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  • Measuring the performance of prosthetic feet using Questionnaire.

    We plan to conduct a study to compare the performance of the prosthetic feet commonly used in our institute. For subjective assessments, we are going to use a “Prosthesis Functional Assessment Questionnaire” similar as the one used by [MacFarlane, et al 1991]. MacFarlane et al used questionnaire to obtain users' perception of the Flex Foot and the SACH foot. In their study, subjects reported significant reductions in exertion when using the Flex Foot at all three speeds (2.0, 2.5, and 3.0 mph) and all three grades (level, 8.5 percent grade incline and decline) tested. Underwood et al [Underwood, et al. 2004] compared the Flex Foot and the SAFE foot, using a rating scale of perceived stability and mobility. Their results showed that the Flex foot scored higher than the SAFE foot in all categories. However, there are concerns of using questionnaire to measure the performance of the prosthetic feet. Though the questionnaire are able to distinguish the difference between the tested feet in these studies, the questionnaire may not able to tell the difference among the feet used in our institute, e.g., College Park TruStep foot, Ossur Ceterus and VariFlex feet, Otto Bock Trias+ and Axtion feet, Blatchford Endolite Elite Foot, Freedom Innovation Renegade foot, since these feet may be less different than the feet compared in these studies.

    My questions are: (1) Is there study show questionnaire are able (or not able) to tell the difference among the feet? (2) Is there better alternative to the questionnaire for the same purpose? Any comment or suggestion is welcome. Thank you for your time.


    References:
    MacFarlane PA, Nielsen DH, Shurr DG, Meier K. “Gait comparisons for below-knee amputees using a Flex-Foot versus a conventional prosthetic foot.” J Prosthet Orthot 1991a; 3:150 –161.

    Underwood HA, Tokuno CD, Eng JJ. “A comparison of two prosthetic feet on the multi-joint and multi-plane kinetic gait compensations in individuals with a unilateral trans-tibial amputation.” Clin Biomech 2004;19:609–616.

  • #2
    Re: Measuring the performance of prosthetic feet using Questionnaire.

    Dear G. Luo,

    I think the core question is about what you mean with 'performance', in other words, what is it that you are interested in analyzing? Based on your interest (expressed in variables) you will then be able to find the correct measuring tool that - once applied - will hopefully provide you with the answer you were looking for!

    Specifically to your questions:
    (1) The references you cite were able to detect a difference in the prosthetic feet - therefore, your question does not seem to express what you would like to ask. Are you worried that the questionnaire might not be sensitive enough to show possible differences? And what, if differences are detectable in variables that are not taken into account by the questionnaire? Again - I think it would assist if you can clarify for yourself, what exactly it is that you would like to find out.
    (2) Alternatives might be energy consumption, GRF patterns of affected and non-affected sides, EMG etc. It all depends on what your overall objectives are!

    Hope this was of assistance. Good luck!

    With kind regards,
    Margrit Meier

    Comment


    • #3
      Re: Measuring the performance of prosthetic feet using Questionnaire.

      Dr. Margrit Meier

      Thank you very much for your response. For the study, I try to create a preference list of prosthetic feet for each test subject using questionnaire, as well as instrumental measurements. Therefore I will know which foot is most performing foot for a given patient, and which one is the least performing foot. For now I am focusing on subjective feedback from patients. I want to use questionnaire to obtain scores of each given activity for each foot from each patient. As you mentioned, my main concerns are if questionnaire are sensitive enough to show possible differences. A related issue is the reproducibility. If I ask a patient to evaluate a foot twice (the patient will not know if the tested feet are the same or not), will questionnaire produce consistent results?

      G Luo


      Originally posted by Marmei View Post
      Dear G. Luo,

      I think the core question is about what you mean with 'performance', in other words, what is it that you are interested in analyzing? Based on your interest (expressed in variables) you will then be able to find the correct measuring tool that - once applied - will hopefully provide you with the answer you were looking for!

      Specifically to your questions:
      (1) The references you cite were able to detect a difference in the prosthetic feet - therefore, your question does not seem to express what you would like to ask. Are you worried that the questionnaire might not be sensitive enough to show possible differences? And what, if differences are detectable in variables that are not taken into account by the questionnaire? Again - I think it would assist if you can clarify for yourself, what exactly it is that you would like to find out.
      (2) Alternatives might be energy consumption, GRF patterns of affected and non-affected sides, EMG etc. It all depends on what your overall objectives are!

      Hope this was of assistance. Good luck!

      With kind regards,
      Margrit Meier

      Comment


      • #4
        Re: Measuring the performance of prosthetic feet using Questionnaire.

        Dear G. Luo,

        Sorry for the late reply.

        Unfortunately, I do not know if questionnaires will be sensitive enough to detect preference differences of the prosthetic feet you are interested in. Something you may need to take into consideration once you discuss your study’s results, in case you think the results did not meet your expectations.

        What is the ultimate goal of your preference list? Would you like to be able to show that for a given activity, a particular foot seems to work best?? If so, how do you plan to account for individual preferences?
        An example for illustration: Let’s take cross-country running shoes: someone may choose type A over B or C despite the fact that his/her performance is similar with all three shoe types. It might be the style of the shoe, the design of it, or “simply” comfort - “it just feels right”! However, for a walk in the city, the same person would not use any of these types of shoes. This example is similar to prosthetic feet choice, but in contrast to people who do not rely on a prosthesis for their daily activities (i.e. most of us), amputees must perform all kinds of activities with the same prosthetic foot despite the fact that different activities may require a different foot.

        For your information, even if you do not tell your study participants about the foot fitted on their prosthesis, most likely they will feel that it is the same or a different foot due to the foot’s behavior. But a validated questionnaire should be robust enough to be able to reproduce reliably.

        Have you thought about alignment and how the mechanical performance characteristics of the feet you are interested in may influence your study? Here are some interesting refs that might be of assistance to you:

        Torburn L, Perry J, Ayyappa E, Shanfield SL. Below-knee amputee gait with dynamic elastic response prosthetic feet: a pilot study. Journal of Rehabilitation Research and Development 1990; 27, 369-384.

        In contrast to most, these above-stated authors aligned the prosthesis only once and did not realign when changing to different prosthetic test feet. One explanation why this was possible you may find by studying the concept of roll-over shapes. You will find a nice overview of this concept in the reference below:

        Hansen AH, Childress DS. Investigations of roll-over shape: implications for design, alignment, and evaluation of ankle-foot prostheses and orthoses. Disability and Rehabilitation, 2010; 32(26): 2201–2209.

        Good luck with your study!

        Kind regards,
        Margrit Meier

        Comment

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