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Unformatted text preview: Please review and complete the required information on this cover page before answering the questions. Biomechanics BME 4540 Department of Biomedical Engineering Rensselaer Polytechnic Institute In-class closed book Exam 111 Duration: One hour & 50 minutes (2 PM to 3:50 PM) Total points: 100 Name: S o W or QM This examination accounts for 15% of your final grade. Please read the instructions carefully and answer each question to the best of your abilities. Total number of pages including cover 10 provided. Be specific and brief. each guestion. Allocate your efforts accordingly and do not exceed the space 1. Articular cartilage derives its mechanical properties from a complex interaction among its components including collagen, proteoglycans, water, sodium, and calcium ions. Explain how salt concentration and pH affect the compressive properties of the cartilage (8 points) 2 Using the given information determine the type of contraction the quadriceps will undergo when IABlE 54.? TYPES OF MUSCLE WORK AND CONTRACHON STATIC WORK No macmnlcnl work pedunm‘ lbs-um nrjoint pom Ire-named " “m” . EOME‘FW' CONTRACHQN Muer mean mum external load Mum: WW” ECEENTRJC comm Mm tension equm edema! Load. MUSUC whens. JSOKINE'ITC CONTRACTJGV Cmmlynlpwrmfim Mmmal m mom WEE]. (a) One is extending the knee to climb the steps (b) One is decelerating the knee flexion while descending stairs C Dmém‘i‘flfi g @Qfl'd‘r id- IIYNAMIC WORK Mechanics! won: pelfamed, lamination gamut ISOWERHAL CONIM mm film bl “El I” load Whit mymucm . u . I 50mm (Wm-10104 Mime mean cdumc WW (_4 points) (4 points) __________m 3. Identify the wear mechanism of ultra-high-molecular-weight polyethylene acetabular component shown below: (6 points) (a) (b) (c) 4. An electrical strain gage rosette was installed on each proximal lateral quadrant of three human femurs containing a press-fitted implant (Femur A), a cemented implant (femur B), and no implant (femur C). The strain-gaged femurs were then placed in a material testing device simulating the single leg stance (See Figure below). Strain gage rosette used for measuring strains 51, 82, and 83 F iggre: Testing configuration with the femur C placed in a materials testing device under axial load simulating a single leg stance For comparing the strains generated during physiological activities in the implanted and non-implanted femurs, an axial load was applied at the femoral head to generate the same magnitude of joint reaction force in all three cases. The strain values 81, 82 and 63, measured from the proximally installed strain gage rosette were converted into the following normal (ex, 8y) and shear (7“) strains for femurs A, B and C (table 1). Table 1 Strain Rosette F emur A F emur B F emur C Readins (.7 -, ) ( _.-_~ .... t) ( 5x 1.64 E-OS 5.83 E-05 1.4 E-04 5,, 3.06 E-06 I 1.77 E-05 4.63 E-05 x 4.568 E-05 -3.078 E-05 -4.53 E-05 (a) Using strain values ex, tall and m given above in Table 1, calculate the principal strains (81 and en) for femurs A, B and C. (b) Using the results from (a), which of the two implants (press-fitted or cemented) would you recommend to a 40-year-old male patient undergoing hip surgery? Justify your answer giving reasons. (c) Would your recommendation for a 80-year old grandmother be same as in case (b). Justify your answer giving reasons. (20 Points) 5. Strain values calculated along the material axes (1,2) of a human tibia for uphill and downhill running exercises are given below. (12 Points) Imam afib%4xme m=6flxlfifi nrvamxwe Downhill: 51 = 707 x 10" £2 = —517 x 10'6 y” =1224 x10—6 Assuming bone to be a transversely isotropic material subjected to plane stress, calculate stresses along the material axes for both exercises and identify the orientation of the plane for both exercises where shear stresses are zero. The values of elastic constants, Poisson’s ratio and other useful mathematical functions for human bone are given below. E11 = 17 GPa E22 = 11.5 GPEI V12 = 0-46 V21 = 0.31 G12 = 3.28 GPa 1H 1—Ell-—=19.72(}Pa #:1343GP51 #:6JZGPa _ _ V12V21 _ V12V21 ‘ . — V12V21 ' W a - ~+’V v49“? a - M. ‘W a . . (7 i ' 22‘ 6 C3 67'?» H 'l 25 E9 ‘2 ,E I:-‘ 2 M 31am: mes - :1 Pmsépm straws an a firlncnecé stress-2s 5/40 M Dowhhm _______————."— 6. The schematic and graphs given below illustrate commonly used internal fixation techniques and their mechanical and biological performances measured from animal testing under identical laboratory conditions. Note that the mechanical and biological performances are expressed as a % of the intact femur and % change, respectively. . Torsional slllfnese Fallure 5:, Bending “We load Intact femur, % Body weight. % den Elise- I Elam I w Kempt plate We Mechanical Performance ‘" Room ‘93 Enders Blade Plate Perinatal Endoeleal Porosity new bone new bone Biological Performance (a) Based on the mechanical performance alone, which of the four internal fixation technique (Enders, Grosse-Kempf, Blade Plate and Screw Plate) would you recommend to a surgeon for a patient subjecting his/her bones to normal daily loading? Explain giving reasons. (b) Based on biological performance alone, which of the two internal fixation technique (nail or plate) would you recommend to a surgeon for a professional skier who is susceptible to torsional ski injuries? Explain giving reasons. (10 points) 7. An 890 N man is standing on one foot. Find the magnitude and the direction of the joint reaction force on the head of the supporting femur. The schematic below shows the location and the magnitude of the centers of gravity for the body and the lower leg. “M” is the unknown tension in the hip abductor muscle group (attached at point 0) acting at 71° with the horizontal. Jx and Jy are the unknown x— and y—components of the joint reaction force. (12 points) f: M : 0 {2 9 I &W\ far i 1 Pmm; ’ E ' a i [x .2 c) ( i moan H) E I 7’; 4,19 1:13 "t I "1.2 #1, _~ o (Ditto) : % x _ 0 web) 'I [394: I . I . 1/ :' 7,- 331 4 '37?» I P ' t 1 5) (its ' (a a s at - c «s We tom Q 9 i {j k})\ " . O r 0 find; 8. From the three choices given below, identify the external fixator (A, B or C) that will provide superior resistance against the application of anterior-posterior bending (4 points) 9. Identify the correct choice: (4 points) Strength of the external fixation device shown under choice B could be increased by: (a) decreasing the number of pins to 2 from 6 (b) increasing the pin diameter from 2 to 4 mm (c) decreasing the distance of the frame from the bone (d) (a) and (b) (e) (a), (b) and (c) W: igi iai and (c) 10. State true or false giving reasons: (16 points) (a) Nonsteroidal anti-inflammatory drugs (NSAID) including asprin and acetaminophen decrease the tensile strength of ligament and tendon. £3“? '1‘W T xvmm (b) Bones can fail when loaded below the yield point during physiological activities including long distance running, marching and ballet dancing. M— (c) A soccer player immobilized for 8 weeks following quadriceps injury permanently looses some strength of his/her ACL. we: - (d) Ligament and tendon do not remodel in response to the mechanical demands placed on them. -§¢.Q-WWféfi.W of W 10 ...
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This note was uploaded on 09/07/2008 for the course BMED 4540 taught by Professor Vashishth during the Fall '07 term at Rensselaer Polytechnic Institute.

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