Two faculty members in UAB's Injury Control Research Center are collaboration on a study of acetabular fractures that may result in the manufacture of safer cars. In their study, biomechanical engineer Martha Bidez, PH.D., and orthopedic surgeon Jorge Alonso, M.D., challenge the current accepted theory that side-impact automotive accidents do not cause fractures of the acetabulum (the pelvic socket portion of the hip joint).
According to Bidez, the automotive industry has been researching side-impact crashes for quite a while, exposing full-body cadavers to side-impact crash conditions. They found large pelvic and pubic bone fractures but very few acetabular fractures, so they concluded that motor vehicle crashes do not cause joint fractures.
Bidez credits Alonso's expertise in setting acetabular fractures with bringing this conclusion into question. "Patients with acetabular fractures with bringing this conclusion into question.
"Patients with acetabular fractures come from all over the Southeast to be treated by dr. Alonso, she says. "and many of these patients received their injuries in side-impact crashes."
Muscle Loading
Bidez and Alonso recently completed a pilot study on side-impact automotive crashes and acetabular fractures, with Alonso providing the patients and Bidez collecting data and performing testing.
At the outset, Bidez says they knew there was some element in real-world crashes that wasn't being duplicated in the cadaver testing. They suspected that element to be "muscle loading" -the effect of bracing and tension muscles before impact. Their hypothesis was that acetabular fractures occurred only in the presence of muscle loading.
Bidez used cadaveric pelvises bolted into biomechanical test frames instead of full-body cadavers secured only by seat belts, as in the auto industry tests. The frames were subjected to simulated side-impact crashes - and in 20-25 percent of these models acetabular fractures occurred. Bidez believes that bolting the pelvises into the frame more closely simulated what takes place in muscle loading.
Safer Automobile Design
This fall, Bidez and Alonso will begin a much larger study funded by the Centers for Disease Control and Prevention. This five-year study will further test their hypothesis and, they hope, will ultimately result in recommendations to the automotive industry for safer car designs.
The study will take a three-pronged approach. In the first phase, the UAB research team will study data collected from the National Data Base Sam0pling system on the injuries sustained in side-impact crashes, velocities of various vehicles, and angles of impact.
The second phase will include more test on cadaveric pelvises as well as test on human volunteers in simulated crash conditions. This phase also will include impact testing with different automotive padding materials.
The third phase of the study will involve analysis through three-dimensional computer models of the human pelvis. This model will allow researchers to simulate muscle loading and to program impact loads and directions into the test. In addition, they'll be able to do precise testing of car door and seat designs, as well as thickness of padding materials.
"This computer model allows us unlimited testing," says Bidez. "We can enter as many variables into the system as we want and study the results."
The results of the study are important to the automotive industry, Bidez comments, because safety has become the top selling point for cars.