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SD_Group12_Midterm_Presentation

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SD_Group12_Midterm_Presentation

  1. 1. MINIMIZING STRESS SHIELDING IN FEMORAL HIP IMPLANTS THROUGH MATHEMATICAL MODELING AND EXPERIMENTAL VERIFICATION Justin Fisher, Tyler Grubb, Phuong Huyen, Rohan Yadav Dr. Abdellah Ait Moussa, Dr. Morshed Khandaker
  2. 2. OVERVIEW Objective: • Reduce stress shielding and interface stress in a hip replacement by controlling stem stiffness, which is a function of stem geometry and its material properties. How: • Create a self-regulated software package to optimize the stem geometry by mathematically modeling and controlling the stem geometry using a fixed number of design parameters, create a solid model of the stem assembly, and conduct the finite element simulation. • Design and build experimental apparatus to benchmark and confirm the numerical results.
  3. 3. DELIVERABLES • Numerical analysis method for minimization of stress shielding on a femoral hip implant under static and dynamic loads through geometrical manipulation • Experimental verification and benchmark of the numerical analysis results.
  4. 4. OSTEOPOROSIS • Secondary Osteoporosis • Bone fragility due to bone density reduction • Caused by a variety of factors
  5. 5. STRESS SHIELDING Femur Bone Bone with Implant
  6. 6. MATHEMATICAL MODEL 𝑥 𝑎 𝑝 + 𝑦 𝑏 𝑝 = 1
  7. 7. FINITE ELEMENT ANALYSIS ANSYS Static Structural in Workbench. Engineering Data- Titanium, PMMA Cement and Cortical Bone. The IGES model imported into Design Modeler. 1. Meshing Medium mesh with Tetrahedral elements. Elements – About 90,000-100,000 Grid Independent Test 2. Contact Region Stem- Cement: Rough Bone-Cement: Bonded
  8. 8. FINITE ELEMENT ANALYSIS 3. Boundary Conditions • Abductor Muscle force of 1.5 KN at 15° with vertical. • Joint Reaction force of 2.5 KN at 10° with vertical. • Fixed Support at Distal End • Simulates average walking conditions. • Fatigue Tool • Goodman Theory • Text file of equivalent alternating stress.
  9. 9. NUMERICAL ANALYSIS RESULTS Compare stress over the surface of bone. Stress Diff = (σ′1 −σ1)2 +(σ′2 −σ2)2 +(σ′3 −σ3)2 +..+(σ′ 𝑛 −σ 𝑛)2 𝑛
  10. 10. NUMERICAL OPTIMIZATION OF STEM GEOMETRY Design of Experiments Method • Developed by Genichi Taguchi from Japan during late 1940. • Suggested fractional factorial experiments using orthogonal arrays. • Type of orthogonal array based on the number of variables and their levels. • Best design parameters will identified from orthogonal arrays. • About 20 variables for cross section of stem geometry. • L32 orthogonal array was used.
  11. 11. TYPE OF SENSOR Sensor Electrical Strain gage Piezoelectric Sensor Fiber Bragg Sensor Temperature effect on zero point Low NA High Drift Small Large Small Temperature coefficient of sensitivity High but compensable Low High Linearity High Low NA Static measurement Applicable NA Applicable Dynamics measurement Applicable Applicable Applicable
  12. 12. MEASUREMENT SYSTEM The system consists of • Power supply provides ± 15 V, 12V, and 5V • 6 strain gage modules • DAQ device
  13. 13. MEASUREMENT SYSTEM – POWER SUPPLY
  14. 14. MEASUREMENT SYSTEM
  15. 15. MEASUREMENT SYSTEM LabVIEW Program for DAQ • Measuring the Output voltage of the strain gage module. • Measuring the Excitation Voltage. • Smoothing the measurement with the Moving Average Filter. • Computing strain and stress value. • Exporting the data to Excel.
  16. 16. MECHANICAL DESIGN Designed for Little Tensile Tester Machined Force Applied Part Hip Cup Part Base Plate
  17. 17. MECHANICAL FORCE ANALYSIS • Sum of moment about L to solve for Fa and Xl such that the give forces for the test condition are met.
  18. 18. BUDGET Total Budget: $1,000.00 Expenses: Electronic Components: $232.74 Instrumentation Amplifiers (6) Circuit Components Strain Gages (6) Mechanical Components: $22.98 Crimps and Cable Total Sent: $255.72 Budget Left: $744.28
  19. 19. FUTURE WORK • Experimentally measure Stress Array in Femur Bone • Experimentally measure Stress Array in Non- Optimized Implant • Experimentally measure Stress Array in Optimized Implant
  20. 20. REFERENCES [1] Kurtz S, Ong K, Lau E, Mowat F, Halpern M, Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030, J Bone Joint Surg Am. 2007 Apr;89(4):780-5. [2] Raut, V. V., Siney, P. D., and Wroblewski, B. M., 1995, ‘‘Revision for Aseptic Stem Loosening Using the Cemented Charnley Prosthesis,’’ J. Bone Joint Surg. Br., 77-B, pp. 23–27. [3] Raut, V. V., Siney, P. D., and Wroblewski, B. M., 1995, ‘‘Cemented Revision for Aseptic Acetabular Loosening,’’ J. Bone Joint Surg. Br., 77-B, pp 357-361. [4] Ali Abdulkarim, Prasad Ellanti, Nicola Motterlini, Tom Fahey, and John M. O'Byrne, Cemented versus uncemented fixation in total hip replacement: a systematic review and meta- analysis of randomized controlled trials, Orthop Rev (Pavia). Feb 22, 2013; 5(1): e8 [5] Li C, Granger C, HD. Progressive failure analysis of laminated composite femoral prostheses for total hip arthroplasty. Biomaterials 2002;23:4249–62. [6] Wolfram Mathematica, http://www.wolfram.com/mathematica/ [7] SolidWorks Corporation, http://www.solidworks.com/ [8] ANSYS Corporation, http://www.ansys.com/ [9] Lennon, A.B., McCormack, B.A.O., Prendergast, P.J., 2003. The relationship between cement fatigue damage and implant surface finish in proximal femoral prostheses. Medical Engineering and Physics 25, 833-841. [10] Jeffers, J.R.T., Browne, M., Taylor, M., 2005b. Damage accumulation, fatigue and creep of vacuum mixed bone cement. Biomaterials 26 (27), 5532-5541.
  • AkHilJHny

    Jan. 14, 2017
  • ShivaHiremat

    Oct. 16, 2016

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