According to the National Institute of Neurological Disorders and Stroke, a headache is the most common neurological ailment in the United States. The second most common neurological ailment? Low back pain—a disorder Babak Bazrgari, Ph.D. and his Human Musculoskeletal Biomechanics Laboratory are researching within University of Kentucky’s Center for Biomedical Engineering.
How prevalent is low back pain? According to epidemiological studies, Bazrgari says up to 85% of the U.S. population may experience low back pain during their lifetime. With regard to frequency, at any given time up to ~ 33% suffer from low back pain and up to ~ 65% have low back pain on an annual basis.
Not only is low back pain widespread, according to NINDS, it also accounts for $50 billion in health care costs annually. It is the number one cause of job-related disability and is often blamed for workplace absences. Hence, accounting for indirect cost due, for example, to lost workdays and reduced production, the total cost of low back pain to the U.S. economy easily exceeds $100 billion. Low back pain is a serious problem socioeconomically, says Bazrgari and, despite advances in our knowledge of human trunk behavior and low back pain, individuals and health care professionals can’t efficiently control and manage low back pain partly because of one glaring fact:
“We don’t know or can’t determine the exact cause of low back pain for most cases at present,” Bazrgari says, pointing to a list of risk factors. “We know a number of risk factors associated with low back pain, but we don’t know everything about how they are related. That is where our research is focused.”
Some risk factors are occupational-related activities—anything job-related that affects the back, such as physically demanding lifting, carrying and pushing as well as non-physically demanding tasks involving a prolonged sedentary working posture. Another occupational-related risk factor for low back pain is vehicle-induced vibration to the driver’s trunk, particularly in off-road vehicles.
There are also non-occupational factors for low back pain, such as age, gender, psychosocial influences such as stress, job satisfaction and even smoking. All of the above have shown correlation to the problem of low back pain, although no single factor covers the whole spectrum of exactly what causes it. As a result, “approximately 85-95% of low back pain cases are categorized as nonspecific in cause, which has led to our inability in offering the most efficient treatment. This highlights the challenges for clinicians and may explain patients’ frustrations in selecting a treatment from a wide range of currently offered treatments for low back pain,” Bazrgari says.
Current evidence suggests abnormal mechanics of the human trunk are the most important cause of low back pain. As such, for Bazrgari, understanding how exposure to these risk factors for low back pain or receiving a particular treatment affect the mechanical behaviors of the active and passive tissues in the human trunk is necessary for designing effective prevention, treatments and rehabilitation procedures. “What we learn has future application for controlling the level of exposure to low back pain risk factors in daily life and at work and potentially as biomarkers to assist clinicians in developing/tracking treatment protocols,” he explains.
In addition to the challenge of many possible factors contributing to low back pain, Bazrgari also faces limitations as far as what his lab can actually see and measure as related to mechanical behavior of the human trunk. “We are looking at ways to quantify or measure the mechanics of the spine within the trunk because we can’t actually get into the spine and measure what happens when someone lifts or is knocked off-balance,” he says. “Instead, we use computational modeling to estimate the force load and stability of the spinal structure.”
A kinematics-driven approach which combines computational modeling with in vivo experimentation has proven to be effective for assessing the risk of injury during manual material handling, trunk motion, whole body vibration and sudden loading and unloading—studies Bazrgari conducted while earning his Ph.D. from École Polytechnique de Montréal and during his post-doctoral work at Virginia Tech. “Some of our research involves having individuals perform a simple lifting task in order to determine what factors enable the trunk to remain stable. We have also done sudden perturbation experiments where a subject is jolted without warning, but kept absolutely stable so we can study the biomechanics of the trunk without any change in muscle response.”
One current aspect of Bazrgari’s research targets a segment of the population quite susceptible to low back problems—the elderly. “With our combined in-vivo experimental and modeling approach, we can begin to understand how age-related changes in our body affect mechanical behavior of our trunk,” he says hopefully. “Understanding age-related changes in trunk mechanical behavior and their effect on spine biomechanics will move us closer to the goal of identifying key years for preventative care, and will serve to inform relevant communities on appropriate control levels for risk exposure among older individuals.”