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  1. Injury,Int.J.CareInjured47(2016)1569–1573 ContentslistsavailableatScienceDirect Injury journalhomepage:www.elsevier.com/locate/injury Zone2sacralfracturesmanagedwithpartially-threadedscrewsresult inlowriskofneurologicinjury AmirHermana,b,*,EmilyKeenera,CandiceDubosea,JasonA.Lowea aTheOrthopaedicTraumaUnit,DivisionofOrthopaedics,UniversityofAlabamaatBirmingham,UnitedStates bTalpiotMedicalLeadershipProgram,ShebaMedicalCentre,Israel ARTICLE INFO ABSTRACT Articlehistory: Accepted9April2016 Background:Zone2sacralfracturesaccountfor34%ofsacralfractureswithreportedneurologicaldeficit in21!28%ofpatients.Thepurposeofthisstudywastoexaminetheriskfactorsforneurologicalinjuryin zone2sacralfractures.Theauthorshypothesizedthatpartiallythreadiliosacralscrewsdidnotincrease incidenceofneurologicinjury. Methods:Aretrospectivereviewofconsecutivepatientsadmittedtoalevel1traumacenterwithzone2 sacralfracturesrequiringsurgeryfromSeptember2010toSeptember2014wasperformed.Patients wereexcludedifnoneurologicexamwasavailableaftersurgery.Fractureswereclassifiedaccordingto Denisandpresence/absenceofcomminutionthroughtheneuralforamenwasnoted.Fixationschema wasrecorded(sacralscrewsoropenreductionandinternalfixationwithposteriortensionplate).Any changeinpost-operativeneurologicalexamwasdocumentedaswellasexamatlastclinicencounter. Results:90patientsmetinclusioncriteria,withzone2fracturesandpost-operativeneurologicalexam. Nopatientwithanintactpre-operativeneurologicexamhadaneurologicaldeficitaftersurgery.86 patients(95.6%)wereneurologicallyintactattheirlastfollow-upexamination.Fourpatients(4.4%)hada neurologicaldeficitatfinalfollow-up,allofthemhadneurologicaldeficitpriortosurgery.81patients weretreatedwithpartiallythreadedscrewsofwhich1(1.2%)hadneurologicaldeficitatfinalfollow-up. Fifty-sevenfractures(63.3%)weresimplefracturesand33fractures(36.7%)werecomminuted.All fourpatientswithneurologicaldeficithadcomminutedfractures.Theassociationbetweenneurologic deficitinzone2sacralfractureandfracturecomminutionwasfoundtobestatisticallysignificant(p- value=0.016).Nononunionwasobservedinthiscohort. Conclusions:Theuseofpartiallythreadedscrewsforzone2sacralfracturesisassociatedwithlowrisk forneurologicinjury,suggestingthatcompressionthroughthefracturedoesnotcauseiatrogenicnerve damage.Thelowrateofsacralnonunioncanbeattributedtocompressioninducedbytheuseofpartially threadedcompressionscrews.Thereisastrongassociationbetweenzone2comminutionandneurologic injury. Keywords: Trans-sacralscrews Sacroiliacscrews Partiallythreadedscrews !2016ElsevierLtd.Allrightsreserved. Introduction rangebetween34and47.5%ofallsacralfractures.Denisoriginally describedtheinfluenceoffracturezoneonneurologicaldeficitand prognosis,withzone2fracturescharacterizedbyinjurytotheL5 throughlowersacralnerveroots.Otherauthorsreportedthe incidenceofneurologicdamagetobeashighas21!28%of thepatientswithmostpatientsrecoveringatleastonefunctional level[4,5]. Severalfixationmethodsforofzone2sacralfractureshave beenexamined:posteriorplating[6,7],triangularfixationusing pedicularscrews[8]andsacroiliacortrans-sacralscrews[9–13]. Percutaneousfixationwithtrans-sacralorsacralscrewshas becomeapopularmethodoffixationowingto,lowcomplication ratesandgoodclinicaloutcomes[12,13].Inaddition,the Sacralfracturesoccurin23!45%ofallpelvicringinjuries,and whenfoundtobeunstable,requireoperativestabilization[1–3]. SacralfracturesareclassifiedaccordingtoDenis:extraforaminal (Zone1),involvingtheneuralforamina(Zone2)orinvolvingthe neuralcanal(Zone3)[3].Zone2sacralfracturesarereportedto * Correspondingauthorat:TheUniversityofAlabamaatBirmingham,Depart- mentofSurgery,DivisionofOrthopaedicSpineandTraumaFaculty,OfficeTower 901,510,20thStreetSouth,Birmingham,AL35294,UnitedStates. E-mailaddress:amirherm@gmail.com(A.Herman). http://dx.doi.org/10.1016/j.injury.2016.04.004 0020–1383/!2016ElsevierLtd.Allrightsreserved.

