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Introduction
Procedure
Risks
Alternative Treatments
The lumbar spine is comprised of vertebral bodies (also known as vertebrae) that are separated by soft intervertebral discs, which act to cushion the spine, allow mobility, and provide stability.
A variety of reasons can lead to instability of the lumbar spine, which causes increased movement and malalignment between adjacent vertebrae, as illustrated in the figure below, where the image on the left depicts normal lumbar spine alignment and arrow in the figure on the right shows malalignment (also known as spondylolisthesis).
This malalignment can cause symptoms such as back pain which is worse with movement or weight-bearing and/or numbness/weakness in the legs that results from compression of one or more nerve roots.
In select patients surgery (lumbar fusion) may be the best option for relief of symptoms and prevention of loss of function by immobilization (stabilization) of the unstable (misaligned) vertebral levels through placement of metal screws and rods. A graft material is generally placed either between the vertebral levels (interbody lumbar fusion) or over the back part of the vertebrae (posterolateral lumbar fusion) in order to provide a conduit for bony fusion and to prevent collapse of the vertebrae. The graft may be made from synthetic materials, patient’s own bone, cadaveric donors, or a combination of these sources.
Various types of interbody fusion exist, including posterior lumbar interbody fusion (PLIF), anterior lumbar interbody fusion (ALIF), and transforaminal lumbar interbody fusion (TLIF). PLIF and TLIF are very similar procedures where the graft material is placed between the vertebral bodies through the incision that is made in the back. In the ALIF procedure, the graft is placed between the vertebral bodies through a small incision that is made in the middle of the lower abdomen.
The main difference between the posterolateral and interbody fusion procedures is the location where the bone graft will be placed. Exactly which procedure is performed depends on several factors including anatomy, the severity of the malalignment, and presence or absence of narrowing within the spinal canal (lumbar stenosis), among others.
Over time, the vertebrae and graft will fuse together, leading to immobility and stabilization of the spine. The risk of non-fusion exists in every case despite good surgical technique, and this risk is increased with a history of tobacco use, certain medications (such as steroid or chemotherapy), malnutrition, and chronic illness.
After induction of general anesthesia, an incision is made in the lower back.
The muscle and other tissues are dissected until the bone is reached. Retractors are placed to keep the muscle and other tissue out of the way and to reveal the bony spine.
After exposure of the bone, holes are drilled through the pedicles into the body of the vertebra, as shown in the side-view image of the lumbar spine below.
Pedicles are bony connections between the back and front part of the vertebrae, as shows in the top-view image of a lumbar vertebra below.
Metal (titanium) screws are then placed into the holes created in the pedicles. This process is repeated for the other vertebral level(s) that are being fused.
At this point, one of two main types of fusion can be performed: posterolateral fusion or interbody fusion. Both of these methods are described below.
Posterolateral Fusion
For posterolateral fusion, after the above steps, metal (titanium) rods are then fastened to the screws to bridge them and create a stable connection between the vertebrae.
Bone graft is then placed around the screws/rods on either side over the exposed bone, as shown by the arrows in the back-view image of the spine below.
The retractors are removed and the incision is closed prior to termination of the operation.
Interbody Fusion
For the interbody fusion procedure, after exposure of the bone as described above, the back portion of the spine (lamina) is removed in order to gain access to the intervertebral disc.
A large portion of the disc is then removed in order to create a space for the graft. For the PLIF and TLIF procedures this is done through the incision that is already made in the back, as illustrated below.
The graft material is then placed in the intervertebral space.
For the ALIF procedure, a separate incision in made in the abdomen to gain access to the front of the spine and remove the disc, as illustrated below.
The graft material is then placed in the intervertebral space.
For all of the interbody procdudres at this stage (PLIF, TLIF, or ALIF), metal (titanium) rods are then fastened to the screws (similar to the posterolateral fusion procedure) and the incision is closed prior to the termination of the operation.
Due to advances in medicine and technology, surgical procedures are generally considered to be safe, and a great majority of patients who undergo surgery will not experience any complications. However, there are certain risks involved in any procedure which are important to be aware of in order to make an informed treatment decision.
Risks Specific to this Procedure: The risks associated with this surgery include, but are not limited to, damage to spinal cord or nerve roots leading to increased pain or other neurologic problems, loss of bowel/bladder function, sexual dysfunction, weakness or paralysis, numbness, cerebrospinal fluid leakage requiring placement of lumbar drain, need for further surgery, and spinal instability at adjacent levels or non-fusion of the fused levels leading to need for future surgery or treatment. Specifically for the ALIF procedure, the risks also include damage to any of the organs in the abdomen such as the bowel, nerves, and/or blood vessels leading to a variety of potential problems.
Infection: Invasion of tissue by bacteria or other germs occurs to some degree whenever a cut, incision or puncture is made. In most instances, through the natural defense mechanisms of the body, healing of the affected area occurs without difficulty. In some instances antibiotic medicines are prescribed and at times additional surgical measures may be necessary to combat infection.
Hemorrhage: The cutting of blood vessels causes bleeding and this occurs in every surgical incision. This bleeding is usually controlled without difficulty. At times, blood transfusions are required to replace blood loss. If blood transfusions are given, there are additional risks of liver inflammation, hepatitis, and the possibility of receiving Acquired Immune Deficiency Syndrome (AIDS). There is no absolutely reliable way to predict these unwanted reactions, some of which may be quite serious and even lead to death.
Drug Reactions: Unexpected allergies, lack of proper response to medications or illness caused by the prescribed drugs are possibilities. It is important for you to inform your physician and your anesthesiologist or certified registered nurse anesthetist of any problem you or your family have had with reactions to drugs and which medications you have taken in the past six months, including over-the-counter drugs, especially aspirin.
Anesthesia Reactions: There may be unusual or unexpected responses to the gases, drugs or methods used to anesthetize you which can lead to difficulties with lung, heart or nerve function. Eating or drinking before anesthesia increases the risks of vomiting which may cause significant complications. Inform your anesthesiologist or certified registered nurse anesthetist of problems you and your family have had with anesthesia.
Blood Vessel Inflammation and Clotting: It is impossible to predict the occurrence of blood vessel inflammation and clotting problems. If blood clots form, they can move from where they formed to other areas of the body and cause injury.
Injury to Other Organs: Because of the closeness of other organs to the area being operated on, there may be injury to other organs. The stress of surgery or the procedure may also harm other organ systems of the body.
The alternative management modalities for this procedure are physical therapy, pain management using medications or injections, certain alternative medicine therapies (acupuncture), and expectant management with no treatment at all. If the decision is made to not have this procedure, there may be associated risks which need to be discussed with a physician.
