Rev. bras. ortop. vol.50 número5

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

Original

article

Experimental

trial

on

surgical

treatment

for

transverse

fractures

of

the

proximal

phalanx:

technique

using

intramedullary

conical

compression

screw

versus

lateral

compression

plate

夽

Daniel

Schneider

Ibanez

∗

_,

_Fabio

_Lucas

_Rodrigues,

_Rafael

_Salmeron

_Salviani,

Fernando

Augusto

Reginatto

Roberto,

Jose

Roberto

Pengo

Junior,

Marcio

Aurelio

Aita

LaboratóriodeEnsaiosMecânicoseMetalográficos(LEMM),Jaú,SP,Brazil

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t

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Articlehistory:

Received17June2014 Accepted25August2014 Availableonline1August2015

Keywords:

Bonefixation

Internalfixationoffractures Handinjuries

Fingerinjuries

a

b

s

t

r

a

c

t

Objective:Tocomparethemechanicalparametersbetweentwomethodsforstabilization throughcompression:1.5mmaxialcompressionplateversusconicalcompressionscrew usedasanintramedullarytutor.

Methods:Polyurethanemodels(Sawbone®₎_that_simulated_transverse_fractures_of_the

prox-imalphalanxwereused.Themodelsweredividedintothreegroups:lateralplate,conical screwandnoimplant.

Results:Greater force was needed to result in fatigue in the synthesis using an intramedullaryplate.Thus,thismodelwasproventobemechanicallysuperiortothemodel withthelateralplate.

Conclusion: StabilizationusingtheAcutrak®_screw_for_treating_fractures_in_the_model_used

inthistrialpresentsmechanicalresultsthatarestatisticallysignificantlysuperiortothose fromtheaxialcompressiontechniqueusingthelateralplate(AptusHand®_).

Ensaio

experimental

para

tratamento

cirúrgico

das

fraturas

transversas

da

falange

proximal

–

Técnica

com

parafuso

intramedular

cônico

de

compressão

versus

placa

de

compressão

lateral

Palavras-chave:

Fixac¸ãoóssea

Fixac¸ãointernadefraturas

r

e

s

u

m

o

Objetivo:Compararosparâmetrosmecânicosentredoismétodosdeestabilizac¸ãopor com-pressão:placadecompressãoaxialde1,5mmcomoparafusocônicodecompressãousado comotutorintramedular.

夽

WorkdevelopedintheLaboratóriodeEnsaiosMecânicoseMetalográficos(LEMM),Jaú,SP,Brazil.

∗ _{Corresponding}_author_.

E-mail:drdanielsi@hotmail.com(D.S.Ibanez).

http://dx.doi.org/10.1016/j.rboe.2014.12.009

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Traumatismosdamão Traumatismosdosdedos

Métodos: Foramusadosmodelosde poliuretano(Sawbone®)quesimulama fraturada falangeproximaltransversa,divididosemtrêsgrupos(placalateral,parafusocônico,sem implante).

Resultados: Hánecessidadedeumamaiorforc¸apararesultarnafadigada síntesecom parafusointramedular.Comprova-se,assim,asupremaciamecânicadessesobreomodelo comaplacalateral.

Conclusão: Aestabilizac¸ãocomoparafusoAcutrak®,notratamentodasfraturasnomodelo adotadonesteensaio,apresentaresultadosmecânicossuperioreseestatisticamente sig-nificativosemcomparac¸ãocomatécnicadecompressãoaxialcomousodaplacalateral (AptusHand®).

Introduction

Fractureofthephalangesarefrequentinjuriesandaccount for6%ofallfractures.1,2 _The_proximal_phalanx_is_fractured morefrequentlythanthemiddleordistalphalanges.3,4

Indicationsforsurgicaltreatmentforthesefracturesneed to take into consideration the type of fracture line, the displacement between the fragment and the difficulty in maintainingclosedreductionofthefracture.3_The_aim_of sur-gicaltreatmentistorestoretheanatomyandfunctionofthe affectedfinger.4,5

Thetechniquesthathavebeendescribedrangefrom seek-ingrelativestability totheprincipleofabsolutestability. A combinationofmethodsissometimesnecessary,6 _and_this dependsonthenatureofthefractureline,theavailabilityof implantsandthesurgeon’spreference.

