Plantar Loading During Cutting While Wearing a Rigid Carbon Fiber Insert

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1 Journl of Athletic Trining 2014;49(2): doi: / Ó by the Ntionl Athletic Triners Assocition, Inc originl reserch Plntr Loding During Cutting While Wering Rigid Crbon Fiber Robin M. Queen, PhD* ; Alici N. Abbey, BS, ATC* ; Rvi Verm, BS*; Robert J. Butler, DPT, PhD ; Jmes A. Nunley, MD *Michel W. Krzyzewski Humn Performnce Lbortory, Duke University, Durhm, NC; Deprtment of Orthopedic Surgery nd Deprtment of Community nd Fmily Medicine, Duke University Medicl Center, Durhm, NC Context: Stress frctures re one of the most common injuries in sports, ccounting for pproximtely 10% of ll overuse injuries. Tretment of fifth mettrsl stress frctures involves both surgicl nd nonsurgicl interventions. Fifth mettrsl stress frctures re difficult to tret becuse of the risks of delyed union, nonunion, nd recurrent injuries. Most of these injuries occur during gility tsks, such s those performed in soccer, bsketbll, nd lcrosse. Objective: To exmine the effect of rigid crbon grphite footplte on plntr loding during 2 gility tsks. Design: Crossover study. Setting: Lbortory. Ptients or Other Prticipnts: A totl of 19 recretionl mle thletes with no history of lower extremity injury in the pst 6 months nd no previous mettrsl stress frctures were tested. Min Outcome Mesure(s): Seven 458 side-cut nd crossover-cut tsks were completed in shoe with or without fulllength rigid crbon plte. Testing order between the shoe conditions nd the 2 cutting tsks ws rndomized. Plntrloding dt were recorded using instrumented insoles. Pek pressure, mximum force, force-time integrl, nd contct re beneth the totl foot, the medil nd lterl midfoot, nd the medil, middle, nd lterl forefoot were nlyzed. A series of pired t tests ws used to exmine differences between the footwer conditions (crbon grphite footplte, shod) for both cutting tsks independently ( ¼.05). Results: During the side-cut tsk, the footplte incresed totl foot nd lterl midfoot pek pressures while decresing contct re nd lterl midfoot force-time integrl. During the crossover-cut tsk, the footplte incresed totl foot nd lterl midfoot pek pressure nd lterl forefoot force-time integrl while decresing totl nd lterl forefoot contct re. Conclusions: Although rigid crbon grphite footplte ltered some spects of the plntr- pressure profile during cutting in uninjured prticipnts, it ws ineffective in reducing plntr loding beneth the fifth mettrsl. Key Words: soccer, cross cutting, side cutting, plntr pressure, fifth mettrsl frcture, rigid crbon grphite footplte Key Points Fifth mettrsl stress frctures cn be difficult to tret becuse of the risks of delyed union, nonunion, nd recurrent injury. In combintion with custom orthotic nd foot brce, modifying footwer with the use of crbon grphic footplte hs been proposed to llow thletes to sfely return to sport while the stress frcture is heling. Plntr loding beneth the fifth mettrsl incresed in helthy prticipnts who wore crbon grphite footplte while performing gility tsks. Plntr loding with nd without the footplte should be studied in ptients with mettrsl frctures. While thletes compete in sports, the risk of injury depends upon the sport nd position being plyed. 1 Age, sex, competition level, bone density, nd shoe type re ll risk fctors for injuries relted to the foot nd nkle. 2 4 Stress frctures re one of the most common time-loss bony injuries in sports, ccounting for pproximtely 10% of ll overuse injuries. 