Hanger study in the works on effects of microprocessor knees on K2 amputees

LAS VEGAS — A study led by Ken R. Kaufman, PhD and Kevin Symms, CPO, is measuring the effects of microprocessor knees on K2 amputees, Kaufman announced at the Hanger Education Fair and National Meeting.

Kaufman is W. Hall Wendel, Jr., Musculoskeletal Research Professor and co-director of the Biomechanics and Motion Analysis Laboratory for the Mayo Clinic. Symms is director of Clinical Operations for Hanger.

Because microprocessor knees (MPKs) were no longer considered “medically necessary” by health insurance companies, Kaufman began the research to provide evidence of the efficacy of MPKs. Kaufman led two previous studies of MPKs, in 2007 and 2008, which showed that K3 amputees experienced improvements in gait and balance; an equal amount of energy efficiency; and a decrease in rate of perceived exertion when given MPKs. Additionally, their total energy expenditure increased and “that means that they were more active in the microprocessor knees. That was a good thing. They spontaneously became more active when using a microprocessor knee because they had [fewer] stumbles and falls. So their quality of life went up,” Kaufman said.

Ken R. Kaufman

In 2007, after a group of researchers and a patient presented the findings to a group of Blue Cross Blue Shield (BCBS) medical directors, the BCBS policy changed to state that MPKs would be considered medically necessary for qualified amputees.

“The qualification was based on the K level. Somebody who was a K3 or a K4 was qualified to receive a microprocessor knee. But an individual who was a K2 [patient] was not. The distinction there is the [difference in] variable cadence. Now we are going to try and see if we can affect policy for patients who are a K2 [level] amputee … We are going to compare the effectiveness of MPKs for individuals who are K2 amputees,” Kaufman said.

The study is called FASTK2. Kaufman and colleagues will examine the patients with their current knees, will provide microprocessor knees to compare function, and then will return the patients to their original knees and study any additional changes that take place. The study is focusing on unilateral transfemoral amputees older than 55 years who are classified by at a K2 level by the PAVET. All microprocessor knees currently on the market are included in the study and supplied by their respective companies.

Kaufman said the study will examine both patient function and patient satisfaction. In addition to measurements in a laboratory setting, the researchers will conduct tests outside of the lab in a “free living environment” which he said will make the results more relevant for reimbursement purposes.

Kaufman and colleagues gathered preliminary results from a group of 10 patients by measuring their activity levels, prosthetic use, number of stumbles and falls, percentage of the day spent bearing load on the prosthetic limb and cadence. The preliminary data shows that K2-level patients given MPKs were taking less than 1,000 steps per day, were load bearing for about 13% of each day and had a variable cadence. The fact that each patient has a different cadence is crucial to Kaufman.

“That is interesting to me, because that says that they really do qualify for a microprocessor knee,” Kaufman said. “There is a lot of capacity for them to do a lot more activity.”

Hanger practitioners who would like to recommend patients for the study should contact Symms. — by Amanda Alexander.


Kaufman K. Functional assessment and satisfaction in K2 amputees (FASTKs): A comparative effectiveness study of MPK vs NPMK knees. Presented at: Hanger Education Fair and National Meeting. Feb. 3-6, 2015. Las Vegas.

Disclosure: The American Orthotic & Prosthetic Association (AOPA) is providing funding for FAST2K. Kaufman reports no relevant financial disclosures.

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