Muscle function in response to rotational perturbation of the glenohumeral joint

111 Pages·2002·4 MB·English

by  Hatzel, Brian Michael

MUSCLEFUNCTIONINRESPONSETOROTATIONALPERTURBATIONOFTHE
GLENOHUMERALJOINT
By
BRIANMICHAELHATZEL
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTL^LFULLFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2002
DEDICATION
ThisdissertationisdedicatedtothememoryofAlbertRoutledge,Doris
Routledge,RussHatzel,andMaryHatzel. Theirendlessencouragementinthepursuitof
mydreamswaslimitlessandtheirsupportandbeliefinmehavebeenimfaltering,and
stillare,mygreatestinspirationforlife.
ACKNOWLEDGEMENTS
Iwouldliketothankthemembersofmydissertationcommittee,Dr.Marybeth
Horodyski,Dr.KeithMeister,Dr.DenisBrunt,andDr.MikePowers,forthetime,
patienceandexpertisethattheyhaveprovidedmethroughoutthisendeavor. Iwouldlike
tomakespecialmentionofmyadvisorandmentor,Dr.MarybethHorodyski,forher
guidedsupportandforgivingmetheopportunitytopursueandachievethisgoal. I
wouldalsoliketothankDr.TomKaminskiforhisendlesscommitmentanddedicationto
measaneducator,researcherandmentorthroughoutmytenureattheUniversityof
Florida. Inaddition,IwouldliketoacknowledgethelateDr.MarkTrimble,forhis
technicalandtheoreticalsupportofthisprojectintheearlystagesofitsinception;his
personalcompassionandcollegialrespectforhisstudentswereadmirable. AsawholeI
wouldberemissinnotthankingtheUniversityAthleticAssociationforsupportingme
throughoutmypastthreeyearsandgivingmesuchinvaluableexperienceinthefieldof
athletictraining.
Iwouldalsoliketoacknowledgemyfamilyfortheircontinuedsupportand
encouragement. Iwillbeforeverindebtedtothemfortheunrivaledsupportandlovethat
theyhavesuppliedmethroughouttheupsanddownsofmypersonalandeducationallife.
Lastly,mysincerestthanksgotomybestfriendandconfidant,GayleHatzel,whohas
beenthesinglemostvaluablesourceofinspirationandsupportthroughoutthisendeavor.
Withouthersupportandimderstandingthiswouldnothavebeenpossible.
iii
1
TABLEOFCONTENTS
Page
ACKNOWLEDGEMENTS
iii
ABSTRACT vi
CHAPTERS
INTRODUCTION
1 1
StatementoftheProblem 7
ResearchHypotheses 8
DefinitionofTerms 8
Assumptions 10
Limitations 11
Significance 1
2 REVIEWOFLITERATURE 12
StaticStabilizers 12
DynamicStabilizers 18
NeuromuscularControl 23
Conclusion 41
3 MATERIALSANDMETHODS 43
Subjects 43
InstrumentationandSetting 44
Measurements 46
Procedures 46
DesignandAnalysis 51
4 RESULTS 52
SubjectDemographics 52
StatisticalAnalysis 54
ANOVA-ReflexLatency 54
iv
5 DISCUSSION 69
Conclusions 79
Summary 80
ImplicationsforFutureResearch 81
APPENDICES
A ELECTRODEPLACEMENTSPECIFICATIONS 82
B INFORMEDCONSENTFORSUBJECTPARTICIPATION 83
C MEANSFORMUSCLELATENCYUSEDINDATAANALYSIS... 89
D ANOVATABLES 90
E TUKEYHSDPOST-HOCANALYSES:CALCULATIONOFCRITICAL
VALUES 91
F DEPENDENTT-TESTINFORMATION 92
REFERENCES 93
BIOGRAPHICALSKETCH 103
AbstractofDissertationPresentedtotheGraduateSchooloftheUniversityofFloridam
PartialFulfillmentoftheRequirementsfortheDegreeofDoctorofPhilosophy
MUSCLEFUNCTIONINRESPONSETOROTATIONALPERTURBATIONOFTHE
GLENOHUMERALJOINT
By
BrianMichaelHatzel
December,2002
Chair:MaryBethHorodyski,Ed.D.
