Effectiveness of Specifically Optimized Off-the-counter Foot Orthosis for the Subtle Cavus Foot
Condition: Subtle Cavus Foot; Mechanical Foot Pains; Plantar Fasciitis; Achilles Tendinopathy; Insertional Achilles Tendinopathy; Strain of Peroneal Tendon; Metatarsalgia; Pes Cavus; Pes Cavus, Bilateral; Pes Cavovarus
MeSH terms: Tendinopathy; Fasciitis; Fasciitis, Plantar; Metatarsalgia; Talipes Cavus; Talipes; Foot Deformities
Study type: Interventional

Summary: 
      As off-the-counter foot orthoses are readily available and have an economic advantage, they
      are increasingly being used by healthcare professionals to treat mechanical foot pains in
      place of custom foot orthosis. However, there is a lack of available evidence to determine if
      a plain off-the-counter foot orthosis that aims to contours to the foot or a specifically
      optimized off-the-counter foot orthosis utilizing the type of orthotic design proposed by
      Abbasian and Pomeroy is more effective in the management of mechanical foot pains in the
      Subtle Cavus foot type.

      This study proposal seeks to fill the gap in this area.

      Primary Aim:

      To investigate the effectiveness of specifically optimized off-the-counter foot orthosis
      designed for the Subtle Cavus foot type in improving patient reported outcomes in patients
      with mechanical foot pains when compared to plain off-the-counter foot orthosis.

      Primary Null Hypothesis:

      There is no difference in pain and functional scores reported by patients between
      specifically optimized off-the-counter foot orthosis and plain off-the-counter foot orthosis
      in patients with mechanical foot pains at four, eight and twelve weeks of intervention.

      In our study, the Subtle Cavus foot refers to the flexible idiopathic forefoot-driven Pes
      Cavus that can be clinically recognised with a positive "Peek a Boo" sign, inverted hindfoot
      position in weight bearing stance and Positive Coleman Block Test as reported by Manoli and
      Graham in 2005.

      Also, for our study, mechanical foot pains are limited to clinically diagnosed Plantar
      Fasciitis, Achilles Tendinopathy, Peroneal Strain or Metatarsalgia:

      Plantar Fasciitis is clinically diagnosed using the following history and physical
      examination findings:

        -  Plantar medial heel pain /or pain along the plantar fascia: most noticeable with initial
           steps after a period of inactivity but also worse following prolonged weight bearing

        -  Heel pain /or pain along the plantar fascia precipitated by a recent increase in
           weightbearing activity

        -  Pain with palpation of the proximal insertion of the plantar fascia /or along the band
           of plantar fascia structure

      Achilles Tendinopathy is clinically diagnosed using the following history and physical
      examination findings:

      Midportion Achilles Tendinopathy:

        -  Self-reported localized pain and perceived stiffness in the Achilles tendon following a
           period of inactivity (eg, sleep, prolonged sitting) lessen with an acute bout of
           activity and may increase after the activity.

        -  Symptoms are frequently accompanied by Achilles tendon tenderness.

        -  Pain located 2 to 6 cm proximal to the Achilles tendon insertion that began gradually
           and pain with palpation of the midportion of the tendon to diagnose midportion Achilles
           tendinopathy

      Insertional Achilles Tendinopathy:

        -  Self-reported pain that is aggravated by activity and stiffness that is associated with
           prolonged periods of rest.

        -  Pain and tenderness with palpation within the distal 2 cm of the Achilles tendon.

        -  Redness and swelling over area of Achilles Tendon insertion over posterior heel

      Peroneal Strain is clinically diagnosed using the following history and physical examination
      findings:

        -  Pain and swelling posterior to the lateral malleolus

        -  Pain with active eversion and dorsiflexion against resistance

        -  May have a history of chronic lateral ankle pain and instability

        -  Pain and tenderness with palpation along the course of the peroneal tendons

      Metatarsalgia is clinically diagnosed using the following history and physical examination
      findings:

        -  Self-reported pain during the propulsive phase of gait. The pain is localized underneath
           the prominent metatarsal heads

        -  The plantar soft tissue can be swollen and inflamed.