Among the surgical complications, the following can be highlighted: joint stiffness, adherence and/or tearing of the extensor tendon,1 _functional _loss _of _the _finger2 _or, additionally, skewed consolidation, pseudarthrosis and osteomyelitis.5–7

Thesecomplicationsareoftencausedbypoorknowledge ofthebiomechanicsofthisorgan;anunfoundedbeliefthat allfracturesofthehandcanberesolvedthroughconservative treatment;orpoorcooperationfromthepatient.8

Inseekingtominimizethesecomplications,Mantovanni etal.9_described_lateral_positioning_of_the_plate_in_which_the extensortendon wasleft untouched soasto avoidtendon adherenceandjointstiffness.Anotheroptionwouldbetouse theprincipleofanintramedullaryinternaltutor,10,11_such_as aconicalcompressionscrew(Acutrak®_),_to_be_placed percuta-neously.Wedescribethisnoveltechniqueinthepresentstudy. Theobjectiveofthisstudywastocomparethemechanical parameters of two methods of stabilization through com-pression:a1.5mmaxialcompressionplateversusaconical compressionscrewusedasanintramedullarytutor.Bothof thesemethodswereusedonfracturesofthediaphysisofthe proximalphalanxthatfollowedatransverseline.

Methods

Thisstudy was conductedin the Mechanical and Metallo-graphicTestingLaboratory(LEMM), inthe city ofJaú,state

Fig.1–GroupImodelbeforethemechanicaltest.

Fig.2–GroupIImodelbeforethemechanicaltest.

ofSão Paulo,Brazil,inMay 2012.Thislaboratoryhas been certifiedbyINMETRO.

Fifteenpolyurethanemodelssimulatingtheproximal pha-lanx(Sawbone®_),_of_dimensions₁₀_mm

×8mm×60mmand density 40poundsper cubicfoot (lb/ft3₎_were _used. _Simple transversefractureswithasinglelineataninclinationofless than30◦_were_made.12

Thesemodelsweredividedintothreegroups:fivemodels foreachgroupwithsynthesismaterial(groupsIandII);and threemodelsforagroupwithoutsynthesismaterial(group III).

GroupI_–_with_a_1.5_mm_compression_plate_and_four corti-calscrews(AptusHand®_),_placed_in_the_lateral_region_of_the model(Fig.1).

Group II – one conical compression screw (Acutrak®₎ _of standardtype,positionedintramedullarily(Fig.2).

GroupIII_–_models_of_the_phalanx_without_an_implant_and withoutafracture(Fig.3).

Placement technique for the lateral plate in the polyurethanemodel(Fig.1):

Placementof1.5mmplatepositionedlaterallyinthemodel and,afterreduction,placementoffourbicorticalscrews(two

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Load

h

Test body

Support bearings

L

Load bearing

Fig.4–Illustrativeschematicphotooftheflexiontestwith load-bearingatthreepoints:distanceL:40mm;distanceh:

15mm;forceapplied:5mm.

distallyandtwoproximallytothefracturefocus)thatpromote compressionaxiallytothefractureline.

Placementtechniquefortheintramedullaryconical com-pressionscrewinthepolyurethanemodel(Fig.2):

Reductionofthefractureinthepolyurethanemodeland passageofthe guidewirefrom theupper face towardsthe lowerface,acrossthefracture.Thisisfollowedby measure-mentofthesizeoftheimplant,drillingofanopeninginboth corticesandinstallationofaconicalcompressionscrewjust belowtheuppersurfaceintheregionproximaltothefracture andadjacenttothedistallowersurfaceofthismodel.

Application ofthe mechanical test inthe polyurethane models:flexiontestatthreesupportpoints(Fig.4).

