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Lumbar Spine Chapter

Normal Anatomy

The bones of the spine (vertebrae) are stacked on top of each other with soft cushioning discs located in between them (intervertebral discs). These discs are very similar to a jelly doughnut. The outer portion of the disc (called the annulus fibrosus) is like the dough of a jelly doughnut and the inner portion (nucleus pulposus) is similar to the jelly inside the doughnut. In a normal disc, all the nucleus pulposus remains inside the annulus fibrosus.

Lumbar Spine

However, if there is a full thickness tear in the annulus fibrosus, the nucleus pulposus will leak out of that tear. This is similar to a full thickness tear in the dough of the jelly doughnut with the jelly inside it leaking out through that tear. The leaked part of the nucleus/jelly is referred to as a 2 “disc herniation.” It is also commonly referred to as a herniated disc, disc extrusion, or a slipped disc. The leaked portion of the disc enters the space where the nerve resides and causes compression of the nerve. This compression leads to irritation of the nerve and the subsequent pain, numbness, tingling, paresthesias (feeling of “pins and needles”), temperature changes, etc.

herniated disc

What does a normal intervertebral disc look like?

The normal disc has two parts to it:

  1. annulus fibrosus- the outer shell (connects the bones & contains the nucleus pulposus)
  2. nucleus pulpous- the inner gelatinous material (cushions the bones & absorbs shock)

This disc looks very similar to a jelly donut with the nucleus pulposus resembling the “jelly” in a jelly donut and the annulus fibrosus resembling the “dough” of the donut.

spinal chord Lumbar Spine

What is the main job of the intervertebral disc?

  1. Absorb the shock subjected to the spinal column
  2. Allow motion between the bones of the spine so that we can bend and move our neck and low back


Most episodes of low back pain are caused by relatively harmless conditions. The most common of these conditions include: muscle strain (“pulled muscle”), weak core muscles (abdominal and lumbar extensor muscles), degenerative discs, arthritic facets, spinal instability (spondylolisthesis- slipping of the bones), scoliosis and a myriad of other more rare conditions. Low back pain affects up to 90% of the population at some point in their lifetime.

The most common reason for back pain is due to the normal aging process of the discs in the low back. This wear is a combination of biological changes that occur in the disc (determined by one’s genetic program) as well the mechanical effects of absorbing both weight and allowing motion to occur between the bones and the disc. This mechanical wear is very similar to the wearing of a car tire or the sole of a shoe with increasing use. Low back pain results when these discs reach a critical level where they can no longer absorb shock efficiently (Figure 1).

degenerative disc mri
xray degenerative disc

Figure 1: MRI demonstrating normal degenerative discs at every level except at L5-S1 where the disc has degenerated (“worn out”). Note how the other discs are tall and have the white core (hydrated “jelly” inside a donut) whereas the L5-S1 disc is dark and has no white core in it. Thus, the L5-S1 disc has lost its ability to absorb shock and may lead to pain during a “flare up.” This patient had back pain of the “discogenic” pattern. Xray demonstrating degenerative discs.

This common form of back pain is called discogenic pain (implying pain from the discs). The pain is usually worse with prolonged sitting or standing. The person may note that they are often stiff and sore in the morning after waking. Bending and lifting are often uncomfortable. Frequent position changes and walking short distances may reduce the pain. The natural history of discogenic pain is that of intermittent episodes of back pain that occur over many years. This is not a dangerous condition and treatment is based on the severity of the pain. Improving your aerobic conditioning can help in the long term management of this condition. Even if aerobic activities cause back pain, they should be pursued. No long term harm will result in exercising through the back pain.

For most patients, using anti-inflammatory medications will alleviate the pain during the episodic flare-ups. Physical therapy for strengthening, stretching, body mechanics, etc can be helpful in those patients with more severe and persistent pain. Epidural steroid injections are reserved for those patients who have persistent pain and have failed physical therapy. While most patients do not need surgery for this condition, some patients who have failed all other treatment modalities and continue to suffer from severe pain, may benefit from surgery.

A person with discogenic low back pain should expect intermittent episodes of short lasting back pain over many years. Each episode of back pain generally lasts less than three weeks and certainly no more than six weeks. If at any point the pain lasts longer than expected, the condition should be re-evaluated by a physician. If the pattern of pain changes then it should be re-evaluated by a physician.

standing xray spondylolisthesis

Figure 2A: Standing X-ray demonstrating a “spondylolisthesis.” Note how the L2, L3 and L4 bones are lined up, as demonstrated by the smooth blue line drawn at the back of the bones. However, a line drawn behind the bones of L4 and L5 is NOT smooth and demonstrates a “step” between those two bones…there is a forward slipping of the L4 bone on the L5 bone! This slipping of the bones is called a spondylolisthesis and can cause back pain with or without leg pain/numbness/tingling/burning etc. These symptoms can be present all the time but are generally worse with sitting, standing or walking and improve when the patient lies down. This is because as the patient sits or stands, there is more stress on the bones and the slip gets worse- thus more pain! When the patient lies down, there is less stress on the bones at the slip; thus, there is a decrease in the pain.

