Outcome after nonoperative treatment of stable Lisfranc injuries. A prospective cohort study

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Outcome after nonoperative treatment of stable Lisfranc injuries.

A prospective cohort study

Are H. Stødle

^a,c,

*, Kjetil H. Hvaal

^a

, Helga Brøgger

^b

, Jan Erik Madsen

^a,c

, Elisabeth Ellingsen Husebye

^a

aDivisionofOrthopaedicSurgery,OsloUniversityHospital,Norway

bDepartmentofRadiologyandNuclearMedicine,OsloUniversityHospital,Norway

cInstituteofClinicalMedicine,UniversityofOslo,Norway

ARTICLE INFO

Articlehistory:

Received22February2021

Receivedinrevisedform15March2021 Accepted23March2021

Availableonlinexxx

Keywords:

Lisfrancinjury

Tarsometatarsaljointinjury Midfootinjury

Stable Nonoperative

ABSTRACT

Background:TheaimofthisstudywastoevaluatetheoutcomeafternondisplacedandstableLisfranc injuries.

Methods: 26patientswithinjuriestotheLisfrancjointcomplexdetectedon CTscans,but without displacementweretestedtobestableusingaﬂuoroscopicstresstest.Thepatientswereimmobilizedina non-weightbearingshortlegcastfor6weeks.Theﬁnalfollow-upwas55(IQR53–60)monthsafterinjury.

Results:AlltheLisfrancinjurieswereconfirmedtobestableonfollow-upweightbearingradiographsata minimumof3monthsafterinjury.MedianAmericanFootandAnkleSociety(AOFAS)midfootscoreat1- yearfollow-upwas89(IQR84–97)andatfinalfollow-up100(IQR90–100);TheAOFASscorecontinuedto improveafter1-year(P=.005).Themedianvisualanalogscale(VAS)forpainwas0(IQR0–0)atthefinal follow-up.Onepatienthadradiologicalsignsofosteoarthritisat1-yearfollow-up.

Conclusion:StableLisfrancinjuriestreatednonoperativelyhadanexcellentoutcomeinthisstudywitha medianfollow-upof55months.TheAOFASscorecontinuedtoimproveafter1year.

1.Introduction

The Lisfranc joint complexcomprise of thetarsometatarsal, intercuneiformandnaviculocuneiformjointswiththeirassociated ligaments [1,2].Lisfranc injuries can varyfromsevere fracture- dislocationstostablenondisplacedinjuries[3–8].Theincidenceis previously reported to be 1/60 000 person-years, but recent studiesreportahigherincidencerangingfrom9.2to14/100000 person-years[8–10].Upto24%ofLisfrancinjuriesaremissedon initial radiographs [8,11,12]. The increase in reportedincidence seems to be related to an increased awareness of this entity, togetherwithmoreadvanceddiagnostictoolssuchasCTscan,MRI, weightbearingradiographsandﬂuoroscopicstresstest[7,8,10].

Operative treatment with anatomic reduction and stable fixationarethemostimportantfactorsinachievingafavorable outcome in the unstable Lisfranc injuries [1,13–15]. A stable LisfrancinjuryhasbeendefinedasaninjurytotheLisfrancjoint complexwithdisplacement<2mmonweightbearingradiographs and/or no obvious displacement on stress fluoroscopy, when

comparedtothenon-injuredfoot[3,7,8,16–18].ForstableLisfranc injuriesnonoperativetreatmentisrecommended,althoughonly fewstudieswithsmallpatientnumbersexist[5,19,20].Also,only onestudyveriﬁesstabilitybyobtainingfollow-upweightbearing radiographs,andnonehaveroutinelyobtainedCTscanstoruleout minordisplacements[19,21].

Theaimofthepresentstudywastoevaluatetheoutcomeafter nonoperativetreatmentofstableLisfrancinjuries.