        -  Presence of hyperkeratosis over tender areas may be present

        -  Pain and tenderness with palpation of plantar metatarsophalangeal joints

      Secondary Aim:

      To investigate the effectiveness of specifically optimized off-the-counter foot orthosis
      designed for the Subtle Cavus foot type in improving patient reported outcomes in patients
      with mechanical foot pains pre- and post-intervention.

      Secondary Null Hypothesis:

      There is no difference in pain and functional scores reported by patients after introduction
      of specifically optimized off-the counter foot orthosis pre- and post-intervention at initial
      to four, initial to eight and initial to twelve weeks of intervention.
    

Detailed description: 
      Study Design:

      This is a Pilot Randomized Controlled Trial designed to compare the effectiveness of
      specifically optimized off-the-counter foot orthosis versus plain off-the-counter foot
      orthosis in managing mechanical foot pains in the Subtle Cavus foot type. (See Figure 3).

        -  Subjects recruited will be randomly assigned to either the plain off-the-counter foot
           orthosis group (Control Group) or the specifically optimized off-the-counter foot
           orthosis group (Intervention Group) based on a pre-specified randomization list during
           the Screening Visit.

        -  Randomization was performed using the Randomized Permuted Block Randomization method
           with blocks of six.

        -  For participants with bilateral mechanical foot pains, the more symptomatic side will be
           used as the reference for collection of participants reported outcome measures
           throughout the study.

        -  There will be an intervention period of 12 weeks, which is a common therapy window for
           the associated symptoms of mechanical foot pains.

        -  All other standard of care Podiatry management will be implemented for all subjects in
           the two groups throughout the study period.

        -  Standard Podiatry management with stretching exercise regime refers to the following
           protocols with official department stretching and strengthening brochure provided for
           all subjects:

      Towel Stretch (To be introduced at Study Visit 1 (Week 0)):

      Sit down and extend both legs Pass a towel around the top of your foot Slowly pull the towel
      towards your body Hold each stretch for a period of 20 seconds Switch sides and repeat Repeat
      the stretch 10 times on both sides for each set Perform 2 sets a day

      Gastrocnemius Stretch (To be introduced at Study Visit 2 (Week 4)):

      Place both hands on a wall and stand an arm's length away from it Place one foot behind the
      other Bend your front knee Ensure your back knee and back are straight Ensure both heels are
      flat on the floor Do not rotate your hips Ensure both feet are parallel Hold each stretch for
      a period of 20 seconds Switch legs and repeat Repeat the stretch 10 times on both sides for
      each set Perform 2 sets a day

      Soleus Stretch (To be introduced at Study Visit 2 (Week 4)):

      Place both hands on a wall and stand an arm's length away from it Place one foot behind the
      other Bend both knees Keep both heels flat on the floor Ensure your back is straight Do not
      rotate your hips Ensure both feet are parallel Hold each stretch for a period of 20 seconds
      Switch legs and repeat Repeat the stretch 10 times on both sides for each set Perform 2 sets
      a day

      Double Leg Tip Toe (To be introduced at Study Visit 3 (Week 8)):

      With both knees straight, go up on tiptoes on both feet (A) Gently lower both heels to the
      ground (B) Repeat 10 times Perform 2 sets a day

        -  Standard Podiatry management for foot orthosis troubleshooting refers to: Bilateral
           Standard Arch Fill Reduction of foot orthoses if study participant complains of
           discomfort / irritation from use of foot orthosis over the arches of the feet for both
           plain off-the-counter foot orthosis or specifically optimised off-the-counter foot
           orthosis.

        -  Subjects' pain and functional impairment perception will be measured pre- and
           post-intervention at Study Visit 1 (Week 0), Study Visit 2 (Week 4), Study Visit 3 (Week
           8) and the Study Visit 4 (Week 12).

