1. Fault Tree Analysis Ver. 5
April 21, 2008
Team Members: Adrienne Belasco, Mitch Barnett, Urvi Patel, Dan Wilkinson
Advisors: Richard Debski, PhD, Jan Grudziak, MD, PhD, Prerana Patel, MD
Failure Mode
Implementation Failure
Design Failure E F G H I K L M A B C D

2. A The screw does not improve healing conditions for the patient
preexisting patient condition.

3. B Improper fitting between screw and removal device
Machining Errors in Precision

4. C The screw causes an infection Rejection of the material
Contamination during surgical implantation
Material Biocompatibility
Patient allergy

5. Loosening of scews, decreased stability, and prolonged bone healing
Vibration and shock during bone regeneration period post-removal surgery

6. Screw shaft breaks due to high torques during removal
Bone regeneration results in higher bone-screw adhesion than normal

7. Torque generated by the surgeon is more than 10 Nm
Bone regeneration results in higher bone-screw adhesion than normal F

8. G Possible screw failure during bone regeneration period
Surgeon place the screw at the wrong angle, resulting in added stress G
Bone regeneration results in higher bone-screw adhesion than normal

9. Reduced effectiveness of screw in the alignment of the regenerating bone
Pharmaceuticals may weaken bone

10. Overgrowth of the bone results in inability to use removal device
Natural bone regeneration

11. Screw Stripping K
Bone regeneration results in higher than normal bone-screw adhesion

12. Removal device breaks due to high torques during removal
Bone regeneration results in higher bone-screw adhesion than normal

13. M Screw breakage in vivo
Weakening of screw due to removal of material for second hexagonal socket