Device for Collecting Stress Images of Subtalar

Joint

Patrick MeltonDaniel Escobar

12/2/10

It is difficult to determine if the subtalar joint is unstable through current methods of examination due to the cost and difficulty of use of the equipment necessary to make reliable measurements.

Producing radiographs to allow for accurate measurements of the subtalar joint for stability analysis has been refined for more practical uses.

Introduction

Create a device that will align the subtalar joint to allow for the best possible radiograph and measurements to determine the stability of the joint.

Purpose

Hindfoot Anatomy

•Cobey view (20°)

•Long axial view (45°)

Various radiograph views

to assess the subtalar joint.

•Telos Device

•“Hinge Device”

•Dynastat

Similar Devices

Literature Review – Radiography

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

• Most reliable and accurate measurements, highest correlation coefficients.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.

Weekly meetings with project advisors discussing literature review, conceptual designs, and future objectives.

Literature Review◦ Subtalar joint anatomy◦ Methods of radiographing the subtalar joint for

best possible measurements.◦ Telos device – same concept but difficult to use.

Current Progress

Considering conceptual designs for stress device

Meeting with Portsmouth Naval Surgeon to discuss potential design ideas

Modeling preliminary designs in Solid Works

Current Progress (cont’d.)

Design Considerations

Price, Mark. (Designer). (2006). Measuring hindfoot with dynastat. [Web]. Retrieved from http://www.gp-training.net/rheum/gait/gait2.jpg

Design allows for inversion of the calcaneus for hindfoot assessment in weight bearing position.

Design Considerations (Ctd)

Brantigan, JW, Pedegana, LR, Lippert, FGInstability of the subtalar joint. Diagnosis by stress tomography in three casesJ Bone Joint Surg Am 1977 59: 321-324

Applies non-weight bearing inversion stress.

Allows for analysis of subtalar tilt angle.

Initial Design

Initial Design (Ctd)

Model the designs in Solid Works and analyze Finite Element model for stresses and factors of safety.

Discuss designs with advisors and make any necessary modifications.

Determine materials needed for constructing device and the cost of the design.

Future Objectives

Schedule