Th Anatom an Mechanic o th e Huma Han d CRAI L TAYLOR - PDF document

V V V V V a a a a a a (4) I 1 (12). (4) a a a A a a a (14). a (10). (3). 2 (2). de­ (11) a (6). a A a (13), a a 5 (i.e., measured a a a (8). a Fig 4 Flexor o wris an digits Fo nomenclature se Tabl 2Th tendon o wris an han pas througbon an ligamentou guid systems a showschematicall i Figur 7 Flexo tendon pasthroug a "tunnel bounde dorsall b carpabones laterall b th greate multangula anth projectio o th hamate an volarl bth toug transvers carpa ligament Similarly th dorsal carpa ligamen guide thextenso tendons an a syste o sheathserve a a guid fo flexo an extenso tendonthroug th metacarpa an phalangearegionsTh intrinsi muscle o th hand i.e., thos wit bot origi an insertio confinet wris an han (Fig 8) are wit th exceptio o th abductor o thum an littlfinger specialize fo th adductio o thdigit an fo oppositio pattern suc amakin a fist spherica grasp an s onTH PALMA AN DIGITA PADTh vola aspec o th pal an digit icovere wit copiou subcutaneou fa an a relativel thic ski s designe i a serie ofold tha i i capabl o bendin i prehension Th fold ar dispose i suc a wa at mak fo securit o grasp whil th underlyin fa furnishe paddin fo greate firmnesi holding Because however slippin o thski ove th subcutaneou fa woul lea tinsecur prehension th fold ar tightl boundow t th skeleta elements muc a mat th phalanges Th latte contribut t thwris action particularl unde loads I succases th finge muscle develo reactioagains th objec hel (o withi th hanitsel i th fis clenched an ad thei forcet wris action Th forces action an groupin o thes muscle ar give i Tabl 5PREHENSIO PATTERNI i eviden equall fro a stud o thmuscle-bone-join anatom an fro observatio o th posture an motion o th hantha a infinit variet o prehensio patterni possible Fo purpose o analysis howeveri suffice t describ th principa typesSeekin a logica basi fo definin th majoprehensio patterns Kelle e al (9 fountha th object-contac patter furnishe a satisfactor basi fo classification Frophotographi observatio o th prehensiopattern naturall assume b individualwhe (a pickin u an (b) holdin fo usTabl 4 ANGULA EXTEN O WRIS FLEXIONSFig 9 Nerve supplyin th hand To t bottom ulna nerve media nerve radia nerve Se Tabl 3 Fig 13 Si basi type o prehension a define b Schlesinge (10). equal th tota are devote t arms trunkan leg (3). Thi circumstanc ensure greapotentialit fo coordinate movemen anfo learnin ne activities Similarly thsensor area ar large s tha the determinsuc advance function a stereognosis thabilit t recogniz th shap o a objecsimpl b holdin i i th hand Th greatactil sensitivit o th han is o course ilarg par du t th ric suppl o sens organi th han surfac itself Th threshol fotouc i th finge tip fo example i 2 gmpe sq mm. a compare t 3 an 2 fo thforear an abdome respectivel (2). Th thre majo type o movemen de­scribe b Stetso an McDil (11) ar i parrepresente i th hand The includ fixatiomovement includin cocontractions movement rangin fro slo t rapi wit controo direction intensity an rate an ballistimovementsFIXATIO MOVEMENTI al o th type o prehensio describedth han assume a fixe position I th prehende objec i unyielding reaction t thflexio force ar afforde b th object I thobjec i fragile o th han empty th hani maintaine i an require prehensilpostur b cocontraction o th opposinmuscl groups.Th characteristic o balance musculaactio whe supportin i th han loadwhic produc moment a th wris havbee studie electromyographicall bDempste an Finert (6). I general wheaverag potentia amplitude ar use tcharacteriz th electrica activit o thmuscle th curve o load-actio potentiaar linear Frequencie rang fro 3 t 6pe sec bu bea n clear-cu relationshi tload Typically eac o th muscle traversinth wris wa foun t functio a agonistlatera stabilizer o antagonis a th momenloa wa shifte fro direc oppositio a4 ar man othe example o fixatio stalessuc a th open-cla conformatio o th finger anth extende an rigi inde finge fo dialin a telephone tresse an upholstere furnitur ar quilteo otherwis fastene t preven slippag oth fillerI th hand th vola ski i tie dow bwhit fibrilla tissu connectin th sheath oth flexo tendon t th dee laye o thdermi alon th latera an lowe edge o thpalma fascia Th fold therefor var witth relativ lengtho th metacarpabone