D.I.S.C.Decompressive Intervertebral Spine Chair Sponsored by Entrepreneur: Sheel Gardner

Advised by Dr. James Iatridis, PhD

The Objective: Proof of Concept

• Find a method and create a non-invasive device that will effectively mitigate low back pain

• Primary Goals:– A) Do No Harm– B) Relieve short-term pain– C) Contribute to long-term health

The Need Immediate : A) Sponsor presented with ruptured disc

Broad Implications: 1) Total direct and indirect costs for treatments

of LBP are estimated to be $100 billion annually in the U.S.1

2) The lifetime prevalence of LBP in the United States is 60-80%2

1 - Bigos SJ, Boyer OR, Braen GR. Acute Low Back Problems in Adults. Clinical Practice Guideline, Quick Reference Guide Number 14. Public Health Agency, Agency for Health Care Policy and Research. Rockville, Md:. Department of Health and Human Services;1994.2 - http://www.ninds.nih.gov/disorders/backpain/detail_backpain.htm

General Approach

• 1) Preliminary Research: anatomy, pathologies, routes to health, working with Cadavers

• 2) Consulting Experts: Orthopaedic Spine Surgeon, Spine Researcher, Physical Therapist, Chiropractors

• 3) Evaluate successful treatments• 4) Existing products and technologies? • 5) Brainstorm, Evaluate, Calculate, Design• 6) Repeat #4-5• 7) Fabricate• 8) Test and Analyze

Understanding the Spine: Basic Anatomy

Healthy Spinal Unit

Side View

http://sobrien2000-ivil.tripod.com/sitebuildercontent/sitebuilderpictures/hs2fig1.gif

Preliminary Research: Spine Pathology

http://emedicine.medscape.com/article/310353-overview

- Because they are avascular, discs rely on pressure gradients to obtain nutrients

- When under compression, a negative pressure gradient cannot be established

Various Pathologies

• Healthy• Small tears in

annulus• Nucleus begins

bulging out annulus, impinging on nerve

• Nucleus escapes via tear or burst through annulus

Why Do Discs Degenerate?

Natural Causes

• Aging – Natural process of

wear and tear over time

• Genetics– Predispositions to

degeneration

Habits• Nutrition

– Vitamins– Fluids

• Lifestyle– Sitting all day– Exercise– Sleep

• Posture– Musculature

Decompress the discAllows diffusion to occurNutrients can replenish the discFacilitates self-repair over timeApproaches the fundamental problem

Intervertebral Decompression (ID)

Challenges Inducing ID

• How to grab vertebrae in a non-invasive way?

• While being comfortable?

• What about muscle resistance (cadaver lab)?

• What already exists?• What target user?• Options: Mechanical

Manipulation, Electrostimulation, Posture Aid

Initial Concept

DISC Solutions

• Work with gravity instead of against it– Lower user instead of

raising them• Comfort provided by

uniquely molded orthotic splint pads

• Seating is a naturally relaxed position, solving the tightening musculature issue

• Many massage chairs exist, but none focus on effective decompression

Demonstration: Final Design Concept

How it WorksWeight compressing discs

Reactant forces from chair

How it Works

Friction

AppliedForce

AppliedForce

Normal Force

After Deflation

Friction and Normal Force Resultant

Weight

Design Evolution

• Decided on an office chair as the platform

– Easier to obtain controlled leverage

– Large market

• This particular chair– Highly adjustable– Modifiable– Solid Steel Frame

Staples® Acadia™ Multi-Function Mesh Task Chair

Design Constraints

• Based on structural anatomy: best contact point was determined

• Contact Area 1.5” governed lead screw choice

• Lead Screw design– Strength was

overdesigned for safety and conformance to contact area

– Negligible deflection

Lumbar Saddles

• Contoured• ThermoPlast• Traction is

obtained at desired location

• Lumbar back support

• Approximately 90 degree coverage, allowing fit for range of users

• Through 5 iterations

• Stiffness design

Saddle Iterations

Connection to Lumbar Saddles

- Steel leveling feet bolted to saddles

- Ball joint to allow degrees of freedom for comfort

- Countersunk bolts into saddle construction

- 5cm into lead screw, other connection

Lead Screw, Frame, Forcepath

- Lead screw connected through threaded bolt support

- Welded to steel base plate

- Bolted to original chair frame

- Transfers force from human through all elements to ground

Seat Cushion Assembly

- Pneumatic cushion- Designed for

immobile users- 3” deflation

capability

- Foam layers for comfort at full deflation

- Supporting wood for enclosed seat cushion assembly

- Connected to Steel base plate

Testing and Analysis

Partial Deflation (5 second intervals)

Load Reduction

(lbs)

Quantitative: Load Reduction on Lumbar Spine

0 1 2 3 4 5 6 7 8 9 10

0

20

40

60

80

100

120

140

160

Testing and Analysis

Partial Deflation (5 second intervals)

Comfort Level

Qualitative: Comfort Levels Throughout Cycle

0 1 2 3 4 5 6 7 8 9 10

0

1

2

3

4

5

6

7

8

9

10

Results

• Average maximum unloading of lumbar spine: 44.7% of body weight

• Average comfort @44.7% unloading : 7.5/10 → MAXIMUM UNLOADING

• Average initial comfort (1-10(good)) : 8.25/10• Average comfort @38.3% unloading : 9.25/10 → OPTIMAL

COMFORT• 5 minute comfort level (@38.3%) : 8.5/10• 10 minute comfort level (@38.3%) : 8/10

Conclusions

- Quantitative– Unloading does take place

• Isolating the lumbar area• Proof of concept successful

- Qualitative– Improved posture

• Muscle training– Higher comfort level needed

• The main deterrent for devices is comfort

Future of DISC

• More comprehensive testing– More diverse subjects– Long term results– Invasive measurement of disc height

• Determine whether customization vs. sizes for saddles

• Refine product now that there is proof that lumbar unloading occurs

Acknowledgments

• Dr. Sharon Henry PhD, Physical Therapy• Dr. Robert Monsey MD, Orthopaedics and

Rehabilitation• Erik Hemmit DC, Chiropractor• Dr. Jean Szilva MD, Gross Anatomy and

Neuroscience• Corey Berman Physical Plant• Dr. Mike Rosen PhD, Engineering• Floyd Vilmont Machine Shop• Dr. James Iatridis PhD, Spine Bionengineering• Sheel Gardner Sponsor, Entrepreneur