Spondylolisthesis is a medical term that describes an abnormal anatomic alignment between two bones in the spine. This anatomic abnormality has been around since antiquity, but it was first described in the modern medical literature by a Belgian obstetrician named Dr. Herbinaux in 1782 who noticed that the abnormal alignment of the lumbar spine and pelvis in very severe cases made natural childbirth difficult. The term spondylolisthesis comes from two greek words: “spondy” (σπονδυλος) which means “vertebra” and “listhesis” (ὁλισθος) which means “a slip”.
Spondylolisthesis most commonly affects the lower lumbar spine, typically at the L4/5 or L5/S1 levels. Spondylolisthesis is a very common condition, occurring in about 5% of the population. The most common type of spondylolisthesis is a degenerative slip that occurs at the L4/5 level. This type of slip is caused by degeneration of the intervertebral disk and the facet joints which results in an increase in the “sloppiness” of the joint, much like a worn bushing. Here are two images that depict the changes that occur as the disk degenerates. The gel-like substance inside the disk shrinks, the edges of the disk become irregular, and bone spurs develop.
A recent clinical consensus paper was produced by the North American Spine Society that will be referenced throughout this guide, and their version of the “best working definition” of a degenerative lumbar spondylolisthesis is as follows: an acquired anterior displacement of one vertebra over the subjacent vertebrae, associated with degenerative changes, without an associated disruption or defect in the vertebral ring. The key elements in this definition — anterior slip, degenerative change, and no disruption of the vertebral ring are easy to demonstrate in a typical case of spondylolisthesis. As the disk deteriorates it becomes less capable of absorbing all of the forces of normal human movement. Because the joint has increased “play” or “sloppiness” L4 starts to slip forward with respect to L5. Here are X-rays and an MRI scan of a typical case of a grade 1 spondylolisthesis. Flexion and extension X-rays are often used to evaluate how much abnormal motion occurs at the level of the spondylolisthesis.
The second most common type of spondylolisthesis that we see occurs at L5/S1. This condition is especially common in people who have repetitively extended their spine during athletics in adolescence. The theory is that repetitive hyperextension of the spine during athletics results in a stress fracture called a spondylolysis in a part of the vertebral body called the pars inter-articularis which disrupts the continuity of the vertebral ring. The lack of a connection between the posterior and anterior parts of the L5 vertebral body allows the L5 vertebral body to slip forwards with respect to S1. The association between adolescent athletics and this condition is demonstrated by the fact that about 95% of competitive gymnasts and about 35% of competitive football players have X-ray evidence of the stress fracture that may result in a spondylolisthesis later on in life.
This condition usually develops in two stages. First the patient has an episode of low back pain during their adolescence which is when the stress fracture of the pars interarticularis occurs. Then as the disk starts to degenerate later in life, they begin to complain of low back and leg pain. In contrast to a degenerative spondylolisthesis, this type of slip does involve a disruption of the vertebral ring, so this is often called an “isthmic” spondylolisthesis
Symptoms of spondylolisthesis
Patients with spondylolisthesis complain of low back pain and pain along the course of the nerves that are pinched by the spondylolisthesis. The narrowing of the normal space available for the nerve roots in the spinal canal is called stenosis. The back pain typically occurs in the area of the lower lumbar spine and often radiates around the abdomen and into the buttocks. The location of the nerve root pain depends upon where the slip is occurring and where the nerve roots are compressed. Nerve root compression due to stenosis is called a radiculopathy: radix is the greek word for “root” and pathos a word for “a disease of”. Pain and numbness in the legs as the result of a spondylolisthesis occurs in patterns called a radiculopathy that are very characteristic. The human body is divided into a series of dermatomes which can be visualized as a map of where the nerves travel after the leave the spinal canal. When the root of the nerve is affected, the entire course of the nerve is typically painful, numb, or the skin in this area is unusually sensitive. For example, here is a map of the normal dermatomes of the body, and then three diagrams of an L4, L5, and S1 radiculopathy. Patients with a spondylolisthesis at L4/5 usually have L4 nerve root pain due to compression of the L4 nerve root in the neural foramen. Patients with a slip at L5/S1 usually have L5 nerve root pain due to tension on the L5 nerve root. For example, a patient with an L4/5 spondylolisthesis will usually describe low back pain at the base of the spine, radiating into the buttocks, associated with pain and numbness along the sides of the legs, down the front and sides of the calves, with numbness and tingling in the feet.