an wit thmutua relation oth sheath o thtendon an thedg o th palmafasciaTh sulci o furrows ar emphasizebecaus th subcutaneou fa i angive are i restricte t th interva betwee th linealon whic th skii tie down Thupressur upo anindividua monticulu canno displac th underlyinsof tissu beyonth boundarie establishe b thfibrilla connectionsTh relativ siz oan particula eminenc i a indicatio o th siz oth muscl involvean o it relativ developmenthroug usage witth exceptio thath siz o th hypothena eminencdepend i par upoth prominenc oth pisiformFig 5 Forear desig arelate t han mobilityB virtu o thi arrangement th han ca b rotate throug 18 deg.pal u t pal downwit th elbo flexed Witth ar full extendedparticipatio o shouldean elbo allow th hant b rotate throug almos 36 deg. pal u tpal up U ulna R radiusP pronation S supinationTH DORSA INTEGUMENUnlik th vola surface th dorsa sid oth han i covere wit thin soft pliablski an equall mobil subcutaneou tissuebot capabl o yieldin easil unde tensionBecaus i flexio th finger an i makina fis th coverin o th bac o han musb abl t stretc fro wris t fingernails thdorsa ski i arrange i numerou minutredundancies which i th fiat-of-hand armanifes i th typica transvers wrinklesparticularl ove th phalangea articulationsSpecia adaptation i th dorsa ski o ththum accommodat th distinctiv rotationa planes o tha digi abou it carpometacarpa articulation I th normal healthhand th degre o redundanc i an giveare i jus suc tha al wrinkle ar dispatche whe th fis clenched Swellin ian area dorsa o volar inhibit flexionextensio o th par affectedNERV AN BLOO SUPPLThre principa nerve serv th muscle oth han (Fig 9) Nerv supply i indicatedexcep fo mino variation an exceptions iTabl 3 Eac o thes majo nerv trunkdiverge int countles smalle branche endini th papilla o th palma pad an dorsaskin an th whol neuromuscula syste is coordinate i th brai tha moto respons t stimul i ordinaril subconsciou anreflex Thu a objec slippin fro th grasi automaticall grippe mor firmly bu nos firml a t damag th han itself Noxioustimul ar rejecte automatically a whe Fig 10 Bloo suppl t th uppe extremity A above media vie o th elbow A bottom dorsa vein oth hand B superficia vein o th arm C arterie o th arma Fic (7)' Th palmari longus absen abou 1 percen o cases i omitte fro th summe Fic force o volaflexion. c fro measurement o maximu force norma t th hand applie a th metacarpophalangeajoint o 1 youn male a th Universit o Californi a Lo Angele (unpublishe data) zer deg t th 90-deg an the t th 180deg positions Th magnitud o th actiopotential associate wit eac o thes rolei approximatel i th orde 4:2:1SLO AN RAPI MOVEMENTI movement rangin fro slo t rapidwit contro o direction intensity an ratether i alway som degre o cocontractiot ensur contro an t permi change iforc an velocity A ne forc i th musclecause motion I thi categor i a lon liso activities suc a writing sewing tyinknots an pressin th key o musica instruments Include ar mos action involvindifferentia o integrate motion o th digitsI i o interes t not tha th ful capacitfo thes motion i seldo develope b thaverag individual Wit intensiv practicesignifican increase i th facilit o manipulation eve wit simpl operations ma bachieved althoug individual diffe markedli th amoun o trainin gain Th averagindividua ha laten potentia fo developmeno skill a show b th feat o manipulatiooccasionall evidenced Knot-tying cigaretterolling an simila comple manipulationma b performe wit on hand a oftedemonstrate b accomplishe unilatera aramputees Accordin t Tiffi (13), dexteritdifference ar correlate neithe wit mentaabilit no wit han shap o dimensions buCo (5 point ou tha the hav a importan effec o th performanc o industriaassembl operationsBALLISTI MOVEMENTBallisti movement ar rapi motionsusuall repetitive i whic activ musculacontraction begi th movement givin momentu t th member bu ceas o diministhei activit throughou th latte par o thmotion I i unlikel that o themselves thfinger utiliz thi typ o motio t anmarke degree Barne (/ review evidenctha i repetitiv wor finge motion armor fatiguing les accurate an slowe thaar motion o th forearm Consequently irepetitiv finge activitie i whic ther i a ballisti element suc a piano-playing typingan operatin a telegrap key wris an elbomotion predominat