        -  Participants will also be asked regarding compliance towards the use of the foot
           orthosis fitted and other standard podiatry management that has been started and Patient
           Satisfaction Ratings with Podiatry Treatment introduced using a verbal compliance
           ratings form administered by the investigators during Study Visit 2 (Week 4), Study
           Visit 3 (Week 8) and Study Visit 4 (Week 12).

        -  Outcome measures of the specifically optimized off-the-counter foot orthosis group will
           be compared against the plain off-the-counter foot orthosis group to achieve the primary
           aim of the study.

        -  Pre and post intervention within group comparison of outcome measures will be conducted
           for both groups independently to achieve the secondary aim of the study.

      Outcome measures:

      Primary outcome measure:

        -  The Foot Function Index (FFI) total score

        -  The FFI is a self-reported measure of pain, function, and activity level associated with
           foot dysfunction consisting of 23 items divided into 3 sub-scales. The scores range from
           0 to 10, with the higher scores indicating more disability.

        -  The FFI has been validated and is recommended as a reliable measurement scale for use in
           foot orthotic interventions study.

        -  The evaluation of the study device efficacy will be conducted with the main outcome
           measure, the FFI, before and after the intervention.

      Secondary outcome measure:

        -  The FFI sub-scale scores in the domain of pain, disability and activity limitation

        -  The subscales of the FFI will be analysed separately as secondary outcome measures.

      Tertiary outcome measure:

        -  100mm Visual Analogue Scale (VAS) with the end-points "no pain" and "worst pain
           possible"

        -  It is a reliable and valid measure of self-reported pain intensity

        -  VAS is administered before and after intervention to evaluate acute pain levels

      Study Setting:

      Podiatry outpatient clinic at Foot Care and Limb Design Centre, Tan Tock Seng Hospital.

      Study Population:

      Study population will be drawn from the patients referred to Podiatry Department, Foot Care
      and Limb Design Centre, Tan Tock Seng Hospital for Biomechanics Assessment.

        -  Adult patients with clinically diagnosed mechanical foot pains limited to Plantar
           Fasciitis, Achilles Tendinopathy, Peroneal Strain or Metatarsalgia will be eligible.

        -  For participants with bilateral mechanical foot pains, the more symptomatic side will be
           used as the reference for collection of participants reported outcome measures
           throughout the study.

        -  There is no subject restriction based on the race of the subjects.

      Standard Podiatry clinical assessments and a full biomechanical assessment will be performed
      to determine eligibility of potential study participants.

        1. Clinical diagnoses of mechanical foot pains limited to Plantar Fasciitis, Achilles
           Tendinopathy, Peroneal Strain or Metatarsalgia will be done through Physical / Clinical
           assessments.

        2. For participants with bilateral mechanical foot pains, the more symptomatic side will be
           used as the reference for collection of participants reported outcome measures
           throughout the study.

        3. Subtle cavus foot type will be identified through a full biomechanical assessment
           including the "Peek a boo" sign and the Coleman Block Test.

        4. Inclusion and Exclusion criteria will be checked against when the above two conditions
           are met.

      On top of outcome measure questionnaires that will be administered, Study team will retrieve
      data from participant's medical records including basic demographics, standard podiatry
      assessments results and management measures and outcomes as well. These data will be recorded
      into the study database document provided.

      There will not be any incidental findings arising in this research.

      Sample size calculation for comparison between two independent means and paired means:

      Taking a 7-point difference in FFI total score as clinically significant / minimal important
      difference:

        -  Alpha error = 0.05

        -  Power (1-beta error) = 0.80

        -  Two-tailed Test

        -  Difference in mean = 7

        -  Standard Deviation in each group = 7

      Required Sample size is estimated to be at least 16 or more in each group. Hence, target at
      least 20 in each group taking into consideration drop-out and lost to follow-up.

      Taking a 12-point difference in FFI pain sub-scale score as clinically significant / minimal
      important difference:

        -  Alpha error = 0.05

        -  Power (1-beta error) = 0.80

        -  Two-tailed Test

        -  Difference in mean = 12

        -  Standard Deviation in each group = 12

      Required Sample size is estimated to be at least 16 or more in each group. Hence, target at
      least 20 in each group taking into consideration drop-out and lost to follow-up.

