Standardised cement augmentation of the PFNA using a perforated blade: A new technique and preliminary clinical results. A prospective multicentre trial

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Standardised

cement

augmentation

of

the

PFNA

using

a

perforated

blade:

A

new

technique

and

preliminary

clinical

results.

A

prospective

multicentre

trial

C. Kammerlander

a,

*

,

F. Gebhard

b

,

C. Meier

c

,

A. Lenich

d

,

W. Linhart

e

,

B. Clasbrummel

f

,

T. Neubauer-Gartzke

g

_,

_M.

_{Garcia-Alonso}

h

_,

_T.

_Pavelka

i

_,

_M.

_Blauth

a

DepartmentofTraumaSurgeryandSportsMedicine,MedicalUniversityofInnsbruck,Innsbruck,Austria

b

DepartmentofTraumatology,Hand-,Plastic-,andReconstructiveSurgery,CenterofSurgery,CenterofMusculoskeletalResearch,UniversityofUlm,Ulm,Germany

c

DepartmentofTraumatology,StadtspitalWaid,Zu¨rich,Switzerland

d_Department_of_{Traumatology,}_Klinikum_Rechts_der_Isar,_Technical_University_of_Munich,_Munich,_Germany e

DepartmentofOrthopedicsandTraumaSurgery,SLKKlinikenHeilbronn,Heilbronn,Germany

f

DepartmentofTraumaSurgery,ZollernalbKlinikum,Balingen,Germany

g

DepartmentofTraumaSurgery,KlinikenNordoberpfalz,Weiden,Germany

h

DepartmentofOrthopedics,HospitalUniversitarionRioHortega,Vallodolid,Spain

i

DepartmentofTraumaSurgery,MedicalUniversityofPlzen,AlejSvobody80,CZ-30460Plzen,CzechRepublic

Pertrochanteric fractures are a rising major health-care problemintheelderlyandtheiroperativestabilisationtechniques arestillunderdiscussion.Whereasthedynamichipscrewisthe standardﬁxationmethodforstableA1fractures,1thereisatrend to use intramedullary implants to ﬁx unstable A2 and A3 fractures.2–7

RecentstudiesrevealedthatthePFNAisaveryeffectiveimplant for the ﬁxation of pertrochanteric femoral fractures.7,8

Blade-related complications withthe PFNA, suchas cut-out, and cut throughwitheithermedialblademigrationintothehipjointor lateralblademigrationarereportedfrom0.6%9_over_2.6%8_up_to

3.6%.7_However,_several_other_implants_which_use_a_screw_design

for thecephalicpartoftheimplant leadtocut-out ratesupto 16%.2,10,11

Acrucialpointisthatthesecatastrophicfailuresmainlytake place in severe osteoporotic bone.12 _However, _the

above-men-tioned studies7–9 _do _not _only _include _fragility _fractures _and

thereforethecut-outrateintheelderlymaybeevenhigher.

ARTICLE INFO

Articlehistory: Accepted11July2011

Keywords: Hipfracture Augmentation PMMA Cementleakage PFNA Cut-out

Cementaugmentation Osteoporosis

Corticalthicknessindex Cementdistribution

SUMMARY

Pertrochantericfracturesarearisingmajor health-careproblemintheelderlyandtheiroperative stabilisationtechniquesarestillunderdiscussion.Furthermore,complicationslikecut-outarereported tobehighandimplantfailureoftenisassociatedwithpoorbonequality.ThePFNA1

withperforated blade offers apossibility for standardisedcement augmentation using a polymethylmethacrylate (PMMA)cementwhichisinjectedthroughtheperforatedbladetoenlargetheload-bearingsurfaceand to diminishthe stresses on the trabecular bone. The current prospective multicentrestudy was undertakentoevaluatethetechnicalperformanceandtheearlyclinicalresultsofthisnewdevice.

