Anterior Interbody Lumbar Fusion
The purpose of this letter is to explain what is involved when a fusion is performed on your lower back. We have found that the more knowledgeable the patient, the more successful the outcome.
What is the basic structure of the spine?
The spine is composed of vertebrae, disks, spinal cord and nerves. Typically, the vertebrae are referred to as the “spine.” These vertebrae are strong and bones that support the trunk and protect the spinal cord and nerves. The disk is the soft structure located between the vertebrae. These disks act as cushions which enable the vertebrae to move.
What is a lumbar fusion?
A lumbar fusion is when two or more vertebrae in the low back are “fused” together to create a solid bridge of bone between the vertebrae and across the disk space. A fusion is usually performed to eliminate movement between vertebrae and stabilize a painful or unstable segment of the spine. Once a segment of the spine is stabilized, the patient usually experiences some relief of pain. Surgery is not usually recommended unless there is a more than 70% chance of improving the level of pain. This approximately 70% of improvement does not necessarily mean you will be completely pain free but rather that your level of pain should be significantly improved. It means that there may be significant chance your pain will not improve. However, each situation is unique. There is also a small chance that you may become significantly worse.
Will I lose mobility once a portion of my spine becomes solid bone?
It depends in part on how much of the spine is fused. The spine will not move as much but you will not notice it because it is only a small percent of your spine. Most people believe that the spine enables you to bend over at the waist; this motion actually occurs mostly at the hips. There are patients who have their entire spines fused yet are still able to touch their fingertips to the floor.
What happens during an anterior lumbar fusion?
At the hospital you are taken to the Transfer Area, where an anesthesiologist explains the anesthesia process. You are then taken to the Operating Room and given a general anesthetic to put you to sleep. After you are asleep you are carefully positioned on the table. You may be positioned on your side or on your back, depending on the needs of your particular case. An incision is made through your abdominal muscles. This incision may be directly in the front of your abdomen and may be straight, horizontal or vertical; sometimes it is more towards your flank and somewhat diagonal in direction, depending on which levels of your spine need to be fused and the number of levels involved. The surgery is then done by moving the abdominal contents over and then identifying the great vessels, called the aorta and the inferior vena cava. These are also carefully retracted over the spine. At this point, we are able to look directly at the front part of the spine and we have an excellent look at the disk spaces in the spine. In the usual anterior lumbar interbody fusion, the disk is removed as completely as possible.
The ends of your vertebra are then prepared for a fusion and a spacer or cage is placed to maintain the alignment of your spine while it biologically fuses.
The spacers/cages come in many shapes and materials including bone, metal, plastic and carbon fiber. The particular cage is specially selected based on your particular condition and anatomy.
The material placed into the cage can be your bone, which is usually harvested from your pelvis, cadaver bone, or human recombinant bone morphogenetic protein (BMP). Whichever graft is used, the principle is the same: over time the body will turn the bone graft into a solid piece of bone and eliminate the movement between the vertebrae.
How is an anterior lumbar interbody fusion different from a posterior lumbar fusion?
In a posterior lumbar fusion, the fusion is done through the back part of the spine. The muscles are dissected from the spine. The bony surfaces of the spine are exposed and small pieces of bone are laid across the back part of the spine. In an anterior fusion, the surgery is done through the front part of the spine, which makes it necessary for us to go through your abdomen. Instead of using chips of a bone graft to span the space, a solid piece of bone is generally used, in the form of a shaped bone graft or metal cage filled with bone or BMP. In the anterior fusion, the bone graft is packed directly between the vertebral bodies, whereas in the posterior fusion the bone is laid across the back part of the spine. It is generally felt that if one can obtain a solid anterior fusion there is a mechanical advantage, in that most of the force of the spine is directed through the front part of the spine.
When is an anterior fusion chosen instead of a posterior fusion?
An anterior fusion is chosen for several reasons. Your surgeon may feel that with your particular situation that an anterior fusion is a better way to obtain fusion. However, anterior fusion is also used in addition to a posterior fusion to obtain a higher percent of fusions. In certain spinal deformity situations, multiple disks are removed from the front of the spine to “loosen up” the spine and improve the correction of the deformity.
What is a “cage?”