      Taking a 7-point difference in FFI disability sub-scale score as clinically significant /
      minimal important difference:

        -  Alpha error = 0.05

        -  Power (1-beta error) = 0.80

        -  Two-tailed Test

        -  Difference in mean = 7

        -  Standard Deviation in each group = 7

      Required Sample size is estimated to be at least 16 or more in each group. Hence, target at
      least 20 in each group taking into consideration drop-out and lost to follow-up.

      Taking a 9mm difference in 100mm VAS pain score as clinically significant / minimal important
      difference:

        -  Alpha error = 0.05

        -  Power (1-beta error) = 0.80

        -  Two-tailed Test

        -  Difference in mean = 9

        -  Standard Deviation in each group = 9

      Required Sample size is estimated to be at least 16 or more in each group. Hence, target at
      least 20 in each group taking into consideration drop-out and lost to follow-up.

      Reference:

        1. R Core Team (2020). R: A language and environment for statistical computing. R
           Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/

        2. Landorf KB, Radford JA (2008): Minimal important difference: values for the foot health
           status questionnaire, foot function index and visual analogue scale. The Foot, 18(1):
           15-19.

      Statistical and Analytical Plans:

      Baseline data such as Age, Gender, Ethnicity, pre-intervention outcome measures and other
      data collected will be explored to determine data distribution and whether data fit a normal
      distribution using the Shapiro-Wilk Test. Other exploration such as Q-Q plot visual
      inspection will be utilised also.

      The Independent Student t-test for comparison between two means for FFI total score, FFI pain
      sub-scale score, FFI disability sub-scale score and VAS pain score between specifically
      optimized off-the-counter foot orthosis and plain off-the-counter foot orthosis at zero,
      four, eight and twelve-weeks post intervention will be utilised.

      Pre- and post-intervention within group comparison will also be analysed using the Paired
      t-test for both the specifically optimized off-the-counter foot orthosis group and the plain
      off-the-counter foot orthosis group at initial to four, initial to eight and initial to
      twelve weeks of intervention.

      Minimal important difference for all outcome measures such as the FFI total score, FFI pain
      sub-scale score, FFI disability sub-scale score and VAS pain score are based on the values
      reported by Landorf and Radford in 2008.

      Statistical significance is defined at the 5% (P = 0.05) level as determined above.

      Non-parametric statistical methods such as the Wilcoxon signed rank test and Wilcoxon rank
      sum test may be applied accordingly if exploratory analysis show that the distribution of
      data collected is skewed.

      Data analysis software that will be applied:

        -  R from R Foundation for Statistical Computing, Vienna, Austria

        -  R Core Team (2020). R: A language and environment for statistical computing. R
           Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/

      Procedures/ activities that are carried out for the purpose of research:

      Screening Visit:

      Potential participants will be assessed by the Principal Investigator or the Co-Investigator
      to identify if they are eligible to participate in the study. If the subject fit the
      inclusion criteria, the on-site investigator will provide an information package, and explain
      and obtain written consent. Subject will be encouraged to ask any questions regarding the
      study.

      If the participant consent to take part in the study, his/her demographics, medical and
      clinical data will be obtained from their medical records at Foot Care and Limb Design Centre
      at Tan Tock Seng Hospital. Participants will be randomly assigned to receive either
      specifically optimized off-the-counter foot orthosis or plain off-the-counter foot orthosis
      based on a pre-specified randomization list upon enrolment into the study. Clinical foot
      orthosis measurement for either a pair of plain off-the-counter foot orthosis or a pair of
      specifically optimized off-the-counter foot orthosis suitable for subject's feet will be
      provided.

      Study Visit 1 (Week 0) Research participants will be fitted with either the specifically
      optimized off-the-counter foot orthosis or plain off-the-counter foot orthosis on Study Visit
      1 (Week 0) as assigned during the Screening Visit.