InnineEuropeanclinics,59patients(45female,meanage84.5years)sufferingfromanosteoporotic pertrochantericfracture(Arbeitsgemeinschaftfu¨rOsteosynthesefragen,AO-31)weretreatedwiththe augmentedPFNA1

.Primaryobjectiveswereassessmentofoperativeandpostoperativecomplications, whereasactivitiesofdailyliving,pain,mobilityandradiologicparameters,suchascementdistribution aroundthebladeandthecorticalthicknessindex,weresecondaryobjectives.

Themeanfollow-uptimewas4monthswhereweobservedcallushealinginallcases.Thesurgical complicationratewas3.4%withnocomplicationrelatedtothecementaugmentation.Morethan one-halfofthepatientsreachedtheirprefracturemobilitylevelwithinthestudyperiod.Ameanvolumeof 4.2mlofcementwasinjected.Wedidnotﬁndanycut-out,cutthrough,unexpectedblademigration, implantlooseningorimplantbreakagewithinthestudyperiod.

Ourﬁndingsleadustoconcludethatthestandardisedcementaugmentationusingtheperforated blade forpertrochanteric fractureﬁxation enhancesthe implantanchorage within thehead–neck fragmentandleadstogoodfunctionalresults.

ß2011ElsevierLtd.Allrightsreserved.

*Correspondingauthorat:DepartmentofTraumaSurgeryandSportsMedicine, MedicalUniversityofInnsbruck,Anichstrasse35,A-6020Innsbruck,Austria. Tel.:+4351250480882.

E-mailaddress:[email protected](C.Kammerlander).

ContentslistsavailableatScienceDirect

Injury

j ou rna l h ome p a ge : w ww . e l se v i e r. co m/ l oc a te / i n j ury

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Several biomechanical investigations on human cadaveric proximalfemoral fracturesshowed a higher cut-out resistance whenthe devicewasaugmented withpolymethylmethacrylate (PMMA)cement.13,14

Augmentation ofﬁxation devicesenlarges thebone–implant interfaceandleadstoahigherstabilityalsoinclinicaluse.10,15–21_A

mainproblemregardingaugmentationatthehipwasthelackofa device for controlled cement placement around the implant.22

Furthermore,thediscussionaboutcement-relateddisturbanceof thebonemetabolismisongoing.13,23,24_However,_several_studies

reportno damagetothecartilage orthebone itselfby cement augmentation.25–28_The_current_prospective_multicentre_study_was

undertakentoevaluatetheearlyclinicalresultsandthetechnical performanceofthenewstandardisedaugmentationforthePFNA blade.Toourknowledge,thisistheﬁrstreportonthisdevice.

Materialsandmethods

The study was performed at nine orthopaedic departments betweenOctober2009andJuly2010.Theinclusioncriteriawereas follows:pertrochantericfracture(Arbeitsgemeinschaftfu¨r Osteo-synthesefragen/Orthopaedic Trauma Association, AO/OTA 31A), age65yearsandabove,low-energytraumaandsignedinformed consent.Patientswithapathologicalfracture,anypatientswith active malignancy, organ transplantation or infection were excluded.Theethicalcommissionapprovedthestudyandevery singlepatientsignedtheinformedconsentform.Atotalnumberof 78patientshavebeenincluded.Nine(11.6%)caseswerelostto follow-up due to concurrent indisposition or weakness, which madeanadditionalevaluationimpossible.Tenpatientsdiedfor reasonsnotrelatedtothesurgicalprocedure.Theremaining59 patientswerefollowedupaccordingtothestudyprotocol.

Operativetechnique

The Proximal Femur Nail Antirotation (PFNA, Synthes1

, Switzerland)is available in foursizes (standard,small, XS and long)withrightandleftoptionsforthelongnail.Theperforated blade(Fig.1)hasthreeholesateverydeepeningofthehelix.A side-opening cannula (Fig. 2) allows for deliberate cement placement through the holes of the blade. Augmentation is performed with a high-viscosity PMMA cement (Traumacem, Synthes1

