Spinal Fusion: Lateral Lumbar Interbody Fusion (LLIF)Open print version


Lateral interbody fusion is a minimally invasive surgery to treat disc problems in the low back. In spinal fusion, two or more bones of the spine are joined to stop painful motion, decompress pinched nerves, and correct scoliosis. Through a small incision at the side of the waist, the disc is removed and a bone graft is inserted to restore the height and relieve nerve pinching. During healing, the bones will fuse together. Patients typically go home the same day; recovery time takes 6 to 12 weeks.

Figure 1. (side view) A collapsed degenerative disc pinches the nerve between the bones, causing back pain and instability.

What is lateral spine fusion?

When back and leg pain result from injury or degenerative changes in the spine (Fig. 1), a lateral lumbar interbody fusion (LLIF) may be recommended. Fusion stabilizes the spine and prevents painful motion. The surgery is sometimes called DLIF, which stands for direct lateral interbody fusion, or XLIF, for extreme lateral interbody fusion. Both refer to the same technique.

During lateral fusion, an incision is made at the side of the waist. The damaged disc is removed and the space between the bony vertebrae is filled with a spacer bone graft. The spacer restores the height between the bones and relieves pinching of the spinal nerves. The graft becomes a bridge between the two bones to promote fusion. In some cases the graft is strengthened with a plate and screws on the side or with pedicle screws from the back.

As the body begins healing, new bone cells grow around the graft. After 3 to 6 months, the bone graft should fuse the two vertebrae, forming one solid piece of bone. Like reinforced concrete, instrumentation and fusion work together.

Depending on the symptoms, a one-level or multi-level fusion may be performed. A one-level fusion joins two bones while a two-level fusion joins three bones.

Figure 2. Through an incision made at the waist, lateral fusion (DLIF, XLIF) reaches the spine from the side. The disc is removed and replaced with a bone graft. Lateral fusion is an alternative to ALIF and TLIF surgeries.

Lateral spine fusion is a unique minimally invasive surgery for several reasons. First, the small incision is only 1 inch long near the waist. Second, its path to the spine is from the side (Fig. 2). The surgeon uses dilation tubes to create a tunnel between the patient's abdominal organs in front and the strong spine muscles in back. Third, a nerve-monitoring probe guides the path to safely enlarge the tubular instruments without injuring the spinal nerves. Lateral fusion can be performed in a hospital or as an outpatient same-day procedure.

Other types of spinal fusion surgery used to treat disc problems include ALIF, TLIF, PLIF, and AxiaLIF, each with its own advantages and disadvantages.

Who is a candidate?

You may be a candidate for LLIF if you have:

  • degenerative disc disease
  • low-grade spondylolisthesis
  • mild to moderate scoliosis
  • symptoms that have not improved with physical therapy or medication

You are not a candidate for LLIF if you have:

  • damaged disc at L5-S1, because the hip bone blocks access
  • severe spondylolisthesis or scoliosis
  • other problems that would prevent bone fusion
  • prior abdominal surgery near the kidneys

Fusion may be helpful in treating:

  • Degenerative disc: with age the discs dry out and shrink. As the disc spaces get smaller, these changes can lead to stenosis or disc herniation that pinches nerves (Fig. 1).
  • Spondylolisthesis: a forward slip of a vertebra out of alignment with the spinal column. It can kink and compress the nerves, causing pain.
  • Spinal stenosis: narrowing of the spinal canal and nerve root canal, along with enlargement of the facet joints, can pinch spinal nerves and cause pain and numbness in the legs.
  • Scoliosis: with age or previous spine surgery, the bony vertebra may move out of alignment, causing the spine to develop an abnormal side-to-side curvature.

The surgical decision

If you are a candidate for spinal fusion, the surgeon will explain your options. Consider all the risks and benefits as you make your decision. Fusion is performed only after other treatments have been explored. It will stop the motion in the painful area of your spine, allowing increased function and return to a more normal lifestyle—though one that may not be totally pain-free.

Your surgeon will also explain the various types of bone graft. These materials are placed within the remaining disc space and act as a kind of mortar between the bones as your body heals. Each type has advantages and disadvantages.

  • Autograft is your living bone. The marrow contains bone-growing proteins. It can be collected from drillings during the surgery or taken from the hip as an iliac crest bone graft. The harvested bone is about a half inch thick. The entire thickness of bone is not removed
  • BMA (bone marrow aspirate) is your living bone marrow, collected with a syringe from the hip (iliac bone) or vertebra. It is relatively painless compared to an iliac crest graft.
  • Allograft is bone from an organ donor, collected and stored by a bone bank. The donor graft has no bone-growing cells.
  • BMP (bone morphogenetic protein) is sometimes added to bone-graft material to stimulate bone growth naturally in the body.

Who performs the procedure?

A neurosurgeon or orthopedic surgeon can perform spine surgery. Many spine surgeons have specialized training in minimally invasive surgery. Certain minimally invasive techniques are highly technical; they require special instruments and training to avoid complications. Ask your surgeon about his or her training, especially if your case is complex or you have had previous spinal surgery.

What happens before surgery?

Presurgical tests (e.g., blood test, chest x-ray, electrocardiogram) will be done several days before surgery. In the doctor's office, you will sign consent forms and provide your medical history (allergies, medicines/vitamins, bleeding history, anesthesia reactions, previous surgeries). Inform your healthcare provider about all the medications (over-the-counter, prescription, herbal supplements) that you are taking.

Continue taking the medications your surgeon recommends. Stop taking all non-steroidal anti-inflammatory medicines (Naprosyn, Advil, Motrin, Nuprin, Aleve, etc.) and blood thinners (Coumadin, Plavix, etc.) 1 to 2 weeks before surgery as directed by your doctor. Ask your doctor if you are unsure.

