Lumbar Disc Replacement

Lumbar disc replacement surgery involves replacing the damaged intervertebral disc in the lower spine to alleviate the symptoms of back pain. The total disc replacement surgery is an alternative to the more commonly performed lumbar spinal fusion surgery. The lumbar disc replacement has potential benefits when compared with the traditional spinal fusion although research continues to determine the long term results.

The intervertebral discs are present in between the two adjoining vertebrae. The disc consists of an outer thick fibrous part (annulus) and an inner soft mushy center (nucleus). The disk functions to cushion the forces acting on the vertebral column during various activities. The intervertebral disk also functions to provide stability and flexibility to the spinal column.

Bone model showing the anatomy of the spine

The vertebral column provided a safe conduit for the spinal cord and the various spinal nerves. The spinal nerves branch out of the spinal cord as it descends down from the base of the brain. The vertebral canal hosting the spinal cord/dural sac is formed of the vertebral bodies and the intervening intervertebral disks in the front.

With advancing age, the water content of the central nucleus of the disk decreases. As a result of dehydration, the disc height decreases and the intervertebral disk may herniate through the vertebral canal. The herniated disks may compress the dural sac and the transversing or descending spinal nerves. The compression/irritation of the spinal nerves and the dural sac may lead to symptoms of back pain and radiculopathy.

In the majority of patients, these symptoms are relieved in a period of few weeks with conservative management. Conservative management consists of physical therapy, activity modification, pain medications, heat and cold therapy, epidural/nerve block injections, etc.

Surgical management is reserved for patients who do not benefit from conservative treatment options for a period of at least 6 months. Spinal fusion is a popular surgical option for such patients. The fusion surgery involved the removal of the herniated disk and insertion of cage with bone graft. The cage and the bone graft help in fusion/welding of the adjoining vertebrae. The surgery often involves supplementation of the fusion with screws and rods to provide stability as the fusion heals.

The fusion surgeries function by elimination the motion between the disease vertebrae and the removal of the disease disk. The procedure is successful in the majority of the patients but some patients may still complain of back pain. The back pain may originate from the loss of the motion of the spine segment. With time, there may be accelerated degeneration of the adjoining spine segments. The adjoining segments degenerate as excess forces act on them due to fusion of a segment.

Lumbar disc replacement was devised to eliminate the shortcomings of the fusion surgery. The artificial disk reproduces the size and the function of the natural disk. The motion of the diseased segment is preserved while the diseased disk is removed.

The artificial disk may be made of surgical grade plastic (polyethylene) or may be made of metal alloys. The artificial disk rests between the surfaces of the adjoining vertebrae that are covered with metal parts.

During the procedure, the surgeon approaches the diseased lumbar vertebrae from the front of the spine. An incision is made in the abdomen and the various organs and blood vessels are gently retracted to reach the lumbar spine. The diseased lumbar intervertebral disk is removed and the ends of the vertebrae are freshened to attach the metal endplates. The artificial disk is introduced and the surgical incision is closed in layers.

The patient may stay at the hospital for 2-3 days and regular activity is permitted after the surgery. Gradually a physical therapy regimen is started to strengthen and improve the flexibility of the back.

Although with it’s advantages over the lumbar fusion surgery, not all patients are candidates for artificial disk replacement. Only patients who are not morbidly obese and with a clear disk pathology are candidates for total disk replacement. Patients with inflammatory bone diseases such as osteoporosis, ankylosing spondylitis, rheumatoid arthritis, etc are poor candidates for disk replacement. Similarly in patients whose back pain is a result of facet joint disease or any infection, tumor, fracture, etc are not candidates for disk replacement.

There may be potential complications of artificial disc replacement such as excessive bleeding, damage to blood vessels or nerves during the surgery. There may also be complications of infection, implant failure, persistent back pain, etc after the surgery.

Lumbar disc replacement surgery is increasingly being performed as an alternative to lumbar fusion surgery. Majority of the patients achieve excellent results and a marked reduction in back pain. Your orthopaedic spine surgeon will determine if you are a candidate for artificial lumbar disk replacement surgery.