32 ORTHOPRENEUR • September/October 2010

FUTURETECH

Computer-assisted Treatment of Distal Radius Malunion

Author: Prof. Filip Stockmans, M.D., Ph.D.

Intra-articular malunions represent an exceptional technical challengeforthetreatingsurgeon.MultidetectorCTscans(MDCT)withthree-di-mensional(3D)surfacerenderedimagesareincreasinglyusednotonlyfortheevaluationofmalunions,butalsotodeveloparoadmapforsur-geryinpatientswhohavebeenselectedforcorrectiveosteotomy.1,10,12

CT-basedvirtualpre-operativeplanning,includingvirtualosteotomy,predic-tionoffinalpositioning11andadditivemanufacturingofpatient-specificinstrumentsbasedonthe3Dbonestructureareclinicalreality.8,9

Computer-assisted PlanningThe3DinformationpresentinthedatasetofaCTscancanbeused

forcomputer-assistedplanning.TheMDCTscansconsistofaseriesofsequentialsliceswithpresetthicknessandsliceintervals.Withthemulti-detectorhelicoidalCTscans,resolutionofupto0.3mmcanbeachieved,thoughat the“cost”ofahigherradiationdose.8FromtheCTdataset,3Dimagescanbereconstructedwithtwodistinctlydifferenttechniques.Themostcommonlyusedtechniqueissurfacerendering,11,13whichre-constructsthebonesofttissueinterfacepresentedasa3Dsurfacethatcanbeviewedfromallangles.Ontheotherhand,thesegmentationtech-niqueidentifiesthebonystructureineachslice(surfacexheightequaltoslicethickness)whichisrestackedinanorderlymanner,resultinginmathematically described volume,8,9 with distinct mathematical sizesand shapes that can be manipulated as a geometric structure (sliced,repositioned,measured,etc.)intonewconfigurations.Mimicssoftware(MaterialiseNV,Leuven,Belgium)wasusedforsegmentationandvir-tualplanning.

Whendealingwithadistalradiusmalunion,thefirststepistoseg-menttheradiusandmakeavirtual3Dreconstruction.(SeeExhibit1.)Next,thedifferentpartsofthemalunionareisolatedasindividualstruc-tures.(SeeExhibit2.)Treatmentofanintra-articularmalunionusuallyinvolves recreating the original fracture pattern with a series of 1mmdrillholes.(SeeExhibit3.)Incaseswherelengthneedstobereconstruct-ed, it ispreferabletousethemirror imageof thecontralateralnon-af-fectedradiusasareference.(SeeExhibit4.)Oncethevirtualreductionisperformed(SeeExhibit5.),adigitalimageoftheimplant(typicallyplateandscrews)canbeimportedintotheproject.Thisstepallowsoptimiza-tionoftheosteotomysiteandimplantchoice.

The implantcanalsobeusedasanassemblyguide for therecon-struction. In these cases, thedrillholes for thefixationof the implanthavetobepredrilledonthemalunitedradius.(SeeExhibit6.)Theloca-

Exhibit 1: Virtual 3D reconstruction of distal radius

Exhibit 2: Parts of radius malunion are isolated

Exhibit 3: Recreating the original fracture pattern of an intra-articular radius malunion

September/October 2010 • ORTHOPRENEUR 33

tionofthedrillholesonthemalunitedboneisdeterminedbyfittingtheimplanttothevirtualreconstructionandsubsequentlyreverseengineer-ingthedrillholepositionsinthemalunitedposition.

Executing the Surgery Using Patient-specific InstrumentsSince the goal of these procedures is to reconstruct the anatomy

with(sub)millimeterprecision,5it’sdifficulttorelyonclinicaljudgmentand fluoroscopy only. Various solutions have been suggested rangingfromarthrotomy,10arthroscopywithinsideoutosteotomy,3experimen-talnavigation6andpatient-specificinstrumentsproducedusingadditivemanufacturing.8,9

Thesepatient-specificSurgiCase®surgicalguides(MaterialiseNV)areproducedassurfacemoldsofthe3Dbonemodelandhaveauniquefittothebone.Additionally,theseguidesaredesignedwithK-wireholesforfixationtothebone,cylindersthatarefittedwithdrillsleeves,andslitstoperformosteotomiesalongdefinedcuttingplanesasdeterminedinthepre-surgicalplan.

