Device for Collecting Stress Images of Subtalar Joint

Final Presentation

Patrick MeltonDaniel Escobar

4/26/11

Hindfoot Anatomy

PurposeCreate a device that will apply stress to the subtalar joint for the best possible radiographic images to allow for accurate measurements and determine the stability of the joint.

Cobey View

Reilingh, M., Beimers, L., Tuijthof, G., Stufkens, S., Maas, M., & van Dijk, C. (2010). Measuring hindfoot alignment radiographically: the long axial view is more reliable than the hindfoot alignment view. Skeletal Radiology, 39(11), 1103-1108.

Long Axial Alignment View

Reilingh, M., Beimers, L., Tuijthof, G., Stufkens, S., Maas, M., & van Dijk, C. (2010). Measuring hindfoot alignment radiographically: the long axial view is more reliable than the hindfoot alignment view. Skeletal Radiology, 39(11), 1103-1108.

Semester Recap•Research Phase•Literature Review•Similar devices•EndNote

•Design Phase•Modeling/Drawings•Size Calculations

•Analysis Phase•Finite Element Analysis•Optimization

Completed Tasks

Final Design 30 degree plate

inclination with additional forefoot plate that rotates 15 degrees.

Sliding heelcup plate for various foot sizes.

Allows for footstraps to be placed in multiple areas.

Final Design

Utilizes two bolts that act as columns to angulate the foot for optimal positioning of the subtalar joint.

Dimensions - Bolts

Ø 1.125” UNF – 12 Hex Head bolt

15°

Ø 0.5” UNF – 20 Hex Head bolt

Dimensions - Hinges

Shoulder screw - Ø ½”,3/8”–16 thread with matching nut.

Shoulder screw – Ø ¼”#10–24 thread with matching nut.

Hinge: Ø 1.0” OuterØ 0.5” Inner

Hinge: Ø 0.5” OuterØ 0.25” Inner

Finite Element Analysis – Foot Plate

Max Displacement: .0618 in.

Finite Element Analysis – Foot Plate

Max Stress: 2550 psi Safety Factor: 3.92

Finite Element Analysis – Base Plate

Max Displacement: .0362 in.

Finite Element Analysis – Base Plate

Max Stress: 1180 psi

Safety Factor: n = 8.47

Finite Element Analysis – Forefoot Plate

Max Displacement: .0273 in.

Finite Element Analysis – Forefoot Plate

Max Stress: 8970 psi

Safety Factor: n = 1.12

Materials SelectionMost of the device will be

made from a radiolucent plastic called Delrin, manufactured by DuPont.Tensile strength – 400 ksiYield Strength – 10 ksiDensity – 1.42 g/cm3

Footstraps made from Nylon

Foam padding (Lux-R-Foam) on sliding plate, forefoot plate, and in heelcup.

CostMaterials Dimensions Cost

Delrin Sheets (4) 12" x 24" x 1" $159 ea.

Delrin Rods 1 ¼" D $7.50/ft.

½" D $1.56/ft.*

¼" D $0.52/ft.**

Lux-R Foam Padding 82" x 36" x ¼" $5.99

Velcro Straps (4) 1" W x 8" L $3.47/ft.

Total Material Cost $675

Shipping $50

Labor Hourly Rate Total Labor

Design $30 60 hrs

Machinist $25 16 hrs

Total Labor Cost $2200

Grand Total $2925

Questions?