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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.
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Analyzing the forces within unilateral transtibialprosthetic 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 Socket • Transtibial Patient Evaluation a. Limb measurements b. Skin type and integrity c. Range of motion d. Hand dexterity e. Fine and gross motor skills • Cognition • Gel Liner Interface Material Selection • Most common: Urethane, thermoplastic elastomer, silicone • Fit Gel Liner to Patient
Current Process for Constructing a Transtibial Socket (cont.) • Cast and measure over gel liner • Modify negative model • Computer modeling • Hand modification • Fabricate positive check socket • Fit positive check socket – static and dynamic assessments • 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 Vout=Vref*(-RG/RFSR)
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 Sensitive • Distal end of tibia • Distal end of fibula • Fibular head • Anteromedial tibia • Hamstring tendons • Pressure Tolerant • Patellar tendon • Medial tibial flare • Mid shaft of fibula • Medial tibial shaft
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
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