Spinal (Lumbar) Fusion/Lumbar Spinal Stenosis - Pinched Nerves in the Back

Introduction

The low back is a common place to experience pain.  This area of the back is called the lumbar spine.  The main function of the lumbar spine is to support the weight of your upper body.  The joints of the lumbar spine primarily allow you to bend forward or flex and extend or straighten at the waist.

Your spinal column is made of a series of short bones called vertebrae.  An opening in the center of each vertebra forms the spinal canal.  Your spinal cord and spinal nerves run through the protected canal and send messages between your body and brain.

Spinal Stenosis is a condition in which the spinal canal is narrowed.  The narrowed canal causes pressure on the spinal cord and nerves.  Spinal Stenosis may or may not produce symptoms.  Many cases of Spinal Stenosis can be treated without surgery.  However, some individuals experience severe or progressive nerve involvement, loss of function, and pain.  Surgical treatment can relieve nerve pressure and help restore function and relieve pain.

Anatomy

There are different areas of the spine, defined by their curvature and function.  The lumbar spine is located in your lower back.  It forms the curve below your waist.  The lumbar spine connects your upper body-- your head, trunk, and arms, to your lower body--your pelvis and legs.  Ligaments and muscles connect to your spinal column.  They provide stability while allowing movement.

Five large vertebrae make up the lumbar area of your spine.  The back part of the vertebra arches to form the lamina.  The lamina creates a roof-like cover over the back opening in each vertebra.  The opening in the center of each vertebra forms the spinal canal.  Your spinal cord and spinal nerves travel through the protective spinal canal.

Your spinal cord tapers near the first lumbar vertebra and forms a bundle of nerves called the cauda equina.  Your spinal cord and spinal nerves at the lumbar spine level send signals for sensation and movement between your brain and leg muscles.  The cauda equina is involved with regulating bowel and bladder functions.

There are discs between the vertebrae in your lumbar spine.  The discs are made up of strong connective tissue.  Their tough outer layer is called the annulus fibrosus.  Their gel-like center is called the nucleus pulposus. 
 
The discs and two small spinal facet joints connect one vertebra to the next.  The discs and joints allow movement and provide stability.  The discs also act as a shock-absorbing cushion to protect the lumbar vertebrae.

Causes

Spinal Stenosis is a condition in which one or more areas of the spine are narrowed.  It can involve the spinal canal in the center of the vertebrae and/or the "tunnels" where nerves branch out.  These areas are called foramina.  Spinal Stenosis is more common in people over the age of 50.  It can also occur in younger people that are born with a narrowed spinal canal.

Spinal Stenosis is most frequently caused by the gradual degeneration of the spine during the aging process.  The intervertebral discs become less fluid-filled and dry out with age.  They can lose height and bulge into the spinal canal.  The spinal facet joints and ligaments can thicken and enlarge, pushing into the spinal canal.  Arthritis is the main cause of these structural changes.

Arthritis is a major cause of pain, swelling, and structural changes in the lumbar spine.  Arthritis can occur for many reasons, including aging, “wear and tear,” injury, autoimmune disease, and inflammatory disease.  There are over 100 different types of arthritis.  Osteoarthritis and Rheumatoid Arthritis are types of arthritis that typically develop in the spine.

Osteoarthritis is the most common type of arthritis.  It is a chronic and degenerative condition.  Osteoarthritis tends to appear as people grow older.  It causes cartilage to gradually wear away bone to overgrow and cause "spurs".  These abnormal bone growths, called osteophytes can grow into the spinal canal and vertebral joints.  The bone spurs can compress the spinal cord and nerves disrupting their function.  Spondylosis is a condition that can result when Osteoarthritis affects the intervertebral discs and the vertebral facet joints.  Spondylosis causes disc degeneration and the overgrowth of bone into the spinal canal or nerve root canals.  A condition called spondylolisthesis causes one vertebra to slip forward on another.

Spinal tumors are abnormal soft tissue growths.  Acquired Spinal Stenosis develops when spinal tumors grow into the spinal canal or cause swelling.  A spinal tumor may also cause the vertebrae to shift out of place because of bone loss.  Acquired Spinal Stenosis can also develop when a spinal ligament ossifies.  Ossification occurs when calcium deposits form on a ligament and turn it into bone.  The posterior longitudinal ligament attaches to the spine and can cause stenosis if it ossifies and presses on the nerves in the spinal canal. 

Symptoms

Diagnosis

Your doctor can diagnose Spinal Stenosis by performing a physical examination and viewing medical images.  Your doctor will ask you about your symptoms and medical history.  You will asked to perform simple movements to help your doctor assess your muscle strength, joint motion, and spine stability.  Your doctor will order imaging studies to learn more about the location and extent of your spinal canal narrowing and nerve root compression.

Your doctor will order X-rays to see the condition of the vertebrae in your spine and to identify narrowed discs or thickened facet joints.  Sometimes doctors inject dye into the spinal column to enhance the X-ray images in a procedure called a myelogram.  A myelogram can indicate if there is pressure on your spinal cord or nerves from herniated discs, bone spurs, or tumors.  A bone scan may be used to show fractures, tumors, infections, or arthritis.  A bone scan requires that you receive a small harmless injection of a radioactive substance several hours before your test.  The substance collects in your bones in areas where the bone is breaking down or repairing itself. 

Your doctor may also order Computed Tomography (CT) scans or Magnetic Resonance Imaging (MRI) scans to get a better view of your spinal structures.  CT scans provide a view in layers, like the slices that make up a loaf of bread.  The CT scan shows the shape and size of your spinal canal and the structures in and around it.  The MRI scan is very sensitive.  It provides the most detailed images of the discs, ligaments, spinal cord, nerve roots, or tumors.  X-rays, myelograms, bone scans, CT scans, and MRI scans are painless procedures.

Treatment

Surgery

Recovery

Prevention