Rev. bras. ortop. vol.50 número1

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w w w . r b o . o r g . b r

Original

article

Is

there

a

difference

in

the

positioning

of

sliding

screws

between

stable

and

unstable

extracapsular

fractures?

夽

Pedro

José

Labronici

a,∗

,

Rodrigo

Freitas

da

Silva

a

,

Ana

Maria

Santos

Viana

a

,

Saulo

Santos

Blunck

a

_,

_José

_Sergio

_Franco

b

_,

_Sergio

_Ricardo

_Neto

a

_,

Robinson

Esteves

Santos

Pires

c,d

,

Roberto

Canto

e

a_Prof._Dr._Donato_D’Ângelo_Orthopedics_and_Traumatology_Service,_Hospital_Santa_Teresa,_Petrópolis,_RJ,_Brazil

b_Department_of_Orthopedics_and_{Traumatology,}_School_of_Medicine,_Federal_University_of_Rio_de_Janeiro,_Rio_de_Janeiro,_RJ,_Brazil c_Federal_University_of_Minas_Gerais,_Belo_Horizonte,_MG,_Brazil

d_Hospital_Felício_Rocho,_Belo_Horizonte,_MG,_Brazil e_University_of_Uberlândia,_Uberlândia,_MG,_Brazil

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received3January2014 Accepted27February2014 Availableonline24February2015

Keywords:

Femoralfractures Hipfractures Bonescrews

a

b

s

t

r

a

c

t

Objective:Toanalyzethetip–apexdistance(TAD),cervicodiaphysealangleandGardenangle instableandunstableextracapsularfracturesofthefemurtreatedwithaplateandsliding screw.

Method:Hipradiographsinanteroposterior(AP)andlateralviewon117patientswere eval-uated.Thefractureswereclassifiedasstableorunstable,usingtheAOclassification,and thereductionachievedwasassessedinaccordancewiththefollowingcriteria:TAD>3cm; Gardenalignmentindex(AP)<160◦_;_and_AP_{cervicodiaphyseal}_varus_angle_<₁₂₅◦_._When_two

ormorecriteriawerepresent,thequalityoftheosteosynthesiswasclassifiedas“notideal”.

Results:ThepatientswithunstablefracturespresentedAPcervicodiaphysealanglesthat weresignificantlygreater(p=0.05)thaninthosewithstablefractures.Thepatientswith unstablefracturespresentedlateralcervicodiaphysealanglesthatweresignificantlysmaller (p=0.05)thaninthosewithstablefractures.Therewerenosignificantdifferencesinthe remainderofthecriteriaevaluated.

Conclusion:Thisstudydidnotfindanysignificantdifferencesinthemeasurements evalu-ated,exceptinrelationtothecervicodiaphysealangle.Satisfactoryreductionwasachieved bothforthestableandfortheunstablefractures,whenweusedaplateandslidingscrew totreatproximalextracapsularfracturesofthefemur.

夽

WorkdevelopedattheProf.Dr.DonatoD’ÂngeloOrthopedicsandTraumatologyService,HospitalSantaTeresa,andatthePetrópolis SchoolofMedicine,Petrópolis,RJ,Brazil.

∗ _{Corresponding}_author_.

E-mail:plabronici@globo.com(P.J.Labronici).

http://dx.doi.org/10.1016/j.rboe.2015.02.002

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Existe

diferenc¸a

no

posicionamento

do

parafuso

deslizante

entre

as

fraturas

extracapsulares

estáveis

e

instáveis?

Palavras-chave:

Fraturasdofêmur Fraturasdoquadril Parafusosósseos

r

e

s

u

m

o

Objetivo: Analisaradistânciaponta-ápice(DPA),oângulocervicodiafisárioeoângulode Gardenemfraturasextracapsularesinstáveiseestáveisdofêmurtratadascomplacae parafusodeslizante.

