comparison of alternative rigid sternal fixation techniques

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Comparison of Alternative Rigid Sternal Fixation Techniques

By

John C Dieselman

A Thesis

Submitted to the Faculty

Of the

WORCESTER POLYTECHNIC INSTITUTE

In partial fulfillment of the requirements for the

Degree of Master of Science

In

Biomedical Engineering

Fall 2011

Thesis Committee:

Kristen Billiar, Ph.D., Advisor, Biomedical Engineering

X

George Pins, Ph.D. Biomedical Engineering

X

Raymond Dunn M.D., University of Massachusetts Medical School

X

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Acknowledgements

Iwouldliketothankallthemembersofthethesiscommittee,especiallyProf.KristenBilliar,fortheirsupportandinvaluableguidanceoverthecourseofmyresearch.

IwouldalsoliketothankRaymondDunnMD,RonaldIgnotzMDandJaniceLalikosMDofUniversityofMassachusettsMedicalCenter,Worcesterfortheirclinicalexperience,insightandsupport.

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Abstract

Sternalmalunionisacomplicationresultingindisplacementofthesternalhalvesfollowingopenheartsurgery.Currently,littleisknownabouttheeffectivenessofalternativefixationsystemsunderphysiologicallyrelevantloadingscenarios.Thegoalofthisstudywastomechanicallytestseveralcurrentlymarketedsternalfixationdevicesandcomparethemtoaprototypedeviceindifferentloadingconditionstosimulatesittinguporbreathing.Eachsystemshoweduniquedifferencesincost,failuremodeandefficiency;however,nostatisticaldifferenceinfailureloadordisplacementwasobservedbetweenthetestinggroups.

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TableofContents

1.Introduction.....................................................................................................................................1

2.Background......................................................................................................................................4

2.1OpenheartStatistics..........................................................................................................................4

2.2SternumAnatomyandPhysiology......................................................................................................4

2.3SternotomyProcedure........................................................................................................................7

2.4SternalFixationMethods....................................................................................................................8

2.4.1WireFixation................................................................................................................................8

2.4.2RapidSternalClosureTalonSystem.........................................................................................9

2.4.3RigidFixationviaPlateandScrewSystem...................................................................................9

2.5TypesofRigidFixation:Plates...........................................................................................................11

2.6TypesofRigidFixation:Screws.........................................................................................................13

2.6.1ScrewDesign..............................................................................................................................15

2.7SternalLoading.................................................................................................................................16

3.MaterialsandMethods..................................................................................................................18

3.1DeterminationofSternalModel.......................................................................................................18

3.2LateralDistraction.............................................................................................................................19

3.3LongitudinalandTransverseShear...................................................................................................20

4.Results...........................................................................................................................................23

4.1LateralDistraction.............................................................................................................................23

4.2LongitudinalShear............................................................................................................................25

4.3Transverseshear...............................................................................................................................26

5.Discussion......................................................................................................................................28

6.Conclusions....................................................................................................................................31

WorksCited.......................................................................................................................................33

AppendixA:LateralDistractionData.................................................................................................36

AppendixB:LongitudinalShearData.................................................................................................39

AppendixC:TransverseShearData....................................................................................................41

AppendixD:InstronE1000information.............................................................................................42

AppendixE:CustomGripDrawings....................................................................................................43

AppendixF:Inventory........................................................................................................................45

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TableofFiguresFigure 1: Muscles involved in respiration cycle ............................................................................. 5Figure 2: Spirogram of adult lung volume and capacity ................................................................. 6Figure 3: Anatomy of an Adult Human Sternum (Sandring, 2004) ............................................... 6Figure 4: Cross-section of Human Sternum.................................................................................... 7Figure 5: Sternum Closed by Wire Fixation (Shields et al, 2004) .................................................. 8Figure 6: Talon system and Placement (rapidsternalclosure.com) ................................................. 9Figure 7: Sternum Closed by Rigid Plate Fixation (Song et al, 2004) ......................................... 10Figure 8: X shaped plate and Straight plate (Based on (Ozaki, 1999)) ........................................ 11Figure 9: A wave style compression plate (An, 2002) .................................................................. 12Figure 10: A Meyrueis friction plate (An, 2002) .......................................................................... 13Figure 11: Anatomy of a bone screw (Akbar Bonakdarpour, 2009) ............................................ 14Figure 13: Screw Pitch Parameters (An &Draughn, 2000) .......................................................... 16Figure 12: Visualization of loading directions, courtesy of KLS martin ...................................... 17Figure 14: Schematic of Sternal Talon in Lateral Distraction ...................................................... 19Figure 15: Example of a failure due to Rib Fracture (Left), and longitudinal shear test schematic (Right). .......................................................................................................................................... 22Figure 16: Typical loosening curve .............................................................................................. 23Figure 17: Comparison of the Sternal Talon (KLS Martin), Anti-Wobble Screw prototype and Biomet Sternalock systems in lateral distraction .......................................................................... 24Figure 18: Force and displacement of different screw systems in Longitudinal Shear. ............... 25Figure 19: Comparison of test groups in transverse shear. ........................................................... 27Figure 20 Top: Rotation of linear AntiWobble plates in Longitudinal Shear. Bottom: Proposed anti-rotation plate as shown in (Ahn et al, 2009) .......................................................................... 29Figure 21: Reduction technique using AntiWobble screw. Left: Screw is inserted with lateral trajectory. Right: Screw is forced into alignment by AntiWobble Cap ........................................ 30

TableofTables

Table 1: Failure forces of Sternal Fixation Systems in Longitudinal Shear ................................. 26

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1.IntroductionAs of February 1st, 2011 the American heart association estimates that 82,600,000

American adults have developed one or more types of cardiovascular disease. The same survey

shows that in 2007 there were over 6,846,000 inpatient intratoracic cardiovascular operations

performed in the US (American Heart Association, 2011). At the beginning of every open-heart

surgery the sternum is bisected to allow access to the heart. This procedure is known as a

sternotomy. This technique is essential for a vast majority of interthoracic surgeries. Following

the completion of the procedure the sternum must be realigned and secured with a sternal

fixation device.

In 98% of procedures the reapproximation is successful; however in the remaining 2%

post operative complications occur (Casha, 1999). Usually this is due to low bone integrity