Improving Mobility in Peripheral Artery Disease Using an Ankle Foot Orthosis
Condition: Peripheral Artery Disease
MeSH terms: Peripheral Arterial Disease
Study type: Interventional

Summary: 
      This study will determine whether an ankle foot orthosis (AFO) improves walking performance
      in patients with PAD from its first use. Additionally, the study will test walking
      performance after a three month AFO intervention and will examine the feasibility of this AFO
      intervention.

      Data for evaluations will be collected from 50 patients with PAD. Fifty healthy age-matched
      controls will be participate in one baseline gait assessment for comparison purposes. Both
      groups between 40-85 years old.

      Interventions and Evaluations Biomechanics evaluations: Patients with PAD will complete a
      biomechanics evaluation at baseline, following three months of control (standard of care),
      and following three months of AFO intervention. The evaluation will include measurement of
      walking distances, gait function, physical activity, quality of life, energy cost, muscle
      morphometrics, muscle activity, muscle oxygenation, and muscle strength and endurance while
      walking with and without the AFO. Healthy controls will be assessed during one baseline
      collection only and their participation in the study will then be finished.

      Feasibility interview: All patients with PAD will participate in feasibility interviews that
      will assess acceptability, demand, implementation, and practicality. Interviews will occur
      1.5 months and following completion of the AFO intervention (not the control arm).

      AFO and Control (standard of care) Intervention: Patients will wear an off-the-shelf, carbon
      composite AFO that is adjusted to fit for three months. The patients will be asked to wear
      the AFO at all times except when they are in bed or showering/bathing. The instructions given
      to the patients about walking will be to follow the instructions from their doctor regarding
      risk factor management and exercise. The intervention order will be randomized and all
      subjects will participate in both arms.
    

Detailed description: 
      Peripheral artery disease (PAD) is a common cardiovascular disease manifesting from
      atherosclerotic blockages in the arteries of the legs. The most prevalent symptom of PAD is
      intermittent claudication, defined as pain or discomfort in the legs that is produced by
      physical activity and is relieved only through rest. PAD results in significant functional
      limitations such as slower walking velocity and an overall sedentary lifestyle. Prior
      research has documented significant deficits in gait biomechanics; specifically, an inability
      of the ankle plantar flexors to generate normal torque and power. Furthermore, insufficient
      blood flow was not found to be the only mechanism contributing to gait dysfunction in
      patients with PAD, but the affected muscle also demonstrates a myopathy that prevents normal
      leg function in these patients. Thus, treatment must consider muscular function and
      hemodynamics to improve function and increase activity levels. Supervised treadmill walking
      exercise is an effective treatment for increasing the distances patients with PAD can walk.
      However, there is a critical treatment gap for individuals whose disease presentations
      warrant a non--operative treatment plan but lack the motivation, time, access and monetary
      resources for supervised therapy. An ankle--foot orthosis (AFO) to offset ankle plantar
      flexor torque and power deficiency is a novel approach to increase the walking distances and
      physical activity levels in those with PAD. Made of a carbon-- composite material, AFOs are
      adjustable, affordable and could be prescribed and worn long--term to overcome the reduced
      propulsion and improve walking economy. The spring--like properties of carbon--composite AFOs
      allow energy storage at weight acceptance and return at the point of toe off, when the ankle
      plantar flexors are supposed to propel into the next step. Improvements in ankle kinetics and
      angular momentum have been reported by using an AFO with stroke, and other neuromuscular
      disorders affecting the legs. However, AFOs are typically worn for foot drop, and have never
      been implemented in patients with PAD to improve forward propulsion. Pilot work has shown
      that walking with an AFO instantly increases the initial and absolute walking distances in
      patients with PAD as much as pharmacotherapy for six months. An AFO addresses both the
      myopathy and low blood flow problems associated with claudication. Mechanical force from the
      AFO compensates for the insufficient propulsion force of the myopathic gastrocnemius muscles,
      while at the same time decreasing blood flow demand and muscular stress effects of ischemia.
      Thus an AFO allows patients to walk longer without pain or walk the distance needed to
      complete daily activities with less stress to the affected leg, and may preserve/improve the
      overall health of the PAD limb by lowering oxygen demands to PAD muscle and effort induced
      ischemia and stress.

      Hypothesis: An AFO improves walking performance in patients with PAD by reducing the energy
      cost of walking and these improvements can be seen from the first time the patient uses the
      AFO. Further, an AFO intervention improves walking performance by improving the muscular
      function of patients' affected legs.

      Specific Aim 1: Test the hypothesis that from its first use an AFO produces improvements in
      walking performance of patients with PAD by decreasing the required muscle contribution and
      energy cost of walking.

      Specific Aim 2: Test the hypothesis that using an AFO for three months leads to progressive
      improvements in walking performance, physical activity levels and quality of life of patients
      with PAD and that these improvements correlate with improvements in the morphometric
      measurements, oxygenation levels, and muscle strength and endurance characteristics of the
      affected legs. A crossover design will be used, in which half of subjects will complete a
      three--month control period before, and half after, the AFO intervention.

      Specific Aim 3: To determine the feasibility of a three month AFO intervention by examining
      acceptability (satisfaction, intent to continue use), demand (actual use, perceived demand),
      implementation (degree of use, success or failure of use, factors affecting use), and
      practicality (effects, ability of participants to use AFO).

      If the hypothesis is correct, the study will be the first to demonstrate that a simple,
      accessible AFO device can rapidly improve functional status and quality of life in patients
      with PAD immediately by decreasing the required muscular contribution and oxygen demands to
      PAD muscle. Additionally, Aim #2 will evaluate the long--term effects of wearing an AFO on
      functional status and quality of life. Aim #3 will help the investigative team ensure it is
      feasible to implement the AFO in our target population. Detailed measures of mechanisms
      related with walking performance, muscle contribution, physical activity, quality of life and
      how these mechanisms change after wearing the AFO for three months will provide the evidence
      required to implement an AFO therapy that will improve functional status and quality of life
      in individuals with PAD.
    

Intervention name(s): Ankle foot orthosis; Control/standard of care
Intervention type(s): Device; Other
Intervention description(s): Patients will wear an ankle foot orthosis at all times except when he/she is sleeping or bathing for three months.; Patients will carry out with typical activities suggested by their physician for three months.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: ankle foot orthosis; biomechanics; mobility