Note:whenconfrontedwithcombinedintra-andextra-articularmal-unions,theprocedurerequirestheuseofmultipleconsecutiveguides.Inthesecases,theintra-articularosteotomyisperformedfirstbydrillingaseriesof1.1mmdrillholesalongtheoriginalfracturelinethatstructur-allyweakens theboneand facilitates recreating the fracturealong thepreset pattern. (See Exhibit 7.) Second, the drill holes for the implantfixationaremade.Usually,themetaphysicalosteotomyisthelaststep.

Atthispointallpartsareseparated.Drilling(perforating)thebonestructurallyweakensittotheextentthatitwillbreakalongthepresentpattern. (SeeExhibit8.)Sincethedrillholesforthefixationof the im-plantarepre-drilledinthepositionofthefullyreducedmalunion,theimplantisusedasafinalreductiontemplate.(SeeExhibit9.)

ConclusionThistechnologywasfirstusedinourdepartmentin2005,initially

forthesurgicalplanningofaMadelung’sdeformitywithouttheuseofpatient-specific instruments. Patient-specific instrumentation was thenintroducedin2007withourfirstintra-articularmalunionoftheradius.Sincethen,fivetotencasesofvaryingnatureshavebeenperformedev-eryyearutilizingtheengineeringservicesprovidedbyMaterialise.Fur-ther,thistechnologyhasbeenusedfortreatmentsofmalunionsoftheproximalradius,distalhumerus,distalfemur,proximaltibia,etc.

Asreportedpreviously,thepre-surgicalplanningaloneofcomplexosteotomies in 3D offers multiple advantages. The surgeon not onlygainsmore insight in thecomplexityof thedeformity,buthecanalsofine-tune the surgery and evaluate different, sometimes conflicting,treatmentstrategiessuggestedinliterature.4Thedifferenttrialsaredoneinavirtualsystematnoadditionalcost,incontrasttotrialsurgeryonphysicalmodelsthatasarulecanonlybeperformedonce.

FUTURETECHExhibit 4: Using Mimics to create a mirror image of the contralateral non-affected radius as a reference for reduction

Exhibit 5: Virtual reduction of segments

Exhibit 6: Determining the drill holes for plate fixation

Exhibit 7: Intra-operative use of Materialise’s SurgiCase guide

The different trials are done in a virtual system at no additional cost, in contrast to trial surgery on physical

models that as a rule can only be performed once.

34 ORTHOPRENEUR • September/October 2010

Soonafterthepossibilitiesofvirtualsurgeryplanningwerereported,surgeonstriedtobringplanningintotheoperatingtheater.Onepossibilityistouploadtheprojectintonavigationsoftware.Theproblemintheupperextremity,however,istheuseoftrackingmarkersontheupperextremityand instruments due to size limiting factors. The first attempts to bringthesurgeryintotheoperatingtheaterproducedspacingblockstoexactlymatch thevoidspaceafteropeningwedgeosteotomies.11Ofcourse, thiswasofnouseinclosingwedgeorintra-articularosteotomies.

Along came the next technological advancement for surgery plan-ningviathedevelopmentofpatient-specificinstruments,suchassurgicalguides.Thistechnologyhasbeenusedformanyyearsindental implan-tology14,15andmorerecently,wasintroducedtokneearthroplasty.7Thesepatient-specificinstrumentsserveasanintra-operativenavigationtooltoperformsurgical functionswithhighprecision; thegreencolor indicates<1mmaccuracy.(SeeFigures9.1,9.2and9.3inExhibit9.)Theaccuracyfa-cilitatesauniquefittingofthepatient-specificinstrumentontothesurfaceoftheaffectedbone.Themoreirregularitiescanbeincludedinthemoldedsurface,themorereliablethefit.

Withtheintroductionofpatient-specificinstrumentstotheorthopae-dicfield,itbecamepossibletoperformintra-andextra-articularosteoto-mieswithahighdegreeofprecision9aspre-surgicallyplannedforthein-dividualpatient.Furtherintroducingthefixationdeviceintotheplanningprocessallowsassembling thedifferent fragmentsusing thefixation im-plantasadistractiontemplate.Althoughconventionalsurgicalskillsandpre-operativefluoroscopyaresufficientinmanycases,themorecomplexcaseslikecombinedintra-andextra-articularosteotomieswithlengthre-constructionorrotationalmalunion,mostcertainlyarefacilitatedwiththeuseofthefixationdeviceasanassemblytemplate.

REFERENCES

1. AthwalGS,EllisRE,SmallCFandPichoraDR.“Computer-assisteddistalradiusoste-otomy,” J Hand Surg Am28(6):951-8,2003.

2. BindraRR,ColeRJ,YamaguchiK,EvanoffBA,PilgramTK,GilulaLAandGelbermanRH.“Quantification of the radial torsion angle with computerized tomography in cadaverspecimens,” J Bone Joint Surg Am79(6):833-7,1997.

