disc replacement surgery avoids this problem, as the new artificial disc is designed for and able to absorb shock while imitating the functions of a healthy disc – providing a normal distribution of stress along the spine and facilitating motion just as the natural, once-healthy disc did. Patients are in fact encouraged to return to motion early after artificial disc replacement surgery, though at a gradual progression.
There are two different options for replacing a spinal disc. The surgeon can elect to remove and replace the entire disc, or can replace only the nucleus (center), while the outer part of the disc remains in place. The type of artificial disc to use depends on the cause of the back pain and the severity of the problem. A nucleus replacement may be an option for patients with early-stage disc degeneration where the outer portion is still in good condition. In more advanced-disease stages where the outer portion is also compromised, total disc replacement may be indicated. In the case of a total disc replacement, after the damaged disc is removed from between the vertebrae, two metal plates are secured to the vertebrae above and below the now empty intervertebral space and a plastic spacer is inserted between them. After surgery, the patient’s own body weight compresses the spacer and allows for maximum degree of movement. The goal of each type of disc replacement is the same: returning the spine to a normal anatomy to eliminate pain and maintain natural range of motion.
At this moment, nucleus replacement devices are not approved in the United States and have not been as successful as anticipated. Artificial disc replacement devices for both the neck and back have been approved by the FDA and there is extensive experience with their use.
Though there are clear advantages to artificial disc replacement and it is a promising option for many, there are still certain circumstances under which not every patient is a candidate. Spondylolisthesis, osteoporosis, obesity, or other conditions that compromise the integrity of the spine may prevent someone from receiving a disc replacement. Your spine surgeon will be able to discuss your detailed health history with you, to provide the option that will suite you best and provide the most successful outcome with the least amount of risk.