Axialif is short for Transxial ALIF. Transaxial means that the procedure is performed along an axis perpendicular to the disc. ALIF is short for Anterior Lumbar Interbody Fusion (causing two vertebral bodies to grow together from an anterior approach). It is a completely novel approach for an otherwise long-standing familiar operation. An approach that is far less invasive compared to other techniques. There is almost no tissue damage and the normal anatomy of the spine is not changed or impaired.
The transaxial route can be used for almost all patients in case fixation of the lowest lumbar vertebra to the sacrum is considered. Usually these are patients with back pain due to a degenerated disc, so called discopathy. It should be stressed that a symptomatic disc is the reason for back pain only in a minority of all patients suffering from back pain. The operation is also suitable for patients with pain originating from the small facet joints between the vertebral bodies.
Back pain is one of the most common conditions in any population. The costs for treatment and absence from work are tremendous. A search on the internet will provide thousands of sites with information of variable and uncontrollable quality. For the lay person it is almost impossible to find his way in this information jungle. Complaints arising in the spine, the pelvis or their junction are often poorly understood, leading to fancy sounding but meaningless "diagnoses" like "tension myositis syndrome", "sacro-ileacal syndrome", "pelvic instability" etc. In view of the uncertain diagnosis there is a multitude of treatments, including many that are both ineffective and unproven.
In this text we would like to clarify some issues. There are many ways of classifying back pain. A distinction can be made in acute and chronic, in pain with and without demonstrable cause, in treatable and resistant to treatment etc. The distinction is not easy because there is overlap between the various classifications.
The lumbar spine consists of 5 vertebral bodies. Below it is the sacrum. In some people (about 10%) there are variations. The fifth vertebral body can be fused with the sacrum (sacralisation) or, on the other hand there can be a separate first sacral body (lumbalisation). These variations have no special significance, they are only important for orientation. So when naming segments we can see: L5/S1 but also L4/S1 or L6/S1.
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| Lower lumbar spine and sacrum. | Anterior side of the sacrum. The safe zone for the operative approach is between the openings. |
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| Sagittal cut. The black line is the position for the Axialif rod. | Sagittal cut. The procedure is done along the red line. The layer of fat tissue in front of the sacrum is clearly visible. |
On the anterior surface of the sacrum there are no significant structures. The large blood vessels split above the disc space. Between the sacrum and the bowel there is a layer of fat tissue of approximately 1,7 cm. There is a safe pathway to gain access to a point from where the center of the disc can be reached. This point is about 2 to 3 cm below the disc and due to the angle of the sacrum it is below its center.
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| The large blood vessels (here only the veins are visible, but the arteries run along with them) split above the disc space. The red line is the safe route for the operation. |
Signs of ageing, degenerative changes or "wear" are a normal process, taking place in every human to a more or lesser extent. To which extent is probably largely determined by genetic predisposition, which explains the fact that some families seem especially affected. Wear by activities or work is probably caused less than often thought, although it is true that back pain can occur more with certain activities. Smoking is a known cause of accelerated disc degeneration. This degeneration often begins with dehydration of the disc. This is seen on an MRI scan as a black disc, as the water causes the image to be more white.
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Left an MRI of the lower spine showing the central cut. The disc between the sacrum and the fifth lumbar vertebra is dried out with a black appearance and decreased height. The white changes in the bone reflect a reaction to the degeneration, described by Modic and named after him as Modic changes. The disc above has a completely normal appearance. This is classified as discopathy L5/S1. |
Acute back pain. This is the most well known type of back pain. It is a severe sudden pain in the lower spine, often without any obvious cause, or after having stood in an uncomfortable position. The cause is thought to be small tears in the ligaments around the spine or in the disc. The pain can be very severe, but usually diminishes after one to two weeks. Pain killers offer relief for pain, but there is no known proven effective treatment. If the pain does not subside and the condition becomes chronic, treatment can become problematic. Sometimes the acute back pain is followed by radiation into the leg, as is the case in a herniated disc.
Symptomatic back pain. This is back pain originating from some known underlying cause like infection, tumor, severe degeneration or rheumatic disease.
Non specific back pain. This is the largest and by far most difficult group of patients, as a clear underlying cause cannot be demonstrated. Investigations like X-ray and MRI will often prove normal. Treatment is often a matter of trial and error. Sometimes the only treatment consists of a program teaching the patients how to handle their pain rather than trying to relieve it.