2.Materialsandmethods

A prospective cohortstudy includingstable Lisfrancinjuries was conductedat Oslo UniversityHospital (a levelone trauma center) and Oslo Accident and Emergency Department. The patientsinthepresentstudywerealsoincludedinapreviously publishedstudyreportingonincidence,mechanismofinjuryand predictors of instability [8]. The study was approved by The RegionalCommitteeforMedicalandHealthResearch(2014/849/

REK)andapprovedbythedataprotectionofﬁcerattheuniversity hospital.Aninformed consentformwas signed bythepatients prior toenrollment.Patientspresenting withanisolatedstable Lisfrancinjury betweenSeptember1,2014andAugust31,2015 wereinvitedtoparticipate.

*Corresponding author at: Ortopedisk avdeling, Oslo Universitetssykehus, Kirkeveien166,0450Oslo,Norway.

E-mailaddress:[email protected](A.H. Stødle).

https://doi.org/10.1016/j.fas.2021.03.017

creativecommons.org/licenses/by/4.0/).

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Pleasecitethisarticleas:A.H.Stødle,K.H.Hvaal,H. Brøggeret al.,OutcomeafternonoperativetreatmentofstableLisfrancinjuries.A ContentslistsavailableatScienceDirect

Foot and Ankle Surgery

j o u r n a lh o m e p ag e :w w w . e l s e vi e r . c o m / l o c a t e / f as

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Anacute,stableLisfranc injury wasdeﬁnedasacute trauma (Lisfranc injury diagnosed within 4 weeks) presenting with midfootpainonweightbearingandmanipulationofthemidfoot.

Inaddition,radiographsveriﬁedinjurytothetarsometatarsaljoint linewithintraarticularoravulsionfractures,butnodisplacement of2mmonradiographsorCTscansorobviousdisplacementon stresstestunderﬂuoroscopy(Fig.1).

ExclusioncriteriawereunstableLisfrancinjuries,concomitant lower extremity injuries, Charcot arthropathy, isolated ﬁfth metatarsal fracture, non-compliant patient and patient not availableforfollow-up.

Patientcharacteristicsandmechanismofinjurywereregistered atenrollment.Injuredfeetweretestedforoccultinstabilitybya stresstestunderﬂuoroscopy[22,23].Asthistestwasperformed7– 14daysafterinjury,anesthesiawasunnecessaryinmostpatients.

Ifneeded,thefootwastestedundergeneralanesthesia.Thestress test was positive if joint displacement was detected, and the oppositenon-injuredfootwastestedforcomparison.

The patients were treated with immobilization in a non- weightbearing short leg cast for 6 weeks. If no pain on weightbearing at 6 weeks they started full weightbearing in normal shoes,whereas ifpainwas presentthey wereoffereda Walkerbootwithfullweightbearingforthenext4weeks.

WeightbearingAP,obliqueandlateralradiographsofboththe injuredandnon-injuredfeetwereobtainedat6weeks,3months and12monthsfollow-up.4–5yearsafterinjurythepatientswere interviewedbyphoneandinvitedtoaﬁnalfollow-up.

RadiographsandCTscanswereevaluatedusingSyngoStudio VB36E (Siemens Healthcare GmbH, Erlangen, Germany). Two orthopaedicsurgeonsspecializedinfootandanklesurgeryandone musculoskeletalradiologyconsultantevaluatedtheimages.

Injuries to the tarsometatarsal joints were categorized as avulsion fractures or intraarticularfractures and locatedtothe medial, middle and lateral column according to the columnar theoryasdescribedbyChiodoandMyerson,andlaterrevisedby SchepersandRammelt[16,24].

TheprimaryoutcomemeasurewastheAmericanOrthopaedic FootandAnkleSocietymidfootscore(AOFASscore),consistingof threemaincomponents(pain,function,andalignment),ranging from0to100withbestscorebeing100[25].Secondaryoutcome measureswerethe36-ItemShortFormHealthSurvey(SF-36)and the visual analog scale for pain (VAS pain) at rest and during walking.