whil th finger merelpositio themselve t strik th prope keyHAN DYNAMICTh han thei actions an contractil force ar give i Tabl 5 take froFic (7) Th tota Fic forc equal th summate force o th individua muscle participatin i th action Fo eac muscl th forci equa t th physiologica cros sectio (i.e., th tota cros sectio o th muscl take norma t it fibers multiplie b th forc factoo 1 kg pe sq cm. estimate b Fic thol fo huma muscle Thes force ar produce alon th axi o th muscl an ittendon bu sinc th effectiv momen arupo an o th wris o han joint i smallth measured isometri force ar onl abou1 percen o th tota forceAmon th wris actions tota force anmeasure isometri force assum th samran order Th variation, wit wris angleo bot flexor-extenso force i th wris ano prehensil force i th han i o practicaimportanc a wel a theoretica interest Thprehensil forc reache a maximu a a wrisangl o abou 14 deg (Fig 12 bottom) Thii approximatel th angl a whic th maximu force o wris flexio an extensio occu(Fig 12 top) I i commo experienc thath wris assume thi angl whe ver stronprehensio i required Th lessene force awris angle towar th extrem position oflexio o extensio ar attributabl t thwell-know forc reduction i th isometrilength-tensio curv a a muscl i markedlstretche o slackene (8). Th exceptio tthi rule see i th augmente forc o flexio a wris angl 8 deg. apparentl meantha thi degre o wris extensio doe nostretc th flexo muscle beyon thei forcmaximumCONCLUSIOThis briefly constitute th anatomicabasi o han mechanics fro whic i cab see tha norma han functio i th resul no onl o a highl comple an versatilstructura arrangemen bu als o a equallelaborat an full automati syste o con Fig 1 Bone an articulation o thhand includin th interosseu muscles Avola view B dorsa view Fo nomenclture se Table 1 an 2Fig 2 Angle o rotatio abou th wrist A extensio (o dorsiflexion) B flexio (o vola flexion) C radiaflexion D ulna flexion Fig 6 Extensor o wris an digits Fo nomenclature se Tabl 2th finger ar withdraw fro a objec uncomfortabl hotTh wris an han receiv thei bloo suppl fro th radia an ulna arteries whicru paralle wit th bone concerned enteth han throug th flexo "tunnel, anthe joi throug a double-arc syste (Fig10) Smal branche fro th arche serv thdigits Th majo venou syste compriseth basili an cephali vein superficiallplace o th vola surfac o th forearmTH RESTIN HAN PATTERTh restin han assume a characteristiposture a featur easil see whe th hanhang loosel a th side Th restin wristake a mid-positio i which wit respec tth extende forear axis i dorsiflexe3 deg (Fig 11) I i wort notin tha thii th positio o greates prehensil forc(Fig 12 bottom) Th mid-positio fo radiao ulna flexio appear t b suc tha thmetacarpophalangea join cente o digi IIlie i th extende sagitta plan o th wris(Fig 11)Typically th conformatio o finger anthum i simila t tha show fo palma prehensio (Fig 13) th finger bein mor anmor flexe fro inde t littl finger Th relation betwee thumb palm an finger arsuc a t permi gras o a 1.75-in cylindecrossin th pal a abou 4 deg t thradioulna axis Bunnel (4) consider thi "aancestra positio read fo graspin limbsweapons o othe creatures. Fig 11 Th restin han patterncommo object use ieveryda life thre typewer selecte fro amonthos originall classifie bSchlesinge (10). These appearin i Figur 13 arpalmar tip an latera prehension respectively Thfrequenc wit whic eac othes type occurre i thinvestigatio cite i give iTabl 6 Whil th relativpercentage diffe i th twtype o action th orde ofrequenc wit whic thprehensio pattern occurrei th same.MECHANICAL-ANATOMICA BASI oPREHENSIO PATTERNI i convenien t analyz digita mechanici term o flexion-extensio variation i thdigits thum postures an variation i thradioulna axisINDIVIDUATIO O DIGITA FLEXION-EXTENSIOInsertio o flexo an extenso muscl system int severa majo segment alon thproximal-dista axi provide a variet oflexion-extensio pattern i th digits IFigur 7 th essentia component ar showschematicall fo digit I an III Wit thesattachments fixatio carpa an metacarpasegment b cocontractio o flexo an extenso carp muscle provide a fir bas foindependen movement an fixation thphalangea segments Individua flexion o thsecon an termina phalange ste froseparat flexo muscl groups Suc flexogroups inserte distally ca als caus complet