  2. 1570 A.Hermanetal./Injury,Int.J.CareInjured47(2016)1569–1573 biomechanicalpropertiesofthesacralscrewsshow80!85%return ofpelvicbiomechanicalrigidityafterinstrumentation[14,15]. Onepotentialconcernwithpartiallythreadedscrewsisthe potentialforcompressionandnarrowingoftheneuralforamen particularlythroughcomminutedfractures,whichmayresult iatrogenicneurologicinjury[16,17].Fullythreadedscrews representanalternativetopartiallythreadedscrewsasameans toavoidthispotentialcomplication[18,19]. Thepurposeofthisstudywastodefinetheincidenceofpost- operativeneurologicinjuryandidentifyriskfactorsforneurologi- caldeficitafterzone2sacralfractures.Theauthorshypothesized thatpartiallythreadedposteriorscrews(trans-sacral,sacral) wouldnotresultiniatrogenicneurologicinjury,andthatfracture comminutionthroughtheneuralforamenwouldpredictinjury- relatedneurologiccompromise. excludedbecausetheydidnothaveaneurologicalexamination priortosurgeryandhadaneurologicdeficitaftersurgery. Thestudypopulationincluded90patients,meanagewas39.10 ("15.03).Ofthe90patients,36patients(40.0%)weremaleand54 patients(60.0%)werefemale.Themostcommoncauseofinjurywas motorvehicleaccident–52patients(57.8%)followedbyfallfrom height–12patients(13.3%).Therewasnostatisticallysignificant differenceinthedemographiccharacteristicsbetweenneurologically intactanddeficientpatients(Table1). Ofthe90patients,86(95.6%)hadnoneurologicaldeficitatany timepoint.Fourpatients(4.4%)hadaneurologicaldeficitatfinal follow-up.Noneofthefourpatientswithfinalneurologicaldeficit hadanintactexaminationattimeofadmission.Thesefour patientspresentedwithweakbutpresentinitialmotorexam definedas2!3/5motorstrengthinthetibialisanterior,extensor hallucislongus,flexorhallucislongusorgastrocnemius–soleus complex.Nopatientpresentingwithaninitiallyintactneurologic examdevelopedaneurologicdeficitfollowingoperativefixation (Table2). Methods FollowinginstitutionIRBapproval,aretrospectivereviewofall pelvicringfracturesandfracturedislocationsfixedatasinglelevel 1traumaacademiccenterfromSeptember2010toSeptember 2014wasperformedusingCPTandICD-9codes.Patientinclusion criteriaincluded:age>18yearsatthetimeofinjuryandclosed zone2sacralfractureaccordingtoDenis.Exclusioncriteriawere: lackofneurologicalexaminationaftersurgery,patientsthatdid nothaveneurologicexaminationpriortosurgeryandhada neurologicdeficitaftersurgery,openfractures,andanypatient transferredafterfixationtoanoutsidefacility. Weextractedpatientdemographicdataincludingageand gender;aswellasinjuryprofiles(mechanismofinjury,abbreviat- edinjuryscore(AIS)andtheinjuryseverityscore(ISS)). Neurologicalstatusatarrival,firstavailableneurologicexamafter surgeryandlastclinicalfollow-upneurologicalexaminationwere obtainedfromconsult,post-operative,in-patientprogress,and clinicnotes,respectively.Furtherdatacollectionincluded: comminutedvssimplefractures,thesurgicalinterventionofopen vsclosedreduction,andposteriortensionbandplatefixation versuspercutaneousscrews,aswellasscrewtype(partially