Hydrogel Composites for Spinal Disc Replacement

Who Cares?A 2002 National Health Survey reported that 34 million Americans over 18 have lower back pain.

80% of people will have some form of back pain in their lives, many of them with extruded discs.

People with lower back pain are often less productive and have large medical expenses.

Disc or nucleus pulposus replacement attempts to remove debilitating pain and restore functionality.

Current “Solutions”

Composite Perspective

Lumbar Decompression

Laminectomy – Relieves pressure on nerve rootDiscectomy – Removal of the nucleus pulposus to relieve pressure on spinal chord

Lumbar Spinal Fusion Immobilization of spinal bones via screws to reduce movement related painThis can hasten the degeneration of adjacent intevertebral discs and reduce daily mobility

http://brispine.com.au/images/ posterior_fusion_x_ray.jpg

Replaces only the central cushion and restores disc heightHowever, this requires a fully functional annulus fibrosus

http://www.discdyn.com/procedure.html

Nucleus Pulposus Replacement

The Problem

Total Disc Replacement

An invasive surgery that eliminates all damaged disc tissueIt restores function, but without properly imitating the actual function

http://www.usc.edu/schools/medicine/departments/neurological_surgery/clinical/spina/artdisc.html

ObjectiveTo evaluate the effects of micro-crystalline cellulose filler in a hydrogel matrix as a potentially injectable nucleus pulposus replacement.

http://catalog.nucleusinc.com/imagescooked/9122W.jpg

Properties AnalysisMechanical Testing

Rheological Testing

AcknowledgementsA Special Thanks to:

Dr. Skip Rochefort Melissa Taylor Dr. Phil Harding William BeattieDr. Brian Bay Valerie CannonDr. John Simonson Janey-Rae Collins

www.pivotalwellness.com

The spine allows for a highly utilized and diverse range of movements.

A spinal disc has two essential parts: the annulus fibrosus, which acts as a container for the inner cushion, the nucleus pulposus.

Disc herniation is when the annulus fibrosus ruptures and the nucleus pulposus extrudes out.

Annulus Fibrosus

Nucleus Pulposus

www.porcpotlas.hu/en/porckorongserv

Herniation can be caused by a single intense strain/injury or a minor strain/twisting movement if the disc has degenerated over time.

China Lim, Paul Cary and Greg NewbloomChemical, Biological and Environmental Engineering, Oregon State University

The study of the flow of matter

G’ = Storage (Elastic) Modulus G’’ = Loss (Viscous) Modulus

Parallel Plate Geometry with “non-slip” surface

/

/ o

F AK

h h

Compression Modulus, K

where F = applied force A = initial cross-sectional area ∆h = change in height ho = initial height

Initial Peak: Breaking Point

At Rest Breathing Walking Driving

BIO-BASED NANOCOMPOSITES: CHALLENGES AND OPPORTUNITIES - John Simonsen , OSU Wood Science and Engineering

Agarose Micro-crystalline Cellulose (MCC)

A polymer extracted from red algaeForms a gel network in water when heated and then cooledIs inexpensive and biocompatible

Structural component in the cell wall of green plantsIs non-soluble in water and highly hydrophilic

Synthesis Procedure Methods

Agarose is dissolved in water.

Microcrystalline cellulose is added and sonicated to disrupt aggregates.

The mixture is heated by microwave, and quickly poured into chilled molds to prevent filler settling.

http://biology.clc.uc.edu/

http://www.pontinaelettronica.com/

The compressive and rheological properties of a native disc may be achieved by varying the matrix and filler to water ratios.

The MCC has a tensile strength of 7.5 GPa and was used to increase the “toughness” of the gel.

1% Agarose-gel composites were created in 0.00, 0.04, 0.08, and 0.30 ratios of microcrystalline cellulose to water.

Trends were analyzed to predict the effect of cellulose filler on gel strength.