cylindrical-gras prehensio b "rollinup th han (Fig 13) Th counterbalancindigita extenso insert int th tw mos dista phalange and o contraction rigidl extend th entir finger Coordinate actiobetwee extenso an flexo groups howeverpermit fixe intermediat position o eacsegmen o th systemTw commo posture o thi syste mab pictured I palma prehensio (Fig 13)th carpa an metacarpa segment commonlfi th wris i moderat extension whil thdigita configuration mostl metacarpophalangea flexio couple wit onl sligh phalangea flexion indicate actio o th lonflexors strongl modifie b th lumbricalan interossei whic ar i positio no onlt contribut t th metacarpophalangeaflexio bu als t maintai th phalangeaTabl 6 FREQUENC o PREHENSIO PATTERN3 o palma prehensio i bot activitie account fo adoptio o thi patter i th desigo moder artificia hand (pag 86) trols A wil b see late (pag 78) succonsideration la dow th principa requirement an limitin factor i th desig oreasonabl successfu han substitutes Wheni th norma hand an functiona featureeithe mechanica o sensory-motor i impaired manipulativ characteristic ar reduce correspondingly I th ar amputeehan structura element hav bee wholllost an th mos delicat neuromusculafeatures thos i th han itself hav beedestroyed Althoug th los bon an joinmechanis ca b simulated adequat replacemen o th contro syste defie preseningenuity Lackin contro comparabl t thai th natura hand present-da artificiahand ar necessaril limite i th mechanica detail tha ca b utilized whic accountfo th fac tha th regai i functio currentl possibl i han prosthese fall fashor o duplicatin th natura mechanism. ACKNOWLEDGMENTh anatomica drawing whic accompanthi articl ar th wor o Joh Cassonemedica illustrato a th Universit o California Lo AngelesLITERATUR CITE1 Barnes R M. Motion and time study, Wiley NeYork 19372 Best C H. an N B Taylor Physiological basis o medical practice, William an Wilkins Baltimore 1937 p 12563 Bes an Taylor op. cit., p 14184 Bunnell Sterling Surgery o the hand, LippincottPhiladelphia 19445 Cox J W. Manual skill, Cambridg UniversitPress 19346 Dempster W T. an J C Finerty Relative ac­tivity of wrist moving muscles in static support of the wrist joint; a electromyographic study, AmJ Physiol. 150:59 (1947)7 Fick Rudolf Handbuch der Anatomic un Mechanik der Gelenke, Dritte Teil G Fischer Jena 19118 Inman Vern T. an H J Ralston The mechanics o voluntary muscle, Chapte 1 Klopste anWilson' Human limbs and their substitutes, McGraw-Hill Ne York 19549 Keller A D. C L Taylor an V Zahm Studies to determine the functional requirements for hand and arm prosthesis, Departmen o EngineeringUniversit o Californi a Lo Angeles 194710 Schlesinger G. Der mechanische Aufbau der kunst-lichen Glieder i Ersatzglieder und Arbeitshilfen, Springer Berlin 191911 Stetson R an J A McDill Mechanism odifferent types o movement, Psych Mono.32(3) 1 (1923)12 Taylor Crai L. The biomechanics o the normal and o the amputated upper extremity, Chapte 7 i Klopste an Wilson' Human limbs and their substitutes, McGraw-Hill Ne York 195413 Tiffin Joseph Industrial psychology, Prentice-HallNe York 194714 Universit o Californi (Berkeley) Prostheti Device Researc Project Subcontractor' FinaRepor t th Committe o Artificia LimbsNationa Researc Council Fundamental studies of human locomotion and other information relating t design o artificial limbs, 1947 Vol II TAYLO AN SCHWARarrange i tw rows thos i th mor proximaro articulatin wit radiu an ulna Betwee th tw i th intercarpa articulationTh bon conformatio an ligamentou attachment ar suc a preven bot lateraan dorsal-vola translation bu t allo participatio i th majo wris motion (Fig 2)I eac o th digits th anatomica desigi essentiall th same wit exception i ththumb Metacarpal I throug V articulats closel wit th adjacen carpa bone o thdista ro that althoug the ar capabl osom flexio an extension independenc omotio i ver limited Th metacarpa shaftar arche t for th palm an th distaend ar almos hemispherica t receiv thconcav curvatur o th proxima end o thfirs phalangesTh metacarpophalangea join exhibit a patter see als i th interphalangea jointsA show schematicall i Figur 3 th virtua cente o rotatio lie approximatel ath cente o curvatur o th dista en o thproxima member Th latera aspect o thjoin surface ar narrowe an