      Study Visit 1 to 4 (Week 0 to Week 12) Collection of patient reported outcome measures such
      as The Foot Function Index (FFI) total score and its sub-scale scores in the domain of pain,
      disability and activity limitation and the 100mm Visual Analogue Scale (VAS) with the
      end-points "no pain" and "worst pain possible" for the purpose of research will be carried
      out.

      All patient reported outcome measures will be collected at Study visit 1(week 0), Study Visit
      2 (week 4), Study visit 3 (Week 8) and Study Visit 4 (week 12).

      Study Visit 2 to 4 (Week4 to Week 12) Collection of patient reported Verbal Compliance
      Ratings towards the use of the foot orthosis fitted and other standard podiatry management
      using a verbal compliance ratings form administered by the investigators during the study
      visit will be carried out.

      All patient reported Verbal Compliance Ratings will be collected at Study Visit 2 (week 4),
      Study visit 3 (Week 8) and Study Visit 4 (week 12).

      Study Visit 2 to 4 (Week4 to Week 12) Collection of Patient Satisfaction Ratings using a
      verbal compliance ratings form administered by the investigators during the study visit will
      be carried out.

      All Patient Satisfaction Ratings will be collected at Study Visit 2 (week 4), Study visit 3
      (Week 8) and Study Visit 4 (week 12).

      Activities that are performed for routine diagnostic or standard medical treatment as part of
      the research participant's standard care:

      Screening visit Standard Podiatry Biomechanical assessment to determine the participant's
      biomechanics profile is performed as part of standard care. Standard appropriate footwear
      advice (neutral running sport shoes as labelled by the retail manufacturers such as New
      Balance 880, Asics Nimbus, etc.) for the fitting of subject's foot orthosis at the next
      follow-up visit will be provided as part of standard care. Participants will receive standard
      best practice Podiatry treatment for their mechanical foot pains.

      Study Visit 1 (Week 0) The subject will be required to return to Foot Care and Limb Design
      Centre for follow-up consultation with a pair of neutral running sport shoes for fitting of
      either a specifically optimized off-the-counter foot orthosis or plain off-the-counter foot
      orthosis that has been pre-assigned during the screening visit. Standard Podiatry assessment
      and routine management will be provided which includes introduction of clinically indicated
      stretching exercise regime and foot orthosis troubleshooting. Participant will receive
      standard best practice Podiatry treatment for their mechanical foot pains.

      Study Visit 2 (Week 4) The subject will be required to return to Foot Care and Limb Design
      Centre for follow-up consultation with a pair of neutral running sport shoes and foot
      orthosis that has been fitted previously. Standard Podiatry assessment and routine management
      will be provided which includes introduction and review of clinically indicated stretching
      exercise regime and foot orthosis troubleshooting. Participant will receive standard best
      practice Podiatry treatment for their mechanical foot pains.

      Study Visit 3 (Week 8) The subject will be required to return to Foot Care and Limb Design
      Centre for follow-up consultation with a pair of neutral running sport shoes and foot
      orthosis that has been fitted previously. Standard Podiatry assessment and routine management
      will be provided which includes introduction and review of clinically indicated stretching
      exercise regime and foot orthosis troubleshooting. Participant will receive standard best
      practice Podiatry treatment for their mechanical foot pains.

      Study Visit 4 (Week 12) The subject will be required to return to Foot Care and Limb Design
      Centre for follow-up consultation with a pair of neutral running sport shoes and foot
      orthosis that has been fitted previously. Standard Podiatry assessment and routine management
      will be provided which includes introduction and review of clinically indicated stretching
      exercise regime and foot orthosis troubleshooting. Participant will receive standard best
      practice Podiatry treatment for their mechanical foot pains

      Potential Benefits (direct as well as indirect) to research participants and to the society:

      Direct Benefits:

      Study participant may reasonably expect to benefit from the trial's specifically optimized
      off-the-counter foot orthosis or plain off-the-counter foot orthosis in the following way:
      The study device providing optimal biomechanical control leading to reduce stress over
      injured structures of the feet which typically translate to symptoms or pain reduction for
      the user.

