Increased Force on the Lumbar Spine
While the anatomy of the cervical (neck) and lumbar (low back) vertebrae and discs may be similar, the stresses experienced by the two spinal areas are vastly different. The cervical spine only supports the weight of the head. Conversely, the lumbar spine must support the weight of the head, arms and complete torso. This creates challenges when designing an artificial disc that can sustain the forces imposed on it during everyday activities and more strenuous activities like sports of exercising.
Natural discs not only function as the lubricant that allow the spine to rotate and bend, but they are also important for absorbing the shock of simply activities like walking or running. This shock absorption quality is especially important in the lumbar area.
Current artificial disc technology is able to maintain the natural bending and rotating function of the healthy spine, as compared to spinal fusion. However, current FDA approved technology does not yet account for the shock absorption properties found in the natural discs. Shock absorbing disc are on the horizon and will likely be seen in the near future.
Accessing the Lumbar Spine
Another challenge relating the lumbar artificial disc replacement is the difficulty in accessing the lumbar spine to perform the surgery. To install most current artificial discs approved in the United States, the surgeon must access the vertebrae from the front. This is not an issue for cervical (neck) artificial disc replacement in which the incision is made near the throat, only a short distance away from the target vertebrae.
Lumbar artificial disc, however, is more complicated, requiring an incision be made in the lower abdomen. The surgeon much then navigated through the abdominal area to reach the front of the spine. Generally speaking, many spine surgeons believe access to the cervical discs can be easier than the lumbar discs. This is also the case for revision surgery if the artificial disc wears down and needs to be updating, requiring an additional surgery.