Spinal Fusion

Doctors sometimes recommend spinal fusion for pain relief, to correct a deformity or to improve a patient’s stability. Patients with scoliosis, severe arthritis in the spine or a herniated disk may all be candidates for this surgical procedure.

Spinal fusion means that the surgeon locks together some of the bones in the spine. This limits the movement of these bones, which may help relieve pain. Even though the patient will have restricted movement in the back or neck after the surgery, the spine may feel more flexible because moving is less painful.

To fuse vertebrae, the surgeon grafts bone to an area of the spine. This tricks the body into thinking it has a fracture and sets up a biological response that causes the bone to grow between the two vertebral elements. Once the bone grows in, it prevents motion at that segment.

There are a few different types of spinal fusion surgeries, depending on the direction from which the surgeon approaches the spine.

  • Anterior lumbar interbody fusion (ALIF) means performing surgery on the front of the spine, that is, approaching to the side of the patient’s abdomen.
  • In a posterior lumbar interbody fusion (PLIF), the surgeon makes an incision in the patient’s back.
  • Transforaminal Lumbar Interbody Fusion (TLIF) also requires an approach through the back of the patient’s body.

Each procedure has advantages and disadvantages and carries a different set of risks. Which approach works best depends on the patient’s condition and on the surgeon’s skill.

Anterior lumbar interbody fusion (ALIF)

Surgeons may recommend anterior lumbar interbody fusion (ALIF) for patients who suffer from degenerative disc disease, spinal instability or degenerative disc disease. The goal is to stabilize the spine so that pain or deformity is reduced.

With an ALIF, the surgeon approaches through the front, or anterior, of the patient, and adds a bone graft to the front of the spine. The graft could be autograft—a piece of the patient’s own bone, taken from another part of his or her body—or allograft—a piece of bone from a donated cadaver. Advantages of ALIF include leaving the back muscles and nerves undisturbed, and that the bone graft tends to fuse better when inserted into the front of the spine because that places it in compression.

Some ALIF procedures will be done using a minilaparotomy (one small incision) or with an endoscope (a scope that allows the surgery to be done through several one-inch incisions). The surgeon’s training will dictate which procedure he or she is most comfortable using.

THE ALIF PROCEDURE:

    • 1. Surgical approach
      The surgeon cuts a three- to five-inch incision on the left side of the abdomen or in the midline. Since the anterior abdominal muscle (rectus abdominis) runs vertically, the surgeon can easily retract these muscles to the side without cutting. The abdominal contents lay inside a large sack (peritoneum) that can also be retracted, thus allowing the surgeon access to the front of the spine.
      Alternatively, the peritoneum can be cut and the abdominal contents retracted to approach the spine. The large blood vessels that continue to the legs (aorta and vena cava) also need to be retracted off of the anterior spine. A general or vascular surgeon often performs this part of the procedure.
    • 2. Disc removal
      Once the correct disc space has been identified on x-ray, the surgeon removes the disc by first cutting the outer annulus fibrosis (fibrous ring around the disc) and removing the nucleus pulposus (the soft inner core of the disc).

      3. Preparation of the fusion bed
      After the disc is removed, a space remains between the vertebral bodies. The surgical team must be sure the space is the exact height, width and depth needed for the bone graft. They may use special tools to shave adjacent discs or add small spacers made of titanium, plastic, metal or bone. Once the space is meticulously prepared, it’s ready for the bone graft.

    • 4. Bone graft and fusion
      If the patient is using autograft bone, and thus being his or her own donor, the surgeon will often choose the pelvis as the donation site. Since the lumbar disc spaces are tall, the patient will often require extra material in addition to the bone graft to fill the space and to provide a structural, weight-bearing component. This strut is usually made of allograft, or donated bone.

Recovery
Patients may need to stay in the hospital for a day or two after surgery. Once they go home, they can expect a six to twelve week recovery as the bone graft does its fusion work. Bone forms better if motion is limited, so patients should avoid bending, lifting, and twisting for three months after spinal fusion surgery.

Possible risks and complications

The principal risk of ALIF is that the bones may fail to fuse. Autograft bone usually heals better than allograft bone. However, some patients experience more pain at the bone removal site than they do in their spine.

Other possible risks include:

      • Damage to large blood vessels, resulting in excessive blood loss
      • Injury to the bowel or ureter, which are close to the lower lumbar discs
      • Retrograde ejaculation, or ejaculating backwards into the bladder
      • Dislodged bone graft

Chronic pain, infection, bleeding, nerve damage or fracture at the bone graft site (especially with larger bone grafts)

Posterior lumbar interbody fusion (PLIF)
Surgeons may recommend posterior lumbar interbody fusion (PLIF) for patients with painful spinal conditions, including spondylolisthesis and degenerative disc disease. The goal is to stabilize the spine so that pain or deformity is reduced.