Patientsnotabletoattendﬁnalfollow-upwereinterviewedby phoneandtheAOFASscore,Numericratingscale(NRS)forpainat rest and during walking, as well as return to activities were addressed.Withregardstogaitabnormalityandalignmentpartsof theAOFASscore,thepatientsinterviewedbyphonewereasked aboutanygaitabnormalityorifthealignmentoftheirfoothad changed (comparedtothenon-injuredfoot). TheNRS painhas beenshowntohighlycorrelatetotheVASpain[26].

Secondary displacement and signs ofposttraumatic osteoar- thritis (OA)wereevaluatedon theradiographs obtainedatthe follow-ups.Radiographswerenotroutinelyobtainedattheﬁnal follow-up.

3.Statistics

StatisticalanalyseswereconductedusingSPSSversion26(SPSS Inc,IBM,Chicago,IL).Dataweretestedfornormalityandnormally distributed dataarepresentedwithameanvalueand standard deviation (SD). The one sample t-test was used for statistical analysis.Non-parametricdataarepresentedwithmedianvalues andtheinterquartilerange(IQR)andtheWilcoxonsignedranktest wasusedforstatisticalanalysis.Thesigniﬁcancelevelwassetto P<05.

WhenexaminingthechangeinAOFASscoreovertime,aone- sampleT-testwas conductedtodeterminewhethertheaverage slope (change in AOFAS score per one-month time unit) was differentfromzero(nochange).Tobeabletoevaluatechangein Fig.1.(a,b,c)36yearsoldmalewhofellduringjogging,wasunabletoweightbear onhisforefootandhadmidfootpainandplantarecchymosis.ACTscanrevealeda nondisplacedintraarticularfractureatthebaseofthe2ndmetatarsal(aandb).A dorsolateral avulsion fracture ofthe third cuneiform and extraarticular non- displacedfracturesoftheproximalthirdandfourthmetatarsalwaspresent(not shown).Thefootwasstablewhenstresstestedunderﬂuoroscopy.Nodisplace- mentsweredetectedonweightbearingradiographsofbothfeetatthe3-month follow-up(c).

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AOFASscoreoverthewholestudyperiod,onlypatientswhohad AOFAS score measured at 3 and/or12 monthsand at the ﬁnal follow-upwereincluded.Theslopewascomputedbetweeneither

“ﬁnal follow-up – 3 months”, or “ﬁnal follow-up – 1 year”, dependingonwhatdatawasavailableforeachsubjectandthen dividedbythenumber ofmonthsoccurringbetweenthesetwo measurements.

4.Results

Eighty-nine Lisfrancinjuries were registeredduringthe one year inclusion period,48 of theseinjuries werestable. Sixteen patientsdidnot meet theinclusion criteriadue tootherlower extremityinjuries(n=11),presentationlaterthan4weeksafter injury(n=2),residencyoutsideNorway(n=3).Sixpatientsdidnot wanttoparticipateinthestudy.Twenty-sixpatientswithisolated stable Lisfrancinjuries wereincluded. Patient characteristicsat enrollmentandmechanismsofinjuryarepresentedinTables1a and1b.Aplantarecchymosiswasregisteredin20/26patients.

Twenty-three of the patients had initial non-weightbearing radiographs and nine of these radiographs were evaluated as normal. CT scans were obtained of all injured feet prior to inclusion,allofwhichshowedavulsionfracturesorintraarticular fractures in the TMT jointline, indicating a Lisfrancinjury. No displacementof2mmormoreweredetectedinanyjointsofthe Lisfranc joint complex. Radiological ﬁndings are presented in Table2.