      Indirect shorter-term Benefits:

      This study will provide evidence for or against the use of specifically optimized
      off-the-counter foot orthosis in the management of mechanical foot pains in the Subtle Cavus
      foot type. The findings of this study will help to build up knowledge in foot orthotic
      therapy delivery. If specifically optimized off-the-counter foot orthosis is proven more
      effective than plain off-the-counter foot orthosis, this can provide evidence to support the
      use of assessment directed foot orthosis prescription as in the case of utilising the Coleman
      Block Test to differentiate between flexible forefoot-driven Subtle Cavus foot type from a
      hindfoot driven Rigid Pes Cavus foot type compared to a "generic" foot orthosis that simply
      contours to the arch of the foot.

      As the optimisations suggested are specific, this will help practitioners to confidently
      apply wedging techniques and perform standard arch fill reduction that can be consistently
      replicated. Furthermore, incidences of foot orthosis that are optimized wrongly will be
      reduced with standardized optimizations leading to better standard of care.

      Specifically optimized off-the-counter foot orthosis which is "tailored" to the presenting
      Subtle Cavus foot type is cheaper than current custom solutions. If found to be effective
      when compared to a generic plain off-the counter foot orthosis, further research can be
      conducted to determine if a specifically optimized off-the-counter foot orthosis is as
      effective and non-inferior to a custom foot orthosis with the same specifications. As
      optimized off-the-counter foot orthosis can be readily fitted, foot orthotic therapy can be
      instituted without any delay. Improvement in treatment outcomes can be expected as patients
      will receive timely foot orthotic intervention.

      If specifically optimized off-the-counter foot orthosis is as effective and non-inferior to a
      custom foot orthosis with the same specifications. It can provide an easily available,
      cost-effective foot orthosis for patients as custom foot orthosis are at least three times
      the cost of a specifically optimized off-the-counter foot orthosis and require at least two
      weeks for such a custom solution to be made.

      In summary, this project has the potential to make podiatry care delivery for patients with
      painful Subtle Cavus foot type better, safer, faster and cheaper.

      Indirect longer-term benefit:

      Currently, foot orthosis construction for diabetic foot offloading in ulcer prevention is
      also based on the principle of increasing contact area to reduce pressure at a particular
      point. The findings of this study can potentially help to understand how offloading of the
      diabetic foot in ulcer prevention can be relooked for the Subtle Cavus foot type. If
      specifically optimized off-the-counter foot orthosis is proven to be more effective than
      plain off-the-counter foot orthosis in managing mechanical foot pains in the Subtle Cavus
      foot type, this can provide evidence to further investigate if specifically optimised
      off-the-counter foot orthosis can perform better than a device that simply contours to the
      foot in diabetic offloading for ulcer prevention. A cheaper and faster "tailored" solution
      like specifically optimised off-the-counter foot orthosis can benefit patient care in the
      long run in offloading the diabetic foot.

      With emerging technology such as data analytics and machine learning, this project may
      potentially lay the foundation to spur further research in the area of feet type recognition
      for the Subtle Cavus foot type and the Pes Planus foot type using visual analytics
      techniques.

      Safety Monitoring plan, i.e. frequency of review (e.g. daily, weekly, quarterly) and type of
      data (e.g. adverse events/serious adverse events) will be monitored:

      Frequency of review: Monthly at every study visit on Study visit 1, Study visit 2, Study
      visit 3 and the Final Visit.

      Adverse events or Serious adverse events will be monitored

      Assessment plan:

      A standard physical examination of the feet will be conducted at every study visit on Study
      visit 1, Study visit 2, Study visit 3 and the Final Visit.

      Description of anticipated events including character and expected incidence:

        1. Study participant complaining of discomfort / irritation from use of foot orthosis over
           plantar aspect of the feet (both conventional custom foot orthosis or specifically
           optimised off-the-counter foot orthosis) Such incidences can happen and are expected in
           routine and standard foot orthotic therapy in about 30% of users based on PI's clinical
           experience. It is also expected that some people might need longer period of time to get
           used to foot orthotic therapy. Simple trouble shooting of foot orthosis can resolve the
           complaint most of the time.

