| In 1963, Lyman Smith coined the term 'chemonucleolysis' to describe the treatment of herniated discs with intradiscal injections of an enzyme extracted from papaya, called, chymopapain. Chymopapain acts by digesting the jelly-like inner prtion of the disc known as the nucleus pulposus, while at the same time, leaving the outer portion, the annulus fibrosis, essentially intact.
After many years of animal testing and FDA studies, in 1981, a randomized study, sanctioned by the FDA, on 108 patients revealed success rates of chymopapain at 82% versus 41% in the placebo treated group with no serious complications. At about the same time, a larger study included 1500 patients and revealed a sucess rate of 90% with only four reported cases of anaphylaxis (an acute allergic reaction).
In November of 1982, largely on the basis of these studies, chymodiactin received FDA approval. Over the ensuing years approximately 120,000 patients received chymopapain, unfortunately, 46 individuals experienced serious neurologic complications, including paraplegia and transverse myelitis. By 1984 the FDA had modified the administration procedures in an effort to minimize these complications. Currently, the complication rate is believed to be about 0.2 to 0.5%.
In spite of the concern for untoward reactions, in depth comparison reveals a rate of significant neurologic complications to be at 4.7 per 10,000 patients, or six times less than traditional open discectomy procedures. The infection rate is 1.8 per 10,000 versus 30.7 per 10,000 with surgery.
Who should have chemonucleolysis?
Approximately 80-85% of patients who experience leg pain from disc problems will respond favorably to conservative methods such as bed rest, exercise, anti-inflammatory drugs, body corset, epidural blocks, physical therapy, and traction. Only when all conservative methods have failed should more aggressive treatment be considered. Chymopapain is therefore intended for treatment of unremitting leg pain (sciatica) from a proven herniated disc that has failed to respond to all non-operative methods—the ideal candidate for chemonucleolysis is also the appropriate candidate for elective disc surgery by other methods, however the reverse is not always true.
Who should NOT have chemonucleolysis?
Anyone who has an allergy to papain or papaya should absolutely NOT undergo this procedure. Further, the effect of chymopapin on the growing fetus is unknown, therefore pregnancy is a contraindication. Progressive neurologic deficits including the loss of bowel and/or bladder control should NOT be treated with chymopapain.
How is chemonucleolysis done?
As shown below, the patient is positioned either on his/her side or stomach on the operating table. Under sterile conditions, an x-ray machine is used to guide the introduction of a needle into the intervertebral disc at the appropriate level. A small amount of dye is injected into the disc in order to assess the integrity of the disc as well as, accurate needle placement. Next a small 'test dose' of the enzyme is placed into the disc. If no adverse reaction is noted within ten minutes, the appropriate therapeutic dose of chymopapain is then injected.
Conclusion
Despite its somewhat controversial history, chemonucleolysis has resulted in significantly fewer complications than those reported for open surgical interventions. After better than a quarter century of clinical use and scientific scrutiny, chemonucleolysis has been firmly established as a safe and effective treatment for sciatica due to a proven herniated disc. |