MajorDepartment:ExerciseandSportSciences
Theglenohvmieral(GH)jointhasbeendescribedasthemostmobileand
potentiallyunstablejointinthebody. Thepiuposeofthisstudywastodescribethe
timing(latencies)ofmuscularfiringinnormalhumansubjectsversusthosewithshoulder
instability. Subjectsmakingupthecontrolgroup(N=5;ht=70.0±1.41in;age=21.6
±2.07yr.;wt=189.0±27.7lbs.)werematchedtotheparticipatinginstabilitysubjects
byheight,weight,ageanddominantshoulder. Thosethatmadeuptheinstabilitygroup
(N=5;ht=70.0±1.41in.;age=22.0±3.08yr.;192.0±29.49lbs.)presentedwitha
historyofsubluxationordislocationtotheirdominantshoulder. Utilizingfinewireand
surfaceelectromyographic(EMG)techniques,subjectreflexlatenciesweremeasuredin
responsetoanexternal(ER)andinternal(IR)rotationalperturbation. Astheperturbation
wasappliedtotheGHjointthesubjectswereaskedtoresistthemovementandkeepthe
shoulderfix)mmovinginthedirectionoftheperturbation. Afterdatacollection,one3
waymixedmodelanalysisofvariance(ANOVA)wasperformed.Thebetweensubjects
vi
factorwasgroup(unstable,control),thewithinsubjectsfactorsweremusclesinvestigated
(subscapularis,teresmajor,supraspinatus,andinfraspinatus)andmovement(IR,ER). An
apriorialevelofsignificancewassetatP<0.05forallcomparisons. TheANOVA
revealedsignificantdifferencesinthemovement,muscleandgroupmaineffects,
movementbygroupinteraction,musclebygroupinteraction,movementbymuscle
interactionandthemovementbymusclebygroupinteraction. Significantdifferenceswere
followedbyTukeyHSDpost-hocanalysis. Theresultsofthisstudyindicatethatthe
imstablegrouppossessedsignificantlylongerreflexlatenciesthanwerenotedinthe
controlgroupforbothmotions.Giventheresultsofthisstudy,itissafetoassumethat
significantdecrementsinstabilityexistbetweenthosewithshoulderinstabilityandthose
without. Inconclusion,practitionersmustidentifytheseareasofdeficiencyinthe
pathologicalshoulderinordertothwartthenegativeinvolvementoftheshoulder
instabilityparadigm.
vii
CHAPTER
1
INTRODUCTION
Theglenohiimeral(GH)jointhasbeendescribedasthemostmobileand
potentiallyunstablejointinthebody.*Shouldermjuriesarefrequentandoftenextensive
insportsoroccupationsduringwhichthearmismovedatahighvelocity,underload,or
stressedatendrangesofmotion. Duetotheextensiveamountofmotionallowedatthe
GHjoint,stabilityisoftencompromisedformobility. AlthoughtheGHjointallows
significantphysiologicalmotion,onlyafewmillimetersofhumeralheadtranslation
occursduringthesemovementsinthenormalindividual.^"^Demandingtheutmostin
mobilitywhileaccommodatingrelentlessforceisanessentialanddangerouscompetition
betweenstructureandftinction. Functionoftheshoulderisdependentonmanyfactors.
Itisimportantforclinicianstocontinuetheirquesttodiscovertheintricaciesofshoulder
ftinctionanddysftmction.
TheGHjointconsistsofahumeralheadarticulatingwiththeglenoidone-fourth
itssize. Thisfeatureprovidesforauniquerangeofmotionandshock-absorbing
capability.^ Stabilizingsuchanarticulationisoneoftheuniquechallengesof
musciJoskeletalanatomyandmechanics. Inorderforajointtomaintainstabilization
duringsuchdemandingftmction,itisimperativetoappreciatetheinvolvementofrelated
structuresthatmustworktogethertocontributetoafunctionaloutcome. The
interdej)endenceoftheGHjointandsurroundingstructuresrequiredtomaintainshoulder
stabilityforcestheneedforresearcherstounderstandalloftheanatomicalstructuresin
1
2
theshoulderregion. Functionalshoulderstabilityismaintainedbytheintegrationof
staticanddynamicmechanisms.
