Evaluation of Foot Mechanical Information on Static Task and Locomotion
Condition: Postural Balance
Study type: Interventional

Summary: 
      Sensory foot integration is evaluated by foam under feet both in research and clinical
      contexts. However, there is no norm defined regarding foam characteristics and this
      evaluation is mostly performed using a static task. Our goal is to better understand the
      impact of the modification of plantar information by foam both during static task and
      locomotion task. The purpose is to standardize evaluation methods and define reference values
      for a better follow-up and diagnosis of patients.
    

Detailed description: 
      The foot is a fundamental area of interaction with the environment. To understand and
      quantify the importance of plantar information for balance control, researchers characterized
      plantar sensors and evaluated the motor adaptations induced by disrupting the sensory
      feedback of this information via different techniques: electrostimulation, vibration,
      anesthesia, mechanical stimulation (Bent, 2015). Mechanical stimulation is non-invasive and
      uses material of different characteristics. In most cases, it is a foam plate or an
      orthopedic insole (composed of predefined reliefs).

      In clinical practice, the foam is used to assess the foot ability to adapt to the correction
      of the orthopedic insoles. A patient stands still on a force plate which records Center of
      Pressure (CoP) position. The CoP oscillations with and without the foam are compared using
      the Plantar Quotient (PQ). PQ is the ratio between the oscillation surface of the CoP on the
      foam and the oscillation surface of the CoP without foam. A podal postural inefficiency is
      then defined by a PQ >100% meaning that their balance is improved with the interposition of a
      foam. However, there is no consensual characteristics about the height or the density of the
      foam.

      In addition, postural evaluation with mechanical stimulation was previously done exclusively
      in this static mode, which does not represent an ecological reality of daily life activities.
      The effect of thin orthopedic elements has never been quantified during a locomotor task.

      In this context, our project has two objectives, that will be addressed through two
      experimental studies. The first objective is to relate the effect of foam characteristics and
      postural stability. Understanding the standard postural response will allow to identify
      patients with a podal postural inefficiency. The second objective is to evaluate the effect
      of a sole element on the statics and locomotion of healthy participants compared to
      ineffective podal postural participants (determined via the calculation of the PQ detailed
      previously with the foams analyzed in the first study).

      We will perform clinical tests carried out in a daily podiatry practice adding motion capture
      to consider dynamic situations more precisely. The study is interventional (non-invasive) and
      non-permanent due to the interposition of thin foam plate (less than 1 cm thick) and sole
      elements (3 mm thick) under the feet.

      For each experiment, the participants will receive an information leaflet to be read several
      days before coming to the experiment. When they arrive at the experimentation site (IFPEK
      podiatry clinic or M2S research laboratory), each participant will sign a consent form to
      participate to the study after having had the opportunity to ask all the questions to the
      experimenter.

      During the first experimentation (Pimouss 1), the identity of each participant and their
      contact information will be recorded on a dedicated computer and a participant code will be
      assigned to them as part of a pseudo-anonymization procedure. This procedure allows us to
      contact the participants in case of unexpected discovery and for a possible participation in
      the Pimouss 2 study. The correspondence file between the participant's identity and his
      participant code will be saved on a password-protected computer, and this file will itself be
      password-protected for reading and writing.

      PIMOUSS1

      This experiment will be carried out in the IFPEK's care clinic. Before signing the consent
      form, the experimental device (force platform and foam plates) as well as the task to be
      performed will be explained to the participant. The participant will have the opportunity to
      ask all the questions necessary for a good understanding of the study. Once the consent is
      signed, the participant will be able to start the experiment. The participant will perform
      this task under several experimental conditions presented in a randomized order. We will
      focus on the following factors:

        -  Foam: 4 conditions: Depron, Plastazote,Orthomic and the control condition (without foam)

        -  Vision: eyes open and eyes closed. A condition will correspond to a combination of the
           different levels of the foam and vision factor. A test will consist of maintaining a
           standing position on a stabilometric platform for 30 seconds in a given condition. Three
           trials will be performed for each condition. Between each trial of 30s, a rest time of
           at least 30s will be imposed.

      During these 30 seconds of rest, the participant will have to self-assess his stability using
      a visual analog scale.

      In addition to recommendations on the use of foams, the results of this study will allow us
      to identify three categories of postural response:

        1. A physiological response that will be determined by the average oscillation on foam of
           the population studied

        2. An unphysiological response that is significantly lower than the low standard of the
           physiological oscillation

        3. An unphysiological response significantly higher than the high norm of the physiological
           oscillation We will then propose to a selection of participants within each of these
           three groups to perform the Pimouss 2 experiment. The selection of the participants will
           be conditioned by their positive response to participate in Pimouss 2 and according to
           their individual result during Pimouss 1. The interest will be to obtain 3 populations
           whose answers are significantly different.