5 Mettrsl stress frctures ccount for up to 25% of ll stress frctures in the foot. 4 In ddition to the previously mentioned risk fctors, other risk fctors pper to be ssocited with fifth mettrsl stress frctures, such s foot morphology, shoe design, nd thletic tsk. 4 The literture exmining foot type s risk fctor for fifth mettrsl stress frctures is inconclusive, with some studies indicting tht individuls with flt foot were t incresed risk for frcture 6 nd others indicting tht those with high rch foot were t incresed frcture risk. 7 Tretment of fifth mettrsl stress frctures involves both surgicl nd nonsurgicl interventions. Regrdless of tretment, however, fifth mettrsl stress frctures re difficult to tret 8 12 becuse delyed union, nonunion, nd recurrent injury re frequent complictions. 9,11,13 15 The role of sex in fifth mettrsl stress frctures is not well understood. However, of the 23 fifth mettrsl stress frctures studied by Porter et l, 3 17 occurred in men. Although differences in the incidence of injury between sexes hve limited reserch support, sex differences in plntrloding mgnitude nd incresed lterl foot loding in men hve been reported in multiple studies In ddition, investigtors 19 hve shown tht fifth mettrsl stress frctures re more common in sports such s soccer, bsketbll, nd lcrosse, which require cutting nd other gility tsks. Journl of Athletic Trining 0 //xinet/production//ttr/live_jobs/ttr-49-02/ttr /lyouts/ttr d Š 29 Jnury 2014 Š 4:49 pm Š Allen Press, Inc. Š Customer MS# Pge 1

2 Figure 1. A, The side cut. B, The crossover cut. The effects of side cuts, crossover cuts, nd forwrd ccelertion on plntr loding hve been exmined Queen et l, 20 Eils et l, 21 nd Wong et l 22 demonstrted tht 458 or 1808 side-cutting tsk (to either side) resulted in incresed plntr loding under the medil column of the foot. With the crossover cut, however, the increse in plntr loding shifted to the lterl forefoot. 20 This increse in plntr loding beneth the lterl column indictes the importnce of evluting crossover cuts when exmining potentil risk fctors for fifth mettrsl stress frctures. The conservtive mngement of fifth mettrsl stress frctures hs often resulted in delyed union or nonunion of these frctures, especilly in thletes. 9,11,13 15 A novel technique is showing success in the conservtive tretment of these frctures. Combining custom orthotic nd foot brce nd modifying footwer through the use of crbon grphite footplte llowed plyers to return to sport while the frctures were heling; no delyed unions or nonunions occurred. 23 Bsed on this work, the purpose of our study ws to quntify the effect of rigid crbon grphite footplte on plntr loding, s defined by contct re, mximum force, nd the loclized force-time integrl, during side cuts nd crossover cuts. We hypothesized tht rigid crbon grphite footplte would decrese plntr loding beneth the lterl spect of the foot during the cutting tsks nd, therefore, be beneficil in the conservtive tretment of stress frctures. METHODS A totl of 19 college-ged physiclly ctive mles (ge ¼ yers, height ¼ m, mss ¼ kg, body mss index ¼ ) volunteered for the study. They were physiclly ctive nd engged in sports tht require cutting-type mneuvers, such s soccer nd bsketbll, nd hd no history of lower extremity injury in the pst 6 months, foot or nkle surgery in the pst 3 yers, or previous mettrsl stress frctures. Physiclly ctive ws opertionlly defined s prticipting in physicl ctivity t lest 3 times per week for pproximtely 1 hour ech time. Ech volunteer red nd signed n informed consent tht hd been pproved by the medicl center institutionl review bord, which lso pproved the study. A Pedr-X in-shoe pressure mesurement system (Novel, St. Pul, MN) ws used to collect plntr-pressure dt. The insoles were plced bilterlly, nd plntr-pressure dt were smpled t 100 Hz