,Switzerland). Fracture reduction and implantation of thePFNAareperformedaspreviouslyreported7,9_and,_instead_of

thestandard blade,theperforatedbladeis used.Itisofutmost importancetonotperforatethefemoralheadwhendrillingthek -wiretodeterminethepositionofthehelicalblade.Attheendofthe usualprocedure and before augmentation, a perforation in the jointhastobeexcludedtoavoida leakage.Therefore,the side-opening cannula is inserted into the PFNA blade and some customarywater-solublecontrastmediumisappliedwithausual syringe. If there is no contrast ﬂuid leakage into the hip joint detected,theprocedureistobecontinued.Fig.3showsthetypical

distributionofthecontrastmedium(a)andacaseofleakage(b). Thecementismixedassuggestedbythemanufacturerandfilled intosyringeswithastandardisedset.Theside-openingcannula has to be primed with3ml of cement. The syringes are then attachedtotheside-openingcannulaandthecementisinjected under fluoroscopic control. During injection, the side-opening cannulacanberotatedtoplacethecementindifferentdirections. Afterfinishingtheinjection,thecannulahastoberemoved.The augmentation process lasts around 10–15min. Fig. 4 shows a representativecaseofstandardisedcementaugmentationofthe perforated PFNA blade in a 87-year-old lady withan unstable pertrochantericfracture.

Outcomeparameters

TheWHOPerformanceScore29_was_used_to_measure_the_quality

oflifebeforeandafterthefracture.Itconsistsofﬁvelevelsinwhich

Fig.1.Theperforatedblade.

Fig.2.Thesideopeningcannulawhichisusedtoinjectthecement.

Fig.3.Imageintensiﬁerpicswithtypicalcontrastmediumdistribution(a)anda caseofleakageofcontrastmediumintothehipjoint(b)whichconsequently prohibitscementaugmentation.

C.Kammerlanderetal./Injury,Int.J.CareInjuredxxx(2011)xxx–xxx 2

G Model

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0meansfullactivitywithoutrestrictionand4meanscompletely disabledandtotallyconﬁnedtobedorchair.

TheParker MobilityScore30_was_used _to_assess _the_walking

ability before the accident and at follow-up. The particular capabilitytowalkinside,walkoutsideandhavingsocialcontact isevaluatedinfourlevelswith‘‘nodifﬁculty,’’‘‘alone,’’‘‘withhelp fromanotherperson’’and‘‘not atall.’’Amaximum of9 points meansunlimitedwalkingability.Inaddition,theuseofawalking aid was documented for every patient before and after the accident.

Painwas assessedusing the visualanalogue scale (VAS),as previouslydescribed31_and_widely_known._The_VAS_was_found_to

havegoodmeasurementpropertiesassessingpaininhipfracture patients.32

OnthepreoperativeX-rays,thefracturepatternandthecortical thickness index33 were assessed. The cortical thickness index showsa signiﬁcantpositive correlationwiththeT-Scoreof the femoralneck34_and_was_therefore_used_to_classify_the_local_bone

qualityinourstudypopulation.Acorticalthicknessindexlower

than0.40 (lateralfilm)and0.50 (anterioposterior(ap)film)has beendescribedasathresholdforosteoporosiswhereallmeasured femorahadalocalbonemineraldensitylowerthan2.5standard deviationsbelowthepeakbonemass,whichistheWorldHealth Organization(WHO)definitionofosteoporosis.34

On the postoperative X-rays, we evaluated the quality of fracturereductionasanatomic(nodisplacement),near-anatomic (<3mmdisplacementor5–108varus/valgusand/oranteversion/ retroversion) or non-anatomic (>3mm displacement or >108

varus/valgusand/oranteversion/retroversion).6,9Furthermore,the position of the PFNA blade was evaluated and categorised, as previouslydescribed6,7_by_dividing_the_femoral_head_into_superior,

centralandinferiorthirdsontheapradiographandintoanterior, central and posterior thirds on the lateral radiograph (Fig. 5). Cement distribution was measured in relation to the blade. Therefore, the plain X-rays in both ap and lateral view were assessedbyusingthesoftwareOsirixTM_,_which_allows_drawing_the

bordersofthecementandcalculatingthesquarecentimetresof the marked area. The blade was subdivided in its middle in

