One of the most common conditions we encounter as spinal surgeons is degenerative spondylolisthesis. Spondylo means spine, and listhesis means slip. In other words, it is a slip of one vertebra on another. The most common level involved is L4-5, but any lumbar level may be involved. A spondylolisthesis implies that there is underlying instability, and often times there is associated narrowing of the passage for the nerves. This narrowing of the spinal canal is called spinal stenosis. The cause of this type of spondylolisthesis is wearing out of the intervertebral disc in the front and the facet joints in the back of the spine. Simply put, it is due to spinal arthritis.
Instability of the slipped vertebrae can cause pain. The pain may be in the low back, which is called axial back pain. Narrowing of the passageway for the nerves can lead to nerve pinching and can lead to radiating pain down the legs, also known as sciatica. Severe narrowing can lead to weakness, heaviness, or numbness in the legs when walking or standing. The medical term for these types of nerve symptoms is neurogenic claudication. So the patient with a degenerative spondylolisthesis may present with complaints of low back pain, sciatica, leg weakness or heaviness or numbness, or a combination of the above symptoms. Often times, the symptoms are brought on by walking and standing, and relieved by rest or bending over, such as walking on a shopping cart.
Treatment options for degenerative spondylolisthesis include observation, anti-inflammatory medications, mild analgesics, physical therapy and exercise programs, injections into the spine, and surgery. We usually start with non-operative treatments to try to control symptoms. Often times the instability and stenosis are too severe and non-operative treatments provide only temporary relief. In this situation, the only long-term solution is to take pressure off of the nerves and stabilize the spine through a surgical procedure.
In general, the appropriate procedure for the treatment of degenerative spondylolisthesis is a laminectomy and fusion at the affected level. A laminectomy is a removal of the back covering of the spine, or lamina. This portion of the procedure can be referred to as a decompression. The fusion involves placing screws and rods into the spine and laying bone graft along the side of the spine. The bone graft will eventually be incorporated into the spine and turn into one solid piece of bone. Often the disc will be removed and shims, also known as cages, will be placed between the vertebrae to reestablish disc height and enhance the fusion.
Bone graft can be obtained from multiple sources. The removed lamina is a good source of bone and is commonly utilized. Bone can be taken from the back side of the pelvis, called the iliac crest, through the same or separate incision. Bone marrow can be harvested and concentrated through a needle placed into the iliac crest. This technique harnesses the patients own stem cells to promote bone healing. Donor bone, or allograft, is often used to extend available graft material. Synthetic grafts are available, but lack clinical data. Genetically engineered bone protein is available and can be highly effective. This product is BMP-2 and goes by the trade name of Infuse. Use of Infuse from a posterior approach is off-label per the FDA, but may be the best solution depending on the circumstances.
There are multiple ways to perform laminectomy and fusion procedures. They can be done through standard open techniques or through less invasive or minimally invasive approaches. No matter the technique, the operation needs to be done safely, effectively, and efficiently. When choosing a procedure, or a surgeon, remember that the most important factor in determining success for a spinal operation is the indication for the operation, and not the technique. In other words, it is not how we do it, but why we do it. Standard open techniques for the treatment of degenerative spondylolisthesis have extremely high success rates. All procedures need to be compared to this standard, in terms of effectiveness, complications, and safety.
© 2017 Christopher J. Bergin, MD and The Spine Center, SC