Lumbar Spine

Figure 2B. The MRI above is of the same patient. However, note that the slip at L4-5 is not as dramatic as on the X-ray. Why? Because the MRI is done with the patient lying down! Hence, less stress on the L4 and L5 bones and less slipping! Most of these slips eventually lead to stenosis (tightening around the nerves) because the slipping narrows the spinal canal and the abnormal forces at the slip cause bone spurs, disc herniations and thickening of the ligamentum…all of which contribute to the stenosis. Treatment is determined based on the patient’s symptoms as described earlier in this article.

ct scan degenerative facet joint

Figure 3. CT scan demonstrating a degenerative facet joint. Normal facet joints have a smooth surface made of cartilage that slides against each other. One of the facet joints is more worn out (right side of this page) than the other facet joint. This can lead to back pain as two uneven, rough surfaces move against each other.

scoliotic curve

Figure: Scoliosis is a curvature of the spine that is more than 10 degrees in the frontal plane (looking at the patient face to face). The above radiograph demonstrates a scoliotic curve.

Lumbar Spine

Figure: These radiographs demonstrate the progression of scoliosis over a period of 22 years. Notice how rapidly the curve has progressed from age 50 to 55 (15 degrees). [Aebi M. Eur Spine J 1995]

What is a disc herniation (herniated discs)?

A disc herniation occurs when a full thickness tear in the outer part of the disc (tear in the dough of the jelly donut) allows the inner portion of the disc (the jelly inside the donut) to leak out of the tear. Because the nerve root lies right next to the intervertebral disc, it gets compressed by the leaked nucleus pulposus (leaked jelly from the donut). This compression of the nerve root can lead to pain, numbness, tingling, burning or the sensation of “pins and needles” that run down the arm or leg. It can also cause weakness in the arm or leg muscles and rarely may lead to loss of bowel or bladder control.

herniated disc
MRI Lumbar Spine

MRI of the lumbar spine demonstrating a disc herniation on the right side. This particular patient had severe pain, numbness, tingling and weakness in the right leg.

Lumbar Spine

MRI of the neck demonstrating a LARGE disc herniation causing severe spinal cord compression. In a case like this, non-operative treatment is NOT amenable to relieving the pressure on the spinal cord and surgery is recommended as a first line of treatment.

Disc Herniation - Lumbar Spine

Figure. MRI of the lumbar spine demonstrating a disc herniation at L4-5 on the patient’s right side (arrows are pointing at the herniated disc in A, B, D and E). The picture marked C shows a normal part of the spine where there is no herniation. 17


Disc herniations can be treated nonoperatively or may require surgery. Most disc herniations can generally be treated non-operatively if the symptoms associated with it (ie pain, numbness, tingling, burning sensation, etc) are mild and tolerable. The only time that surgery is recommended as a first line of treatment is if there is:

  1. intractable pain
  2. muscle weakness
  3. spinal cord compression
  4. loss of bowel &/or bladder function

Non-operative treatment options include:

  1. Anti-inflammatory medications (Ibuprofen, naprosyn, steroids, etc.)
  2. Physical therapy
  3. Epidural injections

*In many cases, chiropractic care and acupuncture can be very effective for short term pain relief. I support these modalities for selected conditions.

Depending on the size of disc herniation and amount of nerve root compression, the pain may last from a few weeks to several months. It is often difficult to judge the duration and severity of symptoms.


These injections use cortisone or another similar medication to reduce inflammation that is the cause of your pain. The injections can be done in different parts of your spine depending on where the problem exists (nerve compression, facet arthritis, degenerative disc, etc.). These injections are very safe and are generally performed in a matter of minutes with very little discomfort. Most patients experience significant relief with only one injection; however, in patients with severe arthritis, multiple steroid injections may be necessary to control the pain. Most physicians generally will not perform more than 3 injections in the same part of the spine within a 6 month period.

