Lumbar spinal fusion

Also known as spondylodesis or spondylosyndesis.

A spine fusion is a surgery performed to link together individual segments, or vertebrae, within the spine.

Intended to stop the motion at a painful vertebral segment, which in turn should decrease pain generated from the joint.

Multiple approaches to lumbar spinal fusion surgery, and involve adding bone graft to an area of the spine to set up a biological response that causes the bone graft to grow between the two vertebral elements and create a fusion.

Considered if abnormal and excessive motion at a vertebral segment results in severe pain and may be due to degenerative disc disease, degenerative or postlaminectomy spondylolisthesis, isthmic spondylolisthesis, unstable spine from malignancy, infection, fractures, scoliosis or other deformities.

Two vertebral segments need to be fused together to stop the motion at one segment.

A spine fusion surgery involves using bone graft to cause two vertebral bodies to grow together into one long bone, and the graft can be taken from the patient’s hip during the spine fusion surgery, harvested from cadaver bone or manufactured, or synthetic bone graft substitute.

Spinal fusion of more than two segments is unlikely to provide pain relief because it removes too much of the normal motion in the lower back and places too much stress across the remaining joints.

There are two main types of lumbar spinal fusion, which may be used in conjunction with each other.

Posterolateral fusion places the bone graft between the transverse processes in the back of the spine.

With posterolateral fusion the vertebrae are fixed in place with screws and/or wire through the pedicles of each vertebra attaching to a metal rod on each side of the vertebrae.

Interbody fusion places the bone graft between the vertebra in the area usually occupied by the intervertebral disc and the later is removed entirely.

In the Interbody fusion a device, either platic or titanium, may be placed between the vertebra to maintain spine alignment and disc height.

In the Interbody fusion, the fusion occurs between the endplates of the vertebrae.

When both types of fusion are used it is known as 360-degree fusion.

Interbody fusion has higher fusion rates than the posteriorlateral fusion.

Three types of interbody fusion are the Anterior lumbar interbody fusion whereby the disc is accessed from an anterior abdominal incision, the Posterior lumbar interbody fusion where the disc is accessed from a posterior incision, and the Transforaminal lumbar interbody fusion where the disc is accessed from a posterior incision on one side of the spine.

As part of the process to perform spine fusion instrumentation, the placing of metal within the spine to hold the vertebral bones together may be performed.

Spinal instrumentation utilization depends on many factors including the underlying problem being treated, the age of the patient, and the number of levels of the spine being fused.

In a trial involving patients undergoing surgery for degenerative lumbar spondylolisthesis, most had symptoms for more than a year, decompression alone was non-inferior to decompression with instrumental fusion over a period of two years: reoperation occurred somewhat more often in the decompression alone group than  in the fusion group (Austevoli IM).

Indications for a fusion in the setting of concomitant, spondylolisthesis, are debated, given the greater risk of complications and higher cost of fusion, balance, with the potential for improved outcomes with fusion.

Overall studies indicate the decompression alone is non-inferior to decompression plus fusion with concomitant spondylolithesis.

Fusions are commonly augmented by fixation, meaning the placement of metallic screws, rods or plates, or cages to stabilize the vertebra to facilitate bone fusion.

The fusion process typically takes 6–12 months, and if it is not successful patients may require reoperation.

Artificial disc replacement, are being offered as alternatives to fusion, but have not yet been adopted widely.

Fusion is associated with adverse effects with a study showing a 30 day all cause rehospitalization rate of 6.6% for decompression alone compared with 9.4% for decompression combined with fusion.

in this study, the 30 day mortality rate for decompression alone was 0.3% compared with 0.6% for decompression with fusion.

Wound complications for decompression alone was significantly lower than decompression with fusion.

Fusion adds significant time to surgery and is associated with increased blood loss as well.

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