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Mixing and Injection System for Polyurethane Scaffolds

Mixing and Injection System for Polyurethane Scaffolds. Michael Scherer Dustin Dowell Andrew Solomon. February 21 th , 2007. Background. Indications:  Minimally invasive techniques Small bone fractures (i.e. distal radius fracture) Osteoporotic fractures Vertebral compression fractures

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Mixing and Injection System for Polyurethane Scaffolds

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  1. Mixing and Injection System for Polyurethane Scaffolds Michael Scherer Dustin Dowell Andrew Solomon February 21th, 2007

  2. Background • Indications:  Minimally invasive techniques • Small bone fractures (i.e. distal radius fracture) • Osteoporotic fractures • Vertebral compression fractures • Bone cancer repairs (void filler) • Antibiotic delivery • Growth hormone delivery

  3. Current State-of-The-Art • ~1 million hospitalizations due to bone fractures per year in the United States • 700,000 of these per year are treated via autogenous bone graft (within same patient) • Limited donor bone tissue • Increased risk of pain and morbidity at donor site  Demand for synthetic material that is safe and effective

  4. Market Forecast • Capture 10% market share ~70,000 procedures per year • Cost of system (including mixer): $300 • Retail price: $1500 • Total Revenue: $105,000,000 • Total Profit = $84,000,000

  5. Polyurethane Constituents • Isocyanate • Hardener • Polyol • Water • Catalyst • Stabilizer • Pore opener Polyol + isocyanate  polyurethane Water + isocyanate  CO2 (helps pores form)

  6. Desired Foam Properties • 200-600 um pore size • Low PDI – maintain uniform pore sizes • To be validated experimentally • Foam strength

  7. Procedure • In the OR, the polymer is stored as two separate components (isocyanate + hardener) • When needed, both elements will be added to the canister • The canister will then be inserted into the mixing fixture.

  8. Procedure • After mixing is complete, the container is removed from the fixture. (Mixing time estimated 45 sec) • An attachment is then employed to move the mixture into an injection device. • Polymer is injected into the body • 5-10 minute working time depending on composition

  9. Current Budget Estimate • Agitator requires special manufacturing • All estimates are conservative

  10. Outside Advisor – Dr. Frank Papay • Personal practice – craniofacial plastic surgery using PMMA • Volume of injection between 5 and 35cc • Referenced Synthes Norian SRS as comparison

  11. Current Work • Fabrication in process – Rapid Prototype Machine • Immediate obstacles: • Rotary shaft to impeller coupling http://www.postmixing.com/mixing%20forum/images/rt6.jpg

  12. Optimization of Impeller Design • Rushton turbine – radial flow impeller • Important parameters: • D/T ratio = 0.6 (D = impeller diameter; T = tank diameter) • Off-bottom clearance C = variable according to design

  13. Future Work • Experimental testing • What speed to mix (5,000 – 15,000 RPMs) • How much mixing time is needed (30 - 90 s) • Achieve necessary physical properties • Canister fabrication • Develop a system for transferring mixture from canister to syringe • Maintaining sterility throughout process

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