The pain that is associated with spondylolisthesis is variable. It is often worse with standing and many patients find that the length of time they can walk comfortably starts to shorten as the disease progresses. We call this finding “limited walking endurance” and it is often an indicator of how severely the patient is affected and how much nerve root compression they have. Patients who are able to walk for more than an hour rarely need operative treatment, whereas those who can only walk for a few hundred yards before they are limited by back and leg pain will often experience substantial relief once their spondylolisthesis is corrected. While the pain associated with a spondylolisthesis is usually worse when the patient is on their feet, many patients have a hard time sleeping at night because the nerve root pain keeps them awake.
Xray and MRI findings in spondylolisthesis.
The best test for diagnosing a spondylolisthesis is a lateral Xray of the lumbar spine with the patient standing. It is important that the patient is standing because there are some slips that return to their normal position when the patient lies down, so they are not apparent on supine X-rays or an MRI scan. The best test for evaluating the degree of nerve root compression and spinal stenosis caused by spondylolisthesis is an MRI scan of the lumbar spine.
Here are a series of X-rays and MRI scans showing the relevant anatomic finding in a typical L4/5 degenerative spondylolisthesis. Click on these images to enlarge them to full size
And here are the X-rays and MRI scans of a patient with an L5/S1 spondylolisthesis with bilateral pars defects.
Non-operative treatment of spondylolisthesis
Physical Therapy: While it impossible to reverse the degenerative changes that occur with aging, it is possible to strengthen the muscles that surround the spine. This helps to stabilize the lumbar spine and will often result in a decrease in symptoms of low back and leg pain to the point where surgery becomes unnecessary. This type of therapy MUST emphasize active rehabilitation, which means that the patient must work actively to strengthen the muscles of the abdomen, low back, and core. Massage, hot pack treatments, and electrical stimulation may feel good at the time, but their effects are always temporary and they WILL NOT result in sustained relief. The type of therapy that we employ emphasizes core conditioning and strengthening and our therapists will instruct you on how to do these exercises properly. If your symptoms are relatively mild and you are still able to exercise, hike, and play some sports, then often a Pilates or a Yoga program may be very beneficial, less costly, and more convenient than going to a physical therapist.
Medical Management: Non-steroidal pain relievers like Aspirin, Tylenol, Motrin, and Ibuprofen are very helpful in the management of spondylolisthesis. The medications can calm down the inflammation that accompanies degenerative disk disease. This often makes it possible to participate in physical therapy with less pain which makes it possible to work harder to strengthen the muscles of the low back and abdomen.
Selective Nerve Root Blocks: In our clinic we have specialists who perform selective nerve root blocks with injectable medications like Cortisone and Kenalog that are much stronger than the anti-inflammatories you can take by mouth. These injections are performed in the surgical center and are done using an intra-operative X-ray machine to make sure that the medication is injected in the same area where the nerve root compression is occuring. In our experience, nerve root blocks are very helpful for patients. They will often result in a sufficient reduction in pain so that physical therapy is tolerable. The block may also interrupt the “cycle of inflammation” to the point where the symptoms are manageable and surgery can be avoided indefinitely.
Narcotic Pain Medications: In our experience, using narcotic pain medications on a daily basis for the treatment of the pain associated with a spondylolisthesis is a bad idea. Because spondylolisthesis is a condition that tends to worsen with time most people who start taking narcotics find it very difficult to stop. The use of narcotic pain medications for an open-ended diagnosis in which there is not a defined point in the future when we know that the pain will spontaneously resolve is a dangerous situation. For example, if a patient has a fracture, we know that the pain will subside once the fracture heals. However, with a spondylolisthesis, because there is not a possibility of spontaneous correction, the patient will continue to perceive a need for narcotics on a regular basis. This quickly leads to tolerance as the medications become less effective with time and their routine use becomes habit forming. For more information on my philosophy about the use of narcotic pain medications, click here.
