Low Back Pain
Incidence and Impact
Low back pain is extremely common in today's society. Seventy-five percent of all people will experience back pain at some time in their lives. The total cost in lost productivity is enormous. Back pain is the second leading cause of absenteeism from work, after the common cold and accounts for 15% of sick leaves. Back injuries cause 100 million lost days of work annually, and are the most costly injury for employers. The cost of a back pain injury claim far surpasses others. The average total cost per claim in 1989, was $18,365.00. Time plays an important role in back pain recovery. After 52 weeks of back injury disability and absenteeism, only 25% of injured workers return to work. After two years of disability, the return rate is zero. For 85% of back pain sufferers, the primary site of injury is the lower lumbar spine.
The good news is that the vast majority of back-injured patients, probably greater than 90%, will recover completely without surgical treatment. Only 2 to 3% of the population with back pain have a herniated disc and only 1% have compression of a nerve root (leg symptoms).
Chronic Low Back Pain/Failed Back
Treating chronic low back pain that has proven refractory to non-operative management can be challenging. The results of previous surgical treatments are often sobering. Re-operation rates on the spine have been reported at 6.9 - 37.7%. Heithoff et al, reported 25,000 - 50,000 failed back surgery syndrome cases occurring each year. For the aforementioned reasons the appropriate diagnosis, efficient treatment, and when indicated well - executed surgery, are of absolute necessity. Otherwise it is all too easy to add to the chronic "failed back" patient population.
Causes of Low Back Pain
Some of the common causes of back problems are disc injury (e.g., herniation and internal disc disruption, IDD) and degenerative discs. Disc degeneration affects about 12 million people in the United States, of which most are between the ages of 20 and 65. Approximately ten percent of patients with degenerative discs are candidates for some type of spinal surgery.
The intervertebral disc serves as a shock absorber, load distributor and spacer. As we age the disc normally undergoes degenerative change. The disc loses its ability to hold water, resulting in decreased ability to absorb shock and a narrowing of the nerve openings in the sides of the spine, which may pinch the nerves. The result is increased disc stiffness often accompanied by back and leg pain. The degenerative changes within the disc are universal and account for the majority of chronic low back pain seen in spine clinics.
Unfortunately there is not a 1:1 association of disc degeneration to pain. In one study 52% of degenerative discs were found to be the source of the patients back pain. The MRIis a relatively sensitive test for the detection of degenerative changes within the intervertebral disc, but is incapable of providing a pain association.
Additional testing is required to assign a "pain generator" status to the individual disc. Discography is accepted as the disc evaluation "procedure-of-choice". Discography investigates, and establishes the intervertebral discs role in the production of the patient's low back pain.
At times in the past the value of discography has been questioned. Current literature supports discography's worth as a diagnostic tool used to investigate painful spinal conditions.
Who is a candidate and when is discography indicated?
- A patient who experiences persistent spinal (cervical, thoracic, lumbar) pain.
- A disc abnormality is suspected.
- Non-invasive tests have failed to provide an explanation or source of pain.
- A pain correlation is desired.
Patients who have continued pain despite previous surgery are often discography candidates. There are many variations of the discography procedure. The method most commonly utilized at KU Medical Center is that of provocative discography. Provocative discography is the instillation of sterile saline (not dye) into the disc looking for reproduction of the patient's pain. Exact pain reduction supports the discs role as a "pain generator", documenting a specific diagnosis, and allows more aggressive intervention.
History of Discography
Discography was originally performed with dye, when existing imaging techniques did not provide information on the disc's internal architecture. In most present cases we utilize the MRI to identify disc abnormalities and the discogram to assign a "pain generator" status.
Historically, Lindblom (1940's) injected cadaveric specimens with red lead containing dyes and examined the pattern of distribution within the disc. Erlacher (1952), studied 200 cadaver disc specimens and found that discography accurately represented the disc anatomy. The discs were sectioned and studied for correlation. Wiley (1968) reported on 1092 patients, finding discography a valuable tool with very few complications. In one study of the MRI, significant disc abnormalities were demonstrated in 28% of symptom and pain-free individuals (28% false-positive rate). Clearly a procedure is needed to further define the MRI findings as contributing to the patient's symptoms. Discography is the only method that directly relates a radiographic image to the patient's pain.
Walsh et al (1990), performed provocative discography on ten asymptomatic pain-free volunteers. No pain was produced on injection. However, 50% demonstrated abnormal dye patterns. He felt the pain correlation the procedure had a specificity of 100%. Simmon's et al's (1990), suggested that treating painful spinal conditions based only on MRI results could lead to under treatment.
Colhoun et al (1988), studied the success of fusions performed with a discography proven pain correlation. Patient satisfaction was achieved in 88%. When the correlation was absent the satisfaction with the fusion procedure dropped to 52%. Discography has also been documented as helpful in diagnosing pseudarthrosis (failure-of-fusion), Byrd (1992).
Indications for Discography
We believe in the following indication, for discography:
- Failed conservative therapy
- Diagnostic tests - inconclusive (equivocal or inconsistent)
- Persistence of severe symptoms - surgery a consideration
Discography is an outpatient procedure, performed under biplanar fluoroscopy, local anesthesia and sterile conditions. When performed correctly and in "experienced hands" the main complication is a short period of increased pain. In short, discography has proven itself to be an invaluable diagnostic modality reserved for the investigation of painful spinal conditions where other non-invasive studies have been unable to provide or confused the diagnosis to allow further more aggressive treatment.
Interbody Cage Fusion
Once the disc has been established as the source of the patients chronic, refractory to conservative care, incapacitating, low back pain, one of the most exciting advances in spine surgery becomes available as a treatment modality.
The new interbody fusion systems utilize an innovative threaded titanium cage for spinal fusion. The technique is less invasive than other methods. The cages are small, hollow threaded titanium cylinders used to restore the degenerated disc space to or near its original height, relieving any pressure on the patient's nerves. The clinical outcomes of the cage interbody fusion study, which were reviewed by the FDA, have shown significant reductions in pain and increases in activity levels compared to other fusion methods.
During the surgery, portions of the painful disc and a small amount of bone are removed, allowing implant insertion. A small amount of bone is then taken from the pelvis and packed inside the cage implants. This allows the bone to grow through and around the implant fusing the vertebral bodies and relieves the patient's pain. The interbody cage fusion system is implanted from the front (anterior) when possible, as recovery and postoperative pain are lessened. However, the decision on surgical approach is based upon the patient's condition.
Advantages of Interbody Cage Fusion
Based upon the findings of the FDA clinical study and comparisons to other fusion methods, the cage interbody fusion system offers many advantages over traditional fusion methods.
The following are some of the advantages:
- The procedure has been found to have a low overall complication rate.
- The amount of blood loss during surgery can be much less than other types of spinal fusion.
- Postoperative pain may be minimized through a decrease in the amount of surgical intervention.
- Operative procedure and length of stay in the hospital can be less than other fusion methods.
- Return to daily activities can be much quicker.
Results of Interbody Cage Fusion Procedure
These findings follow the general trend in medical care toward less invasive surgical techniques that provide better outcomes for patients. The first FDA controlled clinical study on interbody cage fusions includes 947 patients. The clinical success rates for patients at two years after surgery were measured in the following areas:
- Patients reporting favorable outcome - 89%
- Function maintained or improved - 94%
- Pain improvement - 85%
- Strength maintained or improved - 94%
- Fusion rate - 91%
As the numbers reflect, an exciting advance compared to previously available techniques.
Material provided by Dr. Glenn M. Amundson
Used by Permission