christine bronikowski, amanda chen, jared mulford, amy ostrowski
DESCRIPTION
Analyzing the forces within unilateral transtibial prosthetic sockets and design of an improved force minimizing socket. Christine Bronikowski, Amanda Chen, Jared Mulford, Amy Ostrowski. Advisor: Aaron Fitzsimmons, The Surgical Clinic. Problem Statement. - PowerPoint PPT PresentationTRANSCRIPT
Analyzing the forces within unilateral transtibial prosthetic sockets and design of an improved force minimizing socket
Christine Bronikowski, Amanda Chen, Jared Mulford, Amy Ostrowski
Advisor: Aaron Fitzsimmons, The Surgical Clinic
Problem Statement
•Lack of research in the socket interface between the artificial limb and the residual limb, specifically force profiles▫Majority of research based on models with historically
proven success and qualitative assessments
Current Process for Constructing a Transtibial Socket1. Transtibial Patient Evaluation
a. Limb measurementsb. Skin type and integrityc. Range of motiond. Hand dexteritye. Fine and gross motor skillsf. Cognition
2. Gel Liner Interface Material Selectiona. Most common: Urethane, thermoplastic
elastomer, silicone3. Fit Gel Liner to Patient
Current Process for Constructing a Transtibial Socket (cont.)4. Cast and measure over gel liner5. Modify negative model
a. Computer modelingb. Hand modification
6. Fabricate positive check socket7. Fit positive check socket – static and dynamic
assessments8. Fit final laminated socket
Current Socket Designs
Designed on a case-by-case basis for individual patients
Problems with Current Models▫ Skin abrasion▫ Pain or discomfort▫ Tissue breakdown at the skin surface and
within deep tissues▫ Pressure ulcerations and resultant infections
at the socket interface
Many of these problems arise from forces at prosthetic interfaces
Project Goals
•Acquire accurate measurements of perpendicular forces acting on the residual limb of transtibial amputee during various movements
•Pinpoint regions with highest forces•Design a socket system in which forces are optimally
distributed throughout the residual limb-socket interface
• Increase overall patient comfort
Forces Acting on the Limb
•Shear– resulting from frictional forces between skin and socket▫Can be
minimized using socket liners
•Perpendicular
Method of Force Analysis• Force Sensing Resistor (FSR) placed between liner and
socket• Very thin– will not cause variation in force determination• Decrease in resistance with increasing force, which leads
to increasing output voltage
Circuit Design
Circuit design: current to voltage converter
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Vout=Vref*(-RG/RFSR)
Circuit Design
Placement of FSRs
•Impractical to cover every area of the residual limb with sensors
•One FSR used in each area of clinical interest, 9 total
Pressure Tolerant
• Patellar tendon
• Medial tibial flare
• Mid shaft of fibula
• Medial tibial shaft
Pressure Sensitive
• Distal end of tibia
• Distal end of fibula
• Fibular head
• Anteromedial tibia
• Hamstring tendons
Design/Safety Considerations•Wire thickness
▫Thin enough to prevent interference with force data▫Thick enough to remain durable during movement
•FSR-wire connection▫Must not break during testing
•Transportability▫Must move from treadmill to ramp area quickly
•Power Supply
Preliminary Trial at The Surgical Clinic
Recent Work• Alterations based on the
preliminary test▫ FSRs reinforced with
nonconductive epoxy▫ Circuit rebuilt▫ Transportable
Encasement
• Prosthetic leg testing
• Voltage calibration
• Drift correction
• NI LabVIEW / RIO
Current Status•Preparing to test with Cody on Friday,
Feb. 11th•Developing LabVIEW module to record
data•Attempting to get in contact with Dr.
Robinson•Calibrating Voltage – Force curve
Future Work
• Conduct trials with additional patients▫ Test on multiple surfaces (incline, flat, stairs)
• Analyze results, determine regions containing peak forces
• Test several different types of sockets with Cody
• Design and develop new socket: provide more cushioning in areas of greatest force
• Determine success from patient feedback and peak force reduction in critical regions
ReferencesEngsberg, J.R., Springer, M.J.N., and J.A. Harder. (1992). Quantifying interface
pressures in below-knee-amputee sockets. J Assoc Child Prosthet Orthot Clin 27(3), 81-88.
Houston, V. L., Mason, C.P., LaBlanc, K.P., Beattie, A.C., Garbarini, M.A., and E.J.
Lorenze. Prelimary results with the DVA-Tekscan BK prosthetics socket: residual limb stress measurement system. In: Proceedings fo the 20th Annual Meeting American Academy of Orthotist and Prosthetist, Nashville TN. P 8-9
Jendrzejczyk, D. J. (1985). Flexible Socket Systems. Clin. Prosthet. Orthot. 9 (4), 27-31. Lee, W.C., and M. Zhang. Using computational simulation to aid in the prediction of
socket fit: a preliminary study. Med Eng Phys. 2007 Oct;29(8):923-9. Polliack, A.A., Sieh, R.C., Craig, D.D., Landsberger, S., Mcneil, D.R., and E. Ayyappa.
Scientific validation of two commercial pressure sensor systems for prosthetic socket fit. Prosthetics and Orthotics International, 2000, 24, 63-73.
Sanders, J.E., Daly, C.H., and E.M. Burgess (1993). Clinical measurement of normal
shear stresses on a transtibial stump: Characteristics of wave-form shapes during walking. Prosthet Orthot Int 17, 38-48.