        2. Study participant complaining of intolerance to foot orthosis use and are not able to
           continue wearing the device even after simple trouble shooting of foot orthosis has been
           provided.

      Such incidence can happen and are expected in routine and standard foot orthotic therapy in
      about less than 5% of users based on PI's clinical experience. Study participant will be
      advised to stop foot orthotic therapy.

      3/4. Rarely, the use of foot orthosis can cause more mechanical pains or create friction
      between the device and the sole of the feet resulting in blister formation. Symptoms of such
      occurrences include: increased pain when using the device but has no issues when not using
      the device, redness over the arch area or blister formation. If participants have any of
      these symptoms, they will be advised to stop the use of the device immediately and to call
      the Podiatrist or principal investigator at once.

      Plan for grading the seriousness of events:

        1. Discomfort / Irritation from foot orthosis use

        2. Intolerance to foot orthosis use

        3. Friction between foot orthosis and plantar sole of foot resulting in rubbing and redness

        4. Friction between foot orthosis and plantar sole of foot resulting in blister formation

      Both 1 and 2 can be considered expected incidences in standard foot orthotic therapy and does
      not amount to an adverse event.

      Both 3 and 4 can be considered adverse events not amounting to serious adverse events.

      Plan for assessing the causal relationship of events to the study:

      For both 1 and 2, standard simple troubleshooting of foot orthosis will be rendered to assess
      for causal relationship. If discomfort / irritation / intolerance is resolved, there is a
      possible causal relationship between events 1 and 2 to the study device being investigated.

      For 3 and 4, study participant will be advised to stop the use of the study device until
      redness or blister has resolved prior to restarting foot orthotic therapy again (with simple
      trouble shooting of foot orthosis rendered). If redness or blister formation is resolved,
      there is a possible causal relationship between events 3 or 4 to the study device being
      investigated.

      Data monitoring will be done in accordance with ICH GCP by the PI on a quarterly basis to
      ensure data integrity is assured.

      Route of dissemination of any data and safety information to the study sites, as well as the
      person/team responsible for doing so:

      PI will conduct monthly face-to-face ad-hoc meetings to discuss and update data and safety
      information with the study team.
    

Intervention name(s): Specifically optimized off-the-counter foot orthosis (Medical grade foot orthosis); Plain off-the-counter foot orthosis (Medical grade foot orthosis)
Intervention type(s): Device; Device
Intervention description(s): The study device is a specifically optimized off-the-counter foot orthosis modified by an additional wedging added onto the original Formthotics (Original Dual Hard) with standard arch fill reduction to achieve a foot orthosis that is "tailored" for the management of mechanical foot pains in the Subtle Cavus foot type. The original Formthotics (Original Dual Hard) is currently in use and is considered a Class A medical device according to the Health Science Authority of Singapore risk classification system. At the moment, the original Formthotics (Original Dual Hard) is also available in the retail market, abeit, without assessment guided optimisations for specific feet types.; The control device for this study would be the plain original Formthotics (Original Dual Hard).
Other intervention name(s): Specifically optimized prefabricated foot orthosis; Specifically optimized prefabricated Insoles; Plain prefabricated foot orthosis; Plain prefabricated Insoles
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: This is a Pilot Randomized Controlled Trial designed to compare the effectiveness of specifically optimized off-the-counter foot orthosis versus plain off-the-counter foot orthosis in managing mechanical foot pains in the Subtle Cavus foot type
Subjects recruited will be randomly assigned to either the plain off-the-counter foot orthosis group (Control Group) or the specifically optimized off-the-counter foot orthosis group (Intervention Group) based on a pre-specified randomization list during the Screening Visit.
Randomization was performed using the Randomized Permuted Block Randomization method with blocks of six.
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Mechanical foot pains; Prefabricated insoles; Off the counter insoles; Optimized insoles