Spinal Fusion Surgery

From the North American Spine Society (NASS) website

What is Spinal Fusion

The spine comprises a series of bones called "vertebrae"; between each vertebra are strong connective tissues, which hold one vertebra to the next and act as a cushion between the vertebrae. Spinal Fusion The disc allows for movements of the vertebrae and lets people bend and rotate their neck and back. The type and degree of motion vary between the different levels of the spine: cervical (neck), thoracic (chest), or lumbar (low back). The cervical spine is a highly mobile region that permits movement in all directions. The thoracic spine is much more rigid due to the presence of ribs and is designed to protect the heart and lungs. The lumbar spine allows mostly forward and backward bending movements (flexion and extension).

Fusion is a surgical technique in which one or more of the spine's vertebrae are united ("fused") so that motion no longer occurs between them. The concept of fusion is similar to that of welding in industry. Spinal fusion surgery, however, does not weld the vertebrae during surgery. Instead, bone grafts are placed around the spine during surgery. The body then heals the grafts over several months - similar to healing a fracture - which joins, or "welds," the vertebrae together.

When Is Fusion Needed

A surgeon may consider fusing the vertebrae for many reasons. These include treating a fractured (broken) vertebra, correcting deformity (spinal curves or slippages), eliminating pain from painful motion, treating instability, and treating some cervical disc herniations.

One of the less controversial reasons to do spinal fusion is vertebral fracture. Although not all spinal fractures need surgery, some fractures - particularly those associated with spinal cord or nerve injury - generally require fusion as part of the surgical treatment. Severe spine bend (see x-ray below)

Certain types of spinal deformity, such as scoliosis, are commonly treated with spinal fusion. Scoliosis is an "S" shaped spine curvature that sometimes occurs in children and adolescents. Fusion is indicated for very large or smaller curves that are getting worse.

Sometimes, a hairline fracture allows vertebrae to slip forward on top of each other. This condition is called spondylolisthesis (see North American Spine Society patient education brochure on Adult Isthmic Spondylolisthesis) and can be treated by fusion surgery.

Another condition treated by fusion surgery is actual or potential instability. Instability refers to abnormal or excessive motion between two or more vertebrae. It is commonly believed that instability can cause back or neck pain, irritation, or damage to adjacent nerves. Although there is some disagreement on the precise definition of instability, many surgeons agree that definite instability of one or more spine segments indicates fusion.

Cervical disc herniations that require surgery usually need not only removal of the herniated disc (discectomy) but also fusion. This procedure removes the disc through an incision in the front of the neck (anteriorly), and a small piece of bone is inserted in place of the disc. Although disc removal is commonly combined with fusion in the neck, this is not generally true in the lower back (lumbar spine).

Spinal fusion is sometimes considered in the treatment of a painful spinal condition without apparent instability. A major obstacle to the successful treatment of spine pain by fusion is the difficulty in accurately identifying the source of a patient's pain. The theory is that pain can originate from painful spinal motion, and fusing the vertebrae to eliminate the motion will eliminate the pain. Unfortunately, current techniques to precisely identify which structures in the spine could be the source of a patient's back or neck pain are not perfect. Because it can be so hard to locate the source of pain, treatment of back or neck pain alone by spinal fusion is somewhat controversial. Fusion under these conditions is usually viewed as a last resort and should be considered only after other conservative (nonsurgical) measures have failed.

How Is Fusion Done

There are many surgical approaches and methods to fuse the spine, and they all involve the placement of a bone graft between the vertebrae. The spine may be approached, and the graft placed either from the back (posterior approach), front (anterior approach), or a combination of both. In the neck, the anterior approach is more common; lumbar and thoracic fusion is usually performed posteriorly.

The ultimate goal of fusion is to obtain a solid union between two or more vertebrae. Fusion may or may not involve the use of supplemental hardware (instrumentation) such as plates, screws, and cages. Instrumentation is sometimes used to correct a deformity but is usually used as an internal splint to hold the vertebrae together while the bone grafts heal—open view.

