AN IMPROVED LOWER LEG MUL TIBODY MODEL

Transcription

1 AN IMPROVED LOWER LEG MUL TIBODY MODEL HJ Cappon, AJ van den Koonenbeg, R Happee, JSHM Wsmans TNO automotve, Cash Safety Cente, the Nethelands ABSTRACT lnjues to the lowe extemtes ae among the most seous, non lfe theatenng njues occung nowadays In ode to nvestgate and pedct the occuence of njues, bofdelc eseach tools, lke mathematcal human body models ae needed The model of the lowe extemty, pesented hee, ncludes actve musculatue, smulatng bacng and factue at cetan njuy thesholds found n lteatue The model was valdated wth toe and heel mpact tests on human specmens and voluntees and geneally good ageement was found between expemental esults and smulatons Usng the model n a footwell ntuson smulaton llustates the pedcton of factue due to the contbuton of actve musculatue n tba loadng LOWER LIMB INJURIES account fo 37 % of the njues sustaned n ca cashes, whle 49 % of these njues nvolve the lowe leg, foot and ankle (Pattmoe, 99 ) Lestna (998) found that ankle and foot njues accounted fo about one thd of the lowe extemty njues Theefoe modellng of the human lowe extemty has become nceasngly mpotant fo studyng njues n ths body egon and pedcton of lowe extemty knematcs dung a cash Dung the past yeas, fnte element models have been developed by fo nstance Beaugonn (996), Tannous {996) and Wykowsk (998) Paenteau (996) and Hall (998) have developed multbody models of the lowe leg, focusng on the knematcs of the ankle jont n patcula The am of ths study was to develop a multbody model of the lowe extemty, to study the nfluence of footwell ntuson on foot, ankle and lowe leg knematcs and loads Footwell ntuson causes dosflexon and n o eveson of the foot Ths study focused on dosflexon n patcula Snce a ca occupant tends to bace befoe a fontal cash, the model also needed to addess actve musculatue An addtonal capablty pesented, s the falue occung n tba and ankle at specfed njuy thesholds In ode to valdate the model, the esponses to heel and toe pedulum mpacts, measued n expements wth cadave specmens and voluntees, wee compaed wth coespondng numecal smulatons Once the model was valdated t was used to smulate lowe leg esponses dung footwell ntuson /RCOBI Confeence Stges (Span), Septembe

2 METHODS THE BASIC MODEL Hall (998) developed a multbody model of the human lowe extemty, ncludng thgh, leg, ankle and foot The model was valdated only fo planta mpact, nvolvng small foot otatons The n and eveson movement has also been ncopoated, but not valdated The hp jont, femu and knee jont wee adopted fom a Hybd III database model and the pelvs was gdly suppoted The model of the leg conssted of 6 bodes, esultng n 7 gd stuctues, 6 jonts, lgaments and 2 muscles The jonts modelled wee the poxmal tbafbula jont, the ankle jont, the subtala jont, the tasal jont, the metatasal jont and the toe jont The gastocnemus and soleus muscle wee epesented by nonlnea spng elements, whle the most mpotant lgaments wee modelled wth two paallel stuctues a nonlnea spng element and a Maxwell element Thus the chaactestcs of the foot and ankle wee patly lumped n the jont chaactestcs and patly modelled as sepaate stuctues, that s lgaments and muscles The geomety of the lowe leg and foot was espesented by 3 ellpsods, as the contact aeas of the foot, beng the heel and the ball of the foot, can be adequately modelled wth ellpsods Fgue Model of the lowe extemty ncludng (actve) musculatue shown ght Femu Knee """d",, Rectus Femos Vast Soleus Gastocnemus Lgaments (Hall) The model used n ths study s a modfed veson of the model pesented by Hall Ths model extends to smulaton of dosflexon loadng as descbed below MUSCULATURE Dung bacng n fontal mpacts, the ca occupant pesses the foot aganst the bake pedal as was found n dvng smulatons pefomed by Owen (998) and Palmetz (998) The muscles manly nvolved n ths acton ae the knee extensos, the hp extensos and the ankle planta flexos The most mpotant knee extenso s the quadceps muscle n the thgh, whch s attached to the patella and extends to the anteo sde of the tba lt conssts of the ectus femos and thee vast The muscles manly nvolved n hps extenson ae the adducto magnus, the hamstngs* and the gluteus maxmus, whle ankle planta * Bceps femos, semtendnosus and semmembanosus 5 JRCOBJ Confeence Stges (Span), Septembe 999

