This design project aimed to create a low-cost spinal orthosis for scoliosis treatment in low-resource settings. The design uses an adjustable two-part plastic shell fastened with screws and a simple hook-and-loop strap mechanism. Validation tests assessed effectiveness, safety, affordability and other requirements. Force and deformation tests on prototypes showed promise while highlighting areas for future work like improved ventilation and fitting adjustability.

1. This project was inspired by and entered in the 2014 LIMBS International
design competition. The purpose of this project is to design a low-cost spinal
orthosis (back brace) for the treatment of scoliosis in low-resource settings.
Therefore, the design problem can be split into two separate categories,
namely scoliosis and low resources.
Scoliosis
• Undesirable spinal bending in the coronal plane
• Develops at the onset of puberty
• Left untreated, can cause:
• Lung and heart damage
• Chronic back pains
• Effects to physical appearance
• Treatment Options available:
• Observation
• Surgery
• Bracing (Spinal Orthosis)
Bracing
• Meant to halt and partially correct spinal bending
• Provides corrective forces upon the ribcage, spine, and trunk
• Gold standard: Boston Brace
Low Resources
• Estimated 29 million people in resource-limited settings in need of orthotics
and prosthetics
• Access to trained professionals is often limited
• Minimal materials and tools for maintenance and manufacturing
• Current orthoses too expensive and require expertise to fit and adjust
VALIDATION
ME 450 TEAM 9
Dan Borgnakke, Dominic Cincione, Marc Hensel, Nicholas Montes
LOW-COST SPINAL ORTHOSIS FOR SCOLIOSISSECTION INSTRUCTOR
Kathleen Sienko
SPONSOR
LIMBS International
DESIGN VALIDATIONPROBLEM
This design is similar to existing spinal orthosis designs, with
crucial differentiating features intended to increase adjustability.
Key design aspects:
• 2-part semi-compliant plastic shell
• UV-fortified polypropylene copolymer
• Adjustable chest and waist circumference
• Fastened with 3 screws on back
• Variable pad placement and spacing
• Simple hook and loop mechanism
• Easy-to-use, durable front straps
MANUFACTURING
Axillary / Thoracic Pads
Front Straps
Pad Straps
Pelvic Pads
Lumbar Pad (inside shell)
Right Shell
Left Shell (transparent)
Velcro Spacer
(inside shell)
Countries with injection molding capabilities have been identified in Africa and
Asia, near resource-limited regions. Suppliers for all hardware parts have also
been identified. A table summarizing the manufacturing cost of this device can be
seen on the right.
Durability Tests
Impact Loading Test/Drop Test
• To validate durability
• 1 impact test at 48.5 kg
• 60 drop tests at brace weight
Static Loading Test
• Load each possible pad location with a 300 N force
Cyclic Loading Validation
• To further validate durability
• Determine deformation caused by walking
• Replicate 51.1 million cycles with an Instron machine
Clinical Trials
• To evaluate effectiveness, clinical trials would need to be performed
• Design would be implemented in adolescents with idiopathic scoliosis
• Successful treatment would be identified as cases where curve is corrected
or stabilized within 5 degrees
Future Work
• Design would need to be taken to and tested in low resource environments
by both the physicians who would fit the brace and the patients
• Tooling designs for injection molding would need to be made
• In jection molded prototypes would need to be validated with the same
standards
PENDING VALIDATION
User Requirement Engineering Specification Spec Target [units]
Effective
Degree of curvature that can be
corrected/stabilized
Between 20⁰ and 45⁰
Percent success in clinical cases
(defined as reducing curve severity
or stabilizing curve within 5⁰)
≥ 75% of cases do not
progress more than 5⁰
Force magnitude applied to
axillary, thoracic, and lumbar
regions of the torso for correction
0 to 65 Newtons
Safe
Coefficient of Friction between skin
contact materials and skin
≤ 0.3
Contact points of pressure greater
than 32 mm Hg (4.3 kPa)
0 points
Maximum deformation by volume
at extreme conditions
≤ 2-5% by volume at
335 K for 2 hours
Minimum radius of any edges
touching the body
≥ 5 mm for corners, ≥ 2
mm for edges
Affordable Total cost ≤ $85
Wearable
Weight ≤ 2.8 kg
Maximum normal distance of brace
outer surface to body surface
≤ 8 cm
Preservance of torso flexion Lateral Flexion ≥ 15°
Quantitative survey data on
comfort
Acceptable on Likert
scale
Adaptable
Cobb angles fit Between 20⁰ and 45⁰
Waist circumference 59 cm to 88 cm
Height 140 cm to 174 cm
Chest Circumference 74.3 cm to 101.5 cm
Number of spinal bends 2 (S shaped curve)
Durable
Drop tests 50 drops from 1.3 m
Survival under impact loading
618 J under IEC 62262
standard
Survival under cyclic loading 51.1 million cycles
Maximum sustained force ≥ 300 Newtons
Easy to fit
Non-included hand tools required ≤ 1 tool
Number of steps ≤ 9 steps
Number of words in instruction
manual
0 words
Time needed to fit device ≤ 4 hours
Easy to don and doff
Number of tools required 0 tools
Number of steps ≤ 9 steps
Number of people other than the
patient required to don/doff the
brace
0 people
Time needed to don/doff device ≤ 5 minutes
Locally Maintainable
Number of consumable parts that
are not supplied or locally available
0 parts
DESIGN CRITIQUE
Injection Mold Shell
Purchase Hardware
Assemble Device
* - Specifications which were validated by design have been left off this list.
