and that excessive pronation is one major cause of foot and leg problems of runners. The treatment modahties used on these runners are shown

Transcription

1 Foot orthotic devices to modify selected spects of lower extremity mechnics* B. T. BATES,&dgger; Ph.D., L. R. OSTERNIG, Ph.D., B. MASON, M.S., AND L. S. JAMES, M.D., Eugene, Oregon From the Biomechnics-Sports Medicine Lbortory, University of Oregon, nd the Orthopedic nd Frcture Clinic of Eugene, Eugene, Oregon ABSTRACT Fxcessive foot prontion hs been speculted to be cuse of leg nd foot problems mong runners. Foot orthotic devices re often used to modify this condition. Exmintion of the records of 180 ptients treted for vrious running injuries showed tht 83 individuls (46%) were prescribed orthotic devices nd tht 65 of these runners (8%) were ble to return to their previous running progrms. In order to ssess further the effects of this type of orthotic device, six runners were selected from this group nd filmed using two cmers (200 frmes/sec) under three conditions: (1) brefoot, (2) regulr shoe, nd (3) regulr shoe plus orthotic device. Both the period of prontion nd the mount of mximum prontion were significntly reduced by using the foot orthotic device. The dt support the conclusion tht foot orthotic devices cn be successfully used to modify selected spects of lower extremity mechnics during the support phse of running. Although number of ntomicl fctors must be considered m the dignosis nd evlution of lower extremity problems encountered by runners, it seems tht mny of these problems re relted, either directly or indirectly, to foot structure nd function during the support phse of the ctivity. 1-3 In recent clinicl study, Jmes et l. identified some common problems experienced by 180 runners (Tble 1). The dt lso indicted tht 58% of the subjects exmined exhibited pronted feet in the sttic weightbering position. The mjor injury nlysis is shown in Tble 2. Additionl observtions indicted tht the types of injuries ssocited with pronted * Reserch ws supported by grnt from Northwest Are Foundtion, St Pul, Minnesot z- Address correspondence to: B T. Btes, Ph D, Biomechmcs/ Sports Medicine Lbortory, Deprtment of Physicl Eduction, Umversity of Oregon, Eugene, Oregon feet were, m fct, similr to those found in the overll injury nlysis. This would, however, suggest tht there is complex mterction between running injuries nd ntomicl fctors nd tht excessive prontion is one mjor cuse of foot nd leg problems of runners. The tretment modhties used on these runners re shown m Tble 3. Eighty-three individuls (46%) wore prescribed orthotic devices s form of tretment nd 65 of these runners (8%) were ble to return to their previous running progrms. An orthotic pplince or device is type of &dquo;shim&dquo; plced between the foot nd shoe to modify foot position (not only prontion) during the support phse of running. Foot orthotics cn be mde either of soft flexible mteril or more rigid plstic mtenl. The purpose of this study ws to ssess further the effects of foot orthotic devices on selected spects of foot nd leg running mechnics by exmining smll group of joggers-runners selected from the previously discussed clinicl study. All subjects chosen were from the group clssified s &dquo;prontors&dquo; nd hd been successfully treted with orthotic pplinces. 1 METHODS Six joggers-runners (running 3 to dys per week; 10 to 110 km per week) who hd used prescribed rigid foot orthotic devices for t lest 1 yer served s subjects for this study. All subjects hd history of vrious difficulties sufficiently severe to cuse them to seek medicl ttention. Clinicl evlution of ech condition indicted tht n orthotic device might be helpful in overcoming the ptient s problem(s). Foot csts were mde nd the pproprite orthotic device ws constructed for ech individul. All six subjects were eventully ble to return to their norml jogging-running schedule. While running on tredmill subjects were filmed usmg two high-speed super 8-mm cmers (Visul Instrumenttion Corportion, Model SP-1) operting t 198 to 205 frmes per sec. Films were obtined of foot plcement from the rer nd of 338

2 - TABLE 1 The most common problems expenenced m study group of runners &dquo; From Jmes et l In group of 180 runners, 164 (1 %) hd lower extremity problems TABLE 2 Mjor injury nlysis of study group of runners From Jmes et l In study of 180 runners, 2 (58%) ptients exhibited pronted feet m the sttic weightbenng position. TABLE 3 Tretment modlities used for runners m study group The films were evluted using stop ction projector m conjunction with Numonics Grphics Clcultor interfced to Tektronix 4051 grphic system. All rw dt were treted by usmg cubic spline dt fittmg progrm prior to computtion of finl vlues. Dt nlysis consisted of the evlution of smgle right footfll for ll subjects for the three previously described conditions. Dt nlysis consisted of reltive temporl evlution of selected events throughout the support phse, kinemtic nlysis of selected body prts nd joint functions, nd grphic displys of the functionl reltionships between selected prmeters. The dt for the three test conditions were nlyzed by using one-wy nlysis of vrince design with repeted mesures nd plnned comprisons conducted between the three pirs of group mens for ech vrible, P < In ddition, ll dt were compred to previously obtmed results on group of symptomtic runners~ by usmg one-wy nlysis of vnnce design for independent groups. Plnned comprisons were conducted between the brefoot nd shoe conditions for ech group, the orthotic nd nonorthotic group, nd the brefoot nd shoe conditions, P < RESULTS AND DISCUSSION Men vlues descnbing the occurrence of selected events reltive to the beginning of the support phse re presented in Tble 5. Men vlues from previous study re lso given s well s significnt comprisons between selected events nd conditions. Compnsons between the events of mximum knee flexion, mximum prontion, nd ptell cross for ll conditions showed no significnt differences. This finding is in greement i TABLE 4 From Jmes et l. In group of 180 runners, 164 (1%) hd lower which necessitted tretment. extremity problems Terms nd defimtions used m nlyses of lower extremity function m runners lower limb movement from lterl view. Subjects were filmed under three conditions: (1) brefoot, (2) test shoe, nd (3) test shoe plus orthotic device. All runners wore the sme type of shoes (Nike Boston) for testing. The speed chosen for ech runner ws bsed upon individul running bility rther thn fixed speed due to the widely vried cpbilities of the individuls. Running speeds rnged from 2.82 m per sec (9:30 min per mile pce) to 4.4 m per sec (6 min per mile pce). Tredmill runmng ws chosen insted of overground runmng m order to control foot plcement nd obtin severl consecutive footflls with minimum mount of filming perspective error. To minimize differences tht might exist between tredmill nd overground running, ll subjects prticipted in supervised trining session before being filmed. Previous studies4-6 hve divided the support phse of running mto three subphses, i.e., seprted by the positions of heel strike, foot flt, nd heel-off nd toe-off. In previous study, six intermedite positions were identified bsed upon relted joint functions. Importnt terms ssocited with these positions re given nd defined in Tble

3 with previous results reported by Btes et ll It would pper tht these three events ll occurred t or ner the position when the center of grvity psses over the bse of support. When compring the experimentl conditions, significnt differences were observed for four events between the brefoot nd orthotic conditions. For ech of these events, the men vlue for the shoe condition ws observed to be n intermedite vlue. Prontion begn lter nd ended sooner with the use of the orthotic device. obtmed dt for In compnng these dt with previously norml or symptomtic runners, it should be noted tht for the events of begin prontion, end prontion, nd period of prontion, ll between group comprisons were significntly different except begin prontion nd the period of prontion between the brefoot conditions for both groups. The reltion- the occurrence of mximum ships of these events, mcluding prontion, re shown grphiclly in Figure 1. The dt suggest tht the use of the orthotic device cused djustments of the functionl mechnisms of the joint nd produced observed vlues in the orthotic group tht were similr to those previously observed in the norml group. The between group com- between the brefoot nd shoe conditions were ll prisons significnt. These dt support the premise tht simple shoe cn produce significnt chnges in the events used to define foot function. A finl observtion of some importnce ws the occurrence of mximum nkle dorsiflexion lter in the support phse s the result of wenng n orthotic device. It would seem tht the reonenttion of the heel llowed the body to move forwrd longer before the mximum dorsiflexion vlue ws reched nd the heel ws forced to rise from the running surfce. Tble 6 contins the men ngulr vlues describing the positioning of selected body prts. Significnt differences tht occurred between men vlues for vrious conditions re lso presented s well s men vlues from previous study. The use of the orthotic device resulted in significnt reduction in mximum prontion compred to the brefoot condition. In ddition, ll comprisons between the orthotic group nd the norml group were significnt, indicting tht the groups did differ m mximum prontion for ll conditions evluted. However, with the use of n orthotic device the injured group men vlue of mximum prontion (.0 ) ws pproximtely equl to tht of norml subjects wering only regulr shoe (.2 ) nd their injury problems were eventully resolved. The observed chnges in the vlues of mximum prontion were primrily the result of reorienttion of the heel reltive to the running surfce. The orienttion of the leg remined nerly constnt. It is importnt to note, however, tht increses in ~ upporc k ) Fig. 1. Comprisons between reltive periods of prontion for selected conditions. TABLE 5 Men vlues of selected events occurnng dunng the support phse of running&dquo; indicte stndrd devitions &dquo; All vlues re expressed s percentge of time from begmnmg of support phse. Numbers m prentheses b Dt for normls tken from Btes et l C Sigmficnt difference between brefoot nd shoe, P < ~ Significnt difference between brefoot nd orthotic, P < 0 I5. e No sigmficnt differences between these events ~ Significnt difference between shoe nd orthotic, P < &dquo; 340