closel bounwit ligaments s tha latera rotatio ismal i th metacarpophalangea joint anlackin entirel i th phalangea articulations Hence th latte ar typica hingjoints Th thum differ fro th othe digitfirs i tha th secon phalan i missin andsecond i tha ther i greate mobilit i thcarpometacarpa articulationMUSCLE AN TENDONMos o th muscle o han an wrisFig 3Sectio throug radius lunate capitate an th bon structuro digi III showin virtua center o rotatio o eac segmen upo thnex mor proxima one Whe th fis clenched th prominenc o thknuckle i forme b th hea o th mor proxima membe o eac articulation Fo nomenclature se Tabl 1(Tabl 2 li i th forear and narrowinint tendons travers th wris t reac insertion i th bon o ligamentou component o th hand Generally th flexor(Fig 4 aris fro th media epicondyl oth humerus o fro adjacen an vola aspect o th radiu an ulna an the coursdow th insid o th forearm The are therefore ipar supinator o th forear(Fig.5).Th extensor (Fig.6o wris an digit originatfro th latera epicondylan part o th ulna pasdow th dorsa sid o thforearm an thu assis ipronation Th thum sharei th genera flexor-extensoscheme bu it extensor anabductor originat fro midan dista part o radiu anulna Fig 7 Th anatom o prehension Schemati sectionthroug digit I an II sho essentia relation o muscle anbones Th letter L indicat thpresenc o ligamentou guidewhic channe clos t th wristh tendon o muscle originatin i th forearm Guid linX— indicate relativ positioo carpa base o thum an fingers Fo res o nomenclature seTable 1 an 2 Fro Taylo (12). FIXE HAN ADAPTATIONI thrustin o strikin action an th liketh han ma assum fixe an rigi posturewhil functionin wit th ar i supportThes represen nonspecialize function iwhic th han serve merel a adapte"en o th arm. Th variou form includth flat-of-hand th clenche fist th knucklan digita suppor postures an s onWRIS MECHANICTh wris joint compose o th radiocarpaan intercarpa articulation (Fig 1) ha aelliptica rotatio fiel wit th majo axi ith dorsal-vola excursion th mino i thulnar-radial N significan torsio occursBunnel (4) give th angula excursion abouth radiocarpa an intercarpa articulatio ashow i Tabl 4Th rotatio withi th carpa bone durinthes movement i to complicate fo brietreatment No onl d th rotation occua severa articulatin surfaces bu th virtuaaxe o rotatio li dista t th contac surface owin t glidin motion i th convexconcav structur o th joints Idealizatio oth motion int thos o a simpl lever rotatin abou a fixe center a implie i diagram suc a Figur 2 ca b justifie onla a convenien approximationTh muscle traversin th wris includthos insertin int th carpu an metacarpuan thos mediatin flexio an extensio oFig 8 Vola intrinsi muscle o th hand Fonomenclature se Tabl 2 TAYLO AN SCHWARextension I ti prehension th actio omuscle upo carpaan metacarpa bonei similar bu distribute flexio al phalangea segment indicate predominanflexo activityTHUM VERSATILITPATTERNTh versatilit o ththum lies first thvariet o it flexionextensio pattern andsecond i th adjustable rotator plan iwhic flexion-extensioca tak place Thfirs o thes i directlanalogou t th digitasyste fo th othefou fingers i tha foan give metacarpapositio ther ar numerou possibl position o th phalangesTh secon effec idu t th relativmobilit o th carpometacarpa joint whicallow th thum t ac i an plan necessar t oppos th digits Th principa opposition ar semidirect a see i palmartip an spherica prehensions Actually ithes case th plan o th thum actio iincline 4 t 6 deg t th palma plane Ilatera prehension th plan i approximatelparalle t th palma planeVARIATION I TH RADIOULNA AXI O THHANA thir principa mod o variatio concerncross-han alignments Thu th metacarpophalangea joint ma b draw int line anwit abducte thum a flat-han positio iassumed A th othe extreme th han iFig 12 Effec o forearm-han angl upo wris flexio an extensio forcean upo prehensio forces Above relationshi betwee forearm-han angl anmaximu force o wris flexio an extensio measure a th carpometacarpajoint Heav lines flexio (vola flexion) ligh lines extensio (dorsa flexion)Soli lines averages dotte lines standar deviations Unpublishe data UCLA1 mal subjects Below relationshi betwee forearm-han angl an maximuprehensio forc measure betwee thum an opposin inde an middl fingergraspin a 1/2-inc block Righ hand eigh norma mal subjects Soli line average dotte lines standar deviation Fro a U repor (14). cuppe fo spherica prehensio (Fig 13 ath opponen muscle o thum an littlfinger aide b othe adductor an flexorsac t pul thes digit towar eac otherSimila alignmen occur whe a fis madeHAN MOVEMENTTh larg numbe o muscle an joint oth han obviousl provide th equipmen fonumerou an varie pattern o movementNo s evident bu equall importan i determinin complexit an dexterit o motionar th larg area o th cerebra corte giveove t th coordinatio o motio an sensatio i th hand Thus i th moto corte thare devote t th hand approximatel tresse an upholstere furnitur ar quilteo otherwis fastene t preven slippag oth fillerI th hand th vola ski i tie dow bwhit fibrilla tissu connectin th sheath oth flexo tendon t th dee laye o thdermi alon th latera an lowe edge o thpalma fascia Th fold therefor var witth relativ lengtho th metacarpabone an wit thmutua relation oth sheath o thtendon an thedg o th palmafasciaTh sulci o furrows ar emphasizebecaus th subcutaneou fa i angive are i restricte t th interva betwee th linealon whic th skii tie down Thupressur upo anindividua monticulu canno displac th underlyinsof tissu beyonth boundarie establishe b thfibrilla connectionsTh relativ siz oan particula eminenc i a indicatio o th siz oth muscl involvean o it relativ developmenthroug usage witth exceptio thath siz o th hypothena eminencdepend i par upoth prominenc oth pisiformFig 5 Forear desig arelate t han mobilityB virtu o thi arrangement th han ca b rotate throug 18 deg.pal u t pal downwit th elbo flexed Witth ar full extendedparticipatio o shouldean elbo allow th hant b rotate throug almos 36 deg. pal u tpal up U ulna R radiusP pronation S supinationTH DORSA INTEGUMENUnlik th vola surface th dorsa sid oth han i covere wit thin soft pliablski an equall mobil subcutaneou tissuebot capabl o yieldin easil unde tensionBecaus i flexio th finger an i makina fis th coverin o th bac o han musb abl t stretc fro wris t fingernails thdorsa ski i arrange i numerou minutredundancies which i th fiat-of-hand armanifes i th typica transvers wrinklesparticularl ove th phalangea articulationsSpecia adaptation i th dorsa ski o ththum accommodat th distinctiv rotationa planes o tha digi abou it carpometacarpa articulation I th normal healthhand th degre o redundanc i an giveare i jus suc tha al wrinkle ar dispatche whe th fis clenched Swellin ian area dorsa o volar inhibit flexionextensio o th par affectedNERV AN BLOO SUPPLThre principa nerve serv th muscle oth han (Fig 9) Nerv supply i indicatedexcep fo mino variation an exceptions iTabl 3 Eac o thes majo nerv trunkdiverge int countles smalle branche endini th papilla o th palma pad an dorsaskin an th whol neuromuscula syste is coordinate i th brai tha moto respons t stimul i ordinaril subconsciou anreflex Thu a objec slippin fro th grasi automaticall grippe mor firmly bu nos firml a t damag th han itself Noxioustimul ar rejecte automatically a whe Fig 10 Bloo suppl t th uppe extremity A above media vie o th elbow A bottom dorsa vein oth hand B superficia vein o th arm C arterie o th arma Fic (7)' Th palmari longus absen abou 1 percen o cases i omitte fro th summe Fic force o volaflexion. c fro measurement o maximu force norma t th hand applie a th metacarpophalangeajoint o 1 youn male a th Universit o Californi a Lo Angele (unpublishe data) zer deg t th 90-deg an the t th 180deg positions Th magnitud o th actiopotential associate wit eac o thes rolei approximatel i th orde 4:2:1SLO AN RAPI MOVEMENTI movement rangin fro slo t rapidwit contro o direction intensity an ratether i alway som degre o cocontractiot ensur contro an t permi change iforc an velocity A ne forc i th musclecause motion I thi categor i a lon liso activities suc a writing sewing tyinknots an pressin th key o musica instruments Include ar mos action involvindifferentia o integrate motion o th digitsI i o interes t not tha th ful capacitfo thes motion i seldo develope b thaverag individual Wit intensiv practicesignifican increase i th facilit o manipulation eve wit simpl operations ma bachieved althoug individual diffe markedli th amoun o trainin gain Th averagindividua ha laten potentia fo developmeno skill a show b th feat o manipulatiooccasionall