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Bone Grafting

All spinal fusions use some type of bone material, called a bone graft, to help promote the fusion. Generally, small pieces of bone are placed into the space between the vertebrae to be fused.

A bone graft is primarily used to stimulate bone healing. It increases bone production and helps the vertebrae heal together into a solid bone. Sometimes larger, solid pieces are used to provide immediate structural support to the vertebrae.

In the past, a bone graft harvested from the patient's pelvis was the only option for increasing the material needed for fusing the vertebrae. This type of graft is called an autograft. Harvesting a bone graft requires an additional incision during the operation. It lengthens surgery and can cause increased pain after the operation.

Most autografts are harvested from an area of the pelvis called the “iliac crest.”

If you are having a decompression procedure, the surgeon may harvest your bone from the site of the decompression and use it as the graft. This type of graft is called a local autograft. The bone is essentially recycled; it is moved from where it is compressing your nerves to the area the surgeon wants to fuse.  

One alternative to harvesting a bone graft is an allograft, which is cadaver bone. An allograft is typically acquired through a bone bank. These tissues are highly processed, and the chance of infection or disease from this tissue is very low.

Illustration of a posterolateral lumbar fusion (PLF) shows bone graft material placed over the transverse processes of the vertebrae. Screws have been placed to provide stability to the spine while the fusion heals. 

Today, several artificial bone graft materials have also been developed:

• Demineralized bone matrices (DBMs). Calcium is removed from cadaver bone to create DBMs. Without the mineral, the bone can be changed into a putty or gel-like consistency. DBMs are usually combined with other grafts and may contain proteins that help in bone healing.
• Bone morphogenetic proteins (BMPs). These very powerful synthetic bone-forming proteins promote a solid fusion. They are approved by the U.S. Food and Drug Administration for use in the spine in certain situations. Autografts may not be needed when BMPs are used.
• Synthetic bone. Synthetic bone grafts are made from calcium/phosphate materials and are often called “ceramics.” They are similar in shape and consistency to autograft bone.

Your surgeon will discuss with you the type of bone graft material that will work best for your condition and procedure.

(Left) This X-ray of the lumbar spine shows decreased disk space between the vertebrae. (Right) In an anterior lumbar interbody fusion (ALIF), a metallic interbody cage has been inserted to restore the normal height of the disk space. The bone graft is contained within the cage and cannot be seen on X-ray.

Immobilization

After bone grafting, the vertebrae need to be held together to help the fusion progress. 

In many cases, surgeons will use plates, screws, and rods to help hold the spine still. This is called internal fixation, and may increase the rate of successful healing. With the added stability from internal fixation, most patients are able to move earlier after surgery. Your surgeon may suggest that you wear a brace to help protect the welding process.

In this X-ray of posterolateral lumbar fusion (PLF), a rod and screws have been used to prevent motion at the spinal segments being fused.

Warning Signs

It is important that you carefully follow any instructions from your doctor relating to the warning signs of blood clots and infection. These complications are most likely to occur during the first few weeks after surgery.

Blood clots. Warning signs of a possible blood clot include:

• Swelling in the calf, ankle, or foot
• Tenderness or redness, which may extend above or below the knee
• Pain in the calf

Occasionally, a blood clot will travel through the bloodstream and may settle in the lungs. If this happens, you may experience sudden chest pain and shortness of breath or coughing. If you experience any of these symptoms, you should notify your doctor immediately. If you cannot reach your doctor, have someone take you to the hospital emergency room or call 911.

Infection. Infection following spine surgery occurs very rarely. Warning signs of infection include:

• Redness, tenderness, and swelling around the wound edges
• Persistent drainage from the wound
• Pain or tenderness
• Shaking chills
• Elevated temperature, usually above 101°F if taken with an oral thermometer

If any of these symptoms occur, you should contact your doctor or go to the nearest emergency room immediately.

Pain Management

After surgery, you will feel some pain. This is a natural part of the healing process. Your doctor and nurses will work to reduce your pain, which can help you recover from surgery faster.

Medications are often prescribed for short-term pain relief after surgery. Many types of medicines are available to help manage pain. Your doctor may use a combination of these medications to improve pain relief, as well as minimize the need for opioids.

Be aware that although opioids help relieve pain after surgery, they are narcotics and can be addictive. Opioid dependency and overdose have become critical public health issues in the U.S. It is important to use opioids only as directed by your doctor and to stop taking them as soon as your pain begins to improve. Talk to your doctor if your pain has not begun to improve within a few days of your surgery. If you are already taking narcotics prior to surgery, talk to your surgeon before your procedure so you can plan your postoperative pain regimen together.

Rehabilitation

The fusion process takes time. It may be several months before the bone is solid, although your comfort level will often improve much faster. During this healing time, the fused spine must be kept in proper alignment. You will be taught how to move properly, reposition, sit, stand, and walk.

Your symptoms will gradually improve, as will your activity level. Right after your operation, your doctor may recommend only light activity, like walking. As you regain strength, you will be able to slowly increase your activity level. Physical therapy is typically started 6 weeks to 3 months after surgery. Your surgeon will talk with you about whether physical therapy is needed in your situation.

Maintaining a healthy lifestyle and following your doctor's instructions will greatly increase your chances for a successful outcome.