Astresstestunderﬂuoroscopywasperformedin25ofthe26 patientsat median 10(IQR8–14) daysafterinjury, toevaluate stability.Allstresstestswerenegative.Onepatientdidnothavea stresstest(an80-yearsoldfemale).Onthefollow-upweightbearing radiographs, none of the patients had any subsequent displacement in the Lisfranc joint complex. When comparing theinjuredfoottothenon-injuredfoot,noneofthe26patientshad adifferenceof2mmormoreintheC1-M2intervalortheM1-M2 intervalonthefollow-upweightbearingradiographsat6,12and 52weeks.Onlyonepatienthadradiologicalsignsofdegenerative jointdiseaseatthe1-yearfollow-up,thejointdegenerationwas locatedtotheTMT-1jointwherethepatienthadanintraarticular fractureonpresentation.Thepatientpresentednosymptomsfrom theinjuredfootattheﬁnalfollow-up.

The AOFAS score, VAS pain scores and SF-36 are listed in Tables3and4.

14/26patientsattendedtheﬁnalfollow-up,eightpatientswere interviewedbyphoneand fourpatientswerelosttofollow-up.

Medianfollow-uptimewas55(IQR53–60)months.Oftheeight patientsinterviewedbyphone,sevenpatientsreportednopainor discomfortfromtheirinjuredfoot.Onepatientreportedmildpain at rest(NRS 1/10)and duringwalking (NRS 1/10).Noneof the patients interviewedby phone on theﬁnalfollow-up reported limitationsduringactivities,walkingdistance,footwearorwalking surface.Nopatientsreportedanygaitabnormalityorwereableto detectanychangeinappearanceoralignmentoftheirinjuredfoot comparedtothenon-injuredfoot.

TwentypatientshadatleastoneearlierAOFASscoreinaddition totheAOFASscoreattheﬁnalfollow-up.Thescoresfromthese

patientswereusedtocalculatetheslopesoftheAOFASscoreover time.TheslopeswerenormallydistributedasassessedbyShapiro- Wilk'stestof normality(p=0.228). Meanslope (0.24,SD=0.17) wasstatisticallydifferentfromzero,t(19)=6.57,p<.001,indicating apositivechangeinAOFASscoreovertime.Withregardtothetime periodfrom1yearafterinjuryuntiltheﬁnalfollow-up(median55 Table1a

Patientcharacteristicsattimeofinclusion.

Patientcharacteristics

Numberofpatients 26

Gender(Male/Female) 15/11

Side(Right/Left) 14/12

Age(mean,SD) 40.0(15.7)

Timeinjury-diagnosisindays(mean,SD) 2.2(5.7)

Plantarecchymosis 20

Table1b

Mechanismsofinjury.

Mechanismofinjury

Fallfromownheight/twistinginjuryoffoot 7

Falldownstairs 1

Bikeaccident 2

Kickedintoanobject 1

Sportsrelatedinjury 4

Motorvehicleaccident 2

Fall>3meters 2

Crushinjury 7

Table2

Noneofthepatientshadisolatedlateralcolumninjuries.

Radiologicalﬁndings

Initialnon-WBradiographs(pos/neg)^a 14/9

PositiveCTscans^b 26

Medialcolumn

Negative 8

Avulsionfx 10

Intraarticularfx 8

Middlecolumn

Negative 5

Avulsionfx 5

Intraarticularfx 13

Lateralcolumn

Negative 15

Avulsionfx 1

Intraarticularfx 7

WB=weightbearing.Fx=fracture.

aPositive=Fracturesdetectedoninitialnon-weightbearingradiographs.

b IntraarticularfracturesoravulsionfracturesTMTjoints.

Table3

AmericanFootandAnkleSociety(AOFAS)midfootscoreandthevisualanalogscale forpain.(VASpain).Themedianandinterquartilerange(IQR)arereported.

3months (19patients)

1year (20patients)

FinalFU^a(22patients

b)

AOFASmidfootscore 85(77–87) 89(84–97) 100(90–100) VASpainscore

Atrest 0(0–2) 0(0–1.1) 0(0–0)

Duringwalking 3(2–5) 0.5(0–2.4) 0(0–0)

aFinalfollow-up(FU)=Median55(IQR53–60)months.

b 8ofthe22patientswereinterviewbyphone.