In our practice, we perform these injections with the use of an X-ray machine to ensure accurate placement of the medication. Patients are awake during the injection and the physician explains each step to the patient before performing it. The procedure generally starts with the injection of “numbing” medicine in the skin. Once the skin is numb, another needle with the cortisone is directed to the abnormal part of the spine with the use of the X-ray machine. Once the location is ascertained, the medication is then delivered. The needle is then removed and a Band-Aid is placed on the injection site. You are then allowed to go home or work. There are no activity restrictions and you are free to partake in any activity you choose.


A small (around 1 inch) incision is made over the affected disc space of the lumbar spine. I use a microscope to provide the best visualization and minimize the size of the incision and amount of soft tissue injury. The space between the two vertebrae (interlaminar space) is identified and entered. Then, the nerve root and the disc herniation is visualized. Specialized tools are used to safely remove the herniated disc and decompress the nerve root. Sometimes there are bone spurs that are also compressing the nerve root (in addition to the disc herniation). When this condition exists, the bone that is compressing the nerve root is removed along with the herniated disc. In most cases the amount of bone that is removed is not enough to weaken the spine. The entire disc is not removed. Only the disc that is directly compressing the nerve root (the “leaked” portion) is removed. After removing the herniated disc, the small hole in the back of the annulus fibrosus is identified; if there are any additional disc fragments that are threatening to come out the disc space, they are also removed.

Most patients go home a few hours after surgery on the same day while a few patients stay overnight. Patients are allowed to get out of bed and walk independently within a couple of hours of the operation. The overwhelming majority of patients experience significant, if not complete relief of the leg pain, numbness, tingling, etc. There is some pain at the incision site but it is generally well controlled with pain medication; most patients are off all pain medications in a few days. Immediately following the operation, patients are allowed to resume all activities without restrictions.

The results of this operation are generally very good. The critical factor for good outcomes with this type of surgey is the accuracy of diagnosis. The better the correlation between your symptoms, examination findings and imaging studies, the better the chance of surgery eliminating your symptoms. When there is very good correlation between your symptoms, exam findings and MRI studies that chance of surgical success can be 97% or better.

What is “spinal stenosis?”

Spinal stenosis is a very common condition that leads to pinching of the nerves in the lower lumbar spine. It is the result of the progressive wear and tear of the spine that leads to a decrease in the diameter of the spinal canal and subsequent pressure on the nerves in that canal. It is caused by bulging discs, herniated discs, bone spurs, thickening of the ligaments and other changes in the structure of the bones.

MRI severe

The MRI above demonstrates severe spinal stenosis in between the L4 and L5 bones. Note that there is no white fluid (space) around the nerves at that level. In fact, there is no space around the nerves and they are completely “pinched!”

Is lumbar “spinal stenosis” dangerous?

Progressive lumbar spinal stenosis that occurs in most patients is not dangerous in the sense that it will not cause paralysis. It can, however, be quite painful. As it increases in severity, a patient’s ability to stand or walk any significant distance diminishes as they began experiencing back pain &/or leg “heaviness” (pain, numbness, tingling, burning, etc). Patients with spinal stenosis generally feel better by leaning forward when they walk or stand with most patients reporting that they have to lean on a grocery cart to be able to navigate around a grocery store. Very rarely does lumbar spinal stenosis pose a risk for permanent nerve injury (loss of leg, bowel or bladder function) and is generally not a concern.

How is lumbar spinal stenosis treated?

Because the condition in not life threatening or pose a risk for paralysis, it is treated symptomatically. Treatment options include:

  1. Medications as needed (Ibuprofen, Naprosyn, Tylenol, etc.) for pain
  2. Physical Therapy- good for general conditioning and stretching
  3. Epidural Injections- “cortisone” injections in the spine
  4. Laminectomy- relieves pressure on the nerves by removing bone and ligaments
  5. X-STOP Spacer- creates space for the nerves without removing bone
  6. XLIF- creates space for the nerves without removing bone and helps “straighten” and stabilize the spine if there is any deformity, instability or scoliosis



A one inch (or longer for extensive stenosis) incision is made in the middle of the back over the effected region of the spine. The muscles over the bone are moved aside until the laminae are visualized. The correct level is then identified again. With the use of a microscope and specialized tools, the laminae are removed and the nerves are decompressed (released so that they are no longer pinched). All the unnecessary bone spurs and thickened ligaments that compress the nerves are also removed. This portion of the case is called a laminectomy and is all that is required in the majority of cases of spinal stenosis. This is a very safe operation which is usually performed in a short period of time (30 minutes to 120 minutes depending of the extent of stenosis) without any significant complications (I will discuss individual complications with you). The overwhelming majority of patients with spinal stenosis experience immediate relief of their symptoms after surgery and are very satisfied.