3 flexon s nduced by the gastocnemus and the soleus muscle, both attached to the achlles tendon (Fgue ) The nseton pont of the muscles modelled wee deved fom Seeg ( 989) Actve musculatue I n MADYMO muscles can be mplemented accodng to the model of Hll (Wntes, 99) Ths muscle model allows the use to specfy actve and passve muscle chaactestcs The paametes fo the actve chaactestcs that wee used n ths model ae pesented n Appendx A, table The level of actvaton s dependent on the applcaton of the model Passve musculatue The passve behavou of the hp and thgh muscles was based on the standad functons povded n MADYMO, whle the behavou of the lowe leg muscles was adapted fom Halls model, showng stffe functons than MADYMO FRACTURE Two stuctues wthn the lowe leg model wee gven the possblty to beak the ankle jont and the tba In the ankle jont a dosflexon angle of 45 degees (Begeman, 99 and Pote, 997) o a lowe tba toque of 6 Nm (Pote, 997) had to be exceeded fo at least ms fo the jont to beak At falue the ankle jont was emoved, whch meant that the ankle was attached to the foot by lgaments only afte falue The tba faled when the axal compesson foce n the tba exceeded 78 kn fo lange than ms Fo ths pupose a tanslatonal jont was modelled n the tba, whch was locked untl falue Afte falue the tba was able to tanslate fo a few mllmetes, snce cush of catlage and factue of the tba mght nvolve some axal dsplacement of the ankle wth espect to the knee Yoganandan ( 996) poposed 8 kn fo falue, Ktagawa ( 998) found 73 kn fo pylon factues, 8 kn fo calcaneal factues and epoted 78 kn fo tbal factue found by Begeman Fgue 2 shows an example of falue on the compessve foce calculated n the tba Fgue 2 tba compesson foce wth and wthout falue 4 4X 35 3 z ;;; u "" wh taue Wl tou au t [ ( ( ( j ;,, 5 3 f Exceeds 78 kn fo ms ; ( tme [s] IRCOBI Confeence Stges (Span), Septembe

4 VALIDATION At the Tanspot Reseach Laboatoy (TRL) a set of toe and heel mpact expements wee pefomed (Mannng, 998) The test wee conducted usng 7 human post motem specmens and 5 voluntees The PMHS legs wee gdly suppoted at the knee, whle fo the voluntees the knee was flexed at 9 and suppot was povded behnd the knee The voluntee tests wee dvded n awae and unawae voluntee expements n ode to evaluate muscle tenson nfluence on the esponse The setup as used at TRL was modelled and used fo valdaton of the lowe leg pat of the model (Fgue 3) The feet wee ht wth an mpacto of 4 kg effectve mass The knee n the model was fxed, whch means that only the ankle planta flexos modelled wee of nfluence on the esponse Fgue 3 smulaton of the TRL tests (fxed knee) The followng output paametes wee compaed to the test esults foot otaton the angle between the tba and the foot (planta flexon s ), whch was measued n the voluntee expements by means of a gonomete and checked usng flm data analyss; 2 pendulum acceleaton; 3 tba compessve foces, measued wth a load cell mplemented n the tba of the post motem specmen (no data avalable fo voluntee tests); 4 tba fowad / eawad bendng toque, measued wth the tba load cell mentoned (no data avalable fo voluntee tests) The PMHS tests wee smulated usng passve muscles, thus assumng compaable tensle chaactestcs fo lvng and post motem muscle tssue Ths s a usual appoach, although some dffeence has been epoted (Ee et al, 998) The esponses of unawae voluntee tests wee compaed wth smulatons nvolvng passve musculatue, although the muscle actvty of unawae voluntees was not completely neglgble The awae voluntee expements wee compaed wth the smulatons nvolvng actve musculatue (Table ) usng a muscle actvaton level of 3 % 52 IRCOBI Confeence Stges (Span), Septembe 999

