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1 MME2259a November 9, 2012 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. [email protected] For Dr. Paul Kurowski’s Engineering Design Class MME2259a November 9, 2012
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MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. [email protected].

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Page 1: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

1MME2259a November 9, 2012

Engineering Contraception

The TCu380A

Intrauterine Contraceptive Device

Steve Nazar, MSc.Nazar Associates Inc.

[email protected]

For Dr. Paul Kurowski’s Engineering Design Class MME2259a

November 9, 2012

Page 2: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

2MME2259a November 9, 2012

Global Significance of Birth ControlThomas Malthus, 1798: “Population grows exponentially, but resources are finite.”

Population projections

Page 3: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

3MME2259a November 9, 2012

(Modified from U. Michigan course noteshttp://www.globalchange.umich.edu/globalchange2/current/lectures/human_pop/human_pop.html)

“Demographic Transition” happens ONLY because of birth

control!

Page 4: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

4MME2259a November 9, 2012

Modes of Birth Control

• Diaphragms (barrier method)

• Condoms (barrier method)

• Foams and creams (spermicides)

• The Pill (daily hormonal management)

• Norplant, Depo-Provera (slow release hormone implants)

• Surgical ligations, male or female (irreversible)

• Intrauterine Contraceptive Devices:• Copper-bearing, and• Hormonal slow release

Page 5: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

5MME2259a November 9, 2012

Mirena (TM)

Slow-release levonorgestrel

Page 6: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

6MME2259a November 9, 2012

TCu380A:

“Tatum Tee”; or“Copper T”; or

various trade names

Page 7: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

7MME2259a November 9, 2012

How an IUD is used

Uterus should remain sterile through IUD insertion.Tee frame must unfold promptly after insertionTee frame must fold “upward” for removal – 10 years later

cervix

Issues

Page 8: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

8MME2259a November 9, 2012

IUD Advantages

• Very low cost

• Immediately effective

• Reversible

• Non-hormonal (recent exception – Mirena™)

• Zero maintenance up to 10 years

• No male cooperation needed

Page 9: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

9MME2259a November 9, 2012

IUD Disadvantages

• No protection from venereal diseases

• Pregnancies not completely suppressed

• Moderately high rates of excessive bleeding, cramping, expulsion

• Incidents (extremely rare) of uterine perforations.

Page 10: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

10MME2259a November 9, 2012

The Tatum Tee

Original monograph by Howard Tatum, MD, PhD. 1974

Page 11: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

11MME2259a November 9, 2012

Geneva, 2007

Page 12: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

12MME2259a November 9, 2012

Bangkok Conference, January 2010

Page 13: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

13MME2259a November 9, 2012

Bangkok Attendees, January 2010

Page 14: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

14MME2259a November 9, 2012

Outcome:

Free, online at http://whqlibdoc.who.int/publications/2011/9789241500999_eng.pdf

The new manufacturing and global purchasing standard

Page 15: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

15MME2259a November 9, 2012

Anatomy of a Tatum Tee

Staked copper tubes

Copper wire0.010 inch dia

Wire anchor hole

Ball tip with string hole

Loose wire end

“armpit”

Low Density Polyethylene frame

knot

Oriented high density polyethylene monofilament suture

Starter tag, over-wound

1.25 inches 0.0625 inches

Page 16: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

16MME2259a November 9, 2012

Insertion Tube and Package

Plunger

Insertion tubeDepth marker

IUD

Barrier package for sterility

Page 17: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

17MME2259a November 9, 2012

Three problems:

• Frame material needed generic specification AND substitution

• Armpit radius specification needed range

• Barium sulfate dispersion quality needed specification

Page 18: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

18MME2259a November 9, 2012

Generic Material Specification

• Specification by key properties is needed, NOT tradename & grade

-- Properties had been “grandfathered” i.e. based on past successful IUD use -- NOT theory or measurement.

Thus two problems arise:

• Du Pont will not sell into any long-term human implant market. Alternative resins must be qualified soon!

• We aren’t sure what ranges to use for key functional specifications.

Page 19: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

19MME2259a November 9, 2012

Uncertainty of Single-Source

!

Page 20: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

20MME2259a November 9, 2012

Key Material Properties

• Availability!

• Stiffness in “correct” range

• Toughness retention to 10 years

• Springback (creep resistance)

• No toxic reactions…

• …& lots more…

Page 21: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

21MME2259a November 9, 2012

Some dimensions are fixed, but the armpit could be varied

• Copper area and location cannot be changed• Over-all length and width cannot be changed

(image from Solidworks model)

Page 22: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

22MME2259a November 9, 2012

Model needed -for Stiffness Matching

• A different polymer may have a different stiffness – so how do we adjust the design to compensate?

Beam stiffness formula:

“ Stiffness is proportional to modulus X (section depth)3 ”

But this formula fails for polyethylene!

Page 23: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

23MME2259a November 9, 2012

Typical Polymer Stress vs Strain Curve

ElasticInelastic

Page 24: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

24MME2259a November 9, 2012

Why model?

