BONIFAY, Fla. - Sandra Duck thinks she's the victim of an undeclared Medicaid boycott. And she's probably right.

BONIFAY, Fla. - Sandra Duck thinks she's the victim of an undeclared Medicaid boycott. And she's probably right.

When her artificial right hip became infected with the superbug MRSA in late 2009, Dr. Dale Mitchum, a general surgeon, drained, cleaned and closed the infected area. But when the infection returned in early 2010, Mitchum knew Duck needed another hip replacement surgery, which he couldn't perform. He tried to find an orthopedic surgeon who would operate. More than a year later, he's still trying.

"I cannot find a living soul that will touch her," he said recently. "And I've tried everywhere, from Tallahassee to Pensacola."

Doctors in several states outside Florida also have refused to operate on Duck, who's covered by Medicaid, the state-federal health insurance program for poor people and those with disabilities. Because of the program's history of low payments, fewer than half of U.S. doctors and other health care professionals accept Medicaid patients, according to a recent study.

For those that do, getting an appointment sometimes can take months because of the high demand, particularly among specialists.

The problem is worse in rural areas such as Bonifay, in the Florida Panhandle. While 20 percent of Americans live in less-populated parts of the country, only 10 percent of U.S. doctors practice there. That's why 77 percent of the nation's 2,000-plus rural counties are designated as health professional shortage areas, according to the National Conference of State Legislatures.

Nationwide, the lack of doctors is a growing problem that will only worsen as some 27 million people get health coverage by 2016 as part of the Patient Protection and Affordable Care Act. The Association of American Medical Colleges projects a shortage of 29,800 primary care doctors and 33,000 specialty doctors in 2015 alone.

If left unaddressed, the shortage of doctors and their rejection of Medicaid patients could severely hamper the health care overhaul next year, when 5 million to 8 million Americans will gain Medicaid coverage under the law.

While the health care law also provides for steeply increasing Medicaid fees to doctors this year and next year, some physicians worry that the payments would drop again in 2015.

The new law allows state Medicaid programs to cover non-elderly adults who earn up to 138 percent of the federal poverty level. That's nearly $16,000 for an individual in 2013 or about $32,500 for a family of four.

As of Monday, 26 states and the District of Columbia are slated to participate in the Medicaid expansion, while New York is leaning that way, according to the Advisory Board Company, a global research and consulting firm.

But as Duck's experience shows, a Medicaid insurance card doesn't guarantee care if there aren't enough physicians to treat the new enrollees or wide swaths of doctors simply won't see them.

Of more than 1 million physicians, therapists and counselors nationwide, only 43 percent accept Medicaid, according to a new study by HealthPocket, a technology firm that compares and ranks health plans.

The situation varies by city. The study found that only 31 percent of caregivers accept Medicaid patients in Washington and Detroit, 36 percent in San Francisco, 42 percent in Philadelphia and San Diego, and 47 percent in Seattle.

"If the current Medicaid acceptance rates hold true for 2014, timely access to care for those relying on Medicaid is likely to become more difficult as enrollees compete for an already inadequate pool of doctors," said Kev Coleman, the head of research and data at HealthPocket.