3. delPinalF,Garcia-Bernal,FJ,DelgadoJ,SanmartinM,RegaladoJandCerezalL.“Cor-rectionofmalunitedintra-articulardistalradiusfractureswithaninside-outosteotomytechnique,”J Hand Surg Am31(6):1029-34,2006.

4. JupiterJB,RuderJandRothDA.“Computer-generatedbonemodelsintheplanningofosteotomyofmultidirectionaldistalradiusmalunions,” J Hand Surg Am17(3):406-15,1992.

5. KnirkJLandJupiterJB.“Intra-articularfracturesofthedistalendoftheradiusinyoungadults,”J Bone Joint Surg Am68(5):647-59,1986.

6. LiverneauxP.“[Scaphoidpercutaneousosteosynthesisbyscrewusingcomputerassistedsurgery:anexperimentalstudy,]”Chir Main24(3-4):169-73,2005.

FUTURETECHExhibit 8: Recreating the original fracture after the bone has been weakened

Exhibit 9: Plate fixation

Figure 9.1:

Figure 9.2:

Figure 9.3:

With the introduction of patient-specific instruments to the orthopaedic field, it became possible to perform intra- and extra-articular osteotomies with a high degree of precision9

as pre-surgically planned for the individual patient.

September/October 2010 • ORTHOPRENEUR 35

7. Lombardi AV Jr, Berend KR and Adams JB. “Patient-specific ap-proachintotalkneearthroplasty,”Orthopedics31(9):927-30,2008.

8. MuraseT,OkaK,MoritomoH,GotoA,YoshikawaHandSugamotoK.“Three-dimensionalcorrectiveosteotomyofmalunitedfracturesoftheupperextremitywithuseofacomputersimulationsystem,”J Bone Joint Surg Am90(11):2375-89,2008.

9. OkaK,MoritomoH,GotoA,SugamotoK,YoshikawaHandMu-raseT.“Correctiveosteotomyformalunitedintra-articularfractureof thedistal radiususingacustom-madesurgicalguidebasedonthree-dimensional computer simulation: case report,” J Hand Surg Am 33(6):835-40,2008.

10. PrommersbergerKJ,RingD,delPinoJG,CapomassiM,SlullitelMandJupiterJB.“Correctiveosteotomyfor intra-articularmalunionofthedistalpartoftheradius.Surgicaltechnique,”J Bone Joint Surg Am88Suppl1Pt2:202-11,2006.

11. RiegerM,GablM,GruberH,JaschkeWRandMallouhiA.“CTvir-tualreality inthepreoperativeworkupofmaluniteddistalradiusfractures:preliminaryresults,”Eur Radiol 15(4):792-7,2005.

12. Ring D, Prommersberger KJ, Gonzalez del Pino J, Capomassi M,Slullitel M and Jupiter JB. “Corrective osteotomy for intra-articu-larmalunionofthedistalpartoftheradius,”J Bone Joint Surg Am87(7):1503-9,2005.

13. Vannie,MW,TottyWG,StevensWG,WeeksPM,DyeDM,Daum WJ,GilulaLA,MurphyWAandKnappRH.“Musculoskeletalap-

plications of three-dimensional surface reconstructions,” Orthop Clin North Am16(3):543-55,1985.

14. Verstreken K, Van Cleynenbreugel J, Martens K, Marchal G, vanSteenbergheDandSuetensP.“Animage-guidedplanningsystemfor endosseous oral implants,” IEEE Trans Med Imaging 17(5):842-52,1998.

15. VrielinckL,PolitisC,SchepersS,PauwelsMandNaertI.“Image-based planning and clinical validation of zygoma and pterygoidimplantplacementinpatientswithsevereboneatrophyusingcus-tomizeddrillguides.“Preliminaryresultsfromaprospectiveclini-calfollow-upstudy,”Int J Oral Maxillofac Surg 32(1):7-14,2003.

Professor Filip Stockmans, M.D. is a professor at Katholieke Universiteit, Campus Kortrijk Belgium. Trained in Hand & Microsurgery at the Kleinert Institute in Louisville, Kentucky and University of Umea in Sweden, Dr. Stockmans has been in private practice for over 20 years. For clinical follow up, please contact Dr. Stockmans at filip.stockmans@kuleuven-kortrijk.be. For technology follow up, please contact Bill McIlhargey at william.mcilhargey@materialise.com.

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