threadedvsfullythreaded),andscrewnumber. Neurologicdeficitatfinalfollowupwasdefinedasmotor strengthoflessthanfive(outoffive)oftheinjuredextremity. Table1 Demographicandinjuryrelateddata. Neurologically intactPostOp (N=86) Neurological deficitPostOp (N=4) P-value Age Gender Male Female Mechanismofinjury Assault CrushInjury Fallfromheight Fallfromhorse MCC MVC PedestrianvsMV Tornado AIS–Abdomen AIS–Extremities AIS–Injuryseverityscore 39.21("15.22) 36.75("10.43) 0.887 34(39.5%) 52(60.5%) 2(50.0%) 2(50.0%) 0.676 1(1.2%) 5(5.8%) 12(14.0%) 2(2.3%) 5(5.9%) 48(55.8%) 10(11.6%) 3(3.5%) 2.38("0.61) 3.02("0.88) 22.34("10.62) 00(00%) 00(00%) 00(00%) 00(00%) 00(00%) 4(100.0%) 00(00%) 00(00%) 3.33("1.53) 3.25("0.96) 30.5("8.34) 0.931 0.226 0.595 0.087 AIS=AbbreviatedInjuryScore;MVC=Motorvehiclecollision;MCC=motorcycle collision;MV=motorvehicle. Statisticalanalysis Table2 Pelvicinjuryandsurgeryrelateddata. Statisticalanalysiswasperformedbyanexperiencedbiostatis- tician(A.H.)usingSPSS!23.0(Chicago,IL,USA).Categoricaldata arepresentedascount(percent).Continuousdataarepresentedas mean("standarddeviation).Thedataweredividedtopatientswith intactanddeficientneurologicalexaminationatfinalfollow-up.All thecollectedvariableswerecomparedbetweenthesetwostudy groups.Comparisonsbetweencontinuousvariablesweredonebythe Wilcoxon!Mann!Whitneyranksumtest.Comparisonsbetween categoricaldataweredonewithchi-squaretestortheFisherexact test.Thelatertestwasusedifexpectedcountwaslessthanfiveinany cell.Allp-valuesreportedaretwo-sided. Neurologically intactPostOp (N=86) Neurological deficitPostOp (N=4) P-value Sideofzone2fracture Left Right Bilateral Fracturepattern Simple Comminuted Fixationmethod ORIFandplate CRPPandscrew Typeofscrews Sacroiliacscrews Trans-sacralscrews Numberofscrews 1screw 2screws 3screws 4screws Typeofscrewthreads Partiallythreaded Fullythreaded 42(48.8%) 33(38.4%) 11(12.8%) 2(50.0%) 2(50.0%) 0(00.0%) 0.886 57(66.3%) 29(33.7%) 0(0.0%) 4(100.0%) 0.016 5(5.8%) 81(94.2%) 2(50.0%) 2(50.0%) 0.001 Results 35(43.2%) 46(56.8%) 0(00.0%) 2(100.0%) 0.506 Initialdatareviewincluded100patientswithzone2sacral fractures.Afterreviewingthepatients’data,sevenpatientswere excludedbecauseoflackofneurologicalexaminationatfollow-up. Theseincludedonepatientthatdiedshortlyafteradmission,five patientsthatweretransferredintubatedandfollowedatanother hospitalandonepatientthathadanabovekneeamputationthe samesideasthesacralfracture.Threeadditionalpatientswere 48(59.3%) 25(30.9%) 5(6.2%) 3(3.7%) 2(100.0%) 0(00.0%) 0(00.0%) 0(00.0%) 0.717 80(98.8%) 1(1.2%) 1(50.0%) 1(50.0%) 0.049

  3. 1571 A.Hermanetal./Injury,Int.J.CareInjured47(2016)1569–1573 Table3 Neurologicalexaminationofpatientswithneurologicaldeficit. Ofpatientswithcomminutedfracturethosewithneurological deficitweremorecommonlyfixedopenreductionandinternal platefixation(twopatients50.0%)thanpatientsthatwere neurologicallyintact(fivepatients,5.8%).Thisdifferencewas foundtobestatisticallysignificant(p-value=0.001). Sacroiliacscrewsalonewereusedtofixthesacralfracturesof 