Thestaticmechanismencompassescapsuloligamentousstructuressuchasthe
jointcapsule,labrum,andGHligaments. Thesestructuresfunctionascheckreinsto
excessivetranslationorrotationofthehumeralheadontheglenoidbutarelaxinthe
midrangesofmotion.^TheGHcapsuleandligamentsalsopossessneurosensory
characteristics. Mechanoreceptors,imbeddedwithincapsuloligamentoustissue,detect
jointloadsandtransmitsensoryinformationregardingjointmotionandpositiontothe
centralnervoussystem(CNS).7'9
Althoughfourtypesofreceptorsaredispersedthroughoutligamentousand
capsulartissues,Rufifinireceptorsarethemostfrequentlydescribed.'^ Theyare
consideredtobehaveasbothstaticanddynamicreceptorsbasedontheirlow-threshold,
slow-adaptingcharacteristics." Incontrast,thelow-threshold,rapidlyadapting
characteristicsofPaciniancorpusclescausethemtobeexclusivelyclassifiedasdynamic
receptors.'' AlsopresentinthesetissuesisGolgitendonorgan-likeendingsandfree
nerveendings.''"''*
Tenomuscularstructurescontaintwotypesofmechanoreceptorsthathave
receivedattentionfortheircontributiontojointmotion. Golgitendonorgans(GTOs)
provideinformationonmuscletensionwhilemusclespindlesencodesignalsconcerning
musclelength. RecenttheoriessuggestthatthesensoryarticularreceptorsandGTOs
influencemusclespindlesensitivityandthereforemediatemuscleactivityandmuscle
Thesensoryinformationtransmittedfrommechanoreceptorsisutilizedbythe
CNSforconsciousandunconsciousappreciationofjointmotionandposition. A
complexnetworkofsynapsesinthespinalcord,brainstem,andcerebralcortexlinks
afferent(sensory)pathwayswithefferent(motor)pathways.Peripheralreceptorsnotonly
provideinformationregardingproprioceptionandkinesthesia,butalsocontributetothe
involuntaryandvoluntarymuscleactivationrequiredforneuromuscularcontrol. The
involuntaryactivationinfluencesmuscletoneandmusclereflexes. Voluntarymuscle
activationresultsinpreprogrammingofmotorpatternsforplaimedfunctionalactivities
oftheextremity.^''^''^ Thecomplexityoftheshoulderisnecessarytoprovideefficient,
coordinatedmovementofajointthatismulti-planarandmulti-tasked.Inordertoachieve
functionalmotionoftheshoulder,communication,synergismandantagonismamongst
allinvolvedstructuresmustbestrict. Forexample,inthrowingaball,particularmuscle
activationsequencesoccurintherotatorcuffmusclestoensurethattheoptimal
glenohumeralalignmentandcompressionrequiredforjointstabilityareprovided. These
muscleactivationstakeplaceunconsciouslyandsynonymouslywiththevoluntary
muscleactivationsdirectlyassociatedwiththeparticularsofthetask(i.e.,aiming,speed,
distance). Proprioceptiveinformationconcerningthestatusofthejointandassociated
structuresisessentialforneuromuscularcontrol.
Adelicatebalanceexistsbetweenthestaticanddynamicrestraintmechanismsin
theGHjointandalterationsmayevokeshoulderdysfunction. Injurytothestatic
restraintsmayresultinincreasedlaxityandpotentiallydecreasedstabilization;
meanwhile,injurytothedynamicmechanismmayleadtoimpairmentsinneuromotor
controloverthemusclescrossingtheGHjoint. Thequestionexists:whatoccursfirst.