5 Table Matx of valdatons appled PMHS specmen Toe mpact 2 m/s Toe mpact 4 m/s Heel mpact 2 m/s Heel mpact 4 m/s Voluntee unawae (passve) X X X X X Voluntee awae (actve) X X RESULTS TOE IMPACT Manly the esults of the 4 m/s smulatons wll be shown n ths paagaph Addtonal fgues ae shown n appendx B The smulaton of the mpact at the ball of the foot (actve muscles) showed that the foot ntally dosflexes Planta flexon follows afte 6 ms, whch s less clea n the (awae) voluntee tests (Fgue 4) Ths phenomenon can be fully attbuted to the muscles that ae actvated 3 % thoughout the ente smulaton (actvaton statng at t=o s) Fgue 4 foot otaton, ball mpact at 4 m/s; actve muscles 5 model actve "* Voluntee awae tme [s] The foot otaton data of unawae voluntee tests, at 4 m/s ball mpact, showed vey lage vaatons (Appendx B) and wee not sutable fo valdaton puposes The smulaton at 2 m/s, on the othe hand, showed good esults (Fgue 5) The foces calculated n the tba ae geneally close to the measued values n the PMHS specmen (Fgue 6) The man dffeence s that the foce cuve n the specmen tests lasts longe than n the smulaton, whch can patly be explaned by the foot contact stffness used (see below) The toques n the tba calculated at toe mpact wee much too hgh (Fgue 7) lt was found that the appled otatonal dampng of the foot ankle complex, whch s lumped n the ankle jont, was the cause of ths dscepancy Deceasng the dampng caused lowe tba toques as can be seen n Fgue 7 Ths paamete was adopted fom the ognal model (Hall, 998) and seems to be chosen abtaly The dampng of the ankle appaently needs futhe study IRCOBI Confeence Stges (Span), Septembe

6 Fgue 5 foot otaton, ball mpact at 2 m/s; passve muscles 5 5 t f l model passve * 3 voluntees 2 5 tme [s] Fgu e 6 tba compessve foce, ball mpact at 4 m/s; passve muscles, j j ; /,oeij>ess ve O *=""""LL,,J 5 tme [s) The magntude of the calculated pendulum acceleatons wee found to be vey close to the expemental esults n all ball mpact smulatons, but the duaton of the acceleaton was geneally too shot A possble cause of ths shote duaton s that the ubbe shoe epesentaton, used n the expements, was not modelled The shoe was omtted n the smulaton, because the esponses wee found to be elatvely nsenstve to changes n dampng an stffness n the contact nteacton between foot and mpacto Only the tme ange of the tba foce and of the acceleaton peak nceased due to a deceasng foot stffness 54 IRCOBI Confeence Stges (Span), Septembe 999

7 Fgue 7 tba toque, ball mpact at 4 m/s; passve muscles \ "\ ] 2 3 \ j 4 5 /, j ; ;tt<= ";,/Yf( f*/ I * L pass ve lowe dampng specmen modal e model 6 5 tme [s] Fgue 8 pendulum acceleaton, ball mpact at 4 m/s; passve muscles 5 4 Q) j ; ; j 3 t 2 " modal p assve voluntees specm n *"" 3 ) IJll,"*""P ; ; \ ; \;/{ ll = ;; """" " " """" O 5 tme [s] Fgue 9 tba compessve foces, heel mpact at 2 m/s 8 6 Q) E 4 2 modal oassve le specme n Fol"* ;j,;; *" tme [s] IRCOBI Confeence Stges (Span), Septembe

