1 Right Angle Screwdriver December 9, 2009 Team: Scott Carpenter - Team Leader Chuck Donaldson - Communicator Nate Retzlaff - BWIG John McGuire - BSAC Client: Ashish Mahajan, MD Resident Plastic and Reconstructive Surgery Advisor: Thomas Yen, Ph.D.2 Abstract In the case of mandible fractures, titanium plates are fastened to the mandible with titanium screws to aid in the healing process. Current procedure requires an external incision on the cheek to gain access to these screws resulting in a scar following operation. A right angle screwdriver could eliminate this need by allowing access to the screws from inside the mouth. However, such a device would need to meet many specifications including size and safety restrictions. Three ideas involving a variety of gears and sprockets were taken into consideration: a worm and wheel gear, right angle gears, and a sprocket and chain design. Through research and an evaluation of the design ideas, a sprocket and chain concept was chosen as a promising solution to this problem. Following the decision of a final design, a final prototype was built to specifications. .3 Table of Contents Abstract ......................................................................................................................................................... 2 Problem Statement ....................................................................................................................................... 4 Background ................................................................................................................................................... 4 Motivation................................................................................................................................................. 4 Current Procedure .................................................................................................................................... 5 Design Constraints ........................................................................................................................................ 5 Current Apparatus ........................................................................................................................................ 6 Design Ideas .................................................................................................................................................. 7 Worm and wheel design ........................................................................................................................... 7 Bevel Gear design ..................................................................................................................................... 9 Sprocket and Chain design ...................................................................................................................... 10 Design Matrix .............................................................................................................................................. 11 Final Prototype ............................................................................................................................................ 14 Actuation ................................................................................................................................................. 14 Fabrication .............................................................................................................................................. 15 Testing Procedure ....................................................................................................................................... 16 Conclusion ................................................................................................................................................... 18 Future Work ............................................................................................................................................ 18 Delivery to Client ..................................................................................................................................... 19 Ethical Considerations ................................................................................................................................. 19 Bibliography ................................................................................................................................................ 21 Product Design Specifications for BME 300 Group 24: Right Angled Screwdriver ..................................... 224 Problem Statement The goal of this project is to design a right angle screwdriver for the reconstruction of the mandible. The right angle screwdriver must be able to fit through a 5 cm incision inside the mouth while providing enough torque to tighten the screws down on to the plate in accordance with standard surgical protocol for safety and sanitation. Background Motivation Facial reconstructive surgeries sometimes include the fastening of plates, normally made from titanium, onto the skull to keep bones correctly placed during the healing process. An incision must be made somewhere on the face, as in all facial reconstructive surgeries, to gain access to the bone in order to attach these plates. Consideration for post-operative scar tissue is taken into consideration and incisions are usually made in places that won’t be aesthetically marring. Unfortunately, not all surgeries can be performed without leaving a visible scar due to the limitations of the instrument used. The implementation of a right angle screwdriver that could fit though an incision of standard size (5 cm) and still effectively seat the screws into the bone would simplify the procedure for the surgeon by allowing better access to the screws. It would also improve the procedure by eliminating the need for another incision and thus not leave any external scarring on the patient’s face.5 Current Procedure Reconstructive surgery of the mandible is a case in which the limitations of the instrument used in attaching the plates leaves a visible scar. The surgeon makes an incision inside the mouth, approximately where the gum and cheek meet, to insert the plates to be attached. A straight screwdriver is used to seat the screws that will fasten the plate to the bone. The only way to gain access to the screws is to make an incision on the exterior cheek. In order to reduce the amount of scar
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