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

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

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

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

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

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

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

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

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

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

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

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

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