• Experiments with machined steel mould would be expensive!

• We needed a computational model for stiffness adjustment

• But for the WHO specification, we made educated guesses based on past practice

Page 25: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

25MME2259a November 9, 2012

Three problems:

• Frame material needed generic specification AND substitution

• Armpit radius specification needed range

• Barium sulfate dispersion quality needed specification

Page 26: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

26MME2259a November 9, 2012

Radiusing Problem

• A re-entrant corner is a “stress riser.” Local strains rise rapidly when arms are bent.

• Tatum’s original design did not specify an armpit radius.

• In removal, optimum radius is unclear -- too small a radius encourages cracking, -- too large a radius increases arms’ stiffness

• In insertion, optimum radius also unclear -- interacts with loading devices, as shown by the UWO student team

Page 27: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

27MME2259a November 9, 2012

Deformation: Loading vs Removal

Insertion: risks compressive damageRemoval: risks tensile damage

Worst stretch zone

Worst crush zone

“arms down”“arms up”

Page 28: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

28MME2259a November 9, 2012

1. Arranged collection of 80 used IUDs2. Measured strengths of frames and strings3. Examined armpits by scanning electron microscopy

Bolivia, England, Kenya, Philippines, Vietnam - thanks to Marie Stopes International & Dr. Paul O’Brien, London

Evidence for Role of Radiusing

Page 29: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

29MME2259a November 9, 2012

Compressive damageand then

tensile fracture

Specimen B4, left armpit at 35X

Page 30: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

30MME2259a November 9, 2012

Compressivedamage first

Specimen B4, low magnificaitonright armpit

Page 31: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

31MME2259a November 9, 2012

Many cycles, but -

Oxidative Damage?

Stress-Cracking?

Fatigue?

1200X magnification of right armpit of B4

Page 32: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

32MME2259a November 9, 2012

Aged Frame Strengths

Figure 5: Break strengths of New and Used IUDs (tested in "arms-up" geometry)

20

25

30

35

40

45

0 2 4 6 8 10 12 14 16 18

age in utero , years

bre

ak

str

en

gth

, N

ew

ton

s

UK

Bolivian

Kenyan

Philippina

Vietnamese

New tee strengths n = 19 frames

mean = 38.9 Nstd dev = 1.7 N

Page 33: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

33MME2259a November 9, 2012

Compressive Damage?Consider Tee loaded for insertion:

• Highly deformed into insertion tube• Wide variety of methods of loading

Page 34: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

34MME2259a November 9, 2012

…loading from inserted end:

Page 35: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

35MME2259a November 9, 2012

…loading from inserted end:

Page 36: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

36MME2259a November 9, 2012

…loading from external end

Page 37: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

37MME2259a November 9, 2012

Modeling Needed for

• Stiffness adjustment

• Radiusing

• Loading Devices

Page 38: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

38MME2259a November 9, 2012

Computational Model = “Finite Element Analysis”: FEA

• Model the geometry of the 3D part in (e.g.) Solidworks™

• Measure and input the material stiffness curve (both tension and compression)

• “Mesh” the parts: divide into small elements• Assign loads (“where you push”) and constraints (“where

the part is held”)

• Run nonlinear simulation software

Page 39: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

39MME2259a November 9, 2012

The Western team:2009-2010

Helen BrennickPete McIntosh

Andrea Sylvester

…supervised by Dr. Kurowski

Page 40: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

40MME2259a November 9, 2012

The 4th Year Practicum 2009-2010

Objectives:

• Design and build a simple arm flex tester

• Measure arm stiffness

• Model IUD frame arms-up and arms down by FEA

• Check model predictions against measurement.

Page 41: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

41MME2259a November 9, 2012

Dimensioned IUD dwg – included in WHO specification

• Starter tag over-wind is very difficult to model

• Problems arose from use of student licenses

Page 42: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

42MME2259a November 9, 2012

Arm stiffness instrument

• Inexpensive and rugged

• Slightly difficult to read

Page 43: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

43MME2259a November 9, 2012

Material data for SW nonlinear(from UWO team)

Example data from actual frame material – not corrected yet to “true” stress, strain

Page 44: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

44MME2259a November 9, 2012

From UWO team presentation

Page 45: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

45MME2259a November 9, 2012

Load cases: loading methods

Page 46: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

46MME2259a November 9, 2012

Model conclusions

• Suspicions reinforced, re loading devices causing damage

• But radiusing issue difficult to model quantitatively –

– Large deformations cause failure – (later resolved with 1st order elements)– Nonlinear material input caused program failure – unknown reasons

Removal Insertion

stem

stem

Page 47: MME2259a November 9, 2012 1 Engineering Contraception The TCu380A Intrauterine Contraceptive Device Steve Nazar, MSc. Nazar Associates Inc. nazar-associates1@rogers.com.

47MME2259a November 9, 2012

FEA analysis -- a toolkit for IUD design:

• Adapt design to alternative materials of different stiffness or yield

• Estimate a radiusing specification

• Design or select the least damaging loading devices