Minimally Invasive Procedures for Lumbar Spine Disorders
Introduction
Low back pain is the second most common cause,
behind the common cold, for a visit to the primary
care physician’s office. It is the number
one cause of disability in the young population
(less than 45 years old) and the third leading
cause of disability in patients older than 45
years old. The yearly cost of low back pain to
the American economy is estimated at $16 billion
(1990). The lifetime prevalence of low back pain
is 60-90%.
Most low back pain is self-limiting. Eighty-five
to ninety percent of low back pain resolves in
6-12 months spontaneously and 75% of “sciatica”
resolves in this same time span. But, is it necessary
to suffer for a year? Can one year be taken off
of work? Also, recurrences of low back pain occur
in 60-70% of patients. Clearly, untreated low
back pain can also lead to chronic pain conditions
as well.
Physiatric Approach
The physiatric approach to low back pain is a
very simple one. The first principle is to attempt
to identify the main pain generator. Is the patient’s
pain going down their leg related to a nerve that
is being pinched, or is it related to tight muscles?
Is it the vertebral bones causing the pain, or
is it the joints in the back that are making it
difficult for the patient to enjoy their life.
These are the types of questions we try to answer.
This is made more difficult by the ambiguity of
symptoms that some people experience. To help
answer these questions, physiatrists perform a
very careful history and physical exam, in addition
to using imaging studies (such as MRI, X-rays),
and different spinal injection techniques.
Pain Generators
The main types of pain generators that are encountered,
and can be treated effectively with minimally
invasive techniques are the nerve root, annulus
fibrosis of the intervertebral disc, the zygapophyseal
joints and the sacroiliac joint.
Why perform spinal injections?
The most pertinent reason for most patients is
to relieve the pain. We can diminish the pain
response with an injection and, hopefully, facilitate
participation in a therapeutic exercise program.
We also attempt to hasten recovery and obtain
diagnostic information with each injection. Lastly,
we may be able to avoid spinal surgery if the
injections are successful.
These injections work through the inhibition
of prostaglandin synthesis (inhibition of the
chemicals that your body puts out to sites of
tissue injury that stimulate inflammation), inhibition
of phospholipase A2, nerve membrane stabilization,
and blocking C-fiber conduction. In addition,
we perform all of our injections using fluoroscopy
(an X-ray machine) to ensure the proper placement
of the medication.
The most common injection that is performed is
an epidural steroid injection. It is most commonly
used for either nerve root generated pain or discogenic
pain, i.e., pain from the outer portion of the
disc, called the annulus fibrosis.
Nerve Root Pain: Radiculopathy
Nerve root pain is also called radiculopathy
and is pain that starts in the low back, goes
down the leg, below the knee. It typically is
worse with bending forward and patients may experience
weakness and/or decreased reflexes. A herniated
disc usually causes this condition.
Medication taken by mouth usually helps decrease
the pain and epidural steroid injections can be
very helpful. These injections can be given through
any of a number of routes. The most selective
injection is given through the transforaminal
route. Two other routes of administration for
these injections are caudal and interlaminar injections.
Research is currently under way to determine which
route is most effective in relieving pain from
a radiculopathy. As the transforaminal route is
the most selective manor in which to deliver medication,
it can also help with diagnosis.
Nucleoplasty
For a persistent herniated disc causing a pinched
nerve that does not respond to epidural steroid
injections, a new procedure may help alleviate
pain. Nucleoplasty is a technique that uses radiofrequency
energy to shrink the herniated disc. Studies of
this new technique are very promising in relieving
leg pain from a herniated disc.
Discogenic Pain
Pain that arises from the disc itself is often
difficult to treat. Usually these patients complain
of pain that is worse with sitting, and is improved
with bending backwards. A part of what makes this
condition difficult to treat is that the diagnosis
is often difficult to make. Studies have shown
that up to one-third of people without any low
back pain whatsoever have abnormal discs when
viewed with an MRI. In a patient with low back
pain and multiple discs that look worn out on
MRI, it is difficult to pinpoint the pain-generating
culprit.
Discogram (Discography)
A discogram is a procedure that attempts to verify
exactly which disc is painful by instilling dye
into the disc. This allows the doctor to view
the disc under x-ray and determine its structure,
as well as determining if the disc is sensitive
to the increased pressure from the dye. Often,
a CT scan to get an even better look at the disc
follows this procedure. It is not a treatment,
but, like an MRI, is used to gather additional
information. It may be used with pressure monitoring
which may give the physician additional information.
Discogenic Pain: Treatment
Treatment consists of epidural steroid injections,
preferably given via the transforaminal route.
In theory, this allows the medication to be in
close proximity to the painful disc. Unfortunately,
this theory has never been proven and the best
route of epidural steroid medication for discogenic
low back pain is unclear.
If epidural injections do not help with the low
back pain, another treatment possibility is Intradiscal
Electrothermal Annuloplasty (IDEA, IDET). This
technique involves inserting a heated catheter
in the nucleus pulposus. The proposed methods
of pain relief are 1) destroying ingrown nerves
to the disc and, 2) collagen remodeling. A study
is underway to help determine the efficacy of
this procedure.
Spinal Joints
The facets, or zygapophyseal joints, have also
been proven to be a pain generator in the low
back. In health, these joints help to guide movement
in the lumbar spine. When these joints are dysfunctional,
patients typically complain of pain located in
the low back that does not radiate below the knee.
Patients complain of pain worse at the end of
the day, which improves with sitting. Low back
pain may worsen with combining bending backwards
and rotating.
Nerve Blocks and Neurotomy
MRI, X-ray and CT scan may show degenerative
changes in the joints, or may be completely normal.
Injections of steroid and numbing medicine directly
into the joints may help relieve the pain.
Another alternative is to perform an anesthetic
block to the nerves that supply sensation to the
joint. These are called medial branch blocks of
the dorsal ramus. An advantage of these injections
is that the nerve also supplies some of the back
muscles. This type of injection is very helpful
for patients with muscle spasm in the low back.
If either the facet joint injection or the medial
branch block gives excellent relief but is short-lived,
radiofrequency neurotomy is an option to induce
long-term relief. The procedure is similar to
the medial branch blocks, but instead of numbing
the nerves that supply the facet joints, heat
is used to destroy those nerves.
Sacroiliac Joint
The sacroiliac joint is often cited as a pain
generator in the low back. Patients typically
complain of low back pain in the upper buttock
and may be worse on one side than the other. Also,
their pain is increased with walking and does
not go below the knee. Patients who have undergone
a fusion in the lumbar spine are prone to this
disorder. Injections directly into the sacroiliac
joint can be helpful for this problem.
Conclusion
Again, the physiatric approach is to make an
accurate diagnosis targeting the main pain generator.
Injections are one tool in the bag of any good
physiatrist. A main component of treatment that
wasn’t addressed in this brief introduction
is physical therapy that is specific to the patient’s
diagnosis. Without the appropriate physical therapy,
the injection techniques may offer only temporary
relief from pain. Using therapy in conjunction
with injections has given me, and my patients,
the best results.
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