Table4

36-ItemShort FormHealthSurvey (SF-36) score at1 year. Themedianand interquartilerange(IQR)arereported.

SF-36 1year(20patients)

Physicalfunction 95(86.3–100)

Rolephysical 100(75–100)

Bodilypain 78.8(60–90)

Generalhealth 70(57.5–80)

Vitality 65(47.5–70)

Socialfunction 100(78.1–100)

Roleemotional 100(41.7–100)

Mentalhealth 80(66–88)

Physicalcomponentsummary(PCS) 51.8(46–54.6) Mentalcomponentsummary(MCS) 52.9(40.9–58.4)

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months), there was also an improvement of the AOFAS score (median89 vs100,P=.005)indicatinga positivechangeinthe AOFASscorebetween1yearandﬁnalfollow-up.

Noneofthepatientsreportedwork-relatedlimitationsdueto theirLisfrancinjuryatﬁnalfollow-up,but2/22patientsreported somelimitations inrecreationalsports activities(skateboarding andskiing).Noneofthepatientshadundergoneanysurgeriesto theirfootatﬁnalfollow-up.

5.Discussion

TheoutcomeofnonoperativelytreatedstableLisfrancinjuries in 26 patients are presented in this study. Allinjuries had CT verified avulsion fractures or intraarticular fracture in the tarsometatarsal joint line. The stability was verified using fluoroscopicstresstestandfollow-upweightbearingradiographs ataminimumof3monthsafterinjury.Theoutcomeafteramedian follow-up timeof 55(IQR 53–60)monthswas excellentwitha medianAOFASmidfootscoreof100(IQR90–100),improvingfrom 89(IQR84–97)at1year(P=.005).Osteoarthritisdoesnotseemto be frequent after a stable Lisfranc injury as degenerative joint diseasewasonlydetectedradiologicallyat1-yearinonepatient.

Only 2/22 patients reported limitations in recreational sports activitycausedbytheirLisfrancinjuryattheﬁnalfollow-up.Stable Lisfrancinjuriesareeasilyoverlookedas9/23injurieswerenot detectedoninitialnon-weightbearingradiographs.

MostpreviouspapersonLisfrancinjuriesfocusontheunstable fracture-dislocations and only few report on the stable and nondisplacedLisfrancinjuries[3,5,19,20].Stableinjuriesarebest treated nonoperatively, while the unstable injuries should be treated operatively [5,7,16,27–29]. Oneof themost challenging issues concerning Lisfranc injuries is to adequately evaluate stabilityofthenondisplacedLisfrancinjuriesandtherebyproperly select the right patients for nonoperative treatment. Minor displacements of the TMT joints indicating instability are best evaluatedusingCTscansastheyareoftenmissedonradiographs [21]. To detect occult instability in the nondisplaced Lisfranc injuries, the feet can be examined using either weightbearing radiographsorafluoroscopicstresstest[5,17,22,23,27,30,31].MRI hasalsobeenshowntohaveahighaccuracyindetectinginstability in ligamentous Lisfranc injuries [18,32]. When evaluating both weightbearing radiographs and fluoroscopic stress tests the injuredfootshouldbecomparedtothenon-injuredfoot,asthe M1-M2andC1-M2distancesshowvariancebetweenindividuals andalsobetweenthenon-weightbearingandweightbearingstate [2,5,7,18,27,29].Thefluoroscopicstresstesthasbeencriticizedfor lack of reliability in detecting unstable Lisfranc injuries, even though it is reported to be more sensitive compared to weightbearingradiographsincadaverstudies[22,23,33,34].

