Surgery from the Front or Back: Is There a Difference?
By Dr. Thomas C. Schuler
Patients that have severe back pain that does not get better with conservative treatment often become surgical candidates. If the pain is coming from the disc, then one possible treatment is to remove the disc and fuse the two vertebrae together. This can potentially stop the motion between the vertebrae and put an end to the pain.
The disc itself is a ligament just like a knee or a shoulder. When tears form in this ligament, it can lead to micro-instability, allowing for hyper flexion or extension as a patient moves. This micro-stress to a patient's disc can cause a leakage of enzymes, which will then irritate the outer covering of the disc. For patients experiencing this problem, spinal fusion surgery is one option.
There are many different ways the spine can be fused. The traditional way is to lay bone across the transverse processes. These are little knobs that stick out from the side of the vertebrae. So a surgeon lays bone across this area allowing one bone to fuse to the other. However, this often does not work when the source of the pain is coming from a disc that is degenerative. For patients with degenerative discs, removing the disc and putting a bone graft in between two vertebral bodies is often the best treatment. This allows the two bones to fuse together stopping the motion much more effectively than the older fusion techniques of laying bone across the transverse processes.
There are two approaches to a spinal fusion: either from the front or the back. The more traditional way is from the back where the surgeon removes the lamina in order to gain access to the disc space and then take the disc out. To do this, surgeons must pull the nerves aside and pack the bone into the disc space. The bone we use could be soft bone, pieces of bone chips, or a large bone graft. That is why this procedure is called a Posterior Lumbar Interbody Fusion (PLIF): interbody because it is between the vertebral bodies, posterior because it comes from behind, and lumbar because we are in the lumbar spine.
Traditionally, if a surgeon does a posterior lumbar interbody fusion, for example, in the case of a slipped vertebra, then that procedure will need to be supplemented with spinal instrumentation. The instrumentation serves one purpose, and that is to hold the spine stiff. An example of posterior spinal instrumentation is a system using pedicle screws. The pedicle screws go into the bone and hold the spine rigid, allowing the bones to grow together. The actual fusion occurs with the bone graft; the instrumentation can be thought of as an internal brace or a cast.
The other fusion technique is done entirely from the front. The disc is removed and the bone graft is placed between the vertebrae [Click here to learn more about this procedure, Anterior Lumbar Interbody Fusion (ALIF)]. This procedure has been made possible by several advancements. One of which is the LT-CAGE® Lumbar Tapered Fusion Device that is used to treat certain types of disc disease. This device is a threaded cage with holes in the middle as well as on the end. The cage is placed between the vertebrae and is designed for bone to be placed inside it and allow the bone to grow between the two vertebrae.
The benefit of the posterior instrumentation is that it is very strong and rigid. The down side is that it requires significant elevation of spinal muscles. Because there are a lot of muscles on the back of the spine, during a posterior approach we often have to detach them in order to gain access to the disc space. This muscle detachment can sometimes cause problems. Another complication of a posterior approach is that surgeons have to disrupt the facet joints. These are the joints that allow for bending and extending of the spine.
Though it is still appropriate to do a spinal fusion with instrumentation from the back, we now feel that if we can avoid it, patients benefit from the lack of some of the potential complications. One of the major complications of the posterior approach is the need for autograft bone. Autograft bone is a bone graft taken traditionally from the pelvis or the iliac crest of the patient. In order to obtain the graft, an incision is made over the pelvis and part of the bone is removed with either chisels or different awls. The reason for taking the autograft is that it is very effective and is the gold standard for use in fusion surgery that we have had to date. The problem with the removal of this bone is that it can be very painful. In fact, around 25% of patients who have had this bone graft procedure have some sort of chronic pain associated with the graft site after surgery.
However, there is now a new product, which allows us to avoid the pain associated with harvesting that bone graft. INFUSE® Bone Graft, used in combination with the LT-CAGE® Device, is a recombinant protein product, commonly known as BMP. BMP is a substance, found naturally in our bodies, which is believed to stimulate the primitive cells in the blood stream and turns them into osteoblasts. Osteoblasts are little cells that make up bone. The exciting thing about INFUSE® Bone Graft is that surgeons can now avoid the problem associated with harvesting the bone from the pelvis by using this new substance implanted in the LT-CAGE® Device.
INFUSE® Bone Graft comes to the surgeon in a dry form. During the surgery the circulating nurse will re-hydrate the INFUSE® Bone Graft with sterile water. The re-hydrated INFUSE® Bone Graft is placed on a sponge, which is then packed inside the LT-CAGE® device. This will allow for the possibility of a fusion to occur right through the holes in the cage without having to harvest bone graft.
The beauty of this substance is that it will allow us to obtain a solid fusion without any of the complications of harvesting bone graft. In essence, surgeons can get the same or better results without the problems. For patients who are petrified of pain and bone grafts, this is wonderful news.
Click here to meet one of Dr. Schuler's patients.
It is important that you discuss the potential risks, complications, and benefits of the INFUSE® Bone Graft/LT-CAGE® Lumbar Tapered Fusion Device with your doctor prior to receiving treatment, and that you rely on your physician's judgment. Only your doctor can determine whether you are a suitable candidate for this treatment.