The Multifidus Muscle - Key to Spinal Stabilization?

Recently, researchers at UC San Diego used laser to measure the strength of the multifidus, a small muscle in the back. The results, published in the Journal of Bone and Joint Surgery, may influence the future of medical science as it relates to back pain and spine surgery. The research was supported by the Department of Veterans Affairs Rehabilitation, the National Institutes of Health and DePuy Spine, a device manufacturer.

Up until now, the thinking has been that because the multifidus is very small, it isn’t important to back health. Size aside, the multifidus has a very unique design that lends stability to the spine and keeps the individual upright. The researchers in this study concluded that the special design provides a scaffolding for the vertebral column. They identified short stiff muscle fibers packed inside a long finger-like covering, and said this particular construction is responsible for the extra strength and support the multifidus gives to the spine.

A small 2006 posture study published in the European Spine Journal, found that in people with back pain, the multifidus is working to the max well before the spine is vertical. In study subjects who didn’t have back pain, the multifidus was able to continue contracting until the trunk was erect.

Also the sarcomere, or the area where muscle contraction happens, is much smaller than in other muscles. But when the multifidus is put on a stretch, as when you bend forward, it actually gets stronger. This is unlike most muscles which, when lengthened, lose their strength. Something different is at work in this muscle!

"Our research shows that it’s actually the strongest muscle in the back because of its unique design," states Richard L. Lieber, PhD. Lieber is the director of the National Center for Skeletal Muscle Rehabilitation Research, a professor and Vice Chair at UCSD’s Department of Orthopedic Surgery, and a senior research scientist at the VA in San Diego.

These findings may influence the future of spine surgery, according to Steven R. Garfin, MD, professor and Chair of Department of Orthopedic Surgery. Garfin says this is because the way surgery is currently performed may actually disrupt the multifidus, which, in turn, may disrupt the spine’s ability to maintain upright posture.

Minimally invasive spine surgery usually results in less interruption of and trauma to soft tissues than traditional back surgery.

Some rehab specialists who work extensively with back exercises already knew about the special capacity of the multifidus muscle. Physical therapist Jim Johnson, for example, offers an exercise program for chronic back pain sufferers that is based on the multifidus. He believes that the multifidus plays a role in almost all non-neurological back pain.

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