1. Mixing and Injection System for Polyurethane Scaffolds Michael Scherer Dustin Dowell Andrew Solomon February 21 th, 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 Water + isocyanate  CO 2 (helps pores form) Polyol + isocyanate  polyurethane

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 ItemCost Dremel$75 (known) Agitator$150 (estimate) Canister$50 (est.) Device Housing$50 (est.) Miscellaneous Fixtures$50 (est.) Polymer components$25 TOTAL:$400 – 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/m ixing%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