Why do some bone cells knit together neatly following a fracture or amputation, while others grow wildly into soft tissue that can limit range of motion and cause problems with prosthetics?
Dr. Erika Mitchell, assistant professor of orthopaedic trauma, has won a $1.3 million, three-year grant from the U.S. Army Medical Research and Materiel Command to find out.
The condition called heterotopic ossification—excessive bone growth—typically occurs in 11 percent to 25 percent of patients who’ve experienced serious trauma such as auto accidents. Yet, it’s being seen in a staggering 63 percent of military casualties.
“That number is extremely high, and extremely problematic,” says Mitchell. “Bone growth can become so excessive that it needs to be removed. In the case of amputation stumps, the stumps have to get shorter. That causes prostheses problems and requires multiple surgeries, which we’d like to avoid.”
Mitchell hopes that learning what causes the excess bone growth will one day mean it can be “turned off”—or on, in cases where bones don’t heal. “If we could understand how this excessive bone growth occurs, maybe we could better understand how we could create bone growth when needed.”
Researchers are not sure why, but several studies indicate a link between serious head trauma—a common injury on battlegrounds—and heterotopic bone formation. Yet, it doesn’t occur in every patient with head trauma and a fracture. That leads Mitchell to suspect that some people have a genetic predisposition toward the condition.
Mitchell and her team will examine clinical information gathered from patients to find those with heterotopic ossification. They’ll divide those patients based on categories such as the severity of their injuries, medications they were using, and their overall physical condition at the time of injury. Then Mitchell will explore their genetic data, hoping to identify underlying gene markers that can be linked to the condition.
The premise is promising, says Dr. John Morris Jr., professor of surgery and director of the Division of Trauma and
Surgical Critical Care. “This study looks at the area that is just coming into focus: the role of the genome in response to traumatic injury,” he notes. “The hope is that we are going to find multiple pathways where small variations in the genome alter outcome following trauma.”
The grant that funds the study, part of the U.S. Department of Defense’s Orthopaedic Trauma Research Program, is a cooperative venture between Vanderbilt’s Division of Orthopaedic Trauma and the Division of Trauma.