Lateral Lumbar Interbody Fusion

Abstract

Minimally invasive lateral retroperitoneal transpsoas approach for lumbar interbody fusion is the fastest growing type of minimally invasive spinal fusion in the United States. We prefer to perform the psoas dissection under direct visualization, in order to protect sensory nerves not detected by neuromonitoring, and insert the widest cage possible, typically 22 mm. We use either lateral plating or posterior percutaneous instrumentation to increase stability and maximize fusion rates.

Electronic Supplementary Material Lateral lumbar interbody fusion (LLIF) electronic supplementary material

L4–5 LLIF. The psoas muscle is fibrous and difficult to dissect. The femoral nerve is exposed during the procedure (an uncommon occurrence) and therefore the retractor has to be repositioned. Angled instruments are used to access the disc in this patient with a high iliac crest (MP4 77880 kb)

L4–5 LLIF. A far lateral disc herniation is removed via this approach, prior to re-docking and performing the fusion (MP4 30032 kb)

L4–5 LLIF. The femoral nerve is exposed in the middle of the disc and cannot be mobilized posteriorly. A rare, behind-the-femoral-nerve LLIF is performed (MP4 37533 kb)

L4–5 LLIF. The genitofemoral nerve is encountered and protected during the transpsoas approach. The psoas has a normal consistency (MP4 8516 kb)

L4–5 LLIF. The genitofemoral nerve is encountered and protected during the transpsoas approach. The psoas is soft and easy to dissect (MP4 5352 kb)

Addendum: Informative Letter to the Patients

The following informative letter is NOT intended to cover ALL the possible complications and scenarios. It is only intended to serve as a general guide, to improve patients’ understanding of the operation.

This procedure can be very long. Despite careful padding of all pressure points, abrasions and pressure sores can occur. Generally these are minor, but can be serious, especially if they occur on the face. Nerve damage, particularly at the joints, can also occur. Blood clots forming in the legs, with potential death from spread to the lungs, are always a worry, and we use special inflatable devices to minimize that risk. Blood loss during this kind of surgery is normal and unavoidable, and sometimes we need to give transfusions from the blood bank. All of the blood is carefully tested, but unfortunately no test is perfect and there is always a small risk of acquiring some disease, such as hepatitis or AIDS. Death from anesthesia reaction or massive blood loss is possible, but fortunately extremely rare.

We make a one-inch skin incision on the side, just above the hip bone, usually on the left. Before we go through the abdominal wall, we use this incision to take a small amount of your bone marrow from the hip bone, to concentrate it and use it for the fusion. Rarely, you may experience pain and soreness at the site where bone marrow has been harvested. Damage to small nerves in the area can lead to numbness or even pain towards the thigh or groin area.

We then dissect the muscles in the abdominal wall to get to the abdominal cavity. Sometimes, this may cause pain and/or numbness in the groin or anterior thigh. Using our fingers, we then sweep the bowels and abdominal organs out of the way and reach the spinal column with a small retractor, under X-ray guidance. At this point, an operating microscope is used to allow us to keep the incision as small as possible, yet have excellent vision so we can see what needs to be done. In order to get to the spine, we have to go through a thick muscle called psoas. There are several nerves in this muscle. We try to protect these nerves by doing the dissection under direct visualization and also by recording any abnormal electric potentials that appear when the nerves are stimulated. Nonetheless, it is very common in the first 3 months after surgery to have pain and/or paresthesias over the thigh or groin. Sometimes, when the larger nerves are stretched or damaged, you may have weakness in the leg, especially when trying to straighten out your knee. While most of these changes resolve by 3 months after the surgery, sometimes they persist forever. Another potential complication (but fortunately very rare) is injury to the bowels, kidney, or large vessels; these may require opening the abdomen widely (usually by a general surgeon) and may result in serious damage and even death.

Once we get to the side of the spine, we then remove the bad disc or discs and prepare the area to accept the fusion construct. After we take out the disc, we replace it with a synthetic box we call “cage” that is filled up with bone graft and will promote the bony fusion. We are careful to avoid damage to the nerves in the spinal canal, which are very close to our “working area”. However, such damage (while very rare) is a risk and can result in paralysis from nerve damage, loss of bowel, bladder, and sexual function, numbness, lack of feeling or sensation, or even severe pain below the waist. X-rays are used throughout the procedure to maximize the safety.