evidenced Knot-tying cigaretterolling an simila comple manipulationma b performe wit on hand a oftedemonstrate b accomplishe unilatera aramputees Accordin t Tiffi (13), dexteritdifference ar correlate neithe wit mentaabilit no wit han shap o dimensions buCo (5 point ou tha the hav a importan effec o th performanc o industriaassembl operationsBALLISTI MOVEMENTBallisti movement ar rapi motionsusuall repetitive i whic activ musculacontraction begi th movement givin momentu t th member bu ceas o diministhei activit throughou th latte par o thmotion I i unlikel that o themselves thfinger utiliz thi typ o motio t anmarke degree Barne (/ review evidenctha i repetitiv wor finge motion armor fatiguing les accurate an slowe thaar motion o th forearm Consequently irepetitiv finge activitie i whic ther i a ballisti element suc a piano-playing typingan operatin a telegrap key wris an elbomotion predominat whil th finger merelpositio themselve t strik th prope keyHAN DYNAMICTh han thei actions an contractil force ar give i Tabl 5 take froFic (7) Th tota Fic forc equal th summate force o th individua muscle participatin i th action Fo eac muscl th forci equa t th physiologica cros sectio (i.e., th tota cros sectio o th muscl take norma t it fibers multiplie b th forc factoo 1 kg pe sq cm. estimate b Fic thol fo huma muscle Thes force ar produce alon th axi o th muscl an ittendon bu sinc th effectiv momen arupo an o th wris o han joint i smallth measured isometri force ar onl abou1 percen o th tota forceAmon th wris actions tota force anmeasure isometri force assum th samran order Th variation, wit wris angleo bot flexor-extenso force i th wris ano prehensil force i th han i o practicaimportanc a wel a theoretica interest Thprehensil forc reache a maximu a a wrisangl o abou 14 deg (Fig 12 bottom) Thii approximatel th angl a whic th maximu force o wris flexio an extensio occu(Fig 12 top) I i commo experienc thath wris assume thi angl whe ver stronprehensio i required Th lessene force awris angle towar th extrem position oflexio o extensio ar attributabl t thwell-know forc reduction i th isometrilength-tensio curv a a muscl i markedlstretche o slackene (8). Th exceptio tthi rule see i th augmente forc o flexio a wris angl 8 deg. apparentl meantha thi degre o wris extensio doe nostretc th flexo muscle beyon thei forcmaximumCONCLUSIOThis briefly constitute th anatomicabasi o han mechanics fro whic i cab see tha norma han functio i th resul no onl o a highl comple an versatilstructura arrangemen bu als o a equallelaborat an full automati syste o con Fig 1 Bone an articulation o thhand includin th interosseu muscles Avola view B dorsa view Fo nomenclture se Table 1 an 2Fig 2 Angle o rotatio abou th wrist A extensio (o dorsiflexion) B flexio (o vola flexion) C radiaflexion D ulna flexion Fig 6 Extensor o wris an digits Fo nomenclature se Tabl 2th finger ar withdraw fro a objec uncomfortabl hotTh wris an han receiv thei bloo suppl fro th radia an ulna arteries whicru paralle wit th bone concerned enteth han throug th flexo "tunnel, anthe joi throug a double-arc syste (Fig10) Smal branche fro th arche serv thdigits Th majo venou syste compriseth basili an cephali vein superficiallplace o th vola surfac o th forearmTH RESTIN HAN PATTERTh restin han assume a characteristiposture a featur easil see whe th hanhang loosel a th side Th restin wristake a mid-positio i which wit respec tth extende forear axis i dorsiflexe3 deg (Fig 11) I i wort notin tha thii th positio o greates prehensil forc(Fig 12 bottom) Th mid-positio fo radiao ulna flexio appear t b suc tha thmetacarpophalangea join cente o digi IIlie i th extende sagitta plan o th wris(Fig 11)Typically th conformatio o finger anthum i simila t tha show fo palma prehensio (Fig 13) th finger bein mor anmor flexe fro inde t littl finger Th relation betwee thumb palm an finger arsuc a t permi gras o a 1.75-in cylindecrossin th pal a abou 4 deg t thradioulna axis Bunnel (4) consider thi "aancestra positio read fo graspin limbsweapons o othe creatures. Fig 11 Th restin han patterncommo object use ieveryda life thre typewer selecte fro amonthos originall classifie bSchlesinge (10). These appearin i Figur 13 arpalmar tip an latera prehension respectively Thfrequenc wit whic