A PLIF requires the surgeon to approach through the patient’s back. “Interbody fusion” means the surgeon will remove an intervertebral disc and replace it with a bone spacer. Surgeons sometimes favor a posterior over an anterior approach when the patient needs a laminectomy (removal of the lamina, or back part of the veterbrae) along with the fusion, and when they plan to insert metal rods and screws. Traditionally, a PLIF involves inserting two small bone graft spacers and retracting spinal nerves.

The PLIF procedure

Surgical approach
The surgeon cuts a three-inch to six-inch long incision in the midline of the back. He or she then retracts the spinal muscles, allowing access to the vertebral disc. MRI and CAT scans before the surgery let the doctor plan exactly the right size implants for the patient.

Laminectomy

The surgeon removes the lamina to access the nerve roots. It may be necessary to trim the facet joints, which lie over the nerve roots. The surgeon removes the troubled disc and prepares the surfaces of adjacent vertebrae.

Inserting the implants

Once the disc space is ready, the surgeon places the bone graft. The graft could be autograft—a piece of the patient’s own bone, taken from another part of his or her body—or allograft—a piece of bone from a donated cadaver. Rods and screws may also be necessary to provide sufficient spine stabilization.

Recovery
Patients may need to spend two to four days in the hospital after surgery. They should plan to take a couple of weeks off driving, especially if they’re using opioid medications for pain. Most people can resume an office job in four to six weeks, but it could take a few months to return to more physical work. It usually takes three to six months for the bone graft to become fully integrated into the spine. During that time, it’s best to limit motion. Patients should avoid bending, lifting, and twisting for three months after spinal fusion surgery.

Possible risks and complications

Risks of PLIF include failure for the vertebrae to fuse, infection, bleeding, and damage or disease to adjacent discs. Because PLIF requires substantial retraction of the nerve roots to gain access to the disc space, the nerve root could be injured. This may result in severe chronic leg pain and back pain.

Transforaminal lumbar interbody fusion (TLIF)

Transforaminal lumbar interbody fusion (TLIF) is one of the newer techniques surgeons use to to stabilize the spinal vertebrae. It treats painful conditions of the back, including degenerative disc disease, spondylolisthesis and recurrent disc herniations.

When doing a TLIF, the surgeon approaches through the patient’s back to insert the bone graft or bone graft substitute and hardware. As the patient heals, the bone graft and interbody spacer stabilize the front portion of the spine. Hardware like rods and pedicle screws work with the bone graft to lock the posterior part of the spine into place.

The TLIF Procedure

Surgical approach

The surgeon cuts a three-inch to six-inch long incision in the midline of the back. He or she then retracts the spinal muscles on one side, allowing access to the vertebral disc.

Laminectomy

The surgeon removes the lamina (bones protecting spinal cord) to access the nerve roots. It may be necessary to trim the facet joints, which lie over the nerve roots. The surgeon clears the disc area and prepares the surfaces of adjacent vertebrae.

Inserting the implants
The surgeon places an interbody cage filled with bone graft into the disc space, making sure to maintain the correct disc height. He or she places additional bone in the side gutters of the vertebra and in the disc space, then attaches pedicle screws to plates or rods.

Recovery

Patients stay in the hospital for three to five days after a TLIF. Some require blood transfusion. Doctors usually urge patients to start physical therapy as soon as the day after surgery. Patients can generally return to sedentary jobs in four six weeks. Active occupations will require a longer recovery time.

Possible risks and complications

TLIF doesn’t always work. Sometimes bone grafts don’t take and the spine fails to fuse. Continued pain is also possible. As with most surgeries, TLIF carries the risk of blood loss, nerve injury, infection and adverse reactions to anesthesia.

    • Artificial Disc Replacement

The discs between vertebrae are designed to cushion and support the spine. But as people age, their discs naturally degenerate. Some people weather this process without problems. But other people experience pain, numbness and loss of function. Traumatic injury can also cause disc degeneration or herniation.

Your doctor will first suggest non-surgical treatment options for degenerated discs. Sometimes all it takes is anti-inflammatory medications, hot and cold packs or physical therapy. But if a patient’s condition doesn’t respond to these less invasive interventions, a doctor might recommend surgery.

The two main surgical solutions would be fusing some vertebrae together, or replacing the painful disc with an artificial disc. The two types of artificial disc surgery are lumbar, for the lower back, and cervical, for the neck. Most artificial discs are made with an outer shell of titanium, cobalt chromium or other metal, and an inside of medical grade plastic. They aim to replicate the form and function of real discs.