An Injectable Hydrogel for Nucleus Pulposis Augmentation by gdf57j


									           An Injectable Hydrogel for Nucleus
                Pulposus Augmentation

                   Cambridge Polymer Group, Inc.
                   52-R Roland St., Boston, MA 02129
3/5/2004           (617) 629-4400
Anatomy of the Spine
•   Composite Structure
     –     Bony vertebral bodies

     –     Intervertebral Disc

•   Intervertebral disc (IVD)
     –     Outer multilayer fiber structure (annulus
           fibrosus, AF)

     –     Jelly-like inner core, 80% water (nucleus
           pulposus, NP)

•   Notes
     –     Nutrient flow out of vascularized vertebrae is
           through faceplates
             •   Diffuses through NP

     –     Annulus Fibrosis is innervated on outside
           layers only

3/5/2004                                                         AF
•     Lower back pain
       – Herniations
       – Degenerated discs/Trauma
               • Loss of disc height
               • Tears in annulus fibrosus
•     Treatments
       – Discectomies: most common surgical procedures
         for treating intervertebral disc herniation
       – Fusion
       – Disc replacement
•     Loss of nucleus pulposus decreases disc
      height, observed in 98% of discectomy patients
       –   Increases load on facet joints
       –   Deterioration of facet cartilage
       –   Bulging of annulus fibrosus
       –   All result in pain

Disc Repair

•   Restoration of disc height and
    distribution of load across
    vertebral surfaces and annulus
•   Two approaches to disc repair:
    – Total disc replacement
    – Nucleus pulposus augmentation

Nucleus Augmentation: In Situ vs. External

•   Minimizes damage to annulus fibrosus (AF)
     – Better load transfer of NP to AF
           • “flat tire”
•   Better load distribution
     – NP conforms to vertebral surfaces in joint
       space, avoid point or line contact loads
           • mimics behavior of natural NP
•   Less chance of expulsion
     – Better lock-and-key approach
           • Fully fills old NP void
•   Minimally invasive surgery
     – Early therapy, which can be easily revised
       with fusion or total IVD replacement         Line contacts

Invention Summary

•   CPG has developed a technique to
    control the gelation kinetics of vinyl
    polymers, allowing injection of a pre-gel
    mixture into a joint space, followed by in
    situ gelation, forming a load-bearing

•   The parameter space allows a range of
    hydrogels with tunable mechanical
    properties and gelation times

Basics of Invention

 •   The rate of gelation of aqueous vinyl polymers is controlled
     with a second gelling agent (gellant)
 •   Yields a gelling polymer with a finite working time
       – Remains in a viscoelastic state for minutes to hours
       – Injected, molded, extruded, calendered, etc.
 •   The material starts as a two-part mixture
       – Mixed in a mixer, then injected
       – Mixed with a two barrel syringe during injection
 •   Patent pending

Basics of Invention (continued)
•   Gelation occurs over a controlled
    time scale
     – 5 minutes to several hours
•   Actively working with a range of
     – Can control
           • Gelation time
           • Pore structure
           • Mechanical properties
•   Emphasis on biocompatible
     – No polymerization occurs
•   No toxic residues will be released

Advantages of Technology

•   In Situ fabrication of implants
•   FDA clearance likely
     – All materials are biocompatible
     – No by-products produced in hydrogel formation
•   Tunable range of mechanical properties
•   Tunable range of gelation times
•   Closure plug at joint injection site can be created by
    contacting injected pre-gel mixture with high concentration

For More Information


                  Cambridge Polymer Group, Inc.
                  52-R Roland St.
                  Boston, MA 02129
                  (617) 629-4400


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