Paper ReviewPaper Review

Contribution of the extrinsic and intrinsic hanContribution of the extrinsic and intrinsic hand muscles to the moments in finger jointsd muscles to the moments in finger joints

Z.M. Li, V.M. Zatsiorsky, M.L. LatashZ.M. Li, V.M. Zatsiorsky, M.L. LatashClinical Biomechanics 15(2000)Clinical Biomechanics 15(2000)

學號：學號： N16941703N16941703 學生學生 : : 洪振翔洪振翔 指導教授指導教授 : : 朱銘祥 朱銘祥 林宙晴林宙晴實驗室：人機系統實驗室實驗室：人機系統實驗室2007/05/292007/05/29

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OutlineOutline

• IntroductionIntroduction• GoalsGoals• MethodsMethods• ModelingModeling• ResultsResults• DiscussionDiscussion

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Introduction(1)Introduction(1)• Extrinsic muscles: originate outside the hand.Extrinsic muscles: originate outside the hand. - responsible for the primary functioning in a variety of tasks- responsible for the primary functioning in a variety of tasks - extensor- extensor 、、 flexorflexor

• Intrinsic muscles: originate and insert within the hand.Intrinsic muscles: originate and insert within the hand. -provide necessary balance and fine tuning of the multi-joints system-provide necessary balance and fine tuning of the multi-joints system

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Introduction(2)Introduction(2)• In clinical practice the force of FDP is estimated In clinical practice the force of FDP is estimated

subjectively.subjectively.

• If we want to calculate the moments at the finger If we want to calculate the moments at the finger joints in static conditions, both the magnitude and joints in static conditions, both the magnitude and direction of the external force must known.direction of the external force must known.

• In this study, a novel measuring system (the In this study, a novel measuring system (the suspension system) was developed.suspension system) was developed.

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GoalsGoals• To develop a method of estimating force produced by To develop a method of estimating force produced by

the flexor digitorum profundus (FDP), flexor digitoruthe flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS) and intrinsic muscles (INT).m superficialis (FDS) and intrinsic muscles (INT).

• To estimate the contribution of these muscles to the fiTo estimate the contribution of these muscles to the finger joint moments.nger joint moments.

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MethodsMethods• ApparatusApparatus -the suspension system-the suspension system• Ten right-handed maleTen right-handed male

• Experimental procedureExperimental procedure 1. three location1. three location -ExpDP, ExpDIP, ExpPIP-ExpDP, ExpDIP, ExpPIP

2. press down maximally2. press down maximally -the interphalangeal joints are fully extended-the interphalangeal joints are fully extended

3. EMG of EDC3. EMG of EDC (extensor digitorum communis)(extensor digitorum communis)

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Modeling(1)Modeling(1)• Finger joint momentFinger joint moment

• Muscles counterbalancing an external finger moment Muscles counterbalancing an external finger moment at the joints at different loop positionsat the joints at different loop positions

( ) ( ) ( )2 2 2

0 ( ) ( )0 0 ( )

DP DP DPDIP PIP MCPDIP DIP DIPDIP PIP MCPPIP PIP PIPDIP PIP MCP

DP DP DPDP DP DPIP IP PP

DIP DPIP IP PP

PIPPP

M M MM M M M

M M M

L L LP P L P L L

P L P L LP L

where is the moment at joint produced by external forcek kjM j P

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Modeling(2)Modeling(2)• Analysis of muscle forces and their contribution to Analysis of muscle forces and their contribution to

joint momentjoint moment

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Results(1)Results(1)• Contribution of muscle groups to joint momentsContribution of muscle groups to joint moments For ExpDP,For ExpDP,

For ExpDP,For ExpDP,

For ExpDIP,For ExpDIP,

, , 100%DP DPFDP PIP FDS PIPC C

, , , 100%DP DP DPFDP MCP FDS MCP INT MCPC C C

, , 100%DIP DIPFDS MCP INT MCPC C

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Results(2)Results(2)• Muscle forcesMuscle forces The maximal forces produced by individual muscles depended The maximal forces produced by individual muscles depended

on the experimental condition.on the experimental condition.

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Discussion(1)Discussion(1)• The “suspension” design in this study is The “suspension” design in this study is

advantageous in that the orientation of force advantageous in that the orientation of force application can be pre-specified.application can be pre-specified.

• In this study the fingers were extended and the force In this study the fingers were extended and the force was applied at the middle of the distal phalanx which was applied at the middle of the distal phalanx which might be similar to the pulp pinch posture.might be similar to the pulp pinch posture.

• In the model, the contribution of the INT to the In the model, the contribution of the INT to the extensor mechanism at the PIP and DIP joints was extensor mechanism at the PIP and DIP joints was neglected.neglected.

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Discussion(2)Discussion(2)• The dorsal and palmar interossei and lumbricals were The dorsal and palmar interossei and lumbricals were

lumped together and viewed a single muscle that prodlumped together and viewed a single muscle that produced a moment solely at the MCP joint.uced a moment solely at the MCP joint.

• The assumption is justified because in the experimentThe assumption is justified because in the experiments the fingers were extended.s the fingers were extended.

• As a result, the effects of extensor mechanism are relaAs a result, the effects of extensor mechanism are relatively small when the point of force application is at dtively small when the point of force application is at distal position.istal position.

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Thanks for your attentionThanks for your attention