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longitudinaldirectiontomeasurethedistributionofcementabove andbelowthebladeaswellascentrallyintheapradiograph,in which‘centrally’meansthearea‘b’inFig.6fromthetipofthe bladetowardsthepelvisinthelongitudinaldirectionoftheblade. Measurementsinthelateralradiographwereconductedventrally, dorsallyandagaincentrallytotheblade.Theareaswerecalculated inrelationtotheareaofthefemoralhead(Fig.6).Furthermore,the amountofinjectedcementwasdocumented.Onthefollow-up X-rays,signsoffracturehealingwereassessed.Themigrationofthe blade within the head–neck fragment and the lateral blade migrationweremeasuredaspreviouslydescribed.35,36

Intra-operativecomplications includedanyunforeseenevent duringtheaugmentation,suchasperforationwiththeguidewire into the hipjoint and cement leakage. Potential postoperative complicationswerecuttingoutofthebladefromthefemoralhead, cutting through the blade centrally, any unexpected blade migration, loosening of the blade, implant breakage, infection, additionalfracture or bone-healing disturbances and anyother generalcomplicationwithinthefollow-upperiod.

Statisticalanalysis

Statistical Packagefor Social Sciences (SPSS)16.0(SPSSInc., Chicago,IL,USA)wasusedforstatisticalanalysis.Allbaselineand follow-upparametersweredescribedusingstandarddescriptive statistics.Metricscaleddataarereportedasarithmeticmeanand categoricaldataasabsolutefrequencyandpercentagedistribution. Depending on the distribution form, a t-test for independent variablesoranon-parametricMann–WhitneyUtestwasused.The Kolmogorov–Smirnov test was used to assess the distribution form.Achi-squaretestoraFisher’sexacttestwasusedtoanalyse categoricaldata.Theprobabilitylevelwassetasp<0.05.

Results

Toinvestigatetheeffectofthestandardisedcement augmen-tation,59patientswereanalysed.Meantimetofollow-upwas4 months(68–355days).ThedemographicsareshowninTable1. Associatedinjurieswerenotedintwopatients.Themajorityofthe patients sustained an unstable pertrochanteric fracture (A2/3; 74.5%).Only20.3% wereindependentlymobile(ParkerScore9) before their fracture. Mean Parker scores were 4.5 before the fractureand3.8atfollow-up.Atthefollow-up,55.3%reachedthe sameorevenabetterParkerscore.MeanVASatfollow-upwas0.9. All patients were osteoporotic, whereas the mean cortical thickness index (CTI AP) was0.47. In 33.9%, thepostoperative X-rays showedan anatomicreduction. In 57.6%, reduction was near-anatomicandnon-anatomicin8.5%.Anopenreductionwas necessary inthree cases,whereas in two casessubtrochanteric cerclage wires were used to stabilise the reduction without removal.In61%,thebladecouldbeplacedinanidealposition,that is,centre–centreofthehead(Fig.4).Therewasonepatientwitha postoperativebleedingandonewitharotationaldeformity,both necessitatingare-operation.

Theonlyintra-operativecomplicationreportedwasa perfora-tionofthek-wireintothehipjoint.Itwasdetectedbyinstillingthe contrastmedium(Fig.3(b)).Consequently,nocement augmenta-tionwasperformedinthispatient.Forthepresentedstudy,cement applicationwasratedas‘‘good’’or‘‘excellent’’in84.7%.

In two cases, the augmented PFNA was used as a salvage procedureinfailurecases.Onewasafailedgammanailwith lag-screwlooseninginanA3fracture.Inthiscase,thegammanailwas removed 6 weeks after implantation and an augmented PFNA procedure was performed without complications. Follow-up examinationafter4monthsshowedfractureunionwithoutany further problems(Fig.7). The othercase wasa malreducedA3 fracture,wherethePFNAwasinsertedatawrongentrypointand poorlypositioned.Inthissecondcase,animpendingcut-outwas intended to be avoided with thestandardised augmentation 2 weeksaftertheprimarysurgicalintervention.Unfortunately,the patientdiedafter6weeksduetoapre-existingrenalinsufﬁciency. Follow-up4weeksaftertherevisionsurgeryshowednofurther dislocationapartfromalateralblademigration.