vi Bluetooth technology. Prticipnts were fitted with pproprite-sized shoes, insoles, nd rigid crbon grphite footpltes for testing. The rigid crbon grphite footpltes were mnufctured by Dynflex nd re non-custom, full-length inserts. The Pedr-X insole ws plced between the foot nd either the crbon insert or the shoe, depending on the testing condition. All testing ws completed in the lbortory on stndrd flooring with prticipnts wering the Nike Air Pegsus (Nike, Inc, Beverton, OR), which is neutrl cushioning running shoe. These running shoes were used to stndrdize footwer equipment mong prticipnts nd to prevent them from slipping on the lbortory floor during the cutting tsks. Ech prticipnt ws sked to run t 75% of mximum speed nd then cut 458; the direction depended on whether the tsk ws side cut or crossover cut. We monitored pproch speed with set of photocells to ensure tht speed remined within 5% for ll trils t the time of collection for ech person in ech condition. The side-cut tsk 0 Volume 49 Number 2 April 2014 //xinet/production//ttr/live_jobs/ttr-49-02/ttr /lyouts/ttr d Š 29 Jnury 2014 Š 4:49 pm Š Allen Press, Inc. Š Customer MS# Pge 2

3 Figure 2. Representtion of the msks tht were used to divide the foot into 8 ntomicl regions in the Novel softwre (St Pul, MN) during dt reduction. consisted of left or right foot plnt, depending on the dominnt leg bsed on prticipnt comfort, followed by cut wy from the plnt leg t 458 (Figure 1A). The crossover cut ws performed by hving the prticipnt run forwrd long 10-m runwy nd plnt either the right foot or the left foot, depending on plnt-foot preference, nd then cut cross the leg t 458 (Figure 1B). The prticipnt pproched ech cut with t lest 4 steps before the cut nd 3 steps fter the cut. Ech person ws shown how to Figure 3. Chnges in regionl plntr pressure during the sidecutting tsk. Arrow indictes chnge in the vrible when the crbon fiber footplte ws worn in the shoe. perform the cutting tsks nd llowed to choose which foot to use to perform the mneuvers bsed on comfort. After completing the cutting tsks, the plnt leg ws isolted from ech mneuver for the pressure nlysis. Testing order ws rndomized for both footwer cutting nd condition to void ftigue nd lerning effects. Once the rndomiztion order for footwer condition nd tsk ws determined, ech prticipnt completed 7 cceptble trils for the given condition before moving on to the next condition. Therefore, if person ws rndomized to the crbon grphite footplte nd side-cut condition first, he ws sked to complete 7 trils in tht condition before moving to the other 3 testing conditions. The prticipnt ws given 30-second rest between trils nd 5-minute rest between testing conditions. For nlysis, the foot ws divided into 8 ntomicl regions (rerfoot, medil midfoot [MMF], lterl midfoot Journl of Athletic Trining 0 //xinet/production//ttr/live_jobs/ttr-49-02/ttr /lyouts/ttr d Š 29 Jnury 2014 Š 4:49 pm Š Allen Press, Inc. Š Customer MS# Pge 3

4 Tble 1. Pek Pressure During the Side-Cutting Tsk, kpa Totl foot , , Rerfoot , , Medil midfoot , , Lterl midfoot , , Medil forefoot , , Mid forefoot , , Lterl forefoot , , Hllux , , Lesser toes , , No [LMF], medil forefoot [MFF], middle forefoot [MidFF], lterl forefoot [LFF], hllux, nd lesser toes) using percentge msk in the Novel Multiproject-ip softwre 20,21,24 26 (Figure 2). The mximum force, force-time integrl, contct time, contct re, nd pek pressure were collected for the totl foot re nd ech ntomicl region. The results of the 7 trils were verged. Mximum force is the pek force in the region of interest throughout the entire stnce phse. Contct re is the percentge of n re of the insole tht ws ctivted during