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 ID: 582253
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Slide1
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 ClinicSlide2
Problem StatementLack of research in the socket interface between the artificial limb and the residual limb, specifically force profilesMajority of research based on models with historically proven success and qualitative assessmentsSlide3
Current Process for Constructing a Transtibial SocketTranstibial Patient Evaluationa. Limb measurementsb. Skin type and integrity
c. Range of motiond. Hand dexteritye. Fine and gross motor skillsCognitionGel Liner Interface Material SelectionMost common: Urethane, thermoplastic elastomer, silicone
Fit Gel Liner to PatientSlide4
Current Process for Constructing a Transtibial Socket (cont.)Cast and measure over gel linerModify negative modelComputer modelingHand modification
Fabricate positive check socketFit positive check socket – static and dynamic assessmentsFit final laminated socketSlide5
Current Socket DesignsDesigned on a case-by-case basis for individual patientsSlide6
Problems with Current ModelsSkin abrasionPain or discomfortTissue breakdown at the skin surface and within deep tissues
Pressure ulcerations and resultant infections at the socket interfaceMany of these problems arise from stresses at prosthetic interfacesSlide7
Project GoalsAcquire accurate measurements of perpendicular forces acting on the residual limb of transtibial amputee during various movements
Pinpoint regions with highest forcesDesign a socket system in
which
forces
are optimally distributed throughout the
residual limb-socket interface
Increase overall patient comfortSlide8
Forces Acting on the LimbShear– resulting from frictional forces between skin and socketCan be minimized using socket linersPerpendicularSlide9
Method of Force AnalysisForce Sensing Resistor (FSR) placed between liner and socketVery thin– will not cause variation in force determinationDecrease in resistance with increasing force, which leads to increasing output voltageSlide10
Placement of FSRsImpractical to cover every area of the residual limb with sensorsOne FSR used in each area of clinical interest (i.e. areas expected to face larger pressures and cause patient discomfort)
Patellar TendonAnterodistal
Area
Medial Tibia
Lateral Tibia
Popliteal DepressionSlide11
Data AcquisionCircuit design: current to voltage converterSlide12
Circuit Design
Peak force expected to be around 4000 g
feedback resistor selected to be around 500
Ω
to avoid saturation of op-amp
Slide13
Current StatusCompact RIO (analog-to-digital converter) connection with computer set upFSRs connected to measuring circuit1/21/2011 – First trial at The Surgical Clinic with Cody, a transtibial amputee patientTest if circuit reaches saturationCheck sensor sensitivity – changes in resistance that are too rapid with changes in force undesirableSlide14
Design/Safety ConsiderationsWire thicknessThin enough to prevent interference with force dataThick enough to remain durable during movement FSR-wire
connectionCannot break during movementSlide15
Future WorkSuccessful first trial construct more systems for more patients (~10)Rotate FSRs within socket to cover entire area
Test multiple surfaces (incline, flat, stairs)Analyze results, determine regions containing peak forcesUse different types of sockets on Cody
Design and develop
new
socket: provide more
cushioning in
areas of greatest forceSlide16
Determination of SuccessDesign is patient-drivenMeasure forces before and after fitting of new socket and compare valuesSlide17
References