Biomechanics

Allan Tencer, PhD
Section Head

	HIPRC Overview Overview Injury Prevention at Work Acute Care Biomechanics Epidemiology Rehabilitation Collaborative Efforts

Applying mechanical principles to the body to study injury causation and to evaluate injury treatment methods

"In order to best understand the relationship of biomechanics to injury control, it is useful to think of an injury as a mechanical event, says Allan Tencer, Ph.D. ÒBy simulating what happens in an injury, we then give epidemiologists valuable information to identify the most important risk factors. For example, take our current investigation of falls in the elderly. First we look at the mechanics involved, such as how people fall, and then relate that information to varying factors about the stability of different types of shoes, such as their stiffness and friction with the walking surface."

Founded in 1988, the laboratory is a collaborative effort between Harborview and the University of Washington Department of Orthopaedics, with support from the Harborview Injury Prevention and Research Center (HIPRC). It is one of the few labs in the country dedicated to the biomechanics of trauma-related care.

Reducing the toll of motor vehicle injuries

Motor vehicle injuries remain the leading cause of injury death in the U.S., and for people under the age of 32, motor vehicle crashes re the leading cause of all deaths. Despite improvements in vehicle design and roadways, the toll in injuries, deaths and medical expenses, remains a serious national problem. Investigators in the Biomechanics Section research the motor vehicle injuries that occur most frequently, as well as what can be done to reduce their impact.

Whiplash injury to the cervical spine is most often seen in rear-end vehicle collisions. The resulting damage to the body is difficult to diagnose, particularly in low-speed crashes, yet generates a multitude of insurance claims. HIPRC researchers are investigating to what degree impact strains spinal tissue, and which tissues are most vulnerable. Using a simulator to measure these mechanical strains, the researchers plan to work with clinicians to develop more specific diagnostic tests and thus streamline treatment.

Researchers also are looking at passenger deaths related to side-impact vehicle collisions, in which most deaths are due to injuries of the neck or spinal cord. One cause of such life-threatening injuries, the HIPRC researchers suspect, may be sideways whiplash, where the body snaps from side to side rather than back to front. To document this possibility, the lab is using data from actual crashes and is simulating them with a sled-and-track device to measure tissue strain and spinal movement.

Another related project, aimed at prevention, is investigating how headrest design and position affect the potential for whiplash injuries. This work addresses a national insurance group's contention that the headrests in most vehicles do not protect against whiplash. The Biomechanics Laboratory has also done important research on many other parts of the body, often to assess surgical techniques and implants in orthopedic trauma. Several projects involving injuries of the thumb and wrist, for example, yielded information that has improved the results of restorative surgeries and significantly reduced complication rates.

Breaking the downward spiral of hip fractures

Each year, nearly 250,000 Americans sustain broken hips. Hip fractures account for 30 percent of all bone fractures, and for half of all hospital beds occupied by fracture patients. Unlike other types of fractures, hip fractures P especially among older patients P tend to initiate a downward health spiral with complications that eventually kill one-quarter of patients over age 70.

If the hip joint is functional, surgeons prefer to spare rather than replace it, using three long screws to stabilize the broken bone. But in patients with osteoporosis, the bone tends to be thin, causing the screws to eventually fail in 30 percent of cases and requiring the patient to eventually undergo hip-replacement surgery.

HIPRC researchers helped in solving this problem by testing an injectable bone mineral cement and developing standards for its use. The cement resembles toothpaste but quickly and effectively strengthens weak bones at specific points, ensuring the success of the original repair process and sparing patients a second surgery.

Computers offer surgical feedback

The vast amount of computer technology developed in the last decade holds particular promise for biomechanics, said Tencer. Not only can researchers create three-dimensional images of complex joints, such as those of the foot and wrist, but they also can attach sensors directly to bones, manipulate those bones, and see the results instantly on the computer screen. It's the kind of technology Tencer says belongs in the operating room for the surgeons' use, and exemplifies the Biomechanics Section's dedication to increasing the precision of trauma prevention and treatment.

"We will learn an incredible amount," he says. "We can put the sensors on patients, manipulate the shoulder or foot to show what's wrong, then do the surgery and manipulate it again to show the effect of the procedure in real time. Surgeons now can really only guess at the results."

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