the stnce phse reltive to the entire contct re of the insole. Force-time integrl is the re under the force-time curve nd mesures both the mgnitude of lod on n re nd the durtion of the loding during the stnce phse. Mximum force ws normlized to ech person s body weight, nd contct re ws normlized to the entire insole contct re. 20 We used series of pired t tests (,.05) to determine if ny differences existed between footwer conditions for ny study vrible independently for the 2 tsks. The choice of pired t tests ws bsed on previous work 27 indicting differences in loding bsed on tsk (side cut versus cross cut) nd, therefore, this comprison ws not needed in our study. The question of interest ws not whether differences existed between the cutting tsks but specificlly wht the effect of the insert ws on plntr loding during these tsks independently. Although the Pedr- X mesurement system collects pressure dt from ll prts of the foot, we nlyzed the MMF, LMF, MFF, MidFF, nd LFF becuse our focus ws the lods under the lterl column of the foot (LMF nd LFF). Focusing on these regions of the foot decresed the need for sttisticl djustments due to multiple comprisons. RESULTS Side-Cut Tsk The totl foot pek pressure (P,.001) nd the LMF pek pressure (P ¼.017) were incresed by 54% nd 17%, respectively, with the rigid crbon grphite footplte (Tble 1). The force-time integrl (P,.001; Tble 2), totl foot contct re (P ¼.001), nd LMF contct re (P ¼.007; Tble 3) were decresed by 28%, 9%, nd 15%, respectively, with the use of the footplte (Figure 3). The chnges in mximum force in the vrious foot regions during the side-cut tsk cn be found in Tble 4. No differences existed between the footplte conditions for the remining regions of the foot. Crossover-Cut Tsk With the rigid crbon footplte, the totl foot pek pressure (P,.001; Tble 5), LMF pek pressure (P,.001), nd LFF force-time integrl (P ¼.016; Tble 6) incresed by 60%, 37%, nd 15%, respectively The totl foot contct re (P,.001) nd LFF contct re (P ¼.014; Tble 7) were decresed by 9.7% nd 4.8%, respectively, with the footplte (Figure 4). The chnges in mximum force in the vrious foot regions during the Tble 2. Force-Time Integrl During the Side-Cutting Tsk, ns No Men (Body Weight) 6 SD Men (Body Weight) 6 SD Totl foot , , Rerfoot , , Medil midfoot , , 5.47 Lterl midfoot , , Medil forefoot , , Mid forefoot , , Lterl forefoot , , Hllux , , Lesser toes , , Volume 49 Number 2 April 2014 //xinet/production//ttr/live_jobs/ttr-49-02/ttr /lyouts/ttr d Š 29 Jnury 2014 Š 4:49 pm Š Allen Press, Inc. Š Customer MS# Pge 4

5 Tble 3. Contct Are During the Side-Cutting Tsk, Normlized Insole Contct Are Foot Region Tble 4. Weight crossover cut tsk cn be found in Tble 8. No differences existed for the remining regions of the foot. DISCUSSION No Mximum Force During the Side-Cutting Tsk, Body No Totl foot , , 0.80 Rerfoot , , 0.22 Medil midfoot , , 0.07 Lterl midfoot , , 0.14 Medil forefoot , , 0.07 Mid forefoot , , 0.08 Lterl forefoot , , 0.08 Hllux , , 0.05 Lesser toes , , 0.09 Totl foot , , 2.34 Rerfoot , , 1.05 Medil midfoot , , 0.10 Lterl midfoot , , 0.21 Medil forefoot , , 0.37 Mid forefoot , , 0.42 Lterl forefoot , , 0.23 Hllux , , 0.32 Lesser toes , , 0.26 The purpose of our study ws to determine the mgnitude of chnge in plntr loding during side cut nd crossover cut with the use of rigid crbon fiber footplte. Our results indicte tht plntr loding incresed during both tsks when the crbon insert ws worn compred with performing the cutting tsks without the insert. During the crossover cut, the totl foot pek pressure, mximum force, nd force-time integrl were ll incresed when the crbon footplte ws used, while the