Método: Foramavaliadasradiografiasdoquadrilnasincidênciasemanteroposterior(AP) eperfilde117pacientes.Asfraturasforamclassificadascomoestáveiseinstáveis,pela classificac¸ãoAO,eareduc¸ãoobtidafoiavaliadadeacordocomoscritériosdedistância ponta-ápice(DPA>3cm),índicedealinhamentodeGarden(AP)<160◦_e_ângulo

cervicodi-afisário(AP)emvaro<125◦_._Quando_dois_ou_mais_critérios_estavam_presentes,_a_qualidade

daosteossíntesefoiclassificadacomo«nãoideal».

Resultados: OspacientescomfraturainstávelapresentaramCDAP(p=0,05) significativa-mentemaiordoqueosestáveis.Ospacientescomfraturainstável apresentaramoCD Perfil(p=0,05)significativamentemenordoqueoscomfraturaestável.Nãohouvediferenc¸a significativaentreorestantedoscritériosavaliados.

Conclusão: Esteestudonãoencontroudiferenc¸asignificativaentreasmedidasavaliadas, excetooângulocervicodiafisário.Foiconseguidaumareduc¸ãosatisfatória,tantonas frat-urasestáveiscomonasinstáveis,quandousamosplacaeparafusodeslizantenasfraturas proximaisextracapsularesdofêmur.

Introduction

Plates and sliding screwsare currently the implants most oftenusedforfixation ofintertrochantericfractures ofthe femur.1_This_is_because_of_an_intrinsic_{characteristic}_of_their

design,whichmakesitpossibletocollapsethefracturewith controlledimpactionintoastableposition,while maintain-ingaconstantcervicodiaphysealangle,withoutpenetration ofthefemoralhead.2–4 _The_plate_and_sliding_screw_join_the

limbtogetherwithoutmakingcuts,soastoresistpenetration andthethreadedscrewincreasesthefixationintheproximal fragment.Thegreatadvantageofthisisthatthescrewcan beinserteddeeplywithoutanydangerthatthejointmight becomeperforatedlateron,althoughtheplacementneedsto bepreciseinordertoavoidfailures.5

Themostcommon cause offailure offixationof extra-capsular fractures that are treatedwith plates and sliding screwsrelatestosituationsinwhichthescrewinthefemoral headcutsout.The incidenceofthissituation ranges from 5.3%to16.8%.1,2,6–8_It_occurs_when_the_{cervicodiaphyseal}_angle

collapsesinvarusandthethreadedscrewextrudessuperiorly throughthefemoralhead.2,3_Baumgaertner_et_al.2_introduced

theconceptofthetip–apexdistance(TAD)asastrong progno-sticfactorforthiscomplication.

TADwasdefinedbyBaumgaertneret al.2 _as_the_sum_of

thedistanceinmillimeters, onradiographsin anteroposte-rior(AP)andlateralviews,fromthetipofthethreadedscrew to the apex of the femoral head, with appropriate correc-tionformagnification.2,6,9_It_has_been_demonstrated_that_TAD

greaterthan2.5cmisassociatedwithincreasedriskofimplant failure2,6,9 _with _greater _occurrence_of_cut-out.1–3,6,9,10 _Some

studieshavesuggestedthatvalueslowerthan2cmoughtto betheideal.1

TheaimofthepresentstudywastoanalyzeTAD, cervi-codiaphysealangleandGardenangleinstableandunstable extracapsularfracturestreatedwithaplateandslidingscrew.

Materials

and

methods

BetweenMay1998andJuly2011,408patientswithunstable and stableextracapsular fractures ofthefemurunderwent surgicaltreatmentbymeansofreductionandfixationusing aplateandslidingscrewatHospitalSantaTeresa, Petrópo-lis,stateofRiode Janeiro.Amongthese,291patientswere excludedbecausetheypresentedradiographswithincorrect viewsordidnotpresentoneoftheviewsneededfor analy-sisontheTADmeasurements;orbecausetheywereunder60 yearsofage;orbecausetheypresentedpathologicalfractures andtreatmentwithcephalomedullarynails.Allthepatients wereoperatedonatractiontable.