Seven myths about herniated disc and back painIn the Spine Journal (Vol. 29 nr.16 p. 1818-1822) the following statements are debunked:
Mind you: all of these statements are not true!! |
Causing two vertebral bodies to grow together, spinal fusion, can be done at any level and with any number of vertebral bodies in the spine. The most frequent levels are those in the neck and lumbar spine. The lowest segment with an intervertebral disc is called the lumbosacral junction. To fuse this segment three techniques have always been available:
the anterior approach. In this procedure an access is made through an incision in the lower abdomen to the front or side of the segment. The disc is cleared out as much as possible and the disc space is filled with bone, cages or a combination. These cages can be made of titanium, carbon or a polymer (PEEK). They may or may not be supplemented with screws. The goal is for the bone to grow together, a process that can take 2 to 3 months.
the posterior approach. In this procedure screws can be inserted into the pedicles of the vertebral bodies, connected by rods. Bone can be applied along these rods. It is also possible to remove the disc via this approach, as is common in a herniated disc. The disc space can then be filled with bone or cages. There are many systems on the market with similar characteristics. It is usually according to the preference of the surgeon which system is used.
combined approach. Some surgeons prefer to perform the fusion from both sides, the circumferential fusion. It may be the most radical approach, but it is certainly a big operation.
The transaxial approach has so far not been used for any procedure. Surgeons are therefore not familiar with the local anatomy. In the common textbooks the area in front of the sacrum is hardly described. Now we know there is a safe pathway with a width of about 2,5 cm to a point below the disc space, provided a close contact with the sacrum is kept at all times.
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| Patient positioning during the procedure. | Slowly proceed upwards with the blunt instrument until the ideal position is reached. |
The access is a 3 cm incision in the midline over the coccyx (tail bone). The optimal site is determined using X-ray fluoroscopy. Then the fascia just adjacent to the coccyx is perforated, entering the presacral space. Under fluoroscopy a blunt instrument is advanced along the anterior surface of the sacrum, observing the midline, up to a point from where the center of the disc can be reached. Depending on the anatomy this can sometimes be difficult. Some patients have a very steep sacrum, in others it is very curved. When fluoroscopy in two planes has confirmed a correct position a 3 mm sharp wire is advanced up to the disc space. A correct position of the wire guarantees a correct route for the further procedure (animation).
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| With a cutter made from memory metal in various lengths the disc space can be cleared. | For bone growth to take place it is important that the endplates are scraped clean. |
Over this wire dilator tubes are inserted to create an opening in the sacrum large enough to accommodate the 10 mm working channel. Through this channel the disc space is cleared using metal cutters, a loop that can be turned around, and steel brushes. The endplates should be well scraped off to allow for a surface that bone can grow in to (animation). After clearing as much as possible the disc space is filled with a mixture of bone, bone substitute and bone marrow (animation). Then a hole is drilled halfway the fifth lumbar vertebra.
After determining the size for the rod the working channel must be exchanged to allow for the passage of the larger rod. After that the rod can be inserted (animation). The rod has a variable pitch for the two halves, causing it to provide for some distraction as the rod is screwed into position. This creates a bit more room for the exiting nerve roots, although it is not always necessary.
The whole procedure takes about 40 minutes. There is only a small wound to close.
If you have a broadband internet connection you can watch this film clip.
Before the operation the bowels will be emptied with the aid of an enema. It is not strictly necessary for the operation, but it is comfortable for the patients in the days thereafter. There is no further preparation necessary.
After the operation patients can quickly be mobilized and leave the hospital. Pain is not very significant and compared to "a kick in the butt". Because recovery is so quick patients tend to forget that nothing less than a fusion procedure has been performed and it is important to remember that. This means that in the first 6 to 12 weeks they should refrain from sports, lifting and bending. At the first outpatient visit an X-ray will show if fusion has begun to take place.
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| Image after the operation. Observe the oblique position of the rod. This is due to the slightly off-midline approach, but it is also the desired position. In this way rotation of the vertebral bodies over the rod is prevented. | Image in a lateral view. Observe the bone formation in the disc space around the rod. | This CT-scan (after one year) clearly demonstrates fusion. The rod has completely been incorporated into the bone. |
The operation has few risks. Certainly for such a new procedure the number of complications worldwide has been exceptionally low. Especially worth mentioning is the fact that the risk of nerve damage, leading to problems of sexual function, is almost absent. This is a risk of anterior procedures performed through the abdomen.
Possible complications are:
hemorrhage. It is always possible that some bleeding occurs from a ruptured blood vessel or from the sacral bone after it has been drilled, especially if the rod is sunk into the sacrum. It usually requires no specific measures.
bowel perforation. This of course is a serious complication that has happened a few times so far. Most of these instances however appear to be attributed to poor handling of the instrumentation or imperfect patient selection. It is however a real danger that patients should be made aware of.
infection. This is a risk that is present in any operation. The risk is low due to the long distance between incision and actual operating area and the amount of tissue to cover and protect the trajectory.
hardware problems. Working with any implant can lead to failure, malposition, loosening, breakage etc. It is also possible that the desired fusion does not occur. This can also happen with the other techniques. Also some subsidence of the fifth vertebra over the rod can occur, but this does not have to lead to any complaints.
Complications generally speaking can be dealt with well. If necessary the rod can be removed and it is always possible to supplement the Axialif with posterior screws.
Last revision of this text: August 2007