Laminectomy with Fusion

Patients with back pain due to spondylolisthesis (abnormally slippage between bones), scoliosis (curvature of the spine) or spondylosis (severe arthritis of the spine) may require a fusion with or without the placement of screws and rods. While this is also a very safe procedure, it does add more operative time and is generally associated with a slightly longer recovery and postoperative pain compared to laminectomy alone. After this procedure, most people go home in 3-4 days.

Lumbar Spine

Figure: Lateral radiograph (Xray) demonstrating a spondylolisthesis (slipping of the bones) at L4-5

xray laminectomy

Figure: X-rays of the same patient after he underwent a L4-5 laminectomy & fusion to stabilize the slip at L4-5. The screws and rods prevent the abnormal motion (translation) between the L4 and L5 bones thus relieving the pain.


This is a “minimally invasive” procedure that relieves the pressure off the nerves with the insertion of a metallic device in between the spinous processes of the vertebrae. The insertion of this device distracts the two bones which increases the space between the two vertebrae, thus creating more room for the nerves that are in between the two bones. There is no bone removal in this procedure and thus there is less postoperative pain than a laminectomy. There is also no “fusion” with this procedure. Most patients go home the same day (outpatient surgery) with this procedure; however, I give patients the option of staying in the hospital (usually overnight) depending on their preference. For certain patients, this procedure can be performed without general anesthesia (with the patient in a “twilight” but without a “breathing tube”).

spinal stenosis
postoperative position

Figure: The MRI on the top demonstrates spinal stenosis at L4-5. This patient failed nonoperative treatment and underwent the X-STOP procedure. The radiograph on the bottom demonstrates the postoperative position of the X-STOP implant. The patient had complete relief of his lower extremity symptoms after the 15 minute X-STOP procedure and went home the following day.


This is also a “minimally invasive” procedure for lumbar spinal stenosis. This technique is utilized when the stenosis is caused by or associated with scoliosis, instability (spondylolisthesis) or severe disc degeneration. A 1-inch incision is placed on the side, the intervertebral disc is removed and a plastic spacer is inserted between the vertebral bodies to distract the adjacent vertebrae and relieve the pressure on the nerves. This procedure can take 30 to 120 minutes depending on the extent of spinal stenosis. Most patients stay overnight and go home the following day. For patients with severe scoliosis, this is also an excellent method to achieve deformity correction without the extensive pain, operative time and blood loss associated with traditional scoliosis surgery. For patients with severe scoliosis and others with osteoporotic bone, screws may also need to be placed to achieve absolute stabilization. Even so, these screws are placed in a minimally invasive fashion through 1-cm incisions on the back. Whether or not a patient needs screws is dependent on an individual’s bone quality, pathology and other medical conditions. It is generally discussed preoperatively.

posterior fusion radiograph

The patient in the above radiograph is a 62 year old female who underwent a posterior fusion 12 years ago. She developed stenosis with a degenerative disc at the level above the fusion. Note the flattened disc space on the radiograph on the left; note how the XLIF spacer restored the disc height on the radiograph on the right. She underwent the XLIF procedure for this problem. The surgery took 30 minutes and she went home the next day with a minimal amount of “soreness” at the incision site. She had immediate of her leg pain, numbness and tingling.

scoliosis radiograph

This 72 year old woman underwent a minimally invasive fusion (utilizing the XLIF procedure) for lumbar spinal stenosis and scoliosis. She had one small incision on the side for the XLIF procedure and several very small incisions on the back for each screw. She was in the hospital for 4 days before going home (XLIF on Monday and the screws on Wednesday before being discharged on Friday). She lost a minimal amount of blood and did NOT need a blood transfusion. She was walking independently the day after each procedure. The radiograph on the left shows her scoliosis before the surgery and the radiograph on the right demonstrates her curve after surgery.

What happens after the surgery?

Patients are allowed to get out of bed and walk independently within a couple of hours of the operation. The overwhelming majority of patients experience significant, if not complete relief of the leg pain, numbness, tingling, etc. There is some pain at the incision site but it is generally well controlled with pain medication. Patients with a X-STOP or an XLIF usually go home the next day. Patients undergoing a laminectomy alone go home in 1-3 days while those with a laminectomy and open posterior fusion go home in 2-4 days. All patients are able to walk on their own and are independent in their activities of daily living (eating, drinking, personal hygiene, etc) when they go home.

Most patients are off all pain medications within a few days to a few weeks depending on their specific procedure. Within a few days after surgery, patients are allowed to resume all activities without restrictions (with common sense being the guiding principle); however, we also give each patient specific written instructions on the level of activity. There are individual exceptions to this and are discussed on an individual basis.

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