Carbon Fiber Off-Loading Orthosis
Phase: NA
Conditions: Diabetes Mellitus, Peripheral Neuropathy, Orthotic Device
Sponsor: Washington University School of Medicine

 
 
 
Brief Title:  Peak plantar pressures while wearing a carbon fiber off-loading orthoses 
 
Official Grant Title: Carbon Fiber Off-Loading Orthosis 
 
NCT03618628 
 
Date uploaded to clinicaltrials.gov: 2/11/2019 
 
Date the protocol most recently uploaded to human subjects protection review board:  6/28/2018 

Carbon Fiber Off Loading Orthosis 
 
Research Design and Methods 
Model Development: A carbon fiber off-loading ankle foot orthosis will be fabricated for a study team member 
using the geometry consistent with the clinical standard at Orthotic & Prosthetic Design.  The complete carbon 
fiber off loading orthosis (CFO) consisted of the carbon fiber composite (CFC) strut, leather calf support, and a 
leather and foam shoe.  This representative CFO will serve as a baseline from which a finite element (FE) 
model will be built. The model will then be altered as desired to determine the effects of variable design 
characteristics. 
 
First, a computed tomography (CT) scan of the CFO will be completed using a Siemens Biograph 40 scanner 
(0.71 x 0.71 x 0.60 voxel spacing).  Individual structures of the CFO will be segmented and reconstructed in 
3D. The CFC strut geometry and material properties are the greatest determining factors in CFO stiffness and 
mechanical performance and were the basis of the FE model.  From the 3D reconstruction, the strut geometry 
will be traced, extruded, and meshed within Abaqus Explicit FE solver software. Thickness measurements of 
the strut will be confirmed with caliper measurements at various locations along its profile. Ten caliper 
measurements will be taken to verify the width of the strut. These measurements will be averaged and the traced 
profile extruded to the averaged value. Doing will keep the FE mesh consistent with the 3D reconstruction 
geometry but eliminate small geometric artifacts from segmentation of CT images. 
 
The resulting model will be used in the FE analyses to determine deflection and stress responses of the strut 
under varied loads and with varied CFC fabrication techniques (i.e. layups). Material properties for the CFC and 
CFC-to-CFC layer interfaces will be derived from the manufacturer specifications and from prior investigations 
by our group (REF Zou JRRD 2014).  Boundary and loading conditions will be imposed on the model to 
simulate forces applied during a typical gait cycle. Specifically, the top of the strut will be fixed in place and 
experimentally derived force data (from the subject for whom the CFO will be fitted) will be applied as a time-
varying and location-varying vertical force that moved from the heel to the toe in correspondence with the 
subject’s average ground reaction force trajectory during the stance phase of gait. In this way, stress and 
deflection throughout the strut will be measured throughout the entire step, from initial contact to toe off. These 
results will be cross referenced with a simple beam bending equation to confirm accuracy.  Deflection of the 
strut will be measured as an indicator of energy return that can be expected in various CFC layups.  
Model Execution / CFO Design Characteristic Perturbation: Preimpregnated CFC (prepreg CFC) is composed 
of a sheet of single layer carbon fibers embedded in resin. This material comes in two forms; one is 
unidirectional, in which the fibers of a single layer all follow the same direction, while the other is a 2x2 twill, 
in which the fibers are interwoven at 90 degree angles from each other, with half the fibers going in one 
direction and the other half going in the transverse direction. During brace fabrication, layers of CFC are added 
one at a time in varying directions depending on in which direction strength is needed. 
During the course of this award, three CFC layups will be explored.  The different layups were chosen after 
review of manufacturing techniques at Orthotic & Prosthetic Design prior to the award, review of existing 
literature, review of prior modeling results from our group, and through conversations with the CFC 
manufacturer.  The goal of exploring the three layup schemes was to find the layup that 1) maximized 
deflection of the brace (i.e. indirect measure of energy return), while simultaneously 2) minimized stress within 
the brace (i.e. indirect measure of propensity for strut fracture and failure).  The three CFC were each modeled 
with the same geometry (equal length and thickness), boundary conditions, and loading conditions.  
Layup A: Unidirectional fibers, two out of every three layers were oriented along the longitudinal 
direction while the third layer was oriented in the transverse direction. This pattern was repeated 

throughout the layup. The 2x2 twill was used on the very top and bottom layers rotated at a 45 degree 
angle from the principle axis. (Expectation: Greater strength along longitudinal axis with some 
strengthening in the transverse direction) 
Layup B: 2x2 carbon twill without any rotation between layers. Half the fibers were along the principle 
axis and the other half 90 degrees to the principle axis. The cross section of this layup had the same 
strength in the longitudinal direction as it did in the transverse. (Expectation: Strength in both the 
longitudinal and transverse direction) 
Layup C: Unidirectional fibers all in the same direction along the principle axis, meaning all of the fiber 
strength was oriented in the longitudinal direction. (Expectation: Strength along the principal axis only, 
no fibers in the transverse direction). 
 