Whether or not hardware is used, bone or bone substitutes must be used to get the vertebrae to fuse. The bone may be taken from another bone in the patient (autograft) or a bone bank (allograft). Fusion using bone taken from the patient has a long history of use and results in predictable healing. Autograft is currently the "gold standard" source of bone for fusion. Allograft (bone bank) bone may be an alternative to the patient's bone. Although healing and fusion are not as predictable as with the patient's bone, allograft does not require a separate incision to take the patient's bone for grafting and is associated with less pain. Smoking, medications you are taking for other conditions, and your overall health can affect the rate of healing and fusion, too.

Promising research is currently being conducted on synthetic bone as a substitute for autograft or allograft. Synthetic bone substitutes will likely eventually replace the routine use of autograft or allograft bone.

With some of the newer "minimally invasive" surgical techniques currently available, fusion may sometimes be done through smaller incisions. The indications for minimally invasive surgery (MIS) are identical to those for traditional extensive incision surgery; however, it is essential to realize that a smaller incision does not necessarily mean less risk involved in the surgery.

How Long Will It Take To Recover

The immediate discomfort following spinal fusion is generally more significant than with other types of spinal surgeries. Fortunately, excellent methods of postoperative pain control are available, including oral pain medications and intravenous injections. Another option is a patient-controlled postoperative pain control pump. With this technique, the patient presses a button that delivers a predetermined amount of narcotic pain medication through an intravenous line. This device is frequently used for the first few days following surgery.

Recovery following fusion surgery is generally longer than for other types of spinal surgery. Patients typically stay in the hospital for three or four days, but a more extended stay after more extensive surgery is not uncommon. A short stay in a rehabilitation unit after release from the hospital is often recommended for patients who had extensive surgery or for elderly or debilitated patients.

It also takes longer to return to a normal active lifestyle after spinal fusion than many other types of surgery. This is because you must wait until your surgeon sees evidence of bone healing. The fusion process varies in each patient as the body heals and incorporates the bone graft to solidly fuse the vertebrae. The healing process after fusion surgery is similar to a bone fracture. The earliest evidence of bone healing is not apparent on X-ray until at least six weeks following surgery. During this time, the patient's activity is generally restricted. Substantial bone healing does not usually occur until three or four months after surgery. At that time, activities may increase, although evidence of bone healing and remodeling may continue for up to a year after surgery.

The time you will need to be off work will depend on the type of surgery and your job. It can vary from approximately 4-6 weeks for a single-level fusion in a young, healthy patient with a sedentary job to as much as 4-6 months for more extensive surgery in an older patient with a more physically demanding occupation.

In addition to some restrictions in activity, a brace is sometimes used for the early postoperative period. Many types of braces might be used. Some are very restrictive and are designed to severely limit motion, while others are intended mainly for comfort and to provide some support. The decision to use a brace or not, as well as the optimal type of brace, depends upon your surgeon's preference and other factors related to the type of surgery.

Following spinal fusion surgery, a postoperative rehabilitation program may be recommended by your surgeon. The rehabilitation program may include back strengthening exercises, possibly a cardiovascular (aerobic) conditioning program, and a comprehensive program custom-designed for the patient's work environment to get the patient back to work safely. The decision to proceed with a postoperative rehabilitation program depends upon many factors. These include factors related to the surgery (such as the type and extent of the surgery) and aspects related to the patient (age, health, and anticipated activity level.) Active rehabilitation may begin as early as 4 weeks postoperatively for a young patient with a single-level fusion.

What Can I Expect in the Long Run

Although fusion can be an excellent treatment for some spinal conditions, it does not return your spine to "normal." The normal spine has some degree of motion between vertebrae. Fusion surgery eliminates the ability to move between the fused vertebrae, which can put added strain on the vertebrae above and below the fusion. Fortunately, once a fusion has healed, it rarely, if ever, breaks down. However, it does place more stress on the vertebrae next to the fusion. This has some potential to accelerate the degeneration of those segments, but this risk varies between individuals. Many surgeons, therefore, recommend that spinal fusion patients avoid repetitive strenuous activities that involve combined lifting and twisting maneuvers to minimize the stress on the areas around the fusion.

The decision whether or not to undergo spinal fusion is complex and involves many factors related to the condition being treated, the age and health of the patient, and the patient's anticipated level of function following surgery. Therefore, This decision must be made carefully and discussed thoroughly with your surgeon.