8 HEEL IMPACT As the loadng path to the tba s much shote than fo the toe mpact, these esponses coesponded well wth the expemental data Fgue 9 shows the tba foce The othe esults of these smulatons can be found n appendx B APPLICATION Fnally the lowe leg model was used to evaluate the effect of muscle actvty on the esponse n case of footwell ntuson The pelvs was fxed, whle the ball of the foot of the model was placed on a plate, epesentng a bake pedal, wth an ntal angle of 6 degees The ntuson nvolved a pescbed otaton of 5 degees and a tanslaton of 4 mm occung n 24 ms The bake pedal could not be depessed, snce the nfluence on the loads n the tba and otatos of the foot, was found to be small (Rudd, 998) The nomal foce actng on the bake pedal was set to 8 N, as was appoxmately found by Owen (998) and Palmetz (998), whch means a muscle actvaton level of 3 % n ths model (shea foces on the pedal wee below 5 N) Fgue shows an example of an ntuson sequence wth pescbed footwell knematcs somewhat lage than mentoned above, only fo the sake of claty Fgue Footwell ntuson, 3 otaton and 8 mm dsplacement n 24 ms 65 ms, bacng 75 ms, ght afte factue lt was found that the factue n the tba occued due to the actvated muscles, as the tenson n the achlles tendon causes an addtonal ncease n the tba loadng Fgue pesents the tba compessve foce fo actve and passve muscle behavou The actve muscles cause the tba to beak, whle the tba stays ntact wth passve muscles In both smulatons the ankle beaks due to the lage tba toque, at 328 seconds n the actve smulaton and at 335 seconds n the passve smulaton 56 IRCOBI Confeence Stges (Span), Septembe 999

9 Fgue tba compessve foce dung footwell ntuson Actve and passve Q) u actve e passve, 3 2 F== tme [s] DISCUSSION A multbody model has been pesented, whch s capable of pedctng foot and ankle knematcs n a cash nvolvng footwell dsplacement and otaton The nfluence of actve musculatue on tba loads and lowe leg knematcs has been evaluated and factue has also been modelled The model was valdated wth expemental data nvolvng toe and heel mpacts on a PMHS specmen and 3 voluntees The otaton of the foot and the compessve loads n the tba wee pedcted vey well by the model and theefoe njuy pedcton based on these paametes s vey well possble The mayo mpovement of the cuent model wth espect to Halls model s that actve musculatue has been added Futhemoe the actve musculatue enables the use to smulate the effect of bacng dung a cash Pett ( 998) studed the effect of actve musculatue on a Hybd III dummy model and found sgnfcant changes n the esponse due to actve muscles, as was found hee Modellng of factue clealy showed that the chance of factue nceased wth nceasng muscle actvty, as t caused an nceasng tba compesson foce A lmtaton of modellng factue, s that pedcton of knematcs afte falue s not possble n ths case, due to the dependency on the modfcaton n the ntenal stuctue Futhemoe, pedcton of factue sequence s thus questonable as well Note that, as soon as an njuy theshold s exceeded, the knematc behavou of the model wthout factue, s questonable as well The valdaton and applcaton of the model only consdeed dosflexon and tanslaton of the foot, as ths s geneally occung du ng footwell ntuson I n ode to make the model moe wdely applcable, t s ecommended to valdate the model wth n and eveson mpact expements In the nea futue the leg model wll be ncluded n the human body model as pesented by Happee ( 998) IRCOBI Confeence Stges (Span), Septembe