In order to test the results of the FE model, we will create a new brace for the study team member and we will 
enroll 10 individuals who currently have a Gillette ankle foot orthosis and foot complication related to diabetes. 
Participants will attend an initial study visit when they will sign a consent and have a mold of their foot taken in 
order to design carbon fiber off loading brace.   
 
Participant selection, Inclusion and Exclusion Criteria 
 Inclusion Criteria  
1. Daily life includes a minimum of moderate activity level (variable cadence walking) 
2. Have a Gillette or carbon off loading orthosis as a result of diabetes related foot impairments 
3. Diagnosis of diabetes mellitus and peripheral neuropathy 
4. Ability to ambulate in the community (K-level ≥ 2) 
5. Age > 21 years 
 
Exclusion Criteria (Must be a no)  
1. Unable to ambulate and complete testing required for study participation. 
2. Severe foot deformity of the hindfoot or any deformity of the foot with a dislocation resulting in a bony 
prominence on the plantar/weightbearing surface of the foot. 
3. Neurological diseases that affects walking 
 
Data Acquisition: 
Participants who meet the inclusion/exclusion criteria will be identified by a member of the research team.  A 
member of the research team will contact the participant to assess interest and schedule for testing.  The first 
visit will begin with a member of the research team reading and explaining the informed consent document to 
the participant.  After informed consent is obtained the research team member will create a mold of the 
participant’s foot.  The mold will be used in conjunction with the results from the FE model to create a new 
brace for the participant to be tested at a later date.  The following tests will then be completed during the first 
visit: 
 
1) Collection of medical and personal information: the participants will provide their and their doctor’s 
contact information as well as medication list, a brief medical history, and information about activities 
of daily living. 
2) Movement analysis: Reflective markers will be placed in various locations on the feet, legs, and body so 
we can record movements of the foot and leg while walking.  We will place pressure sensing insoles into 
the participant’s footwear to measure the amount of pressure when performing the activities listed 
during the recording. The participant will be recorded with the device or footwear while performing 
daily activities. The conditions under which they will walk with first will be randomized using a 
computer program which will generate a random order for the conditions.  The recordings will be in a 

format in which any information that identifies the participant is removed. The de-identified recording 
will be stored on a secure server, in a secured area behind locked doors. Only study personnel will have 
access to these computer files.  
3) Questionnaires:  Foot and Ankle Ability Measure and Quebec User Evaluation of Satisfaction with 
Assistive technology 2.0 questionnaire (asks questions about use, comfort, effectiveness, and 
professional services).  The participant is free to skip any questions that they prefer not to answer. 
4) Plantar pressure testing: the participant will be asked to walk across a surface barefoot. This test will 
occur during one of the study visits and will take place at 509 S. Euclid, Suite 216. St. Louis, MO. 
63110 in the Applied Kinesiology Lab.  
5) Neuropathy Assessment: Foot sensation will be measured using a monofilament and a biothesiometer. 
Monofilaments are similar to fishing line of different thicknesses, and will be placed on the bottom of 
the foot to test if the participant feels it touching the skin. A biothesiometer is a vibrating wand that will 
be placed on the bottom of the foot to test if the participant feels it. 
Following the first visit, a new CFO will be fabricated based on the mold and on results from a FE model.  The 
participant will pick up the orthosis at the offices of Orthotic and Prosthetic Design.  The orthosis will be 
examined and modified for comfort.  The participant will then wear the brace from 1 week.  If the brace is 
causing discomfort or pain during this week the participant may return to have it modified.  The participant will 
return to O & P Design after a week.  If necessary, the brace will be adjusted to avoid any rubbing on the foot or 
ankle.  The participant will then continue to wear the orthosis and can return to O & P Design at any time to 
have the brace examined and modified for comfort.  Once the participant has worn the brace for two 
consecutive weeks with no issue, they will return to complete tests 1-5. 
 
Statistical Analyses: 
A repeated measures ANOVA will be used to test for differences of the primary measure of peak plantar 
pressure at the forefoot, midfoot, and heel during walking while the participants are barefoot, wearing the CFO 
consistent with current clinical standards, and wearing the new CFO fabricated based on the results of the FE 
model.  Statistical significance was set at p < 0.05.