Thetechnicalqualityoftheosteosynthesiswasanalyzed by means of observation and using radiographs produced during the immediate postoperative period. According to Baumgaertneretal.2,6 _TAD_was_described_as_the_sum_of_the

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Fig.1–Stableintertrochantericfractureofthefemurtreatedwithaplateandslidingscrew.

indicatesthedegreeofrotationofthefemoralhead.Inthe anteroposterior projection, the cervicocephalic trabeculae formanangleof160–175◦ _with_the_medial_cortical_bone_of

thefemoraldiaphysis;inthelateralprojection,thealignment ofthetrabeculaeshouldbe180◦_._From_the_Garden_alignment

index,adequatereductionistakentobeatrabecularangleof between160◦_and₁₈₀◦_,_both_in_AP_and_in_lateral_view.

TheAOclassificationforhipfractureswasused,12_and_this

wassubdividedintostablefractures(31A1)orunstable frac-tures(31A2)(Figs.1and2).Thequalityoftheosteosynthesis wasclassifiedas“ideal”or“notideal”,inaccordancewiththe followingcriteria:(1)TAD>3cm;(2)Gardenalignmentindex (AP)<160◦_;_and₍₃₎_{cervicodiaphyseal}_angle_(AP)_in_varus_<₁₂₅◦_.

Whentwoormorecriteriawerepresent,thequalityofthe osteosynthesiswasclassifiedas“notideal”.

Table1presentsthecharacterizationofthemean,standard

deviation(SD),medianandminimumandmaximumofthe numericalvariablesofthetotalsampleofthisstudy.

Amongthe 117 records examined, 74 (63.2%) related to unstablefractures,59(50.4%)tofracturesontherightsideand 66(56.4%)tofracturesinfemales.

Table1–Descriptionofthenumericalvariablesinthe

totalsample.

Variable Mean SD Median Minimum Maximum

AP 1.21 0.43 1.20 0.20 2.50

Lateral 1.18 0.44 1.10 0.10 2.20

TAD 2.39 0.84 2.20 0.30 4.10

GardenAP 162.7 8.4 162 125 178

Gardenlateral 173.1 4.8 174 160 180

CDAP 135.5 11.3 134 112 170

CDlateral 171.5 5.8 172 150 180

Source:HospitalSantaTeresa,Petrópolis,stateofRiodeJaneiro, Brazil.

SD,standarddeviation;AP,anteroposterior;TAD,tip–apexdistance; CD,cervicodiaphysealangle.

Statistical

methodology

Thedescriptiveanalysispresentedtheobserveddataintables, intheformofmeans,standarddeviationsandmedians.

The inferential analysis consistedofthe nonparametric Mann–Whitney test for comparing the numerical variables betweenthesubgroupsofstableandunstablefracturesand the2(Chi-square)testforcategoricalvariables.

A nonparametric method was used because the vari-ables didnotpresent normal(Gaussian) distribution,given that the hypothesis ofnormality wasrejected through the Kolmogorov–Smirnovtest.

Thecriterion used fordeterminingsignificancewas the levelof5%.Thestatisticalanalysiswasprocessedusingthe SAS6.11software(SASInstitute,Inc.,Cary,NC,USA).

Results

Toshowanydifferencesamongthestudyvariables,Table2

presents themeans,standard deviations(SD)andmedians of the variables according to stability (unstable or stable) and the corresponding descriptive level (p-value) from the Mann–Whitneytest.

Itwasobservedthattherewerenosignificantdifferences inthevariablesstudiedbetweenthetwogroupsoffractures, asillustratedinFigs.3–5.

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Fig.2–Unstableintertrochantericfractureofthefemurtreatedwithaplateandslidingscrew.

similartothatofthesubgroupwithstablefractures(60.5%), withp=0.50.

It was also observed that there were differences in the study variables between the two groups of fractures (unstableand stable),separately accordingto side(rightor left).

