Iterative Design of Custom Dynamic Orthoses and Comprehensive Design of Musculoskeletal Model
Phase: NA
Conditions: Adult ALL, Healthy
Sponsor: University of Iowa

 
 
 
 
 
 
 
 
 
Title: PRMRP Norms: Iterative Design of Custom Dynamic Orthoses and Comprehensive Design of 
Musculoskeletal Model. 
NCT Number: NCT04800510 
Date: November 7, 2023 
 
 
 

Study Protocol: 
Purpose and Procedures: 
The purpose of this study is to determine the effect of external bracing, in the form of a carbon fiber dynamic 
orthosis, on joint contact stress, muscle forces, physical function, and gait biomechanics. The effects of external 
bracing on gait mechanics, mobility, and muscle and joint forces are poorly understood. Collected data will 
include patient demographics and anthropometrics, ankle range of motion and stiffness data, plantarflexion 
strength data, CT images, CDO stiffness data, physical performance measures, patient reported outcomes, gait 
kinematics and kinetics, plantar pressures, and electromyography data. The knowledge that will be gained from 
this investigation has the potential to substantially improve the understanding of how external bracing impacts 
limb function and inform future investigations to advance the clinical prescription of ankle foot orthoses. 
Objectives and Specific Aims: 
Specific Aim 1: Determine the effect of CDO design modifications on ankle contact stress in a cohort of healthy 
able-bodied individuals. 
Specific Aim 2: Determine the effect of CDO design modifications on physical function and gait biomechanics 
in a cohort of healthy able-bodied individuals. 
Specific Aim 3: Determine the effect of CDO design modification on muscle forces during gait 
Specific Aim 4: Refine methods of integrating data from multiple sources into musculoskeletal model to 
evaluate ankle contact stress. 
Background and Significance: 
Post-traumatic osteo-arthritis (PTOA) is a significant problem caused by chronic, increased, contact stress and 
fracture severity. Surgical fracture reduction has been the mainstay of intra-articular fracture (IAF) treatment for 
decades, but it is not the only factor influencing joint contact stresses. Furthermore, even with the best surgical 
effort, there often remains residual incongruity that leads to elevated contact stress. Numerous studies have 
explored the relationship between elevated contact stresses and the development of osteoarthritis following 
traumatic injury of the ankle. CDOs, such as the Intrepid Dynamic Exoskeletal Orthosis (IDEO) developed at 
Brooke Army Medical Center, have been used to dramatically improve function and reduce pain in hundreds of 
service members with traumatic limb injury. CDOs are comprised of a proximal cuff sitting just below the knee, 
a posterior strut used to store and return energy, a semi-rigid foot plate, and in some cases a heel cushion 
between the footplate and shoe [11]. These design components can be varied to influence the forces and 
motions experienced by the limb [11-14], which in turn influence the forces on the foot and the activation of 
muscles that cross the ankle [8, 15, 16]. Recent findings indicate that this can decrease load transfer across the 
ankle, which implies that CDOs may be able to be effectively tuned to reduce articular contact stress. A key 
mechanism by which may articular contact stress may be reduced is the reduction of force produced by muscles 
around the ankle. 
The multiple data sources collected in this study will serve as inputs for creating a comprehensive 
musculoskeletal model using OpenSim modeling software. OpenSim is an extensible software package that has 
been developed over decades to combine knowledge of computational modeling and biomechanical system 
simulations in order to calculate muscle forces generated from movement, kinematic adaptations during gait, 
and human-device interactions [78]. The use of OpenSim will allow for accurate simulations of gait, as well as 
calculation and prediction of variables that are difficult to measure experimentally [78]. 
Inclusion/Exclusion Criteria: 
Patient Inclusion Criteria 
- Between the ages of 18 and 50 
- Shoe size between women’s 8 and 13.5 or men’s 6.5 and 12 
- Healthy individuals without a current complaint of lower extremity pain, spine pain, or medical 