The North American Spine Society’s consensus statement on non-operative care for spondylolisthesis is a follows: The majority of patients with symptomatic degenerative lumbar spondylolisthesis and an absence of neurologic deficits will do well with conservative care. Patients who present with sensory changes, muscle weakness, [or a short walking endurance] are more likely to develop progressive functional decline without surgery. Progression of slip correlates with jobs that require repetitive anterior flexion of the spine. Slip progression is less likely to occur when the disc has lost over 80% of its native height and intervertebral osteophytes have formed. Progression of clinical symptoms does not correlate with progression of the slip.
Surgery for spondylolisthesis
Here is what the North American Spine Society has to say: Surgery is recommended for treatment of patients with symptomatic spinal stenosis associated with low grade degenerative spondylolisthesis whose symptoms have been recalcitrant to a trial of medical and interventional treatment. In our clinic we agree with this statement. What this means to us is that patients who have symptoms that can be clearly attributed to their spondylolisthesis should first be educated about their condition. Next they should consider physical therapy and lifestyle changes that we believe are associated with improvements in back pain. If they continue to have pain they should consider a selective nerve root block to temporarily reduce the inflammation in the nerve roots — as long as this is seen as a bridge to making physical therapy more tolerable. Surgery should only be considered when the patient has continued symptoms that do not improve with physical therapy or medical management.
Our technique for the surgical correction of spondylolisthesis is designed to achieve four goals
1. relieve the nerve root compression that is causing pain and numbness in the legs
2. stabilize the unstable spinal segment that is slipping
3. improve the alignment of the spinal canal
4. provide the patient with a durable solution that will improve their quality of life for years to come.
While there is a great deal of debate about the best surgical technique for the treatment of spondylolisthesis, the NASS clinical guidelines do state that surgical decompression with fusion is recommended for the treatment of patients with symptomatic spinal stenosis and degenerative lumbar spondylolisthesis…and that …decompression and fusion is recommended as a means to provide satisfactory long-term (greater than 4+ years) results for the patient. For example, on a recent Spine Surgery Board Certification Examination administered by the American Academy of Neurological Surgeons, the following question was asked: A 47 year old dentist presents with a 5 year history of intractable low back pain refractory to several courses of physical therapy and numerous medications. He has recently developed bilateral L5 radiculopathy. MR imaging demonstrates grade II anterolisthesis of L4 on L5 with resulting L4-5 central canal stenosis and bilateral neuroforaminal stenosis. The BEST treatment option is:
- dorsal column stimulator
- anterior lumbar interbody cage fusion
- laminectomy and pedicle screw fusion
- epidural steroid injection
- laminectomy with facetectomy
The correct answer, according to the AANS, is #3. Here is their explanation: This patient has failed reasonable attempts at non-operative management and has an anatomical abnormality that corresponds to his clinical symptomatology. Surgical correction is the best option. Decompression alone in the presence of spondylolisthesis in a relatively young patient is associated with a high incidence of progressive listhesis and worsening pain. Stand alone anterior lumbar interbody fusion procedures are contraindicated in the presence of more than a minimal spondylolisthesis. Placement of translaminar facet screws requires the presence of lamina. Posterior decompression and fusion, especially with interbody techniques, is associated with better patient outcomes than any of the other treatment options listed.
Here is a series of pictures from our operating room during correction of a spondylolisthesis of the spine…
Here are a series of x-rays that demonstrate the correction of spondylolisthesis with a decompression and fusion of the slip performed in our clinic in Monterey, California. You can click on each of these Xrays to enlarge them to full size.
L4.5 degenerative spondylolisthesis repaired with an L4.5 lumbar decompression, instrumented fusion, and reduction of spondylolisthesis.
L5/S1 isthmic spondylolisthesis repaired with an L5/S1 lumbar decompression, instrumented fusion, and reduction of spondylolisthesis.