A mean of 4.2ml of cement was injected and the cement distributionaroundthebladewasalmosthomogeneous(Table2).

Fig.6.ThemethodofmeasuringthecementdistributionaroundthebladeintheAP viewwhereasameansthesuperior,bthecentralandctheinferiorfractionofthe cement.

Table1

Thebaselinecharacteristicsofthestudypopulation.

All(n=59) Percent

Age,mean 84,5

Female/male 45/14 76.3/23.7

Left/right 29/30 49.2/50.8

AO31-A1 15 25.4

AO31-A2 31 52.5

AO31-A3 13 22

Hospitalisationtime,mean 12.5days Fig.5.Thepositionofthebladewithinthefemoralhead.

G Model

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Only a severeosteoporosis is predictive for central(area ‘b’ in

Fig.6)cementﬂowtowardsthehipjoint(p<0.05).

Atfollow-up,allfracturesshowedacallusformation.Wecould notdetectanysignofosteonecrosisofthefemoralheadorlysis around the cement. According to the above-mentioned meth-od,35,36 there was no implant migration (e.g.,migration of the bladerelatedtothefemoralhead)measurableasidefromlateral blade migration. We did not ﬁnd any cut-out, cut through, unexpected blade migration, implant loosening or implant breakagewithinthestudyperiod.

Discussion

ThePFNAwasprovedtobeastableimplantforthetreatmentof proximalfemoralfractures.7–9,37_{Nevertheless,}_there_are

compli-cationssuchascuttingoutofthefemoralheadorbladeloosening reported in the literature.7–9 All these complications are cata-strophic failures for these patients due to the necessity of re-operation.Asmostofthesefracturesoccurintheelderly,these failuresareevenmoresevereduetothepatients’co-morbidities andtheirinabilitytocounterbalance,whichcomesalongwitha highperioperativemorbidityandmortality.

Thesurgicalcomplicationrateinthepresentedstudywas3.4%, withnocomplicationrelatedtothecementaugmentation.Thisis anacceptableratecomparedwithotherreportsintheliterature.8,9

Wedidnotfindanycut-outorcuttingthroughoftheblade, unexpectedblademigrationandlooseningoftheblade. Implant-related complications in proximal femoral fractures needing revision surgery, suchas a cut-out of the implant throughthe femoral head,arereportedtobeashighas16%.2,10,38,39Recent findingsdealingonlywiththePFNAreportaboutacut-outrateof 2%8_and_3.6%.7_We_did_not_find_any_cut-out_or_cutting_through_of_the

blade, unexpected blade migration and loosening of the blade. Therefore,ourﬁndingsmakeusbelievethatanadditionalcement augmentationcanavoidacut-outinthesefractures;butithasto benotedthatourseriesispossiblytoosmalltoconcludethis.

Fig.7.(a)Thegammanailfailedinthisunstablepertrochantericfracture6weeksaftersurgery.(b)APFNAwithstandardizedcementaugmentationthroughtheperforated bladewasusedasasalvageprocedure.Thefracturehealedwithoutanyproblemwithin4months.

Table2

Thecementdistributioninallpredeﬁneddirectionsinpercent.Therightpart showsthecorrelation(p-value)withthecorticalthicknessindexinbothstandard views.

CTIAP CTIAX

CementdistributionAP

Cranial 44.1 0.992 0.400

Caudal 43.1 0.096 0.061

Central 12.8 0.387 0.078

CementdistributionAX

Ventral 43.1 0.374 0.127

Dorsal 44.8 0.079 0.089

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Postoperatively, we observed one case of a fall-related additionalfemoralfractureatthetipofthenail.Inthiscase,the shortnailwaschangedtoalongnailandboththeremovalandthe new implantation of the blade was performed without any problem. Theblade–PMMA interface brokeand there werenot more force needed to remove the blade. The new blade was inserted in the same position and there was no additional augmentationdone.Unfortunately,thepatientdied4weeksafter thesecondoperationduetomyocardialinfarction.