Strongly Agree
Agree
Neutral
Disagree
Strongly Disagree
Engineering Specification* Spec Target [units] Result [Status]
Percent success in clinical
cases
≥ 75% of cases do not
progress more than 5⁰
Force application 0 to 65 Newtons 118 N
Thermal deformation
≤ 2-5% by volume at
335 K for 2 hours
0.5% ± 0.2%
Minimum radius
≥ 5 mm for corners, ≥ 2
mm for edges
8 mm, 2mm
Total cost ≤ $85 $68.07
Weight ≤ 2.8 kg 1.31 kg
Maximum distance normal to
body
≤ 8 cm 2 cm ± 2 cm
Preservance of torso flexion Lateral Flexion ≥ 15°
Quantitative survey data on
comfort
Acceptable on Likert
scale
”Agree”
Drop tests 50 drops from 1.3 m
Survival under impact loading
618 J under IEC 62262
standard
Survival under cyclic loading 51.1 million cycles
Maximum sustained force ≥ 300 Newtons
Number of steps to fit ≤ 9 steps 10
Number of steps to don/doff ≤ 9 steps 3
Time needed to don/doff
device
≤ 5 minutes ≤ 1 minute
48.5 kg
1.3m
To assess the feasibility of this design, several validation
tests were performed on the final prototype. Some trivial
tests included measurements of weight, waist and chest
circumference, and maximum normal distance from body
were recorded. Several more complicated validation tests
were also performed, including force application, thermal
deformation, and comfort tests. The results of the completed
tests are presented below.
* - Some specifications are left off of this list. These
specifications are those which were validated by design
selection.
Force Application
• To validate potential effectiveness
• Fitted with force sensitive resistors and worn while forces
at contact points were measured
• Resistors placed in region of lowest perceived pressure
• Scaled up to the size of the pads
Thermal Deformation
• To validate safety and durability
• Rectangular sample of material was measured
• Placed in an oven at 140°F for 2 hours
• Yielded a volumetric deformation of 0.5% ± 0.2%
Comfort Testing
• To validate wearability and comfort
• Ten participants wore brace and completed survey
• Scores recorded with a Likert scale
Width adjustment mechanism shown above in the narrowest straight
configuration (left), and the widest angled configuration (right).
Component Material or Process Cost
Plastic Shell
Polypropylene Copolymer $9.79
Injection Molding $25.05
Force Application
Pads
Closed-Cell Foam $1.12
Straps $0.21
Assembly $1.04
Pad Spacers
Hook and Loop Material $11.50
Assembly $1.34
Hardware
Straps $0.80
Strap Adjusters $1.74
Hooks $7.74
Screws $1.98
Final Assembly Final Assembly $5.76
Total $68.07 FUTURE WORK/VALIDATION
It is recommended the following ideas be explored to improve the design’s
ability to satisfy user requirements:
• Optimize number and placement of ventilation holes to improve safety
• Make non-essential pad areas of brace removable to enhance wearability
• Include a height adjustment mechanism to increase adaptability
• Utilize mechanical advantage strap adjusters for easier donning/doffing
• Add pad spacing mechanism that requires less labor during fitting
Jeffrey Wensman, University of Michigan Orthotics and Prosthetics Center,
Dr. Daniel Johnson, University of Michigan
Acknowledgements