Stop smoking and drinking before surgery

The most important way to achieve a successful spine fusion is to eliminate tobacco use (cigarettes, cigars, pipes, chewing tobacco, and snuff / dip) before surgery.

Nicotine prevents bone growth and decreases successful fusion. Smoking risk is serious: fusion fails in 40% of smokers compared with 8% of non-smokers [1]. Smoking also decreases blood circulation, resulting in slower wound healing and increased risk of infection. Talk with your doctor about ways to help you quit smoking: nicotine replacements, pills without nicotine (Wellbutrin, Chantix), and tobacco counseling programs.

You should not drink alcohol 1 week before and 2 weeks after surgery to avoid bleeding problems.

Morning of surgery

  • No food or drink.
  • Shower using antibacterial soap. Dress in freshly washed, loose-fitting clothing.
  • Wear flat-heeled shoes with closed backs.
  • If you have instructions to take regular medication the morning of surgery, do so with small sips of water.
  • Remove make-up, hairpins, contacts, body piercings, nail polish, etc.
  • Leave all valuables and jewelry at home (including wedding bands).
  • Bring a list of medications (prescriptions, over-the-counter, and herbal supplements) with dosages and the times of day usually taken.
  • Bring a list of allergies to medication or foods.

Arrive at the hospital 2 hours before (outpatient surgery center 1 hour before) your scheduled operation to complete the necessary paperwork and pre-procedure work-ups. An anesthesiologist will talk with you and explain the effects of anesthesia and its risks. An intravenous (IV) line will be placed in your arm.

What happens during surgery?

This surgery generally takes 1 to 2 hours, depending on how many spine levels are treated.

Step 1: prepare the patient

You will lie on the operative table and be given anesthesia. Once asleep, you will be positioned on your side; the waist area is cleansed and prepped.

Figure 3. (front view) A 1-inch skin incision is made at the waist, and a corridor (green area) is opened to the disc.

Step 2: make the incision

A small 1- to 2-inch incision is made at the waist (Fig. 3). The surgeon gently makes a path between the abdominal cavity and the back muscles through the retroperitoneal space. This area contains fat as well as the kidney and colon, which are gently moved aside.

Figure 4. (cross section view) Using tubular dilators, the surgeon makes a corridor behind the abdominal wall through a fat-filled area called the retroperitoneal space. A monitoring probe detects the position of nerves along the side of the spine, and helps guide a safe path through the psoas muscle to the disc.

Step 3: locate the damaged disc

A monitoring probe is inserted to detect the nerves that form the sciatic nerve. Looking at the fluoroscope (a special x-ray), the surgeon carefully passes a long tube along the path through the psoas muscle to the disc (Fig. 4).

Figure 5. The disc is removed with tiny instruments through the tube retractor.

Step 4: remove the disc

Next, a series of dilator tubes are passed, one around the other, to separate the muscles and create a tunnel to the spine. Working through the tube, the surgeon removes the damaged disc (Fig. 5).

Step 5: prepare the disc space

The open disc space is measured and an appropriate sized spacer or bioplastic cage is selected. Progressively larger spacer trials are slid into the space to reopen the height and decompress the nerves. When height has been restored, the permanent spacer is prepared with bone graft.

Bone marrow is taken from the iliac crest with a syringe (or by incision) and then mixed with other graft material. The mortar-like paste contains bone-growing proteins that are packed into the spacer cage.

Figure 6. A spacer bone graft is inserted to restore the collapsed disc height, realign the bones, and relieve pinching of nerves.

Step 6. insert the bone graft

Guided by x-ray fluoroscopy, the spacer graft is inserted into the empty disc space, pushing the two bones apart to restore normal disc height (Fig. 6 and 7).

Figure 7. (front view) X-ray sequence shows opening of the disc space and increase in height as the bone graft is inserted.

Step 7. insert plate and screws (optional)

The spacer graft may be held in place with a metal plate screwed into the side of the vertebrae, or with screws and rods from the back. The hardware provides stability during fusion.

Step 8. close the incision

The tubes and instruments are removed. The skin incision is closed with Steri-Strips or biologic glue.

What happens after surgery?

You will awaken in the postoperative recovery area. Your blood pressure, heart rate, and respiration will be monitored. Any pain will be addressed. Once awake, you can begin gentle movement (sitting in a chair, walking). Most patients having a 1- or 2-level LLIF go home the same day. However, if any difficulty in breathing or unstable blood pressure occurs, the patient can be transferred to a hospital.

Discharge instructions


1. After surgery, pain is managed with narcotic medication. Because narcotic pain pills are addictive, they are used for a limited period (2 to 4 weeks). As their regular use can cause constipation, drink lots of water and eat high-fiber foods. Laxatives (e.g., Dulcolax, Senokot, Milk of Magnesia) can be bought without a prescription. Thereafter, pain is managed with acetaminophen (e.g., Tylenol).


2. If you had a fusion, do not use non-steroidal, anti-inflammatory drugs (NSAIDs) (e.g., aspirin; ibuprofen, Advil, Motrin, Nuprin; naproxen sodium, Aleve) for 3 months after surgery. NSAIDs may cause bleeding and interfere with bone healing.

3. Do not smoke. Smoking delays healing by increasing the risk of complications (e.g., infection) and inhibits the bones' ability to fuse.

4. Do not drive for 2 to 4 weeks after surgery or until you have talked with your surgeon.

5. Avoid sitting for long periods of time. Do not bend or twist at the waist.

6. Do not lift anything heavier than 10 pounds (e.g., gallon of milk).

7. Housework and yardwork are not permitted until the first follow-up office visit. This includes gardening, mowing, vacuuming, ironing, and loading/unloading the dishwasher, washing machine, or dryer.


1. Postpone sexual activity until your follow-up ap