In the past decade, the rate of back surgery among Medicare patients has increased by more than half, driven by factors including new technology to fuse damaged vertebrae, more advanced imaging to diagnose injury, generous federal reimbursements and greater demand.
Yet even as the numbers swell, there is no clear-cut science for treating back pain. Some doctors favor surgery, while others recommend exercise, rehabilitation and other conservative approaches.
The result is a jigsaw pattern of medical care in which the patient's chance of having surgery often is decided by where he or she happens to live.
In Fort Myers, Medicare patients are twice as likely to have back surgery as those in Miami.
Had Fort Myers's surgeons operated at the more conservative Miami rate, there would have been 4,800 fewer back surgeries from 1992 to 2001 and Medicare would have saved millions of dollars, according to an estimate by James N. Weinstein, chairman of the Department of Orthopaedic Surgery at Dartmouth Medical School. Weinstein has tracked variations in the number of spine surgeries in South Florida for a decade.
Medicare patients in Fort Myers underwent spine surgery at a rate of 6.9 per 1,000 in 2001 -- the latest year for which figures were available. In Miami, the rate was 3.2. Nationally, it was 4.5.
Back surgery is a growing cost to Medicare. In 2003, the government paid about $1.6 billion to hospitals for more than 167,353 spine procedures, not including doctors' fees. The average charge per surgery was $40,000.
Dartmouth researchers estimate that as much as one in three dollars spent by Medicare goes to unnecessary care. In that sense, variations in back surgery in South Florida provide a glimpse of Medicare's inefficiencies.
"It's highly improbable that Medicare retirees living in Fort Myers prefer back surgery two times as often as residents of Miami," Weinstein said. "So if it's not the patients, what is it?"
Weinstein points to what he calls the "surgical signature" of doctors -- idiosyncratic patterns in the likelihood of a doctor choosing to operate. The greater the scientific uncertainty in treatment options, Weinstein said, the more variations appear.
Less clear is the role of hospitals. For hospitals that offer spine surgery, the financial rewards can be substantial. In 2001, spine surgery accounted for more than half of all profits from orthopedic procedures in hospitals but only 21 percent of the volume, according to a study done for the American Academy of Orthopaedic Surgeons.
"It can be very profitable, especially at centers with big volumes," said James H. Herndon, past president of the group and a Harvard Medical School professor. One new, aggressive surgeon can increase the rates in a community "if he comes into an area where surgeons are conservative," Herndon said.
In Fort Myers last year, surgeons at the three hospitals that are part of the Lee Memorial Health System performed 447 spine procedures on Medicare patients, generating nearly $2.8 million, according to data provided by the system. Medicare reimbursements to the three hospitals for spine operations have grown by nearly 50 percent in the past five years.
Chuck Krivenko, the system's chief medical officer, said he is hard-pressed to explain the high rates of back surgery. At first, he suggested it must be because of the annual winter influx of elderly visitors. But the Dartmouth researchers account for seasonal visitors by counting their surgeries as though they occurred at their place of year-round residence.
"I can't explain it," Krivenko said. The neurosurgeons who perform spine surgeries at Lee Memorial "are not what I'd call aggressive neurosurgeons. We have a very good group of what I consider conservative neurosurgeons . . . and we have some of the best outcomes," he said.
Nevertheless, Krivenko said, because treatment for back pain remains discretionary, many doctors are going to opt for surgery. "If the only tool you have is a hammer, everything looks like a nail," he said.
Not necessarily, Weinstein contends. At his hospital, Dartmouth-Hitchcock Medical Center in New Hampshire, patients with back pain are given educational materials and allowed to choose. They often opt not to have surgery.
"What we have found," Weinstein said, "is that patients tend to make good decisions when presented with good information."
Medicare data appear to back up Weinstein. In 2001, the rate of back surgery among Medicare patients in his area was 2.3 per 1,000, among the lowest in the nation.