Posterior Lumbar Interbody Fusion Surgery
Lumbar fusion surgery is usually done to relieve the pressure off the nerve roots which may be causing sciatica pain. The procedure is usually reserved when all forms of conservative management have been tried and failed.
The vertebrae in the human spine are stacked upon each other with the intervening discs. The vertebrae form a central canal that provides a conduit for the spinal cord and its covering. Spinal nerve roots exit the spinal canal through intervertebral foramina at each level to supply the target region. The vertebral body lies in front of the spinal canal, whereas the lamina lies at the back.
Due to degenerative or traumatic conditions, the spinal nerves or the thecal sac contents may at times be compressed/irritated leading to radiating pain known as sciatica. In severe cases, the compression may also lead to weakness of the leg muscles or loss of sensation in the lower extremities. When the nonsurgical management of the lumbar radiculopathy fails, a posterior spinal fusion may help in alleviating the symptoms.
The degeneration of the disc and the facet joints in the spine may lead to back pain. A chronic back pain not amicable to nonsurgical management may be managed by lumbar fusion surgery.
Due to instability of the vertebral segment, the adjoining vertebrae may slip over one another, a condition which is known as scoliosis . The instability may result from trauma sustained in a fall or a motor vehicle accident or secondary to degeneration of the spine.
In some patients, the stabilizing structures of the spine may be absent by birth that may lead to instability. The instability is usually treated surgically in the form of a lumbar fusion with additional instrumentation in the form of screws and rods.
Deformity or misalignment of the vertebrae such as scoliosis may also be managed with posterior lumbar fusion surgery. Similarly, infections of the lower spine or some tumors may require management in the form of lumbar fusion. A failed back surgery previously performed from a different approach may be treated using a posterior lumbar fusion surgery.
The lumbar interbody fusion surgery is performed from the back of the patient. After appropriate anesthesia, an incision is given along the midline of the involved segment. The surgeon carefully retracts the spinal muscles attached to the lamina and the transverse process. The lamina is then cut to expose the spinal nerve roots. The facet joint may be trimmed or cut to make more space for the nerve roots.
The nerve roots are retracted to one side to allow the visualization and removal of the intervertebral disc material. The intervertebral disc is removed and the adjoining surfaces of the vertebrae are freshened to introduce a prosthetic bone cage.
The bone cage ensures to maintain the distance between the vertebrae after removal of the disc. The bone cage also helps relieve the pressure off the spinal nerve roots.
Bone graft is then filled in the space between the vertebrae and the bone cage. The bone graft may be harvested from the patient during the surgery from the pelvic bone. The lamina and parts of the vertebrae removed during the surgery may also be used as a bone graft. A bone graft may also be utilized from the bone bank.
During the surgery, if instability of the vertebral segment is anticipated, pedicle screws may be inserted in the segment from the sides. A metallic rod is tightened over the screws to make a solid construct. The instrumentation ensures stability and early rehabilitation.
The instrumentation also helps in the early fusion of the involved vertebrae. The surgeon closes the incision in layers at the end of the surgery.
As with any surgical procedure, there may be medical complications such as blood clots, infection, myocardial infarction, respiratory failure. Specific to the procedure there may be complications of nerve damage, dural sac rupture, blood loss during the surgery. After the surgery, there may be complications of hardware subsidence, failure of fusion, radiculitis, etc.
The patients are usually motivated to walk the same day of the surgery or the day after. The patients may be observed in the hospital or discharged the same day of the surgery depending upon the level of fusion.
The patient may be instructed to avoid movements that may lead to hardware subsidence. After the initial post-operative period, physical therapy may be started to increase the strength and flexibility of the muscles of the lower back.
Posterior lumbar interbody fusion is a successful surgical option for patients with lumbar spine disease when indicated. The surgery may also be performed through minimally invasive techniques that utilize less cutting of the tissues to achieve fusion.