contct re ws decresed. The force-time integrl is mesure of the re under the force-time curve nd indictes not only how much the foot is being loded but for how long. A decrese in the forcetime integrl is generlly believed to be beneficil for preventing injuries. Previous literture 20,21,28,29 on plntr-pressure distributions while performing these thletic tsks is limited. Queen et l 20,28 exmined differences in plntr loding during specific thletic tsks. During side cut, most of the lod ffected the medil portion of the foot, wheres during the crossover cut, most of the lod ws beneth the lterl column of the foot. Therefore, the loding ptterns differed between the cutting tsks. The results of the shoe-only condition re consistent with previous reserch During either type of cut while wering the shnk, the lterl column of the foot experienced incresed pressures nd decresed contct re when compred with cutting without the crbon inserts. When we exmine the effect of plntr loding on the incidence of fifth mettrsl stress frctures, the re of interest is the lterl column, which includes the LFF nd LMF. Plcing rigid crbon footplte in the shoes, however, resulted in higher plntr loding during the tsks studied, which ws contrry to our expecttions. Our findings show tht when performing both the side cut nd the crossover cut with the rigid insert, pek pressure incresed in the LMF compred with completing these tsks without the shnk. Additionlly, in the crossover cut, pek pressure in the LFF incresed. These results suggest tht the crbon plte ws not effective in decresing plntr loding in group of helthy prticipnts. However, no informtion exists regrding the use of these insert in ptients with fifth mettrsl stress frctures to understnd if their response differs. Although mny fctors hve been identified tht increse plntr loding nd risk fctors for fifth mettrsl frctures, 2 it is importnt to understnd tht ltered sher stress, which cnnot be mesured using current plntrloding systems, my lso exist between the foot, shoe, nd Tble 5. Pek Pressure During the Crossover Cutting Tsk, kp No Totl foot , , Rerfoot , , Medil midfoot , , Lterl midfoot , , Medil forefoot , , Mid forefoot , , Lterl forefoot , , Hllux , , Lesser toes , , Journl of Athletic Trining 0 //xinet/production//ttr/live_jobs/ttr-49-02/ttr /lyouts/ttr d Š 29 Jnury 2014 Š 4:49 pm Š Allen Press, Inc. Š Customer MS# Pge 5

6 Tble 6. Force-Time Integrl During the Crossover Cutting Tsk, ns No Totl foot , , Rerfoot , , Medil midfoot , , 4.92 Lterl midfoot , , Medil forefoot , , Mid forefoot , , Lterl forefoot , , Hllux , , Lesser toes , , rigid crbon footplte. Controlling sher stress could be criticl in improving heling nd decresing the time lost due to injury. 30 Therefore, the inbility to quntify sher forces is limittion of this study. Sex, shoe, nd thletic tsk were controlled, but other fctors might influence the pressure-distribution ptterns, including type nd speed of movement. 20,28,31 The reltive chnges in plntr loding due to ftigue re unknown. Also unknown re the interctions of these vrious limittions in norml prticipnts, in injured thletes, nd during trining nd competition. Our results do not support the hypothesis tht the use of rigid crbon footplte reduces plntr loding during cutting when compred with performing these sme tsks in shoes without the footplte. The crbon footplte did not decrese loding beneth the lterl column in helthy people during gility ctivities, but previous study 32 in ptients with midfoot rthritis indicted tht the crbon shnk ws effective in reducing plntr loding during wlking. The results of our study indicte tht the use of rigid crbon footplte ctully incresed loding