Tables 3 and 4 presented the means, standard

devia-tions(SD)andmediansofthevariablesaccordingtostability (unstableorstable)andthecorrespondingdescriptivelevels (p-values) ofthe Mann–Whitney test,for theleft and right sides,respectively.

Itwasobservedthatthepatientswithunstablefractures presented AP cervicodiaphyseal angles that were signifi-cantlygreaterthanthoseofthepatientswithstablefractures (p=0.05),asshowninFig.6.Therewerenostatistically sig-nificantdifferencesin theother variables betweenthetwo subgroups.

Itwasalsoseenthatthepatientswithunstablefractures presentedlateralcervicodiaphysealanglesthatwere signifi-cantlysmallerthanthoseofthepatientswithstablefractures

Stable fracture Unstable fracture

180

170

160

150

140

130

120

Garden (degrees)

Lateral AP

Fig.3–Comparisonbetweenstableandunstablefractures usingtheGardenangle.

Table2–Analysisonvariablesaccordingtostability.

Variable Unstable(n=74) Stable(n=43) p-Valuea

Mean±SP Median Mean±SD Median

AP 1.23±0.43 1.2 1.17±0.43 1.2 0.58

Lateral 1.22±0.44 1.1 1.11±0.45 1 0.19

TAD 2.45±0.83 2.2 2.28±0.85 2.2 0.33

GardenAP 163.0±8.8 164 162.1±7.9 162 0.32

Gardenlateral 172.8±5.0 174 173.7±4.4 174 0.44

CDAP 135.6±11.6 133 135.5±10.8 134 0.87

CDlateral 170.7±6.5 170 172.9±4.1 172 0.093

Source:HospitalSantaTeresa,Petrópolis,stateofRiodeJaneiro,Brazil.

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Table3–Analysisonthevariablesaccordingtothestabilityoftherightside.

Mean±SP Median Mean±SP Median

AP 1.20±0.44 1.2 1.13±0.37 1.15 0.66

Lateral 1.17±0.40 1 1.04±0.36 1.05 0.38

TAD 2.37±0.79 2.2 2.17±0.67 2.25 0.46

GardenAP 164.3±7.2 164 161.9±6.3 162 0.21

Gardenlateral 173.1±4.9 174 173.6±4.3 174.5 0.81

CDAP 137.0±11.4 135 131.4±7.6 128 0.053

CDlateral 171.9±5.4 172 172.9±3.7 172.5 0.50

AP,anteroposterior;TAD,tip–apexdistance;CD,cervicodiaphysealangle;SD,standarddeviation. a _{Mann–Whitney}_test.

180

170

160

150

140

130

120

110

100

CD (degrees)

Lateral AP

Fig.4–Comparisonbetweenstableandunstablefractures usingthecervicodiaphysealangle(CD).

(p=0.05),asshowninFig.6.Therewerenostatistically sig-nificantdifferences intheother variables betweenthe two subgroupsofpatients.

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

TAD

Fig.5–Comparisonbetweenstableandunstablefractures usingthetip–apexdistance(TAD).

The subgroup with unstable fractures was seen to present lateral cervicodiaphyseal angles that were signifi-cantlysmallerthanthoseofthesubgroupwithstablefractures (p=0.05),asshowninFig.7.Therewerenostatistically

sig-Table4–Analysisonthevariablesaccordingtothestabilityoftheleftside.

Mean±SP Median Mean±SP Median

AP 1.28±0.42 1.2 1.20±0.48 1.2 0.61

Lateral 1.28±0.47 1.2 1.15±0.51 1 0.28

TAD 2.56±0.87 2.4 2.35±0.96 2.1 0.34

GardenAP 161.5±10.3 164 162.3±9.0 162 0.96

Gardenlateral 172.5±5.1 172 173.8±4.5 172 0.33

CDAP 133.8±11.7 130 138.4±11.9 140 0.19

CDlateral 169.2±7.5 170 172.8±4.5 172 0.058

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180

175

170

165

160

155

150

145

140

135

130

125

CD (degrees)

Lateral AP

Fig.6–Comparisonbetweenstableandunstablefractures usingthecervicodiaphysealangle(CD),rightside.