Thepolyurethanemodels(testbodies) wereplacedin a machine(EMIC apparatus,model DL10000)withthree con-tactpoints:oneloadbearingandtwosupportbearings.Inthis manner,theloadwasappliedsoastogenerateaconstantly increasingflexionforceuntilthesynthesismaterialreached fatigue.

Fig.5–Illustrativedetailedschematicphotooftheflexion testwithload-bearingatthreepoints:groupII.

120

100

80

60

40

20

0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Deflection (mm)

Source: Mechanical and metallographic testing laboratory (LEMM)

Force/Load (N)

TB 1 TB 2 TB 3 TB 4 TB 5

Fig.6–Flexiontestcurves,withload-bearingatthree points,forgroupI.

GroupI–forceappliedfromabovetobelow,withthe com-pressionplatepositionedlaterally.

GroupII_–_force_applied_from_above_to_below,_with_the com-pression screwalso placedfrom above to below,inclined accordingtothetransversefractureline(Fig.5).

GroupIII–forceappliedfromabovetobelow,ontheentire testbody.

Inallthegroupsevaluated,thedistanceLbetweenthe sup-portbearingswasthesame.IngroupsIandII,theflexionforce appliedbytheloadbearingwaskeptconstantatadistanceh

of15mmfromthebeginningofthesynthesisandat5mm fromthefractureline.

All the data were sent for statistical analysis. The Kruskal–Wallistestwasusedandthesignificancelevelwas takentobe5%(0.050).TheStatisticalPackagefortheSocial Sciences (SPSS) software, version 21.0,was used to aid in obtainingtheresults.

The Kruskal–Wallis test was applied to ascertain the possible differences between the three groups, compared simultaneously,forthevariablesofinterest.

Results

Ingroup I(lateralcompression plate),themean maximum flexionforcewithstoodwas81.23N,witharangefrom97.13 to73.35N.Themeanrigidityunderflexionwas90.80N,with arangefrom116to70N(Table1andFigs.6and7).

GroupII(intramedullaryconicalcompressionscrew) with-stoodameanmaximumflexionforceof320.40N,witharange from 360.08 to 278.85N. The mean stiffness under flexion was427.48N,witharangefrom455Nto385N(Table2and

Figs.8and9).

GroupIII(entiretestbody)withstoodamean maximum flexionforceof537.50N,witharangefrom545.61to528.68N. Themeanstiffnessunderflexionwas492N,witharangefrom

499Nto480N(Table3andFig.10).

Description and comparisonof the variables of interest betweenthethreegroupsstudied(Table4).

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Table1–ResultsobtainedfromflexiontestforgroupI.

Item K(N/mm) Ele(Nm2) Q(mm) P(N) R(Nm) Fmax(N)

1 96.0 0.05 0.03 54 0.41 79.05

2 70.0 0.04 47 0.35 73.35

3 116.0 0.07 52 0.39 97.13

4 86.0 0.05 47 0.35 71.36

5 86.0 0.05 49 0.37 85.05

Mean 90.8 0.052 0.030 49.8 0.4 81.2

Standarddeviation 16.89 0.01 3.11 0.02 10.39

Source:MechanicalandMetallographicTestingLaboratory(LEMM).

K,rigidityunderflexion;Ele,structuralrigidityunderflexion;P,plasticflowload;R,momentofflow(resistancetoflexion);q,displacementat

0.2%ofthedistancebetweentheexternalandinternalbearings;Fmax,maximumtestforce.

Table2–ResultsobtainedfromflexiontestforgroupII.

Sample K(N/mm) Ele(Nm2) q(mm) P(N) R(Nm) Fmax(N)

1 434.0 0.24 0.03 250 1.88 360.08

2 455.0 0.26 265 1.99 328.09

3 467.0 0.26 320 2.40 342.55

4 398.0 0.22 250 1.88 278.85

5 385.0 0.22 190 1.43 292.45

Mean 427.8 0.2 0.03 255.0 1.9 320.4

Standarddeviation 35.48 0.02 46.37 0.35 34.03

Source:MechanicalandMetallographicTestingLaboratory(LEMM).