or neuromusculoskeletal disorders that have limited participation in work or exercise in the last 
6 months 
- Full active range of motion of the bilateral lower extremities and spine 
- Ability to hop without pain 
- Ability to perform a full squat without pain 
- Ability to read and write in English and provide written informed consent 
Patient Exclusion Criteria 
- Diagnosed moderate or severe brain injury 
- Prior lower extremity injury resulting in surgery or limiting function for greater than 6 weeks 
- Diagnosis of a physical or psychological condition that would preclude testing (e.g. cardiac 
condition, clotting disorder, pulmonary condition) 
- Visual or hearing impairment that would interfere with instructions given during testing 
- Require an assistive device 
- Wounds to the foot or calf that would prevent CDO use 
- BMI greater than 35 
- Pregnancy – Per participant self-report. Due to the expected small number of pregnant 
individuals and resulting inability to account for its effect on resulting outcomes, participants 
will be withdrawn from the study 
Design and Methods: 
Patients will wear generic sized CDOs provided by Bio-Mechanical Composites (Des Moines, IA). 
Personal/demographic and anthropometric information will be used to fully characterize the study participants. 
We will collect multiple variables that have been previously associated with outcomes including race, ethnicity, 
and education. Anthropometric and demographic information such as age, biological sex, study limb (left or 
right), height, weight, leg length, shoe type, shoe length and width will also be used to characterize the cohort. 
Multiple outcomes measures will be used to characterize patient-centric outcomes. 
Physical performance measures provide an objective and responsive assessment of an individual’s functional 
mobility. Activities of daily life require performance of a range of functional tasks that require balance, agility, 
speed, and power. The four square step test (4SST) is a widely used test of functional mobility that requires 
rapid changes in direction that are often problematic following lower limb injury. The measure has good to 
excellent reliability and validity across multiple patient populations and groups and is a key dependent measure 
in most CDO-related studies to date and has demonstrated ability to detect changes in function in individuals 
with limb trauma and CDOs [7, 9, 27, 36].  The sit to stand 5 times (STS5) test is a well-established measure of 
lower limb muscle strength, endurance, and mobility [39]. The STS5 test has excellent reliability and good 
validity across a broad range of patient populations [35, 39-48]. 
Patient-reported outcomes questionnaires will be used to evaluate participant physical function, activity level, 
pain, comfort, satisfaction, and preference in addition to multiple other relevant outcomes. The Orthotics 
Prosthetics Users’ Survey (OPUS) is a leading measure for evaluating satisfaction with orthotic devices and 
services [49]. It is a self-report questionnaire, with the full battery consisting of 88 questions and five modules. 
The satisfaction with devices portion will be used to evaluate device comfort, form, and fit using a four-point 
Likert scale and has good to excellent reliability, internal consistency, and validity for individuals with a wide 
range of diagnoses requiring orthotic and prosthetic services [49]. Comfort and smoothness will also be 
assessed using a modified version of the Socket Comfort Score, a reliable, valid, and sensitive measure of 
device fit and comfort [50]. These measures have been shown to effectively capture patient perception, are 

responsive to simple modifications to CDO device function, and will be applied in a manner consistent with a 
prior publication by the research team [11]. Participants will be asked to report their pain using a standard 11-
point numerical pain rating scale, in which 0 = no pain and 10 = worst pain imaginable, at the start of each 
session, and at multiple points while walking in each condition. Participants will be asked to rate the three 
braces (CDO-A, CDO-B, and CDO-C) on a standard 11-point scale, where 0 = worst imaginable device and 10 
= best imaginable device. The University of California, Los Angeles (UCLA) activity score is a 10-level rating 
scale that is used to both qualitatively and quantitatively define an individual’s current and/or desired level of 
activity and has been shown to be reliable with no floor effects [53]. The Patient Reported Outcomes 
Measurement Information System (PROMIS) is a group of patient-centered tests, developed through funding 
from the National Institutes of Health, which can be used to characterize physical, mental, and social health and 
function. The PROMIS instruments use modern measurement theory to reliably and validly assess patient-
reported outcomes. We will use PROMIS to evaluate physical function. Semi-structured interviews will also be 
used to fully capture the patients’ perspectives, experience, and opinions associated with the device options they 
experienced as part of the study. 
Impairment, biomechanical, and device data will be used to compare devices, characterize limb and device 
function, and to provide insight in a manner not commonly found in comparative studies. Bending stiffness will 
be measured using a custom-made orthotic stiffness testing device designed specifically for quantifying CDO 
bending stiffness in Nm/degree. Ground reaction force and motion capture data will be used to evaluate the 
motion and loading of the lower limb and CDO devices as participants walk on an over ground walkway at self-
selected speed and a controlled speed based on leg length [54, 55]. Muscle activity will be measured using 
DELSYS EMG sensors. EMG data will be collected bilaterally in the lower limbs and data will be analyzed 
over regions throughout the gait cycle. In-shoe plantar pressure distribution will be measured using the LoadSol 
system which interfaces with the foot and shoe insole and has been found to be accurate, precise, and repeatable 
in measuring plantar pressures during normal gait [60, 61]. Ankle range of motion and stiffness will be assessed 
using the Iowa Ankle Range of Motion device. Ankle strength will be assessed using the Standing Heel-Rise 
Test. Subjects will perform as many standing heel-rises as they can, while their ankle motion and body/limb 
alignment are carefully monitored.  
Statistical Analysis Plan: 
Analysis Methods: 
Data quality will be rigorously examined over the course of this study. The distributions of study measures will 
be characterized using descriptive statistics. For descriptive statistics, univariate statistical approaches will 
include careful review of data frequencies, measures of central tendency, and distribution shapes. Additionally, 
identification of out of range data, determination of the quantity of missing data, and accurate description of the 
study population will be achieved. 
Power Analysis: 
The proposed sample size for this study is 10 subjects. Since the primary purpose of this study is to refine 
procedures for inputting multiple data sources into a musculoskeletal model, the study does not call for a total 
number of participants consistent with prior investigations by Dr. Wilken. In a 2017 study conducted by 
Blazkiewicz et al, data was collected from 10 healthy subjects and incorporated into a generic OpenSim 
musculoskeletal model [79]. The results of the study showed some inter-individual variation as expected, but 
identified a common theme of muscle peak force regularities acting on the ankle joint across subjects, indicating 
that a 10 subject sample size is sufficient for the protocol design of similar investigations [79]. 
 
 

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