180

175

170

165

160

155

150

145

140

135

130

125

CD

(degrees)

Lateral AP

Fig.7–Comparisonbetweenstableandunstablefractures usingthecervicodiaphysealangle(CD),leftside.

nificantdifferencesin theother variables betweenthetwo subgroupsatthe5%level.

Fig.8showstheincidenceofthestableandunstable frac-turesrelatingtothe117patientsanalyzed.

Fig.9showstheidealandnon-idealreductionsinthestable andunstablefractures.

Itwasseenthat79%ofthestablefracturesand81%ofthe unstablefracturespresentedidealreductions.

Discussion

Inoursetting,themajorityofintertrochantericfracturesare still treated using plates and sliding screws. The success of treatments using this type of implant depends on the impactionofthe headand necksegments intheproximal

0% 10% 20% 30% 40% 50% 60% 70%

Stable n=43 Unstable n=74

Fig.8–Comparisonofabsolutenumbersbetweenstable andunstablefractures.

regionofthefemur,intoastableposition.Afterthishasbeen achieved,theloadonthefracturewillbesharedbetweenthe boneandimplantandthebonewillabsorbapproximately75% ofthe load transmitted.13 _Kaufer14 _described _five_variables

thatcouldaffecttheresistanceofthecombinationofimplant andfracturefragment:(1)bonequality;(2)fragment geome-try;(3)fracturereduction;(4)implantmodel;and(5)implant choice.Amongthese,thelastthreeareunderthecontrolof thesurgeon.Accordingtotheliterature,complications relat-ingtotheplateandslidingscrewoccurinaround16–23%of thecases.Therefore,adequateplacementofthescrewis fun-damentallyimportant.15–17_These_{complications}_may_include

lossofthereduction,pseudarthrosis,skewedconsolidation withvarusdeformityofthefemoralneck,shorteningorscrew cut-out.7,16,18–23_Our_main_objective_here_was_to_analyze_the

positionsoftheplate andslidingscrewthroughcomparing stableandunstableintertrochantericfractures.

Despitethemechanicaladvantagesofplatesand sliding screws,slidingscrewcut-outremainsasignificantproblem, especially incasesof unstable fractures.However,internal

0 10 20 30 40 50 60 70 80

Stable Unstable

Non-ideal reduction Ideal reduction

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fixationofstableintertrochantericfractureshasshownlow incidenceofcomplications.5,7,24

Many authors have triedto quantify the positioning of theslidingscrew.25–27_Clawson5_recommended_that_the_screw

should be placed6mm from the subchondral bone. Some authorshavedescribedthelocationofthescrewinrelation tothedistancefromthecentralaxisofthefemoralheadand neck,onAPandlateralradiographs.25–27_The_screw

penetra-tiondepth hasbeen calculatedaccordingtothenumber of turnsthatwouldbeneededtoadvancethescrewinsidethe bone.Thenine-zonesystemusedbyKyleetal.24_did_not

rep-resentthescrewpenetrationdepth.Larssonetal.28_took_into

considerationthedirectionanddepthofthescrewanddivided thefemoralheadintoperpendicularaxesandtheremaining quadrantsinto11 zonesinbothradiographs.Bridleet al.29

usedsimilaraxes,butdividedeachradiographintonineareas. Parker30_used_a_proportional_technique_for_defining_the

direc-tionofthescrew,butnotitsdepth,inbothradiographicviews. The two mainmethods forquantifying the positioning ofthe screwthathavebeendescribed are theproportional methoddescribedbyParker30_and_the_tip–apex_distance_(TAD)

methoddescribedbyBaumgaertneretal.,apudEvans31_and

Garden.32_The_latter_method_has_been_shown_to_be_a_useful

intraoperativeindicatorforscrewpositioningatdepthandfor centralplacementinthe femoralhead.Thisisperhapsthe mostimportantindicatorforpreciseplacementofthescrew and hasbeen shown in several studies tohave prognostic value after treatments for intertrochanteric fractures.2,17,33

