Reliability of Force Measurement Within the Carbon Fiber Orthosis Proximal Cuff

Overview

The primary purpose of this research study is to determine if forces within carbon fiber custom dynamic orthoses (CDOs) can be reliability assessed using Loadpad and Loadsol force measuring sensors (Novel GMBH, St. Paul, MN). An improved understanding of the forces acting within orthoses may help to guide future orthosis related research studies, provision methods, and patient education. Study participants will consist of three groups; 1) healthy, able-bodied adult participants using generic sized CDOs, which 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, and a semi-rigid footplate that acts as a lever arm to bend the posterior strut, 2) individuals without peripheral neuropathy who use AFO(s) regularly, and 3) individuals with peripheral neuropathy who use AFO(s) regularly. . Group 1 participants will be asked to fasten the proximal cuff to a self-selected cuff tightness 'SSCT', as well as three different predefined force levels; 'Loose' where the proximal cuff is loosely fastened around the participants leg, 'Moderate' where the proximal cuff is fastened with moderate tightness, and 'Tight' where the proximal cuff is tightly fastened around the participants leg. Testing in the predetermined force levels (Loose, Moderate, Tight) will occur in a randomized order. Group 2 and Group 3 participants will be asked to fasten their AFO(s) to a self-selected 'SSCT' tightness. For all groups, forces acting on the leg, within the proximal cuff, will be measured using wireless Loadpad sensors and forces acting on the foot will be measured using wireless Loadsol insoles. Testing will include collection of force data as participants sit quietly, stand quietly, and walk and completion of questionnaires.

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.