10 CONCLUSIONS The model of the human lowe extemty pesented s able to pedct tba compessve foces and foot otaton dung planta mpact of the foot The tba toques seem to be oveestmated by the model, but deceasng the ankle jont dampng was found to mpove the toque consdeably The actve musculatue n the hps, thgh and leg shows the capablty of modellng bacng of the occupant n a cash Bacng dung mpact poved to ncease the load n the tba consdeably and showed that factues ae moe lkely to occu when bacng ACKNOWLEDGEMENTS The authos would lke to thank the Unvesty of Vgna fo povdng the ntal model, whch was patly developed n collaboaton wth TNO Futhemoe, specal thanks to Lucy Wheele and Glae Owen at Tanspot Reseach Laboatoy, fo povdng the expemental data Pat of ths study was fnanced by the Euopean ADRIA poject (PL9674) REFERENCES Begeman, PC, Pasad, P Human Ankle Impact Response n Dosflexon SAE has also been modelled The model was valdated wth 9238 (99) 2 Beaugonn, M, Haug, E, Cesa, D A Numecal Model of the Human Ankle/Foot unde Impact Loadng n Inveson and Eveson SAE (996) 3 Band, RA, Pedesen, DR, Fedech, JA The Senstvty of Muscle Foce Pedctons to Changes n Physologe CossSectonal Aea In Jounal of Bomechancs Vol 9 No 8 (986) pp Van Ee, CA, Chasse, AL, Myes, BS The Effect of Postmotem Tme and Feeze Stoage on the Mechancal Popetes of Skeletal Muscle SAE (998) 5 Hall, GW Bomechancal Chaactezaton and Multbody Modelng of the Human Lowe Extemty PhD Dssetaton, Unvesty of Vgna (998) 6 Hall, GW, Candall, JR, Plkey, WD, Thunnssen, JG Development of a dynamc multbody model to analyze human lowe extemty mpact esponse and njuy IRCOBI poceedngs 998 Happee, R, Hoofman, M, Koonenbeg, AJ van den, Mosnk, P, Wsmans, J A Mathematcal Human Body Model fo Fontal and Reawad Seated Automotve Impact Loadng SAE 9835 (998) 8 Ktagawa, Y, lchkawa, H, Pal, C, Kng, AI, Levne, RS Lowe Leg lnjues Caused by Dynamc Axal Loadng and Muscle Tensng ESV (998) 9 Lestna, DC, Kuhlmann, TP, Keats, TE, Alley, RM Mechansms of Factue n Ankle and Foot lnjues to Dves n Moto Vehcle Cashes SAE (992) Mannng, P, Owen, C, Robets, A, Oakley, C, Lowne, R, Wallace, A Dynamc Response and lnjuy Mechansm n the Human Foot and Ankle and an Analyss of Dummy Bofdelty ESV 9889 (998) Owen, C, Robets, A, Mannng, P, Lowne, R Postonng and Bacng of the Lowe Leg dung Emegency Bakng a Voluntee Study IRCOBI poceedngs IRCOBI Confeence Stges (Span), Septembe 999

11 2 Palmetz, C, Jakobsson, L, Kalsson, A Pedal Use and Foot Postonng dung Emegency Bakng IRCOBI poceedngs Paenteau, CS FootAnkle Jont Responses, Epdemology, Bomechancs and Mathematcal Modelng PhD Dssetaton, Chalmes Unvesty of Technology (996) 4 Pattmoe, D, Wad, E, Thomas, P, Badfod, M The Natue and Cause of Lowe Lmb lnjues n Ca Cashes SAE 929 (99 ) 5 Pett, Ph, Pote, L, Tosselle, X Rgd Body Model of the Hybd III Dummy Lowe Lmb lncludng Muscle Tenson unde Ca Cash Condtons IRCOBI poceedngs Pote, L Pett, Ph, Dömont, A Tosselle, X, Le Coz, J, Taee C, Lassau, J Dynamc Bomechancal Dosflexon Responses and Toleances of the Ankle Jont Complex SAE (997) 7 Rudd, RW, Seveka, EM, Candall, JR, Pellettee, J, Lynn, S, Kelle, J Lowe Extemty and Bake Pedal lnteacton n Fontal Collsons Compute Smulaton SAE (998) 8 Seeg, A, Avka, R Bomechancal Analyss of the Musculoskeletal Stuctue fo Medcne and Spots (989) 9 Tannous, RE, Bandak, FA, Tods, TG, Eppnge, RH A TheeDmensonal Fnte Element Model of the Human Ankle Development and Pelmnay Applcaton to Axal Impulsve Loadng SAE (996) 2 TNO CashSafety Reseach Cente Theoy Manual 3D and Uses Manual 3D of MADYMO veson 53 (997) 2 Wntes, JM, Stak, L Estmated Mechancal Popetes of Synegstc Muscles lnvolved n Movements of a Vaety of Human Jonts In Jounal of Bomechancs Vol 2 No 2 (988) pp Wntes, JM, Woo SLY Hllbased muscle models A systems engneeng pespectve In Multple Muscle Systems Bomechancs and Movement Oganzaton (99) pp Wykowsk, E, Snnhube, R, Appel, H Fnte Element Model of Human Lowe Extemtes n a Fontal Impact IRCOBI poceedngs Yoganandan, N, Pnta, FA, Boynton, M, Begeman, P, Pasad, P, Kuppa, SM, Mogan, RM, Eppnge, RH Dynamc Axal Toleance of the Human FootAnkle Complex SAE (996) IRCOBI Con/eence Stges (Span), Septembe

