The Effects of Heel Distraction Height on Foot Loading With Carbon Fiber Custom Dynamic Orthoses

Carbon fiber custom dynamic orthoses (CDOs) have been used to improve function, reduce pain, and offload the foot and ankle for individuals with a number of conditions affecting the lower extremity. CDOs consist of a proximal cuff that wraps around the leg just below the knee, a posterior carbon fiber strut that bends to store and return energy during mid to late stance, a semi-rigid carbon fiber footplate, and, in some cases, a foam heel wedge placed in the shoe. Unloading ankle foot orthoses (AFOs) have also been used for a number of lower extremity conditions, including traumatic injuries, in effort to reduce forces and pressure acting under the foot. Unloading AFOs have been created using many different designs, which include a proximal cuff just below the knee, a rigid strut (made of metal, plastic, etc.), and some sort of foot component (footplate, shoe, etc.).

Both CDOs and unloading AFOs have shown varying levels of success in reducing forces acting on different regions of the bottom of the foot during gait. The differences in loading may be related to a distinct difference between CDOs and unloading AFOs: CDOs do not suspend, or distract, the foot away from the footplate.

The purpose of this study is to determine the effects of CDOs and heel distraction height (the distance between the heel and the footplate) on limb loading and motion as well as patient reported pain and comfort. In this study, forces acting under the foot will be measured using wireless Loadsol insoles (Novel GMBH, St. Paul, MN) as participants walk without an orthosis (NoCDO) and with a CDO with three different posterior strut lengths resulting in three different levels of heel distraction (0cm, 1cm, 2cm) at self-selected and controlled speeds. Additionally, gait kinematic and kinetics will be measured using infrared motion capture cameras (Vicon Motion Systems Ltd., Denver, CO) and force plates (AMTI, Watertown, MA). Participants will be provided a lift for the contralateral limb to reduce the effects of leg length discrepancies during walking. Loadpad force measuring sensors (Novel GMBH, St. Paul, MN) will be used to measure forces within the CDO proximal cuff. After walking in each condition, participants will complete questionnaires concerning pain and orthosis comfort.

Inclusion criteria

• Ages 18-65 years
• Traumatic hindfoot injury (soft tissue injury or fracture affecting the hindfoot or ankle)
• Mechanical pain with limb loading (>=4/10 on Numerical Pain Rating Scale)
• Ability to walk 50 feet at a slow to moderate pace
• Ability to walk without a cane or crutch
• Ability to read and write in English and provide written informed consent

Exclusion criteria

• Diagnosis with a moderate or severe brain injury
• Diagnosis with a physical or psychological condition that would preclude functional testing (e.g., cardiac condition, clotting disorder, pulmonary condition, etc.
• Ankle weakness resulting from spinal cord injury or central nervous system pathology
• Nerve, muscle, bone, or other condition limiting function in the contralateral extremity
• Rheumatoid or inflammatory arthritis
• Necrosis of any bones in the foot or ankle
• Pain of 8/10 or greater during walking
• Uncorrected visual or hearing impairments
• Require use of a knee stabilizing device to perform daily activities (i.e., Knee ankle foot orthosis, knee orthosis, etc.)
• Pregnancy
• Body mass index greater than 40 kg/m2