Reliability of Force Measurement Within the Carbon Fiber Orthosis Proximal Cuff

Ankle foot orthoses (AFOs) are medical devices often used to support the foot and ankle during daily activities. Carbon fiber custom dynamic orthoses (CDOs), one subset of AFOs, that consist of a proximal cuff that wraps around the leg just below the knee, a posterior carbon fiber strut that runs the length of the leg and bends to store and return energy during gait, a semi-rigid carbon fiber footplate that acts as a lever arm to bend the posterior strut, and in some cases a foam heel wedge placed between the footplate and the shoe. Different CDO design characteristics, such as posterior strut stiffness, device alignment, and heel cushion height and stiffness have been studied in the past. While different design characteristics have been studied previously, there is little information available concerning the proximal cuff and how it impacts patient outcomes. Different types of AFOs and CDOs have been used in an effort to offload the limb for years. Both CDOs and patellar tendon bearing (PTB) style AFOs have been shown to reduce forces acting on the plantar surface of the foot. While multiple studies have indicated the importance of fastening the proximal cuff, few have actually investigated the forces acting within the proximal cuff. A loose proximal cuff has been associated with pistoning of the limb, where the limb translates down within the proximal cuff during loading, potentially increasing forces acting on the foot and reducing the offloading effects of the orthosis. Only one study investigated the effects of altering forces within the proximal cuff by adding more padding to the proximal cuff, which was shown to improve limb offloading.

A better understanding of the forces acting within the proximal cuff, and how these effect patient outcomes would help to guide future AFO related research studies, provision, and patient education. At this point in time there is little guidance available to inform patients how tightly they need to secure the proximal cuff when wearing an AFO, many clinicians recommend tightening it so that it's secure, but not uncomfortable. The ability to measure forces within the proximal cuff and an idea of the range of forces seen in a clinical setting will act as a first step to better understanding how forces acting within the proximal cuff impact patient outcomes.

Group 1 - Able Bodied Participants

Inclusion criteria

• Between the ages of 18 and 65
• Healthy without current complaint of lower extremity pain, spine pain, open wounds or active infections, or medical or neuromusculoskeletal disorders that have limited their participation in work or exercise in the last 6 months
• Able to hop without pain
• Able to perform a full squat without pain
• Ability to read and write in English and provide written informed consent
• Ability to fit in a generic sized CDO

Exclusion criteria

• Diagnosed with a moderate or severe brain injury
• Lower extremity injury resulting in surgery or limiting function for greater than 6 weeks
• Injuries that would limit performance in this study
• Diagnosed with a physical or psychological condition that would preclude functional testing (e.g. cardiac condition, clotting disorder, pulmonary condition)
• Visual or hearing impairments that limit walking ability or limit the ability to comply with instructions given during testing
• Require use of an assistive device
• Unhealed wounds (cuts/abrasions) that would prevent AFO use
• BMI > 40
• Pregnancy

Group 2 - AFO Users without Peripheral Neuropathy

Inclusion criteria

• Between the ages of 18 and 90
• Use an AFO(s) for daily activities
• The AFO(s) proximal cuff is compatible with loadpad sensors
• Have used their AFO(s) for a minimum of 2 weeks
• Ability to walk 50 feet without use of an assistive device (e.g. cane, crutch, etc.)
• Ability to read and write in English and provide written informed consent

Exclusion criteria

• Diagnosis or indication of peripheral neuropathy determined using Semmes Weinstein Filaments
• Medical or psychological condition that would preclude functional testing (ex. Moderate or severe brain injury, stroke, heart disease)
• Requirement of a knee stabilizing device (e.g. KAFO, KO) to preform daily activities
• Visual or hearing impairments that limit walking ability or limit the ability to comply with instructions given during testing
• BMI > 40
• Pregnancy

Group 3 - AFO Users with Peripheral Neuropathy

Inclusion criteria

• Between the ages of 18 and 90
• Use an AFO(s) for daily activities
• The AFO(s) proximal cuff is compatible with loadpad sensors
• Have used their AFO(s) for a minimum of 2 weeks
• Ability to walk 50 feet without use of an assistive device (e.g. cane, crutch, etc.)
• Diagnosis or indication of peripheral neuropathy determined using Semmes Weinstein Filaments
• Ability to read and write in English and provide written informed consent

Exclusion criteria

• Medical or psychological condition that would preclude functional testing (ex. Moderate or severe brain injury, stroke, heart disease)
• Requirement of a knee stabilizing device (e.g. KAFO, KO) to preform daily activities
• Visual or hearing impairments that limit walking ability or limit the ability to comply with instructions given during testing
• BMI > 40
• Pregnancy