in the lterl column of the foot during cutting tsks nd would probbly not be wrrnted for ptients hoping to compete in gility sports while recovering from fifth mettrsl stress frcture. The crbon plte could be detrimentl to heling nd ineffective in decresing plntr loding beneth the lterl column of the foot. Future uthors should exmine the chnges in plntr loding both with nd without Tble 7. Contct Are During the Crossover Cutting Tsk, Normlized Insole Contct Are No Totl foot , , 0.79 Rerfoot , , 0.21 Medil midfoot , , 0.05 Lterl midfoot , , 0.15 Medil forefoot , , 0.07 Mid forefoot , , 0.08 Lterl forefoot , , 0.07 Hllux , , 0.05 Lesser toes , , 0.08 Figure 4. Chnges in regionl plntr pressure during the crossover-cutting tsk. Arrow indictes chnge in the specific vrible when the crbon fiber footplte ws worn in the shoe. 0 Volume 49 Number 2 April 2014 //xinet/production//ttr/live_jobs/ttr-49-02/ttr /lyouts/ttr d Š 29 Jnury 2014 Š 4:49 pm Š Allen Press, Inc. Š Customer MS# Pge 6

7 Tble 8. Mximum Force During the Crossover Cutting Tsk, Body Weight crbon grphite footplte in ptients with mettrsl frctures, which could id in the understnding of whether this novel tretment is n effective tretment for reducing heling time nd expediting return to ctivity. REFERENCES No Totl foot , , 2.16 Rerfoot , , 1.03 Medil midfoot , , 0.07 Lterl midfoot , , 0.45 Medil forefoot , , 0.19 Mid forefoot , , 0.43 Lterl forefoot , , 0.33 Hllux , , 0.26 Lesser toes , , Hwkins RD, Fuller CW. A prospective epidemiologicl study of injuries in four English professionl footbll clubs. Br J Sports Med. 1999;33(3): Murphy DF, Connolly DAJ, Beynnon BD. Risk fctors for lower extremity injury: review of the literture. Br J Sports Med. 2003; 37(1): Porter DA, Duncn M, Meyer SJ. Fifth mettrsl Jones frcture fixtion with 4.5-mm cnnulted stinless steel screw in the competitive nd recretionl thlete: clinicl nd rdiogrphic evlution. Am J Sports Med. 2005;33(5): Queen RM, Nunley JA. 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The plntr loding vritions to uphill nd downhill grdients during tredmill wlking. Foot Ankle Int. 2000;21(3): Urry SR. Redistribution of foot pressure in helthy dults during sideslope wlking. Foot Ankle Int. 2002;23(12): Willson JD, Kernozek TW. Plntr loding nd cdence ltertions with ftigue. Med Sci Sports Exerc. 1999;31(12): Queen RM, Mll NA, Nunley JA, Chuckpiwong B. Differences in plntr loding between flt nd norml feet during different thletic tsks. Git Posture. 2009;29(4): Queen RM, Chrnock BL, Grrett WE Jr, Hrdker WM, Sims EL, Moormn CT III. A comprison of clet types during two footbllspecific tsks on FieldTurf. Br J Sports Med. 2008;42(4): Sntos D, Crline T, Flynn L, et l. Distribution of in-shoe dynmic foot pressures in professionl footbll plyers. The Foot. 2001;11(1): Ekstrnd J, Nigg BM. Surfce-relted injuries in soccer. Sports Med. 1989;8(1): Rosenbum D, Hutmnn S, Gold M, Cles L. Effects of wlking speed on plntr pressure ptterns nd hindfoot ngulr motion. Git Posture. 1994;2(3): Ro S, Bumhuer JF, Nwoczenski DA. Is brefoot regionl plntr loding relted to self-reported foot pin in ptients with midfoot osteorthritis. Osteorthr Crtilge. 2011;19(8): Address correspondence to Robin M. Queen, PhD, 102 Finch Yeger Building DUMC 3435, Durhm, NC Address e-mil to robin.queen@duke.edu. Journl of Athletic Trining 0 //xinet/production//ttr/live_jobs/ttr-49-02/ttr /lyouts/ttr d Š 29 Jnury 2014 Š 4:49 pm Š Allen Press, Inc. Š Customer MS# Pge 7

8 Queries for ttr This mnuscript/text hs been typeset from the submitted mteril. Plese check this proof crefully to mke sure there hve been no font conversion errors or indvertent formtting errors. Allen Press.