Obesity Threatens Leg Survival After Injury

A new study of more than 19,000 knee dislocation cases in the U.S. between 2000 and 2012 provides a painful indication of how the nation's obesity epidemic is changing the risk, severity and cost of a traumatic injury. The study, “Increased Incidence of Vascular Injury In Obese Patients with Knee Dislocations” was published in the October 23, 2017 issue of the Journal of Orthopaedic Trauma.

"Obesity greatly increases the complications and costs of care," said lead author Joey Johnson, M.D., orthopedic trauma fellow at the Warren Alpert Medical School of Brown University and a physician at Rhode Island Hospital. "As the rate of obesity increases, the rate of knee dislocations increases. The total number of patients who are obese is increasing, so we are seeing more of these problems."

Knee dislocations occur when the knee has multiple torn ligaments in the joint. Often this happens in vehicle crashes or contact sports like football. Johnson and co-author Christopher Born, M.D., a professor of orthopedics at Brown University, looked into the role of obesity because, over the last five years, they have seen an increase in knee dislocations among obese patients. They have seen an increased risk of vascular injury to the main artery that runs down the leg behind the knee.

They have also seen an increase in "low-energy" causes of dislocations, especially among obese patients. They found that obese or morbidly obese patients made up an increasing share of knee dislocation patients, rising to 19% of patients in 2012 compared to just 8% in 2000.

Vascular injury is a particularly severe complication because if undiscovered and untreated, it can lead to amputation of the leg. The doctors found that the odds of vascular injury during a knee dislocation were twice as high among obese people as it was for normal-weight people.

Johnson said this finding is particularly insidious because a common clinical assumption is that vascular injury might be less likely among people suffering a low-energy knee dislocation. He and Born said the new research suggests physicians should be especially vigilant about vascular injury in obese knee dislocation patients, regardless of the cause.

"Orthopaedic and emergency medicine clinicians should have a heightened awareness for the potential of a knee dislocation in the obese patient following a low-energy fall," Born said. "That subset of obese patients who come in with complaints of knee pain need to be carefully evaluated so as not to miss a potentially catastrophic vascular injury."

The stakes, Johnson added, could be the leg itself.

"You don't want to be fooled," he said “the cost pf care is also affected. Patients with vascular injury, which was twice as likely among obese patients, stayed in the hospital for an average of 15.3 days, while patients without vascular injury stayed for an average of 7.4 days. Average hospitalization costs were $131,478 for vascular injury cases and $60,241 for those who had no vascular damage.