Prosthetic Categories

How Microprocessor Feet Improve Mobility

    Since its commercial introduction in 2006, microprocessor prosthetic feet have been known to offer prosthetic users various benefits, including improved performance while negotiating ramps and stairs, reduced pressures against the residual limb within the socket, and increased prosthetic mobility. However, most of the studies supporting microprocessor feet have been endorsed by product manufacturers and derived from measurements taken in controlled laboratory environments.

     Microprocessor feet significantly improve a user's prosthetic mobility and physical function.

    So, researchers from the Hanger Institute for Clinical Research and Education in Austin, Texas, sought to determine how microprocessor feet affected prosthetic mobility and physical function among below-knee amputees in the community setting.  

    The other aim of this study was to get initial findings on the effect of microprocessor feet on reducing the intensity of back pain and residual limb pain, as well as improving the user’s ability to ascend and descend steep hills using single-item questions from the Prosthesis Evaluation Questionnaire.

    The study  

    The participants  

    Weber et al. perused patient records from a national provider of lower limb prostheses. They determined that patients were eligible for the study if they were not already using microprocessor prosthetic feet and had a written prescription from a doctor to transition to a microprocessor foot.

    A total of 20 patient cases qualified, with an average age of 56.65 years. Over 60% of the sample was male, and the most common cause of amputation was vascular disease or diabetes. The subjects used non-microprocessor prosthetic feet that met the standards of the K3 community ambulator based on the Medicare Functional Classification Levels. Being classified K3 means that the patients have the ability or potential to walk at variable speeds.

    Most of the subjects got the Blatchford Elan microprocessor foot, with some participants using the Proteor Kinnex, Ottobock Meridium, and Össur Proprio. Although all the microprocessor prosthetic feet were fitted and aligned by prosthetists, the subjects didn’t receive any standardized physical therapy associated with obtaining new prosthetic feet.

    The study design  

    The researchers collected two patient reports to analyze. First is a filled-out questionnaire before the subjects use a microprocessor foot, and the second is another questionnaire at a follow-up appointment after they have used the new microprocessor feet. The researchers evaluated participants’ experiences based on their answers on a custom PROMIS Physical Function questionnaire and a combination of independent questions from the Prosthesis Evaluation Questionnaire.

    Some of the questions included in the PROMIS Physical Function questionnaire sought to understand the patients’ experiences when doing the following:

    • bending down to retrieve something from the floor,

    • carrying a laundry basket up a flight of stairs,

    • getting in and out of a car,

    • going for a 15-minute walk,

    • going up and down the stairs at an average pace,

    • sitting on a toilet and a low soft couch and then standing up, and

    • walking a block. 

    Meanwhile, questions taken from the Prosthesis Evaluation Questionnaire include assessments of the ability to walk up and down a steep hill, the intensity of back pain and residual limb pain, prosthesis fit and weight, and sitting comfort.


    Physical function  

    In a univariate analysis, the researchers found a significant increase in the patients' PROMIS Physical Function scores when they used microprocessor feet than when they used passive prosthetic legs.

    How microprocessor feet improve mobility table 1

    In a multivariate analysis, the researchers saw similar findings. When controlling for unmeasured variables, such as age, cause of amputation, gender, and assessment intervals, the participants’ PROMIS Physical Function scores increased by 5.40 points.  

    How microprocessor feet improve mobility multivariate analysis findings

    Prosthesis evaluation questionnaire  

    The researchers also used this study to analyze how microprocessor prosthetic feet impact the users’ back pain, residual limb pain, and hill ascent and descent. The researchers found that all concerns improved when the user transitioned from passive prosthetic feet to microprocessor feet. 

    The participants also reported significant improvements in the intensity of back pain, as well as ascending and descending steep hills when wearing the microprocessor prosthetic feet.

    The bottom line  

    This analysis, published in July 2022 in the SAGE Journals, has demonstrated how microprocessor prosthetic feet perform outside the laboratory setting with the subjects transitioning from passive prosthetic feet to microprocessor feet. The researchers found that below-knee prosthetic limb users who recently transitioned to using microprocessor feet experienced a significant improvement in their prosthetic mobility and physical function.

    The findings support previous studies conducted in clinical walking environments. These studies showed the advantages of using microprocessor prosthetic feet, such as increased prosthetic mobility, increased toe clearance in swing, improved experience when negotiating ramps and stairs, and reduced pressure against the residual limb within the prosthetic socket.

    In addition, the researchers proved that using microprocessor prosthetic feet reduced the intensity of back pain and residual limb pain and improved the experience of ascending and descending steep hills.

    The researchers also noted that the findings from this study could help inform clinical decision-making.

    What do you think of the study’s findings?