35patients(42.16%).In48patients(58.84%),trans-sacralscrews wereusedforfracturefixation,eithercombinedwithsacroiliac screwsorassolefixation.Nostatisticallysignificantdifferencewas foundbetweenthesetwogroups(p-value=0.506,seeTable2). Percutaneousscrewfixationwasperformedin83patientsand partiallythreadedscrewswereusedin81(97.6%)ofthese.Only one(1.2%)ofthese81patientshadneurologicaldeficitatfinal follow-up,butthisdeficitwaspresentpre-operatively.Therewere nononunionsrecordedinthiscohort. Firstavailableexamination Lastfollow-upexamination TA 3 2 3 3 EHL 3 2 NA 3 FHL 4 NA NA 3 GS TA 4 2 4 4 EHL 1 2 1 4 FHL 5 5 4 4 GS 5 5 5 4 Patient1 Patient2 Patient3 Patient4 4 NA 3 3 NA=Not FHL=Flexorhallucislongus,GS=Gastrocnemius-Soleus. available. TA=Tibialis anterior, EHL=Extensor hallucis longus, Ofthefourpatientswithdeficitatfinalfollow-upallhadTibialis Anterior(TA)andextensorhalucislongus(EHL)motorstrengthof lessthanfive(outoffive).Twopatientshadeitherflexorhallucis longusorGastrocnemius-soleuscomplexwithstrengthoffouror less(offive).Onepatientalsoexperiencedasensorydeficit.Most patientshadsomerecoveryoftheirinitialexamination(seeTable3). Correlationofassociatedinjuriesandneurologicdeficitafter sacralfracturewasperformedusingtheabbreviatedinjuryscore (AIS,Table1).FortheentirepatientcohortthemeanAIS! abdomenwas2.43("0.689).ThemeanISSfortheentirepatient cohortwas22.72("10.63).TherewasastatisticaltrendforhigherISS inneurologicallydeficientpatients(p-value=0.087). Fiftysevenpatients(66.3%)hadsimplepatternfractures(Fig.1) and33patients(36.7%)hadcomminutedfractures(Fig.2).Allfour patientswithneurologicaldeficithadacomminutedfracture pattern.Ofthe86patientswithoutneurologicaldeficit,29patients (33.7%)and57(66.3%)hadcomminutedorsimplefracture patterns,respectively.Theassociationbetweencomminuted fracturesandneurologicaldeficitwasfoundtobestatistically significant.(p-value=0.016,Table2). Discussion Thedatapresentedsupportsahigherincidenceofneurologic injurywithcomminutedzoneIIfracturesthansimplefractures. Surgicalfixationwithpartiallythreadedsacralandtrans-sacral screwsdidnotresultiniatrogenicneurologicinjuryevenin communitedfractures. Previousworksdescribedtheincidenceofneurologicalinjury aftersacralfracturestobeashighas21!28%[2,5].Themost commoninjurypatterndescribedwasasensory-motordeficit[5]. Zone2sacralfracturesaremostlyassociatedwithsciatic-like nerveinjuryanddrop-foot–injurytotheL5-S1nerveroots.Inthis series,theincidenceofneurologicinjury(4.4%)islowerthan previouslyreported. Ithasbeenreportedthatallpatientsshowimprovementofat leastonegradeofmusclefunctionand53%havecomplete Fig.1.ACTofa54-year-oldmalethatwasinjuredfallingfrom10feet.Hehadazonetwosimplefracture–theforaminalinvolvementwasnotcomminutedalthoughsome comminutionexistsinzone1.Hewastreatedbyclosedreductionandinternalfixationusingatransacralscrewthatproducedfixation.(b)(c)presentthesixmonthsfollow- uppelvisoutletandinletx-rays.Bothcompressionacrossthefractureandunioncanbeseen.Atthistime,heisneurologicallyintactandpainfree.