      Only Anne-Hélène Olivier (in charge of data entry and also of the project) will be able to
      contact the selected participants.

      A large number of participants will be necessary to allow the construction of the norm of the
      population oscillation which is unknown (in the foam condition) and thus determine the bounds
      of this parameter. A seminal study on postural control, and particularly on the weight of
      visual information, established norms for this control on a population of 132 participants.
      We therefore refer to this number for our experiment and plan to evaluate the postural
      control response on 132 participants. We will statistically re-evaluate this number with the
      first data.

      The voluntary participant will have no indication on the results of the Pimouss 1 study at
      the time of his inclusion in Pimouss 2.

      PIMOUSS2 The participant will arrive at the M2S Laboratory. His correspondence file will be
      found and will allow to use directly the pseudo-anonymization code created during the first
      experimentation.

      The optoelectronic system (Qualisys A, Sweden) will require the positioning of
      retro-reflective sensors on the anatomical landmarks.

      The participant will then perform the same test as in the first experiment (but on a single
      foam), followed by several recordings with and without insole elements.

      Each condition will be repeated 3 times to limit the bias of variability of the measurement.

      For locomotion, each participant will perform defined trajectories (straight ahead and 90°
      turns) of about 10m distance. He will repeat 5 times per condition (sole elements or not, and
      with eyes closed or open). The participant will perform this task under several experimental
      conditions presented in a randomized order. We will focus on the following factors:

        -  Trajectories: (straight ahead or 90° turns) to allow for representativeness of daily
           walking

        -  Visuals: (eyes closed or eyes open) to isolate the contribution of plantar information
           on this task.

        -  Mechanical stimuli (control condition (without element), sole element under the right
           foot or sole element under the left foot) A condition will correspond to a combination
           of the different levels of the trajectory factor, vision and mechanical stimulation.

      Data Anonymization:

      A pseudo-anonymous identification code is assigned to each participant when he/she is
      received in the laboratory via a computer dedicated exclusively to this purpose. Access to
      the computer is protected by a password. In fact, none of the data used in this research
      contains any identifying information about the participants.

      A pseudo-anonymous identification code is assigned to each participant upon arrival at the
      IFPEK clinic via a computer dedicated exclusively to this purpose.

      Data storage:

      The storage of information on paper is reduced to a minimum, and concerns the experimentation
      notebook and the participation consents.

      The notebook contains the experimental data recorded for each day of testing, the
      experimenters present, the identification code of the participants tested, the nature of the
      tests and any technical or human problems. This notebook is archived in a locked cabinet
      located either in the medical office of the laboratory.

      All other computerized data are stored on the hard disk of the motion analysis system
      computer, access to which is protected by a password. They are then archived after each
      experiment and for each project, in the form of an electronic file saved on a dedicated space
      in the internal Network Attached Storage (NAS) of the M2S laboratory.

      For experiments outside the laboratory (within the IFPEK) the M2S laboratory has created a
      secure Virtual Private Network (VPN) to allow the transfer of data and the equivalence file
      from the experimentation site to its internal NAS.

      Data retention period:

      Experimental notebooks and the participants' consent forms are kept for 15 years.

      Anonymized computerized data are archived after 4 years (duration of the study).

      Data processing and analysis The statistical analysis will consist of a comparison of results
      from dependent groups. The statistics will be inferential. A repeated measures ANOVA followed
      by post-hoc tests will be used to evaluate the effect of the foam on the participants'
      postural response or the effect of the plantar stimulation during the locomotor task. We will
      pay particular attention to the effect size associated with the test.

      The static analysis with the foams will be complemented by equivalence tests with respect to
      the results obtained with Depron. The dependent variables analyzed will be, among others, the
      characteristics of the displacement of the Center of Pressure and the Center of Mass, or the
      plantar pressures.
    

Intervention name(s): Foams; Foam / Orthopedic insole
Intervention type(s): Other; Other
Intervention description(s): Every subject will perform 24 randomized trials on force platform.; 3/5 of the initial population will perform static and locomotion task, with randomized conditions.
Other intervention name(s): plastazote; orthomic; Depron; foam; Insole
Intervention model: Sequential Assignment
Intervention model description: All participants participate to the first experiment. As the outcomes are continuous variables, to be sure to identify a variability between subjects based on their plantar information, we select 3 separated groups (on CoP results) of the initial population.
Based on their results, 3/5 of the initial population can be recruited for the second part of the experiment.
Masking: None (Open Label)
Primary purpose: Other
Keywords: foam; locomotion; postural control; orthopaedic insoles