4 TABLE 6 Comprisons of men ngulr vlues of selected body prts occurnng withm the support phse of running&dquo; rusu::nur vmes re ior ngm ieg, u vmes re expresse m egrees mumoers m premneses b Dt for normls tken from Btes et l C Sigmficnt difference between brefoot nd orthotic, P < d Sigmficnt difference between shoe nd orthotic, P < e Sigmficnt difference between brefoot nd shoe, P < micie sinr eviuons. running speed cn cuse increses in mximum prontion s result of chnges in leg orienttion. Exmintion of the dt on comprisons between the vlues of mximum nkle dorsiflexion indicted strong reltionship between this vrible nd prontion. All compnsons between the vrious conditions nd groups except one (shoe versus orthotic) showed significnt differences. Severl observtions re worth noting: (1) reductions in mximum prontion within ech group were lwys ccompnied by reductions in mximum nkle dorsiflexion; (2) the norml group hd greter nkle dorsiflexion, but lesser corresponding vlues for mximum prontion; nd (3) the brefoot condition vlues were lwys greter thn the shoe condition vlues. In ddition, there ws significnt difference between the orthotic nd norml groups on mximum knee flexion, with the orthotic group hving greter flexion. Explntions for this finding re specultive. The orthotic group my hve lcked nkle flexibility due to tight gstrocnemius musculture. In n ttempt to gin greter nkle dorsiflexion they shortened the gstrocnemius by dditionl knee flexion. This ws not sufficient, however, nd they my hve been forced to pronte more s n dditionl compensting mechnism. It is lso possible tht this group my hve pronted excessively to compenste for some other condition (tibi vrum, subtlr vrus, or forefoot supintion) nd no longer hd need to dorsiflex s much. In rehty, however, it ws observed tht the runners in the orthotic group s well s others in the clinicl study tht were clssified s prontors usully experienced combintion of two or more of these conditions. One finl observtion is tht the effect of slightly positive heel (bout 8 mm) reduced the period of prontion s well s the mount of mximum prontion nd mximum nkle dorsiflexion. About 5% of the men reduction in mximum nkle dorsiflexion resultmg from positive heel shoe ws directly ccounted for by the geometry of the two conditions. The ddition of n orthotic device further elevtes the heel but it lso reorients it. Figures 2 to 4 contin grphic displys of the functionl Fig. 2. Prontion-supintion reltionship for the support leg brefoot (....), with shoe (- - -), nd with orthotic device in shoe (-). f&dquo;s, Fig. 3. Comprison between prontion nd knee flexion of the support leg brefoot (...), with shoe (- - -), nd with orthotic device in shoe (-). 341

5 the injured runners modified their lower extremity mechnics in such wy tht the observed vlues were similr to those mesured on noninjured runners wering only simple shoe Mjor chnges were observed in both the mount nd period of prontion, nd these chnges seemed to llevite these runners problems. These findings imply tht functionl foot mechnics seem to be dependent upon the shpe, chrcteristics, nd fit of the mterils we plce between our feet nd the running surfce. Cre must be tken tht overmodifictions do not crete new problems. Elimintion of prontion requires tht the norml stresses of running be bsorbed by some other mechnism. Smce prontion is necessry functionl mechnism, only when it results in injury should ttempts be mde to modify it. Fig. 4. Comprison between prontion nd nkle flexion for the support leg brefoot (...), with shoe (- - -), nd with orthotic device in shoe (-). reltionships between selected prmeters obtined for single subject whose dt vlues re representtive of the men vlues. Figure 2 shows the reductions in mximum prontion tht resulted from shoe nd the shoe with the orthotic device. Exmintion of Figures 3 nd 4 shows similr reltionships for ll three conditions, with greter chnges hmng occurred between the brefoot condition nd the other two conditions. of the Another pnmry difference ws seen m the shiftmg curves to the left which ws the result of the reduction in prontion. The functionl mechmsms evluted m this study were different for the three conditions. The orthotic device used by REFERENCES 1 Jmes SL, Btes BT, Ostermg LR: Injuries to runners Am J Sports Med , Athletes Feet. Mountin View, CA. World Publictions, Schuster R. Custive fctors in foot nd leg problems in runners New York RRC Newsletter, summer Btes BT, Hven BH Effects of ftigue on the mechnicl chrcteristics of highly skilled femle runners In Biomechnics I V, edited by RC Nelson nd CA Morehouse Bltimore, University Prk Press, 194, pp Slocum DB, Jmes SL. Biomechmcs of running. JAMA , Inmn VT, Mnn RA Biomechnics of the foot nd nkle. In VT Inmn nd HL DuVries St. Surgery of the Foot, edited by Louis, CV Mosby Co, 193, pp 3-22 Btes BT, Osternig LR, Mson B, et l: Lower extremity function during the support phse of running In Biomechnics VI, edited by PE Asmussen nd K Jorgensen University Prk Press, 198, pp