A cage is a device that has threads on the outside. There are special tools to create the appropriate holes in the front part of the spine and then the cages are then put into the spine. At this point, the vertebrae are being held apart by a hollow cylinder (the cage) that has holes on the outside. The bone graft is then packed into the middle part of this cage and there is direct contact between the rough bony surfaces of the vertebrae and the bone graft through cage. This contact allows the fusion to occur. There are several brands of cages, but they all use basically the same principles. They may be made of different types of materials, such as carbon or titanium.
Why are cages used?
Once the cages are in position, they give remarkably good fixation. This seems to alleviate the back pain quite quickly, as there is very little motion between the vertebrae after the cage is in place. It has also been documented that the fusion rate seems to be quite high. Without the cages, historically the fusion rate has been around 60-70%. At this point, it is felt that the fusion rate with the cages is 90%
Are there any specific risks in using the cages?
There are several risks of anterior lumbar fusions that we will discuss below. The only additional risk of using the cage in anterior lumbar fusion is that if the cage is placed too far backwards or too far to the side it can damage a nerve root. This is a rare complication and can be solved if the cage is removed. If the fusion does not take and the cage must be removed, then this can be a challenging procedure. Often, however, the nonunion can be solved by doing a procedure from the back and leaving the cage in place.
Does smoking have an affect on my fusion?
Research shows that the healing rate is greater than 90% in nonsmokers and less than 50% in smokers. It appears that with the cage technology the difference is not quite as great but there is still certainly a lower fusion rate in patients who smoke. In addition, there is a higher infection rate in people who smoke. Many surgeons will not perform a fusion in patients who smoke because of the higher rate of nonunion and infection. Physicians have also found that it is sometimes necessary to go through both the front and the back of the spine to obtain a successful fusion in smokers. If you smoke, be prepared to discuss the situation in detail with your physician.
What will my hospital stay be like?
You will check into the hospital approximately two hours before surgery. Several nurses and doctors will ask you questions regarding you medical history. It would be helpful to bring a list of medications that you are currently using. You will wait in the holding area of the operating room for about 30 minutes before surgery. This is where you will meet your anesthesiologist and have your IV’s initiated. After surgery you will wake up in the Recovery Area where you will remain for about 2 hours. There will be a catheter in your bladder. The catheter is usually removed on the second day. However, if you are unable to urinate you may need to be recatheterized. Due to the anesthesia and medications, many patients have a poor recollection of this time period.
The first 2 days will be difficult. We will try very hard to keep you as comfortable as possible with IV pain medicine. You will be ale to control the amount of pain medication you receive by using a small push button. You can push the button as often as you need; the machine will control the dose. We have been very happy with the amount of pain control we can obtain with this machine.
The combination of pain medicine, anesthesia, and spine surgery may cause you to experience some nausea. We allow only ice chips or small amounts of liquids until you are passing gas. If fed too soon, you may become distended and even more nauseated. About 20% Anterior Interbody Lumbar Fusionof our patients are fairly nauseated within the first 24 hours. This problem is usually resolved by the second or third day. We encourage you to get out of bed on the first day.
When can I shower?
The drains are usually removed on the first or second day. You may shower with the dressings in place or off, depending on the preference of your doctor, on the second or third day. There are small tapes on your skin that you will need to pull off after the tenth day. The sutures do no need to be removed as they will eventually be absorbed into the skin.
When can I go home and what will I be able to do?
You may go home once your pain can be controlled with pills, your incision is not draining, and your bowel and bladder are functioning normally. Most patients are ready to go home by the third or fourth day after surgeryWithin the first few weeks following discharge we encourage you to begin walking for one half hour to two hours each day. If you were given a brace, you must wear it during the day although you can remove it to sleep or shower. You should be able to go up and down stairs, drive, and perform basic daily activities without too much of a problem. You should avoid bending at the waist as that increases the stress across the fusion site. It usually takes a minimum of four months for the fusion to heal. The time frame in which you can return to work depends on your recovery. Each patient has a unique set of work related issues which will need to be discussed with the doctor.
The first office visit should be scheduled two to four weeks after you are discharged. The purpose of this visit is to check your incision and make sure you are progressing as planned. The second visit is typically scheduled two to four months after surgery. During this visit the status of your fusion is assessed.
Will I need a blood transfusion?
