Spinal (cervical, thoracic and lumbar) fusion

Spinal fusion is surgical procedure performed to permanently immobilize a portion of the spine. It might be a primary procedure or a part of the spinal surgery. 

Fusion is a commonly performed procedure for treatment for treating various spine conditions. It is performed in order to provide stability to a segment of spine. Normally the spine is a flexible structure composed of vertebral bones and joints connecting them. In some instances, the surgeon may be willing to freeze several vertebral bones together. Usual indications for fusion are trauma, tumor, degeneration and spondylolisthesis. For example, in case of trauma there might be a bone fracture or joint disruption impairing the stability of the spine. Therefore, the surgeon might need to reconnect vertebral bones with hardware. In some cases, fusion is performed for degenerative spine disease. Spinal disc joints may become damaged by degeneration. This may cause spinal cord and nerve compression either by herniated disc and/or bone spurs. During the surgery the surgeon might need to fuse the joint completely in order to permanently eliminate possibility of recurrence. For instance, anterior cervical fusion is a common procedure for cervical disc herniation treatment. During this procedure, the surgeon removes the disc joint and relieves the pressure from the spinal cord and the nerves. Hardware is placed to keep the vertebral bones at a particular distance and allow them to fuse in the future.  This is usually done by placing a cage and bone graft between the bones. The bones afterwards are stabilized by plate and screws. 

Lumbar fusion might be performed for degenerative lumbar disease or spondylolisthesis. This procedure is different from cervical fusion and performed from the back. The surgeon removes intervertebral disc by working between spinal nerves. After the disc space has been completely cleaned up the surgeon places a cage and bone graft material and then uses screws and rods to hold vertebral bones together. 

Sometimes spinal fusion is performed after removal of the spinal tumors. Tumors may weaken the spine and/or to a reach tumor surgeon has to remove part of the spine responsible for its stability. In these cases, the surgeon must restore stability following removal of the tumor. Spinal fusion is performed to treat spinal deformity. Scoliosis (bending to side) and kyphosis (bending forward) are usually treated with spinal fusion.

In the vast majority of cases fusion is performed by implanting metallic screw to the vertebral bones. These screws hold the spine together by plates, rods or other means. If there is a gap between vertebral bones to be fused this gap is usually filled with cages and bone grafts. Interbody fusion is an example and the most common type of spinal fusion. There are several surgical techniques used to perform interbody fusion

  • In cervical spine the surgery is performed from the front and therefore – anterior cervical discectomy and fusion (ACDF) is performed
  • In lumbar spine there are several options like
    • Posterior Lateral Interbody Fusion (PLIF) fusion is performed from the back by inserting a straight cage and bone pedicle screws
    • Transforaminal Lateral Interbody Fusion (TLIF) fusion is performed from the back slightly lateral than PLIF by inserting a curved bigger cage and bone pedicle screws
    • eXtreme Lateral Interbody Fusion (XLIF) fusion is performed from the side trough the psoas muscle and a big cage is placed. It may require placement of additional bone pedicle screws.
    • Anterior Lateral Interbody Fusion (ALIF) fusion is performed from the front and a big cage is placed. It may require placement of additional bone pedicle screws.

Successful bone fusion needs some time to develop following the surgery. The eventual goal is to have two neighbor vertebral bones to fuse together. There are several keys for successful surgery. The most important aspect is robustness of hardware. Another important key is abundance of bone graft material for fusion. Grafts are placed to provide pathway for fusion. The best graft is the patient’s own bone.  

In some cases, fusion fails to develop. This condition is called nonunion. In these cases, adjacent bones become connected by soft tissue instead of solid bone.  Nonunion usually creates pain for the patient. Hardware may become loosened or even broken under constant pressure from moving spine bones further aggravating patient’s condition. There are many reasons for nonunion. Advanced age, smoking, poor bone quality, insufficient surgery are factors negatively affecting the fusion process.