eac othes type occurre i thinvestigatio cite i give iTabl 6 Whil th relativpercentage diffe i th twtype o action th orde ofrequenc wit whic thprehensio pattern occurrei th same.MECHANICAL-ANATOMICA BASI oPREHENSIO PATTERNI i convenien t analyz digita mechanici term o flexion-extensio variation i thdigits thum postures an variation i thradioulna axisINDIVIDUATIO O DIGITA FLEXION-EXTENSIOInsertio o flexo an extenso muscl system int severa majo segment alon thproximal-dista axi provide a variet oflexion-extensio pattern i th digits IFigur 7 th essentia component ar showschematicall fo digit I an III Wit thesattachments fixatio carpa an metacarpasegment b cocontractio o flexo an extenso carp muscle provide a fir bas foindependen movement an fixation thphalangea segments Individua flexion o thsecon an termina phalange ste froseparat flexo muscl groups Suc flexogroups inserte distally ca als caus complet cylindrical-gras prehensio b "rollinup th han (Fig 13) Th counterbalancindigita extenso insert int th tw mos dista phalange and o contraction rigidl extend th entir finger Coordinate actiobetwee extenso an flexo groups howeverpermit fixe intermediat position o eacsegmen o th systemTw commo posture o thi syste mab pictured I palma prehensio (Fig 13)th carpa an metacarpa segment commonlfi th wris i moderat extension whil thdigita configuration mostl metacarpophalangea flexio couple wit onl sligh phalangea flexion indicate actio o th lonflexors strongl modifie b th lumbricalan interossei whic ar i positio no onlt contribut t th metacarpophalangeaflexio bu als t maintai th phalangeaTabl 6 FREQUENC o PREHENSIO PATTERN3 o palma prehensio i bot activitie account fo adoptio o thi patter i th desigo moder artificia hand (pag 86) trols A wil b see late (pag 78) succonsideration la dow th principa requirement an limitin factor i th desig oreasonabl successfu han substitutes Wheni th norma hand an functiona featureeithe mechanica o sensory-motor i impaired manipulativ characteristic ar reduce correspondingly I th ar amputeehan structura element hav bee wholllost an th mos delicat neuromusculafeatures thos i th han itself hav beedestroyed Althoug th los bon an joinmechanis ca b simulated adequat replacemen o th contro syste defie preseningenuity Lackin contro comparabl t thai th natura hand present-da artificiahand ar necessaril limite i th mechanica detail tha ca b utilized whic accountfo th fac tha th regai i functio currentl possibl i han prosthese fall fashor o duplicatin th natura mechanism. ACKNOWLEDGMENTh anatomica drawing whic accompanthi articl ar th wor o Joh Cassonemedica illustrato a th Universit o California Lo AngelesLITERATUR CITE1 Barnes R M. Motion and time study, Wiley NeYork 19372 Best C H. an N B Taylor Physiological basis o medical practice, William an Wilkins Baltimore 1937 p 12563 Bes an Taylor op. cit., p 14184 Bunnell Sterling Surgery o the hand, LippincottPhiladelphia 19445 Cox J W. Manual skill, Cambridg UniversitPress 19346 Dempster W T. an J C Finerty Relative ac­tivity of wrist moving muscles in static support of the wrist joint; a electromyographic study, AmJ Physiol. 150:59 (1947)7 Fick Rudolf Handbuch der Anatomic un Mechanik der Gelenke, Dritte Teil G Fischer Jena 19118 Inman Vern T. an H J Ralston The mechanics o voluntary muscle, Chapte 1 Klopste anWilson' Human limbs and their substitutes, McGraw-Hill Ne York 19549 Keller A D. C L Taylor an V Zahm Studies to determine the functional requirements for hand and arm prosthesis, Departmen o EngineeringUniversit o Californi a Lo Angeles 194710 Schlesinger G. Der mechanische Aufbau der kunst-lichen Glieder i Ersatzglieder und Arbeitshilfen, Springer Berlin 191911 Stetson R an J A McDill Mechanism odifferent types o movement, Psych Mono.32(3) 1 (1923)12 Taylor Crai L. The biomechanics o the normal and o the amputated upper extremity, Chapte 7 i Klopste an Wilson' Human limbs and their substitutes, McGraw-Hill Ne York 195413 Tiffin Joseph Industrial psychology, Prentice-HallNe York 194714 Universit o Californi (Berkeley) Prostheti Device Researc Project Subcontractor' FinaRepor t th Committe o Artificia LimbsNationa Researc Council Fundamental studies of human locomotion and other information relating t design o artificial limbs, 1947 Vol II