In a study by Chen et al. on minimally displaced Lisfranc injuriesevaluatedbyweightbearingradiographsatpresentation, 14/26 patients showed subsequent displacement at follow-up, where 9/14 were detected within 14 days [19]. Preidleret al.

showedthatobtainingweightbearingradiographsonthedayof injury did not add any information to non-weightbearing radiographs[35].Thisemphasizesthattheassessmentofstability in thesenondisplacedinjuriesis difficult,especially duringthe firstdaysafterinjury.Hence,testingthestabilityofthemidfoot should be postponed until 7–14 days, when pain is reduced [8,16,19,27]. The patients should also be reassessed with weightbearing radiographs at follow-ups to detect any subsequent displacement [19,27]. Inthe present study, the Lisfranc injuriesweretestedforinstabilityusingafluoroscopicstresstest at a medianof10(IQR 8,14) days. Weightbearingradiographs wereobtainedat6and12weeksand1year.Noneoftheinjured feetshowedanysubsequentdisplacement.

Although the stable Lisfranc injuries are uniformly recom- mendednonoperativetreatment,onlyfewauthorshavereported ontheoutcomeofnondisplacedLisfrancinjuriesafterevaluating the stability using weightbearing radiographs or fluoroscopic stresstests[3,5,19,20].Nunleyetal.reportedexcellentoutcome after Lisfranc injuries that were tested to be stable using weightbearing radiographs [5]. In their study only one of the sevenpatientswithastableLisfrancinjurypresentedwithinthe first4weeks,incontrasttothepresentstudy,whereallpatients presentedwithinthefirst4weeks.

Chenetal.reportedon12/26patientswitha stableLisfranc injurytreatednonoperatively.³ThepatientreportedAOFASscore atmeanfollow-upof54monthswas78.0(95%CI,68.6–87.4)and Manchester-Oxford Foot Questionnaire (MOXFQ) 24.8 (95% CI, 11.1–38.5).TheAOFASscorewaspoorerthantheexcellentresults wepresentatamedianof55months,median100(IQR90–100).

ThismaybeexplainedbyadifferenceinthenatureoftheLisfranc injuriesincludedinthetwostudies.InChen'sstudy,theinclusion criteriawerelessthan2mmdiastasisbetweenthebasesofthefirst andsecondmetatarsal(M1-M2)andnodisplacementinthethird, fourthandfifthtarsometatarsaljoint.Thus,anincreaseddiastasis between the medial cuneiform and the base of the second metatarsal(C1-M2)inadditiontodisplacementofthefirstand secondtarsometatarsaljointcouldbepresent.Inourstudyonly injurieswithlessthan2mmdifferenceintheC1-M2intervaland theM1-M2interval,andnodisplacementinanytarsometatarsal jointswereincluded.Alltheinjuredfeetinourstudywerealso initially evaluated by CT scans. Injuries with displacements of 2mm or morewereconsidered unstable and therebyexcluded fromthestudy.InthestudybyChenetal.multiplanarimagining wasnotroutinelyobtained,butlefttothediscretionofthetreating surgeon[19].

Cratesetal.reportedtheoutcomesof36patientswithsubtle Lisfrancinjuries,includingpatientswith2mmorlessdiastasisin theM1-M2intervalonweightbearingradiographs.16/36patients weretreatedsuccessfullynonoperatively,while20patientsfailed nonoperative treatment. Failed nonoperative treatment were basedonjudgementbythesenior author,andneithertimingof initial weightbearing radiographs, nor the time from injury to failed nonoperative treatment or the use of weightbearing radiographsonfollow-up werespeciﬁed[20].Furthermore,the injuries inthat studywerenotevaluatedbyCTscanstodetect minordisplacements, indicatingunstable injuries.These factors andthepoorAOFASscoreinthegroupwhofailednonoperative treatment(meanAOFASscoreof63.5)comparedtothegroupwith successful nonoperative treatment (mean AOFAS score=90.2, calculatedfromthesubgroupsreported)suggestthattheinjuries failingnonoperativetreatmentwereinfactunstableinjuries.

