Prosthetic Knee Type Affects Care Costs for Amputees

The average additional cost in the six months following a fall for transfemoral amputee patients requiring an emergency department visit was $18,000. For patients who had to be hospitalized, this extra expense was more than $25,000.

Medicare and other insurers that pay for only basic mechanical artificial knees and legs instead of more sophisticated prosthetics with microprocessors could pay more in the long run because of falls associated with the low-tech appendages, a Mayo Clinic study has found.

In a new study published in Prosthetics and Orthotics International, Mayo researchers examined the direct medical costs of falls in adults with amputations above the knee in an effort to “provide a comparison for policymakers when evaluating the value of more expensive … technologies.”

Of the 185,000 transfemoral amputee patients each year, only 25%-30% receive a prosthetic leg and knee, and insurance policies for most only cover basic mechanical knees. Despite growing data that newer technology reduces falls and improves physical capabilities, only high-functioning patients are deemed eligible for a knee with microprocessor technology.

Mayo researchers said they are challenging that standard.

“We want to help provide the best quality of life and prosthesis for each individual,” said study lead author Benjamin Mundell, a health economist and a student at Mayo Clinic School of Medicine. “It is important to look beyond the initial cost differences of a microprocessor knee compared to a mechanical knee and understand what downstream costs might be avoided with a better prosthesis.”

“Microprocessor knees are designed to help improve balance and reduce falls,” he said. “The fear of falling for those with mechanical knees likely reduces their overall physical activity and if they do fall and require hospitalization, the cost of care is almost as expensive as a microprocessor knee.”

The team examined the medical records of 77 patients in Wisconsin and Minnesota who received a transfemoral amputation between 2000 and 2014. They found that 46 of these patients had received a prosthetic knee. Of these, 22 patients logged 31 falls that resulted in an ED visit or hospitalization.

Using standardized Medicare cost data, the researchers found that the average additional cost in the six months following a fall for patients requiring an ED visit was $18,000. For patients who had to be hospitalized, this extra cost was more than $25,000.

“Understanding the costs is part of basic health economics,” said study senior author Kenton Kaufman, a biomedical engineer and orthopedics researcher at Mayo. “This study quantifies the cost of falls that require medical attention – providing evidence that it may not be economical to withhold microprocessor knees from patients with moderate ambulatory capabilities.”

Kaufman said the costs to patients are much higher than the study shows because the study doesn’t reflect indirect costs such as lost wages, and transportation and caregiving expenses.

Medicare K levels are used to determine which prosthetic device is medically necessary for a patient. To be considered eligible for the microprocessor knee, a patient needs extensive documentation that he would use the leg more than the normal day-to-day walking, stairs, etc.

“For many, the default may be a mechanical knee, because it is easier to prove basic necessity than to ensure the rigorous documentation requirements for one with advanced – and more costly – technology,” Kaufman said. “One of the reasons we work on improving technology in prosthetic knees is to help individuals become more agile, more balanced and less likely to fall, but if people aren’t able to access this technology, they may become more vulnerable and less active than their condition would normally indicate.”