12 APPENDIX A Muscle paametes These values wee calculated accodng to Wntes (988), wth Vmax=5 x LO and Fmax=5 x PCSA (wth PCSA n m2) No actvaton and extaton tme constants wee found fo the Gluteus Maxmus and the Adducto Magnus These values wee coped fom the Hanstngs Values that ae not mentoned n the table have been set to MADYMO default (see MADYMO Uses Manual 3) Table Muscle paametes Muscle PCSA Ta Tn LO V max [cm2] [ms] [ms] [m] [m/s] Rectus Femos Vastus Lat Vastus lnt Vastus Med Gastoc Med Gastoc Lat Soleus Gluteus Maxmus Hanstngs Adducto Magnus abbevatons of table PCSA = Physologcal CossSectonal Aea; Ta = actvaton tme constant; Tn = exctaton tme constant; LO = est length of the muscle; Fmax=maxmum muscle foce; Vmax = maxmum contacton velocty; Pett (998) used values fo Vmax, whch dffeed up to one ode of magntude wth the ones pesented hee He also used dffeent values fo Fmax The esponses, howeve, calculated wth the values accodng to Pett, dffeed lttle fom the esponses calculated hee 5 IRCOBI Confeence Stges (Span), Septembe 999

13 APPENDIX B Ths appendx contans all emanng fgues of the valdaton of the model The fgues below contan pendulum acceleatons, foot otaton angles, tba ytoques and tba compessve foces Each set of fgues contans a heade wth the test condtons Actve musculatue, ball mpact at 2 m/s 5 " f,;,?f 5 j L m d I actve 2 =? ; == == = ==,2 ; 2 " 5 ; T t, 2 g c 2 ; F F O ""=""""tl(, tme [s] 5 tme[s] Passve musculatue, ball mpact at 2 m/s 6 == = == = ; ; 2 modal f ; ; ; ; pass ve ; T 4 ;;ET 8 ; )L) ) tme [s] Passve musculatue, heel mpact at 2 m/s ;, c, 6, 2 ; == = ==; t T 5 5 H,H l 85 Ilj; modeloassve lle specmen 5 tme [s] j 5 2 c «> 2 IRCOBI Confeence Stges (Span), Septembe 999 ll Oll 5 I * model oassvel specmen, L T "" tme[s] 5

14 Actve musculatue, ball mpact 4 m/s Passve musculatue, ball mpact 4 m/s 6,,; ; == == == 5 Q; 2 ; <"4 g 3 ; ; model acbve *" vo untee awae ;, 2 5 o O L 5"" o "" = o, tme[s] bme[s] Passve musculatue, heel mpact 4 m/s 6 ; ;==== modaloassv e specmen 5 4 I 3 a; l l f \ o ;;; ;H 5 tme [s) J [ ;== = ====; 6 modeljlass ve j spec en 4 ; 2 f g Q; soo 6 2, , l 4 > L ) t 25 3 ; 3 ; ; ; = = = = 2 5 o 5 Q 5 ] t t " 5 tme [s] j j mo deljlassve spec en l t tme [s], ; 5 2 IRCOBI Confeence Stges (Span), Septembe 999