In ourstudy,55.3%reachedtheirprefracturefunctionallevel withinthestudyperiod.Inthiscontext,wehavetonotethatthe mean age of our study population was 84.5 years and these patientshavemanyco-morbidconditions.40–43_These

co-morbid-itiesinﬂuencetherecoveryofthepatients41_and_compared_with

theliterature,7–9thisisasatisfyingoutcome.

AccordingtocorticalthicknessmeasurementsproposedbySah et al.,34 _all _our _patients _suffered _from _{osteoporosis.} _We _have

observed that the distribution of the cement was almost homogeneous.However,itwasnotpossibletoguidethecement intoapredeterminedareawiththeusedside-openingcannula.A mean amount of 4.2ml cement was used to augment the perforatedblade.Thedistributionofthecementwasinﬂuenced onlyincaseswithsevereosteoporosisinthewaythatwecould observeahigherfractioncentralofthetipofthebladetowardsthe hipjoint.Ithastobenoticedthatasubchondralpresenceofthe PMMAcouldpossiblyinﬂuencetheoverlyingcartilage.44_We_did

notﬁndanycorrelationwiththeamountofinjectedcementand pain or mobility at follow-up. Due to an exothermic reaction duringPMMA cementpolymerisation, itis suspected thatlocal bonedamagemaybeinduced.24_In_our_series,_we_did_not_ﬁnd_any

radiologicalsignsofbonenecrosis.Thissupportsthetheorythat thereisno thermal damagetothebone duetotheexothermic reactionofthePMMAinastandardisedaugmentationsettingwith onlya smallamountofcementinjected.26,28_The_mean _cement

volumeof4.2mlusedinourstudywasabletoincreasestabilityin biomechanicalinvestigations.14,20,23,26_However, _with_this _small

amountofcementdamagetotheboneisunlikely.14_In_this_context,

ithastobementionedthatourfollow-uptimecouldbetooshort forastatementaboutbonenecrosis,asseveralauthorsreportthe timetoonsetupto3yearsafterthefracture.45,46_Within_the_study

period,allfractureswerehealedandwedidnotﬁndany bone-healingdisturbance.Therefore,westatethatthenewstandardised techniqueisasafemethodcomparedwithotherpublishedcement augmentationtechniques.10,16–21,47

Themainlimitationsofthis studywerethelackofacontrol group and the inclusion of stable pertrochanteric fractures. However, thefeasibility ofthe newstandardisedaugmentation wasproved.Theindicationfortheaugmentationisnotclearyet andwesupporttheopinionthatthegoodresultswiththePFNAin previousstudiesresultfromachievingagoodfracturereduction and careful implant placement.7,8,48 _We _think _that _a _severe

osteoporosiscouldbeapossibleindicationbutthereareprobably moreconcomitantpatient-relatedfactorstobeconsidered.From thesocioeconomicperspectivealso,additional costshavetobe mentioned. An analysis of failure cases and a prospective, randomised trial comparing geriatric patients with unstable pertrochanteric fractures with a PFNA either with or without augmentation would probably give us more hints to ﬁnd the patientsatriskandtodeﬁnetheindicationsforaugmentation.

Conclusion

ThestandardisedaugmentationoftheperforatedPFNAbladeis asafeanduser-friendlytoolforpertrochantericfractureﬁxation.It prevents blade migration within the head–neck fragment and leads to good functional results. These impressions should be

proven by a randomised trial comparing the PFNA with and withoutaugmentation.

Conﬂictofinterest

Noneoftheauthorshasanyﬁnancialorpersonalrelationship withorganisationsthatcouldinﬂuencetheirworkinappropriately.

Acknowledgements

Synthesisacknowledgedfororganisationalsupport.Therewas no involvement of Synthes in study planning, data analysis, interpretationorarticlewriting.Theauthorswouldliketothank Dr.Alexander Scolaforhelpingwithdata managementand Dr. StefanieErhartforherhelpwithpreparationofthearticle.

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G Model

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