Table3–ResultsobtainedfromflexiontestforgroupIII.

Sample K(N/mm) Ele(Nm2) q(mm) P(N) R(Nm) Fmax(N)

1 480.0 0.27 0.030 430 3.23 528.68

2 499.0 0.28 0.030 420 3.15 545.61

3 497.0 0.28 0.030 410 3.08 538.12

Mean 492.0 0.3 0.030 420.0 3.2 537.5

Standarddeviation 10.44 0.01 0.030 10.00 0.08 8.48

Source:MechanicalandMetallographicTestingLaboratory(LEMM)

Fig.7–IllustrativephotoofgroupIafterthemechanical test.

400

350

300

250

200

150

100

50

0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Deflection (mm)

Force/Load (N)

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Table4–ApplicationofKruskal–Wallistest.

Variable Group N Mean Standarddeviation Minimum Maximum P25 Percentile50(median) P75 Significance(p)

K(N/m) I 5 90.80 16.89 70.00 116.00 86.00 86.00 96.00 0.005 II 5 427.80 35.48 385.00 467.00 398.00 434.00 455.00

III 3 492.00 10.44 480.00 499.00 488.50 497.00 498.00 Total 13 313.00 186.03 70.00 499.00 96.00 398.00 467.00

Ele(Nm2) I 5 0.05 0.01 0.04 0.07 0.05 0.05 0.05 0.005

II 5 0.24 0.02 0.22 0.26 0.22 0.24 0.26

III 3 0.28 0.01 0.27 0.28 0.28 0.28 0.28

Total 13 0.18 0.10 0.04 0.28 0.05 0.22 0.26

q(mm) I 5 0.03 0.00 0.03 0.03 0.03 0.03 0.03 >0.999

II 5 0.03 0.00 0.03 0.03 0.03 0.03 0.03

III 3 0.03 0.00 0.03 0.03 0.03 0.03 0.03

Total 13 0.03 0.00 0.03 0.03 0.03 0.03 0.03

P(N) I 5 49.80 3.11 47.00 54.00 47.00 49.00 52.00 0.005 II 5 255.00 46.37 190.00 320.00 250.00 250.00 265.00

III 3 420.00 10.00 410.00 430.00 415.00 420.00 425.00 Total 13 214.15 152.58 47.00 430.00 52.00 250.00 320.00

R(Nm) I 5 0.37 0.03 0.35 0.41 0.35 0.37 0.39 0.005

II 5 1.92 0.35 1.43 2.40 1.88 1.88 1.99

III 3 3.09 0.06 3.03 3.15 3.06 3.08 3.12

Total 13 1.59 1.12 0.35 3.15 0.39 1.88 2.40

Fmax(N) I 5 81.19 10.39 71.36 97.13 73.35 79.05 85.05 0.005

II 5 320.40 34.03 278.85 360.08 292.45 328.09 342.55 III 3 537.47 8.48 528.68 545.61 533.40 538.12 541.87 Total 13 278.49 184.81 71.36 545.61 85.05 292.45 360.08

synthesismaterials(Tables1and2)andfracturingofthetest bodyingroupIII(Table3).

The study described here did not present any statisti-callysignificantdifferencesincomparingthedifferentmodels simultaneouslyand withineachgroup.For thisreason,the Mann–Whitneytestwasapplied(Table5)toidentifywhich groupsdifferedfromtheothers,whencomparedaspairs.

Withtheexceptionofthevariableq(mm),whichremained constantinthethreegroups,itcanbestatedthatreal differ-encesbetweenthegroupswerepresentinrelationtotheother variablesofinterest.

Fig.9–IllustrativephotoofgroupIIafterthemechanical test.

600

500

400

300

200

100

0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Deflection (mm)

Force/Load (N)

Fig.10–Flexiontestcurves,withload-bearingatthree points,forgroupIII.