  4. 1572 A.Hermanetal./Injury,Int.J.CareInjured47(2016)1569–1573 Fig.2.A39-year-oldmalethatwasinjuredinamotorvehiclecollision.(a)anaxialCTinwhichthecomminutioninvolvestheneuralforamincanbeseenwithafragmentin theforamina.HeinitiallypresentedwithmotorfunctionofthreeoutoffiveinTA,EHL,FHLandGS.Hewastreatedbyopenreduction,decompressionlaminectomyand internalfixationbytwotensionbands.(b)and(c)presentshisinletandoutletpelvisx-rayat1yearfollow-up.HerecoveredtofouroutoffiveinTA,EHL,FHLandGSbut remained0/5inperonealstrength. neurologicalrecovery[5].Inourpatient,cohortonepatienthad neurologicalrecoveryandthatafterhehadsacrallaminectomy anddecompressionduringhisopenreductionandinternalfixation (Fig.2). Vaccaroetal.andRouttetal.havesuggestedthatzone2sacral fracturesshouldbefixedusingfullythreadedsacralscrewstoavoid neuroforaminalcompressiongeneratedbypartiallythreaded screwsandresultantiatrogenicnerveinjury[16,17].Concise scientificstudyofthisassertionislacking.Datapresentedinthis cohortdoesnotsupportthesepriorconcernsasnopatientwith comminutiondevelopedapostoperativeneurologicinjury.Addi- tionally,thisseriessupportsthatsurgicalstabilizationwithpartially threadedsacralandtrans-sacralscrewsyielded100%unionrate. Minetal.reportedon35patientswithZone2sacralfractures thatweretreatedwithpartiallythreadedsacralscrews.Theydid notfindanynewneurologicaldeficitthatcouldbeattributedtothe compressionscrews[20].Theydidnotstudyotherriskfactorssuch ascomminutionandtheyhadasmallcohortof35patientsthathad Zone2sacralfracture. Ourdatasuggestthatneurologicdeficitisinjuryrelatedand thatitdependsonthecomminutionofthefracturethatis determinedatinjury.Strengtheningthisconclusionisthefactthat neurologicallyinjuredpatientshadhigherscoresofabdomenAIS andISS.Thissuggeststhattheseweremoreseverelyinjured patients.Wedidnotrecognizeasinglepatientthathadanintact neurologicalexaminationuponadmissionandhadaneurological deficitaftersurgery. Ourstudyhasseveraldrawbacks;thefirstisthatitisa retrospectivestudybasedonclinicalrecordssomeofwhichsome recordsmightbeincompleteorbiased.Severalpatientswere intubateduponarrivalwhichmakesitimpossibletodetermine theirneurologicalstatusatarrival.However,intubationupon arrivalisinherenttoapopulationofseverelyinjuredpatientsata referraltraumacenter.Thesepatientscannotbeexcludedifatrue representationofthesacralfracturepopulationistobeconsidered. Furtherstudiesarerequiredtoconfirmourresults.More specifically,wewouldbeinterestedinarandomizedtrail comparingtheresultsbetweenpartiallythreadedandfully threadedscrews,focusingbothonneurologicstatusandunion rateaftersurgicalfixationofzone2sacralfractures. Conflictsofinterest Nonedeclared. References [1]GansslenA,PohlmannT,PaulCH,LobenhofferPH,TscherneH.Epidemiologyof pelvicringinjuries.Injury1996;27(Supp1):13–20. [2]MehtaS,AuerbachJ,BornC,ChinK.Sacralfractures.JAmAcadOrthopSurg 2006;14:656–65. [3]DenisF,DavisS,ComfortT.Sacralfractures:animportantproblem.Retro- spectiveanalysisof236cases.ClinOrthopRelRes1988;227:67–81. [4]GibbonsK,SoloniukD,RazackN.Neurologicalinjuryandpatternsofsacral fractures.JNeurosurg1990;72:889.

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