In order to give instant strength and stability to the spine and to increase the probability of the natural bony fusion healing properly, we use either a lateral plate (that can be inserted through the same incision) or screws and rods (that have to be inserted through two 1-in. incisions in the back). We place the screws accurately with the aid of intraoperative X-ray guidance. Nerve or blood vessel damage is possible, but fortunately quite rare. These devices function as an internal cast to keep the spinal bones immobile while the bone cells are forming the fusion mass. (If you’re gluing two pieces of wood together, the glue is more likely to stick if you keep the wood pieces in a vice until the glue is set.) The screws and rods have been engineered and designed for endurance, but if a natural bony fusion does not form, eventually they will work loose or break. Another risk of any type of implanted foreign (non-natural) body is the possibility of infection. If this occurs (which is rare) it is early, and not months or years later. Generally removal of the screws is not necessary (to treat the infection), but prolonged antibiotics and debriding (cleaning up) procedures could be required.

It is important that you understand that this is a serious and possibly painful operation with a long and slow recovery. Most frequently, after the surgery you will be moved from the recovery room to a normal hospital room. Occasionally, if the surgery takes longer than a few hours, you may need to be monitored in the intensive care unit. Sometimes the intestines are sluggish for a few days and until you begin to “pass gas”, your intake of food may be restricted. We encourage you to walk with assistance as soon as possible, and it is hoped that the total hospital stay will be in the range of 1–4 days. Of course, this is varied as needed on an individual basis.

At home we would encourage a program of walking on a level surface, gradually increasing the distance to between 2 and 3 miles a day. At about 3 months, a home exercise regimen can be cautiously started. Return to daily activities is highly variable, but in general it is sometimes possible to return to the equivalent of a light office type job at about that time (3 months). Maximal medical improvement is generally reached around a year after the date of surgery. It is generally not possible to engage in heavy manual labor type occupations following an operation of this nature.

Over the 6–12 months after surgery, it is hoped that the operated discs will heal and grow into a strong bony mass, so as to cause a solid union between the bones. This is a gradual process and at first there is no increased strength. This healing process is dependent upon the patient’s powers of healing and does not always occur properly. The use of nicotine in any form (cigarettes, smokeless tobacco, nicotine patches, or nicotine gum) interferes with bone healing and dramatically decreases the odds of a successful fusion. You should not smoke or use nicotine in any form! Generally about 3 months is required for the fusion to begin to set, but strengthening continues for about a year or more. Also, for the first several months after surgery it is best to avoid non-steroidal anti-inflammatory drugs (such as aspirin, Motrin, Aleve, Naprosyn, etc.). These medications may interfere with bone healing. Tylenol use is OK, but you should be careful not to exceed the recommended dose. We expect to achieve a successful fusion for one disc level in about 90% and for two levels in about 80%. Sometimes postoperative X-rays show that the fusion has not healed to form solid bone. Most of the time, this does not seem to matter because a tough scar tissue-like gristle has formed instead and there are no symptoms. Occasionally, however, the failed fusion is symptomatic. That is called a pseudoarthrosis and repeat surgery is sometimes required. The type of surgery in those cases depends on individual circumstances.

Major complications (life threatening) may occur in about 2% of cases. The most common major complication is implant malposition or migration and may require reoperation. Sudden massive blood loss could occur, resulting in death. Other major complications include pneumonia and pulmonary embolism (blood clot going to the lungs).

There is also the chance that another type of fusion operation will be required if this one does not heal solidly. For example, it might be necessary to perform an additional operation in the back or front of the spine, with more bone graft added at that time.

One last potential problem after fusion surgery is what we call “juxtafusional disease”. After you have had a successful spinal fusion, that segment becomes immobile and the joints above and/or below that fusion are subjected to increased stress. Over the years, these joints can have problems that may require further surgery.

It is very important to emphasize that no operation or device is a “spine transplant”. Results on an individual basis cannot be predicted, and therefore we certainly cannot give any guarantees or promises. Once you have a bad back, you always will have a bad back to some degree. You could be no better, or even worse. Most patients indicate that on average the pain is improved from “marked” to “mild”. While this is a great improvement, it is usually not improved to “occasional” or “none”. Whether you will be able to return to their pre-injury or preoperative level of functioning will have to be determined on an individual basis. As a general rule, it is about a year before patients are “over” the operation because recovery and reconditioning is a slow process. It is sometimes necessary to call upon the Departments of Physical Medicine & Rehabilitation and Occupational Medicine to perform functional capacity evaluations (FCE) to determine a patient’s actual limitations and abilities.

My general advice to anyone with a spinal affliction of this nature is to “live with it” (if possible). Of course that’s easy for me to say because I’m not the one hurting. This operation has been recommended in the belief that your condition is serious and therefore taking the risks of surgery makes sense. I believe this is a good operation that is the best choice for your particular problem. If your only affliction is pain, the decision is yours and yours alone as to whether you can live with it. While I obviously hope and believe that this operation will help you, I cannot give any guarantees or promises about results. It is possible that you could be the same or even worse. Furthermore, my general recommendation is to “live with it” if possible and avoid the risks and uncertainties of surgery. Nevertheless I am offering my surgical services in an attempt to help you, but the decision to proceed is up to you.