Mini Project 3

Mini Project 3: Orthobullets

Jensen Williams, Natalie Ivey, Timothy Lindquist

Question

Summarize the problemWhat is J when the acetabulum is moved medially on a patient standing on their right leg given the information on the next slide?

Collect InformationNon-medial Distance A = 50 mm = 0.05 mDistance B = 100 mm = 0.1 mJ = Resultant Hip Joint Force = 1800 NAT = Abductor Tension = 1200 NFBW = Body weight at pubis = 5/6 x BW = 5/6 x 720 N = 600 N

Medial Distance A = 50 mm = 0.05 mDistance B = 50 mm = 0.05mJ = Resultant Hip Joint Force = UNKNOWNAT = Abductor Tension = UNKNOWNFBW = Body weight at pubis = 5/6 x BW = 5/6 x 720 N = 600 N

Assumptions?Assumptions for this problem include: 1) This material exhibits ideal behavior for the models used. This is termed a LEHI material.2) 2D problem: this simplifies calculation of forces3) Ignore all other forces: just focusing on the hip.4) Hip in static equilibrium: allows for calculations to be set to zero.5) Forces are perpendicular to moment arm: this eliminates the need for force calculations regarding different angles, although some problems might contain angles this one does not.

Isolate the area to be analyzed before drawing the free body diagram

Draw the free body diagram

Pick a point to take moment about

Visualize the moments

Solve for equilibrium of moments

Continue to solve for J

Alternate Way OR A Great Checking Mechanism

Isolate the spot to analyze moment

Visualize the moments

Write moment equilibrium equations

Continue to solve the equations

Equilibrium in y direction

Looking BackEliminating Answers

M = r x FM = r x FFcJM = r x FRed Medial hip body weight momentGreen Medial and nonmedial hip moment from JDark Blue Nonmedial hip moment from body weightFc