TheAOFAS scorein thepresent studycontinuedtoimprove evenafter1year(median89versus100,P=.005),implyingthatthe rehabilitationperiodcanbeprolongedoveryears.

TheVASpainscoreatrestandduringwalkingatﬁnalfollow-up were both 0 (IQR: 0–0), corresponding well with an excellent outcome.Also, themedian SF-36physicalcomponentsummary score(PCS51.8)andmentalcomponentsummaryscore(MCS52.9) atthe1-yearfollow-upwereequivalenttothescoresofthegeneral population(40–49years old, PCS mean50.8 (SD9.1) and MCS mean52.6(SD9.1))indicatingreturntothesamequalityoflifeas the Norwegian general population [36]. Only 2/22 patients reportedlimitations inrecreationalsports activities(skiingand skateboarding)atﬁnalfollow-up.Wehavenotencounteredany otherstudyreportingVASpainscoreorSF-36afterstableLisfranc injuries.

AhighincidenceofradiographicposttraumaticOAisreported inpatientstreatedfor unstableLisfrancinjuries[14,37–40].The frequency of posttraumatic OA afterstable Lisfranc injuries is xxx–xxx

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largelyunknown.Chenetal.reportedon12stableLisfrancinjuries treatedconservativelywithafollow-upof54monthsandfollow- upradiographsatminimum24weeks;Noneofthestableinjuries showedsigns of degenerativejoint disease[19]. Inthe present studyonlyonepatienthadradiologicalsignsofposttraumaticOA at1yearandnopatientshadclinicalsignsofOAat5years.

Thepresentstudyhassomestrengths,ﬁrstlytheprospective designwithamedianfollow-upof55months.Allbutonepatient were tested for stability and all patients had weightbearing radiographsobtainedataminimumof3months.Theinjurieswere all assessedusingCTscanstoverifyinjury totheLisfrancjoint complex(fractures,includingavulsionfractures)andruleoutany subtle displacementsoftennotdetected onconventionalradio- graphs [41]. All patients followed the same nonoperative treatmentprotocol.Althoughthestudyincludedonly26patients, itistoourknowledgethelargeststudyonstableLisfrancinjuries treatednonoperativelythroughouttheentirestudyperiod.

The studyalsocontains someinherent weaknesses.Only14 patientswereavailableforthefinalfollow-upvisit,thefurther8 patientswereinterviewedbyphoneand4patientswerelostto follow-up.As8patientswereinterviewedbyphoneatthefinal follow-up,anygaitabnormalityormalalignmentnotdetectedby thepatientsthemselvesmighthavebeenmissed,eventhoughthis was not detectedin thesepatientsonprevious follow-ups.The patients did not routinely have radiographs obtained at final follow-upandanyradiologicalOAwithoutclinicalmanifestationat thatpointwastherebynotdetected.TheAOFASmidfootscalehas beenshowntohaveaceilingeffectandthereforealimitedability todifferentiatebetweenpatientswithhighoutcomescores[42].

We used ﬂuoroscopic stress test for the initial evaluation of stability of non-displaced Lisfranc injuries and weightbearing radiographsatfollow-ups.Inthefuture,weightbearingCTscans might be an even more precise method to detect any occult instability[43].

6.Conclusion

StableLisfrancinjuriestreatednonoperativelyhadanexcellent outcome55monthsafterinjuryinthisprospectivecohortstudy.

TheAOFASmidfootscorecontinuedtoimproveevenafter1year.

Assessment ofstability inLisfranc injuriesshouldpreferablybe done7–14daysaftertheinjury.Noneofthepatientshadclinical symptomsofposttraumaticosteoarthritisattheﬁnalfollow-up, onepatienthadradiologicallydetecteddegenerativejointdisease atthe1-yearfollow-up.

Conﬂictofinterest None

Acknowledgements

WewouldliketothankMaijuPesonenforstatisticalsupport.

Thisstudyhasnotreceivedanyfunding.

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