Table5–ApplicationofMann–Whitneytest.

Variable Pairofgroups

I_vs.II I_vs.III II_vs.III

K(N/m) 0.009 0.024 0.025

Ele(Nm2) 0.008 0.021 0.023

P(N) 0.009 0.024 0.024

R(Nm) 0.009 0.024 0.024

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Discussion

Fracturesoftheproximalphalanxaremostprevalentamong malesbetweentheagesof10and40years.Theyareusually treatedasinsignificantinjuries,butthisresultsinfunctional limitation4_in_an_economically_important_population.

Evolution in treatments for fractures of the proximal phalanx is a necessity in our setting, given that the inci-dence of this fracture has been increasing exponentially andthepublishedresultsfromtheestablishedmethodsare unconvincing.10_The_ideal,_in_seeking_to_diminish_the postop-erativecomplications,istocombinelessinvasivetechniques withbetterimplantstability,inordertoenableearly mobiliza-tionofthefracturedfinger.

Thenewdesignoflockedplatesandspecificallythoseof 1.5mmwithathicknessof2mm,alongwiththe accompany-inginstruments(preciseguidesandtweezersforperforming reduction),facilitatestheintraoperativeprocedure.

TheuseofanAcutrak®_conical_compression_screw_(which wasdesignedfortreatingfracturesofthescaphoid),described forthefirsttimeinthisstudy,showsthepossibilityof apply-ingthistofracturesoftheproximalphalanxwiththestability thatisnecessaryforgood postoperativerecovery.However, forthistobeundertaken,mechanicalproofthatthesynthesis would withstandtheloadingneeded duringthe rehabilita-tion,andwouldnotimpairrecoveryorbringanyharmtothe patient,wasrequired.Thisreasonencouragedustoconduct thepresentstudy.

Neither the percutaneous approach using the Acutrak® screwinthedorsalregionofthefinger(asaninternaltutor) northe placementofalateral plate (usingtheprinciple of axialcompression)reachedtheextensortendon,and adher-enceofthe tendontothe implantwas avoided.Therewas alsolessriskofjointstiffness,sincethehypothesiswasthat thesemethodswouldbesufficientlystabletoenable metacar-pophalangealand interphalangealjointmobilityduringthe immediatepostoperativeperiod.

Wedecidedtouseasyntheticbonemodel,ratherthanan animalphalanx(suchasfromapig),becausethedensityinthe modelwouldbeaconstant.Thisminimizedthebiasrelating tovariationsinbonedensityandconcentratedthetestingon theimplants.Westandardizedonasimpletransversefracture linesincethisisthebestlineforobtainingaxialcompression ofthefragments,giventhatweweregoingtotesttechniques thatappliedcompression.

In making horizontal comparisons of the mechanical resultsbetweenthegroups, itwasobservedthattherewas astatisticallysignificantdifferencebetweengroupsIandII. Thus,greaterforcewasneededtoreachfatigueofthe syn-thesismaterialconsistingofanintramedullaryscrew.Itwas thereforeshownthatthismaterialwasmechanicallysuperior tothemodelwiththelateralplate.

Sincethe meanmaximum forceingroupIII(Fig.3)was 167.8%greaterthanthatofgroupIand662.9%greaterthan thatofgroupII,thisshowsthatthetestmachine(Fig.1)didnot influencethefracture,butonlytheimplants.Thecomparative mechanicaltestperformedinthepresentstudywastherefore certified.

The results obtained from this study encourage us to proceedfurtherintheseinvestigations,nowinaclinical man-ner.Inadditiontothemechanicaladvantageofconicalscrews, theyareappliedpercutaneouslyandthismayavoid compli-cations relating tothe surgical access that isnecessary in osteosynthesisusingaplate.

Conclusion

StabilizationusingAcutrak®_screws,_in_treating_the_fractures inthemodelusedinthistrial,presents mechanicalresults thatarestatisticallysignificantlysuperiortothosefromthe axial compression technique using a lateral plate (Aptus Hand®_).

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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