A spinal fusion is a major surgery which may require a blood transfusion. However, if you are having just a one-or two-level anterior fusion, the blood loss has been shown to be quite minimal. We have generally not had people predonate blood for just an anterior fusion. However, if the fusion is being done in conjunction with a posterior fusion, then a blood transfusion may be required. The blood bank is very safe; the risk of contracting AIDS is less than one in 500,000 and the risk of contracting hepatitis is one in 100,000. Prior to surgery, our office can arrange pre donations through blood bank if necessary.
What are the specific risks of this operation?
Every surgical procedure carries significant risks. These include major risks which my have long-term or negative side-effects and minor risks which do not have any long-term effects.
Deep Infection: 1-2%
These include infections which may show up several months after surgery and require multiple surgeries and prolonged use of antibiotics.
A pseudarthrosis or non-union is a term used to describe a fusion that has not healed. This means that a solid bridge of bone has not formed between the vertebrae. A non-union does not necessarily mean that the surgery must be redone; many patients with a non-union are quite happy with their pain relief. However, in cases where the pain persists, the fusion may have to be redone. We have found that smokers have a higher incidence of pseudarthrosis(>50%) than non-smokers. Therefore, you should be aware that smoking can significantly affect the outcome of your surgery.
Dural Tear: <1%
Generally a dural tear can occur in conjunction with a posterior procedure. It would be unusual to encounter this complication from the front. To heal properly you must remain flat on your back for 24 to 72 hours, so that the leak will seal. If the leak persists, you may require further surgery or special drains.
Nerve Damage: 1-2%
Nerve damage can occur in the front part of the spine if the cage is placed too far lateral to the vertebrae, which would put it very close to the nerve. This generally causes pain but occasionally causes numbness or weakness as well as pain. It would be rare to have the catastrophic complication of lost bowel or bladder function, but it is possible if the disk material is pushed straight back into the spinal cord.
Further surgeries may be necessary if the hardware breaks or loosens. Other reasons include nerve impingement from a screw, pseudarthrosis (non-healing of the fusion), infection, other disks degenerating, or persistent pain.
Major organ or vessel damage:
With the anterior procedure there is the additional risk of perforation of the aorta or inferior vena cava. These are major vessels and this could cause major blood loss. Generally this can be stopped in surgery and repaired. In very rare instances, this major bleeding could lead to death. It is also possible to damage the tubes coming from your kidney to your bladder, which would require additional surgery to repair.
Sexual Dysfunction (males): less than 1%
In males, functional sterility can occur. This arises from retrograde ejaculation. The male is able to have normal sexual function and sperm production, except that the ejaculation does backwards instead of forwards. There is still full sensation but sterility can occur. Most instances of retrograde ejaculation are temporary, resolving in 6 to 12 months. Occasionally it can be a permanent situation. Impotence is a rare complication of this surgery.
Persistent pain at the bone graft site: 25%
Generally the bone graft site seems to have the most pain after surgery. This is because the major gluteal muscles attach to the pelvis and when you walk this pulls on the area that is sore. This usually resolves within three to four weeks. Occasionally however, this is a very persistent, long-term problem. Partially due to this risk your doctor may recommend the use of bone morphogenic protein for your fusion.
Complications which are less serious include bladder infection, superficial wound drainage, inability to urinate for a few days, nausea, headache, constipation, abdominal bloating, sore throat, pneumonia, and reactions to medications. If your body is unable to replenish its blood supply or if too much blood is lost during surgery, a blood transfusion may be necessary. As with any surgery, there are also unanticipated major and minor risks.
What is your overall philosophy regarding spinal fusion?
Lumbar fusion is generally an elective surgery. Therefore, it is your choice to proceed based on your current level of discomfort and disability. We recommend that you do not have surgery if you can live with your current level of pain or can make changes in your lifestyle to decrease the pain. If you have made a valiant effort and the pain still persists, surgery should be your next step.
The rate of surgical success varies greatly depending on your exact problem, overall health, and the magnitude of surgery necessary. We hope that by providing you with as much information as possible about the surgery, you can determine if the pain you are experiencing is worth the risk of surgery.
Patients often ask if the purpose of this letter is to provide the surgeon with legal and medical protection. This is true; however, the main goal of this letter is to provide you with as much information as possible to assist you during your decision-making process. We believe that patients who are more informed about the procedure are less anxious and apprehensive with their surgery. These patients usually experience less pain and have a better outcome overall.