TAD<2.5cmhasbeenreportedtorepresentagood progno-sisfortheresults.However,somestudieshavetakentheview thattheidealwouldbeTAD<2cm.2,17,33

Several authors have reported that failures are practi-cally nonexistent in relation to fixation of stable two-part intertrochantericfractures.7,34_The_most_common_mechanical

complicationafterusingaplateandslidingscrewis progres-sivecollapseinvarusthroughthefemoralhead,withproximal migrationandpossiblyscrewcut-outinthehead.6,7_Adequate

positioningofthescrewinsidetheheadprotectsagainstthese complications.6,7 _Nonetheless, _divergences_of_opinion _exist

inrelationtoinstability.26,34–36_Lindskog_and_Baumgaertner37

demonstratedthatageandunstablefractureswerealso inde-pendent factors for a prognosis of cut-out. Baumgaertner etal.6 _reported_cut-out_rates_ranging_from _4%_to_20%,_with

higherratesinunstable fractures.Haidukewych38 _reviewed

unstablefractures (AO/OTAtypesA3.1 andA3.3)and found complicationrates ofup to56% (consistingof cut-outand pseudarthrosis)whenaplate and slidingscrewwere used. Ourresultsshowedthattherewasnosignificantdifference inTADbetweenstablefractures (2.28±0.85cm) and unsta-blefractures(2.45±0.83cm).OurTADresultsof2.39±0.84cm remainedwithinthelimitdeterminedbyBaumgaertner,i.e. below2.5cm.OurdatadonotsupportthehypothesisthatTAD mightbehigher(therebyfavoringcomplications)incasesof unstablefracturesbecauseofpossibledifficultyinreducing suchfractures.

Studiesoncadaversandradiographicstudieshave demon-stratedthatthemeancervicodiaphysealangleinthegeneral populationis127±7◦_.39,40 _No_significant_differences_in

rela-tion to side and gender have been demonstrated, despite culturaldifferences.41_The_AP_radiographic_evaluation_of_the

cervicodiaphysealanglewasshowntobemoreprecisewhen thefemurwasinternallyrotatedat10◦_,_given_that_external

rotationmightleadtoanapparentincreaseinthe cervicodi-aphysealangle.42_The_present_study_demonstrated_that_good

reductionisanimportantfactorforavoidingcomplications. However,sincenointra-orinterobservercomparisonswere made,wecannotconcludethattherewasnosignificant differ-enceincervicodiaphysealangleonAPradiographs,between stableand unstablepatients(135.5±10.8◦ _and_135.6_±_11.6◦_,

respectively),oronlateral-viewradiographs(172.9±4.1◦ _and

170.7±6.5◦_,_{respectively).}

Somestudieshaveindicatedthatcorrectreductionof frac-tures seenonradiographs, especiallyinAPview,and good correctionofthetrabecularangletoaround165–170◦_are

asso-ciatedwithreductionoftheriskofcut-out.41,43_Pervez_et_al.1

confirmedthevalueoffracturereductiononradiographsinAP view,withanincreaseincut-outratesincasesoffracturesthat had beenreducedinvarus.Fracture reductionand implant positioningaredirectlyrelated.Therefore,correctreduction ofthefractureisaprerequisiteforimplantplacement.44

WeobservedthatthecervicodiaphysealangleinAPview wassignificantlygreaterinunstablefracturesandthatthere wasatendencytowardreductioninvalgus.Wealsoobserved inlateral viewthat thecervicodiaphysealanglewas signif-icantly smallerinunstable fractures,which suggestedthat therewasatendencytowardposteriorcollapse.

Conclusion

Theresultsfromthisstudyconfirmedthatthereareno sig-nificant differences between the measurements evaluated, exceptthecervicodiaphysealangle.Moreover,bothforstable andforunstablefractures,goodreductionisanimportant fac-torforavoidingcomplicationswhenplatesandsidingscrews areusedforextracapsularfracturesofthefemur.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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